【摘要】 目前轧态42CrMo棒材过高的硬度严重影响后序加工，可通过优化轧制与冷却工艺制度降低其硬度。通过DIL805A相变仪和S60/58507同步热分析仪绘制了42CrMo钢的动态CCT曲线，并以此为基础探究了轧制和冷却工艺对42CrMo钢组织转变和硬度的影响。研究表明：单道次控轧实验中，不同的轧制参数下，42CrMo钢中铁素体均优先在原始奥氏体晶界处发生相变，随后在原始奥氏体晶内形核生长，通过降低变形温度、增大真应变可明显增加铁素体转变量从而降低其轧后硬度；双道次变形后控冷实验中，超快冷—缓冷—空冷工艺可进一步增加42CrMo钢冷后铁素体含量，缓冷段冷速为0.1℃/s时，其铁素体体积分数可达41.79%,使得42CrMo钢轧态硬度远低于国标硬度要求(不大于241HV);当冷却过程中缓冷段冷速不超过0.2℃/s时，其轧后硬度满足行业对于冷成形用42CrMo钢的硬度要求(不大于220HV)。更多还原

【Abstract】 The excessively high hardness of rolling-state 42CrMo steel bars significantly affects subsequent processing. Optimizing the rolling and cooling processes is crucial for reducing the hardness. Dynamic CCT curves of 42CrMo steel were drawn using the DIL805A phase transformation instrument and S60/58507 simultaneous thermal analyzer to investigate the effects of rolling and cooling processes on the microstructure transformation and hardness. The study reveals that during single-pass controlled rolling, ferrite preferentially nucleates at original austenite grain boundaries under various rolling parameters, followed by nucleation and growth within the grains. Lowering deformation temperature and increasing deformation degree significantly increase ferrite content and reduce hardness. In two-pass deformation and controlled cooling experiments, the ultra-fast cooling—slow cooling—air cooling process further raises ferrite content. At a slow cooling rate of 0.1 ℃/s, ferrite volume fraction reaches 41.79%, achieving rolling-state hardness well below the standard(≤241HV). A slow cooling rate slower than 0.2 ℃/s ensures hardness meet cold-forming requirements(≤220HV).更多还原