45#圆管坯棒材穿管裂纹成因及控制措施

Analysis of Causes and Control Measures for Cracks in 45# Round Billets During Pipe Threading

某钢管有限公司利用45#圆管坯棒材生产规格为Φ114 mm×4.5 mm的穿管产品,成品车削深度0.2~0.4 mm后,发现存在严重的表面发纹。对缺陷部位取样,通过宏观形貌观察、化学成分、金相分析以及扫描电镜微区分析,以及未加工成品取样塔形分析,认为裂纹缺陷是由于产品局部存在大颗粒夹杂物,经磨削后夹杂物暴露于表面所致。采取提高保护渣性能、将浸入式水口插入深度由100~140 mm调整为110~130 mm等措施,基本消除裂纹缺陷。

A 45# Steel bar for the production of a specification ofΦ114 mm×4.5 mm produced by a steel pipe limited company has surface cracking defects after turning,The turning depths are 0.2 mm and 0.4 mm respectively.After sampling at the defective site,macroscopic morphology observation,chemical composition,metallographic analysis,scanning electron microscopy analysis,and tower type analysis of steel bar,it was found that the surface crack is caused by the local presence of large inclusions in the furnace product,which were exposed to the surface after grinding.Some measures such as improving the performance of protective slag and adjusting the insertion depth of submerged nozzle from 100-140 mm to 110-130 mm are adopted to basically eliminate the crack defects.