热镀锌钢管滚槽开裂原因分析

Analysis of Cracks Caused by Rolling Groove of Hot Dip Galvanized Steel Pipe

某企业生产的热镀锌焊接钢管在滚槽加工过程中出现开裂问题。对开裂样品进行化学成分、断口形貌、显微组织、焊缝熔合线夹杂物、焊缝金属流线、焊缝熔合线宽度检测分析。结果表明,由于化学成分及焊接工艺问题导致焊缝区域存在魏氏组织、焊缝两侧组织不同、未焊合、熔合线粗大、熔合线夹杂物聚集、熔合线流线角不合理等缺欠,在焊接、酸洗及烘干过程引入的氢在这些缺陷处聚集,最终在焊接残余应力和压槽时剪切拉应力的综合作用下,导致管氢延迟性开裂。

The hot-dip galvanized welded steel pipe produced by a company has cracking problems during the rolling groove processing. The cracked samples are tested for chemical composition, fracture morphology, microstructure, inclusion of weld fusion line, weld metal flow lines and weld fusion line width. The result shows that due to chemical composition and welding process problems, there are defects in the weld area, such as widmanstatten structure, different microstructures on both sides of the weld, unwelded defect, thick fusion lines, inclusion accumulation in fusion line and unreasonable weld streamline angle. The hydrogen introduced during the welding,pickling and drying process accumulates at these defects. Finally, under the combined action of the welding residual stress and the shear tensile stress at the rolling groove, the hydrogen causes delayed cracking of the pipe.