关键词: 渗碳体, TRIP钢, 回火, 临界退火, 贝氏体转变, 组织遗传性

Abstract: By utilizing tempering process, initial microstructure with different cementite characteristics was prepared. Subsequent intercritical annealing was carried out to obtain retained cementite with different characteristics, and effect of cementite characteristics on the final microstructure of TRIP steel was investigated. The results indicate that cementite with varying number densities, sizes, and degrees of Mn-riched can be obtained after different pre-tempering processes, which is difficult to dissolve during the annealing, and the Mn-riched cementite remains in the final microstructure. After intercritical annealing, the retained cementite acts as nucleation sites to promote bainite transformation in the partitioning stage, thereby reducing the content of secondary martensite. The bainite content increases from 49.5% without tempering to 62.2% tempered at 550 ℃ for 4 h. By fitting the relationship between the number density, size, and Mn-rich of cementite before and after dissolution (intercritical annealing) and the bainite content in the final microstructure, it is found that the number density of the retained cementite is a key factor affecting bainite transformation. The greater the amount of the retained cementite, the higher the bainite content in the final microstructure, while the effects of cementite size and Mn-rich are relatively minor.

Key words: cementite, TRIP steel, tempering, intercritical annealing, bainite transformation, microstructure inheritance