回火温度对Q1100超高强钢组织和性能的影响

采用力学性能测试、显微组织观察、扫描电镜观察,研究回火温度对Q1100超高强钢组织和性能的影响规律。结果表明:试验钢900 ℃保温后水淬再200~300 ℃回火后,为回火板条马氏体组织;在 400 ℃和500 ℃回火后,为回火屈氏体组织;在600 ℃回火后,为回火索氏体组织。试验钢具有较高的回火稳定性,在400~600 ℃回火时,α铁素体仍保持板条马氏体的形状和位向。在200 ℃回火后,小角度晶界含量较多,阻碍微裂纹扩展,韧性较好,随着回火温度的升高,小角度晶界占比逐渐减少,在400 ℃回火后,小角度晶界占比较少,碳化物的析出恶化试验钢的韧性,发生了回火脆性,韧性最差,500 ℃和600 ℃回火后,试验钢的小角度晶界占比较400 ℃相差不明显,但试验钢回复程度较大且600 ℃回火发生部分再结晶,回火软化作用较大,韧性较高。当回火温度为200 ℃时,试验钢具有最佳的综合性能,屈服强度为1164.38 MPa,抗拉强度为1429.70 MPa,断后伸长率为14.66%,硬度为430.27 HV3,标准试样-40 ℃冲击吸收能量为92.30 J。

Effect of tempering temperature on microstructure and properties of Q1100 ultra-high strength steel

Effect of tempering temperature on microstructure and properties of Q1100 ultra-high strength steel was studied by mechanical properties test, metallographic observation and SEM observation. The results show that the tested steel is composed of tempered lath martensite when water quenched from 900 ℃ and then tempered at 200-300 ℃. After tempering at 400 ℃ and 500 ℃, the microstructure is tempered troostite. After tempering at 600 ℃, the microstructure is tempered sorbite. The tested steel has high tempering stability, the α ferrite still maintains the shape and orientation of lath martensite when tempered at 400-600 ℃. After tempering at 200 ℃, the content of low angle grain boundary is high, which hinders the propagation of microcracks and the steel has good toughness. With the increase of tempering temperature, the proportion of low angle grain boundary decreases gradually. After tempering at 400 ℃, the proportion of low angle grain boundary is relatively small, the precipitation of carbides deteriorates the toughness of the tested steel, the tempering brittleness occurs and results in the worst toughness. After tempering at 500 ℃ and 600 ℃, the proportion of low angle grain boundary is not significantly different from that at 400 ℃, but the recovery degree of the microstructure is large and partial recrystallization occurs after tempering at 600 ℃. The tempering softening effect is large and the toughness is high. When the tempering temperature is 200 ℃, the tested steel has the best comprehensive properties, of which the yield strength is 1164.38 MPa, the tensile strength is 1429.70 MPa, the elongation after fracture is 14.66%, the hardness is 430.27 HV3, and the impact absorbed energy of the standard specimen at -40 ℃ is 92.30 J.