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针对42CrMo钢大棒材轧后冷却过程中的组织性能控制与表面裂纹问题,在Gleeble热模拟平台研究了42CrMo钢的组织转变规律及其动态CCT曲线,并建立了150 mm大棒材轧后输送和缓冷过程的温度-组织-应力场耦合有限元模型,对轧件轧后温度变化、显微组织和应力状态进行了模拟分析。结果表明,当采用缓冷工艺且轧件入坑温度高于600℃时,棒材横截面内组织主要为珠光体和铁素体,与工业现场取样结果一致,符合对大棒材切削加工性能的实际要求。空冷条件下,轧件表面金属处于拉应力状态且最大周向应力为13 MPa,缓冷工艺能够降低工件内部温度梯度和应力水平,对抑制表面裂纹萌生有重要作用。
Aiming at the microstructure control and surface crack in the cooling process of 42CrMo steel bar after rolling, the microstructure transformation and dynamic CCT curve of 42CrMo steel were studied on the Gleeble thermal simulation platform. After the 150 mm large bar rolling The coupled finite element model of temperature-tissue-stress field in the process of conveying and slow cooling is simulated and the temperature changes, microstructure and stress state after rolling are simulated. The results show that the microstructure of the cross section of the bar is mainly composed of pearlite and ferrite when the slow cooling process is adopted and the temperature of the workpiece is higher than 600 ℃. It is consistent with the sampling results at the industrial site and is in good agreement with the cutting performance The actual requirements. Under the condition of air cooling, the metal on the rolling surface is in the state of tensile stress and the maximum circumferential stress is 13 MPa. The slow cooling process can reduce the temperature gradient and stress level inside the workpiece, which plays an important role in suppressing the surface crack initiation.