弹簧钢SUP9D超声探伤缺陷分析

Analysis on Ultrasonic Inspection Defects of Spring Steel SUP9D

通过对弹簧钢SUP9D超声探伤不合格品进行水浸探伤和金相检测,发现SUP9D钢心部夹杂物位于皮下10.5~12.4 mm,沿纵向长度为18.2~24.9 mm,沿横向长度为200μm左右。对SUP9D钢心部夹杂物进行能谱分析,发现夹杂物成分为Mg、Al、Ca和O,判断夹杂物为Mg、Al、Ca的氧化物。形成原因为中间包内耐火材料溶损物聚集长大为大块氧化物夹杂后未充分上浮和排出,或是在水口附近聚集长大后,随钢液到结晶器后未充分上浮和排出导致。对中间包流场进行优化,增加控流装置,延长夹杂物上浮时间,是减少SUP9D钢内部大型夹杂物,提高SUP9D钢连铸坯内部质量的有效办法。

Through waterlogging ultrasonic inspection and metallography detection for unaccepted the inclusions founded in the core of spring steel SUP9D located in the subsurface 10.5 - 12.4 product, mm, and 18.2 - 24.9 mm long along lengthways and about 200 μm long along crosswise. Through energy dispersion spectrum analysis,the chemical composition of inclusions in the core of SUP9D steel was Mg,Al,Ca,O, so SUP9D steel inclusion was decided as oxide of Mg,Al,Ca. The forming reason of SUP9D steel inclusions was that the refractory dissolution-loss-matter did not fully come up and discharge after agglomerating to block inclusions or the refractory dissolution-loss-matter flowed into crystallizer with liquid steel and did not fully come up and discharge after agglomerating to block inclusions nearby ladle slide gate. Optimizing the tundish low field, increasing the control flow device and extending the ascent time of inclusions were the effective method of reducing internal block SUP9D steel inclusions and improving interior quality of SUP9D steel of the continuous cast bloom.