20Cr方坯表面缺陷分析与工艺优化  

SURFACE DEFECTS ANALYSIS AND PROCESS OPTIMIZATION OF CASTING BILLET OF 20Cr STEEL

作　　者：陈事 印传磊 刘从德[1] 朱平 蒋栋初 Chen Shi;Yin Chuanlei;Liu Congde;Zhu Ping;Jiang Dongchu(Steelmaking Plant of Jiangsu Shagang Group Huaigang Special Steel Co.,Ltd.,huaian 223002,Jiangsu)

机构地区：[1]江苏沙钢集团淮钢特钢股份有限公司炼钢厂,江苏淮安223002

出　　处：《河北冶金》2024年第8期65-69,共5页Hebei Metallurgy

摘　　要：20Cr是一种亚包晶低碳合金钢,铸坯酸洗时发现角部存在横向裂纹缺陷,采取抛丸、磁粉探伤和扫描电镜等方式对铸坯横向角裂缺陷进行了分析,发现缺陷位置存在明显的脱碳现象,判断裂纹在结晶器高温区域产生。根据检测结果,围绕结晶器区域,对工艺方案进行了优化。试验结果表明:结晶器冷却水流量偏大、冷却偏强,水流速达到了13.7 m/s,保护渣熔点和粘度低使得液渣流入气隙时存在不均匀现象,另外铸坯角部存在深振痕,这是导致20Cr铸坯存在角部横裂纹的主要原因;经过理论计算,将结晶器冷却水流量从150 m^(3)/h降低至120 m^(3)/h,减缓结晶器内的传热速度;将保护渣熔点从1030℃提高至1180℃、粘度从0.53 Pa·s提高至0.95 Pa·s,使液态保护渣能够更均匀地流入钢坯与铜管之间的缝隙;将振幅从±5 mm下调至±3 mm、振频从155 cpm上调至190 cpm,铸坯的振痕深度大大减轻,铸坯酸洗100块以上均未发现裂纹缺陷,铸坯抛丸、磁粉探伤合格率从75%提高至99%以上。20Cr is a subperitectic low-carbon alloy steel.Transverse cracks were observed in the corners of the cast billet during pickling.The analysis of the transverse cracks in the cast billet was conducted using shot blasting,magnetic particle testing,and scanning electron microscopy.Based on the test results,the process plan was optimized around the mold area.The findings indicate that excessive flow rate of mold cooling water led to strong cooling with a water flow speed reaching 13.7 m/s.Uneven flow of liquid slag into air gaps was attributed to its low melting point and viscosity of protective powder.Additionally,deep vibration marks at the corner of casting billet were identified as the primary cause for transverse corner cracks in 20Cr casting billet.Theoretical calculations suggested reducing mould cooling water flow from 150 m^(3)/h to 120 m^(3)/h to slow down heat transfer rate and increasing slag melting point from 1030℃to 1180℃along with viscosity from 0.53 Pa·s to 0.95 Pa·s for more even distribution between billet and copper tube gap.Furthermore,by reducing amplitude from±5 mm to±3 mm and increasing vibration frequency from 155 cpm to 190 cpm,significant reduction in billet vibration depth resulted in absence of cracks in over 100 pickled billets.It consequently raises pass rate for shot blasting and magnetic particle detection from 75%to over 99%.

关 键 词：20Cr 横裂纹 结晶器 冷却水 保护渣 振痕 

分 类 号：TF764.2[冶金工程—钢铁冶金]