440 MPa级高强度球扁钢的热处理工艺

采用金相显微镜、透射电镜、相分析等实验分析方法，研究了不同热处理工艺对10CrNiMoV球扁钢组织和力学性能的影响。结果表明，热轧或正火连续冷却过程中，形成了大量的粒状贝氏体，显著降低了钢的韧性。正火加高温回火处理后，粒状贝氏体得到了一定程度的分解，虽其屈服强度有所下降，但显著提高了10CrNiMoV球扁钢的低温韧性，?40 ℃冲击功达到117 J。通过正火＋控冷＋高温回火处理后，形成了一定量的多边形铁素体，并且粒状贝氏体得到了充分的分解，获得了良好的综合性能。

Heat treatment process of bulb flat steels with yield strength of 440 MPa

The effect of heat treatment process on microstructure and mechanical properties of 10CrNiMoV bulb flat steel are studied by means of optical microscope， transmission electron microscope， phase analysis and so on. The results show that a large number of granular bainite is formed in the period of rolling or normalizing continuous cooling. The low temperature toughness of the steel is decreased obviously with the formation of granular bainite. Akv-40 can be up to 117 J and the yield strength reduce to 420 MPa by normalizing + high tempering treatment， because the granular bainite are decomposed by normalizing + high tempering treatment. Furthermore， Akv-40 can be up to 180 J by normalizing＋controlled cooling＋high tempering treatment because of the granular bainite decomposed sufficiently.