在线淬火型微合金高强钢的回火组织与性能

对在线淬火型微合金高强结构钢在400~600 ℃范围内进行回火40 min处理,以研究不同回火温度对试验钢显微组织和力学性能的影响。通过光学显微镜、扫描电镜等进行组织观察分析,同时测量试验钢回火后的强度、硬度及-40 ℃冲击吸收能量等进行力学性能分析。试验结果表明:随着回火温度的升高,试验钢强度及硬度整体呈下降趋势,冲击性能整体上升,并在450~500 ℃出现回火脆性区。同时随着回火温度升高,试验钢组织中马氏体逐渐宽化减少,铁素体含量增多。450 ℃回火时,试验钢的组织为回火托氏体,此时其屈服强度和硬度分别为840 MPa和304 HV3,断后伸长率为14.4%,-40 ℃冲击吸收能量为129 J,达到良好综合力学性能。

Tempered microstructure and properties of on-line quenched micro alloyed high strength steel

To investigate the effect of tempering temperature on microstructure and mechanical properties of the tested steel, the process of tempering at 400-600 ℃ for 40 min for micro alloyed high strength steel was carried out. The microstructure was analyzed by means of optical microscope and scanning electron microscope. At the same time, the strength, hardness and impact absorbed energy at -40 ℃ after tempering were measured to analyze the mechanical properties. The results show that with the increase of tempering temperature, the strength and hardness of the tested steel are reduced on the whole, and the impact absorbed energy shows a mainly increasing tendency. But the tempering brittleness appears at 450-500 ℃. The martensite in the tested steel gradually broadens and decreases with the increase of tempering temperature, and the ferrite content increases. When tempered at 450 ℃, the microstructure of the tested steel is troostite, the yield strength and hardness of the tested steel are 840 MPa and 304 HV3, the elongation after fracture is 14.4%, and the impact absorbed energy at -40 ℃ is 129 J, which indicates good comprehensive mechanical properties.