Influence of single and tandem-submerged Arc Welding on ASTM A572 Gr.50 steels

Influence of single and tandem-submerged Arc Welding on ASTM A572 Gr.50 steels | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Influence of single and tandem-submerged Arc Welding on ASTM A572 Gr.50 steels Adapa Mahanth Kumar, Polamuri Sudheer Kumar, Perka Ashok Kumar, and 3 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4398172/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 01 Oct, 2024 Read the published version in The International Journal of Advanced Manufacturing Technology → Version 1 posted 5 You are reading this latest preprint version Abstract Square butt joints were prepared using two different materials, Niobium (Type 1) and Vanadium (Type 2) micro-alloyed ASTM A 572 Gr.50 steels, employing both single wire submerged arc welding (SAW) and two-wire tandem submerged arc welding (SAW-T) processes, with a constant heat input per unit length of 2.5 kJ/mm maintained throughout the study. The weld profile, microstructure, and mechanical properties were analyzed for SAW and SAW-T processes. It was observed that the weld width, hardness, yield strength, ultimate tensile strength, and impact toughness of the welds increased with SAW-T compared to SAW. Furthermore, a comparison was made between the two types of steel weld joints. Type 1 steel weld exhibited higher acicular ferrite, yield strength, and ultimate tensile strength due to the intra-granular nucleation of Niobium carbonitrides in austenite. In contrast, Type 2 steels displayed a higher percentage of elongation, hardness, and impact toughness at 25°C. At -20°C temperature, SAW-T welds show higher HAZ toughness than SAW welds. Also, Type 2 welds showed enhanced toughness in comparison to Type 1 welds by mitigating the pinning effect of precipitates. Tandem submerged arc welding ASTM A572 Gr.50 steel Alternating current Balance Offset Flux Copper backing Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 Figure 12 Figure 13 Figure 14 Figure 15 Figure 16 Figure 17 1. Introduction The general trend in structural steels has been to attain good toughness and weldability while decreasing the carbon content and increasing the mechanical properties through microalloying addition. Accordingly, several microalloying grades were developed with the addition of Niobium, Vanadium, and Titanium, etc. ASTM A572 Gr.50 is a structural steel that finds extensive applications in fabrication due to its commendable strength and toughness, with the inclusion of micro alloying elements such as Niobium or Vanadium aimed at enhancing its mechanical properties. Depending on the type of alloying elements, these steels are categorized as Type 1 steels (Nb added) and Type 2 steels (V added). The primary purpose of adding Niobium to steel is to regulate the size of the austenite grains. Niobium precipitates as Niobium carbide and Niobium carbonitride and governs the grain size via the pinning effect [ 1 ]. Vanadium is another micro alloying element added to steel to refine the grains. Vanadium, when combined with nitrogen, creates stable Vanadium nitride, thereby enhancing the steel's strength through precipitation hardening [ 2 ]. Between Niobium and Vanadium, Niobium exhibits greater potential than Vanadium in precipitation hardening due to the binding energy of Niobium to austenite grain boundaries compared to Vanadium. Bhattacharya et al. [ 3 ] studied the effect of different states of Niobium on the evolution of Heat affected zone (HAZ) microstructure in SAW X80 pipe welds. The reduction in transformation temperature for a constant prior austenite grain size is strongly correlated to the presence of dissolved Niobium, as the prior austenite grains serve as sites for heterogeneous nucleation in the HAZ. SAW is preferred for welding the medium to high thickness plates used in pressure vessels, offshore structures, and marine and pipeline industries because of its higher deposition rate and good surface quality [ 4 ]. Conventional SAW machines generally work on direct current electrode positive (DCEP) or negative polarity (DCEN) [ 5 ]. The DCEN yields high weld deposition and less penetration, as compared to the DCEP. In general, the weld bead geometry is influenced by various parameters such as polarity, welding current, welding voltage, wire feed speed, electrode extension, and welding speed. Yang et al. [ 6 ] asserted that the utilization of DCEP instead of DCEN, along with a larger electrode diameter of 3.2 mm, a reduced electrode extension of 25.4 mm, and an increased welding voltage promotes the attainment of a larger weld width and higher penetration in SAW. Furthermore, it was observed that, when employing basic fluxes under constant current power source conditions, a greater weld width is achieved compared to constant voltage power source conditions. Ali et al. [ 7 ] studied the effect of arc voltage and current intensity on weld penetration depth in submerged arc welding, revealing that increasing both arc voltage and current intensity enhances penetration depth. An alternating current (AC) is an appropriate option to obtain the advantages of both polarities [ 8 ]. In AC, the electrode is in positive polarity for a portion of a cycle and negative polarity for the remainder. In AC square waveform, parameters like balance, offset, and frequency can change the bead geometry apart from conventional parameters. Balance is the percentage of positive polarity time in one complete AC cycle, the offset is the percentage variation (increase or decrease) in positive polarity peak current magnitude, and the frequency denotes the number of AC cycles occurring within one second. Figure 1 depicts the schematic diagram of waveforms with different offset and balance parameters. The waveform modulation in SAW can be adjusted using power electronics to optimize parameters and achieve an optimal weld. Full-wave control technology evolved in SAW to alter the waveform variables in AC power sources [ 9 ]. It is an excellent choice to manipulate the waveforms in SAW to achieve welding productivity and quality. Pepin et al. [ 10 ] conducted a set of bead-on-plate (BOP) weld experiments using a single wire SAW process, systematically varying the balance and offset parameters, and analyzed their impact on weld geometry. The findings indicated that increasing the balance and decreasing the offset leads to maximum base metal penetration. Opting for two wires instead of a single wire is a preferred option to enhance the productivity of SAW. The two-wire tandem submerged arc welding (SAW-T) process employs two independent electrode wires, fed through separate wire feeders and controlled by distinct power sources. In SAW-T, the lead wire electrode is linked to a direct current power source, while the trail wire electrode is attached to an alternating current power source to mitigate arc blow [ 11 , 12 ]. The utilization of large-diameter wire electrodes and increased wire feed speeds (WFS) contributes to high deposition rates, resulting in enhanced productivity. Kiran et al. [ 13 , 14 ] studied the influence of lead wire electrode current, trail wire electrode current pulses, and welding speed on weld dimensions in a single pass bead-on-groove (BOG) SAW-T of high strength low alloy (HSLA) steel. The depth of weld penetration is mainly affected by the lead wire electrode current, whereas weld width is notably responsive to the trail wire electrode current. Mohsen et al. [ 15 ] developed tandem submerged arc welding with an additional cold wire (CWTSAW) to enhance productivity [ 16 ] by increasing the deposition rate and travel speed. Bead-on-groove welds with a 90° V-shaped bevel angle were prepared using both SAW-T and CWTSAW. The study compared these processes, highlighting the effects of the cold wire addition on the dilution area, microhardness, and microstructure of the weldment. The addition of the cold wire reduces the overall heat introduced to the weldment, decreasing dilution and the coarse grain heat-affected zone (CGHAZ) area, while faster cooling rates result in lower microhardness values in the CGHAZ. Tailin Ren et al. [ 17 ] investigated the critical role of optimizing process variables in CWTSAW to enhance productivity, control weld quality, and improve mechanical properties in heavy gauge pipe welding applications. The cold wire feed speed significantly influences micro-hardness profiles by modifying local thermal cycles [ 18 ]. By adjusting the cold wire feed speed, the amount of heat absorbed from the molten pool can be controlled. This alteration in heat input affects the cooling rate of the weld metal and the heat-affected zone, leading to changes in the microstructure and hardness distribution. Comprehensive studies have already been conducted on the impact of welding parameters on the weld geometry and mechanical properties of BOP and BOG welds. The aforementioned studies were employed to choose the polarities for SAW and SAW-T welds in the present study. As per ISO 9692-2:1998(E), for SAW of steels with a thickness ranging from 3 to 12 mm, it is recommended to prepare a square butt weld with a root gap not exceeding 0.5 times the thickness of the plate or a gap of 5 mm, along with utilizing a backing bar with a minimum thickness of 5 mm [ 19 ]. The process of joining medium to thick steel plates with a square butt configuration involves welding from the top, then flipping over the welded plates, gouging the root, and subsequently completing the final bottom welding. Performing these many operations is a tedious and costly process. To address these challenges, the utilization of flux-filled aluminum/copper backing or ceramic backing is employed in the SAW. Ceramic backing is non-reusable, and flux-filled aluminum backing can melt if the dimensions of the backing groove are improper. In contrast, flux-filled copper backing has certain advantages, such as its high thermal conductivity, facilitating efficient heat transfer to the surroundings. Additionally, the life of the copper backing is longer because of its immiscible property. Mandal et al. [ 20 ] investigated the combined influence of process parameters like voltage, current, speed, and thickness on weld penetration in 8 mm C-Mn steel plates. The study employed a V groove with a 50° included angle, single side single pass SAW, and a flux-filled aluminum backing. The study identified that optimal conditions for achieving through-thickness fusion in 8 mm plates involved a 3 mm root opening and zero root face, with a required heat input of 1.2 kJ/mm. Furthermore, the use of fine-grained flux in the aluminum backing resulted in improved bottom reinforcement. Utilizing flux-filled aluminum backing without fine-grained flux results in inadequate bottom reinforcement. According to ISO 9692-2:1998(E), a V-groove joint is not advisable for joining 8 mm thick plates. Instead, a square butt joint should be performed. Sridhar et al. [ 21 ] investigated the impact of welding parameters on bead geometry and tensile properties in an 8 mm thick square butt joint with a root gap of 2.5 mm using double-sided SAW on SS 304 stainless steel plates. The study shows that the higher welding current results in increased penetration and bead overlap, while increased voltage leads to wider beads. A higher welding speed results in reduced weld width and penetration. In addition to that, double-sided weld joints demonstrated improved elongation compared to the base material. However, employing double-sided weld joints extends production time and consumes excess filler material. Therefore, economically, preparing the 8 mm thick steel plate joint with a single side single pass is preferable. Biswas et al. [ 22 ] explored the impact of heat input, root gap, and welding speed on the quality of joints formed on plates with thicknesses of 3 mm, 5 mm, and 12 mm. The study utilized a single side single pass SAW with a square butt joint and a flux-filled aluminum backing. It is observed that slower welding speeds were necessary for joining thicker plates. Furthermore, it is noted that achieving full penetration in a single pass for 12 mm plates required a specific heat input of 3.5 kJ/mm. To enhance process productivity, higher welding speeds are necessary. However, achieving this requirement is hindered by the slower welding speeds associated with preparing a joint using single-pass SAW. In another study, Biswas et al. [ 23 ] achieved through-thickness fusion in 8 mm C-Mn steel plates using a square butt configuration with a 2.6 mm root gap and a flux-filled aluminum backing. The optimal parameters identified for achieving full penetration were 570 A welding current, 29 V voltage, and a welding speed of 6.25 mm/s, which constitute the primary data for our study. Sailender et al. [ 24 ] identified critical parameters and projected optimal input parameters that affect dilution and heat affected zone in 8 mm thick V-butt joints of SAW-welded ASTM A516 Gr. 70 low carbon steel with a copper backing plate in their work. The study shows that the welding speed is the predominant factor influencing the width of HAZ. Researchers in the past prepared a square butt joint of 8 mm thick plates using the SAW process at lower speeds. However, joining of the 8 mm thick plates using a square butt joint configuration with the SAW-T process is not practiced. Additionally, there is a lack of available literature on the suitable process parameters for preparing square butt joints in 8 mm thick plates using SAW-T. Furthermore, the literature does not clearly address the effect of using two wires in the SAW-T process on the mechanical properties of joints, including strength, toughness and hardness, when prepared with a single side single pass compared to traditional SAW. To improve productivity without compromising weld mechanical properties, adopting SAW-T is necessary. The thermal cycles experienced during welding can compromise the balance of high strength and good toughness in Nb-V steels, leading to poor toughness in the HAZ during the SAW and SAW-T process. The SAW-T process is not yet employed for the joining of 8 mm thick steel plates. Additionally, the effect of SAW and SAW-T process parameters on the microstructural changes in ASTM A572 Gr. 50 Type 1 and Type 2 steels, which subsequently influence the mechanical properties of the steel joints, is not available in the literature. Furthermore, detailed studies on understanding the effect of tandem wire electrodes over a single electrode have not yet reported. The choice of steel type also exerted a notable impact on the weld properties. The present work involves a thorough experimental investigation by employing two electrodes versus a single electrode on the weld profile, weld, and HAZ microstructure during 8 mm single-side single-pass welding of ASTM A572 Gr. 50 Type 1 and Type 2 steels. Comprehensive mechanical characterization was conducted, encompassing the tensile strength, impact toughness of weld samples, and microhardness of the weldment. 2. Experimental investigation The elemental composition of the ASTM A572 Gr. 50 steel base plates of Type 1 and Type 2, and the electrode wire are presented in Table 1 . The carbon equivalent (CE) of Type 1 and Type 2 materials are 0.361 and 0.366, estimated using Eq. 1 [ 25 ]. As the workpiece materials used in this study have a carbon content of ≅ 0.14 and low CE (≅ 0.366), this class of steels has lower hardenability and good weldability. EH 14 – F7A4 flux combination is used for this work, and its corresponding elemental composition is given in Table 2 . The ASTM A572 Gr. 50 steel plates of 450 X 150 X 8 mm are used to perform the square butt weld joint experiments. The workpiece faying surfaces are grounded to remove rust, and the surface is thoroughly cleaned with acetone to remove the contamination. A consistent root gap of 2.8 mm was maintained between the steel plates with proper clamping. $$\text{C}\text{E}=\text{%}\text{C}+\frac{(\text{%}\text{S}\text{i}+\text{%}\text{M}\text{n})}{6}+\frac{(\text{%}\text{C}\text{u}+\text{%}\text{N}\text{i})}{15}+\frac{(\text{%}\text{V}+\text{%}\text{M}\text{o}+\text{%}\text{C}\text{r})}{5} \left(1\right)$$ Table 1 The elemental composition (wt %) of the base plate and electrode Grade C Mn S P Si Al N Ni Cr Cu V Nb Ti Type1 0.14 1.152 0.005 0.02 0.012 0.053 0.0036 0.024 0.026 0.008 0.001 0.023 0.023 Type2 0.136 1.185 0.004 0.02 0.099 0.039 0.006 0.025 0.032 0.008 0.036 0.001 0.002 Electrode 0.1–0.2 1.7–2.2 0.03 0.03 0.10 - - - - 0.35 - - - Table 2 The elemental composition (wt %) of the flux Element SiO 2 MnO MgO CaF 2 Na 2 O Al 2 O 3 P S Flux 22.7 4.1 25 19.6 2.1 20.5 0.029 0.015 Figure 2 (a) depicts the schematic representation of the experimental setup utilized in this study. The setup includes the Lincoln AC/DC 1000 SAW-T unit which can independently control the leading and trailing arcs with two power sources. A copper backing plate with a circular groove filled with flux is used to support the molten weld pool and ensure complete bottom-edge fusion. A constant voltage power source is used for both leading and trailing arcs. The welding head moves on the gantry system where the welding torch is mounted, while the working table is stationary. The optimum groove dimensions are chosen for the copper backing bar to achieve proper bottom reinforcement of the weld bead which directly affects the top reinforcement. This setup allows for real-time monitoring of current-voltage from the lead and trail wire electrodes. In Fig. 2 (b), an enlarged view depicts two electrodes arranged in tandem configuration, where the lead electrode is perpendicular to the welding direction, and the trail electrode forms a 18 0 angle with the axis of the lead electrode. Multiple trial runs were conducted to find the most suitable parameters to obtain a sound weld with ease of slag removal and to get a sound weld joint, as shown in Fig. 3 . From the available literature, appropriate process parameters such as welding current, voltage, and travel speed are chosen for conducting the SAW & SAW-T Butt joint welds. Preliminary bead on plate welds are performed with SAW and SAW-T processes on low carbon steel plates. Considering the weld dimensions from the bead-on plate trial experiments, the SAW and SAW-T butt joint weld parameters are determined. For SAW, the DCEP polarity is used, and for SAW-T butt joint welds for lead wire electrode, DCEP polarity and trail wire electrode AC square wave with 50% balance and 0% offset are used. Table 3 depicts the welding parameters employed in the current investigation. The experiments on ASTM A572 Gr. 50 steel are performed with the parameters presented in Table 4 . Table 3 Welding parameters used for butt joint welds S. No. Weld process parameter SAW SAW-T Lead wire Trail wire 1 Electrode diameter (mm) 3.2 3.2 4 2 Electrode extension (mm) 25 25 30 3 Polarity CV DCEP CV DCEP CV AC Sq. wave 4 Electrode angle ( 0 ) 90 90 18 to the electrode axis 5 Inter-electrode distance (mm) NA 20 6 Root gap (mm) 2.8 2.8 7 Heat input (kJ/mm) 2.5 2.5 Heat Input is computed for all experiments utilizing the recorded current and voltage waveforms. The average power consumption and heat input are calculated using Eqs. 2 and 3 [ 26 ]. A process efficiency (η) of 0.95 is used for heat input calculations [ 27 ]. A constant heat input of 2.5 kJ/mm is employed for SAW and SAW-T welds. $$\text{P}\text{o}\text{w}\text{e}\text{r}, \text{P}=\frac{\sum _{\text{i}=1}^{\text{n}}{I}_{\text{i}}{V}_{i} t}{\sum _{\text{i}=1}^{\text{n}}t} \left(2\right)$$ Where, I i and V i are instantaneous currents and voltage, respectively, and \(t\) is the difference in cycle time. $$\text{H}\text{e}\text{a}\text{t} \text{I}\text{n}\text{p}\text{u}\text{t}= \frac{{\eta }P}{\text{W}\text{e}\text{l}\text{d}\text{i}\text{n}\text{g} \text{s}\text{p}\text{e}\text{e}\text{d} } \left(3\right)$$ Table 4 Process parameters for SAW and SAW-T processes Exp. No. ASTM A572 Gr.50 steel Welding Process WFS (mm/s) Welding current (A) Welding voltage V) Bal (%) Off (%) Welding speed (mm/s) L T L T L T L T L T 1 Type 1 SAW 26.2 - 510 - 30 - - - 6 2 SAW-T 30.9 14.8 560 390 29 29 - 50 - 0 10 3 Type 2 SAW 26.2 - 510 - 30 - - - 6 4 SAW-T 30.9 14.8 560 390 29 29 - 50 - 0 10 L – Lead electrode and T – Trail electrode Figure 4 provides an overview of the locations where the tensile, Charpy, metallography, micro hardness, and microstructure specimens are extracted. The sectioned weld samples are mirror polished using an automatic disc polisher with successive grit papers from 80 to 2000 size and then cloth polished with a diamond suspension of particle size 1 µm and then etched using 2% nital solution comprising 98% ethanol and 2% nitric acid by agitate for 14 s. [ 28 ]. The macrographs are acquired from a PC-coordinated stereo microscope. The measurements of the fusion zone include weld width, penetration, and reinforcement. Base metal and HAZ micro images are captured using a metallurgical microscope. The weld metal micro images are captured from SEM. The volume fractions of acicular ferrite phases are measured in the weld zone. The mechanical characterization involves the tensile strength of the weld, impact toughness of the joint at 25 0 C and − 20 0 C temperatures, and hardness contours of the weld samples. Transverse tensile weld specimens are extracted from the weld joint. The dimensions of the tensile test specimen used in the present work follow the ASTM E8M standard [ 29 ]. Figure 5 (a-c) shows the schematic representation of the impact toughness specimens extracted from welds with the notch positioned at the weld center, + 2 mm from the fusion line (FL), and + 5 mm from the fusion line. Figure 6 shows the schematic of locations for hardness measurement for obtaining the hardness contours for the weldment. The distance between the two consecutive locations is 0.5 mm. Vickers diamond hardness tester is used with a load of 300 g force for 13 seconds. 3. Results and discussion Figure 7 illustrates the instantaneous welding current and voltage readings for both DCEP and AC square waveforms recorded while performing Type 1 SAW and SAW-T welds. Similar trends are observed in Type 2 butt joints also. Under constant voltage (CV) mode, input data includes the wire feed speed and voltage, and the recorded welding voltage and current are obtained through the Data Acquisition (DAQ) system. The welding current and voltage recorded for SAW are 515 ± 3 Amps and 30 ± 0.1 volts, respectively. In the case of SAW-T, the recorded current of the lead wire electrode is 543.5 ± 2.5 Amps, the trail wire electrode is 389.5 ± 1.5 Amps, and the voltage is 29 ± 0.1 volts. These readings suggest negligible variation in welding current and voltage with the provided input data. From Fig. 7 (c), it is evident that the trail electrode operates with AC 50% balance and 0% Offset. Figure 8 (a)-(d) illustrates the weld macrograph of Type 1 and Type 2 steel for SAW and SAW-T welds. Weld macro images show proper top and bottom reinforcement along the side wall fusion, achieved with parameters detailed in Table 4 . A noticeable disparity in weld dimensions is observed between Type 1 and Type 2 welds. An increase in SAW-T weld width and top reinforcements compared with SAW is evident in Fig. 8 (b, d). It is well understood from the literature that in the case of the tandem wire welding process, the trail wire welding arc is concentrated on the top of the lead wire molten pool rather than the previously deposited/base metal layer [ 28 ]. Consequently, the flow of molten metal in this region leads to enhanced weld width. Furthermore, as the number of passes needed to complete the weld joint in both SAW and SAW-T is one in the present study, it is required to maintain lower travel speeds in the case of SAW compared to SAW-T process. Lower travel speed results in the overhead flow of the molten metal which hinders the welding arc to strike the lower region of the weld as shown schematically in Fig. 9 , resulting in the narrow weld fusion in the middle of the weld joint [ 28 ]. However, the groove in the copper backing plate enhances the molten pool’s flow in the lower end of the narrow gap enabling the side wall fusion. Irrespective of the material (Type 1 or Type 2), a higher weld reinforcement width is observed in SAW-T welds than in SAW. As the welding speed is higher in the case of the SAW-T process, the lead wire arc strikes the base/initial/copper plate, rather than the overhead flow of the molten pool. Additionally, the trail wire arc strikes the molten pool created by the lead wire, resulting in high-intensity arc concentration in this region, which leads to higher weld reinforcement widths in this area [ 28 ]. Figures 10 , 11 , and 12 depict the microstructures of the base metal (BM), weld metal (WM), and HAZ of Type 1 and Type 2 steel welds. In Fig. 10 (a), the base metal microstructure of Type 1 steels reveals a combination of ferrite and pearlite. In the figure, the white and black structures represent ferrite and pearlite structures respectively. Pearlite has a polygonal shape, and a considerable part of the ferrite matrices were connected. The distribution of pearlite and ferrite appears to be uniform, and there were some ferrites with sizes of less than 3 µm. The average grain size of Type 1 steel is measured as 4–5 µm, and this refined grain size results in the pinning effect of Niobium precipitates [ 1 ]. The presence of stable Titanium nitride further contributes to restricting grain growth in Type 1 steels [ 30 ]. As outlined in Table 1 , Type 2 steels have high Vanadium and Nitrogen content, and Vanadium nitride, identified as more stable than vanadium carbide, plays a role in inhibiting recrystallization by exerting pinning forces [ 31 ]. Figure 10 (b) shows the base metal microstructure of Type 2 steel. The average grain size of Type 2 BM is measured as 7–8 µm. Despite this, Niobium is recognized as a more effective grain refiner than Vanadium, precipitating more readily in austenite and offering greater potential for precipitation hardening [ 32 ]. Figures 11 (a) and (b) illustrate the weld microstructure of Type 1 steels for the SAW and SAW-T process. Acicular ferrite ( \({}_{\text{A}})\) and grain boundary ferrite \({(}_{\text{G}\text{b}})\) are observed in the weld microstructure. The carbonitrides of Niobium, precipitated at austenite grain boundaries, act as sites for heterogeneous nucleation, facilitating the nucleation of grain boundary ferrite [ 33 ]. Figures 11 (c) and (d) show the weld microstructures of Type 2 steels for the SAW and SAW-T process. In both type 1 and type 2 steels, \({}_{\text{G}\text{b}}\) was more developed when the SAW-T process was used than in the SAW process. Also, it was observed that the intragranular microstructure, acicular ferrite was coarser in SAW-T. This could be due to the rapid cooling rate influenced by the high travel speed during the SAW-T process in comparison to the SAW process. Figures 12 (a) and (b) illustrate the Coarse grained heat affected zone (CG HAZ) microstructures of Type 1 steel for SAW and SAW-T welds, captured adjacent to the fusion line. Micrographic analysis revealed that the primary microstructural constituents in the case of SAW samples were polygonal ferrite and pearlite due to the slower cooling rates. In the case of SAW-T samples, the microstructure comprised lath-type/bainitic ferrite and degenerated pearlite, alongside conventional ferrite-pearlite. Notably, a bainite/martensite microstructure is evident in the form of needle-like structures, despite not being explicitly mentioned in the initial observation. The influence of Niobium precipitates on austenite/ferrite transformation is evident, as Niobium solute increases the stability of supercooled austenite and reduces the transformation temperature [ 34 ]. The presence of Niobium solute suppresses the transformation of grain boundary ferrite while promoting the transformation towards bainite or martensite. Additionally, in SAW-T welds, larger grain boundary ferrites are noted in comparison to SAW welds. This can be attributed to the higher deposition rates, resulting in slower cooling rates [ 35 ]. Figures 12 (c) and (d) exhibit CG HAZ microstructures of Type 2 steel in SAW and SAW-T welds. In the CG HAZ of Type 2 SAW steel welds, a bainitic microstructure is evident alongside lamellar ferrite. In the case of SAW-T welds, a similar microstructure is observed, but with an increase in grain boundary ferrite size and a concurrent reduction in the presence of lamellar ferrite. Hardness contours were plotted for Type 1 and Type 2 steel welds for the SAW and SAW-T weld conditions, as depicted in Fig. 13 (a) – (d). The average microhardness values for the weld metal are 209 ± 5 HV (Type 1 SAW), 221 ± 6 HV (Type 1 SAW-T), 206 ± 5 HV (Type 2 SAW), and 205 ± 9 HV (Type 2 SAW-T). Irrespective of the welding conditions and the type of material used, the weld region has a higher hardness compared with the HAZ region due to the influence of the alloying elements within the weld metal and the formation of the acicular ferrite. Although there is not much variation in weld hardness, a slight drop in hardness values was observed in the case of SAW welds compared to the SAW-T welds. This might be attributed to the supplementary heat source from the trail wire electrode and slower cooling rates, which contribute to balancing the hardness of the HAZ [ 35 ]. In the CG HAZ, the average microhardness values are 191 ± 11 HV (Type 1 SAW), 200 ± 8 HV (Type 1 SAW-T), 192 ± 11 HV (Type 2 SAW), and 177 ± 5 HV (Type 2 SAW-T). Average microhardness of HAZ are 180 ± 14 HV (Type 1 SAW), 186 ± 14 HV (Type 1 SAW-T), 186 ± 11 HV (Type 2 SAW), and 178 ± 8 HV (Type 2 SAW-T). Type 1 SAW-T samples demonstrate higher hardness in the HAZ than Type 2 SAW-T samples. It clearly shows that Type 2 samples HAZ is slightly softer than the Type 1 samples HAZ. The decrease in hardness may be attributed to the fact that, despite the dispersion of Niobium carbide and Titanium carbide being relatively finer than that of Vanadium carbide when the same amount of alloy is added, a greater driving force for precipitation was required to achieve the same number density of Niobium carbide and Titanium carbide as that of Vanadium carbide. Additionally, the top and bottom sides of the weld exhibit higher hardness due to faster cooling resulting from convection with the atmosphere on top and the presence of a copper backing plate at the bottom of the weld. Figure 14 illustrates the influence of welding conditions on the tensile properties of Type 1 and Type 2 steel weld joints. Regardless of the SAW or SAW-T process, Type 1 steel welds exhibit higher ultimate tensile strength, measuring 535.5 ± 8.5 MPa for SAW and 546 ± 6 MPa for SAW-T process than that of Type 2 steel welds, which measure 513 ± 14 MPa for SAW and 515 ± 17 MPa for SAW-T. Similarly, Type 1 steel welds demonstrate higher yield strength (σ y ) at 419 ± 8 MPa for SAW and 434.5 ± 5.5 MPa for SAW-T, in contrast to Type 2 steel welds, which exhibit 390 ± 10 MPa for SAW and 394.5 ± 12.5 MPa for SAW-T. Type 2 steel welds exhibit a percent elongation of 22.5 ± 1.5 for SAW and 19 ± 3 for SAW-T, while Type 1 steel welds show 20 ± 1 for SAW and 15.5 ± 0.5 for SAW-T. In Type 1 steel welds, Niobium carbonitrides are stable at lower temperatures in austenite but dissolved at higher temperatures [ 36 ]. Niobium carbonitrides can readily precipitate in austenite under deformation (strain-induced precipitation), and these particles impede grain growth and even recrystallization of austenite. The deformed austenite structure transforms into acicular ferrite due to intra granular nucleation of precipitates. This increase in acicular ferrite fraction leads to higher tensile strength in the case of Type 1 than in Type 2 steels. Also, Niobium efficiently locks dislocations, reducing their mobility and increasing the tensile strength of the welds. Type 1 steel welds experience failure near the HAZ, whereas Type 2 steel welds fail in the base metal. In Type 1 steels, a minimal addition of 0.023% Niobium effectively inhibits ferrite nucleation at prior austenite grain boundaries, thereby enhancing the volume fraction of martensite or bainite. Dissolved Niobium reduces ferrite nucleation and growth rates during cooling, leading to the formation of bainite/martensite microstructure and failure near the HAZ. Conversely, Type 2 steels, micro-alloyed with vanadium, exhibit vanadium atoms associated with carbon and nitrogen atoms, segregating to austenite grain boundaries at low austenite temperatures. This inhibits grain boundary nucleation of non-martensite transformation products, increasing strength, and causing the weld to fail away from the HAZ. Figure 15 depicts the effect of welding conditions on the Charpy impact toughness properties at temperatures of 25°C and − 20°C for Type 1 and Type 2 steel weld joints. In Fig. 15 (a), it is evident that Type 2 steel welds exhibit greater toughness than Type 1 steel welds. Specifically, Type 2 steel welds demonstrate toughness values of 103 ± 15 J with SAW and 99 ± 9 J with SAW-T processes at a temperature of 25°C, which are higher than that of Type 1 steel welds at 79 ± 13 J with SAW and 93 ± 4 J with SAW-T. The higher percent elongation values in Type 2 steel welds correlate with the greater toughness observed in these welds. The main reason for the deterioration in impact toughness in the case of Type 1 steel welds is heterogeneous precipitation, with coarse ferrite grains contributing to embrittlement by facilitating crack propagation. Figure 16 shows the Niobium precipitates observed in the fracture surface close to the crack initiating site. In contrast, Type 2 steel welds with higher nitrogen content experience an increase in the chemical driving force for precipitation, resulting in enhanced toughness. In Type 2 steel welds, the HAZ toughness exceeds the weld toughness. Vanadium also reduces bainitic colony size contributing to improved toughness [ 2 ]. This Vanadium nitride precipitation leads to precipitation hardening, contributing to enhanced toughness. At -20 0 C, the impact toughness values of weld joints are suppressed due to the formation of brittle phases. Type 2 steel welds show higher HAZ impact toughness due to the improved ductility as compared with Type 1 steels. The SAW-T welds show higher HAZ toughness than SAW welds. The Charpy impact properties of the type 2 steel maintained the toughness through grain refinement by promoting ferrite nucleation on Nitrogen rich Vanadium carbonitrides co-precipitated on MnS inclusions as shown in Fig. 17 . Several researchers reported that Vanadium carbide nanometer-sized carbides can significantly improve the toughness properties of conventional ferritic steel [ 37 ]. 4. Conclusion The present study extensively investigates the use of SAW and SAW-T processes for Type 1 and Type 2 steel butt joints made of ASTM A572 Gr. 50 steel. The key observations and findings of the study are summarized as follows: Irrespective of the material being used in the present study, the SAW-T process exhibits increased weld width and top reinforcement due to the concentrated trail electrode arc on the lead wire molten pool. Type 1 steel welds, enriched with Niobium, exhibit superior mechanical properties compared to Type 2 steel welds including higher yield strength (≅ 7.9% higher) and ultimate tensile strength (≅ 4.8% higher) for both SAW and SAW-T processes. Furthermore, when comparing SAW-T to SAW, there is a noticeable increase in yield strength of 3.6% and ultimate tensile strength of 1.8%. These improvements are attributed to the development of acicular ferrite and the efficient dislocation locking mechanism facilitated by Niobium. At the given heat input, the SAW-T process influences the impact toughness properties at both 25 0 C and − 20 0 C for both steels. However, Type 2 steel welds show 30% higher impact toughness than Type 1 steels because the Vanadium carbides/ nitride precipitation leads to precipitation hardening contributing to enhanced toughness at 25 0 C. At -20 0 C, Type 2 steel welds show higher HAZ toughness due to improved ductility as compared with Type 1 steels. Type 1 SAW-T steel welds exhibit a 5.74% higher hardness compared to SAW, whereas Type 2 SAW steel welds show a minor 0.5% increase in hardness compared with SAW-T. In the HAZ, Type 1 SAW-T welds display a 3.3% higher hardness than SAW, while Type 2 SAW welds demonstrate a 4.3% higher hardness compared with SAW-T. SAW-T welds exhibit slightly higher microhardness in both weld and HAZ compared to SAW welds, due to differences in cooling rates and deposition rates. The higher hardness in Type 1 steel welds is attributed to the formation of Niobium carbides/ nitride and Titanium nitride. This research offers significant insights into how the SAW-T process impacts both the metallurgical and mechanical properties of welds compared to traditional SAW methods. It advocates the adoption of the SAW-T process over conventional SAW techniques specifically for welding 8 mm thick ASTM A572 Gr. 50 steels. Declarations Funding - This work was supported by TATA Steel Ltd. Jamshedpur, India (Grant Number IC2223MEE003TSLXDEGA). Degala Venkata Kiran has received research support from this grant. Competing Interests The authors declare no competing interests. Author contribution - Adapa Mahanth Kumar: conceptualization, methodology, investigation, validation, formal analysis, writing—original draft, visualization; Polamuri Sudheer Kumar : conceptualization, writing—review and editing, supervision, validation; Perka Ashok Kumar: conceptualization, writing—review and editing, resources, visualization, validation, funding acquisition; Degala Venkata Kiran: conceptualization, methodology, investigation, formal analysis, resources, supervision, writing—review and editing, visualization, project administration, and funding acquisition. Kanwer Singh Arora: conceptualization, writing—review and editing, resources; Nasina Venkaiah:conceptualization, methodology, investigation, formal analysis, resources, supervision, writing—review and editing, visualization, funding acquisition. Ethics approval - Not applicable Consent to participate - Not applicable Consent for publication - Not applicable Conflict of interests - The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Acknowledgment The authors would like to thank Joining and Metallography Laboratory, Department of Mechanical Engineering, IIT Tirupati, for experimental work support. Materials Welding & Joining Group, R&D, TATA Steel Limited, Jamshedpur is also acknowledged for metallography and mechanical characterization work. References Najafi H, Rassizadehghani J, Asgari S (2008) As-cast mechanical properties of vanadium/niobium microalloyed steels. 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Soldag e Insp 25:1–10. https://doi.org/10.1590/0104-9224/SI25.31 Sun Lyan, Liu X, Xu X et al (2022) Review on niobium application in microalloyed steel. J Iron Steel Res Int. https://doi.org/10.1007/s42243-022-00789-1 Rehder D (2015) The role of vanadium in biology. Metallomics 7:730–742. https://doi.org/10.1039/c4mt00304g Cite Share Download PDF Status: Published Journal Publication published 01 Oct, 2024 Read the published version in The International Journal of Advanced Manufacturing Technology → Version 1 posted Reviewers agreed at journal 01 Jul, 2024 Reviewers invited by journal 21 Jun, 2024 Editor assigned by journal 20 Jun, 2024 First submitted to journal 18 Jun, 2024 Editorial decision: Major Revisions Needed 08 Jun, 2024 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-4398172","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":317368282,"identity":"5cd6e027-4800-4fb2-86a2-875a1640c450","order_by":0,"name":"Adapa Mahanth Kumar","email":"","orcid":"","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Adapa","middleName":"Mahanth","lastName":"Kumar","suffix":""},{"id":317368283,"identity":"7c76baf1-0b83-446a-bb4e-68a2e95f1231","order_by":1,"name":"Polamuri Sudheer 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overhead flow of molten metal at lower travel speeds in the SAW process\u003c/p\u003e","description":"","filename":"9.png","url":"https://assets-eu.researchsquare.com/files/rs-4398172/v1/40efb3c24e308cb911bc31c5.png"},{"id":60115328,"identity":"e5705e70-7440-4111-aa93-31eefb4c2775","added_by":"auto","created_at":"2024-07-12 03:14:42","extension":"png","order_by":10,"title":"Figure 10","display":"","copyAsset":false,"role":"figure","size":393741,"visible":true,"origin":"","legend":"\u003cp\u003eBase metal microstructure of (a) Type 1 (b) Type 2 steels\u003c/p\u003e","description":"","filename":"10.png","url":"https://assets-eu.researchsquare.com/files/rs-4398172/v1/d2be7e2c04bf379442bf0bba.png"},{"id":60116032,"identity":"3785b688-a57f-47fb-936c-283bc1b8c92c","added_by":"auto","created_at":"2024-07-12 03:22:42","extension":"png","order_by":11,"title":"Figure 11","display":"","copyAsset":false,"role":"figure","size":1181112,"visible":true,"origin":"","legend":"\u003cp\u003eSEM image of weld microstructure of Type 1 steel (a) SAW (b) SAW-T, Type 2 steel (c) SAW (d) SAW-T\u003c/p\u003e","description":"","filename":"11.png","url":"https://assets-eu.researchsquare.com/files/rs-4398172/v1/961d3931e5109467e789e64a.png"},{"id":60116034,"identity":"1468bacc-e663-4aed-bcaa-00ef984ab65b","added_by":"auto","created_at":"2024-07-12 03:22:42","extension":"png","order_by":12,"title":"Figure 12","display":"","copyAsset":false,"role":"figure","size":959347,"visible":true,"origin":"","legend":"\u003cp\u003eCGHAZ microstructure of Type 1 steel (a) SAW (b) SAW-T, Type 2 steel (c) SAW (d) SAW-T\u003c/p\u003e","description":"","filename":"12.png","url":"https://assets-eu.researchsquare.com/files/rs-4398172/v1/bb635fbca722ed72dfb30b77.png"},{"id":60115330,"identity":"b8fcc0d7-50e7-4997-827d-1a99403bd6dc","added_by":"auto","created_at":"2024-07-12 03:14:42","extension":"png","order_by":13,"title":"Figure 13","display":"","copyAsset":false,"role":"figure","size":724337,"visible":true,"origin":"","legend":"\u003cp\u003eMicro hardness contours of (a) Type 1 SAW (b) Type 1 SAW-T (c) Type 2 SAW (d) Type 2 SAW-T welds\u003c/p\u003e","description":"","filename":"13.png","url":"https://assets-eu.researchsquare.com/files/rs-4398172/v1/ff7b64210cd8dd42b7d43329.png"},{"id":60115334,"identity":"debb6889-bc3f-477c-b048-d8c874491586","added_by":"auto","created_at":"2024-07-12 03:14:42","extension":"png","order_by":14,"title":"Figure 14","display":"","copyAsset":false,"role":"figure","size":483976,"visible":true,"origin":"","legend":"\u003cp\u003eTensile strength of Type 1 and Type 2 butt joints\u003c/p\u003e","description":"","filename":"14.png","url":"https://assets-eu.researchsquare.com/files/rs-4398172/v1/5abe4d144cbff57e258a6e39.png"},{"id":60116033,"identity":"10ee2e0e-13f2-4e4f-8cb4-e774b3033450","added_by":"auto","created_at":"2024-07-12 03:22:42","extension":"png","order_by":15,"title":"Figure 15","display":"","copyAsset":false,"role":"figure","size":1826304,"visible":true,"origin":"","legend":"\u003cp\u003eImpact toughness of Type 1 and Type 2 butt joints (a) at 25\u003csup\u003e0\u003c/sup\u003eC (b) at -20\u003csup\u003e0\u003c/sup\u003eC temperature\u003c/p\u003e","description":"","filename":"15.png","url":"https://assets-eu.researchsquare.com/files/rs-4398172/v1/5adab2ac321bc87311a83512.png"},{"id":60115336,"identity":"d73beb49-70b0-4efe-8822-7c85940d4635","added_by":"auto","created_at":"2024-07-12 03:14:42","extension":"png","order_by":16,"title":"Figure 16","display":"","copyAsset":false,"role":"figure","size":320937,"visible":true,"origin":"","legend":"\u003cp\u003eSEM micrographs showing the Niobium carbonitride precipitates on the Type 1 steel HAZ fracture surface\u003c/p\u003e","description":"","filename":"16.png","url":"https://assets-eu.researchsquare.com/files/rs-4398172/v1/5ab824ff3ecb432f2b85a6a8.png"},{"id":60115338,"identity":"032b510e-e835-45f4-ad24-0b5393f77c62","added_by":"auto","created_at":"2024-07-12 03:14:42","extension":"png","order_by":17,"title":"Figure 17","display":"","copyAsset":false,"role":"figure","size":334074,"visible":true,"origin":"","legend":"\u003cp\u003eSEM micrographs showing the potential Vanadium carbonitride particle location along with the MnS inclusions on the Type 2 steel HAZ fracture surface\u003c/p\u003e","description":"","filename":"17.png","url":"https://assets-eu.researchsquare.com/files/rs-4398172/v1/98d208705e9db735065bea3c.png"},{"id":66097302,"identity":"bba45b04-2615-48ac-8cfa-b97ed013eeb1","added_by":"auto","created_at":"2024-10-07 16:13:58","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":12514530,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4398172/v1/8b23a9cf-1d0b-4717-b5fe-531102f69a8e.pdf"}],"financialInterests":"","formattedTitle":"Influence of single and tandem-submerged Arc Welding on ASTM A572 Gr.50 steels","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eThe general trend in structural steels has been to attain good toughness and weldability while decreasing the carbon content and increasing the mechanical properties through microalloying addition. Accordingly, several microalloying grades were developed with the addition of Niobium, Vanadium, and Titanium, etc. ASTM A572 Gr.50 is a structural steel that finds extensive applications in fabrication due to its commendable strength and toughness, with the inclusion of micro alloying elements such as Niobium or Vanadium aimed at enhancing its mechanical properties. Depending on the type of alloying elements, these steels are categorized as Type 1 steels (Nb added) and Type 2 steels (V added). The primary purpose of adding Niobium to steel is to regulate the size of the austenite grains. Niobium precipitates as Niobium carbide and Niobium carbonitride and governs the grain size via the pinning effect [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. Vanadium is another micro alloying element added to steel to refine the grains. Vanadium, when combined with nitrogen, creates stable Vanadium nitride, thereby enhancing the steel's strength through precipitation hardening [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. Between Niobium and Vanadium, Niobium exhibits greater potential than Vanadium in precipitation hardening due to the binding energy of Niobium to austenite grain boundaries compared to Vanadium. Bhattacharya et al. [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e] studied the effect of different states of Niobium on the evolution of Heat affected zone (HAZ) microstructure in SAW X80 pipe welds. The reduction in transformation temperature for a constant prior austenite grain size is strongly correlated to the presence of dissolved Niobium, as the prior austenite grains serve as sites for heterogeneous nucleation in the HAZ.\u003cdiv class=\"BlockQuote\"\u003e\u003cp\u003eSAW is preferred for welding the medium to high thickness plates used in pressure vessels, offshore structures, and marine and pipeline industries because of its higher deposition rate and good surface quality [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. Conventional SAW machines generally work on direct current electrode positive (DCEP) or negative polarity (DCEN) [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. The DCEN yields high weld deposition and less penetration, as compared to the DCEP. In general, the weld bead geometry is influenced by various parameters such as polarity, welding current, welding voltage, wire feed speed, electrode extension, and welding speed. Yang et al. [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e] asserted that the utilization of DCEP instead of DCEN, along with a larger electrode diameter of 3.2 mm, a reduced electrode extension of 25.4 mm, and an increased welding voltage promotes the attainment of a larger weld width and higher penetration in SAW. Furthermore, it was observed that, when employing basic fluxes under constant current power source conditions, a greater weld width is achieved compared to constant voltage power source conditions. Ali et al. [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e] studied the effect of arc voltage and current intensity on weld penetration depth in submerged arc welding, revealing that increasing both arc voltage and current intensity enhances penetration depth.\u003c/p\u003e\u003cp\u003eAn alternating current (AC) is an appropriate option to obtain the advantages of both polarities [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. In AC, the electrode is in positive polarity for a portion of a cycle and negative polarity for the remainder. In AC square waveform, parameters like balance, offset, and frequency can change the bead geometry apart from conventional parameters. Balance is the percentage of positive polarity time in one complete AC cycle, the offset is the percentage variation (increase or decrease) in positive polarity peak current magnitude, and the frequency denotes the number of AC cycles occurring within one second. Figure\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e depicts the schematic diagram of waveforms with different offset and balance parameters. The waveform modulation in SAW can be adjusted using power electronics to optimize parameters and achieve an optimal weld. Full-wave control technology evolved in SAW to alter the waveform variables in AC power sources [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. It is an excellent choice to manipulate the waveforms in SAW to achieve welding productivity and quality. Pepin et al. [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e] conducted a set of bead-on-plate (BOP) weld experiments using a single wire SAW process, systematically varying the balance and offset parameters, and analyzed their impact on weld geometry. The findings indicated that increasing the balance and decreasing the offset leads to maximum base metal penetration.\u003c/p\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"BlockQuote\"\u003e \u003cp\u003eOpting for two wires instead of a single wire is a preferred option to enhance the productivity of SAW. The two-wire tandem submerged arc welding (SAW-T) process employs two independent electrode wires, fed through separate wire feeders and controlled by distinct power sources. In SAW-T, the lead wire electrode is linked to a direct current power source, while the trail wire electrode is attached to an alternating current power source to mitigate arc blow [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e, \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. The utilization of large-diameter wire electrodes and increased wire feed speeds (WFS) contributes to high deposition rates, resulting in enhanced productivity. Kiran et al. [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e, \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e] studied the influence of lead wire electrode current, trail wire electrode current pulses, and welding speed on weld dimensions in a single pass bead-on-groove (BOG) SAW-T of high strength low alloy (HSLA) steel. The depth of weld penetration is mainly affected by the lead wire electrode current, whereas weld width is notably responsive to the trail wire electrode current. Mohsen et al. [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e] developed tandem submerged arc welding with an additional cold wire (CWTSAW) to enhance productivity [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e] by increasing the deposition rate and travel speed. Bead-on-groove welds with a 90\u0026deg; V-shaped bevel angle were prepared using both SAW-T and CWTSAW. The study compared these processes, highlighting the effects of the cold wire addition on the dilution area, microhardness, and microstructure of the weldment. The addition of the cold wire reduces the overall heat introduced to the weldment, decreasing dilution and the coarse grain heat-affected zone (CGHAZ) area, while faster cooling rates result in lower microhardness values in the CGHAZ. Tailin Ren et al. [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e] investigated the critical role of optimizing process variables in CWTSAW to enhance productivity, control weld quality, and improve mechanical properties in heavy gauge pipe welding applications. The cold wire feed speed significantly influences micro-hardness profiles by modifying local thermal cycles [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]. By adjusting the cold wire feed speed, the amount of heat absorbed from the molten pool can be controlled. This alteration in heat input affects the cooling rate of the weld metal and the heat-affected zone, leading to changes in the microstructure and hardness distribution. Comprehensive studies have already been conducted on the impact of welding parameters on the weld geometry and mechanical properties of BOP and BOG welds. The aforementioned studies were employed to choose the polarities for SAW and SAW-T welds in the present study.\u003c/p\u003e \u003cp\u003eAs per ISO 9692-2:1998(E), for SAW of steels with a thickness ranging from 3 to 12 mm, it is recommended to prepare a square butt weld with a root gap not exceeding 0.5 times the thickness of the plate or a gap of 5 mm, along with utilizing a backing bar with a minimum thickness of 5 mm [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]. The process of joining medium to thick steel plates with a square butt configuration involves welding from the top, then flipping over the welded plates, gouging the root, and subsequently completing the final bottom welding. Performing these many operations is a tedious and costly process. To address these challenges, the utilization of flux-filled aluminum/copper backing or ceramic backing is employed in the SAW. Ceramic backing is non-reusable, and flux-filled aluminum backing can melt if the dimensions of the backing groove are improper. In contrast, flux-filled copper backing has certain advantages, such as its high thermal conductivity, facilitating efficient heat transfer to the surroundings. Additionally, the life of the copper backing is longer because of its immiscible property.\u003c/p\u003e \u003cp\u003eMandal et al. [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e] investigated the combined influence of process parameters like voltage, current, speed, and thickness on weld penetration in 8 mm C-Mn steel plates. The study employed a V groove with a 50\u0026deg; included angle, single side single pass SAW, and a flux-filled aluminum backing. The study identified that optimal conditions for achieving through-thickness fusion in 8 mm plates involved a 3 mm root opening and zero root face, with a required heat input of 1.2 kJ/mm. Furthermore, the use of fine-grained flux in the aluminum backing resulted in improved bottom reinforcement. Utilizing flux-filled aluminum backing without fine-grained flux results in inadequate bottom reinforcement. According to ISO 9692-2:1998(E), a V-groove joint is not advisable for joining 8 mm thick plates. Instead, a square butt joint should be performed. Sridhar et al. [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e] investigated the impact of welding parameters on bead geometry and tensile properties in an 8 mm thick square butt joint with a root gap of 2.5 mm using double-sided SAW on SS 304 stainless steel plates. The study shows that the higher welding current results in increased penetration and bead overlap, while increased voltage leads to wider beads. A higher welding speed results in reduced weld width and penetration. In addition to that, double-sided weld joints demonstrated improved elongation compared to the base material. However, employing double-sided weld joints extends production time and consumes excess filler material. Therefore, economically, preparing the 8 mm thick steel plate joint with a single side single pass is preferable.\u003c/p\u003e \u003cp\u003eBiswas et al. [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e] explored the impact of heat input, root gap, and welding speed on the quality of joints formed on plates with thicknesses of 3 mm, 5 mm, and 12 mm. The study utilized a single side single pass SAW with a square butt joint and a flux-filled aluminum backing. It is observed that slower welding speeds were necessary for joining thicker plates. Furthermore, it is noted that achieving full penetration in a single pass for 12 mm plates required a specific heat input of 3.5 kJ/mm. To enhance process productivity, higher welding speeds are necessary. However, achieving this requirement is hindered by the slower welding speeds associated with preparing a joint using single-pass SAW. In another study, Biswas et al. [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e] achieved through-thickness fusion in 8 mm C-Mn steel plates using a square butt configuration with a 2.6 mm root gap and a flux-filled aluminum backing. The optimal parameters identified for achieving full penetration were 570 A welding current, 29 V voltage, and a welding speed of 6.25 mm/s, which constitute the primary data for our study. Sailender et al. [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e] identified critical parameters and projected optimal input parameters that affect dilution and heat affected zone in 8 mm thick V-butt joints of SAW-welded ASTM A516 Gr. 70 low carbon steel with a copper backing plate in their work. The study shows that the welding speed is the predominant factor influencing the width of HAZ. Researchers in the past prepared a square butt joint of 8 mm thick plates using the SAW process at lower speeds. However, joining of the 8 mm thick plates using a square butt joint configuration with the SAW-T process is not practiced. Additionally, there is a lack of available literature on the suitable process parameters for preparing square butt joints in 8 mm thick plates using SAW-T. Furthermore, the literature does not clearly address the effect of using two wires in the SAW-T process on the mechanical properties of joints, including strength, toughness and hardness, when prepared with a single side single pass compared to traditional SAW. To improve productivity without compromising weld mechanical properties, adopting SAW-T is necessary.\u003c/p\u003e \u003cp\u003eThe thermal cycles experienced during welding can compromise the balance of high strength and good toughness in Nb-V steels, leading to poor toughness in the HAZ during the SAW and SAW-T process. The SAW-T process is not yet employed for the joining of 8 mm thick steel plates. Additionally, the effect of SAW and SAW-T process parameters on the microstructural changes in ASTM A572 Gr. 50 Type 1 and Type 2 steels, which subsequently influence the mechanical properties of the steel joints, is not available in the literature. Furthermore, detailed studies on understanding the effect of tandem wire electrodes over a single electrode have not yet reported. The choice of steel type also exerted a notable impact on the weld properties. The present work involves a thorough experimental investigation by employing two electrodes versus a single electrode on the weld profile, weld, and HAZ microstructure during 8 mm single-side single-pass welding of ASTM A572 Gr. 50 Type 1 and Type 2 steels. Comprehensive mechanical characterization was conducted, encompassing the tensile strength, impact toughness of weld samples, and microhardness of the weldment.\u003c/p\u003e \u003c/div\u003e \u003c/p\u003e"},{"header":"2. Experimental investigation","content":"\u003cp\u003eThe elemental composition of the ASTM A572 Gr. 50 steel base plates of Type 1 and Type 2, and the electrode wire are presented in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. The carbon equivalent (CE) of Type 1 and Type 2 materials are 0.361 and 0.366, estimated using Eq.\u0026nbsp;1 [\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]. As the workpiece materials used in this study have a carbon content of \u0026cong; 0.14 and low CE (\u0026cong; 0.366), this class of steels has lower hardenability and good weldability. EH 14 \u0026ndash; F7A4 flux combination is used for this work, and its corresponding elemental composition is given in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. The ASTM A572 Gr. 50 steel plates of 450 X 150 X 8 mm are used to perform the square butt weld joint experiments. The workpiece faying surfaces are grounded to remove rust, and the surface is thoroughly cleaned with acetone to remove the contamination. A consistent root gap of 2.8 mm was maintained between the steel plates with proper clamping.\u003cdiv id=\"Equa\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equa\" name=\"EquationSource\"\u003e\n$$\\text{C}\\text{E}=\\text{%}\\text{C}+\\frac{(\\text{%}\\text{S}\\text{i}+\\text{%}\\text{M}\\text{n})}{6}+\\frac{(\\text{%}\\text{C}\\text{u}+\\text{%}\\text{N}\\text{i})}{15}+\\frac{(\\text{%}\\text{V}+\\text{%}\\text{M}\\text{o}+\\text{%}\\text{C}\\text{r})}{5} \\left(1\\right)$$\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eThe elemental composition (wt %) of the base plate and electrode\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"15\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c10\" colnum=\"10\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c11\" colnum=\"11\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c12\" colnum=\"12\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c13\" colnum=\"13\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c14\" colnum=\"14\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c15\" colnum=\"15\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eGrade\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e \u003cp\u003eC\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eMn\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eS\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eP\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003eSi\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c8\"\u003e \u003cp\u003eAl\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c9\"\u003e \u003cp\u003eN\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c10\"\u003e \u003cp\u003eNi\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c11\"\u003e \u003cp\u003eCr\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c12\"\u003e \u003cp\u003eCu\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c13\"\u003e \u003cp\u003eV\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c14\"\u003e \u003cp\u003eNb\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c15\"\u003e \u003cp\u003eTi\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e \u003cp\u003eType1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.14\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.152\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.005\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.02\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0.012\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0.053\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e0.0036\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e0.024\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e0.026\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c12\"\u003e \u003cp\u003e0.008\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c13\"\u003e \u003cp\u003e0.001\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c14\"\u003e \u003cp\u003e\u003cb\u003e0.023\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c15\"\u003e \u003cp\u003e0.023\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e \u003cp\u003eType2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.136\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.185\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.004\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.02\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0.099\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0.039\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e0.006\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e0.025\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e0.032\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c12\"\u003e \u003cp\u003e0.008\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c13\"\u003e \u003cp\u003e\u003cb\u003e0.036\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c14\"\u003e \u003cp\u003e0.001\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c15\"\u003e \u003cp\u003e0.002\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e \u003cp\u003eElectrode\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.1\u0026ndash;0.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.7\u0026ndash;2.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.03\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.03\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0.10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c12\"\u003e \u003cp\u003e0.35\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c13\"\u003e \u003cp\u003e\u003cb\u003e-\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c14\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c15\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eThe elemental composition (wt %) of the flux\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"9\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eElement\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eSiO\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eMnO\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eMgO\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eCaF\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eNa\u003csub\u003e2\u003c/sub\u003eO\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003eAl\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c8\"\u003e \u003cp\u003eP\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c9\"\u003e \u003cp\u003eS\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eFlux\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e22.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e4.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e25\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e19.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e2.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e20.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0.029\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e0.015\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e(a) depicts the schematic representation of the experimental setup utilized in this study. The setup includes the Lincoln AC/DC 1000 SAW-T unit which can independently control the leading and trailing arcs with two power sources. A copper backing plate with a circular groove filled with flux is used to support the molten weld pool and ensure complete bottom-edge fusion. A constant voltage power source is used for both leading and trailing arcs. The welding head moves on the gantry system where the welding torch is mounted, while the working table is stationary. The optimum groove dimensions are chosen for the copper backing bar to achieve proper bottom reinforcement of the weld bead which directly affects the top reinforcement. This setup allows for real-time monitoring of current-voltage from the lead and trail wire electrodes. In Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e(b), an enlarged view depicts two electrodes arranged in tandem configuration, where the lead electrode is perpendicular to the welding direction, and the trail electrode forms a 18\u003csup\u003e0\u003c/sup\u003e angle with the axis of the lead electrode.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eMultiple trial runs were conducted to find the most suitable parameters to obtain a sound weld with ease of slag removal and to get a sound weld joint, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e. From the available literature, appropriate process parameters such as welding current, voltage, and travel speed are chosen for conducting the SAW \u0026amp; SAW-T Butt joint welds. Preliminary bead on plate welds are performed with SAW and SAW-T processes on low carbon steel plates. Considering the weld dimensions from the bead-on plate trial experiments, the SAW and SAW-T butt joint weld parameters are determined. For SAW, the DCEP polarity is used, and for SAW-T butt joint welds for lead wire electrode, DCEP polarity and trail wire electrode AC square wave with 50% balance and 0% offset are used. Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e depicts the welding parameters employed in the current investigation. The experiments on ASTM A572 Gr. 50 steel are performed with the parameters presented in Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eWelding parameters used for butt joint welds\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eS. No.\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eWeld process parameter\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eSAW\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e \u003cp\u003eSAW-T\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eLead wire\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eTrail wire\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eElectrode diameter (mm)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e3.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e3.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eElectrode extension (mm)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e25\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e25\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e30\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003ePolarity\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eCV DCEP\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eCV DCEP\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eCV AC Sq. wave\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eElectrode angle (\u003csup\u003e0\u003c/sup\u003e)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e90\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e90\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e18 to the electrode axis\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eInter-electrode distance (mm)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e \u003cp\u003e20\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eRoot gap (mm)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e \u003cp\u003e2.8\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eHeat input (kJ/mm)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e \u003cp\u003e2.5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eHeat Input is computed for all experiments utilizing the recorded current and voltage waveforms. The average power consumption and heat input are calculated using Eqs.\u0026nbsp;2 and 3 [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]. A process efficiency (η) of 0.95 is used for heat input calculations [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e]. A constant heat input of 2.5 kJ/mm is employed for SAW and SAW-T welds.\u003cdiv id=\"Equb\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equb\" name=\"EquationSource\"\u003e\n$$\\text{P}\\text{o}\\text{w}\\text{e}\\text{r}, \\text{P}=\\frac{\\sum _{\\text{i}=1}^{\\text{n}}{I}_{\\text{i}}{V}_{i} t}{\\sum _{\\text{i}=1}^{\\text{n}}t} \\left(2\\right)$$\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003eWhere, I\u003csub\u003ei\u003c/sub\u003e and V\u003csub\u003ei\u003c/sub\u003e are instantaneous currents and voltage, respectively, and \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(t\\)\u003c/span\u003e\u003c/span\u003e is the difference in cycle time.\u003cdiv id=\"Equc\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equc\" name=\"EquationSource\"\u003e\n$$\\text{H}\\text{e}\\text{a}\\text{t} \\text{I}\\text{n}\\text{p}\\text{u}\\text{t}= \\frac{{\\eta }P}{\\text{W}\\text{e}\\text{l}\\text{d}\\text{i}\\text{n}\\text{g} \\text{s}\\text{p}\\text{e}\\text{e}\\text{d} } \\left(3\\right)$$\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab4\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eProcess parameters for SAW and SAW-T processes\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"14\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c10\" colnum=\"10\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c11\" colnum=\"11\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c12\" colnum=\"12\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c13\" colnum=\"13\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c14\" colnum=\"14\"\u003e\u003c/div\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eExp. No.\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eASTM A572 Gr.50 steel\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eWelding Process\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e \u003cp\u003eWFS (mm/s)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c7\" namest=\"c6\"\u003e \u003cp\u003eWelding current (A)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c9\" namest=\"c8\"\u003e \u003cp\u003eWelding voltage V)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c11\" namest=\"c10\"\u003e \u003cp\u003eBal (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c13\" namest=\"c12\"\u003e \u003cp\u003eOff (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c14\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eWelding speed (mm/s)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eL\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eT\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eL\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003eT\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003eL\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003eT\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003eL\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003eT\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c12\"\u003e \u003cp\u003eL\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c13\"\u003e \u003cp\u003eT\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eType 1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eSAW\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e26.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e510\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c12\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c13\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c14\"\u003e \u003cp\u003e6\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eSAW-T\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e30.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e14.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e560\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e390\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e29\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e29\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e50\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c12\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c13\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c14\"\u003e \u003cp\u003e10\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eType 2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eSAW\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e26.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e510\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c12\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c13\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c14\"\u003e \u003cp\u003e6\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eSAW-T\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e30.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e14.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e560\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e390\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e29\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e29\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e50\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c12\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c13\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c14\"\u003e \u003cp\u003e10\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eL \u0026ndash; Lead electrode and T \u0026ndash; Trail electrode\u003c/p\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e provides an overview of the locations where the tensile, Charpy, metallography, micro hardness, and microstructure specimens are extracted. The sectioned weld samples are mirror polished using an automatic disc polisher with successive grit papers from 80 to 2000 size and then cloth polished with a diamond suspension of particle size 1 \u0026micro;m and then etched using 2% nital solution comprising 98% ethanol and 2% nitric acid by agitate for 14 s. [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e].\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe macrographs are acquired from a PC-coordinated stereo microscope. The measurements of the fusion zone include weld width, penetration, and reinforcement. Base metal and HAZ micro images are captured using a metallurgical microscope. The weld metal micro images are captured from SEM. The volume fractions of acicular ferrite phases are measured in the weld zone. The mechanical characterization involves the tensile strength of the weld, impact toughness of the joint at 25\u003csup\u003e0\u003c/sup\u003e C and \u0026minus;\u0026thinsp;20\u003csup\u003e0\u003c/sup\u003e C temperatures, and hardness contours of the weld samples.\u003c/p\u003e \u003cp\u003eTransverse tensile weld specimens are extracted from the weld joint. The dimensions of the tensile test specimen used in the present work follow the ASTM E8M standard [\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e]. Figure\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e (a-c) shows the schematic representation of the impact toughness specimens extracted from welds with the notch positioned at the weld center, + 2 mm from the fusion line (FL), and +\u0026thinsp;5 mm from the fusion line. Figure\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e shows the schematic of locations for hardness measurement for obtaining the hardness contours for the weldment. The distance between the two consecutive locations is 0.5 mm. Vickers diamond hardness tester is used with a load of 300 g force for 13 seconds.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e"},{"header":"3. Results and discussion","content":"\u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e illustrates the instantaneous welding current and voltage readings for both DCEP and AC square waveforms recorded while performing Type 1 SAW and SAW-T welds. Similar trends are observed in Type 2 butt joints also. Under constant voltage (CV) mode, input data includes the wire feed speed and voltage, and the recorded welding voltage and current are obtained through the Data Acquisition (DAQ) system. The welding current and voltage recorded for SAW are 515\u0026thinsp;\u0026plusmn;\u0026thinsp;3 Amps and 30\u0026thinsp;\u0026plusmn;\u0026thinsp;0.1 volts, respectively. In the case of SAW-T, the recorded current of the lead wire electrode is 543.5\u0026thinsp;\u0026plusmn;\u0026thinsp;2.5 Amps, the trail wire electrode is 389.5\u0026thinsp;\u0026plusmn;\u0026thinsp;1.5 Amps, and the voltage is 29\u0026thinsp;\u0026plusmn;\u0026thinsp;0.1 volts. These readings suggest negligible variation in welding current and voltage with the provided input data. From Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e(c), it is evident that the trail electrode operates with AC 50% balance and 0% Offset.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e(a)-(d) illustrates the weld macrograph of Type 1 and Type 2 steel for SAW and SAW-T welds. Weld macro images show proper top and bottom reinforcement along the side wall fusion, achieved with parameters detailed in Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e. A noticeable disparity in weld dimensions is observed between Type 1 and Type 2 welds. An increase in SAW-T weld width and top reinforcements compared with SAW is evident in Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e(b, d). It is well understood from the literature that in the case of the tandem wire welding process, the trail wire welding arc is concentrated on the top of the lead wire molten pool rather than the previously deposited/base metal layer [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e]. Consequently, the flow of molten metal in this region leads to enhanced weld width. Furthermore, as the number of passes needed to complete the weld joint in both SAW and SAW-T is one in the present study, it is required to maintain lower travel speeds in the case of SAW compared to SAW-T process. Lower travel speed results in the overhead flow of the molten metal which hinders the welding arc to strike the lower region of the weld as shown schematically in Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003e, resulting in the narrow weld fusion in the middle of the weld joint [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e]. However, the groove in the copper backing plate enhances the molten pool\u0026rsquo;s flow in the lower end of the narrow gap enabling the side wall fusion.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eIrrespective of the material (Type 1 or Type 2), a higher weld reinforcement width is observed in SAW-T welds than in SAW. As the welding speed is higher in the case of the SAW-T process, the lead wire arc strikes the base/initial/copper plate, rather than the overhead flow of the molten pool. Additionally, the trail wire arc strikes the molten pool created by the lead wire, resulting in high-intensity arc concentration in this region, which leads to higher weld reinforcement widths in this area [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e].\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFigures\u0026nbsp;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e10\u003c/span\u003e, \u003cspan refid=\"Fig11\" class=\"InternalRef\"\u003e11\u003c/span\u003e, and \u003cspan refid=\"Fig12\" class=\"InternalRef\"\u003e12\u003c/span\u003e depict the microstructures of the base metal (BM), weld metal (WM), and HAZ of Type 1 and Type 2 steel welds. In Fig.\u0026nbsp;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e10\u003c/span\u003e(a), the base metal microstructure of Type 1 steels reveals a combination of ferrite and pearlite. In the figure, the white and black structures represent ferrite and pearlite structures respectively. Pearlite has a polygonal shape, and a considerable part of the ferrite matrices were connected. The distribution of pearlite and ferrite appears to be uniform, and there were some ferrites with sizes of less than 3 \u0026micro;m. The average grain size of Type 1 steel is measured as 4\u0026ndash;5 \u0026micro;m, and this refined grain size results in the pinning effect of Niobium precipitates [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. The presence of stable Titanium nitride further contributes to restricting grain growth in Type 1 steels [\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e]. As outlined in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e, Type 2 steels have high Vanadium and Nitrogen content, and Vanadium nitride, identified as more stable than vanadium carbide, plays a role in inhibiting recrystallization by exerting pinning forces [\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e]. Figure\u0026nbsp;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e10\u003c/span\u003e(b) shows the base metal microstructure of Type 2 steel. The average grain size of Type 2 BM is measured as 7\u0026ndash;8 \u0026micro;m. Despite this, Niobium is recognized as a more effective grain refiner than Vanadium, precipitating more readily in austenite and offering greater potential for precipitation hardening [\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e].\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFigures\u0026nbsp;\u003cspan refid=\"Fig11\" class=\"InternalRef\"\u003e11\u003c/span\u003e(a) and (b) illustrate the weld microstructure of Type 1 steels for the SAW and SAW-T process. Acicular ferrite (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({}_{\\text{A}})\\)\u003c/span\u003e\u003c/span\u003e and grain boundary ferrite \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({(}_{\\text{G}\\text{b}})\\)\u003c/span\u003e\u003c/span\u003e are observed in the weld microstructure. The carbonitrides of Niobium, precipitated at austenite grain boundaries, act as sites for heterogeneous nucleation, facilitating the nucleation of grain boundary ferrite [\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e]. Figures\u0026nbsp;\u003cspan refid=\"Fig11\" class=\"InternalRef\"\u003e11\u003c/span\u003e(c) and (d) show the weld microstructures of Type 2 steels for the SAW and SAW-T process. In both type 1 and type 2 steels, \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({}_{\\text{G}\\text{b}}\\)\u003c/span\u003e\u003c/span\u003e was more developed when the SAW-T process was used than in the SAW process. Also, it was observed that the intragranular microstructure, acicular ferrite was coarser in SAW-T. This could be due to the rapid cooling rate influenced by the high travel speed during the SAW-T process in comparison to the SAW process.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFigures\u0026nbsp;\u003cspan refid=\"Fig12\" class=\"InternalRef\"\u003e12\u003c/span\u003e(a) and (b) illustrate the Coarse grained heat affected zone (CG HAZ) microstructures of Type 1 steel for SAW and SAW-T welds, captured adjacent to the fusion line. Micrographic analysis revealed that the primary microstructural constituents in the case of SAW samples were polygonal ferrite and pearlite due to the slower cooling rates. In the case of SAW-T samples, the microstructure comprised lath-type/bainitic ferrite and degenerated pearlite, alongside conventional ferrite-pearlite. Notably, a bainite/martensite microstructure is evident in the form of needle-like structures, despite not being explicitly mentioned in the initial observation. The influence of Niobium precipitates on austenite/ferrite transformation is evident, as Niobium solute increases the stability of supercooled austenite and reduces the transformation temperature [\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e]. The presence of Niobium solute suppresses the transformation of grain boundary ferrite while promoting the transformation towards bainite or martensite. Additionally, in SAW-T welds, larger grain boundary ferrites are noted in comparison to SAW welds. This can be attributed to the higher deposition rates, resulting in slower cooling rates [\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e]. Figures\u0026nbsp;\u003cspan refid=\"Fig12\" class=\"InternalRef\"\u003e12\u003c/span\u003e(c) and (d) exhibit CG HAZ microstructures of Type 2 steel in SAW and SAW-T welds. In the CG HAZ of Type 2 SAW steel welds, a bainitic microstructure is evident alongside lamellar ferrite. In the case of SAW-T welds, a similar microstructure is observed, but with an increase in grain boundary ferrite size and a concurrent reduction in the presence of lamellar ferrite.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eHardness contours were plotted for Type 1 and Type 2 steel welds for the SAW and SAW-T weld conditions, as depicted in Fig.\u0026nbsp;\u003cspan refid=\"Fig13\" class=\"InternalRef\"\u003e13\u003c/span\u003e(a) \u0026ndash; (d). The average microhardness values for the weld metal are 209\u0026thinsp;\u0026plusmn;\u0026thinsp;5 HV (Type 1 SAW), 221\u0026thinsp;\u0026plusmn;\u0026thinsp;6 HV (Type 1 SAW-T), 206\u0026thinsp;\u0026plusmn;\u0026thinsp;5 HV (Type 2 SAW), and 205\u0026thinsp;\u0026plusmn;\u0026thinsp;9 HV (Type 2 SAW-T). Irrespective of the welding conditions and the type of material used, the weld region has a higher hardness compared with the HAZ region due to the influence of the alloying elements within the weld metal and the formation of the acicular ferrite. Although there is not much variation in weld hardness, a slight drop in hardness values was observed in the case of SAW welds compared to the SAW-T welds. This might be attributed to the supplementary heat source from the trail wire electrode and slower cooling rates, which contribute to balancing the hardness of the HAZ [\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e]. In the CG HAZ, the average microhardness values are 191\u0026thinsp;\u0026plusmn;\u0026thinsp;11 HV (Type 1 SAW), 200\u0026thinsp;\u0026plusmn;\u0026thinsp;8 HV (Type 1 SAW-T), 192\u0026thinsp;\u0026plusmn;\u0026thinsp;11 HV (Type 2 SAW), and 177\u0026thinsp;\u0026plusmn;\u0026thinsp;5 HV (Type 2 SAW-T). Average microhardness of HAZ are 180\u0026thinsp;\u0026plusmn;\u0026thinsp;14 HV (Type 1 SAW), 186\u0026thinsp;\u0026plusmn;\u0026thinsp;14 HV (Type 1 SAW-T), 186\u0026thinsp;\u0026plusmn;\u0026thinsp;11 HV (Type 2 SAW), and 178\u0026thinsp;\u0026plusmn;\u0026thinsp;8 HV (Type 2 SAW-T). Type 1 SAW-T samples demonstrate higher hardness in the HAZ than Type 2 SAW-T samples. It clearly shows that Type 2 samples HAZ is slightly softer than the Type 1 samples HAZ. The decrease in hardness may be attributed to the fact that, despite the dispersion of Niobium carbide and Titanium carbide being relatively finer than that of Vanadium carbide when the same amount of alloy is added, a greater driving force for precipitation was required to achieve the same number density of Niobium carbide and Titanium carbide as that of Vanadium carbide. Additionally, the top and bottom sides of the weld exhibit higher hardness due to faster cooling resulting from convection with the atmosphere on top and the presence of a copper backing plate at the bottom of the weld.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig14\" class=\"InternalRef\"\u003e14\u003c/span\u003e illustrates the influence of welding conditions on the tensile properties of Type 1 and Type 2 steel weld joints. Regardless of the SAW or SAW-T process, Type 1 steel welds exhibit higher ultimate tensile strength, measuring 535.5\u0026thinsp;\u0026plusmn;\u0026thinsp;8.5 MPa for SAW and 546\u0026thinsp;\u0026plusmn;\u0026thinsp;6 MPa for SAW-T process than that of Type 2 steel welds, which measure 513\u0026thinsp;\u0026plusmn;\u0026thinsp;14 MPa for SAW and 515\u0026thinsp;\u0026plusmn;\u0026thinsp;17 MPa for SAW-T. Similarly, Type 1 steel welds demonstrate higher yield strength (σ\u003csub\u003ey\u003c/sub\u003e) at 419\u0026thinsp;\u0026plusmn;\u0026thinsp;8 MPa for SAW and 434.5\u0026thinsp;\u0026plusmn;\u0026thinsp;5.5 MPa for SAW-T, in contrast to Type 2 steel welds, which exhibit 390\u0026thinsp;\u0026plusmn;\u0026thinsp;10 MPa for SAW and 394.5\u0026thinsp;\u0026plusmn;\u0026thinsp;12.5 MPa for SAW-T. Type 2 steel welds exhibit a percent elongation of 22.5\u0026thinsp;\u0026plusmn;\u0026thinsp;1.5 for SAW and 19\u0026thinsp;\u0026plusmn;\u0026thinsp;3 for SAW-T, while Type 1 steel welds show 20\u0026thinsp;\u0026plusmn;\u0026thinsp;1 for SAW and 15.5\u0026thinsp;\u0026plusmn;\u0026thinsp;0.5 for SAW-T.\u003c/p\u003e \u003cp\u003eIn Type 1 steel welds, Niobium carbonitrides are stable at lower temperatures in austenite but dissolved at higher temperatures [\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e]. Niobium carbonitrides can readily precipitate in austenite under deformation (strain-induced precipitation), and these particles impede grain growth and even recrystallization of austenite. The deformed austenite structure transforms into acicular ferrite due to intra granular nucleation of precipitates. This increase in acicular ferrite fraction leads to higher tensile strength in the case of Type 1 than in Type 2 steels. Also, Niobium efficiently locks dislocations, reducing their mobility and increasing the tensile strength of the welds.\u003c/p\u003e \u003cp\u003eType 1 steel welds experience failure near the HAZ, whereas Type 2 steel welds fail in the base metal. In Type 1 steels, a minimal addition of 0.023% Niobium effectively inhibits ferrite nucleation at prior austenite grain boundaries, thereby enhancing the volume fraction of martensite or bainite. Dissolved Niobium reduces ferrite nucleation and growth rates during cooling, leading to the formation of bainite/martensite microstructure and failure near the HAZ. Conversely, Type 2 steels, micro-alloyed with vanadium, exhibit vanadium atoms associated with carbon and nitrogen atoms, segregating to austenite grain boundaries at low austenite temperatures. This inhibits grain boundary nucleation of non-martensite transformation products, increasing strength, and causing the weld to fail away from the HAZ.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig15\" class=\"InternalRef\"\u003e15\u003c/span\u003e depicts the effect of welding conditions on the Charpy impact toughness properties at temperatures of 25\u0026deg;C and \u0026minus;\u0026thinsp;20\u0026deg;C for Type 1 and Type 2 steel weld joints. In Fig.\u0026nbsp;\u003cspan refid=\"Fig15\" class=\"InternalRef\"\u003e15\u003c/span\u003e(a), it is evident that Type 2 steel welds exhibit greater toughness than Type 1 steel welds. Specifically, Type 2 steel welds demonstrate toughness values of 103\u0026thinsp;\u0026plusmn;\u0026thinsp;15 J with SAW and 99\u0026thinsp;\u0026plusmn;\u0026thinsp;9 J with SAW-T processes at a temperature of 25\u0026deg;C, which are higher than that of Type 1 steel welds at 79\u0026thinsp;\u0026plusmn;\u0026thinsp;13 J with SAW and 93\u0026thinsp;\u0026plusmn;\u0026thinsp;4 J with SAW-T. The higher percent elongation values in Type 2 steel welds correlate with the greater toughness observed in these welds.\u003c/p\u003e \u003cp\u003eThe main reason for the deterioration in impact toughness in the case of Type 1 steel welds is heterogeneous precipitation, with coarse ferrite grains contributing to embrittlement by facilitating crack propagation. Figure\u0026nbsp;\u003cspan refid=\"Fig16\" class=\"InternalRef\"\u003e16\u003c/span\u003e shows the Niobium precipitates observed in the fracture surface close to the crack initiating site. In contrast, Type 2 steel welds with higher nitrogen content experience an increase in the chemical driving force for precipitation, resulting in enhanced toughness. In Type 2 steel welds, the HAZ toughness exceeds the weld toughness. Vanadium also reduces bainitic colony size contributing to improved toughness [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. This Vanadium nitride precipitation leads to precipitation hardening, contributing to enhanced toughness.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eAt -20\u003csup\u003e0\u003c/sup\u003eC, the impact toughness values of weld joints are suppressed due to the formation of brittle phases. Type 2 steel welds show higher HAZ impact toughness due to the improved ductility as compared with Type 1 steels. The SAW-T welds show higher HAZ toughness than SAW welds. The Charpy impact properties of the type 2 steel maintained the toughness through grain refinement by promoting ferrite nucleation on Nitrogen rich Vanadium carbonitrides co-precipitated on MnS inclusions as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig17\" class=\"InternalRef\"\u003e17\u003c/span\u003e. Several researchers reported that Vanadium carbide nanometer-sized carbides can significantly improve the toughness properties of conventional ferritic steel [\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e].\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e"},{"header":"4. Conclusion","content":"\u003cp\u003eThe present study extensively investigates the use of SAW and SAW-T processes for Type 1 and Type 2 steel butt joints made of ASTM A572 Gr. 50 steel. The key observations and findings of the study are summarized as follows:\u003c/p\u003e \u003cp\u003e \u003col\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eIrrespective of the material being used in the present study, the SAW-T process exhibits increased weld width and top reinforcement due to the concentrated trail electrode arc on the lead wire molten pool.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eType 1 steel welds, enriched with Niobium, exhibit superior mechanical properties compared to Type 2 steel welds including higher yield strength (\u0026cong; 7.9% higher) and ultimate tensile strength (\u0026cong; 4.8% higher) for both SAW and SAW-T processes. Furthermore, when comparing SAW-T to SAW, there is a noticeable increase in yield strength of 3.6% and ultimate tensile strength of 1.8%. These improvements are attributed to the development of acicular ferrite and the efficient dislocation locking mechanism facilitated by Niobium.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eAt the given heat input, the SAW-T process influences the impact toughness properties at both 25 \u003csup\u003e0\u003c/sup\u003eC and \u0026minus;\u0026thinsp;20\u003csup\u003e0\u003c/sup\u003eC for both steels. However, Type 2 steel welds show 30% higher impact toughness than Type 1 steels because the Vanadium carbides/ nitride precipitation leads to precipitation hardening contributing to enhanced toughness at 25\u003csup\u003e0\u003c/sup\u003e C. At -20\u003csup\u003e0\u003c/sup\u003e C, Type 2 steel welds show higher HAZ toughness due to improved ductility as compared with Type 1 steels.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eType 1 SAW-T steel welds exhibit a 5.74% higher hardness compared to SAW, whereas Type 2 SAW steel welds show a minor 0.5% increase in hardness compared with SAW-T. In the HAZ, Type 1 SAW-T welds display a 3.3% higher hardness than SAW, while Type 2 SAW welds demonstrate a 4.3% higher hardness compared with SAW-T. SAW-T welds exhibit slightly higher microhardness in both weld and HAZ compared to SAW welds, due to differences in cooling rates and deposition rates. The higher hardness in Type 1 steel welds is attributed to the formation of Niobium carbides/ nitride and Titanium nitride.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003c/ol\u003e \u003c/p\u003e \u003cp\u003eThis research offers significant insights into how the SAW-T process impacts both the metallurgical and mechanical properties of welds compared to traditional SAW methods. It advocates the adoption of the SAW-T process over conventional SAW techniques specifically for welding 8 mm thick ASTM A572 Gr. 50 steels.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eFunding -\u0026nbsp;\u003c/strong\u003eThis work was supported by TATA Steel Ltd. Jamshedpur, India (Grant Number IC2223MEE003TSLXDEGA). Degala Venkata Kiran has received research support from this grant.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting Interests\u003c/strong\u003e The authors declare no competing interests.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor contribution -\u0026nbsp;\u003c/strong\u003eAdapa Mahanth Kumar: conceptualization, methodology, investigation, validation, formal analysis, writing\u0026mdash;original draft, visualization; Polamuri Sudheer Kumar\u003cstrong\u003e:\u003c/strong\u003e conceptualization, writing\u0026mdash;review and editing, supervision, validation; Perka Ashok Kumar: conceptualization, writing\u0026mdash;review and editing, resources, visualization, validation, funding acquisition; Degala Venkata Kiran: conceptualization, methodology, investigation, formal analysis, resources, supervision, writing\u0026mdash;review and editing, visualization, project administration, and funding acquisition. Kanwer Singh Arora: conceptualization, writing\u0026mdash;review and editing, resources; Nasina Venkaiah:conceptualization, methodology, investigation, formal analysis, resources, supervision, writing\u0026mdash;review and editing, visualization, funding acquisition.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthics approval -\u003c/strong\u003e Not applicable\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent to participate -\u003c/strong\u003e Not applicable\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication -\u003c/strong\u003e Not applicable\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConflict of interests -\u003c/strong\u003e The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgment\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors would like to thank Joining and Metallography Laboratory, Department of Mechanical Engineering, IIT Tirupati, for experimental work support. Materials Welding \u0026amp; Joining Group, R\u0026amp;D, TATA Steel Limited, Jamshedpur is also acknowledged for metallography and mechanical characterization work.\u0026nbsp;\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eNajafi H, Rassizadehghani J, Asgari S (2008) As-cast mechanical properties of vanadium/niobium microalloyed steels. Mater Sci Eng A 486:1\u0026ndash;7. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.msea.2007.08.057\u003c/span\u003e\u003cspan address=\"10.1016/j.msea.2007.08.057\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLi Y, Crowther DN, Green MJW, Mitchell PS, Baker TN (2001) The Effect of Vanadium and Niobium on the Properties and Microstructure of the Intercritically Reheated Coarse Grained Heat Affected Zone in Low Carbon Microalloyed Steels. 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Metallomics 7:730\u0026ndash;742. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1039/c4mt00304g\u003c/span\u003e\u003cspan address=\"10.1039/c4mt00304g\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":true,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"the-international-journal-of-advanced-manufacturing-technology","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"jamt","sideBox":"Learn more about [The International Journal of Advanced Manufacturing Technology](https://www.springer.com/journal/170)","snPcode":"170","submissionUrl":"https://submission.nature.com/new-submission/170/3","title":"The International Journal of Advanced Manufacturing Technology","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Tandem submerged arc welding, ASTM A572 Gr.50 steel, Alternating current, Balance, Offset, Flux Copper backing","lastPublishedDoi":"10.21203/rs.3.rs-4398172/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4398172/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eSquare butt joints were prepared using two different materials, Niobium (Type 1) and Vanadium (Type 2) micro-alloyed ASTM A 572 Gr.50 steels, employing both single wire submerged arc welding (SAW) and two-wire tandem submerged arc welding (SAW-T) processes, with a constant heat input per unit length of 2.5 kJ/mm maintained throughout the study. The weld profile, microstructure, and mechanical properties were analyzed for SAW and SAW-T processes. It was observed that the weld width, hardness, yield strength, ultimate tensile strength, and impact toughness of the welds increased with SAW-T compared to SAW. Furthermore, a comparison was made between the two types of steel weld joints. Type 1 steel weld exhibited higher acicular ferrite, yield strength, and ultimate tensile strength due to the intra-granular nucleation of Niobium carbonitrides in austenite. In contrast, Type 2 steels displayed a higher percentage of elongation, hardness, and impact toughness at 25\u0026deg;C. At -20\u0026deg;C temperature, SAW-T welds show higher HAZ toughness than SAW welds. Also, Type 2 welds showed enhanced toughness in comparison to Type 1 welds by mitigating the pinning effect of precipitates.\u003c/p\u003e","manuscriptTitle":"Influence of single and tandem-submerged Arc Welding on ASTM A572 Gr.50 steels","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-07-12 03:14:37","doi":"10.21203/rs.3.rs-4398172/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"reviewerAgreed","content":"","date":"2024-07-01T12:23:01+00:00","index":0,"fulltext":""},{"type":"reviewersInvited","content":"","date":"2024-06-21T14:06:53+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2024-06-20T13:10:18+00:00","index":"","fulltext":""},{"type":"submitted","content":"The International Journal of Advanced Manufacturing Technology","date":"2024-06-19T02:18:34+00:00","index":"","fulltext":""},{"type":"decision","content":"Major Revisions Needed","date":"2024-06-09T03:39:36+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"the-international-journal-of-advanced-manufacturing-technology","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"jamt","sideBox":"Learn more about [The International Journal of Advanced Manufacturing Technology](https://www.springer.com/journal/170)","snPcode":"170","submissionUrl":"https://submission.nature.com/new-submission/170/3","title":"The International Journal of Advanced Manufacturing Technology","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"f8db18cb-ca0c-4a95-b862-f3825aa42bbd","owner":[],"postedDate":"July 12th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2024-10-07T16:07:49+00:00","versionOfRecord":{"articleIdentity":"rs-4398172","link":"https://doi.org/10.1007/s00170-024-14567-8","journal":{"identity":"the-international-journal-of-advanced-manufacturing-technology","isVorOnly":false,"title":"The International Journal of Advanced Manufacturing Technology"},"publishedOn":"2024-10-01 15:56:52","publishedOnDateReadable":"October 1st, 2024"},"versionCreatedAt":"2024-07-12 03:14:37","video":"","vorDoi":"10.1007/s00170-024-14567-8","vorDoiUrl":"https://doi.org/10.1007/s00170-024-14567-8","workflowStages":[]},"version":"v1","identity":"rs-4398172","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4398172","identity":"rs-4398172","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}