1Cr18Ni9Ti冷轧不锈钢管表面白斑形成原因分析

采用冷轧工艺生产的1Cr18Ni9Ti不锈钢管内表面出现了大量白色斑点状缺陷，导致产品不能正常出厂交付。为确定白色斑点形成原因，使用扫描电子显微镜+能谱仪、金相显微镜、激光诱导击穿光谱仪,对该批钢管表面形貌、金相组织、晶粒度和微区成分进行了分析检验。结果表明：钢管内外表面都出现了表面增碳现象，内表面上的白斑缺陷区增碳最为严重，酸洗钝化时出现了严重的晶间腐蚀，表层晶粒大量剥落，使局部表面粗糙度变差，形成白斑缺陷。钢管表面除油脱脂不彻底使热处理过程中出现表面增碳是导致出现白斑缺陷的主要原因。

Formation analysis of white spot imperfections on cold rolling 1Cr18Ni9Ti stainless steel pipes

Many white spot imperfections were observed on the inner surface of 1Cr18Ni9Ti stainless-steel pipes produced by cold rolling process, so that the products could not be delivered normally. In order to confirm the reasons for the formation of white spots, the surface morphology, metallographic structure, grain size and micro area composition of this batch of steel pipes were analyzed and detected using scanning electron microscopy + energy disperse spectroscopy, metallographic microscope, and laser-induced breakdown spectroscopy. The results showed that the surface carburization occurred on both inner and outer surface of the pipe, and the carburization in white spot imperfection was much more serious than other areas. The severe intergranular corrosion was caused during pickling and passivating. Many grains on the surface were dropped off, deteriorating the roughness on partial surface, and forming white spot imperfections. The inadequate degreasing on pipe surface caused carburization in heat treatment process, which was the major reason for white spot imperfections.