罩式退火Ti-IF钢的粗晶缺陷成因及对策

Cause and countermeasure of coarse grain defect in batch annealed Ti-IF steel

通过对罩式退火卷粗晶缺陷分布、不同程度粗晶缺陷试样中FeTiP的析出和Ti-IF钢FeTiP析出溶解温度及晶粒长大行为的分析,找到了粗晶缺陷的成因,并得到了解决粗晶缺陷的方法。结果表明:780℃或略高的温度是晶粒粗化临界温度,FeTiP析出相细小粒子的溶解导致了析出相粒子分布状态发生明显变化,此为诱发晶粒异常长大导致粗晶缺陷的根本原因。钢卷外圈局部过热导致退火温度超过了780℃,导致钢卷外圈产生了粗晶缺陷,通过在罩式炉退火工艺高温升温阶段添加适温保温平台,可有效解决粗晶缺陷问题。

Based on the analysis of distribution of coarse grain defects,the precipitation of FeTiP in specimen with different degree of coarse grain defects,and the precipitate dissolution temperature of FeTiP in the Ti-IF steel and the grain growth behavior,the causes of coarse grain defects were analyzed,and the method to solve the coarse grain defects was suggested.The results show that annealing at 780℃or slightly higher the temperature becomes the grain coarsening critical temperature,and the dissolution of Fe Ti P precipitate phase significantly change the distribution state of precipitate phase,which becomes the root cause of abnormal grain growth and coarse grain defects.The local overheating of the outer ring in the steel coil due to the annealing temperature exceeding 780℃causes the abnormal growth of grains in the outer ring of the steel coil and leads to the occurrence of coarse grain defects.The problem of coarse grain defects can be effectively solved by adding a heat insulation platform at a certain temperature during the high temperature rising stage of the batch annealing process.