焊管压扁开裂的原因分析

Cause analysis of flattening fracture of welded pipes

某厂家的焊管在压扁试验过程中开裂,为找出焊管开裂的原因,在实验室对未开裂焊管进行了压扁验证试验,观察了开裂管的宏观形貌。并采用微观断口观察、金相分析及金属流线上升角测定等测试分析手段进行综合分析。结果表明,焊管开裂的主要原因是由于焊管中存在的硫化物夹杂破坏了焊管金属的连续性,在焊接过程中,焊缝处于较大挤压力下,使得金属流线上升角过大且露头,从而引起开裂,裂纹沿着管材的中心偏析位置向内扩展。

The welded pipes from one factory were cracked during the flattening test. In order to find out the cause of fracture, the flattening verification tests of non-cracked welded pipes were conducted in laboratory. The macroscopic morphology of cracked pipes was observed. The fractures were comprehensively analyzed by metallographic examina- tion and the measurement of rise angle of metal flow line. The results showed that the main reason to cause fracture was the sulfide inclusions in welded pipe, which destroyed the continuity of metal. During the process of welding, the weld seam was under large extrusion stress, leading to too high rise angle of metal flow line and fracture of welded pipes. The cracks further extended inward along the center segregation.