Effect of Cr content on microstructure, mechanical properties and corrosion behavior of weld metal in weathering steel of high-speed train bogie

Effect of Cr content on microstructure, mechanical properties and corrosion behavior of weld metal in weathering steel of high-speed train bogie | 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 Effect of Cr content on microstructure, mechanical properties and corrosion behavior of weld metal in weathering steel of high-speed train bogie Gaojian Wang, Dean Deng, Dandan Kang, Yanhong Ye This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4744193/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 5 You are reading this latest preprint version Abstract The effects of Cr content on the microstructure, mechanical properties and corrosion behavior of two weld metals containing Ti or Mo in the Ni-Cu alloy system for high-speed train bogies were studied. The results show that: In the weld containing Ti, Cr increases the acicular ferrite by about 15%, decreases the GF and FS, and slightly increases the M-A constituents. the effect of Cr on toughness is not obvious. In the weld containing Mo, Cr almost did not change the acicular ferrite content, resulted in a decrease in GF and an increase in FS, and a substantial increase in M-A constituents in the as-welded zone (0.4–2.5%). Cr reduces weld toughness due to increase the proportion and size of M-A constituents and coarsen inclusions, the impact energy at -40℃ and − 60℃ decreases by 44J and 16J respectively. For the corrosion resistance, the initial corrosion rate of Mo-containing welds is reduced by addition of Cr, mainly due to the formation of MnS on the inclusions, which absorbs Cr, is suppressed, MnS is easily dissolved. While in Ti-containing weld this effect is weakened. In addition, Cr densifies the inner and outer rust layers and then reduces the corrosion rate of weld rust layers. high-speed train weathering steel corrosion resistance toughness Cr weld metal Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 1 Introduction China's high-speed trains have developed from the CRH1 series with a speed of 200km/ h to the CRH380AM ( CIT500 high-speed test train) with a maximum test speed of over 500km/h [ 1 ] and the CRH380BG high-cold EMU [ 2 ] for extreme harsh environments. With the continuous increase of train operating speeds and the higher demand for resistance to high cold and sandstorm, the train structure exhibits more complex dynamic load behavior. At the same time, the harsher service environment (with temperatures − 40℃ or even lower) places more stringent requirements on the low temperature toughness and weather resistance of materials and welds. The bogie frame, as one of the key load-bearing and force-transmitting components, plays a crucial role in ensuring operational safety [ 3 ]. Therefore, the safety of train operation is vital issues in the technological development of high-speed trains. Due to the inhomogeneity of its composition, structure and mechanical properties, and the existence of high residual stress, the weld is often the weakest part of the structure [ 4 ]. Thus, the high requirements for low-temperature toughness and weather resistance of the weld metal in high-speed train bogies pose a significant challenge. As we all know, Cr is a ferrite stabilizing element, which has been widely used in weld metal to improve strength and corrosion resistance [ 5 ]. In recent years, many researchers have studied the effect of Cr on the microstructure and mechanical properties of high-strength steel weld metal, and generally found that the increase of Cr in the weld will lead to the increase of yield strength and tensile strength [ 6 – 9 ], but there is no general consensus in other aspects. In terms of toughness, some studies have shown that increasing Cr can reduce toughness. For example, Surian E et al. [ 6 ] found that the chromium in the weld metal of 2Ni-Cr-0.35Mo alloy system is in the range of 0.04 ~ 1.82%, which is harmful to toughness. Evans GM [ 7 ] found that increasing Cr in C-Mn steel welds ranged from 0 to 2.34% would lead to a decrease in toughness, especially when the Cr exceeded 1%. Studies have also found that when Cr content is in a small amount, it is beneficial to toughness, such as Jorge J F et al. [ 10 ] found that when Cr < 0.5% in C-Mn welds the toughness was slightly improved. Snieder G et al. [ 11 ] found that in the low-alloy high-strength steel welds containing Mo, Nb, Ti and B, when Cr < 0.73%, the weld toughness is sometimes beneficial. CAI Yangchuan et al. [ 8 ] believed that in Ni-Cr-Mo-V welds, when Cr < 1.2%, the toughness of weld metal gradually increases with the increase of Cr content. Avazkonandeh et al [ 9 ] found that in Ni-Cr-Cu-Ti-low Mn welds, the impact toughness increases monotonously when 0.05–0.91% Cr was added. Lee H [ 12 ] found that in the 2Ni-Cr-0.4Mo weld, the toughness is gradually improved by adding Cr 0.02 ~ 0.44%. In terms of corrosion, it was generally believed that [ 12 – 15 ] Cr is significantly enriched in the rust layer, which makes the rust layer denser, reduces the current density during the anodic dissolution reaction, and then improves the corrosion resistance of the deposited metal. However, some scholars hold different views. For example, Sun B et al. [ 16 ] believed that when Cr is 1–4%, the corrosion rate is high. Feng Hui et al. [ 17 ] found that the addition of Cr alone has little effect on the corrosion resistance. It can be seen that the influence of Cr on the toughness and corrosion resistance of steel weld metals under different alloy systems has not been uniform, and the influence of Cr on the properties of steel weld metals containing Ti or Mo in the Ni-Cu alloy system for high-speed train bogies is rarely studied. Therefore, this study aims to investigate the effects of Cr content on the microstructure, mechanical properties and corrosion behavior of steel weld metals containing Ti or Mo in the Ni-Cu alloy system of high-speed train bogies using optical and scanning electron microscopy, mechanical tests, cyclic immersion corrosion tests, and electrochemical tests, revealing its influence mechanism and internal relationship, providing technical support for the development of welding consumables that meet the high requirements of low-temperature toughness and weather resistance for weld metals of high-speed train bogies. 2 Test Method In the study, four kinds of welding wires with different Cr content, 1.2mm in diameter, were independently designed as research materials. The weld metals were prepared according to ISO 14341 for mechanical tests, and 6 ~ 8 layers of deposited metal were cladded on the substrate for corrosion tests. GMA Welding was done in the flat position with Ar + 20%CO2 shielding gas. The process conditions were current: 250 A, voltage: 28 V, average travel speed: 26cm/min. The interpass temperature was held at less than 200°C. Table 1 showed the chemical compositions of weld metals. Table 1 Chemical composition of weld metals (wt. %) No. C Si Mn Cr Mo Ni Cu Ti 0CrTi 0.053 0.40 1.00 - - 0.82 0.35 0.030 0.3CrTi 0.045 0.51 1.09 0.32 - 0.60 0.38 0.036 0CrMo 0.055 0.37 0.92 - 0.04 0.85 0.33 - 0.3CrMo 0.036 0.36 1.04 0.37 0.02 0.87 0.37 - Tensile tests were conducted using a computer-controlled universal testing machine (CMT5305) according to ISO 5178. Impact tests were performed using a JBW-500B pendulum impact testing machine following ISO 9016. Corrosion performance tests included cyclic immersion corrosion tests and electrochemical analysis. Corrosion resistance tests were conducted based on TB/T 2375-93 for a duration of 72 hours to measure the corrosion rate of the deposited metal. Electrochemical corrosion analysis was performed using a Princeton Applied Research (PAR) 273A electrochemical workstation. The test samples included specimens without cyclic immersion corrosion and those subjected to 72 hours of cyclic immersion corrosion. The working surface of the samples to be exposed was 10mm × 10mm, while the remaining parts were encapsulated with epoxy resin. The samples were polished and then subjected to electrochemical measurements. The corrosion medium used was 0.01 mol/L NaHSO3. The scanning potential for polarization curves ranged from − 0.25V to 0.25V at a scanning rate of 0.5 mV/s. The frequency response for impedance spectroscopy was set at 100 kHz to 10 MHz, with an amplitude of 10 mV. The test data was fitted using CVIEW and ZView software. The rust layer morphology and micro-area composition after cyclic immersion were analyzed using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). Metallographic specimens were cut perpendicular to the welding direction and prepared according to standard metallographic methods, polished and etched with 3% nital solution. Metallographic examination is carried out by optical microscope ( OM ). Micrographs taken at 500 magnifications were evaluated using the point-counting method for the proportion of microstructural components in the columnar region and the grain size in the reheated zone, following ASTM E562-2011 and ASTM E112. 10 fields were examined, and a 10×10 grid was used for point counting to ensure a minimum of 1000 points. SEM was used to observe the M-A constituents and inclusions in the weld metals at a magnification of ×2000. 10 random fields were selected in the columnar region, and 5 random fields were selected in the reheated zone. IPP software was used for quantitative analysis of the proportion, size, and characteristics of M-A constituents and inclusions. EDX was used for element mapping and line scan analysis to identify the composition of inclusions and M-A constituents. Impact fracture analysis was performed using SEM. fibrous zone, radial zone and shear lip zone were identified at low magnification, and the proportions of each zone were statistically analyzed using IPP. Micromorphology of impact fracture was observed at 1000 magnification. 3 Results 3.1 Microstructure of Weld Metals 3.1.1 Microstructure of as-welded zone The microstructures of as-welded zones in weld metals with different Cr contents are shown in Fig. 1. Table 2 presents the volume fractions of different microstructures, and Table 3 lists the quantitative results of M-A constituents. The microstructures of weld metals are mainly composed of primary ferrite (PF), ferrite with second phase (FS), acicular ferrite (AF), and M-A constituents (MA). The MA that consists of the mixture of martensite and austenite forms by the martensite transformation of the austenite enriched in C at lower temperatures [ 18 ]. The formation of MA is affected by welding cooling speed as well as chemical composition, and white island particles in SEM images are identified as MA [ 19 , 20 ]. Table 2 Quantitative proportion of microstructure in columnar zone of weld metal with different Cr content No. R mico /% PF AF FS 0CrTi 52.3 ± 5.64 40.05 ± 5.81 7.65 ± 1.8 0.3CrTi 39.8 ± 5.31 55.5 ± 5.98 4.7 ± 1.22 0CrMo 74.6 ± 5.67 20.9 ± 5.23 4.5 ± 1.02 0.3CrMo 70.5 ± 6.22 19 ± 6.11 10.5 ± 2.08 Note: R mico — ratio of microstructures, PF — primary ferrite, AF — aciular ferrite, FS — ferrite with second phases From Fig. 1 and Table 2 , It can be seen that compared with 0CrTi, in the 0.3CrTi weld, which is the Ti-containing weld added by 0.3% Cr, the microstructure is dominated by AF, AF is increased by 15%, both grain boundary ferrite and FS are decreased, the size of AF is significantly reduced, and the dendrite spacing does not change much, but the width of ferrite side-plate tends to decrease. Compared with 0CrMo, in the 0.3CrMo weld, which is the Mo-containing weld added by 0.3% Cr, the microstructure is dominated by PF, the AF does not change much, grain boundary ferrite is decreased, FS is increased, the width of AF does not change much, and the width of columnar grains is reduced slightly. It can be considered that Cr has different effects on microstructure in welds with different components. Table 3 Quantitative proportion of MA in columnar zone of weld metals No. Aavg / µm2 _ _ _ R a /% 0CrTi 0.3 0.1 0.3CrTi 0.21 0.6 0CrMo 0.25 0.4 0.3CrMo 0.41 2.5 Note: A avg — average area of MA, R a — area ratio of MA From Fig. 1 and Table 3 , it can be observed that the MA in each weld are mainly blocky. With the addition of Cr, the proportion of MA increases, the increment is greater in the weld containing Mo, from 0.4–2.5%. For the size of MA, it decreases slightly in the weld containing Ti, but it increases significantly in the welds containing Mo. Table 4 Inclusions in weld metals No. T i /ea RR i / µ m MR i / µ m D i /ea/mm T ni /ea T ni /ea RR ni / µ m 0CrTi 322 0.11 ~ 0.54 0.24 11332 69 0.14 ~ 0.54 0.3 0.3CrTi 231 0.11 ~ 0.47 0.22 8129 28 0.17 ~ 0.43 0.27 0CrMo 251 0.14 ~ 0.63 0.28 8833 46 0.21 ~ 0.58 0.35 0.3CrMo 326 0.11 ~ 0.84 0.23 11472 15 0.16 ~ 0.84 0.36 Note: T i — total number of inclusions, RR i — radius range of inclusions, MR i — mean radius of inclusions, D i — Density of inclusions, T ni — Total number of nucleation inclusions, RR ni — radius range of nucleation inclusions, MR ni — mean radius of inclusions nucleation radius Table 4 shows the quantitative results of inclusions examined by SEM. Cr reduces the nucleation rate of inclusions and the average size of inclusions in both welds. The influence of Cr on the inclusion density is different in the two types of welds. The inclusion density is reduced in the Ti-containing welds, but increased in the Mo-containing welds. The composition of the inclusions was further analyzed. As can be seen from Table 5 , the composition of the inclusions includes (Mn, Al, Si)Ox, FeOx, TiOx, CuS, etc. Compared with 0CrTi and 0.3CrTi, the latter has lower MnOx, SiOx, and TiOx, which means it is probably related to the low oxygen content of the 0.3CrTi weld. The higher the oxygen content, the more Mn and Si are consumed, and the more Mn and Si oxides are produced [ 21 ]. Comparing the two types of welds, it is found that Cr was presence in the inclusions of the welds adding Cr (0.3CrTi and 0.3CrMo), and the Cu was decreased at the same time, which may be due to the absorption of Cr by inclusions [ 22 ] and the formation of CrS with S, while the content of CuS was reduced. Table 5 Composition of inclusions in weld metals (wt. %) No. O Al Si S Ti Cr Mn Fe Cu 0CrTi 14.76 0.77 1.62 0.69 5.01 - 4.14 70.37 1.10 0.3CrTi 15.71 0.97 1.89 0.77 5.86 0.4 4.45 68.73 1.24 0CrMo 17.51 0.87 6.16 1.07 - - 7.77 65.91 0.71 0.3CrMo 22.65 0.79 7.15 0.83 - 0.33 8.78 58.98 0.67 3.1.2 Microstructure of reheat zone The microstructures of the reheated zones in weld metals are shown in Fig. 2. The columnar grains transformed into equiaxed ferrite grains due to the reheating effect of the subsequent weld bead. The statistical results of the grain size and MA constituent in the reheating zone are shown in Table 6 . The grain size of the reheat zone of all welds in this study is small, and the addition of Cr has little effect on it. It tends to increase in the welds containing Ti, while it tends to decrease in the welds containing Mo. MA in the reheat zone of each weld are blocky, and their number are increased significantly with the addition of Cr. Moreover, the size of MA in the weld containing Mo are increased by the effect of Cr. Table 6 Quantitative analysis of grain size and MA in reheating zone of weld metals No. S g Aavg / µm2 _ _ _ R a /% 0CrTi 10.54 ± 0.11 0.12 0.06 0.3CrTi 10.11 ± 0.37 0.25 0.5 0CrMo 10.26 ± 0.21 0.18 0.1 0.3CrMo 10.46 ± 0.34 0.26 0.5 Note: S g — grain size, A avg — average area of MA, R a — area ratio of MA 3.2 Analysis of mechanical properties The effects of Cr on the tensile properties and impact toughness of weld metals are shown in Table 7 . With the addition of 0.3% Cr, the yield strength and tensile strength in both Ti and Mo-containing welds are increased, which may be related to the solution strengthening effect of Cr, the increase of AF and the refinement of microstructures. The toughness of both Ti and Mo-containing welds are reduced by the addition of Cr. Compared with 0.3CrTi and 0CrTi, the impact energy at -40℃ and − 60℃ in the weld containing Ti are reduced by 30J and 49J, respectively. And compared with 0.3CrMo and 0CrMo, the impact energy at -40℃ and − 60℃ in the weld containing Mo are reduced by 44J and 16J, respectively. Table 7 Effect of Cr on tensile properties and impact toughness of weld metals No. R m /MPa R eL /MPa A/% KV 2 (-40℃)/J KV 2 (-60℃)/J 0CrTi 574 492 26.5 159 118 0.3CrTi 700 636 26 129 69 0CrMo 559 463 27.5 149 78 0.3CrMo 575 488 28 105 62 3.3Analysis of corrosion resistance 3.3.1 Result and analysis of 72h immersion corrosion test The results of the 72h immersion accelerated corrosion test of weld metals are shown in Table 8 . It can be seen that, Cr has little effect on the initial corrosion rate of the Ti-containing weld, but Cr makes the initial corrosion rate of the Mo-containing weld decreased from 1.745g·mm − 2 ·h − 1 to 1.642g·mm − 2 ·h − 1 , indicating the beneficial effect of Cr on the corrosion resistance of the Mo-containing weld. Table 8 72h immersion corrosion performance of weld metals with different Cr No. CR/g mm −2 h −1 R wl /% 0CrTi 1.646 1.35 0.3CrTi 1.669 1.37 0CrMo 1.745 1.44 0.3CrMo 1.642 1.35 Note: CR —corrosion rate, R wl —corrosion weight loss ratio 3.3.2 Results and Analysis of Electrochemical test Figure 3 shows the potentiodynamic polarization curves of weld metals with different Cr. The corrosion potential and corrosion current density were obtained through Tafel fitting of the potentiodynamic polarization curves. Figure 4 presents the impedance spectra of weld metals with different Cr. The fitted corrosion potential, corrosion current density, and impedance results are shown in Table 9 . Table 9 Fitting results of electrochemical tests for samples with different Cr No. E corr /mV Icorr / µA·cm −2 R/Ω·cm2 Raw 72h Raw 72h Raw 72h 0CrTi -1405 -920 75.38 53.59 247 245 0.3CrTi -1437 -1090 62.77 46.95 290 377 0CrMo -1261 -972 95.65 43.9 215 195 0.3CrMo -1223 -1112 65.19 49.33 218 206 Note: E corr — self-etching potential, I corr — self-etching current density, R — resistance From the fitting results, it can be observed that the corrosion potential of the samples immersed for 72h has shifted positively compared to the original samples, indicating that the presence of rust layer on the surface of the weld metals impedes the electrochemical anodic dissolution of the weld matrix. In the two types of welds, Cr has little effect on the corrosion potential of the original sample, and has a negative shift on the corrosion potential of the immersion for 72h, indicating that Cr almost does not affect the corrosion tendency of the matrix, but increases the corrosion tendency of the rust layers. In the weld containing Ti, Cr has a slight effect on the corrosion current density and resistance of the original sample. For the sample after 72h of cyclic immersion, Cr significantly reduces the corrosion current density and increases the resistance of the rust layer. This indicates that in the Ti-containing weld, Cr has no significant effect on the initial corrosion rate, but plays a positive role in reducing the corrosion rate of the rust layer. In the weld containing Mo, Cr reduces the corrosion current density of the original sample, and slightly increases the resistance of the rust layer. For the samples immersed for 72h, the corrosion current density and the resistance of the rust layer have little change, which indicates that Cr in the Mo-containing weld is beneficial to the initial corrosion of the weld, but has no obvious effect on the later corrosion. 4 Discussions 4.1 Effect of Cr on microstructure of weld metals It is well known that Cr is a ferrite stabilizing element [ 23 ]. From the comparison of the Fe-Cr phase diagram [ 24 ] and the CCT curves of Si-0.2 and Cr-0.5 welds given in the literature [ 25 ], it can be seen that when a trace amount of Cr is added, the phase field moves downward, the A3 temperature is slightly reduced, the initial ferrite temperature is reduced, but the ferrite end temperature is almost unchanged. According to the Ms equation [ 26 ] and combined with the CCT curve, the starting temperature of the martensitic transformation is slightly lowered with the addition of 0.3% Cr, and the ending temperature is reduced more significantly. Cr reduces the initial transformation temperature of ferrite, that is, reduces the transformation driving force that preferentially forms ferrite, which leads to the decrease number and size of PF in 0.3CrTi and 0.3CrMo welds. In the welds containing Ti, the Ti oxide formed is the most effective inclusion for AF nucleation [ 27 ]. While Cr reduces PF, it provides more space for Ti oxide to induce acicular ferrite nucleation and growth, which leads to the increase of AF in the 0.3CrTi weld. Although the number of AF-nucleated inclusions in 0.3CrTi decreases, it still does not affect the increase of AF, because AF can be promoted by autocatalytic nucleation on the already formed AF [ 28 ], as shown in FIG. 5, sympathetic nucleation was found in both 0CrTi and 0.3CrTi welds. In the Mo-containing weld, it lacks effective AF-nucleated inclusions, and AF has no advantage in competitive growth with FS [ 29 ]. The decrease of PF provides space for the growth of FS, which explains that AF does not change, but FS increases in the 0.3CrMo weld. In the reheat zone, Cr can slightly reduce the temperature of Ac3, which increases the high temperature residence time of austenitizing and then slightly coarsens the grains. However, it is also restrained by the pinning effect of inclusions [ 30 ]. From Table 7 and Table 9 , It can be seen that the correlation between the inclusion density and the grain size of the reheat zone shows that, compared with the weld without Cr, the change of the grain size in the reheat zone of the weld with Cr is negatively correlated with the change of the inclusion density, indicating that the inclusion is the key to the influence of the grain size. MA are formed from untransformed austenite during the cooling process, and a lower content of residual austenite above the Ms temperature reduces the presence of MA [ 31 ]. As mentioned above, Cr reduces the starting temperature of the transition to ferrite, while hardly changing the end temperature of the transition to ferrite, which results in insufficient transition to ferrite, leaving more residual austenite. Cr can slightly lower the Ms temperature, but more significantly lower the Mf temperature, which provides more time for the transition of residual austenite to martensite, and then more MA are formed, which explains the large increase in MA of 0.3CrMo compared to 0CrMo. However, in 0.3CrTi, compared with 0CrTi, the increment of MA is less, because the nucleation AF induced by the inclusion containing Ti can promote the ferrite transformation sufficiently. 4.2 Effect of Cr on the toughness of weld metals The role of Cr in the microstructure, MA, and inclusions of weld metal is a crucial factor affecting impact toughness. AF, due to its fine grain size and interlocking structure with high angle boundaries, acts as an obstacle to crack propagation, thereby enhancing the toughness of weld metal [ 32 ]. In welds containing Ti, Cr increases the AF in the welded zone but decreases the toughness. It has been pointed out that the optimal microstructure of weld metals requires high AF, but not the highest level of AF content [ 33 ]. One of the reasons for the decrease in toughness may be that the grain size of the reheat zone in the 0.3CrTi weld is coarsened. At the same time, the toughness of ferrite matrix in 0.3CrTi weld is reduced by the low Ni content. In the Mo-containing weld, Cr almost did not change the AF content, and the grain size of the reheat zone was refined, so the toughness should be increased but decreased, indicating that the reduction of toughness was affected by other factors. MA are essential factors controlling toughness [ 9 ], and embrittlement cracking of MA or debonding of M-A from the matrix initiates cleavage fracture [ 34 ]. There is a direct relationship between impact toughness and MA, the impact toughness decreased with an increase in MA [ 10 ]. For the welds containing Ti and Mo, whether in the as-welded zone or the reheat zone, Cr increases the content and size of MA, especially in the welds containing Mo, which may be the main reason for the reduction of weld toughness caused by Cr. This is consistent with the conclusions of Evans G M[ 7 ] and Snieder G et al. [ 11 ]. However, in the weld containing Ti, the MA increased by Cr is not large, and its reduction in toughness is limited. Furthermore, the influence of inclusions on the mechanical properties of weld metal is two-sided. Lan L et al. [ 35 ] suggests that when inclusions exceed 1 µm, they tend to act as nucleation sites for cleavage cracks due to their lower local fracture stress. In this study, for the Ti-containing weld, Cr has little effect on the inclusion size, which is less than 1µm. In the Mo-containing weld, Cr increases the maximum inclusion size from 1.2µm to 1.7µm, which may lead to a decrease in toughness. As Cr is a strong carbide, Chen J H et al. [ 36 , 37 ] found that carbide particles may lead to crack initiation. However, according to literature [ 38 ], Cr carbides will not be deposited in the weld of low-alloy high-strength steel containing less than 4% Cr. In this study, due to the small Cr content, no Cr carbides were observed. In short, Cr reduces the toughness of weld metals due to increase the number and size of MA as well as coarsen inclusions. For the Ti-containing weld, this effect of Cr is not obvious. In order to further study, the weld toughness, the microscopic characterization of the impact fracture of the weld metal was carried out, as shown in SEM micrographs in Fig. 8. Their fracture modes are a combination of brittle and ductile fracture. The fracture surfaces can be divided into three zones: fibrous zone, radial zone, and shear lip zone, the energy absorbed for fibrous zone and shear lip zone formation account mostly for the total CVN energy. Table 10 presents the proportions of each zone. Compared with 0.3CrMo and 0CrMo, Cr reduces the sum of the proportion of fibrous zone and shear lip zone, and the brittle fracture region increases, which leads to the increase of cleavage surface and the decrease of absorbed energy. This is consistent with the toughness results. However, compared with 0CrTi, in the 0.3CrTi weld, the radial zone does not increase, which also indicates that the main reason affecting its toughness is that Ni reduces the toughness of the ferritic matrix [ 39 ]. As can be seen from Fig. 6, compared with 0CrTi, the dimples in the ductile fracture zone of 0.3CrTi weld are shallower. Compared with 0CrMo, the cleavage surface of brittle fracture zone in 0.3CrMo welds increased. These confirmed that the reduction in toughness of the two Cr-adding welds. Table 10 Proportion of impact fracture area weld metals with different Cr No. FZ/% SZ/% RZ/% 0CrTi 32 39 29 0.3CrTi 26 48 26 0CrMo 18 72 10 0.3CrMo 33 30 37 Note: FZ — fibrous zone, SZ — Shear lip zone, RZ — radial zone 4.3 Effect of Cr on corrosion resistance The fracture morphology of the rust layer after immersion corrosion for 72 h is shown in Fig. 8. The corrosion rust layer is divided into an inner rust layer and an outer rust layer. The alloying elements act mainly through their influence on the inner rust layer[ 40 ]. The formation of the inner rust layer occurs in the initial stage of corrosion, including local corrosion initiation and local corrosion expansion [ 41 ]. Further, the outer rust layer is formed on the inner rust layer, providing long-term corrosion resistance against the environment. AF has good corrosion resistance, which provides less contact with corrosive media areas [ 18 , 42 ]. In addition, the increase of MA will reduce the corrosion potential and then promote the local corrosion [ 18 ]. Compared with 0CrTi, in 0.3CrTi welds, the positive effect of a large increase of AF on corrosion resistance and the negative effect of the increase of MA offset each other, indicating that the initial corrosion rate changes little. Compared with 0CrMo, the corrosion resistance in 0.3CrMo welds should be adversely affected by the significant increase of MA, but in fact which is beneficial to the initial corrosion. This contradiction cannot be explained by AF and MA. The corrosion resistance of inclusions is much lower than that of the matrix [ 43 ]. Literature [ 41 , 44 ] has indicated that the corrosion process originates from local pitting that occurs at active sites (especially inclusions), which then expands into uneven general corrosion through the extension and merging of small pitting nuclei. As mentioned above, Cr enables inclusion to adsorb Cr and form CrS, which reduces the adverse effect of MnS in inclusion on initial corrosion [ 45 ], which plays a dominant role in welds containing Mo. In the Ti-containing weld (0.3CrTi), TiO2 becomes the core of the inclusion and promotes Mn to form MnS on its surface, which counteracts the inhibition effect of Cr. From the cross section morphology of the rust layer given in Fig. 8, it can be seen that the addition of Cr in the two types of welds leads to Cr enrichment in the inner rust layer. As the crystalline core of the rust phase grains, Cr accelerates the α-FeOOH transformation and promotes the densification of the rust layer [ 46 ], and the outer rust layer grown from this dense inner rust layer is also relatively dense [ 40 ]. From FIG. 7 (a)(b), it can be seen that in the weld containing Ti, the addition of Cr changes the inner and outer rust layers of the weld from obviously loose (0CrTi) to dense (0.3CrTi). In 0.3CrTi welds, the cracks and holes in the outer rust layer are reduced, and the corrosion liquid absorbed by the outer rust layer to the substrate surface through the capillary effect is reduced, thus reducing the corrosion rate of the weld. This explains the great benefit of adding Cr to the weld containing Ti to reduce the corrosion rate of the rust layer. As can be seen from FIG. 7 (c)(d), in the weld containing Mo, Cr enrichment in the inner rust layer did not make the inner and outer rust layers denser. Literature [ 15 ] pointed out that Mo improved the corrosion resistance better than Cr. Compared with 0CrMo welds, the corrosion resistance damage caused by the low Mo content in 0.3CrMo welds counteracts the benefits of adding Cr. So Cr does not play its role in improving the corrosion resistance of welds in 0.3CrMo welds. 5 Conclusion The effect of adding 0.30% Cr content on the microstructure and properties of the weld metal containing Ti or Mo in the Ni-Cu alloy system for high-speed train bogies was studied, and the following conclusions were drawn: (1) When 0.3%Cr was added to the weld containing Ti, the AF content was increased by about 15%, both grain boundary ferrite and FS are decreased, and the microstructure was mainly AF. The number of MA increases slightly. The addition of 0.3%Cr in the weld containing Mo almost did not change the AF content, the grain boundary ferrite decreased and FS increased, the microstructure was dominated by PF, and the number of MA in the as-welded zone increased significantly (0.4–2.5%). (2) Cr reduces the toughness of welds by increasing number and size of M-A component as well as coarsening inclusions. the impact energy of -40℃ and − 60℃ in the weld containing Mo is reduced by 44J and 16J, respectively. In the weld containing Ti, this effect of Cr is not obvious. (3) Cr makes the inclusion adsorb Cr and inhibits the formation of soluble MnS, which is the main reason for the decrease of the initial corrosion rate of the welds containing Mo, while this effect is weakened in the welds containing Ti. Cr densifies the inner and outer rust layers and then reduces the corrosion rate of weld. Declarations Funding and Conflicts of interests This work was supported by Science and Technology Department of Sichuan Province (Grant numbers [2019ZDZX0017]). The authors have no competing interests to declare that are relevant to the content of this article. References Xu YG, Li Y (2020) Research on Technical Indexes of 400 km / h Wheel-Rail EMU for Chengdu-Chongqing Middle Line [J]. High speed Railway Technol 11(3):5 Xiang AF, Yu WL, Chen MG Cold-proof Technology on Traction Motor of High-cold CRH380B EMUs [J]. ELECTRIC DRIVE FOR LOCOMOTIVES, 2014(4):4 Wang BM (2014) EMU overall and bogie[M], 2nd edn. Southwest Jiaotong University, Chengdu, p 143 Tian Y (1991) Metallographic analysis of fracture in welding area[M]. China Machine, Beijing, p 109 Li Xiaogang Corrosion-resistant low-alloy structural steel [M]. 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Curr Opin Solid State Mater Sci 8(3–4):267–278 Koseki T, Thewlis G (2005) Overview Inclusion assisted microstructure control in C–Mn and low alloy steel welds[J]. Mater Sci Technol 21(8):867–879 White D (2018) Investigation of low oxygen HSLA steel weld metal[M]. Colorado School of Mines Matsuda F, IkeuchI K, Okada H et al (1994) Effect of MA Constituent on Fracture Behavior of 780 and 980MPa Class HSLA Steels Subjected to Weld HAZ Thermal Cycles. 23(2):231–238 (Materials, Metallurgy &Weldability)[J]. Transactions of JWRI Jorge JCF, de Souza LF, G, Mendes MC et al (2021) Microstructure characterization and its relationship with impact toughness of C–Mn and high strength low alloy steel weld metals–a review[J]. J Mater Res Technol 10:471–501 Zhang Z, Farrar RA (1997) Influence of Mn and Ni on the microstructure and toughness of C-Mn-Ni weld metals[J]. 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Effects of Alloying Elements on Transformation Behaviour for Synthetic Weld Heat-Affected Zone of Steels (IV) : Effect of Cr on SH-CCT diagram for welding[J]. Q J Japan Weld Soc, 44 Pratomo SB, Oktadinata H, Widodo TW (2019) Effect of nickel additions on microstructure evolution and mechanical properties of low-alloy Cr-Mo cast steel[C]//IOP Conference Series: Materials Science and Engineering. IOP Publishing, 541(1): 012050 Zhu XR (1999) Marine Corrosion and Protection of Metal Materials [M]. National Defense Industry, Beijing, pp 123–126 Zhang S, Liu J, Tang M et al (2021) Role of rare earth elements on the improvement of corrosion resistance of micro-alloyed steels in 3.5 wt.% NaCl solution[J]. J Mater Res Technol 11:519–534 Makhdoom MA, Kamran M, Awan GH et al (2013) Effect of multipasses on microstructure and electrochemical behavior of weldments[J]. Metall Mater Trans A 44(12):5505–5512 Liu C, Revilla RI, Liu Z et al (2017) Effect of inclusions modified by rare earth elements (Ce, La) on localized marine corrosion in Q460NH weathering steel[J]. Corros Sci 129:82–90 ​​Reformatskaya II, Freiman LI (2001) Precipitation of sulfide inclusions in steel structure and their effect on local corrosion processes[J]. Prot Met 37:459–464 Liu Z, Lian X, Liu T et al (2020) Effects of rare earth elements on corrosion behaviors of low - carbon steels and weathering steels[J]. Mater Corros 71(2):258–266 Ishikawa T, Minamigawa M, Kandori K et al (2004) Influence of metal ions on the transformation of γ-FeOOH into α-FeOOH[J]. J Electrochem Soc 151(9):B512 Cite Share Download PDF Status: Under Review Version 1 posted Reviewers agreed at journal 23 Jul, 2024 Reviewers invited by journal 22 Jul, 2024 Editor invited by journal 18 Jul, 2024 Editor assigned by journal 18 Jul, 2024 First submitted to journal 18 Jul, 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. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. 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-4744193","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":330197082,"identity":"8b5a81c7-f5b8-407e-bdfe-578037537958","order_by":0,"name":"Gaojian Wang","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA3UlEQVRIie3PMQrCMBTG8SeFuASypiD2Cs+94Og1XhEyKXR0cBAEHUR7FY8QDDjV3aFDRejk4iK6iNHJqekomP8Y3o+PAPh8PxoSAGcBJCVN4uakI9pwxjJXzZfiMGtV4Wmxc59GA6PTclpwNIGaENMgliuqJb1cEdK+soSpI/ECZH7Y1pPZCJGYsYRbIitAOXaQ7GLJ803ELSU0bhJJu5IsDA/noICoAUFZESYbw0UAQ0lacedfomy4791vps+ETq6PZ9wVy7VjRQPD7wdee/5ZmUFQOq98Pp/vv3sBCCpLkwmVCQEAAAAASUVORK5CYII=","orcid":"https://orcid.org/0009-0005-7686-0087","institution":"Chongqing University","correspondingAuthor":true,"prefix":"","firstName":"Gaojian","middleName":"","lastName":"Wang","suffix":""},{"id":330197083,"identity":"4b17c9e7-f1b9-408c-b92e-5904d438a4d1","order_by":1,"name":"Dean Deng","email":"","orcid":"https://orcid.org/0000-0002-7423-5684","institution":"Chongqing University","correspondingAuthor":false,"prefix":"","firstName":"Dean","middleName":"","lastName":"Deng","suffix":""},{"id":330197084,"identity":"c6b12e62-ef90-41bf-9399-19f6c737bea7","order_by":2,"name":"Dandan Kang","email":"","orcid":"","institution":"Sichuan Railway College","correspondingAuthor":false,"prefix":"","firstName":"Dandan","middleName":"","lastName":"Kang","suffix":""},{"id":330197085,"identity":"136499d9-0bc5-4ffc-a4e9-5b84ce604b8e","order_by":3,"name":"Yanhong Ye","email":"","orcid":"","institution":"Chongqing University","correspondingAuthor":false,"prefix":"","firstName":"Yanhong","middleName":"","lastName":"Ye","suffix":""}],"badges":[],"createdAt":"2024-07-15 16:14:58","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-4744193/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-4744193/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":62576928,"identity":"44630865-09ce-4cad-a8fb-aaf26c019453","added_by":"auto","created_at":"2024-08-16 05:20:59","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":2193736,"visible":true,"origin":"","legend":"\u003cp\u003eMicrostructure of as-welded zone for weld metals with different Cr contents: ( a ) 0CrTi , ( c ) 0.3CrTi , ( e ) 0CrMo , ( g ) 0.3CrMo micrographs, and SEM images of (b), (d ), (f) and (h) corresponding to (a), (c), (e) and (g) respectively\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-4744193/v1/ba118b7631b0edae8c2ad00f.png"},{"id":62576926,"identity":"b76ef985-eb31-4aec-8328-e98178817390","added_by":"auto","created_at":"2024-08-16 05:20:59","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":1963106,"visible":true,"origin":"","legend":"\u003cp\u003eMicrostructure of reheating zone for weld metals: ( a ) 0CrTi , ( c ) 0.3CrTi , ( e ) 0CrMo , ( g ) 0.3CrMo micrographs, and SEM images of (b), (d), (f) and (h) corresponding to (a), (c), (e) and (g) respectively\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-4744193/v1/ec3520e71861dc072946eee9.png"},{"id":62576925,"identity":"a3613e63-f734-49d9-ad36-f24e98ac7720","added_by":"auto","created_at":"2024-08-16 05:20:59","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":248711,"visible":true,"origin":"","legend":"\u003cp\u003ePotentiodynamic polarization curves of weld metals with different Cr: ( a ) original sample ( b ) 72h immersion\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-4744193/v1/bf20c001047129b6e39d50d6.png"},{"id":62576924,"identity":"9aed4b98-3bbb-4293-9685-a3729b403222","added_by":"auto","created_at":"2024-08-16 05:20:59","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":195873,"visible":true,"origin":"","legend":"\u003cp\u003eElectrochemical impedance spectra of weld metals with different Cr: ( a ) original sample ( b ) 72h immersion\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-4744193/v1/c2a0f233b935fa24e67f720d.png"},{"id":62576927,"identity":"8b94656d-8e91-463e-8716-71708ff9b0e2","added_by":"auto","created_at":"2024-08-16 05:20:59","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":572317,"visible":true,"origin":"","legend":"\u003cp\u003eSEM images of 0CrTi and 0.3CrTi welds (red circles: nucleation inclusions, blue circles: sympathetic nucleation)\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-4744193/v1/edee5de7737fbaa953aee1d3.png"},{"id":62576929,"identity":"9d246504-2a34-48ab-a7de-7272b717a02c","added_by":"auto","created_at":"2024-08-16 05:20:59","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":2162623,"visible":true,"origin":"","legend":"\u003cp\u003eImpact fracture morphology of weld metals with different Cr: (a ) ( b ) ( c ), ( d ) ( e ) ( f ), ( g ) ( h ) ( i ), ( j ) ( k ) ( l ) corresponding to 0CrTi , 0.3CrTi , 0CrMo , 0.3CrMo weld impact fracture, ductile fracture zone and brittle fracture zone\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-4744193/v1/701b90d49c5d32bb88c812d1.png"},{"id":62576930,"identity":"0c7d6d21-de3d-4933-bc12-544905bbc0cb","added_by":"auto","created_at":"2024-08-16 05:20:59","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":1808424,"visible":true,"origin":"","legend":"\u003cp\u003eCross-sectional morphology of rust layer around weld metals after immersion for 72h: (a) 0CrTi, (b) 0.3CrTi, (c) 0CrMo, (d) 0.3CrMo\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-4744193/v1/9473e7da33ea8492bddf51a1.png"},{"id":62577367,"identity":"8d826ee4-2387-4086-94b0-b7d0f902b1ae","added_by":"auto","created_at":"2024-08-16 05:29:04","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":11614536,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4744193/v1/b5e9ff41-836b-4f79-a5d2-ae26af362349.pdf"}],"financialInterests":"","formattedTitle":"Effect of Cr content on microstructure, mechanical properties and corrosion behavior of weld metal in weathering steel of high-speed train bogie","fulltext":[{"header":"1 Introduction","content":"\u003cp\u003eChina's high-speed trains have developed from the CRH1 series with a speed of 200km/ h to the CRH380AM ( CIT500 high-speed test train) with a maximum test speed of over 500km/h [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e] and the CRH380BG high-cold EMU [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e] for extreme harsh environments. With the continuous increase of train operating speeds and the higher demand for resistance to high cold and sandstorm, the train structure exhibits more complex dynamic load behavior. At the same time, the harsher service environment (with temperatures \u0026minus;\u0026thinsp;40℃ or even lower) places more stringent requirements on the low temperature toughness and weather resistance of materials and welds. The bogie frame, as one of the key load-bearing and force-transmitting components, plays a crucial role in ensuring operational safety [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. Therefore, the safety of train operation is vital issues in the technological development of high-speed trains. Due to the inhomogeneity of its composition, structure and mechanical properties, and the existence of high residual stress, the weld is often the weakest part of the structure [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. Thus, the high requirements for low-temperature toughness and weather resistance of the weld metal in high-speed train bogies pose a significant challenge.\u003c/p\u003e \u003cp\u003eAs we all know, Cr is a ferrite stabilizing element, which has been widely used in weld metal to improve strength and corrosion resistance [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. In recent years, many researchers have studied the effect of Cr on the microstructure and mechanical properties of high-strength steel weld metal, and generally found that the increase of Cr in the weld will lead to the increase of yield strength and tensile strength [\u003cspan additionalcitationids=\"CR7 CR8\" citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e], but there is no general consensus in other aspects. In terms of toughness, some studies have shown that increasing Cr can reduce toughness. For example, Surian E et al. [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e] found that the chromium in the weld metal of 2Ni-Cr-0.35Mo alloy system is in the range of 0.04\u0026thinsp;~\u0026thinsp;1.82%, which is harmful to toughness. Evans GM [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e] found that increasing Cr in C-Mn steel welds ranged from 0 to 2.34% would lead to a decrease in toughness, especially when the Cr exceeded 1%. Studies have also found that when Cr content is in a small amount, it is beneficial to toughness, such as Jorge J F et al. [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e] found that when Cr\u0026thinsp;\u0026lt;\u0026thinsp;0.5% in C-Mn welds the toughness was slightly improved. Snieder G et al. [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e] found that in the low-alloy high-strength steel welds containing Mo, Nb, Ti and B, when Cr\u0026thinsp;\u0026lt;\u0026thinsp;0.73%, the weld toughness is sometimes beneficial. CAI Yangchuan et al. [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e] believed that in Ni-Cr-Mo-V welds, when Cr\u0026thinsp;\u0026lt;\u0026thinsp;1.2%, the toughness of weld metal gradually increases with the increase of Cr content. Avazkonandeh et al [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e] found that in Ni-Cr-Cu-Ti-low Mn welds, the impact toughness increases monotonously when 0.05\u0026ndash;0.91% Cr was added. Lee H [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e] found that in the 2Ni-Cr-0.4Mo weld, the toughness is gradually improved by adding Cr 0.02\u0026thinsp;~\u0026thinsp;0.44%. In terms of corrosion, it was generally believed that [\u003cspan additionalcitationids=\"CR13 CR14\" citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e] Cr is significantly enriched in the rust layer, which makes the rust layer denser, reduces the current density during the anodic dissolution reaction, and then improves the corrosion resistance of the deposited metal. However, some scholars hold different views. For example, Sun B et al. [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e] believed that when Cr is 1\u0026ndash;4%, the corrosion rate is high. Feng Hui et al. [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e] found that the addition of Cr alone has little effect on the corrosion resistance.\u003c/p\u003e \u003cp\u003eIt can be seen that the influence of Cr on the toughness and corrosion resistance of steel weld metals under different alloy systems has not been uniform, and the influence of Cr on the properties of steel weld metals containing Ti or Mo in the Ni-Cu alloy system for high-speed train bogies is rarely studied. Therefore, this study aims to investigate the effects of Cr content on the microstructure, mechanical properties and corrosion behavior of steel weld metals containing Ti or Mo in the Ni-Cu alloy system of high-speed train bogies using optical and scanning electron microscopy, mechanical tests, cyclic immersion corrosion tests, and electrochemical tests, revealing its influence mechanism and internal relationship, providing technical support for the development of welding consumables that meet the high requirements of low-temperature toughness and weather resistance for weld metals of high-speed train bogies.\u003c/p\u003e"},{"header":"2 Test Method","content":"\u003cp\u003eIn the study, four kinds of welding wires with different Cr content, 1.2mm in diameter, were independently designed as research materials. The weld metals were prepared according to ISO 14341 for mechanical tests, and 6\u0026thinsp;~\u0026thinsp;8 layers of deposited metal were cladded on the substrate for corrosion tests. GMA Welding was done in the flat position with Ar\u0026thinsp;+\u0026thinsp;20%CO2 shielding gas. The process conditions were current: 250 A, voltage: 28 V, average travel speed: 26cm/min. The interpass temperature was held at less than 200\u0026deg;C. Table \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e showed the chemical compositions of weld metals.\u003c/p\u003e\n\u003cp\u003e\u003c/p\u003e\u0026nbsp;\u003ctable id=\"Tab1\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eChemical composition of weld metals (wt. %)\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eNo.\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eC\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eSi\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eMn\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eCr\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eMo\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eNi\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eCu\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eTi\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0CrTi\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.053\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.40\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.00\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.82\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.35\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.030\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.3CrTi\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.045\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.51\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.09\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.32\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.60\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.38\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.036\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0CrMo\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.055\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.37\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.92\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.04\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.85\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.33\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.3CrMo\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.036\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.36\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.04\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.37\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.02\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.87\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.37\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e\u003c/p\u003e\n\u003cp\u003eTensile tests were conducted using a computer-controlled universal testing machine (CMT5305) according to ISO 5178. Impact tests were performed using a JBW-500B pendulum impact testing machine following ISO 9016.\u003c/p\u003e\n\u003cp\u003eCorrosion performance tests included cyclic immersion corrosion tests and electrochemical analysis. Corrosion resistance tests were conducted based on TB/T 2375-93 for a duration of 72 hours to measure the corrosion rate of the deposited metal. Electrochemical corrosion analysis was performed using a Princeton Applied Research (PAR) 273A electrochemical workstation. The test samples included specimens without cyclic immersion corrosion and those subjected to 72 hours of cyclic immersion corrosion. The working surface of the samples to be exposed was 10mm \u0026times; 10mm, while the remaining parts were encapsulated with epoxy resin. The samples were polished and then subjected to electrochemical measurements. The corrosion medium used was 0.01 mol/L NaHSO3. The scanning potential for polarization curves ranged from \u0026minus;\u0026thinsp;0.25V to 0.25V at a scanning rate of 0.5 mV/s. The frequency response for impedance spectroscopy was set at 100 kHz to 10 MHz, with an amplitude of 10 mV. The test data was fitted using CVIEW and ZView software. The rust layer morphology and micro-area composition after cyclic immersion were analyzed using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS).\u003c/p\u003e\n\u003cp\u003eMetallographic specimens were cut perpendicular to the welding direction and prepared according to standard metallographic methods, polished and etched with 3% nital solution. Metallographic examination is carried out by optical microscope ( OM ). Micrographs taken at 500 magnifications were evaluated using the point-counting method for the proportion of microstructural components in the columnar region and the grain size in the reheated zone, following ASTM E562-2011 and ASTM E112. 10 fields were examined, and a 10\u0026times;10 grid was used for point counting to ensure a minimum of 1000 points. SEM was used to observe the M-A constituents and inclusions in the weld metals at a magnification of \u0026times;2000. 10 random fields were selected in the columnar region, and 5 random fields were selected in the reheated zone. IPP software was used for quantitative analysis of the proportion, size, and characteristics of M-A constituents and inclusions. EDX was used for element mapping and line scan analysis to identify the composition of inclusions and M-A constituents.\u003c/p\u003e\n\u003cp\u003eImpact fracture analysis was performed using SEM. fibrous zone, radial zone and shear lip zone were identified at low magnification, and the proportions of each zone were statistically analyzed using IPP. Micromorphology of impact fracture was observed at 1000 magnification.\u003c/p\u003e"},{"header":"3 Results","content":"\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e\n \u003ch2\u003e3.1 Microstructure of Weld Metals\u003c/h2\u003e\n \u003cdiv id=\"Sec5\" class=\"Section3\"\u003e\n \u003ch2\u003e3.1.1 Microstructure of as-welded zone\u003c/h2\u003e\n \u003cp\u003eThe microstructures of as-welded zones in weld metals with different Cr contents are shown in Fig. 1. Table \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e presents the volume fractions of different microstructures, and Table \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e lists the quantitative results of M-A constituents. The microstructures of weld metals are mainly composed of primary ferrite (PF), ferrite with second phase (FS), acicular ferrite (AF), and M-A constituents (MA). The MA that consists of the mixture of martensite and austenite forms by the martensite transformation of the austenite enriched in C at lower temperatures [\u003cspan class=\"CitationRef\"\u003e18\u003c/span\u003e]. The formation of MA is affected by welding cooling speed as well as chemical composition, and white island particles in SEM images are identified as MA [\u003cspan class=\"CitationRef\"\u003e19\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e20\u003c/span\u003e].\u003c/p\u003e\n \u003cp\u003e\u003c/p\u003e\u0026nbsp;\u003ctable id=\"Tab2\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eQuantitative proportion of microstructure in columnar zone of weld metal with different Cr content\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\" rowspan=\"2\"\u003e\n \u003cp\u003eNo.\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" colspan=\"3\"\u003e\n \u003cp\u003eR \u003csub\u003emico\u003c/sub\u003e /%\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003ePF\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eAF\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eFS\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0CrTi\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e52.3\u0026thinsp;\u0026plusmn;\u0026thinsp;5.64\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e40.05\u0026thinsp;\u0026plusmn;\u0026thinsp;5.81\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e7.65\u0026thinsp;\u0026plusmn;\u0026thinsp;1.8\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.3CrTi\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e39.8\u0026thinsp;\u0026plusmn;\u0026thinsp;5.31\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e55.5\u0026thinsp;\u0026plusmn;\u0026thinsp;5.98\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e4.7\u0026thinsp;\u0026plusmn;\u0026thinsp;1.22\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0CrMo\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e74.6\u0026thinsp;\u0026plusmn;\u0026thinsp;5.67\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e20.9\u0026thinsp;\u0026plusmn;\u0026thinsp;5.23\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e4.5\u0026thinsp;\u0026plusmn;\u0026thinsp;1.02\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.3CrMo\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e70.5\u0026thinsp;\u0026plusmn;\u0026thinsp;6.22\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e19\u0026thinsp;\u0026plusmn;\u0026thinsp;6.11\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e10.5\u0026thinsp;\u0026plusmn;\u0026thinsp;2.08\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003ctfoot\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"4\"\u003eNote: R \u003csub\u003emico\u003c/sub\u003e \u003cem\u003e\u0026mdash;\u003c/em\u003e ratio of microstructures, PF \u003cem\u003e\u0026mdash;\u003c/em\u003e primary ferrite, AF \u003cem\u003e\u0026mdash;\u003c/em\u003e aciular ferrite, FS \u003cem\u003e\u0026mdash;\u003c/em\u003e ferrite with second phases\u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tfoot\u003e\n \u003c/table\u003e\n \u003cp\u003e\u003c/p\u003e\n \u003cp\u003eFrom Fig. 1 and Table \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e, It can be seen that compared with 0CrTi, in the 0.3CrTi weld, which is the Ti-containing weld added by 0.3% Cr, the microstructure is dominated by AF, AF is increased by 15%, both grain boundary ferrite and FS are decreased, the size of AF is significantly reduced, and the dendrite spacing does not change much, but the width of ferrite side-plate tends to decrease. Compared with 0CrMo, in the 0.3CrMo weld, which is the Mo-containing weld added by 0.3% Cr, the microstructure is dominated by PF, the AF does not change much, grain boundary ferrite is decreased, FS is increased, the width of AF does not change much, and the width of columnar grains is reduced slightly. It can be considered that Cr has different effects on microstructure in welds with different components.\u003c/p\u003e\n \u003cp\u003e\u003c/p\u003e\u0026nbsp;\u003ctable id=\"Tab3\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eQuantitative proportion of MA in columnar zone of weld metals\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eNo.\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eAavg / \u0026micro;m2 \u003csub\u003e_\u003c/sub\u003e _ \u003csup\u003e_\u003c/sup\u003e\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eR \u003csub\u003ea\u003c/sub\u003e /%\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0CrTi\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.1\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.3CrTi\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.21\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.6\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0CrMo\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.25\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.4\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.3CrMo\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.41\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e2.5\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003ctfoot\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"3\"\u003eNote: A \u003csub\u003eavg\u003c/sub\u003e \u003cem\u003e\u0026mdash;\u003c/em\u003e average area of MA, R \u003csub\u003ea\u003c/sub\u003e \u003cem\u003e\u0026mdash;\u003c/em\u003e area ratio of MA\u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tfoot\u003e\n \u003c/table\u003e\n \u003cp\u003e\u003c/p\u003e\n \u003cp\u003eFrom Fig. 1 and Table \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e, it can be observed that the MA in each weld are mainly blocky. With the addition of Cr, the proportion of MA increases, the increment is greater in the weld containing Mo, from 0.4\u0026ndash;2.5%. For the size of MA, it decreases slightly in the weld containing Ti, but it increases significantly in the welds containing Mo.\u003c/p\u003e\n \u003cp\u003e\u003c/p\u003e\u0026nbsp;\u003ctable id=\"Tab4\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eInclusions in weld metals\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eNo.\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eT \u003csub\u003ei\u003c/sub\u003e\u003c/p\u003e\n \u003cp\u003e/ea\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eRR \u003csub\u003ei\u003c/sub\u003e\u003c/p\u003e\n \u003cp\u003e/\u0026nbsp;\u0026micro;\u0026nbsp;m\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eMR \u003csub\u003ei\u003c/sub\u003e\u003c/p\u003e\n \u003cp\u003e/\u0026nbsp;\u0026micro;\u0026nbsp;m\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eD \u003csub\u003ei\u003c/sub\u003e\u003c/p\u003e\n \u003cp\u003e/ea/mm\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eT \u003csub\u003eni\u003c/sub\u003e\u003c/p\u003e\n \u003cp\u003e/ea\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eT \u003csub\u003eni\u003c/sub\u003e\u003c/p\u003e\n \u003cp\u003e/ea\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eRR \u003csub\u003eni\u003c/sub\u003e\u003c/p\u003e\n \u003cp\u003e/\u0026nbsp;\u0026micro;\u0026nbsp;m\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0CrTi\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e322\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.11\u0026thinsp;~\u0026thinsp;0.54\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.24\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e11332\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e69\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.14\u0026thinsp;~\u0026thinsp;0.54\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.3\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.3CrTi\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e231\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.11\u0026thinsp;~\u0026thinsp;0.47\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.22\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e8129\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e28\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.17\u0026thinsp;~\u0026thinsp;0.43\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.27\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0CrMo\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e251\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.14\u0026thinsp;~\u0026thinsp;0.63\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.28\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e8833\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e46\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.21\u0026thinsp;~\u0026thinsp;0.58\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.35\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.3CrMo\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e326\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.11\u0026thinsp;~\u0026thinsp;0.84\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.23\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e11472\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e15\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.16\u0026thinsp;~\u0026thinsp;0.84\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.36\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003ctfoot\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"8\"\u003eNote: T \u003csub\u003ei\u003c/sub\u003e \u0026mdash; total number of inclusions, RR \u003csub\u003ei\u003c/sub\u003e \u0026mdash; radius range of inclusions, MR \u003csub\u003ei\u003c/sub\u003e \u0026mdash; mean radius of inclusions, D \u003csub\u003ei\u003c/sub\u003e \u0026mdash; Density of inclusions, T \u003csub\u003eni\u003c/sub\u003e \u0026mdash; Total number of nucleation inclusions, RR \u003csub\u003eni\u003c/sub\u003e \u0026mdash; radius range of nucleation inclusions, MR \u003csub\u003eni\u003c/sub\u003e \u0026mdash; mean radius of inclusions nucleation radius\u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tfoot\u003e\n \u003c/table\u003e\n \u003cp\u003e\u003c/p\u003e\n \u003cp\u003eTable \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e shows the quantitative results of inclusions examined by SEM. Cr reduces the nucleation rate of inclusions and the average size of inclusions in both welds. The influence of Cr on the inclusion density is different in the two types of welds. The inclusion density is reduced in the Ti-containing welds, but increased in the Mo-containing welds.\u003c/p\u003e\n \u003cp\u003eThe composition of the inclusions was further analyzed. As can be seen from Table \u003cspan class=\"InternalRef\"\u003e5\u003c/span\u003e, the composition of the inclusions includes (Mn, Al, Si)Ox, FeOx, TiOx, CuS, etc. Compared with 0CrTi and 0.3CrTi, the latter has lower MnOx, SiOx, and TiOx, which means it is probably related to the low oxygen content of the 0.3CrTi weld. The higher the oxygen content, the more Mn and Si are consumed, and the more Mn and Si oxides are produced [\u003cspan class=\"CitationRef\"\u003e21\u003c/span\u003e]. Comparing the two types of welds, it is found that Cr was presence in the inclusions of the welds adding Cr (0.3CrTi and 0.3CrMo), and the Cu was decreased at the same time, which may be due to the absorption of Cr by inclusions [\u003cspan class=\"CitationRef\"\u003e22\u003c/span\u003e] and the formation of CrS with S, while the content of CuS was reduced.\u003c/p\u003e\n \u003cp\u003e\u003c/p\u003e\u0026nbsp;\u003ctable id=\"Tab5\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 5\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eComposition of inclusions in weld metals (wt. %)\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eNo.\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eO\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eAl\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eSi\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eS\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eTi\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eCr\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eMn\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eFe\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eCu\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0CrTi\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e14.76\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.77\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.62\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.69\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e5.01\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e4.14\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e70.37\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.10\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.3CrTi\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e15.71\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.97\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.89\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.77\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e5.86\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e4.45\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e68.73\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.24\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0CrMo\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e17.51\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.87\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e6.16\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.07\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e7.77\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e65.91\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.71\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.3CrMo\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e22.65\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.79\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e7.15\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.83\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.33\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e8.78\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e58.98\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.67\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003cp\u003e\u003c/p\u003e\n \u003c/div\u003e\n \u003cdiv id=\"Sec6\" class=\"Section3\"\u003e\n \u003ch2\u003e3.1.2 Microstructure of reheat zone\u003c/h2\u003e\n \u003cp\u003eThe microstructures of the reheated zones in weld metals are shown in Fig. 2. The columnar grains transformed into equiaxed ferrite grains due to the reheating effect of the subsequent weld bead. The statistical results of the grain size and MA constituent in the reheating zone are shown in Table \u003cspan class=\"InternalRef\"\u003e6\u003c/span\u003e. The grain size of the reheat zone of all welds in this study is small, and the addition of Cr has little effect on it. It tends to increase in the welds containing Ti, while it tends to decrease in the welds containing Mo.\u003c/p\u003e\n \u003cp\u003eMA in the reheat zone of each weld are blocky, and their number are increased significantly with the addition of Cr. Moreover, the size of MA in the weld containing Mo are increased by the effect of Cr.\u003c/p\u003e\n \u003cp\u003e\u003c/p\u003e\u0026nbsp;\u003ctable id=\"Tab6\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 6\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eQuantitative analysis of grain size and MA in reheating zone of weld metals\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eNo.\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eS \u003csub\u003eg\u003c/sub\u003e\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eAavg / \u0026micro;m2 \u003csub\u003e_\u003c/sub\u003e _ \u003csup\u003e_\u003c/sup\u003e\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eR \u003csub\u003ea\u003c/sub\u003e /%\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0CrTi\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e10.54\u0026thinsp;\u0026plusmn;\u0026thinsp;0.11\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.12\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.06\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.3CrTi\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e10.11\u0026thinsp;\u0026plusmn;\u0026thinsp;0.37\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.25\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.5\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0CrMo\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e10.26\u0026thinsp;\u0026plusmn;\u0026thinsp;0.21\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.18\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.1\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.3CrMo\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e10.46\u0026thinsp;\u0026plusmn;\u0026thinsp;0.34\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.26\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.5\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003ctfoot\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"4\"\u003eNote: S \u003csub\u003eg\u003c/sub\u003e \u003cem\u003e\u0026mdash;\u003c/em\u003e grain size, A \u003csub\u003eavg\u003c/sub\u003e \u003cem\u003e\u0026mdash;\u003c/em\u003e average area of MA, R \u003csub\u003ea\u003c/sub\u003e \u003cem\u003e\u0026mdash;\u003c/em\u003e area ratio of MA\u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tfoot\u003e\n \u003c/table\u003e\n \u003cp\u003e\u003c/p\u003e\n \u003c/div\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec7\" class=\"Section2\"\u003e\n \u003ch2\u003e3.2 Analysis of mechanical properties\u003c/h2\u003e\n \u003cp\u003eThe effects of Cr on the tensile properties and impact toughness of weld metals are shown in Table \u003cspan class=\"InternalRef\"\u003e7\u003c/span\u003e. With the addition of 0.3% Cr, the yield strength and tensile strength in both Ti and Mo-containing welds are increased, which may be related to the solution strengthening effect of Cr, the increase of AF and the refinement of microstructures.\u003c/p\u003e\n \u003cp\u003eThe toughness of both Ti and Mo-containing welds are reduced by the addition of Cr. Compared with 0.3CrTi and 0CrTi, the impact energy at -40℃ and \u0026minus;\u0026thinsp;60℃ in the weld containing Ti are reduced by 30J and 49J, respectively. And compared with 0.3CrMo and 0CrMo, the impact energy at -40℃ and \u0026minus;\u0026thinsp;60℃ in the weld containing Mo are reduced by 44J and 16J, respectively.\u003c/p\u003e\n \u003cp\u003e\u003c/p\u003e\u0026nbsp;\u003ctable id=\"Tab7\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 7\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eEffect of Cr on tensile properties and impact toughness of weld metals\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eNo.\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eR\u003csub\u003em\u003c/sub\u003e /MPa\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eR\u003csub\u003eeL\u003c/sub\u003e/MPa\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eA/%\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eKV \u003csub\u003e2\u003c/sub\u003e (-40℃)/J\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eKV \u003csub\u003e2\u003c/sub\u003e (-60℃)/J\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0CrTi\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e574\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e492\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e26.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e159\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e118\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.3CrTi\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e700\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e636\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e26\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e129\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e69\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0CrMo\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e559\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e463\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e27.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e149\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e78\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.3CrMo\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e575\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e488\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e28\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e105\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e62\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003cp\u003e\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\n \u003ch2\u003e3.3Analysis of corrosion resistance\u003c/h2\u003e\n \u003cdiv id=\"Sec9\" class=\"Section3\"\u003e\n \u003ch2\u003e3.3.1 Result and analysis of 72h immersion corrosion test\u003c/h2\u003e\n \u003cp\u003eThe results of the 72h immersion accelerated corrosion test of weld metals are shown in Table \u003cspan class=\"InternalRef\"\u003e8\u003c/span\u003e. It can be seen that, Cr has little effect on the initial corrosion rate of the Ti-containing weld, but Cr makes the initial corrosion rate of the Mo-containing weld decreased from 1.745g\u0026middot;mm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e\u0026middot;h\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e to 1.642g\u0026middot;mm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e\u0026middot;h\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, indicating the beneficial effect of Cr on the corrosion resistance of the Mo-containing weld.\u003c/p\u003e\n \u003cp\u003e\u003c/p\u003e\u0026nbsp;\u003ctable id=\"Tab8\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 8\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003e72h immersion corrosion performance of weld metals with different Cr\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eNo.\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eCR/g mm \u003csup\u003e\u0026minus;2\u003c/sup\u003e h \u003csup\u003e\u0026minus;1\u003c/sup\u003e\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eR \u003csub\u003ewl\u003c/sub\u003e /%\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0CrTi\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.646\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.35\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.3CrTi\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.669\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.37\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0CrMo\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.745\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.44\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.3CrMo\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.642\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.35\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003ctfoot\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"3\"\u003eNote: \u003cem\u003eCR \u0026mdash;corrosion\u003c/em\u003e rate, \u003cem\u003eR\u003c/em\u003e \u003csub\u003e\u003cem\u003ewl\u003c/em\u003e\u003c/sub\u003e \u003cem\u003e\u0026mdash;corrosion\u003c/em\u003e weight loss ratio\u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tfoot\u003e\n \u003c/table\u003e\n \u003cp\u003e\u003c/p\u003e\n \u003c/div\u003e\n \u003cdiv id=\"Sec10\" class=\"Section3\"\u003e\n \u003ch2\u003e3.3.2 Results and Analysis of Electrochemical test\u003c/h2\u003e\n \u003cp\u003eFigure \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e shows the potentiodynamic polarization curves of weld metals with different Cr. The corrosion potential and corrosion current density were obtained through Tafel fitting of the potentiodynamic polarization curves. Figure \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e presents the impedance spectra of weld metals with different Cr. The fitted corrosion potential, corrosion current density, and impedance results are shown in Table \u003cspan class=\"InternalRef\"\u003e9\u003c/span\u003e.\u003c/p\u003e\n \u003cp\u003e\u003c/p\u003e\u0026nbsp;\u003ctable id=\"Tab9\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 9\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eFitting results of electrochemical tests for samples with different Cr\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\" rowspan=\"2\"\u003e\n \u003cp\u003eNo.\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" colspan=\"2\"\u003e\n \u003cp\u003eE \u003csub\u003ecorr\u003c/sub\u003e /mV\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" colspan=\"2\"\u003e\n \u003cp\u003eIcorr \u003csub\u003e/\u003c/sub\u003e \u0026micro;A\u0026middot;cm \u003csup\u003e\u0026minus;2\u003c/sup\u003e\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" colspan=\"2\"\u003e\n \u003cp\u003eR/Ω\u0026middot;cm2\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eRaw\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e72h\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eRaw\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e72h\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eRaw\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e72h\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0CrTi\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-1405\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-920\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e75.38\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e53.59\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e247\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e245\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.3CrTi\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-1437\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-1090\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e62.77\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e46.95\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e290\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e377\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0CrMo\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-1261\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-972\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e95.65\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e43.9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e215\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e195\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.3CrMo\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-1223\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-1112\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e65.19\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e49.33\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e218\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e206\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003ctfoot\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"7\"\u003eNote: E \u003csub\u003ecorr\u003c/sub\u003e \u003cem\u003e\u0026mdash;\u003c/em\u003e self-etching potential, I \u003csub\u003ecorr\u003c/sub\u003e \u003cem\u003e\u0026mdash;\u003c/em\u003e self-etching current density, R \u003cem\u003e\u0026mdash;\u003c/em\u003e resistance\u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tfoot\u003e\n \u003c/table\u003e\n \u003cp\u003e\u003c/p\u003e\n \u003cp\u003eFrom the fitting results, it can be observed that the corrosion potential of the samples immersed for 72h has shifted positively compared to the original samples, indicating that the presence of rust layer on the surface of the weld metals impedes the electrochemical anodic dissolution of the weld matrix. In the two types of welds, Cr has little effect on the corrosion potential of the original sample, and has a negative shift on the corrosion potential of the immersion for 72h, indicating that Cr almost does not affect the corrosion tendency of the matrix, but increases the corrosion tendency of the rust layers.\u003c/p\u003e\n \u003cp\u003eIn the weld containing Ti, Cr has a slight effect on the corrosion current density and resistance of the original sample. For the sample after 72h of cyclic immersion, Cr significantly reduces the corrosion current density and increases the resistance of the rust layer. This indicates that in the Ti-containing weld, Cr has no significant effect on the initial corrosion rate, but plays a positive role in reducing the corrosion rate of the rust layer. In the weld containing Mo, Cr reduces the corrosion current density of the original sample, and slightly increases the resistance of the rust layer. For the samples immersed for 72h, the corrosion current density and the resistance of the rust layer have little change, which indicates that Cr in the Mo-containing weld is beneficial to the initial corrosion of the weld, but has no obvious effect on the later corrosion.\u003c/p\u003e\n \u003c/div\u003e\n\u003c/div\u003e"},{"header":"4 Discussions","content":"\u003cdiv id=\"Sec12\" class=\"Section2\"\u003e\n \u003ch2\u003e4.1 Effect of Cr on microstructure of weld metals\u003c/h2\u003e\n \u003cp\u003eIt is well known that Cr is a ferrite stabilizing element [\u003cspan class=\"CitationRef\"\u003e23\u003c/span\u003e]. From the comparison of the Fe-Cr phase diagram [\u003cspan class=\"CitationRef\"\u003e24\u003c/span\u003e] and the CCT curves of Si-0.2 and Cr-0.5 welds given in the literature [\u003cspan class=\"CitationRef\"\u003e25\u003c/span\u003e], it can be seen that when a trace amount of Cr is added, the phase field moves downward, the A3 temperature is slightly reduced, the initial ferrite temperature is reduced, but the ferrite end temperature is almost unchanged. According to the Ms equation [\u003cspan class=\"CitationRef\"\u003e26\u003c/span\u003e] and combined with the CCT curve, the starting temperature of the martensitic transformation is slightly lowered with the addition of 0.3% Cr, and the ending temperature is reduced more significantly.\u003c/p\u003e\n \u003cp\u003eCr reduces the initial transformation temperature of ferrite, that is, reduces the transformation driving force that preferentially forms ferrite, which leads to the decrease number and size of PF in 0.3CrTi and 0.3CrMo welds. In the welds containing Ti, the Ti oxide formed is the most effective inclusion for AF nucleation [\u003cspan class=\"CitationRef\"\u003e27\u003c/span\u003e]. While Cr reduces PF, it provides more space for Ti oxide to induce acicular ferrite nucleation and growth, which leads to the increase of AF in the 0.3CrTi weld. Although the number of AF-nucleated inclusions in 0.3CrTi decreases, it still does not affect the increase of AF, because AF can be promoted by autocatalytic nucleation on the already formed AF [\u003cspan class=\"CitationRef\"\u003e28\u003c/span\u003e], as shown in FIG. 5, sympathetic nucleation was found in both 0CrTi and 0.3CrTi welds. In the Mo-containing weld, it lacks effective AF-nucleated inclusions, and AF has no advantage in competitive growth with FS [\u003cspan class=\"CitationRef\"\u003e29\u003c/span\u003e]. The decrease of PF provides space for the growth of FS, which explains that AF does not change, but FS increases in the 0.3CrMo weld.\u003c/p\u003e\n \u003cp\u003eIn the reheat zone, Cr can slightly reduce the temperature of Ac3, which increases the high temperature residence time of austenitizing and then slightly coarsens the grains. However, it is also restrained by the pinning effect of inclusions [\u003cspan class=\"CitationRef\"\u003e30\u003c/span\u003e]. From Table \u003cspan class=\"InternalRef\"\u003e7\u003c/span\u003e and Table \u003cspan class=\"InternalRef\"\u003e9\u003c/span\u003e, It can be seen that the correlation between the inclusion density and the grain size of the reheat zone shows that, compared with the weld without Cr, the change of the grain size in the reheat zone of the weld with Cr is negatively correlated with the change of the inclusion density, indicating that the inclusion is the key to the influence of the grain size.\u003c/p\u003e\n \u003cp\u003eMA are formed from untransformed austenite during the cooling process, and a lower content of residual austenite above the Ms temperature reduces the presence of MA [\u003cspan class=\"CitationRef\"\u003e31\u003c/span\u003e]. As mentioned above, Cr reduces the starting temperature of the transition to ferrite, while hardly changing the end temperature of the transition to ferrite, which results in insufficient transition to ferrite, leaving more residual austenite. Cr can slightly lower the Ms temperature, but more significantly lower the Mf temperature, which provides more time for the transition of residual austenite to martensite, and then more MA are formed, which explains the large increase in MA of 0.3CrMo compared to 0CrMo. However, in 0.3CrTi, compared with 0CrTi, the increment of MA is less, because the nucleation AF induced by the inclusion containing Ti can promote the ferrite transformation sufficiently.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec13\" class=\"Section2\"\u003e\n \u003ch2\u003e4.2 Effect of Cr on the toughness of weld metals\u003c/h2\u003e\n \u003cp\u003eThe role of Cr in the microstructure, MA, and inclusions of weld metal is a crucial factor affecting impact toughness. AF, due to its fine grain size and interlocking structure with high angle boundaries, acts as an obstacle to crack propagation, thereby enhancing the toughness of weld metal [\u003cspan class=\"CitationRef\"\u003e32\u003c/span\u003e].\u003c/p\u003e\n \u003cp\u003eIn welds containing Ti, Cr increases the AF in the welded zone but decreases the toughness. It has been pointed out that the optimal microstructure of weld metals requires high AF, but not the highest level of AF content [\u003cspan class=\"CitationRef\"\u003e33\u003c/span\u003e]. One of the reasons for the decrease in toughness may be that the grain size of the reheat zone in the 0.3CrTi weld is coarsened. At the same time, the toughness of ferrite matrix in 0.3CrTi weld is reduced by the low Ni content. In the Mo-containing weld, Cr almost did not change the AF content, and the grain size of the reheat zone was refined, so the toughness should be increased but decreased, indicating that the reduction of toughness was affected by other factors.\u003c/p\u003e\n \u003cp\u003eMA are essential factors controlling toughness [\u003cspan class=\"CitationRef\"\u003e9\u003c/span\u003e], and embrittlement cracking of MA or debonding of M-A from the matrix initiates cleavage fracture [\u003cspan class=\"CitationRef\"\u003e34\u003c/span\u003e]. There is a direct relationship between impact toughness and MA, the impact toughness decreased with an increase in MA [\u003cspan class=\"CitationRef\"\u003e10\u003c/span\u003e]. For the welds containing Ti and Mo, whether in the as-welded zone or the reheat zone, Cr increases the content and size of MA, especially in the welds containing Mo, which may be the main reason for the reduction of weld toughness caused by Cr. This is consistent with the conclusions of Evans G M[\u003cspan class=\"CitationRef\"\u003e7\u003c/span\u003e] and Snieder G et al. [\u003cspan class=\"CitationRef\"\u003e11\u003c/span\u003e]. However, in the weld containing Ti, the MA increased by Cr is not large, and its reduction in toughness is limited.\u003c/p\u003e\n \u003cp\u003eFurthermore, the influence of inclusions on the mechanical properties of weld metal is two-sided. Lan L et al. [\u003cspan class=\"CitationRef\"\u003e35\u003c/span\u003e] suggests that when inclusions exceed 1 \u0026micro;m, they tend to act as nucleation sites for cleavage cracks due to their lower local fracture stress. In this study, for the Ti-containing weld, Cr has little effect on the inclusion size, which is less than 1\u0026micro;m. In the Mo-containing weld, Cr increases the maximum inclusion size from 1.2\u0026micro;m to 1.7\u0026micro;m, which may lead to a decrease in toughness. As Cr is a strong carbide, Chen J H et al. [\u003cspan class=\"CitationRef\"\u003e36\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e37\u003c/span\u003e] found that carbide particles may lead to crack initiation. However, according to literature [\u003cspan class=\"CitationRef\"\u003e38\u003c/span\u003e], Cr carbides will not be deposited in the weld of low-alloy high-strength steel containing less than 4% Cr. In this study, due to the small Cr content, no Cr carbides were observed.\u003c/p\u003e\n \u003cp\u003eIn short, Cr reduces the toughness of weld metals due to increase the number and size of MA as well as coarsen inclusions. For the Ti-containing weld, this effect of Cr is not obvious. In order to further study, the weld toughness, the microscopic characterization of the impact fracture of the weld metal was carried out, as shown in SEM micrographs in Fig. 8. Their fracture modes are a combination of brittle and ductile fracture. The fracture surfaces can be divided into three zones: fibrous zone, radial zone, and shear lip zone, the energy absorbed for fibrous zone and shear lip zone formation account mostly for the total CVN energy. Table \u003cspan class=\"InternalRef\"\u003e10\u003c/span\u003e presents the proportions of each zone.\u003c/p\u003e\n \u003cp\u003eCompared with 0.3CrMo and 0CrMo, Cr reduces the sum of the proportion of fibrous zone and shear lip zone, and the brittle fracture region increases, which leads to the increase of cleavage surface and the decrease of absorbed energy. This is consistent with the toughness results. However, compared with 0CrTi, in the 0.3CrTi weld, the radial zone does not increase, which also indicates that the main reason affecting its toughness is that Ni reduces the toughness of the ferritic matrix [\u003cspan class=\"CitationRef\"\u003e39\u003c/span\u003e]. As can be seen from Fig.\u0026nbsp;6, compared with 0CrTi, the dimples in the ductile fracture zone of 0.3CrTi weld are shallower. Compared with 0CrMo, the cleavage surface of brittle fracture zone in 0.3CrMo welds increased. These confirmed that the reduction in toughness of the two Cr-adding welds.\u003c/p\u003e\n \u003cp\u003e\u003c/p\u003e\u0026nbsp;\u003ctable id=\"Tab10\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 10\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eProportion of impact fracture area weld metals with different Cr\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eNo.\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eFZ/%\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eSZ/%\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eRZ/%\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0CrTi\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e32\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e39\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e29\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.3CrTi\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e26\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e48\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e26\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0CrMo\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e18\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e72\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e10\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.3CrMo\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e33\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e30\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e37\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003ctfoot\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"4\"\u003eNote: FZ \u0026mdash; fibrous zone, SZ \u0026mdash; Shear lip zone, RZ \u0026mdash; radial zone\u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tfoot\u003e\n \u003c/table\u003e\n \u003cp\u003e\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec14\" class=\"Section2\"\u003e\n \u003ch2\u003e4.3 Effect of Cr on corrosion resistance\u003c/h2\u003e\n \u003cp\u003eThe fracture morphology of the rust layer after immersion corrosion for 72 h is shown in Fig.\u0026nbsp;8. The corrosion rust layer is divided into an inner rust layer and an outer rust layer. The alloying elements act mainly through their influence on the inner rust layer[\u003cspan class=\"CitationRef\"\u003e40\u003c/span\u003e]. The formation of the inner rust layer occurs in the initial stage of corrosion, including local corrosion initiation and local corrosion expansion [\u003cspan class=\"CitationRef\"\u003e41\u003c/span\u003e]. Further, the outer rust layer is formed on the inner rust layer, providing long-term corrosion resistance against the environment.\u003c/p\u003e\n \u003cp\u003eAF has good corrosion resistance, which provides less contact with corrosive media areas [\u003cspan class=\"CitationRef\"\u003e18\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e42\u003c/span\u003e]. In addition, the increase of MA will reduce the corrosion potential and then promote the local corrosion [\u003cspan class=\"CitationRef\"\u003e18\u003c/span\u003e]. Compared with 0CrTi, in 0.3CrTi welds, the positive effect of a large increase of AF on corrosion resistance and the negative effect of the increase of MA offset each other, indicating that the initial corrosion rate changes little. Compared with 0CrMo, the corrosion resistance in 0.3CrMo welds should be adversely affected by the significant increase of MA, but in fact which is beneficial to the initial corrosion. This contradiction cannot be explained by AF and MA.\u003c/p\u003e\n \u003cp\u003eThe corrosion resistance of inclusions is much lower than that of the matrix [\u003cspan class=\"CitationRef\"\u003e43\u003c/span\u003e]. Literature [\u003cspan class=\"CitationRef\"\u003e41\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e44\u003c/span\u003e] has indicated that the corrosion process originates from local pitting that occurs at active sites (especially inclusions), which then expands into uneven general corrosion through the extension and merging of small pitting nuclei. As mentioned above, Cr enables inclusion to adsorb Cr and form CrS, which reduces the adverse effect of MnS in inclusion on initial corrosion [\u003cspan class=\"CitationRef\"\u003e45\u003c/span\u003e], which plays a dominant role in welds containing Mo. In the Ti-containing weld (0.3CrTi), TiO2 becomes the core of the inclusion and promotes Mn to form MnS on its surface, which counteracts the inhibition effect of Cr.\u003c/p\u003e\n \u003cp\u003eFrom the cross section morphology of the rust layer given in Fig.\u0026nbsp;8, it can be seen that the addition of Cr in the two types of welds leads to Cr enrichment in the inner rust layer. As the crystalline core of the rust phase grains, Cr accelerates the \u0026alpha;-FeOOH transformation and promotes the densification of the rust layer [\u003cspan class=\"CitationRef\"\u003e46\u003c/span\u003e], and the outer rust layer grown from this dense inner rust layer is also relatively dense [\u003cspan class=\"CitationRef\"\u003e40\u003c/span\u003e].\u003c/p\u003e\n \u003cp\u003eFrom FIG. 7 (a)(b), it can be seen that in the weld containing Ti, the addition of Cr changes the inner and outer rust layers of the weld from obviously loose (0CrTi) to dense (0.3CrTi). In 0.3CrTi welds, the cracks and holes in the outer rust layer are reduced, and the corrosion liquid absorbed by the outer rust layer to the substrate surface through the capillary effect is reduced, thus reducing the corrosion rate of the weld. This explains the great benefit of adding Cr to the weld containing Ti to reduce the corrosion rate of the rust layer.\u003c/p\u003e\n \u003cp\u003eAs can be seen from FIG. 7 (c)(d), in the weld containing Mo, Cr enrichment in the inner rust layer did not make the inner and outer rust layers denser. Literature [\u003cspan class=\"CitationRef\"\u003e15\u003c/span\u003e] pointed out that Mo improved the corrosion resistance better than Cr. Compared with 0CrMo welds, the corrosion resistance damage caused by the low Mo content in 0.3CrMo welds counteracts the benefits of adding Cr. So Cr does not play its role in improving the corrosion resistance of welds in 0.3CrMo welds.\u003c/p\u003e\n\u003c/div\u003e"},{"header":"5 Conclusion","content":"\u003cp\u003eThe effect of adding 0.30% Cr content on the microstructure and properties of the weld metal containing Ti or Mo in the Ni-Cu alloy system for high-speed train bogies was studied, and the following conclusions were drawn:\u003c/p\u003e \u003cp\u003e(1) When 0.3%Cr was added to the weld containing Ti, the AF content was increased by about 15%, both grain boundary ferrite and FS are decreased, and the microstructure was mainly AF. The number of MA increases slightly. The addition of 0.3%Cr in the weld containing Mo almost did not change the AF content, the grain boundary ferrite decreased and FS increased, the microstructure was dominated by PF, and the number of MA in the as-welded zone increased significantly (0.4–2.5%).\u003c/p\u003e \u003cp\u003e(2) Cr reduces the toughness of welds by increasing number and size of M-A component as well as coarsening inclusions. the impact energy of -40℃ and − 60℃ in the weld containing Mo is reduced by 44J and 16J, respectively. In the weld containing Ti, this effect of Cr is not obvious.\u003c/p\u003e \u003cp\u003e(3) Cr makes the inclusion adsorb Cr and inhibits the formation of soluble MnS, which is the main reason for the decrease of the initial corrosion rate of the welds containing Mo, while this effect is weakened in the welds containing Ti. Cr densifies the inner and outer rust layers and then reduces the corrosion rate of weld.\u003c/p\u003e "},{"header":"Declarations","content":"\n\u003ch3\u003eFunding and Conflicts of interests\u003c/h3\u003e\n\u003cp\u003eThis work was supported by Science and Technology Department of Sichuan Province (Grant numbers [2019ZDZX0017]). The authors have no competing interests to declare that are relevant to the content of this article.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eXu YG, Li Y (2020) Research on Technical Indexes of 400 km / h Wheel-Rail EMU for Chengdu-Chongqing Middle Line [J]. High speed Railway Technol 11(3):5\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eXiang AF, Yu WL, Chen MG Cold-proof Technology on Traction Motor of High-cold CRH380B EMUs [J]. ELECTRIC DRIVE FOR LOCOMOTIVES, 2014(4):4\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWang BM (2014) EMU overall and bogie[M], 2nd edn. 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J Electrochem Soc 151(9):B512\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":"welding-in-the-world","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"witw","sideBox":"Learn more about [Welding in the World](https://www.springer.com/journal/40194)","snPcode":"40194","submissionUrl":"https://www.editorialmanager.com/witw/","title":"Welding in the World","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"high-speed train, weathering steel, corrosion resistance, toughness, Cr, weld metal","lastPublishedDoi":"10.21203/rs.3.rs-4744193/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4744193/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThe effects of Cr content on the microstructure, mechanical properties and corrosion behavior of two weld metals containing Ti or Mo in the Ni-Cu alloy system for high-speed train bogies were studied. The results show that: In the weld containing Ti, Cr increases the acicular ferrite by about 15%, decreases the GF and FS, and slightly increases the M-A constituents. the effect of Cr on toughness is not obvious. In the weld containing Mo, Cr almost did not change the acicular ferrite content, resulted in a decrease in GF and an increase in FS, and a substantial increase in M-A constituents in the as-welded zone (0.4\u0026ndash;2.5%). Cr reduces weld toughness due to increase the proportion and size of M-A constituents and coarsen inclusions, the impact energy at -40℃ and \u0026minus;\u0026thinsp;60℃ decreases by 44J and 16J respectively. For the corrosion resistance, the initial corrosion rate of Mo-containing welds is reduced by addition of Cr, mainly due to the formation of MnS on the inclusions, which absorbs Cr, is suppressed, MnS is easily dissolved. While in Ti-containing weld this effect is weakened. In addition, Cr densifies the inner and outer rust layers and then reduces the corrosion rate of weld rust layers.\u003c/p\u003e","manuscriptTitle":"Effect of Cr content on microstructure, mechanical properties and corrosion behavior of weld metal in weathering steel of high-speed train bogie","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-08-16 05:20:54","doi":"10.21203/rs.3.rs-4744193/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"reviewerAgreed","content":"","date":"2024-07-23T08:53:35+00:00","index":0,"fulltext":""},{"type":"reviewersInvited","content":"","date":"2024-07-22T12:32:52+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"Welding in the World","date":"2024-07-18T13:56:05+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2024-07-18T13:07:07+00:00","index":"","fulltext":""},{"type":"submitted","content":"Welding in the World","date":"2024-07-18T07:52:16+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"welding-in-the-world","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"witw","sideBox":"Learn more about [Welding in the World](https://www.springer.com/journal/40194)","snPcode":"40194","submissionUrl":"https://www.editorialmanager.com/witw/","title":"Welding in the World","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"eb7e7999-ebcc-4bc9-a856-40545570c426","owner":[],"postedDate":"August 16th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2024-10-09T12:15:56+00:00","versionOfRecord":[],"versionCreatedAt":"2024-08-16 05:20:54","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-4744193","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4744193","identity":"rs-4744193","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}