Abstract: The causes of inner folding defects of 0.20% C steel tube are analyzed and studied by means of macroscopic observation, chemical composition analysis and microscopic analysis. The results show that there are a lot of large inclusions around inner folding defects； the inclusions gradually approach the inner wall during rolling tube to form inner folding defects. In production process, with the measures including refining slag surface deoxidization by SiC to replace aluminium shot, refining soft blowing time ≥15 min, casting speed decreasing to 1.9 m/min from original 2. 1 m/min, the rating of B class large inclusions decreases from 3 to 0 to avoid the formation of inner folding defects in piercing process.

摘要： 采用宏观观察、化学分析、微观分析等方法对20钢管内折缺陷产生的原因进行了分析和研究。结果表明,内折缺陷周围存在大量大级别的夹杂物,在穿管过程中夹杂物逐渐靠近内壁而形成内折缺陷。在生产中,通过采用精炼渣面用SiC替代铝粒脱氧、精炼软吹时间保持在≥15 min和连铸拉速由原2.1 m/min降至1.9 m/min等措施,管坯钢中大型B类夹杂物级别由3降至0,避免了穿孔过程中内折缺陷的产生。

关键词: Φ168 mm×5 mm 20钢, 钢管, 内折缺陷, 夹杂物,