45^(#)钢圆钢心部缺陷分析

Analysis of central defects in 45^(#)steel round bars

针对某尾炉45^(#)钢轧材探伤合格率低的问题,采用带锯床对该批次材料进行锯切加工,在取样过程中带锯发生异常断裂,同时,轧材断口处存在贯穿式的心部缺陷。通过直读光谱分析仪、光学显微镜、布氏硬度计、显微硬度计、扫描电子显微镜及X射线能谱仪等检测手段,对轧材探伤合格率低的原因进行分析。结果表明,圆钢心部存在的贯穿式缩孔缺陷长度为7~10 mm,因缩孔卷渣使氧化渣的硬度超过锯片的强度极限,在锯切过程中导致锯片异常断裂。通过适当调整铸坯尾坯拉速、二冷水强度、适当增加尾炉尾坯切除长度等优化措施,有效提高了铸坯质量,生产效率明显提升。

Under the condition of a low qualification rate of flaw detection for 45^(#)steel rolled products of a tail furnace,a band sawing machine was used for sawing and sampling.During the sampling process,the band saw was abnormally fractured,and visual defects were found at the center of the round steel.In order to scrutinize the reasons for the low qualification rate of rolled materials,the round steel of 45^(#)steel in this batch was inspected using direct reading spectrum analyzer,optical microscope,Brinell hardness tester,microhardness tester,scanning electron microscopeand energy dispersive X-ray spectroscopy,respectively.The results show that the length of the perforated shrinkage hole defect in the core of the round steel is 7-10 mm,and the hardness of the oxidized slag exceeds the strength limit of the saw due to the shrinkage hole rolled slag,causing abnormal fracture of the saw during the sawing process.The quality of casting billet can be improved effectively and the defects of rolling material can be avoided by adjusting the drawing speed of casting billet,the strength of secondary cooling water and increasing the cutting length of tail furnace and tail billet as well.