等温淬火工艺对超高强贝氏体钢组织性能影响

针对低碳超高强贝氏体钢在不同等温淬火工艺下的组织和力学性能演变规律进行研究.结果表明:与一阶段等温淬火工艺相比，两阶段工艺下组织中贝氏体量增加，马氏体量相对减少，致使实验钢的屈服强度高达1178MPa，提高58%，延伸率从7.7%升高到14.4%，单位冲击韧性达到66J/cm²，提升16%.对比研究不同等温淬火工艺下实验钢的强塑性匹配发现，两阶段工艺A₃(240℃等温2h后再270℃等温1h)条件下实验钢的强塑积可达21888MPa·%.通过两阶段工艺，可消除实验钢中由于Mn元素偏析造成的马氏体带，获得相对均匀的贝氏体组织，从而使得实验钢的强度和韧性同时提高.

Effect of Austempering Process on Microstructure and Mechanical Property of Ultra-high Strength Bainitic Steel

The effect of different austempering processes on microstructure evolution and mechanical property of low carbon ultra-high strength bainitic steels was studied. The results show that compared with the one-stage austempering process， the amount of bainite increases and the content of martensite decreases in the two-stage process， which result that the yield strength of the experimental steel increases 58% and is up to 1178MPa， the elongation increases from 7.7% to 14.4% and the impact toughness increases 16% and reaches 66J/cm². Comparing the strength and plasticity matching of the corresponding experimental steels under different heat treatments， it is found that the product of strength and elongation of the steel can reach 21888MPa·% under the A₃(240℃for 2h and then 270℃for 1h) two-stage process condition. Under the two-stage process conditions， the martensite band due to Mn segregation in the steel can be eliminated and a relatively uniform bainite structure can be obtained， so that the strength and toughness of the experimental steel can be improved simultaneously.