Effect of feed rate during induction hardening on the hardening depth, microstructure, and wear properties of tool-grade steel work roll

Effect of feed rate during induction hardening on the hardening depth, microstructure, and wear properties of tool-grade steel work roll | 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 feed rate during induction hardening on the hardening depth, microstructure, and wear properties of tool-grade steel work roll Alen Sapek, Mitjan Kalin, Crtomir Donik, Matjaz Godec, Bostjan Markoli This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4597879/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 27 Nov, 2024 Read the published version in Journal of Materials Science: Materials in Engineering → Version 1 posted You are reading this latest preprint version Abstract Rolls are the most critical yet vulnerable parts of cold rolling mills. It is crucial for them to withstand long rolling campaigns without losing surface roughness or incurring damage. The newly developed rolls are made from tool-grade steel with high roughness, lower wear, and high damage resistance. One of the most important advantages is the elimination of the need for chrome plating, which is currently widely used on standard steel rolls but is ecologically harmful. We investigated type of steel with 8% Cr for use in cold rolling using LOM, XRD, SEM, electron backscatter diffraction (EBSD), hardness measurements, and tribological tests. In this study, a roll with a diameter of 325 mm was ESR remelted and forged, machined to a diameter of 305 mm, and quenched and tempered to simulate industrial roll production. A forged roll was induction heated and hardened at four different feed rates (i.e., 24 mm/min, 30 mm/min, 36 mm/min, and 42 mm/min), tempered at 515°C for 24 hours and again at 480°C for 24 hours, and dissected for in-depth analysis. We identified a clear relationship between the feed rate of the roll during induction hardening and the depth of hardness, the sizes of carbides, and the wear properties of the roll. By reducing the feed rate of the roll through the inductor, we increased the depth of the hardened layer from 16 mm (at a feed rate of 36 mm/min) to 25 mm (at a feed rate of 24 mm/min), which is a 56.25% increase expected to extend the lifespan of the working roll without having negative effects on the wear resistance and other important parameters. XRD analysis showed that the sample had a 0.4% residual austenite, which means it had a significantly lower risk of roll damage during operation than standard steel grades. Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 Figure 12 Figure 13 Figure 14 Figure 15 Figure 16 Introduction In “rolling,” materials are formed by rotating rolls. As a result, work rolls used in cold rolling mills are expected to have excellent wear resistance, be resilient to plastic deformation, and withstand mechanical and thermal shocks [ 1 – 5 ]. In addition, roll users are looking to reduce production costs while increasing productivity. In cold rolling mills, ensuring adequate surface roughness significantly impacts production costs and is improved by chrome plating after roll grinding and for standard steel grades [ 6 ]. Due to increasingly stringent environmental regulations and the environmental controversy surrounding chrome plating (very bad for the environment, uses toxic acid baths and may cause various health conditions), all development is focused on fabricating rolls made of tool- and high-speed steel grades that have a much higher ability than others to maintain adequate surface roughness and are much more “resistant” to incidents during cold rolling [ 7 – 8 ]. Cold work tool-grade steels have high wear resistance, toughness, dimensional stability, homogeneous microstructures, resistance to abrasive-adhesive wear, fatigue damage starting from the surface, and easy machinability in a pre-annealed structure [ 9 ]. Producing a wear-resistant yet smooth texture is only achievable through the adequate constitution of the surface and subsurface of rolls. Martensitic and/or martensitic-bainitic microstructures accompanied by hard complex carbides appear to be the best fit for the purpose of cold rolling rolls. We must ensure that the transition from hard and brittle surfaces to subsurfaces and subsequent portions of the rolls are continuous and without discontinuities. The use of a combined heat treatment method is required to produce a roll with optimal mechanical properties. The working layer of the roll is inductively heated and hardened (with low-temperature tempering on the level of hardness needed) while the roll’s core is quenched and tempered. Because standard rolls with 0.9% carbon content have eutectoid compositions, they contain a perceptible amount of retained austenite, a metastable phase. Our analyses results for premature roll failures show that retained austenite is one of the significant contributors. The results for spalled roll specimens indicated that higher life rolls contained minimally retained austenite (under 10%). Under high pressures during rolling, there is a risk of transformation of residual austenite and the subsequent formation of cracks, which can lead to the breakage of the roll. A subzero treatment is applied to the induction hardened layer to minimize retained austenite by putting it in liquid nitrogen [ 10 – 12 ]. The improvements after deep cryogenic treatment can be attributed to the transformation of retained austenite to martensite and further to increases in uniform and homogeneous carbide distribution with secondary carbide precipitation in the case of steels with secondary tempering peaks [ 13 ]. In addition to the other advantages of tool-grade steel over standard steel grades for the cold rolling of steel, it has a very low retained austenite content percentage; during the production processes of induction heating, hardening, and high-temperature tempering, retained austenite is transformed to martensite [ 14 ]. The presence of alloying elements such as molybdenum, chromium, vanadium, and tungsten in tool-grade steel lowers the temperature of the martensite start (Ms) and martensite finish (Mf), which are the temperatures that must be reached for the austenite phase to completely transform into the martensitic phase. On the contrary, materials should be fast-cooled from austenite to room temperature during heat treatment to avoid cracking due to temperature shocks. The presence of retained austenite in the hardening process of tool-grade steel often causes the steel to have lower hardness than required and poor dimensional stability [ 15 – 18 ]. Therefore, controlling heat treatment parameters such as feed rate (i.e., the speed at which the roll moves through the induction coil, which is measured in mm/min) during induction hardening is essential [ 19 – 21 ]. One must consider the current frequency and its effect on the penetration depth (i.e., the heating depth) of the rolls, as it is well known that the use of high current frequencies leads to low penetration depths and vice versa. In this case study, only the influence of the feed rate during induction hardening of tool-steel work rolls was analyzed. We found that it had effects on the microstructure and wear properties of working roll, such as higher hardness depth and slightly better wear resistance. The impact of current frequency was not studied; that is, we kept the frequency constant throughout our tests. Experimental work The simulation of induction hardening was performed with the Cenos software using a coupled electromagnetic-thermal model to describe the induction heating process. We used preselected dimensions and temperature, frequency, power, and material parameters that are commonly used to produce industrial work rolls and apply different feed rates. Cold work steel with 8% Cr was selected to produce the test rolls. Chemical composition is presented in Table 1 . The steel was made in an electric arc furnace, degassed in a vacuum, and remelted by electro-slag remelting process to obtain optimum properties. The ESR ingot was forged into a roll blank with dimensions of diameter 325 mm by length 1,700 mm by 2,740 mm and then soft annealed. Table 1 Composition of 8% Cr cold-work tool steel roll blank C Si Mn P S Cr Mo V W 0.93 0.96 0.34 0.015 0.006 7.56 1.45 2.010 0.86 The blank was machined and heat treated (i.e., quenched and tempered) to 900–1,000 N/mm 2 (i.e., the standard value for the production of rolls, which is equal to a hardness range of 27–32 HRc for the barrel and neck). After the first heat treatment, the blank was machined again to a diameter of 305 mm. Induction hardening was performed on the blank by heating it to an austenitizing temperature of 1,080°C and rapidly cooling it in water. As described in Table 2 and shown in Fig. 1, much higher power as usual is required to achieve the consistent austenitizing temperature and frequency. For example, disc 1 was hardened at a feed rate of 24 mm/min with a power of 210 kW, and when hardening disc 4 at a feed rate of 42 mm/min, a much higher power (370 kW) was required. In all our tests, the frequency was kept constant (varying from 355 to 358 Hz), yet the induction hardening machine automatically increased power during higher feeding rates to control the frequency constant. Table 2 Selected feed rate and actual induction hardening parameters Sample name Feed rate [mm/min] Time at austenitization temperature [min] Austenitization temperature [°C] Frequency [Hz] Power [%] Power [kW] Disc 1 24 7.5 1080 355 60 210 Disc 2 30 6 357 75 300 Disc 3 36 5 358 77 340 Disc 4 42 4.3 357 86 370 After induction hardening and tempering were applied to it, the roll was tempered at 515°C for 24 hours, followed by further tempering at 480°C for 24 hours. After heat treatment finalization, specimens were cut from a roll (as shown in Fig. 2 ) using EDM (Electro Discharge Machining) to prevent any possible influence on the microstructure and other properties, ground, and polished for metallographic characterization. Methods First, macro hardness on all four discs with different feed rates was measured using a Rockwell hardness tester. For each sample, ten measurements were performed per position. We used an Axio Imager A1m with an AxioCam ICc 3 digital camera and AxioVision software to classify carbides by size. For this purpose, we used ImageJ software, which can be used to calculate area and pixel value statistics for user-defined selections and intensity-thresholded objects. It can also be used to measure distances and angles. The microstructure was revealed by SEM while the composition of the carbides was determined by energy-dispersive X-ray spectroscopy (EDS). The crystal structures of the phases present in the roller discs were revealed (characterized) via EBSD. The samples were mounted in conductive Bakelite conductive resin and then carefully ground and polished. SEM was performed using a JEOL JSM − 7600F field emission scanning electron microscope with an Oxford Instruments INCA microanalysis suite, an X-Max 20 SDD-EDS detector, and CHANNEL5 EBSD software with a Nordlys detector. For EDS and EBSD analysis, we used a Zeiss CrossBeam 550 FIBSEM field emission scanning electron microscope (Germany) equipped with an EDAX Hikari Super EBSD camera and EDAX APEX software. The following parameters were adjusted to achieve the most accurate results: a 15-kV accelerating voltage and 2.0–5.0 nA probe current for SE images and EDS analyses and 70°-tilted samples and a 7.0-nA probe current for EBSD analyses on 18 mm WD. XRD analysis was performed on a Bruker D8 Advance diffractometer with a scintillation NaI detector. The identification of individual peaks in the radiographs was performed with the program Match v.1.9h, Crystal Impact, Germany, and using PDF2 data 00-006-0696 for alpha Fe and 00-023-0298 for gamma Fe from the ICDD 2006 database. The content of retained austenite (RA-Retained Austenite, in vol.%) was calculated using Rietveld methods and use of PowderCell v.2.4. The basic principle of the Rietveld method is comparison of the measured diffractogram with the calculated one. The process is carried out until the best match is obtained (best fit). Tribological tests were performed using the pin-on-disc method, which was used due to the ability to control the conditions, reproducibility, quantitative data, and simulation of real-world mechanical interactions. Tests were performed at room temperature because we were using steel grades for cold rolling under the following conditions: a frequency of 1 Hz, a stroke length of 10.6 mm, applied loads of 1 GPa, 1.3 GPa, and 1.7 GPa, 1,800 cycles, and test duration of 30 minutes. The ball (counter body) was made of standard 100Cr6 steel with a diameter of 10 mm, and the discs had a surface roughness of 0.1 Ra. Results and discussion The Cenos simulation of induction heating showed that there were significant differences in the hardening depth, but the influence on the microstructure and wear properties could not be simulated. Figure 3 shows that there were substantial changes in the temperature-depth along the diameter of the individual roll depending on the feeding rate. The feed rate seems to be a decisive factor in determining the hardening depth related to the temperature at any given position of the individual roll. When we increased the feeding rate from 24 to 42 mm/min, the temperature-depth decreased as the thermal energy transferred, which is heavily related to the electrical current frequency used in this experiment. Figure 4 shows that in each disc from 1 to 4, the hardening depth ranges from 45 to 60 mm for the lowest feeding rate of 24 mm/min. On the contrary, the surface hardness varies only within the magnitude of a few HRc (i.e., from around 58 HRc for the feed rate of 36 mm/min to 62 HRc for the feed rate of 24 mm/min, which is the lowest). Additionally, the decrease in the hardening depth and hardness itself, as depicted by the curves in different colors, shows that in the case of the lowest feed rate, the decrease was less steep and more continuous than that in the case of the highest feed rate. Table 3 shows the hardness depth measurements from a stationary Rockwell tester. Disc 1, which had a feed rate of 24 mm/min and an austenitizing temperature of 7.5 minutes, had a hardness depth of 50 mm according to the standard DIN 10328, or 25 mm according to the usual customer requirements in the roll industry. For disc 2, which had a 30 mm/min feed rate, the hardness depth was measured at 46 mm according to DIN 10328 and 22 mm according to standard customer requirements. Disc 3, which had a feed rate of 36 mm/min, had a hardening depth of 41 mm according to DIN 10328 and 16 mm according to standard customer requirements. Table 3 Hardening depth measurements Feed rate [mm/min] Time at austenitization temperature [min] Hardening depth acc. to DIN 10328 [mm] Hardening depth acc. to customer requirements (min. 58 HRc) [mm] Disc 1 24 7.5 50 25 Disc 2 30 6 46 22 Disc 3 36 5 41 16 Disc 4 42 4.3 38 16 The same hardness depth according to standard customer requirements was also measured on disc 4 with a feed rate of 42 mm/min, but there is a difference in hardness depth according to DIN 10328, with disc 4 having a 3 mm lower hardness depth compared to disc 3 with feed rate 36 mm/min. With the results of the hardness measurements in mind, we turned to SEM to determine and evaluate the condition of the tested rolls on the microscale before and after induction hardening. SEM was performed on specimens from all four discs. During the microscopic examination, we discovered significant differences in the samples’ microstructures, which were mainly composed of the martensitic matrix and primary and secondary carbides. Images of the microstructure are shown in Fig. 5. However, despite the significant differences in microstructure associated with carbide streaks, we did not find substantial variations in hardness between all four specimens. See Fig. 6 . Table 4 shows the chemical compositions of various strains. As can be seen from the table, the matrix (i.e., Spectra 9 and 10) has almost the same chemical composition as that in Table 1 , while the carbides have two different chemical compositions: the first group contains 27.20–34.62% Cr, 10.79–23.77% V, 3.10–5.76% Mo, and 1.17–3.09% W, while the second group or grade contains 6.79–7.96% Cr, 41.48–55.18% V, 5.09–6.31% Mo, and 4.19–9.99% W. Table 4 Chemical composition of spots on disc 1 with feed rate 24 mm/min Spectrum Label Spectrum 1 Spectrum 2 Spectrum 3 Spectrum 4 Spectrum 5 Spectrum 6 Spectrum 7 Spectrum 8 Spectrum 9 Spectrum 10 C 23.21 23.95 18.46 19.86 23.16 19.07 19.59 23.86 Si 1.03 1.02 Ti 0.36 0.95 0.60 1.27 V 55.18 53.99 23.77 59.05 41.48 11.95 10.79 50.31 0.76 1.03 Cr 7.53 6.97 27.20 7.39 7.96 34.66 34.62 6.98 6.79 7.13 Mn 0.44 0.48 Fe 2.20 4.26 21.72 1.83 2.30 29.73 30.70 8.30 88.92 88.23 Mo 6.31 5.32 5.76 6.05 15.11 3.41 3.10 5.09 1.05 1.40 W 5.20 4.55 3.09 5.21 9.99 1.17 1.20 4.19 1.01 0.70 Total 100.00 100.00 100.00 100.00 100.00 100.00 100.00 100.00 100.00 100.00 The compositions of different streaks of carbides revealed that there were at least two groups of complex carbides present in the samples. One group was based on chromium, and the other was based on vanadium. Both groups contain at least three to four other chemical elements, adding to the hardness of the examined rolls. The carbon content has not been accounted for in the EDS analysis presented in Table 1 . Nevertheless, based on our previous knowledge of the formation of carbides in complex steels, we can classify the first group of carbides as the (Cr, V, Mo, W) x C y type and the second group as the (V, Cr, Mo, W) x C y complex type of carbides, actually expecting MC and M 7 C 3 type of carbides as it will be shown later. The first group of carbides is based on chromium while the other is based on vanadium. Both elements, along with some others, are known to be very potent elements for the formation of carbides. Of course, the carbides are not the only microstructural constituents that influence the properties of the steel. The constitution of the matrix of the investigated steel can have significant impacts on the properties of the steel. Therefore, we turned our attention to the EDS analyses and the distribution of the elements in the carbides and the matrixes of the investigated steel. Figure 7 shows the overall EDS plot on the sample from disc 1 at a feed rate of 24 mm/min, confirming the presence of two main types of carbides. The distribution of the individual alloying elements is shown in Fig. 8. Using light microscopy, we analyzed 200 individual spots on samples from discs 1–4 and measured the average size of the carbides (see Fig. 9). Our analysis results for carbide sizes, which are shown in Fig. 10 and Table 5 , revealed that the largest average carbide size was present in the samples from disc 1, which had a feed rate of 24 mm/min, and the smallest average carbide size was present in the samples from disc 4, which had a feed rate of 42 mm/min. Table 5 Average size of carbides – image size 548.91x410.33 µm Disc 1 with feed rate 24 mm/min Disc 2 with feed rate 30 mm/min Disc 3 with feed rate 36 mm/min Disc 4 with feed rate 42 mm/min Average size of carbide [µm 2 ] 2.265 2.163 2.018 1.843 When we analyzed the size of carbides in the range of 0–1 µm 2 , we found that the samples of disc 1 with a feed rate of 24 mm/min had the smallest average carbide size. The analyses of the sizes of carbides in the 1–5-µm 2 range showed that the carbides in the samples from disc 1 with a feed rate of 24 mm/min had the largest size, confirming the presence of the Ostwald ripening process. This led to the supersaturation of the matrix, which together with the feed rate, affects the shape of carbides. The specimens from disc 1 were hardened at a lower feed rate compared to other three discs, giving the carbides additional time to develop and become spherical (the carbides become more rounded), and the smaller ones dissolved. When measuring the macro hardness, we found that the microhardness was the highest in the sample from disc 1 with a feed rate of 24 mm/min and the lowest in the sample of disc 4 with a feed rate of 42 mm/min, which was hardened at the highest feed rate. Because we identified two types of carbide, we wanted to determine which types of carbide they were. For this purpose, we used the well-established EBSD technique, and the results are presented in Figs. 11 and 12 , with the EBSD IPF Z map and the phase for the confirmation of the proposed phases shown. The analysis results confirmed the presence of two main types of carbides in the sample, namely MC and M 7 C 3 . The IPF Z map shows the typical microstructure of martensitic steel with needle-like structures and carbides in the matrix. In contrast, the phase map shows the martensitic bcc phase in yellow, M 7 C 3 in green and MC in red. Figure 12 contains an EDS map of the same spot as EBSD, where different amounts of elements (e.g., Cr, Fe, V, W, Mo, and C) in the carbides and the matrix so it can corroborate the different carbides have an additional amount of alloying element. X-ray diffraction was performed on samples after induction heating and hardening and first and second tempering to confirm the theory that they had lower residual austenite content than in the production of rolls from standard grades. Figure 13 shows the X-ray diffraction pattern of the sample from disc 1 with a feed rate of 24 mm/min after second tempering at 480°C for 24 hours. The sample contained 99.6% martensite and 0.4% austenite. The XRD results are presented in Table 6 . The content of retained austenite (RA-Retained Austenite, in vol.%) was calculated using Rietveld methods and use of PowderCell v.2.4 software. Table 6 Measurements of RA on a sample from disc 1 with a feed rate of 24 mm/min Process Measured content of RA [%] Induction heating and hardening 12.70 Tempering 1–515°C/24 h 1.00 Tempering 2–480°C/24 h 0.40 Tribological tests that involved using the pin-on-the-disc method gave us clear information about wear volume and specific wear rate of all discs with different feed rates. We applied other loads with 1,800 cycles per specimen. The wear volume and specific wear rate were lowest for disc 1 with a 24 mm/min feed rate. However, the differences in wear were minimal and are more correlated to material homogeneity and its local characteristics, as presented in Figs. 14 and 15 . The wear volume and specific wear rate of a ball made of 100Cr6 steel were highest on the disc with a 24 mm/min feed rate. The specific wear rate was found to be highest at a feed rate of 24 mm/min for all three loads. Furthermore, the specific wear rate decreases as the feed rate increases. As we increased the load for the feed rate of 24 mm/min, the counter body penetrated deeper into the surface of the sample, leaving a narrower track with a lower specific wear rate. On the contrary, the specific wear rate decreased when an increasing feed rate was used and appeared to be similar at the 36 and 42 mm/min feed speeds. We hypothesize that this is due to the lower amount of annealing of the matrix that occurred at the lower feed rates, which generated the heat required to anneal the iron-based matrix. Again, the observed differences from other discs were minor and do not represent significant improvements regarding wear resistance. Images of wear are presented in Fig. 16. Conclusions Induction hardening was performed by heating a tool-steel roll to an austenitizing temperature of 1,080°C, followed by rapid cooling in water. When high feed rates are used, higher power is needed to achieve technologically prescribed austenitizing temperature and frequency. For example, disc 1 was hardened at a feed rate of 24 mm/min with a power of 210 kW, and when hardening disc 4 at a feed rate of 42 mm/min, a much higher power was needed, 370 kW. Disc 1, with a feed rate of 24 mm/min and 7.5 minutes at austenitizing temperature, had a hardening depth of 50 mm according to the standard DIN 10328 (i.e., a minimum of 80% of surface hardness) or 25 mm according to legal customer requirements in the roll industry (i.e., a hardness drop for max. 2 HRc). For disc 2, with a feed rate of 30 mm/min, a hardness depth of 46 mm was measured according to DIN 10328 and 22 mm according to standard customer requirements. Disc 3, with a feed rate of 36 mm/min, was found to have a hardening depth of 41 mm according to DIN 10328 and 16 mm according to standard customer requirements. The same hardening depth according to standard customer requirements was also measured for disc 4 with a 42 mm/min feed rate. Still, there is a difference in the hardening depth according to DIN 10328, with disc 4 having a 3 mm lower hardening depth than disc 3. This shows us that the feed rate significantly influences the hardening depth because the hardening depth is much deeper at low feed rates than when hardening tool-steel work rolls at high feed rates. Our SEM and EDS analysis results revealed two main chemical compositions of the MC carbides. Using the EBSD technique, we confirmed the presence of two types of carbides in our 8% Cr steel: MC and M 7 C 3 . We identified the largest average carbide size in the samples for disc 1 with a feed rate of 24 mm/min and the smallest average carbide size in the samples for disc 4 with a feed rate of 42 mm/min. The average carbide size was highest on disc 1 with a feed rate of 24 mm/min and a size of 2,265 µm 2 and lowest on disc 4 with a feed rate of 42 mm/min with an average size of 1,843 µm 2 . This confirms the Ostwald ripening process, which leads to a supersaturation of the Fe-based matrix, which together with the feed rate, influences the shape of the carbides. The samples from disc 1 were hardened at a lower feed rate, giving the carbides time to spheroidize and grow (the carbides increased in sphericity), while the small carbides dissolved. The sample with the highest macro hardness was from disc 1 with a feed rate of 24 mm/min and the lowest for the sample from disc 4 with a feed rate of 42 mm/min, which was hardened at the highest feed rate. XRD presented us with detailed information about the crystallographic structure of discs, hardened with different feed rates. After induction heating and hardening, there was 12.7% retained austenite (RA) and 87.3% martensite. After the first tempering at 515°C for 24 hours, the RA content decreased to 1.2%, and after the second tempering at 480°C for 24 hours, the RA content further decreased to 0.4%. This confirms the theory that rolls produced from tool-grade steels contain much lower RA content and are much safer to use than standard-grade rolls. Tribological studies on all four discs, hardened with different feed rates, have shown that disc 1, with a 24 mm/min feed rate, has slightly better wear resistance. Still, initial differences in material homogeneity or local features in the material have a more significant influence on the material’s wear resistance than the change in feed rate during induction hardening. Declarations Ethics approval and consent to participate Not applicable Consent for publication Not applicable Availability of data and materials The authors confirm that the data supporting the findings of this study are available within the article its supplementary materials. Competing interests The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper Funding No funds, grants, or other support was received. Authors' contributions Sapek organized the research work and performed the measurements on industrial level. B. Markoli helped us with LOM, interpretation of the results and work on the manuscript. M. Kalin was working on the tribological studies. Č. Donik and M. Godec were responsible for work on SEM and EBSD, and interpretation of results. Acknowledgements Not applicable Authors' information (optional) Not applicable References Sychterz, J. Improved roll performance and elimination of chrome plating using forged semi high-speed steel roll materials in cold rolling application. Rolls 5 Conference, 22–24 April 2015, Birmingham (UK). McCann, J. (April 1999). An overview of work rolls for cold rolling; Rolls 2000+ . 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Evolution of Carbides in Cr-Mo‐Si‐V Alloy Steel during Spheroidization Annealing Process. steel research international. 91. 10.1002/srin.201900287 . Krapivina, P., & Gervasyev, M. (2019). Determining the Optimum Conditions for Heat Treatment of Cold Rolling Mill Rolls by Studying Their Influence on the Microstructure and Properties of the Billet. Journal of Siberian Federal University Engineering & Technologies , 449–459. 10.17516/1999-494X-0152 . Kim, H., Kang, J. Y., Son, D., Lee, D., Lee, T. H., Jeong, Woo, & Cho, K. M. (2014). Microstructures and Mechanical Properties of Cold-Work Tool Steels: A Comparison of 8%Cr Steel with STD11. Journal of the Korean Society for Heat Treatment , 27 , 242–252. 10.12656/jksht.2014.27.5.242 . Prisco, U. (2018). Case microstructure in induction surface hardening of steels: an overview. The International Journal of Advanced Manufacturing Technology , 98 . 10.1007/s00170-018-2412-0 . Kohli, A., & Singh, H. (2011). Optimization of processing parameters in induction hardening using response surface methodology. Sadhana-academy Proceedings in Engineering Sciences - SADHANA-ACAD PROC ENG SCI. 36. 141–152. 10.1007/s12046-011-0020-x . Cite Share Download PDF Status: Published Journal Publication published 27 Nov, 2024 Read the published version in Journal of Materials Science: Materials in Engineering → Version 1 posted 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-4597879","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":321528483,"identity":"3d63658b-1522-4409-a120-bc6b438de477","order_by":0,"name":"Alen Sapek","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAxklEQVRIiWNgGAWjYNCCAzZAnNjAkECCljSQlsYGUrQcBuIExgaiFPP3H3724MOZ8/J8x5PbHzyoYJAzOEBAi8SNNHPDGTduG8488xDosDMMxgS1MNxgMJPm+XCbccMNoF8S2xgSNxDSIn/++DfpPx/O2cO01BPUYnAgx0ya4caBRJiWBIIOM7yRU27YcyY5GeSXGQlnJAxnEtIid/74tgc/jtnZ9h1Pf/DxR4WNPB8hLUDAhsyRIKweXcsoGAWjYBSMAkwAAAQaUY65i97iAAAAAElFTkSuQmCC","orcid":"https://orcid.org/0000-0003-4027-2919","institution":"Additio d.o.o.","correspondingAuthor":true,"prefix":"","firstName":"Alen","middleName":"","lastName":"Sapek","suffix":""},{"id":321528484,"identity":"c0c39d24-7cdb-4409-b033-436a67690cef","order_by":1,"name":"Mitjan Kalin","email":"","orcid":"","institution":"University of Ljubljana Faculty of Mechanical Engineering: Univerza v Ljubljani Fakulteta za strojnistvo","correspondingAuthor":false,"prefix":"","firstName":"Mitjan","middleName":"","lastName":"Kalin","suffix":""},{"id":321528485,"identity":"fa391744-2402-4c18-b497-c578a8d0d5cc","order_by":2,"name":"Crtomir Donik","email":"","orcid":"","institution":"IMT: Institut za kovinske materiale in tehnologije","correspondingAuthor":false,"prefix":"","firstName":"Crtomir","middleName":"","lastName":"Donik","suffix":""},{"id":321528486,"identity":"ec7d396b-21a5-49cb-9a77-afb01c70de2d","order_by":3,"name":"Matjaz Godec","email":"","orcid":"","institution":"IMT: Institut za kovinske materiale in tehnologije","correspondingAuthor":false,"prefix":"","firstName":"Matjaz","middleName":"","lastName":"Godec","suffix":""},{"id":321528487,"identity":"eb4e0d7e-3b09-4620-a9cf-30d2949674ef","order_by":4,"name":"Bostjan Markoli","email":"","orcid":"","institution":"University of Ljubljana Faculty of Natural Sciences and Engineering: Univerza v Ljubljani Naravoslovnotehniska Fakulteta","correspondingAuthor":false,"prefix":"","firstName":"Bostjan","middleName":"","lastName":"Markoli","suffix":""}],"badges":[],"createdAt":"2024-06-18 06:48:30","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-4597879/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-4597879/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1186/s40712-024-00193-5","type":"published","date":"2024-11-27T15:57:25+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":60978707,"identity":"44516e41-8db1-4b1f-86d6-e6061be6f956","added_by":"auto","created_at":"2024-07-24 08:42:10","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":1045413,"visible":true,"origin":"","legend":"\u003cp\u003ea) Test roll during preheating b) Test roll during induction hardening (use of protective metal blanket)\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-4597879/v1/ae0c453dc5c538f364a0af00.png"},{"id":60977743,"identity":"f99560b4-aebf-4799-b348-a470b7fd7258","added_by":"auto","created_at":"2024-07-24 08:34:09","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":146159,"visible":true,"origin":"","legend":"\u003cp\u003eIndustrial roll D305x1700 mm, hardened with different feed rates; discs 1, 2, 3, 4 with sample positions for hardening depth and wear properties determination.\u003c/p\u003e","description":"","filename":"2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4597879/v1/ec8541e7cc01ef4a876e37fe.jpg"},{"id":60977738,"identity":"a3311e65-f94a-4fd6-8a0e-7713ac7bb9d1","added_by":"auto","created_at":"2024-07-24 08:34:09","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":223638,"visible":true,"origin":"","legend":"\u003cp\u003eSimulation of induction hardening with various feeding rates: 1) Disc with feed rate 24 mm/min, 2) Disc with feed rate 30 mm/min, 3) Disc with feed rate 36 mm/min, 4) Disc with feed rate 42 mm/min\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-4597879/v1/e8d250d712d6f38962fe0353.png"},{"id":60978698,"identity":"cfc70926-a00c-4974-bc6f-9e50ab5de50e","added_by":"auto","created_at":"2024-07-24 08:42:09","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":54899,"visible":true,"origin":"","legend":"\u003cp\u003eHardening depth on discs 1-4 with feed rate 24-42 mm/min\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-4597879/v1/40d55c0e76240518fe772686.png"},{"id":60979390,"identity":"e6bcd468-2e7c-4c5f-be1f-b4b32253d7a5","added_by":"auto","created_at":"2024-07-24 08:50:09","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":817954,"visible":true,"origin":"","legend":"\u003cp\u003eScanning electron microscope images: 5a) \u0026nbsp;\u0026nbsp;microstructure on a sample from disc 1 with feed rate 24 mm/min 5b) \u0026nbsp;\u0026nbsp;microstructure on a sample from disc 2 with feed rate 30 mm/min 5c) \u0026nbsp;\u0026nbsp;microstructure on a sample from disc 3 with feed rate 36 mm/min 5d) \u0026nbsp;\u0026nbsp;microstructure on a sample from disc 4 with feed rate 42 mm/min\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-4597879/v1/2a9ffae6ab72624f031afcd0.png"},{"id":60978708,"identity":"eed309ca-fccd-4bd3-ad61-8ac0be270e33","added_by":"auto","created_at":"2024-07-24 08:42:11","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":235818,"visible":true,"origin":"","legend":"\u003cp\u003eSample from disc 1 with feed rate 24 mm, where several spots were analyzed with the use of EDS\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-4597879/v1/b0b00c07a3b675c8e995f4ba.png"},{"id":60978701,"identity":"c59c6e54-39ea-47f0-b607-695482f7eabe","added_by":"auto","created_at":"2024-07-24 08:42:09","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":236877,"visible":true,"origin":"","legend":"\u003cp\u003eOveral EDS mapping on a sample from disc 1 with feed rate 24 mm/min\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-4597879/v1/c4ffa5670203b019bac94580.png"},{"id":60977740,"identity":"7174db09-d4bd-413a-a9cb-a12e5182fc9f","added_by":"auto","created_at":"2024-07-24 08:34:09","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":424516,"visible":true,"origin":"","legend":"\u003cp\u003eEDS mapping of elements on a sample from disc \u0026nbsp;\u0026nbsp;1 with feed rate 24 mm/min\u003c/p\u003e","description":"","filename":"8.png","url":"https://assets-eu.researchsquare.com/files/rs-4597879/v1/481b0689610de58ff07e31ad.png"},{"id":60979392,"identity":"ae43353f-4601-4ddb-bcb0-e55c8798d7f2","added_by":"auto","created_at":"2024-07-24 08:50:09","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":823924,"visible":true,"origin":"","legend":"\u003cp\u003ea) Sample for disc 1 with feed rate 24 mm/min, size 548,91x410,33 µm, before calibration in program ImageJ b) same sample after calibration in program ImageJ c) measurement of the size of carbides on the same sample\u003c/p\u003e","description":"","filename":"9.png","url":"https://assets-eu.researchsquare.com/files/rs-4597879/v1/9d7640a6cc0cb99289bc42ab.png"},{"id":60977735,"identity":"5870fb95-1aa3-4e67-8787-aef233804143","added_by":"auto","created_at":"2024-07-24 08:34:09","extension":"png","order_by":10,"title":"Figure 10","display":"","copyAsset":false,"role":"figure","size":45712,"visible":true,"origin":"","legend":"\u003cp\u003eTable with the average size for all four discs\u003c/p\u003e","description":"","filename":"10.png","url":"https://assets-eu.researchsquare.com/files/rs-4597879/v1/cab5d4382f1124ed63c9d517.png"},{"id":60977750,"identity":"186915f6-b38f-4f09-9cac-a21aab9797da","added_by":"auto","created_at":"2024-07-24 08:34:10","extension":"png","order_by":11,"title":"Figure 11","display":"","copyAsset":false,"role":"figure","size":1168322,"visible":true,"origin":"","legend":"\u003cp\u003eEBSD analysis in the sample from disc 1 with feed rate 24 mm/min\u003c/p\u003e","description":"","filename":"11.png","url":"https://assets-eu.researchsquare.com/files/rs-4597879/v1/07c85531207dbd25e9c471f8.png"},{"id":60980020,"identity":"5c4f81d5-0103-475b-ad75-64d11e149c98","added_by":"auto","created_at":"2024-07-24 08:58:09","extension":"png","order_by":12,"title":"Figure 12","display":"","copyAsset":false,"role":"figure","size":919353,"visible":true,"origin":"","legend":"\u003cp\u003eEDS mapping of alloying elements in the microstructure of disc 1 with feed rate 24 mm/min\u003c/p\u003e","description":"","filename":"12.png","url":"https://assets-eu.researchsquare.com/files/rs-4597879/v1/3dfb4608dcc58c78aa289a92.png"},{"id":60980019,"identity":"f1af7650-fdc3-4eea-bb41-a01ae9ba3831","added_by":"auto","created_at":"2024-07-24 08:58:09","extension":"png","order_by":13,"title":"Figure 13","display":"","copyAsset":false,"role":"figure","size":95419,"visible":true,"origin":"","legend":"\u003cp\u003eThe result of the Rietveld analysis of the sample from disc 1 with feed rate 24 mm/min\u003c/p\u003e","description":"","filename":"13.png","url":"https://assets-eu.researchsquare.com/files/rs-4597879/v1/710cd974734e29ed3ef21ba9.png"},{"id":60979394,"identity":"731b6619-66a6-4dac-ae9a-1a265d8db1c9","added_by":"auto","created_at":"2024-07-24 08:50:09","extension":"png","order_by":14,"title":"Figure 14","display":"","copyAsset":false,"role":"figure","size":369344,"visible":true,"origin":"","legend":"\u003cp\u003eWear volume and specific wear rate of disc sample from disc 1 with feed rate 24 mm/min\u003c/p\u003e","description":"","filename":"14.png","url":"https://assets-eu.researchsquare.com/files/rs-4597879/v1/1758b875a91662b70ed86d46.png"},{"id":60980021,"identity":"fa7ca359-8cba-41a8-9df0-31e25329f67c","added_by":"auto","created_at":"2024-07-24 08:58:10","extension":"png","order_by":15,"title":"Figure 15","display":"","copyAsset":false,"role":"figure","size":414219,"visible":true,"origin":"","legend":"\u003cp\u003eWear volume and specific wear rate of the ball from 100Cr6 with 10 mm diameter\u003c/p\u003e","description":"","filename":"15.png","url":"https://assets-eu.researchsquare.com/files/rs-4597879/v1/dfde631125c4f9f0fbe9663f.png"},{"id":60978706,"identity":"433cb2d8-2532-41de-ad8a-590239fcf029","added_by":"auto","created_at":"2024-07-24 08:42:10","extension":"png","order_by":16,"title":"Figure 16","display":"","copyAsset":false,"role":"figure","size":1116127,"visible":true,"origin":"","legend":"\u003cp\u003ea,b,c) Wear of disc 1 with feed rate 24 mm/min after test, loads 1 GPa, 1,3 GPa and 1,7 GPa\u003c/p\u003e\n\u003cp\u003ee,d,f) Sample of wear on balls used against a sample from disc 1 with feed rate 24 mm/min after test, loads 1 GPa, 1,3 GPa, and 1,7 GPa\u003c/p\u003e","description":"","filename":"16.png","url":"https://assets-eu.researchsquare.com/files/rs-4597879/v1/7dfca705752af41caea89fb5.png"},{"id":70388762,"identity":"20770734-ab0e-42b5-8382-b1ff48689971","added_by":"auto","created_at":"2024-12-02 17:27:06","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":8633658,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4597879/v1/b081800d-ebba-44a6-b3fe-6c45c9d40603.pdf"}],"financialInterests":"","formattedTitle":"Effect of feed rate during induction hardening on the hardening depth, microstructure, and wear properties of tool-grade steel work roll","fulltext":[{"header":"Introduction","content":"\u003cp\u003eIn \u0026ldquo;rolling,\u0026rdquo; materials are formed by rotating rolls. As a result, work rolls used in cold rolling mills are expected to have excellent wear resistance, be resilient to plastic deformation, and withstand mechanical and thermal shocks [\u003cspan additionalcitationids=\"CR2 CR3 CR4\" citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. In addition, roll users are looking to reduce production costs while increasing productivity. In cold rolling mills, ensuring adequate surface roughness significantly impacts production costs and is improved by chrome plating after roll grinding and for standard steel grades [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. Due to increasingly stringent environmental regulations and the environmental controversy surrounding chrome plating (very bad for the environment, uses toxic acid baths and may cause various health conditions), all development is focused on fabricating rolls made of tool- and high-speed steel grades that have a much higher ability than others to maintain adequate surface roughness and are much more \u0026ldquo;resistant\u0026rdquo; to incidents during cold rolling [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. Cold work tool-grade steels have high wear resistance, toughness, dimensional stability, homogeneous microstructures, resistance to abrasive-adhesive wear, fatigue damage starting from the surface, and easy machinability in a pre-annealed structure [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. Producing a wear-resistant yet smooth texture is only achievable through the adequate constitution of the surface and subsurface of rolls. Martensitic and/or martensitic-bainitic microstructures accompanied by hard complex carbides appear to be the best fit for the purpose of cold rolling rolls. We must ensure that the transition from hard and brittle surfaces to subsurfaces and subsequent portions of the rolls are continuous and without discontinuities. The use of a combined heat treatment method is required to produce a roll with optimal mechanical properties. The working layer of the roll is inductively heated and hardened (with low-temperature tempering on the level of hardness needed) while the roll\u0026rsquo;s core is quenched and tempered.\u003c/p\u003e \u003cp\u003eBecause standard rolls with 0.9% carbon content have eutectoid compositions, they contain a perceptible amount of retained austenite, a metastable phase. Our analyses results for premature roll failures show that retained austenite is one of the significant contributors. The results for spalled roll specimens indicated that higher life rolls contained minimally retained austenite (under 10%). Under high pressures during rolling, there is a risk of transformation of residual austenite and the subsequent formation of cracks, which can lead to the breakage of the roll. A subzero treatment is applied to the induction hardened layer to minimize retained austenite by putting it in liquid nitrogen [\u003cspan additionalcitationids=\"CR11\" citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. The improvements after deep cryogenic treatment can be attributed to the transformation of retained austenite to martensite and further to increases in uniform and homogeneous carbide distribution with secondary carbide precipitation in the case of steels with secondary tempering peaks [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eIn addition to the other advantages of tool-grade steel over standard steel grades for the cold rolling of steel, it has a very low retained austenite content percentage; during the production processes of induction heating, hardening, and high-temperature tempering, retained austenite is transformed to martensite [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. The presence of alloying elements such as molybdenum, chromium, vanadium, and tungsten in tool-grade steel lowers the temperature of the martensite start (Ms) and martensite finish (Mf), which are the temperatures that must be reached for the austenite phase to completely transform into the martensitic phase. On the contrary, materials should be fast-cooled from austenite to room temperature during heat treatment to avoid cracking due to temperature shocks. The presence of retained austenite in the hardening process of tool-grade steel often causes the steel to have lower hardness than required and poor dimensional stability [\u003cspan additionalcitationids=\"CR16 CR17\" citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]. Therefore, controlling heat treatment parameters such as feed rate (i.e., the speed at which the roll moves through the induction coil, which is measured in mm/min) during induction hardening is essential [\u003cspan additionalcitationids=\"CR20\" citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]. One must consider the current frequency and its effect on the penetration depth (i.e., the heating depth) of the rolls, as it is well known that the use of high current frequencies leads to low penetration depths and vice versa. In this case study, only the influence of the feed rate during induction hardening of tool-steel work rolls was analyzed. We found that it had effects on the microstructure and wear properties of working roll, such as higher hardness depth and slightly better wear resistance. The impact of current frequency was not studied; that is, we kept the frequency constant throughout our tests.\u003c/p\u003e"},{"header":"Experimental work","content":"\u003cp\u003eThe simulation of induction hardening was performed with the Cenos software using a coupled electromagnetic-thermal model to describe the induction heating process. We used preselected dimensions and temperature, frequency, power, and material parameters that are commonly used to produce industrial work rolls and apply different feed rates. Cold work steel with 8% Cr was selected to produce the test rolls. Chemical composition is presented in Table \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e. The steel was made in an electric arc furnace, degassed in a vacuum, and remelted by electro-slag remelting process to obtain optimum properties. The ESR ingot was forged into a roll blank with dimensions of diameter 325 mm by length 1,700 mm by 2,740 mm and then soft annealed.\u003c/p\u003e\n\u003cdiv class=\"gridtable\"\u003e\n\u003cdiv class=\"colspec\" align=\"left\"\u003e\u0026nbsp;\u003c/div\u003e\n\u003cdiv class=\"colspec\" align=\"left\"\u003e\u0026nbsp;\u003c/div\u003e\n\u003cdiv class=\"colspec\" align=\"left\"\u003e\u0026nbsp;\u003c/div\u003e\n\u003ctable id=\"Tab1\" border=\"1\"\u003e\u003ccaption\u003e\n\u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\n\u003cdiv class=\"CaptionContent\"\u003e\n\u003cp\u003eComposition of 8% Cr cold-work tool steel roll blank\u003c/p\u003e\n\u003c/div\u003e\n\u003c/caption\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\"\u003e\n\u003cp\u003eC\u003c/p\u003e\n\u003c/th\u003e\u003cth align=\"left\"\u003e\n\u003cp\u003eSi\u003c/p\u003e\n\u003c/th\u003e\u003cth align=\"left\"\u003e\n\u003cp\u003eMn\u003c/p\u003e\n\u003c/th\u003e\u003cth align=\"left\"\u003e\n\u003cp\u003eP\u003c/p\u003e\n\u003c/th\u003e\u003cth align=\"left\"\u003e\n\u003cp\u003eS\u003c/p\u003e\n\u003c/th\u003e\u003cth align=\"left\"\u003e\n\u003cp\u003eCr\u003c/p\u003e\n\u003c/th\u003e\u003cth align=\"left\"\u003e\n\u003cp\u003eMo\u003c/p\u003e\n\u003c/th\u003e\u003cth align=\"left\"\u003e\n\u003cp\u003eV\u003c/p\u003e\n\u003c/th\u003e\u003cth align=\"left\"\u003e\n\u003cp\u003eW\u003c/p\u003e\n\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.93\u003c/p\u003e\n\u003c/td\u003e\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.96\u003c/p\u003e\n\u003c/td\u003e\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.34\u003c/p\u003e\n\u003c/td\u003e\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.015\u003c/p\u003e\n\u003c/td\u003e\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.006\u003c/p\u003e\n\u003c/td\u003e\u003ctd align=\"left\"\u003e\n\u003cp\u003e7.56\u003c/p\u003e\n\u003c/td\u003e\u003ctd align=\"left\"\u003e\n\u003cp\u003e1.45\u003c/p\u003e\n\u003c/td\u003e\u003ctd align=\"left\"\u003e\n\u003cp\u003e2.010\u003c/p\u003e\n\u003c/td\u003e\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.86\u003c/p\u003e\n\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/table\u003e\n\u003c/div\u003e\n\u003cp\u003eThe blank was machined and heat treated (i.e., quenched and tempered) to 900–1,000 N/mm\u003csup\u003e2\u003c/sup\u003e (i.e., the standard value for the production of rolls, which is equal to a hardness range of 27–32 HRc for the barrel and neck). After the first heat treatment, the blank was machined again to a diameter of 305 mm. Induction hardening was performed on the blank by heating it to an austenitizing temperature of 1,080°C and rapidly cooling it in water. As described in Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e and shown in Fig.\u0026nbsp;1, much higher power as usual is required to achieve the consistent austenitizing temperature and frequency. For example, disc 1 was hardened at a feed rate of 24 mm/min with a power of 210 kW, and when hardening disc 4 at a feed rate of 42 mm/min, a much higher power (370 kW) was required. In all our tests, the frequency was kept constant (varying from 355 to 358 Hz), yet the induction hardening machine automatically increased power during higher feeding rates to control the frequency constant.\u003c/p\u003e\n\u003cdiv class=\"gridtable\"\u003e\n\u003cdiv class=\"colspec\" align=\"left\"\u003e\u0026nbsp;\u003c/div\u003e\n\u003ctable id=\"Tab2\" border=\"1\"\u003e\u003ccaption\u003e\n\u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e\n\u003cdiv class=\"CaptionContent\"\u003e\n\u003cp\u003eSelected feed rate and actual induction hardening parameters\u003c/p\u003e\n\u003c/div\u003e\n\u003c/caption\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\"\u003e\n\u003cp\u003eSample name\u003c/p\u003e\n\u003c/th\u003e\u003cth align=\"left\"\u003e\n\u003cp\u003eFeed rate [mm/min]\u003c/p\u003e\n\u003c/th\u003e\u003cth align=\"left\"\u003e\n\u003cp\u003eTime at austenitization temperature [min]\u003c/p\u003e\n\u003c/th\u003e\u003cth align=\"left\"\u003e\n\u003cp\u003eAustenitization temperature [°C]\u003c/p\u003e\n\u003c/th\u003e\u003cth align=\"left\"\u003e\n\u003cp\u003eFrequency [Hz]\u003c/p\u003e\n\u003c/th\u003e\u003cth align=\"left\"\u003e\n\u003cp\u003ePower [%]\u003c/p\u003e\n\u003c/th\u003e\u003cth align=\"left\"\u003e\n\u003cp\u003ePower [kW]\u003c/p\u003e\n\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\"\u003e\n\u003cp\u003eDisc 1\u003c/p\u003e\n\u003c/td\u003e\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e24\u003c/p\u003e\n\u003c/td\u003e\u003ctd align=\"left\"\u003e\n\u003cp\u003e7.5\u003c/p\u003e\n\u003c/td\u003e\u003ctd rowspan=\"4\" align=\"char\" char=\".\"\u003e\n\u003cp\u003e1080\u003c/p\u003e\n\u003c/td\u003e\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e355\u003c/p\u003e\n\u003c/td\u003e\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e60\u003c/p\u003e\n\u003c/td\u003e\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e210\u003c/p\u003e\n\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\"\u003e\n\u003cp\u003eDisc 2\u003c/p\u003e\n\u003c/td\u003e\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e30\u003c/p\u003e\n\u003c/td\u003e\u003ctd align=\"left\"\u003e\n\u003cp\u003e6\u003c/p\u003e\n\u003c/td\u003e\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e357\u003c/p\u003e\n\u003c/td\u003e\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e75\u003c/p\u003e\n\u003c/td\u003e\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e300\u003c/p\u003e\n\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\"\u003e\n\u003cp\u003eDisc 3\u003c/p\u003e\n\u003c/td\u003e\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e36\u003c/p\u003e\n\u003c/td\u003e\u003ctd align=\"left\"\u003e\n\u003cp\u003e5\u003c/p\u003e\n\u003c/td\u003e\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e358\u003c/p\u003e\n\u003c/td\u003e\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e77\u003c/p\u003e\n\u003c/td\u003e\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e340\u003c/p\u003e\n\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\"\u003e\n\u003cp\u003eDisc 4\u003c/p\u003e\n\u003c/td\u003e\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e42\u003c/p\u003e\n\u003c/td\u003e\u003ctd align=\"left\"\u003e\n\u003cp\u003e4.3\u003c/p\u003e\n\u003c/td\u003e\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e357\u003c/p\u003e\n\u003c/td\u003e\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e86\u003c/p\u003e\n\u003c/td\u003e\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e370\u003c/p\u003e\n\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/table\u003e\n\u003c/div\u003e\n\u003cdiv class=\"gridtable\"\u003e\n\u003cdiv class=\"colspec\" align=\"left\"\u003e\u0026nbsp;\u003c/div\u003e\n\u003c/div\u003e\n\u003cp\u003eAfter induction hardening and tempering were applied to it, the roll was tempered at 515°C for 24 hours, followed by further tempering at 480°C for 24 hours. After heat treatment finalization, specimens were cut from a roll (as shown in Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e) using EDM (Electro Discharge Machining) to prevent any possible influence on the microstructure and other properties, ground, and polished for metallographic characterization.\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n"},{"header":"Methods","content":"\u003cp\u003eFirst, macro hardness on all four discs with different feed rates was measured using a Rockwell hardness tester. For each sample, ten measurements were performed per position. We used an Axio Imager A1m with an AxioCam ICc 3 digital camera and AxioVision software to classify carbides by size. For this purpose, we used ImageJ software, which can be used to calculate area and pixel value statistics for user-defined selections and intensity-thresholded objects. It can also be used to measure distances and angles.\u003c/p\u003e\u003cp\u003eThe microstructure was revealed by SEM while the composition of the carbides was determined by energy-dispersive X-ray spectroscopy (EDS). The crystal structures of the phases present in the roller discs were revealed (characterized) via EBSD. The samples were mounted in conductive Bakelite conductive resin and then carefully ground and polished. SEM was performed using a JEOL JSM − 7600F field emission scanning electron microscope with an Oxford Instruments INCA microanalysis suite, an X-Max 20 SDD-EDS detector, and CHANNEL5 EBSD software with a Nordlys detector. For EDS and EBSD analysis, we used a Zeiss CrossBeam 550 FIBSEM field emission scanning electron microscope (Germany) equipped with an EDAX Hikari Super EBSD camera and EDAX APEX software. The following parameters were adjusted to achieve the most accurate results: a 15-kV accelerating voltage and 2.0–5.0 nA probe current for SE images and EDS analyses and 70°-tilted samples and a 7.0-nA probe current for EBSD analyses on 18 mm WD.\u003c/p\u003e\u003cp\u003eXRD analysis was performed on a Bruker D8 Advance diffractometer with a scintillation NaI detector. The identification of individual peaks in the radiographs was performed with the program Match v.1.9h, Crystal Impact, Germany, and using PDF2 data 00-006-0696 for alpha Fe and 00-023-0298 for gamma Fe from the ICDD 2006 database. The content of retained austenite (RA-Retained Austenite, in vol.%) was calculated using Rietveld methods and use of PowderCell v.2.4. The basic principle of the Rietveld method is comparison of the measured diffractogram with the calculated one. The process is carried out until the best match is obtained (best fit).\u003c/p\u003e\u003cp\u003eTribological tests were performed using the pin-on-disc method, which was used due to the ability to control the conditions, reproducibility, quantitative data, and simulation of real-world mechanical interactions. Tests were performed at room temperature because we were using steel grades for cold rolling under the following conditions: a frequency of 1 Hz, a stroke length of 10.6 mm, applied loads of 1 GPa, 1.3 GPa, and 1.7 GPa, 1,800 cycles, and test duration of 30 minutes. The ball (counter body) was made of standard 100Cr6 steel with a diameter of 10 mm, and the discs had a surface roughness of 0.1 Ra.\u003c/p\u003e"},{"header":"Results and discussion","content":"\u003cp\u003eThe Cenos simulation of induction heating showed that there were significant differences in the hardening depth, but the influence on the microstructure and wear properties could not be simulated. Figure\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e shows that there were substantial changes in the temperature-depth along the diameter of the individual roll depending on the feeding rate. The feed rate seems to be a decisive factor in determining the hardening depth related to the temperature at any given position of the individual roll. When we increased the feeding rate from 24 to 42 mm/min, the temperature-depth decreased as the thermal energy transferred, which is heavily related to the electrical current frequency used in this experiment.\u003c/p\u003e\n\u003cp\u003eFigure \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e shows that in each disc from 1 to 4, the hardening depth ranges from 45 to 60 mm for the lowest feeding rate of 24 mm/min. On the contrary, the surface hardness varies only within the magnitude of a few HRc (i.e., from around 58 HRc for the feed rate of 36 mm/min to 62 HRc for the feed rate of 24 mm/min, which is the lowest). Additionally, the decrease in the hardening depth and hardness itself, as depicted by the curves in different colors, shows that in the case of the lowest feed rate, the decrease was less steep and more continuous than that in the case of the highest feed rate.\u003c/p\u003e\n\u003cp\u003eTable\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e shows the hardness depth measurements from a stationary Rockwell tester. Disc 1, which had a feed rate of 24 mm/min and an austenitizing temperature of 7.5 minutes, had a hardness depth of 50 mm according to the standard DIN 10328, or 25 mm according to the usual customer requirements in the roll industry. For disc 2, which had a 30 mm/min feed rate, the hardness depth was measured at 46 mm according to DIN 10328 and 22 mm according to standard customer requirements. Disc 3, which had a feed rate of 36 mm/min, had a hardening depth of 41 mm according to DIN 10328 and 16 mm according to standard customer requirements.\u003c/p\u003e\n\u003cdiv class=\"gridtable\"\u003e\n\u003cdiv class=\"colspec\" align=\"left\"\u003e\u0026nbsp;\u003c/div\u003e\n\u003ctable id=\"Tab3\" border=\"1\"\u003e\u003ccaption\u003e\n\u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e\n\u003cdiv class=\"CaptionContent\"\u003e\n\u003cp\u003eHardening depth measurements\u003c/p\u003e\n\u003c/div\u003e\n\u003c/caption\u003e\n\u003cthead\u003e\n\u003ctr\u003e\n\u003cth align=\"left\"\u003e\u0026nbsp;\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eFeed rate [mm/min]\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eTime at austenitization temperature [min]\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eHardening depth acc. to DIN 10328 [mm]\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eHardening depth acc. to customer requirements (min. 58 HRc) [mm]\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\u003eDisc 1\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e24\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e7.5\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e50\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e25\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eDisc 2\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e30\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e6\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e46\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e22\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eDisc 3\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e36\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e5\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e41\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e16\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eDisc 4\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e42\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e4.3\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e38\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e16\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003c/tbody\u003e\n\u003c/table\u003e\n\u003c/div\u003e\n\u003cdiv class=\"gridtable\"\u003e\n\u003cdiv class=\"colspec\" align=\"left\"\u003e\u0026nbsp;\u003c/div\u003e\n\u003cdiv class=\"colspec\" align=\"left\"\u003e\u0026nbsp;\u003c/div\u003e\n\u003c/div\u003e\n\u003cp\u003eThe same hardness depth according to standard customer requirements was also measured on disc 4 with a feed rate of 42 mm/min, but there is a difference in hardness depth according to DIN 10328, with disc 4 having a 3 mm lower hardness depth compared to disc 3 with feed rate 36 mm/min. With the results of the hardness measurements in mind, we turned to SEM to determine and evaluate the condition of the tested rolls on the microscale before and after induction hardening. SEM was performed on specimens from all four discs. During the microscopic examination, we discovered significant differences in the samples\u0026rsquo; microstructures, which were mainly composed of the martensitic matrix and primary and secondary carbides. Images of the microstructure are shown in Fig.\u0026nbsp;5. However, despite the significant differences in microstructure associated with carbide streaks, we did not find substantial variations in hardness between all four specimens. See Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e6\u003c/span\u003e.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eTable\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e shows the chemical compositions of various strains. As can be seen from the table, the matrix (i.e., Spectra 9 and 10) has almost the same chemical composition as that in Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e, while the carbides have two different chemical compositions: the first group contains 27.20\u0026ndash;34.62% Cr, 10.79\u0026ndash;23.77% V, 3.10\u0026ndash;5.76% Mo, and 1.17\u0026ndash;3.09% W, while the second group or grade contains 6.79\u0026ndash;7.96% Cr, 41.48\u0026ndash;55.18% V, 5.09\u0026ndash;6.31% Mo, and 4.19\u0026ndash;9.99% W.\u003c/p\u003e\n\u003cdiv class=\"gridtable\"\u003e\n\u003cdiv class=\"colspec\" align=\"left\"\u003e\u0026nbsp;\u003c/div\u003e\n\u003ctable id=\"Tab4\" border=\"1\"\u003e\u003ccaption\u003e\n\u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e\n\u003cdiv class=\"CaptionContent\"\u003e\n\u003cp\u003eChemical composition of spots on disc 1 with feed rate 24 mm/min\u003c/p\u003e\n\u003c/div\u003e\n\u003c/caption\u003e\n\u003cthead\u003e\n\u003ctr\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eSpectrum Label\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eSpectrum 1\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eSpectrum 2\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eSpectrum 3\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eSpectrum 4\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eSpectrum 5\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eSpectrum 6\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eSpectrum 7\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eSpectrum 8\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eSpectrum 9\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eSpectrum 10\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\u003eC\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e23.21\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e23.95\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e18.46\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e19.86\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e23.16\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e19.07\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e19.59\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e23.86\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eSi\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1.03\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1.02\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eTi\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.36\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.95\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.60\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1.27\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eV\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e55.18\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e53.99\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e23.77\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e59.05\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e41.48\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e11.95\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e10.79\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e50.31\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.76\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1.03\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eCr\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e7.53\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e6.97\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e27.20\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e7.39\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e7.96\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e34.66\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e34.62\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e6.98\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e6.79\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e7.13\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eMn\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.44\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.48\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eFe\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e2.20\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e4.26\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e21.72\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1.83\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e2.30\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e29.73\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e30.70\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e8.30\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e88.92\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e88.23\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eMo\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e6.31\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e5.32\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e5.76\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e6.05\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e15.11\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e3.41\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e3.10\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e5.09\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1.05\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1.40\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eW\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e5.20\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e4.55\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e3.09\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e5.21\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e9.99\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1.17\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1.20\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e4.19\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1.01\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.70\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eTotal\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e100.00\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e100.00\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e100.00\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e100.00\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e100.00\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e100.00\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e100.00\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e100.00\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e100.00\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e100.00\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003c/tbody\u003e\n\u003c/table\u003e\n\u003c/div\u003e\n\u003cdiv class=\"gridtable\"\u003e\u0026nbsp;\u003c/div\u003e\n\u003cdiv class=\"gridtable\"\u003e\u0026nbsp;\u003c/div\u003e\n\u003cp\u003eThe compositions of different streaks of carbides revealed that there were at least two groups of complex carbides present in the samples. One group was based on chromium, and the other was based on vanadium. Both groups contain at least three to four other chemical elements, adding to the hardness of the examined rolls. The carbon content has not been accounted for in the EDS analysis presented in Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e. Nevertheless, based on our previous knowledge of the formation of carbides in complex steels, we can classify the first group of carbides as the (Cr, V, Mo, W)\u003csub\u003ex\u003c/sub\u003eC\u003csub\u003ey\u003c/sub\u003e type and the second group as the (V, Cr, Mo, W)\u003csub\u003ex\u003c/sub\u003eC\u003csub\u003ey\u003c/sub\u003e complex type of carbides, actually expecting MC and M\u003csub\u003e7\u003c/sub\u003eC\u003csub\u003e3\u003c/sub\u003e type of carbides as it will be shown later. The first group of carbides is based on chromium while the other is based on vanadium. Both elements, along with some others, are known to be very potent elements for the formation of carbides. Of course, the carbides are not the only microstructural constituents that influence the properties of the steel. The constitution of the matrix of the investigated steel can have significant impacts on the properties of the steel. Therefore, we turned our attention to the EDS analyses and the distribution of the elements in the carbides and the matrixes of the investigated steel. Figure\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e7\u003c/span\u003e shows the overall EDS plot on the sample from disc 1 at a feed rate of 24 mm/min, confirming the presence of two main types of carbides. The distribution of the individual alloying elements is shown in Fig.\u0026nbsp;8. Using light microscopy, we analyzed 200 individual spots on samples from discs 1\u0026ndash;4 and measured the average size of the carbides (see Fig.\u0026nbsp;9).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eOur analysis results for carbide sizes, which are shown in Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e10\u003c/span\u003e and Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e5\u003c/span\u003e, revealed that the largest average carbide size was present in the samples from disc 1, which had a feed rate of 24 mm/min, and the smallest average carbide size was present in the samples from disc 4, which had a feed rate of 42 mm/min.\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003cdiv class=\"gridtable\"\u003e\n\u003ctable id=\"Tab5\" border=\"1\"\u003e\u003ccaption\u003e\n\u003cdiv class=\"CaptionNumber\"\u003eTable 5\u003c/div\u003e\n\u003cdiv class=\"CaptionContent\"\u003e\n\u003cp\u003eAverage size of carbides \u0026ndash; image size 548.91x410.33 \u0026micro;m\u003c/p\u003e\n\u003c/div\u003e\n\u003c/caption\u003e\n\u003cthead\u003e\n\u003ctr\u003e\n\u003cth align=\"left\"\u003e\u0026nbsp;\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eDisc 1 with feed rate 24 mm/min\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eDisc 2 with feed rate 30 mm/min\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eDisc 3 with feed rate 36 mm/min\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eDisc 4 with feed rate 42 mm/min\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\u003eAverage size of carbide [\u0026micro;m\u003csup\u003e2\u003c/sup\u003e]\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e2.265\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e2.163\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e2.018\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1.843\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003c/tbody\u003e\n\u003c/table\u003e\n\u003c/div\u003e\n\u003cp\u003eWhen we analyzed the size of carbides in the range of 0\u0026ndash;1 \u0026micro;m\u003csup\u003e2\u003c/sup\u003e, we found that the samples of disc 1 with a feed rate of 24 mm/min had the smallest average carbide size.\u003c/p\u003e\n\u003cp\u003eThe analyses of the sizes of carbides in the 1\u0026ndash;5-\u0026micro;m\u003csup\u003e2\u003c/sup\u003e range showed that the carbides in the samples from disc 1 with a feed rate of 24 mm/min had the largest size, confirming the presence of the Ostwald ripening process. This led to the supersaturation of the matrix, which together with the feed rate, affects the shape of carbides. The specimens from disc 1 were hardened at a lower feed rate compared to other three discs, giving the carbides additional time to develop and become spherical (the carbides become more rounded), and the smaller ones dissolved. When measuring the macro hardness, we found that the microhardness was the highest in the sample from disc 1 with a feed rate of 24 mm/min and the lowest in the sample of disc 4 with a feed rate of 42 mm/min, which was hardened at the highest feed rate. Because we identified two types of carbide, we wanted to determine which types of carbide they were. For this purpose, we used the well-established EBSD technique, and the results are presented in Figs.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e11\u003c/span\u003e and \u003cspan class=\"InternalRef\"\u003e12\u003c/span\u003e, with the EBSD IPF Z map and the phase for the confirmation of the proposed phases shown. The analysis results confirmed the presence of two main types of carbides in the sample, namely MC and M\u003csub\u003e7\u003c/sub\u003eC\u003csub\u003e3\u003c/sub\u003e. The IPF Z map shows the typical microstructure of martensitic steel with needle-like structures and carbides in the matrix. In contrast, the phase map shows the martensitic bcc phase in yellow, M\u003csub\u003e7\u003c/sub\u003eC\u003csub\u003e3\u003c/sub\u003e in green and MC in red.\u003c/p\u003e\n\u003cp\u003eFigure \u003cspan class=\"InternalRef\"\u003e12\u003c/span\u003e contains an EDS map of the same spot as EBSD, where different amounts of elements (e.g., Cr, Fe, V, W, Mo, and C) in the carbides and the matrix so it can corroborate the different carbides have an additional amount of alloying element.\u003c/p\u003e\n\u003cp\u003eX-ray diffraction was performed on samples after induction heating and hardening and first and second tempering to confirm the theory that they had lower residual austenite content than in the production of rolls from standard grades. Figure\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e13\u003c/span\u003e shows the X-ray diffraction pattern of the sample from disc 1 with a feed rate of 24 mm/min after second tempering at 480\u0026deg;C for 24 hours. The sample contained 99.6% martensite and 0.4% austenite. The XRD results are presented in Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e6\u003c/span\u003e. The content of retained austenite (RA-Retained Austenite, in vol.%) was calculated using Rietveld methods and use of PowderCell v.2.4 software.\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003cdiv class=\"gridtable\"\u003e\n\u003ctable id=\"Tab6\" border=\"1\"\u003e\u003ccaption\u003e\n\u003cdiv class=\"CaptionNumber\"\u003eTable 6\u003c/div\u003e\n\u003cdiv class=\"CaptionContent\"\u003e\n\u003cp\u003eMeasurements of RA on a sample from disc 1 with a feed rate of 24 mm/min\u003c/p\u003e\n\u003c/div\u003e\n\u003c/caption\u003e\n\u003cthead\u003e\n\u003ctr\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eProcess\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eMeasured content of RA [%]\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\u003eInduction heating and hardening\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e12.70\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eTempering 1\u0026ndash;515\u0026deg;C/24 h\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1.00\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eTempering 2\u0026ndash;480\u0026deg;C/24 h\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e0.40\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003c/tbody\u003e\n\u003c/table\u003e\n\u003c/div\u003e\n\u003cdiv class=\"gridtable\"\u003e\n\u003cdiv class=\"colspec\" align=\"left\"\u003e\u0026nbsp;\u003c/div\u003e\n\u003c/div\u003e\n\u003cp\u003eTribological tests that involved using the pin-on-the-disc method gave us clear information about wear volume and specific wear rate of all discs with different feed rates. We applied other loads with 1,800 cycles per specimen. The wear volume and specific wear rate were lowest for disc 1 with a 24 mm/min feed rate. However, the differences in wear were minimal and are more correlated to material homogeneity and its local characteristics, as presented in Figs.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e14\u003c/span\u003e and \u003cspan class=\"InternalRef\"\u003e15\u003c/span\u003e.\u003c/p\u003e\n\u003cp\u003eThe wear volume and specific wear rate of a ball made of 100Cr6 steel were highest on the disc with a 24 mm/min feed rate. The specific wear rate was found to be highest at a feed rate of 24 mm/min for all three loads. Furthermore, the specific wear rate decreases as the feed rate increases. As we increased the load for the feed rate of 24 mm/min, the counter body penetrated deeper into the surface of the sample, leaving a narrower track with a lower specific wear rate. On the contrary, the specific wear rate decreased when an increasing feed rate was used and appeared to be similar at the 36 and 42 mm/min feed speeds. We hypothesize that this is due to the lower amount of annealing of the matrix that occurred at the lower feed rates, which generated the heat required to anneal the iron-based matrix. Again, the observed differences from other discs were minor and do not represent significant improvements regarding wear resistance. Images of wear are presented in Fig.\u0026nbsp;16.\u003c/p\u003e"},{"header":"Conclusions","content":"\u003cp\u003eInduction hardening was performed by heating a tool-steel roll to an austenitizing temperature of 1,080\u0026deg;C, followed by rapid cooling in water. When high feed rates are used, higher power is needed to achieve technologically prescribed austenitizing temperature and frequency. For example, disc 1 was hardened at a feed rate of 24 mm/min with a power of 210 kW, and when hardening disc 4 at a feed rate of 42 mm/min, a much higher power was needed, 370 kW.\u003c/p\u003e \u003cp\u003eDisc 1, with a feed rate of 24 mm/min and 7.5 minutes at austenitizing temperature, had a hardening depth of 50 mm according to the standard DIN 10328 (i.e., a minimum of 80% of surface hardness) or 25 mm according to legal customer requirements in the roll industry (i.e., a hardness drop for max. 2 HRc). For disc 2, with a feed rate of 30 mm/min, a hardness depth of 46 mm was measured according to DIN 10328 and 22 mm according to standard customer requirements. Disc 3, with a feed rate of 36 mm/min, was found to have a hardening depth of 41 mm according to DIN 10328 and 16 mm according to standard customer requirements. The same hardening depth according to standard customer requirements was also measured for disc 4 with a 42 mm/min feed rate. Still, there is a difference in the hardening depth according to DIN 10328, with disc 4 having a 3 mm lower hardening depth than disc 3. This shows us that the feed rate significantly influences the hardening depth because the hardening depth is much deeper at low feed rates than when hardening tool-steel work rolls at high feed rates.\u003c/p\u003e \u003cp\u003eOur SEM and EDS analysis results revealed two main chemical compositions of the MC carbides. Using the EBSD technique, we confirmed the presence of two types of carbides in our 8% Cr steel: MC and M\u003csub\u003e7\u003c/sub\u003eC\u003csub\u003e3\u003c/sub\u003e.\u003c/p\u003e \u003cp\u003eWe identified the largest average carbide size in the samples for disc 1 with a feed rate of 24 mm/min and the smallest average carbide size in the samples for disc 4 with a feed rate of 42 mm/min. The average carbide size was highest on disc 1 with a feed rate of 24 mm/min and a size of 2,265 \u0026micro;m\u003csup\u003e2\u003c/sup\u003e and lowest on disc 4 with a feed rate of 42 mm/min with an average size of 1,843 \u0026micro;m\u003csup\u003e2\u003c/sup\u003e. This confirms the Ostwald ripening process, which leads to a supersaturation of the Fe-based matrix, which together with the feed rate, influences the shape of the carbides. The samples from disc 1 were hardened at a lower feed rate, giving the carbides time to spheroidize and grow (the carbides increased in sphericity), while the small carbides dissolved. The sample with the highest macro hardness was from disc 1 with a feed rate of 24 mm/min and the lowest for the sample from disc 4 with a feed rate of 42 mm/min, which was hardened at the highest feed rate.\u003c/p\u003e \u003cp\u003eXRD presented us with detailed information about the crystallographic structure of discs, hardened with different feed rates. After induction heating and hardening, there was 12.7% retained austenite (RA) and 87.3% martensite. After the first tempering at 515\u0026deg;C for 24 hours, the RA content decreased to 1.2%, and after the second tempering at 480\u0026deg;C for 24 hours, the RA content further decreased to 0.4%. This confirms the theory that rolls produced from tool-grade steels contain much lower RA content and are much safer to use than standard-grade rolls.\u003c/p\u003e \u003cp\u003eTribological studies on all four discs, hardened with different feed rates, have shown that disc 1, with a 24 mm/min feed rate, has slightly better wear resistance. Still, initial differences in material homogeneity or local features in the material have a more significant influence on the material\u0026rsquo;s wear resistance than the change in feed rate during induction hardening.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eEthics approval and consent to participate\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of data and materials\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors confirm that the data supporting the findings of this study are available within the article its supplementary materials.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNo funds, grants, or other support was received.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthors\u0026apos; contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eSapek organized the research work and performed the measurements on industrial level. B. Markoli helped us with LOM, interpretation of the results and work on the manuscript. M. Kalin was working on the tribological studies. Č. Donik and M. Godec were responsible for work on SEM and EBSD, and interpretation of results.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthors\u0026apos; information (optional)\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eSychterz, J. Improved roll performance and elimination of chrome plating using forged semi high-speed steel roll materials in cold rolling application. Rolls 5 Conference, 22\u0026ndash;24 April 2015, Birmingham (UK).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMcCann, J. 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Sadhana-academy Proceedings in Engineering Sciences - SADHANA-ACAD PROC ENG SCI. 36. 141\u0026ndash;152. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1007/s12046-011-0020-x\u003c/span\u003e\u003cspan address=\"10.1007/s12046-011-0020-x\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":true,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"","lastPublishedDoi":"10.21203/rs.3.rs-4597879/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4597879/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eRolls are the most critical yet vulnerable parts of cold rolling mills. It is crucial for them to withstand long rolling campaigns without losing surface roughness or incurring damage. The newly developed rolls are made from tool-grade steel with high roughness, lower wear, and high damage resistance. One of the most important advantages is the elimination of the need for chrome plating, which is currently widely used on standard steel rolls but is ecologically harmful. We investigated type of steel with 8% Cr for use in cold rolling using LOM, XRD, SEM, electron backscatter diffraction (EBSD), hardness measurements, and tribological tests. In this study, a roll with a diameter of 325 mm was ESR remelted and forged, machined to a diameter of 305 mm, and quenched and tempered to simulate industrial roll production. A forged roll was induction heated and hardened at four different feed rates (i.e., 24 mm/min, 30 mm/min, 36 mm/min, and 42 mm/min), tempered at 515\u0026deg;C for 24 hours and again at 480\u0026deg;C for 24 hours, and dissected for in-depth analysis. We identified a clear relationship between the feed rate of the roll during induction hardening and the depth of hardness, the sizes of carbides, and the wear properties of the roll. By reducing the feed rate of the roll through the inductor, we increased the depth of the hardened layer from 16 mm (at a feed rate of 36 mm/min) to 25 mm (at a feed rate of 24 mm/min), which is a 56.25% increase expected to extend the lifespan of the working roll without having negative effects on the wear resistance and other important parameters. XRD analysis showed that the sample had a 0.4% residual austenite, which means it had a significantly lower risk of roll damage during operation than standard steel grades.\u003c/p\u003e","manuscriptTitle":"Effect of feed rate during induction hardening on the hardening depth, microstructure, and wear properties of tool-grade steel work roll","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-07-24 08:34:04","doi":"10.21203/rs.3.rs-4597879/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"8a05f89f-fe59-445d-8908-41736bbc17b6","owner":[],"postedDate":"July 24th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2024-12-02T17:21:15+00:00","versionOfRecord":{"articleIdentity":"rs-4597879","link":"https://doi.org/10.1186/s40712-024-00193-5","journal":{"identity":"journal-of-materials-science-materials-in-engineering","isVorOnly":true,"title":"Journal of Materials Science: Materials in Engineering"},"publishedOn":"2024-11-27 15:57:25","publishedOnDateReadable":"November 27th, 2024"},"versionCreatedAt":"2024-07-24 08:34:04","video":"","vorDoi":"10.1186/s40712-024-00193-5","vorDoiUrl":"https://doi.org/10.1186/s40712-024-00193-5","workflowStages":[]},"version":"v1","identity":"rs-4597879","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4597879","identity":"rs-4597879","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}