J55钢连铸板坯凝固与固态相变调控热力学分析

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。

Thermodynamic analysis on solidification and solid phase transformation control of J55 steel continuous casting slab

The peritectic point during solidification and Continuous Cooling Transformation(CCT) curve of J55 micro-alloyed steel were calculated on thermodynamics. The grain size and micro-structure of the specimen during solidification were observed by confocal laser scanning microscopy(CLSM). Considering the impact of alloy elements on phase diagram， the calculating results show that J55 steel is critical hyper-peritectic steel， with 69.8% of the δ phase in the process of the peritectic reaction. The CCT curve moves to the right with the increase of grain size. The grain size and microstructure under the in-situ observation are identical with the results predicted by the calculated CCT curves when they are in the same cooling rate. The thermodynamic analysis of J55 steel can be conductive to minimize surface transverse crack sensitive by ingredient and microstructure control during continuous casting and hot charging processes.