Q195焊接钢管压槽过程焊缝开裂特征及成因

Characteristics and Causes of Weld Cracking in Groove Pressuring Process of Q195 Welded Steel Pipe

采用OM、SEM、EDS等检测手段,研究了Q195高频直缝电阻焊(ERW)钢管在压槽过程中焊缝开裂的特征及其成因。结果表明:在焊管焊缝开裂处有氧化夹杂物,焊缝开裂处母材的孔洞、夹杂物与正常试样焊缝处的基本一样,但是有裂纹焊缝处的热影响区不对称、金属流线不明显,而正常试样焊缝处热影响区对称、金属流线明显。因此引起Q195镀锌ERW钢管压槽过程中开裂的原因是高频直缝电阻焊挤压力偏小,造成金属流线不明显,在这种情况下焊缝中较多的氧化夹杂物或'灰斑'不易排出,成为焊缝开裂的裂纹源,导致镀锌焊管在压槽过程中焊缝开裂。

The characteristics and causes of weld cracking in groove pressuring process of Q195 ERW steel pipe were studied by means of OM、SEM and EDS.The results show that there are oxide inclusions in the weld cracks of the welded pipe,and the holes,inclusions of base metal at the cracks of the weld seam are basically the same as those of welds of the normal sample.However,the heat affected zone morphology in the cracked welds is asymmetric,and the metal flow lines are not obvious,while the heat affected zone morphology in the weld of normal sample is symmetry and the metal flow lines are obvious.Therefore the reason for the cracking of Q195 galvanized ERW steel pipe is that the ERW extrusion pressure is small and metal streamline is not obvious.In this case,more oxidation inclusions or'gray spots'in the weld are not easy to be eliminated and become the crack source of cracking of weld,which leads to the crack of galvanized welded pipe in the process of groove pressuring.