12Cr1MoVG 钢管表面折叠形成原因分析及改进

Cause analysis and improvement of surface folding of 12Cr1MoVG steel pipe

12Cr1MoVG热轧圆钢制造的钢管表面出现折叠缺陷。利用金相显微镜、扫描电镜等手段通过对钢管表面缺陷形成的原因进行分析,发现折叠缝隙内存在灰色氧化物,在折叠缝隙附近存在高温氧化质点,折叠缝隙边缘组织存在明显脱碳,并追溯热轧圆钢表面质量及铸坯表面质量。结果表明,钢管表面存在的折叠状缺陷是热轧圆钢表面裂纹缺陷经穿管所致,而热轧圆钢表面的裂纹缺陷是由连铸坯表面横裂纹缺陷导致的,通过优化结晶器水温差和结晶器保护渣参数指标,基本消除了铸坯表面的横裂纹缺陷。

Folding defects occured on surface of steel pipe made of 12 Cr1 MoVG hot rolled round steel. The causes of surface defects were analyzed by means of metallographic microscope and SEM. It is found that there are gray oxides in folding gap, high-temperature oxidation particles near folding gap, and obvious decarburization in edge structure of folding gap. The surface quality of hot-rolled round steel and slab are traced.Results show that folded defects on steel pipe surface are caused by surface crack defects of hot-rolled round steel, and surface crack defects of hot-rolled round steel are caused by transverse crack defects on continuous casting billet surface. The transverse crack defects on billet surface are basically eliminated by optimizing water temperature difference of mold and parameters of mold flux.