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对J55微合金钢凝固相变包晶点和连续冷却过程的CCT曲线进行了热力学计算分析,并利用高温共聚焦显微镜原位观察了试样凝固过程的晶粒度和组织。考虑各种合金成分的贡献,计算表明,J55钢属于微合金临界过包晶钢,凝固相变过程中δ相的比例可达69.8%。J55钢CCT曲线随晶粒增大向右移动。基于原位观察的晶粒度对其CCT曲线进行热力学计算和相变组织的对比分析,结果表明,在相同冷却速率下两者所获得的组织基本一致。研究结果有助于指导通过成分和组织调控,降低J55钢连铸和热装热送过程中表面横裂纹敏感性。
The CCT curves of the solidification phase transformation point and the continuous cooling process of J55 microalloyed steel were calculated by thermodynamic calculation. The grain size and microstructure of the solidified phase were observed by high temperature confocal microscope. Considering the contribution of various alloy compositions, the calculation shows that J55 steel belongs to the micro-alloyed critical peritectic steel, and the δ phase proportion in the solidification phase transformation can reach 69.8%. J55 steel CCT curve with the grain to move to the right. Based on the grain size of the in-situ observation, the CCT curves were calculated thermodynamically and compared with the phase transformation microstructure. The results show that the microstructure of the CCT curves obtained at the same cooling rate is basically the same. The results help guide the reduction of surface transverse crack susceptibility in continuous casting and hot charging of J55 steel through compositional and tissue control.