低碳钢淬火等温碳配分中粒状贝氏体组织演变及性能

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

利用彩色金相、扫描电镜及拉伸实验等方法,研究了I&Q&PB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。

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 mi- croscopy and tensile test method in the I＆Q＆PB process. The results show that experimental steel microstructure con- sists essentially of granular bainite and granular structure after various times isothermal carbon partitioning process, When the partition time is in the range of 200 - 600 s, 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 arrange- ment, and the carbide-free lath bainite appears when carbon partition time is longer than the 1 200 s. The film residual austenite between the bainitie 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.