连铸保护渣特性对X55SiCrA弹簧钢铸坯角部裂纹和盘条质量的影响

Effect of continuous casting mold slag characteristics on billet corner cracks and wire rod quality of X55SiCrA spring steel

为了改善X55SiCrA弹簧钢铸坯角部裂纹和轧制盘条质量,对盘条以及铸坯裂纹进行分析,且对连铸保护渣的成分进行优化。结果表明,轧制盘条裂纹以及铸坯角部纵裂纹两侧发生脱碳行为,铸坯角部纵裂纹附近存在高温氧化物圆点,在铸坯角部纵裂纹内部发现了保护渣成分。当保护渣碱度从0.62增加至1.02,Na_(2)O质量分数从6%左右增加至约12%,F-质量分数从3%左右增加至7%~8%时,保护渣由酸性渣转变为碱性渣,在保证保护渣润滑能力的同时,提高了保护渣的结晶性能和控制传热能力。采用优化保护渣浇铸X55SiCrA弹簧钢时,铸坯角部纵裂纹消除。使用原保护渣和优化保护渣铸坯轧制盘条质量相比发现,优化保护渣浇铸的铸坯轧制盘条判废率从40%以下降至5%以下,大幅度提高了轧制盘条的成材率和产品质量。

In order to improve the billet corner cracks and rolling wire rod quality of X55SiCrA spring steel,the wire rod and billet cracks were analyzed,and the composition of continuous casting mold slag was optimized.The results showed that decarburization behavior occur on both sides of the rolling wire rod crack and the longitudinal crack at the corner of the casting billet.There are high-temperature oxide dots near the longitudinal crack at the corner of the casting billet,and slag composition is found inside the longitudinal crack at the corner of the casting billet.When the slag alkalinity increases from 0.62 to 1.02,the Na_(2)O content increases from about 6%to 12%,and the F-content increases from about 3%to 7%-8%,the slag type transforms from acidic slag to alkaline slag,which ensures the slag lubrication ability,improves its crystallization performance and ability to control heat transfer.When using the optimized slag to cast X55SiCrA spring steel,the longitudinal cracks at billet corners are eliminated.Compared with the rolling wire rod quality when using the original slag and the optimization slag to cast billet,the rejection rate of using optimized slag to cast billet has decreased from over 40%to less than 5%,which greatly improves the yield and theproductqualityof rollingwire rod.