4130X连铸开浇炉钢管探伤不合格原因分析

分析了4130X气瓶钢管探伤不合格的原因为开浇炉二次氧化引起非金属夹杂物。以?500 mm规格连铸圆坯4130X为研究对象，从距勾头不同位置取样，研究氧含量、氮含量、Al损耗、非金属夹杂物等指标的变化规律，发现距离勾头部位越近，氧含量、氮含量越高，Al损耗越大，非金属夹杂物中B类、D类、DS类级别越高，说明开浇阶段钢液二次氧化程度相当严重。另外，研究发现，距离勾头越近，长度5μm及以上的含Al非金属夹杂物分布密度越大，说明开浇时钢液的二次氧化对5μm以上的夹杂物影响较大。

Cause analysis of flaw detection unqualified of 4130X continuous casting open cast furnace steel pipe

It pointed out that the reason for flaw detection unqualified of 4130X steel pipe was the nonmetallic inclusions caused by secondary oxidation of open cast furnace. Take ø500 mm continuous casting blank as the object, several samples were taken from different positions of the casting blank. It was found that the oxygen content, nitrogen content, Al loss and nonmetallic inclusions in the steel in the open casting part were higher than those in other parts, which implied that the secondary oxidation in the open casting part was more serious. In addition, the nearlier to open casting part the quantity and distribution density of inclusions with length more than 5 μm. It is indicated that the effect of secondary oxidation on inclusions more then 5 μm is obviously when open casting.