采用SEM、TEM等方法研究了不同回火温度对300M超高强度钢的显微组织和力学性能的影响。结果表明,300M钢经870℃淬火后,在290～320℃范围内回火,显微组织为板条马氏体、下贝氏体和残留奥氏体组成。随着回火温度的升高,板条马氏体宽度由260 nm增加到437 nm,位错密度减小,下贝氏体含量增多;合金的抗拉强度有所下降,韧性呈上升趋势,而屈服强度、伸长率和断面收缩率变化较小。当回火温度为300℃时,强度、塑性和韧性达到一个最佳匹配,合金具有最优的综合力学性能。 The effects of different tempering temperatures on the microstructure and mechanical properties of 300M ultra-high strength steel were studied by SEM and TEM. The results show that 300M steel is quenched at 870 ℃ and tempered at 290 ~ 320 ℃. The microstructure is lath martensite, lower bainite and retained austenite. With the increase of tempering temperature, the width of martensite increases from 260 nm to 437 nm, the dislocation density decreases and the content of lower bainite increases. The tensile strength of the alloy decreases and the toughness increases. The yield strength, elongation and cross-sectional shrinkage change is small. When the tempering temperature is 300 ℃, the strength, ductility and toughness achieve the best match, the alloy has the best comprehensive mechanical properties.