Cr17Mn6Ni4Cu2N奥氏体不锈钢连铸坯组织及凝固模式

Microstructures and solidification mode of continuous casting slabs of austenitic stainless steel Cr17Mn6Ni4Cu2N

采用AOD＋LF精炼工艺冶炼,通过连铸工艺生产出Cr17Mn6Ni4Cu2N奥氏体不锈钢连铸坯,对其表面层和中心区域进行金相组织分析,并用电子探针分析组织中化学成分的变化.结果表明,连铸坯表面层上的组织均为在奥氏体基体上分布着不同形态的残余δ铁素体,由表及里δ铁素体的形态分别为骨架形,侧板条状和蠕虫状.根据组织形态确定出这种钢在连铸过程中的凝固模式为从液相中先析出δ铁素体,随后通过固相转变形成奥氏体.由连铸坯表面层铁素体的二次枝晶间距得到冷却速度,分析出冷却速度在5~20℃/s变化对凝固模式没有影响.

Continuous casting slabs oLaustenitic stainless steel Crl7Mn6Ni4Cu2N were prepared by using AOD and LF refine technique and continuous casting technique. Optical metallographic examination was performed for their surface layer and central region, and composition variation in microstructures was studied with electron probe microanalyzer to determine their casting microstructures. The result showed that morphologies of casting microstructures were all various residual δ-ferrite with the form of skeletal, lathy and vermiculate respectively inward into casting slabs on the austenitic matrix. According to the microstructure of continuous casting slabs, their solidification mode was determined that the ferrite solidified as primary phase, and subsequently the austenitic formed through solid state transformation. Cooling rates were determined by secondary dendrite arming spaces of ferrite on surface layer. Analysis result showed that cooling rates varying from 5-20 ℃/s had no influence on solidification mode.