热处理对1000MPa级工程机械结构用钢组织和性能的影响

Effect of heat treatment on the microstructure and mechanical properties of 1000MPa grade structural steel for construction machinery

设计了一种低碳Mn-Mo-Nb-Cu-B系超高强度工程机械结构用钢,研究了在同种成分条件下TMCP(thermo-mechan-ical control-process)+回火与控轧+直接淬火+回火两种工艺对钢组织和性能的影响.对比分析了热处理前后钢板各项力学性能和组织的变化.结果表明,两种工艺条件下钢的屈服强度和冲击性能的变化趋势相似,经500～620℃回火1h后钢的屈服强度均有大幅度提高.控轧+直接淬火+回火得到的钢板综合性能明显优于TMCP+回火,前者在600℃回火后屈服强度仍达到1000MPa以上,同时延伸率达到18%,-40℃冲击功大于30J,而后者塑性较好但强度稍低;随回火温度的升高,控轧+直接淬火+回火工艺条件下的组织演化速度要快于TMCP+回火工艺.

A low-carbon Mn-Mo-Nb-Cu-B ultra high strength structural steel for construction machinery was designed and the effect of TMCP （thermo-mechanical control process） ＋ tempering （TMCP＋T） technology and controlled rolling ＋ direct quenching and tempering （CR＋DQ＋T） technology on its microstructure and mechanical properties under the same composition was studied.The changes in mechanical properties and microstructures of the steel plates before and after heat treatment were comparatively analyzed.The results show that after tempering from 500℃ to 620℃ for 1h,there is a substantial increase of the steel plates in yield strength.The performance of the steel plates treated by CR＋DQ＋T process is obviously superior to that by TMCP＋T process,and the yield strength of the former is still more than 1000MPa after tempering at 600℃.Besides,the elongation can reach 18% and the impact energy at-40℃ is more than 30J.However,the plasticity of the latter is better but the strength slightly lower.With the tempering temperature increasing,the evolution speed of microstructures under the condition of CR＋DQ＋T is more quickly than that under the condition of TMCP＋T.