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本文研究了30CrMnSiNi2A及18Cr2Ni4WA钢连续冷却或等温淬火及回火的组织、性能变化,测定了30CrMnSiNi2A钢等温淬火后M/A岛碳分布和Ar回火转变动力学。在超高压电镜中直接观察了Ar回火转变的动态过程,并在此基础上重点探讨了以贝氏体为主的组织中Ar回火转变特点、稳定性及其与钢的强韧性的关系。结果表明:Ar在低温回火时转变为下贝氏体,在中温回火时转变为上(或反)贝氏体;贝氏体转变提高Ar的稳定性。Ar的回火转变将影响钢的强韧性,Ar分解为上(或反)贝氏体、断续碳化物膜和回火冷却时转变为马氏体是引起回火脆性的重要因素,因此淬火工件、特别是以贝氏体为主要组织的工件宜在250～300℃回火。
In this paper, the microstructures and properties of 30CrMnSiNi2A and 18Cr2Ni4WA steels after continuous cooling or isothermal quenching and tempering were investigated. The kinetics of carbon distribution and Ar-tempering of M / A island after 30CrMnSiNi2A steel was quenched were measured. The dynamic process of Ar tempering transformation was directly observed in EHV electron microscope. On the basis of the above, the characteristics and stability of Ar temper transformation in bainite-based microstructure were mainly discussed, and its relationship with the toughness of steel . The results show that Ar is transformed to lower bainite at low tempering temperature and to upper (or opposite) bainite at intermediate temperature tempering. The transformation of bainite improves the stability of Ar. Ar tempering transformation will affect the toughness of steel, Ar decomposition into the upper (or reverse) bainite, intermittent carbide film and quenching into martensite is an important factor in causing temper brittleness, quenching Workpieces, especially those with bainite as the main structure, should be tempered at 250-300 ° C.