20Cr钢曲轴锻件翘皮成因分析和工艺改进

20Cr钢的生产流程为120 t BOF-LF-200 mm×200 mm坯CC-轧制。对Φ35 mm 20Cr圆钢锻造的小型机械曲轴的结疤翘皮进行了成分检测、金相分析和电镜扫描能谱分析。结果表明,连铸过程结晶器液面波动超过±5 mm,造成保护渣卷入弯月面,引起铸坯表面夹渣和增碳,轧制过程形成结疤翘皮缺陷。通过浸入式水口深度由80～120 mm增加至90～130 mm,强化中间包水口和塞棒管控以及优化保护渣操作与性能使熔渣层厚度为10～15 mm,保证结晶器液面波动稳定在±3 mm内,避免了铸坯卷渣和锻件翘皮。

Analysis on Cause of Upwarping of 20 Cr Steel Crankshaft Forgings and Process Improvement

The production flowsheet of 20 Cr steel is 120 t BOF-LF-200 mm x200 mm bloom CC-rolling. The composition detection, metallographic analysis and SEM energy dispersive analysis on the scarring and warping of forged small mechenical crankshaft of Φ35mm 20Cr round steel are carried out. The results show that during the continuous casting process,the mold liquid level fluctuation exceeded ±5 mm,led to mold powder to enter the meniscus,causing slag inclusion and carburization on the surface of the bloom, finally forming scarring and warping defects during rolling. By increasing the depth of the submerged nozzle form 80 ~ 120 mm to 90 - 130 mm, strengthening the control of the tundish nozzle and stop¬per, and optimizing the operation and performance of mold powder, the liquid level fluctuation in mold is stable within ± 3 mm,to avoid entrapped slag and forgings warping.