终冷温度对直接淬火配分超高强度钢组织与性能的影响

Effects of interrupt temperature on microstructure and mechanical properties of ultra high strength steel after direct quenching and partitioning

研究了不同淬火终冷温度对直接淬火配分超高强钢组织与力学性能的影响规律。结果表明:随淬火终冷温度升高,抗拉强度快速降低,屈服强度缓慢下降,冲击吸收能量先增加后降低,伸长率明显增加。直接淬火到马氏体相变区后空冷的组织为板条马氏体和残留奥氏体的复相组织。提高淬火终冷温度,马氏体板条粗化,残留奥氏体的含量增加,导致强度降低而塑韧性提高。淬火终冷温度为360℃时残留奥氏体的含量最高,为8.8%,但由于组织粗化,出现粗大板条马氏体,韧性降低。综合考虑,淬火终冷温度为320℃时具有最好的强度和塑韧性能的匹配,抗拉强度为1632 MPa,冲击吸收能量和伸长率分别为20 J和14.1%。

Effects of interrupt quenching temperature on mechanical properties and microstructure of a ultra high strength steel after direct quenching and partitioning were investigated. The results show that with increasing the interrupt quenching temperature, the tensile strength decreases rapidly, but the yield strength decreases slowly. The impact absorbed energy increases at first and then decreases and the elongation increases obviously with increase of the interrupt quenching temperature. Microstructure of the tested steel consists of lath martensite and retained austenite. With the increase of the interrupt quenching temperature, the martensite lath coarsens, and the content of retained austenite increases. The highest retained aastenite fraction of 8.8% can be obtained when the interrupt quenching temperature is 360℃, but the impact absorbed energy decreases due to the coarsened martensite. When the interrupt quenching temperature is 320℃, a preferable combination of strength and ductility, i.e. the tensile strength of 1632 MPa, the elongation of 16% and the impact energy of 26 J at -20℃ can be obtained.