低碳钢淬火等温碳配分中粒状贝氏体组织演变及性能

利用彩色金相、扫描电镜及拉伸实验等方法,研究了IQPB热处理工艺下低碳硅锰钢在450℃时不同等温时间淬火碳配分工艺对其组织及力学性能影响。结果表明,经不同时间等温碳配分工艺处理,实验钢显微组织基本由粒状贝氏体及粒状组织构成。当配分时间在200~600s时,晶界边缘大块状M/A岛数量逐渐减少,但细小颗粒状M/A岛数量逐渐增多并趋于有序化排列,导致抗拉强度升高,伸长率降低。随碳配分时间延长,细小颗粒状M/A岛又趋于弥散化排列,并且当碳配分时间大于1 200s时出现无碳化物板条贝氏体,其贝氏体板条间的薄膜状残余奥氏体更加稳定,同时受弥散排列的细小颗粒状M/A岛影响,伸长率得到提高,抗拉强度减少。

Granular bainite microstructure evolution and mechanical properties of low carbon steel in quenching isothermal carbon partition process

The influence of different time of carbon partition isothermal quenching treatment at 450 ℃ on the organization and mechanical properties of low carbon Si-Mn steel was investigated by the color metallography,scanning electron microscopy and tensile test method in the I&Q&PB process.The results show that experimental steel microstructure consists essentially of granular bainite and granular structure after various times isothermal carbon partitioning process.When the partition time is in the range of 200-600s,the big block M/A island on grain boundary edge diminishes,but the fine granular M/A island increases and has a gradually increased ordered packing,which results in higher tensile strength and lower elongation.With the extension of carbon partitioning time,fine granular M/A island tends to dispersive arrangement,and the carbide-free lath bainite appears when carbon partition time is longer than the 1 200 s.The film residual austenite between the bainitic ferrite laths is more stable.Under the influence of the fine granular dispersion arrangement M/A islands,the elongation is improved and the tensile strength is decreased.