Q440C级门架型钢大方坯横裂纹原因分析与改进

The Cause Analysis and Improvement Measures of the Transverse Crack in the Section Steel of Q440C Door Frame

针对莱钢开发的Q440C级C250b门架型钢铸坯内弧边存在横裂纹的问题,结合生产实际情况,通过严格控制钢水中的P、S含量、采用非正弦高频小幅振动技术、比水量采用0.25 L/kg的超弱冷方式以及采用Q440C级C250b门架型钢专用保护渣等控制措施,使莱钢Q440C级C250b门架型钢260 mm×300 mm断面大方坯铸坯废品率由7.3%降低到0.5%。

For the grade Q440C steel of the C250b crane span structure developed by Laiwu branch, there is a transverse crack in the inner arc edge of the casting blank. Combining the actual production of Laigang, the content of P and S in the molten steel was strictly controlled, a non-sine, high-frequency and small vibration technique was used. The ultra-weak cooling method of 0.25 L/kg water ratio and the control measures such as protective slags specially used for the door frame section of Q440C grade C250b are adopted. The unqualified rate of the 260 x 300 mm section of Laigang Q440C grade C250b door frame was reduced from 7.3% to 0.5%.