Effects of Mn on microstructures and properties of hot rolled low carbon bainitic steels

Abstract

Two kinds of Mn-Si-Mo low carbon steels were designed to study the effects of Mn on the microstructures and properties of hot rolled low carbon bainitic steels. To reduce the production cost, a very low Mo content of 0.13% was added in both steels. After hot rolling, the mechanical properties of samples were tested. Microstructure was observed and analyzed by optical microscope and transmission electron microscope. The results show that the strength of tested steels increases with the increase in Mn content, while the elongation decreases. When Mn content increases, the bainite microstructure increases. The results can provide a theoretical basis for composition design and industrial production of low cost low carbon bainitic steels.

Keywords

manganese / low carbon bainitic steel / hot rolling / strength

References

[1] Liu F, Xu G, Wang L, et al. In Situ Observation of Austenite Grain Growth of a Fe-C-Mn-Si Superbainite Steel[J]. Int. J. Miner. Metall. Mater., 2013, 20(11): 1060-1066.

[2] Hu H J, Xu G, Liu F, et al. Dynamic Observation of Twin Evolution During Austenite Grain Growth in an Fe-C-Mn-Si Alloy[J]. Int. J. Mater. Res., 2014, 105(4): 337-341.

[3] Xu G, Liu F, Wang L, et al. A New Approach to Quantitative Analysis of Bainitic Transformation in a Superbainite Steel[J]. Acta Mater., 2013, 68(11): 833-836.

[4] Hu Z W, Xu G, Hu H J, et al. In Situ Measured Growth Rates of Bainite Plates in an Fe-C-Mn-Si Superbainitic Steel[J]. Int. J. Miner. Metall. Mater., 2014, 21(4): 371-378.

[5] Shi K, Chen J B, Hou H, et al. Impact Toughness Scattering of Bainitic Steel in the Ductile-brittle Transition Temperature Region[J]. J. Wuhan Univ. Technol.-Mat. Sci. Ed., 2016, 31(3): 636-643.

[6] Hu H J, Xu G, Zhang Y L, et al. Dynamic Observation of Bainite Transformation in a Fe-C-Mn-Si Superbainite Steel[J]. J. Wuhan Univ. Technol.-Mat. Sci. Ed., 2016, 30(4): 818-821.

[7] Zhang M Y, Zhu F X, Duan Z T, et al. Characteristics of Retained Austenite in TRIP Steels with Bainitic Ferrite Matrix[J]. J. Wuhan Univ. Technol.-Mat. Sci. Ed., 2011, 26(6): 1148-1151.

[8] Hu H J, Xu G, Zhou M X, et al. Effect of Mo Content on Microstructure and Property of Low-Carbon Bainitic Steels[J]. Metals, 2016, 6(8): 173-182.

[9] Zhou M X, Xu G, Wang L, et al. The Varying Effects of Uniaxial Compressive Stress on the Bainitic Transformation under Different Austenitization Temperatures[J]. Metals, 2016, 6(5): 119-130.

[10] Bhadeshia H K D H. Bainite in Steels[M]. 2001 Cambridge: Cambridge University Press.

[11] Lis A K. Mechanical Properties and Microstructure of ULCB Steels Affected by Thermomechanical Rolling, Quenching and Tempering[J]. J. Mater. Process. Technol., 2000, 106(1-3): 212-218.

[12] Zhang Z M, Cai Q W, Yu W, et al. Continuous Cooling Transformation Behavior and Kinetic Models of Transformations for an Ultra-Low Carbon Bainitic Steel[J]. J. Iron Steel Res. Int., 2012, 19(12): 73-78.

[13] Gorni A A, Mei P R. Austenite Transformation and Age Hardening of HSLA-80 and ULCB Steels[J]. J. Mater. Process. Technol., 2004, 155–156: 1513-1518.

[14] Liu X, Chen D M, Zhou L B, et al. Low Cost High Strength Si-Mn-Mo Bainitic Steel Bar[J]. J. Northwestern Polytechnical. Univ., 1994, 12(3): 449-452.

[15] Kang M K, Sun J L, Yang Q M. High-temperature Transmission Electron Microscopy in Situ Study of Lower Bainite Carbide Precipitation[J]. Metall. Trans. A, 1990, 21(3): 853-858.

[16] Yang Y, Chen X, Du Z M, et al. Influence of Tempering on Microstructure and Mechanical Property of Si-Mn-Mo Bainitic Steel[J]. Iron Steel Vanadium Titanium, 2011, 32(4): 63-66.

[17] Li H B, Liu X D, Jin B S, et al. Design and Manufacture of a New Low-carbon Bainitic Steel[J]. J. Jiamusi Univ. (Nat. Sci. Ed.), 2006, 24(1): 19-21.

[18] Hu G L, Xie X W. Heat Treatment of Steel[M]. 2010 Xi’an: Northwestern Polytechnical University Press.

[19] Liu S K, Zhang J. The Influence of the Si and Mn Concentrations on the Kinetics of the Bainite Transformation in Fe-C-Si-Mn Alloys[J]. Metall. Trans. A, 1990, 21(6): 1517-1525.

[20] Liu S K, Yang L, Zhang J, et al. Influence of Si and Mn on Morphology of Bainitic Ferrite and Kinetics of Bainite Transformation in Fe-C Alloy[J]. Acta Metall. Sinica, 1992, 28(12): 1-8.

[21] Fang H S, Feng C, Zheng Y K, et al. Creation of Air-Cooled Mn Series Bainitic Steels[J]. J. Iron Steel Res. Int., 2008, 15(6): 1-9.

[22] Chen J K, Vandermeer R A, Reynolds W T. Effects of Alloying Elements upon Austenite Decomposition in Low-C Steels[J]. Metall. Mater. Trans. A, 1994, 25(7): 1367-1379.

[23] Bradley J R, Aaronson H I. Growth Kinetics of Grain Boundary Ferrite Allotriomorphs in Fe-C-X Alloys[J]. Metall. Trans. A, 1981, 12(10): 1729-1741.

[24] Wang J, Van Der Wolk P J, Van Der Zwaag S. On the Influence of Alloying Elements on the Bainite Reaction in Low Alloy Steels during Continuous Cooling[J]. J. Mater. Sci., 2000, 35(17): 4393-4404.

[25] Butt M Z, Feltham P. Review Solid-solution Hardening[J]. J. Mater. Sci., 1993, 28(10): 2557-2576.

[26] Lu J F, Omotoso O, Wiskel J B, et al. Strengthening Mechanisms and Their Relative Contributions to the Yield Strength of Microalloyed Steels[J]. Metall. Mater. Trans. A, 2012, 43(9): 3043-3061.