Influence of Cooling Rates on Microstructure and Mechanical Performance of High-Strength Steel SMAW Joints for High-Pressure Applications

Asaad Kadhim  Eqal; Ahmed Hashim  Kreem; Ali Taha  Mohammed

doi:10.3989/revmetalm.e296.1768

Authors

Asaad Kadhim Eqal Department of Mechanical Techniques, Amarah Technical Institute, Southern Technical University https://orcid.org/0000-0002-5692-5702
Ahmed Hashim Kreem Department of Mechanical Techniques, Amarah Technical Institute, Southern Technical University https://orcid.org/0000-0003-1417-6405
Ali Taha Mohammed Department of Mechanical Techniques, Amarah Technical Institute, Southern Technical University https://orcid.org/0000-0003-2552-1155

DOI:

https://doi.org/10.3989/revmetalm.e296.1768

Keywords:

Cooling rates, DP780 dual-phase steel, High-pressure applications, Phase transformation, Tensile properties

Abstract

This manuscript intends to carry out a comprehensive study on the microstructural evolution, mechanical properties and performance of DP780 dual-phase steel joints under the influence of the post-weld cooling rates during Shielded Metal Arc Welding (SMAW). DP780 has already been used for thin-gauge automotive components; in this study we evaluate the suitability of the 6 mm thick plates in high-pressure industrial applications requiring weight reduction. The cooling mode was set to three different modes including water quench (rapid), still air (moderate), and thermal insulation blankets (gradual). Specific microstructural characterization of the Fusion Zone (FZ) and Heat Affected Zone (HAZ) indicated that rapid cooling leads to a large volume fraction of lath martensite with a maximum microhardness of 350 HV and ultimate tensile strength (UTS) of 728 MPa. In comparison, moderate cooling enables a balanced phase distribution of bainite and polygonal ferrite, resulting in considerable tensile strength versus ductility trade-off, attaining a yield strength of 624 MPa. The observed gradual cooling leads to the development of a coarser ferritic-pearlitic structure, which reduces the hardness and load-bearing capacity considerably. Tensile testing also revealed high dependence upon the phase transformations due to cooling at the FZ/HAZ interface. This reinforces the importance of accurate thermal control for high-strength steel joint safety due to peak loading conditions.

Downloads

Download data is not yet available.

References

Alkhafaji, M.M., Mohammed, M.S., Amin, S.A., Habeeb, L.J., Majdi, H.S. (2025). Electrodes type effects on welding of copper to 304 stainless steel and analysis of heat distribution, microstructures, and mechanical properties. Int. J. Comput. Methods Exp. Meas. 13 (1), 85-96.

Amin, S.A., Abdulhasan, A.A., Mohammed, M.S., Majdi, H.S. (2024). Experimental and numerical study of maximum welding joint temperature impacts in alloy steel pipe welding microstructure, distortion, corrosion resistance, and mechanical properties. JCAM 3 (6), 775-786.

ASTM E8 M-04 (2010). Standard Test Methods for Tension Testing of Metallic Materials. ASTM International, West Conshohocken, USA.

Chabok, A., Van der Aa, E., De Hosson, J.T.M., Pei, Y.T. (2017). Mechanical behavior and failure mechanism of resistance spot welded DP1000 dual phase steel. Mater. Des. 124, 171-182.‏

DeCost, B.L., Lei, B., Francis, T., Holm, E.A. (2019). High throughput quantitative metallography for complex microstructures using deep learning: A case study in ultrahigh carbon steel. Microsc. Microanal. 25 (1), 21-29.

Derakhshan, E.D., Yazdian, N., Craft, B., Smith, S., Kovacevic, R. (2018). Numerical simulation and experimental validation of residual stress and welding distortion induced by laser-based welding processes ofthin structural steel plates in butt joint configuration. Opt. Laser Technol. 104, 170-182.

Dewan, M.W. (2015). Challenges towards structural integrity and performance improvement of welded structures. LSU Doctoral Dissertations, Louisiana State University and Agricultural & Mechanical College.‏

Du, C., Hoefnagels, J.P.M., Vaes, R., Geers, M.G.D. (2016). Block and sub-block boundary strengthening in lath martensite. Scr. Mater. 116, 117-121.

Haslberger, P., Holly, S., Ernst, W., Schnitzer, R. (2018). Microstructure and mechanical properties of high-strength steel welding consumables with a minimum yield strength of 1100 MPa. J. Mater. Sci. 53 (11), 6968–6979.

Hidalgo, J., Santofimia, M.J. (2016). Effect of prior austenite grain size refinement by thermal cycling on the microstructural features of As-quenched lath martensite. Metall. Mater. Trans. A 47, 5288–5301.

Kumar, V., Chhibber, R., Mahajan, S. (2023). Investigations on wetting and structural behavior using CaF2-SiO2-CaO-22.5%TiO2 SMAW electrode coating for AUSC applications. Proceedings of the Institution of Mechanical Engineers, Part L: Journal of Materials: Design and Applications 237 (8), 1861-1873.

Kumar, V., Chhibber, R. (2024). Weld chemistry and microhardness studies of formulated SrO-CaF2-CaO-SiO2 silicabased SMAW electrode with nickel wire. Silicon 16 (9), 3689-3707.‏

Lan, L., Kong, X., Qiu, C., Zhao, D. (2016). Influence of microstructural aspects on impact toughness of multi-pass submerged arc welded HSLA steel joints. Mater. Des. 90, 488–498.

Loder, D., Michelic, S., Bernhard, C. (2017). Acicular ferrite formation and its influencing factors - A review. J. Mater. Sci. Res. 6 (1), 24–43.

Makhlin, N.M. (2020). Processes occurring at excitation of the welding arc (Review). Paton Weld. J. 9, 43–48.

Mičian, M., Harmaniak, D., Nový, F., Winczek, J., Moravec, J., Trško, L. (2020). Effect of the t8/5 cooling time on the properties of S960MC steel in the HAZ of welded joints evaluated by thermal physical simulation. Metals 10 (2), 229.

Mičian, M., Frátrik, M., Kajánek, D. (2021). Influence of welding parameters and filler material on the mechanical properties of HSLA steel S960MC welded joints. Metals 11 (2), 305.

Mohammed, M.S., Hamdey, M.D., Kareem, A.H., Majdi, H.S. (2024). Investigation of copper backing plate effects in stainless steel welding distortion, heat distribution, and residual stress. J. Heat Technol. 42 (4), 1434-1446.

Moslemi, N., Gohery, S., Abdi, B., Sudin, I., Ghandvar, H., Redzuan, N., Rhee, S. (2022). A novel systematic numerical approach on determination of heat source parameters in welding process. J. Mater. Res. Technol. 18, 4427-4444.

Njoku, R.E., Suleiman, I.Y., Ogheneme, O.C., Mu’azu, K., Sirajo, M.Z., Sochima, E.V., Raheem, R. A., Akponah, O., Omoraka, A., Amhenrior, E.O., Ijeamiran, M.T., Amamchukwu, K.C. (2025). Effect of welding parameters on mechanical and microstructure behaviours of welded joints in low-carbon steels for engineering applications. J. Mater. Environ. Sci. 16 (4), 591–601. https://www.jmaterenvironsci.com

Smith, H. (2015). Microstructure and mechanical properties of the fusion and heat-affected zones of a laser welded DP780 steel. Doctoral dissertation.‏

Teixeira da Silva, G., Pereira de Gouveia, L., Toledo de Lima, E., Santos, J.P. (2024). Numerical Study of the Effects of Residual Stress in Welded Pipe Joints.

Wang, Q., Zhou, H., Zhao, L., Chen, X., Liu, S., Jiang, H., Shen, K, Guo, D. (2025). Microstructural Evolution and Fracture Mechanisms of After-Service P92 Welded Joints in Ultra-Supercritical Units. J. Mater. Eng. Perform 35, 6394-6408.‏

Wu, Q., Zikry, M.A. (2014) Microstructural modeling of crack nucleation and propagation in high strength martensitic steels. Int. J. Solids. Struct. 51 (25-26), 4345–4356.