Mechanism of hot-rolling crack formation in lean duplex stainless steel 2101

Abstract

The thermoplasticity of duplex stainless steel 2205 (DSS2205) is better than that of lean duplex steel 2101 (LDX2101), which undergoes severe cracking during hot rolling. The microstructure, microhardness, phase ratio, and recrystallization dependence of the deformation compatibility of LDX2101 and DSS2205 were investigated using optical microscopy (OM), electron backscatter diffraction (EBSD), Thermo-Calc software, and transmission electron microscopy (TEM). The results showed that the phase-ratio transformations of LDX2101 and DSS2205 were almost equal under the condition of increasing solution temperature. Thus, the phase transformation was not the main cause for the hot plasticity difference of these two steels. The grain size of LDX2101 was substantially greater than that of DSS2205, and the microhardness difference of LDX2101 was larger than that of DSS2205. This difference hinders the transfer of strain from ferrite to austenite. In the rolling process, the ferrite grains of LDX2101 underwent continuous softening and were substantially refined. However, although little recrystallization occurred at the boundaries of austenite, serious deformation accumulated in the interior of austenite, leading to a substantial increase in hardness. The main cause of crack formation is the microhardness difference between ferrite and austenite.

Keywords

duplex stainless steel / hot rolling / crack formation / thermoplasticity / grain size / precipitates / softening mechanisms

References

[1] Momeni A., Kazemi S., Bahrani A. Hot deformation behavior of microstructural constituents in a duplex stainless steel during high-temperature straining. Int. J. Miner. Metall. Mater., 2013, 20(10): 953.

[2] Iza-Mendia A., Piñol-Juez A., Urcola J.J., Gutiérrez I. Microstructural and mechanical behavior of a duplex stainless steel under hot working conditions. Metall. Mater. Trans. A, 1998, 29(12): 2975.

[3] Hänninen H., Romu J., Ilola R., Tervo J., Laitinen A. Effects of processing and manufacturing of high nitrogen-containing stainless steels on their mechanical, corrosion and wear properties. J. Mater. Process. Technol., 2001, 117(3): 424.

[4] Siegmund T., Werner E., Fischer F.D. On the thermomechanical deformation behavior of duplex-type materials. J. Mech. Phys. Solids, 1995, 43(4): 495.

[5] Ginsztler J., Mészáros I., Dévényi L., Hidasi B., Potgieter J.H. Magnetic investigations of stainless steels. Int. J. Pressure Vessels Piping, 1995, 61(2-3): 471.

[6] Jia N., Peng R.L., Wang Y.D., Johansson S., Liaw P.K. Micromechanical behavior and texture evolution of duplex stainless steel studied by neutron diffraction and self-consistent modeling. Acta Mater., 2008, 56(4): 782.

[7] Momeni A., Dehghani K. Hot working behavior of 2205 austenite–ferrite duplex stainless steel characterized by constitutive equations and processing maps. Mater. Sci. Eng. A, 2011, 528(3): 1448.

[8] Yang Y.H., Yan B. The microstructure and flow behavior of 2205 duplex stainless steels during high temperature compression deformation. Mater. Sci. Eng. A, 2013, 579, 194.

[9] Liu Y.Y., Yan H.T., Wang X.H., Yan M. Effect of hot deformation mode on the microstructure evolution of lean duplex stainless steel 2101. Mater. Sci. Eng. A, 2013, 575, 41.

[10] Lilias M., Johansson P., Liu H.P., Olsson C.O.A. Development of a lean duplex stainless steel. Steel. Res. Int., 2008, 79(6): 466.

[11] Zou D.N., Wu K., Han Y., Zhang W., Cheng B., Qiao G.J. Deformation characteristic and prediction of flow stress for as-cast 21Cr economical duplex stainless steel under hot compression. Mater. Des., 2013, 51, 975.

[12] Pilhagen J., Sandström R. Influence of nickel on the toughness of lean duplex stainless steel welds. Mater. Sci. Eng. A, 2014, 602, 49.

[13] Li J.Y., Liu H.N., Huang P.W. Effects of pre-precipitation of Cr₂N on microstructures and properties of high nitrogen stainless steel. J. Cent. South. Univ., 2012, 19(5): 1189.

[14] Allain S., Chateau J.P., Bouaziz O., Migot S., Guelton N. Correlations between the calculated stacking fault energy and the plasticity mechanisms in Fe–Mn–C alloys. Mater. Sci. Eng. A, 2004, 387-389, 158.

[15] Lin G., Zhang Z.X., Song H.W., Tong J., Zhou C.D. Investigation of the hot plasticity of duplex stainless steel. J. Iron. Steel. Res. Int., 2008, 15(6): 83.

[16] Atamert S., King J.E. Elemental partitioning and microstructural development in duplex stainless steel weld metal. Acta Metall. Mater., 1991, 39(3): 273.

[17] Lindsley B.A., Marder A.R. The morphology and coarsening kinetics of spheroidized Fe-C binary alloys. Acta Mater., 1997, 46(1): 341.

[18] Pehlke R.D., Elliott J.F. Solubility of nitrogen in liquid iron alloys: 1. Thermodynamics. Trans. Inst. Min. Metall. Eng., 1960, 218(6): 1008.

[19] Pehlke R.D., Elliott J.F. Solubility of nitrogen in liquid iron alloys: 2. Kinetics. Trans. Inst. Min. Metall. Eng. A, 1963, 227(4): 844.

[20] Muthupandi V., Srinivasan P.B., Seshadri S.K., Sundaresan S. Effect of weld metal chemistry and heat input on the structure and properties of duplex stainless steel welds. Mater. Sci. Eng. A, 2003, 358(1-2): 9.

[21] Fu L.M., Fan L.K., Li Z.G., Sun N.R., Wang H.R., Wang W., Shan A.D. Yield behaviour associated with stacking faults in a high-temperature annealed ultra-low carbon high manganese steel. Mater. Sci. Eng. A, 2013, 582, 126.

[22] Chen X.H., Ren X.P., Xu H., Tong J.G., Zhang H.Y. Effect of superplastic deformation on the bonding property of 00Cr25Ni7Mo3N duplex stainless steel. Int. J. Miner. Metall. Mater., 2012, 19(4): 317.