2507双相不锈钢热轧板表面起皮缺陷的特征及成因分析

Characteristics and causes of surface peeling defects on hot-rolled sheet of 2507 duplex stainless steel

针对2507双相不锈钢热轧板表面起皮缺陷问题,通过对热轧板取样,使用光学显微镜、扫描电镜和能谱仪观察起皮缺陷处表面,并进一步对基体处进行了观察,对比了两者金相组织特点以及物相组成,分析了起皮缺陷的成因及形成过程。研究发现:起皮缺陷处组织变形流向与基体明显不同,铁素体体积分数为83.97%,显著高于其基体的62.33%,认为是热轧过程中皮下有害夹杂物加重组织变形所致;在起皮缺陷处发现了大量不同于基体部分的高熔点大尺寸夹杂物,如硅氧化物、硅铝氧化物以及簇状钙镁硅氧化物,认为微裂纹是由于这些夹杂物与基体变形不协调所致,裂纹进一步扩展形成起皮缺陷。基于以上研究结果,提出了2507热轧板起皮缺陷形成机制。

To analyze the surface peeling defects on hot-rolled sheets of 2507 duplex stainless steel, the optical microscope, scanning electron microscope and energy spectrometer were used to observe the surface peeling defects of hot-rolled sheet and the matrix was studied. Comparing the characteristics of the metallographic structure and phase composition of the defects and the matrix, the cause and formation process of the peeling defects were analyzed. It is found that the deformation flow direction of the peeling defects is significantly different from that of the matrix. The proportion of ferrite is 83.97%, which is significantly higher than that of the matrix 62.33%. The harmful inclusions under the skin were considered to aggravate the structure deformation during hot rolling. A number of the large-size inclusions, e.g., silicon oxide, silicon aluminum oxide, and clustered calcium magnesium silicon oxide, with the high melting point are found at the peeling defects. The microcracks are caused by the inconsistent deformation of these inclusions with the matrix, and the cracks further grow to form peeling defects. Based on the above results, the formation mechanism of peeling defects on the hot-rolled sheet of 2507 duplex stainless steel is proposed.