M23C6析出相对节镍型奥氏体不锈钢冷轧表面裂纹的影响

为找出生产的节镍型奥氏体不锈钢冷卷表面裂纹形成原因,通过光学显微镜、扫描电镜对表面裂纹进行检测分析并结合热处理试验及热力学软件JMatPro进行分析计算研究。检测分析发现裂纹处晶界存在大量的析出相,据此推测析出相是导致钢材冷轧形成表面裂纹的主要原因。模拟连续退火工艺开展热处理试验,结果表明正常退火工艺无法完全消除热轧工序钢卷晶界处聚集的大量析出相。计算研究该成分体系下奥氏体不锈钢的平衡相图,结合能谱及透射电镜衍射斑点分析,结果表明M₂₃C₆碳化物的沉淀温度范围为500～925 ℃,钢卷从高温缓慢冷却下来会析出M₂₃C₆碳化物,析出鼻温区为850～900 ℃。以此结合实际工艺流程对减少钢卷中M₂₃C₆碳化物析出提出了可能的措施。

Effects of M23C6 precipitated phase on surface crack of cold-rolled low-nickel austenitic stainless steel

In order to find out the causes of surface cracks of cold-rolled low-nickel austenitic stainless steel strip produced by Liuzhou Steel, the surface cracks were detected and analyzed by the optical microscope and the scanning electron microscope, and analyzed and calculated by combining with heat treatment test and thermodynamic software JMatPro. It was found that there were a large number of precipitated phases at the grain boundary of the cracks, and accordingly, it was presumed that the precipitated phase was the main cause of surface cracks on products during cold rolling. The heat treatment test was carried out by simulating the continuous annealing process. The results showed that the normal annealing process cannot completely eliminate the large amount of precipitated phases accumulated at the grain boundary of steel coil during hot rolling process. The equilibrium phase diagram of austenitic stainless steel under this composition system was calculated and studied by combining with energy spectrum and TEM diffraction spot analysis. The results showed that the precipitation temperature of M₂₃C₆ carbide ranged from 500 to 925 ℃. When the steel coil cooled down slowly from high temperature, M₂₃C₆ carbide would be precipitated out, and the peak precipitation temperature was about 850-900 ℃. The possible measures to reduce the amount of M₂₃C₆ carbide precipitates in steel coil were put forward based on the actual process flow.