回火时间对1800 MPa级热成形钢组织和性能的影响

doi:10.13251/j.issn.0254-6051.2022.08.018

摘要/Abstract

摘要： 采用扫描电镜、电子背散射衍射技术、室温拉伸试验等研究了1800 MPa级热成形钢经930 ℃保温4 min保压淬火后在200 ℃回火不同时间(10~30 min)对其组织和力学性能的影响。结果表明,随着回火时间的延长,试验钢的抗拉强度变化较小,其屈服强度和断后伸长率均呈先增后减的趋势。经20 min回火后,马氏体亚晶粒尺寸最小;回火10 min后,组织中的小角度晶界最多。200 ℃回火10 min后由于试验钢的残余应力释放、马氏体亚晶粒尺寸减小和小角度晶界增多,综合影响下热成形钢的综合力学性能最佳,其抗拉强度为1844 MPa,断后伸长率从淬火态的8.27%提升到11.78%,强塑积达21 GPa·%以上,说明短时回火有利于该超高强度钢的综合性能提高及其热成形件的可靠应用。

关键词: 1800 MPa级热成形钢, 低温回火, 微观组织, 力学性能

Abstract: Effect of tempering time (10-30 min) at 200 ℃ on microstructure and mechanical properties of a 1800 MPa hot stamping steel after flat forming at 930 ℃ for 4 min was studied by scanning electron microscope, electron backscattering diffraction and tensile test at room temperature. The results show that with the extension of tempering time, the tensile strength of the tested steel changes a little, while the yield strength and elongation after fracture both increase first and then decrease. The martensite sub-grain size is the smallest when tempered for 20 min, while the low angle grain boundary is the most when tempered for 10 min. After tempering at 200 ℃ for 10 min, the comprehensive mechanical properties of the hot stamping steel are the best due to the release of residual stress, the decrease of martensite sub-grain size and the increase of low angle grain boundary, of which the tensile strength is 1844 MPa, the elongation increases from 8.27% of quenched tested steel to 11.78%, and the product of strength and elongation reaches more than 21 GPa·%. It is concluded that short-time tempering is beneficial to the improvement of comprehensive properties of the tested ultra-high strength steel and the reliable application of hot stamping parts.

Key words: 1800 MPa hot stamping steel, low temperature tempering, microstructure, mechanical properties

中图分类号:

TG142.2

宋宁宏, 林超, 毕文珍, 王武荣, 韦习成. 回火时间对1800 MPa级热成形钢组织和性能的影响[J]. 金属热处理, 2022, 47(8): 112-117.

Song Ninghong, Lin Chao, Bi Wenzhen, Wang Wurong, Wei Xicheng. Effect of tempering time on microstructure and properties of 1800 MPa hot stamping steel[J]. Heat Treatment of Metals, 2022, 47(8): 112-117.

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