High-strength steels are used more than general structural steel due to their combination of properties such as high strength, good toughness and weldability. They are mainly used in the manufacture of heavy vehicles for the mining industry, cranes, transportation, etc. However, welding these grades of steel brings new challenges. Also, a simulation for welding high-strength steel is required more often. To insert a material database into the simulation program, it is necessary to conduct investigations using CCT (Continuous Cooling Transformation) diagrams, welded joints research, and more. To investigate the behavior of S960MC steel during heating and cooling, we used dilatometry analysis supported by EBSD (Electron Backscatter Diffraction) analysis. A CCT diagram was constructed. The transformation temperatures of Ac1 and Ac3 increase with increasing heating rate. The Ac1 temperature increased by 54 °C and the Ac3 temperatures by 24 °C as the heating rate increased from 0.1 °C/s to 250 °C/s. The austenite decomposition temperatures have a decreasing trend in the cooling phase with increasing cooling rate. As the cooling rate changes from 0.03 °C/s to 100 °C/s, the initial transformation temperature drops from 813 °C to 465 °C. An increase in the cooling rate means a higher proportion of bainite and martensite. At the same time, the hardness increases from 119 HV10 to 362 HV10.

Faculty of Mechanical Engineering Technical University of Liberec Studenstká 2 461 17 Liberec Czech Republic

Faculty of Mechanical Engineering University of Žilina Univerzitná 8215 1 010 26 Žilina Slovakia

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Garcia C.I. High strength low alloyed (HSLA) steels. In: Rana R., Singh S.B., editors. Automotive steels: Design, Metallurgy, Processing and Applications. 1st ed. Woodhead Publishing; Cambridge, UK: 2016. pp. 145–167.

Kaščák L., Cmorej D., Spišák E., Slota J. Joining the High-Strength Steel Sheets Used in Car Body Production. Adv. Sci. Technol. Res. J. 2021;15:184–196. doi: 10.12913/22998624/131739. DOI

Guo W., Li L., Dong S., Crowther D., Thompson A. Comparison of microstructure and mechanical properties of ultra-narrow gap laser and gas-metal-arc welded S960 high strength steel. Opt. Lasers Eng. 2016;91:1–15. doi: 10.1016/j.optlaseng.2016.11.011. DOI

Ghafouri M., Ahn J., Mourujärvi J., Björk T., Larkiola J. Finite element simulation of welding distortions in ultra-high strength steel S960 MC including comprehensive thermal and solid-state phase transformation models. Eng. Struct. 2020;219:110804. doi: 10.1016/j.engstruct.2020.110804. DOI

Tomków J., Landowski M., Fydrych D., Rogalski G. Underwater wet welding of S1300 ultra-high strength steel. Mar. Struct. 2022;81:103120. doi: 10.1016/j.marstruc.2021.103120. DOI

Górka J., Janicki D., Fidali M., Jamrozik W. Thermographic Assessment of the HAZ Properties and Structure of Thermomechanically Treated Steel. Int. J. Thermophys. 2017;38:183. doi: 10.1007/s10765-017-2320-9. DOI

Hrivňák I. Zváranie a Zvariteľnosť Materiálov. Citadella; Bratislava, Slovakia: 2013. Welding and Weldability of Materials. (In Slovak)

Zhao J., Jiang Z., Kim J.S., Lee C.S. Effects of tungsten on continous cooling transformation charakteristics of microalloyed steel. Mater. Des. 2013;49:252–258. doi: 10.1016/j.matdes.2013.01.056. DOI

Villalobos J.C., Del-Pozo A., Campillo B., Mayen J., Serna S. Microalloyed Steels trough History until 2018: Review of Chemical Composition, Processing and Hydrogen Service. Metals. 2018;8:351. doi: 10.3390/met8050351. DOI

Gu Y., Tian P., Wang X., Han X.-L., Liao B., Xiao F.-R. Non-isothermal prior austenite grain growth of a high-Nb X100 pipeline steel during a simulated welding heat cycle process. Mater. Des. 2016;89:589–596. doi: 10.1016/j.matdes.2015.09.039. DOI

Karmakar A., Biswas S., Mukherjee S., Chakrabarti D., Kumar V. Effect of composition and thermo-mechanical processing schedule on the microstructure, precipitation and strengthening of Nb-microalloyed steel. Mater. Sci. Eng. A. 2017;690:158–169. doi: 10.1016/j.msea.2017.02.101. DOI

Nishioka K., Ichikawa K. Progres in thermomechanical control of steel plates and their commercialization. Sci. Technol. Adv. Mater. 2012;13:023001. doi: 10.1088/1468-6996/13/2/023001. PubMed DOI PMC

Lagneborg R., Hutchinson B., Siwecki T., Zajac S. The role of vanandium in microalloyed steels. Scand. J. Metall. 1999;28:186–241.

Porter D., Laukkanen A., Nevasmaa P., Rahka K., Wallin K. Performance of TMCP steel with respect to mechanical properties after cold forming and post-forming heat treatment. Int. J. Press. Vessels Pip. 2004;81:867–877. doi: 10.1016/j.ijpvp.2004.07.006. DOI

Hochhauser F., Ernst W., Rauch R., Vallant R., Enzinger N. Influence of the Soft Zone on The Strength of Welded Modern Hsla Steels. Weld. World. 2013;56:77–85. doi: 10.1007/BF03321352. DOI

Gáspár M. Effect of Wleding Heat Input on Simulated HAZ Areas in S960QL High Strength Steel. Metals. 2019;9:1226. doi: 10.3390/met9111226. DOI

Pisarski H.G., Dolby R.E. The Significance of Softened HAZs in High Strength Structural Steels. Weld. World. 2003;47:32–40. doi: 10.1007/BF03266387. DOI

Bayock F.N., Kah P., Mvola B., Layus P. Effect of Heat Input and Undermatched Filler Wire on the Microstructure and Mechanical Properties of Dissimilar S700MC/S960QC High-Strength Steels. Metals. 2019;9:883. doi: 10.3390/met9080883. DOI

Lahtinen T., Vilaça P., Peura P., Mehtonen S. MAG Welding Tests of Modern High Strength Steels with Minimum Yield Strength of 700 MPa. Appl. Sci. 2019;9:1031. doi: 10.3390/app9051031. DOI

Schneider C., Ernst W., Schnitzer R., Staufer H., Vallant R., Enzinger N. Welding of S960MC with undermatching filler material. Weld. World. 2018;62:801–809. doi: 10.1007/s40194-018-0570-1. DOI

Mičian M., Harmania D., Nový F., Winczek J., Moravec J., Trško L. Effect of the t8/5 cooling time on the properties of S960MC steel in the HAZ of welded joint evaluated by thermal physical simulation. Metals. 2020;10:229. doi: 10.3390/met10020229. DOI

Stemne D., Naström T., Thorstensson O., Bäckström C. Welding Handbook, a Guide to Better Welding of HARDOX and STRENX. Höglund Design AB; Oxelosund, Sweden: 2019.

Vimalraj C., Kah P., Layus P., Belinga E.M., Parshin S. High-strength steel S960QC welded with rare earth nanoparticle coated filler wire. Int. J. Adv. Manuf. Technol. 2018;102:105–119. doi: 10.1007/s00170-018-3059-6. DOI

Guo W., Crowther D., Francis J.A., Thompson A., Liu Z., Li L. Microstructure and mechanical properties of laser welded S960 high strength steel. Mater. Des. 2015;85:534–548. doi: 10.1016/j.matdes.2015.07.037. DOI

Sága M., Blatnická M., Blatnický M., Dižo J., Gerlici J. Research of the Fatigue Life of Welded Joints of High Strength Steel S960 QL Created Using Laser and Electron Beams. Materials. 2020;13:2539. doi: 10.3390/ma13112539. PubMed DOI PMC

Amraei M., Ahola A., Afkhami S., Björk T., Heidarpour A., Zhao X.-L. Effects of heat input on the mechanical properties of butt-welded high and ultra-high strength steels. Eng. Struct. 2019;198:109460. doi: 10.1016/j.engstruct.2019.109460. DOI

Jambor M., Novy F., Mician M., Trsko L., Bokuvka O., Pastorek F., Harmaniak D. Gas Metal Arc Welding of Thermo-Mechanically Controlled Processed S960MC Steel Thin Sheets with Different Welding Parameters. Commun. Sci. Lett. Univ. Zilina. 2018;20:29–35. doi: 10.26552/com.C.2018.4.29-35. DOI

Fonda R.W., Vandermeer R.A., Spanos G. Continuous Cooling Transformation (CCT) Diagrams for Advanced Navy Welding Consumables. Naval Reasearch Laboratory; Washington, DC, USA: 1998.

Li X., Shi L., Liu Y., Gan K., Liu C. Achieving a desirable combination of mechanical properties in HSLA steel through step quenching. Mater. Sci. Eng. A. 2020;772:138683. doi: 10.1016/j.msea.2019.138683. DOI

Jiang Z., Zhao J. Rolling of Advanced High Strength Steels. CRC Press; Boca Raton, FL, USA: 2017.

Wu X., Lin H., Luo W., Jiang H. Microstructure and microhardness evolution of thermal simulated HAZ of Q&P980 steel. J. Mater. Res. Technol. 2021;15:6067–6078. doi: 10.1016/j.jmrt.2021.11.059. DOI

Mandal G., Dey I., Mukherjee S., Ghosh S. Phase transformation and mechanical properties of ultrahigh strength steels under continuous cooling conditions. J. Mater. Res. Technol. 2022;19:628–642. doi: 10.1016/j.jmrt.2022.05.033. DOI

Geng X., Wang H., Xue W., Xiang S., Huang H., Meng L., Ma G. Modeling of CCT diagrams for tool steels using different machine learning techniques. Comput. Mater. Sci. 2020;171:109235. doi: 10.1016/j.commatsci.2019.109235. DOI

SSAB. [(accessed on 8 November 2021)]. Available online: https://www.ssab.com/en/products/brands/strenx/products/strenx-960-mc.

Mola J. Dilatometry Analysis of Cementite Precipitation in Medium Mn High Carbon Steels; Proceedings of the ICAS & HMnS; Chengdu, China. 16–18 November 2016.

Bräutigam-Matus K., Altamirano G., Salinas A., Flores A., Goodwin F. Experimental Determination of Continuous Cooling Transformation (CCT) Diagrams for Dual-Phase Steels from the Intercritical Temperature Range. Metals. 2018;8:674. doi: 10.3390/met8090674. DOI

Hot Rolled Flat Products Made of High Yield Strength Steels for Cold Forming—Part 2: Technical Delivery Conditions for Thermomechanically Rolled Steels. Slovak Office of Standards, Metrology and Testing; Bratislava, Slovakia: 2014.

Metallic Materials. Tensile Testing. Part 1: Method of Test at Room Temperature. Slovak Office of Standards, Metrology and Testing; Bratislava, Slovakia: 2022.

TA Instruments. [(accessed on 20 November 2021)]. Available online: https://www.tainstruments.com/dil-805l-quenching-dilatomers/

Pawlowski B., Bala P., Dziurka R. Improrer interpretation of dilatometric data for cooling transformation in steels. Arch. Metall. Mater. 2014;59:1159–1161. doi: 10.2478/amm-2014-0202. DOI

Grajcar A., Zalecki W., Skrzypczyk P., Kilarski A., Kowalski A., Kolodziej S. Dilatometric study of phase transformations in advanced high-stength bainitic steel. J. Anal. Calorim. 2014;118:739–748. doi: 10.1007/s10973-014-4054-2. DOI

Moravec J., Dikovits M., Novakova I., Caliskanoglu O. Comparison of Dilatometry Results Obtained by Two Different Devices when Generating CCT and In Situ Diagrams. Key Eng. Mater. 2016;669:477–484. doi: 10.4028/www.scientific.net/KEM.669.477. DOI

Falkenreck T., Kromm A., Böllinghaus T. Investigation of physically simulated weld HAZ and CCT diagram of HSLA armour steel. Weld. World. 2017;62:47–54. doi: 10.1007/s40194-017-0511-4. DOI

Kawulok R., Schindler I., Kawulok P., Rusz S., Opěla P., Solowski Z., Čmiel M. Effect of Deformation on the Continuous Cooling Transformation (CCT) Diagram of Steel CrB4. Metalurgija. 2015;54:473–476.

Contreras A., López A., Gutiérrez E., Fernández B., Salinas A., Deaquino R., Bedolla A., Saldaña R., Reyes I., Aguilar J., et al. An approach for the design of multiphase advanced high-strength steels based on the behavior of CCT diagrams simulated from the intercritical temperature range. Mater. Sci. Eng. A. 2019;772:138708. doi: 10.1016/j.msea.2019.138708. DOI

Skočovský P., Bokůvka O., Konečná R., Tillová E. Náuka o Materiáli. EDIS; Žilina, Slovakia: 2014.

Schindler I., Kawulok R., Opěla P., Kawulok P., Rusz S., Sojka J., Sauer M., Navrátil H., Pindor L. Effects of Austenitization Temperature and Pre-Deformation on CCT Diagrams of 23MnNiCrMo5-3 Steel. Materials. 2020;13:5116. doi: 10.3390/ma13225116. PubMed DOI PMC

Kamyabi-Gol A., Herath D., Mendez P.F. A comparison of common and new methods to determine martensite start temperature using a dilatometer. Can. Met. Q. 2017;56:85–93. doi: 10.1080/00084433.2016.1267903. DOI