研究了5NiCrMo低温钢的淬火+临界淬火+回火（QLT）热处理工艺，分析了回火温度对该钢组织和力学性能的影响。结果表明：试验钢经QLT热处理后，形成了回火马氏体、-铁素体与逆转变奥氏体的混合组织。560~640℃回火时，随温度提高，屈服强度降低，100℃冲击功先升高、在620℃回火时达到峰值后降低。深冷后保留的逆转变奥氏体显著影响试验钢的低温韧性。拉伸和冲击性能均满足要求的回火温度是600~620℃。%A complex heat treatment consisting of sequential processes of quenching, intercritical quenching and tempering (QLT, for brevity) imposed on 5NiCrMo cryogenic steel is investigated. The effect of tempering temperature on the microstructures and mechanical properties is particularly estimated. The results show that a mixed microstructure of tempered martensite, -ferrite and reversed austenite forms in the QLT-treated steel. As the tempering temperature increases from 560 to 640℃, the yielding strength decreases and the impact energy at 100℃increases initially, reaching the peak at 620℃followed by a decrease. The cryogenic toughness is significantly dependent on the volume fraction of the survivable reversed austenite. The QLT-treated steel tempered at 600~620℃can satisfy the requirements for the tensile and impact properties.
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