大电流MAG焊接接头弯曲性能研究

采用无氦多元气体保护大电流MAG焊接技术焊接了A5 72接头 ,对接头进行了弯曲性能试验 ,用光学显微镜、扫描电镜和EDAX分析了接头侧弯脆性断口。结果表明 ,弯曲试验时产生的脆断与焊缝金属中有非金属夹杂物、焊缝金属中C、Ti含量较高以及焊缝金属中有马氏体组织等因素密切相关。在弯曲时 ,焊缝金属中存在的非金属夹杂物形成裂源 ,在小线能量焊接时焊道间热影响区组织中存在的大量粗大马氏体组织 ,使焊缝金属在裂纹萌生区和开始扩展阶段为解理断裂。在大电流MAG焊时 ,适当增大线能量以利于非金属夹杂物的逸出并避免马氏体的形成 ,降低焊缝金属中的C、Ti含量 ,从而改善接头韧性。

Bend Performance of High Current MAG Welding Joints

The A572 joints are made with high current MAG welding shielded with helium free gas in different heat input and the joints exhibit brittle failure in succedent face bend test. The fracture is examined by means of microscope, SEM and EDAX. The results show that the brittle failure is related to C and Ti content, inclusion and martensite in weld metal. In the bent test, the cracks are initiated at the inclusion and then propagate in cleavage fracture for the coarse martensile in the weld. It is concluded that the ductility of the joints can be improved by increasing heat input in welding to help the escaping of inclusion and the decreasing of martensite and C and Ti content.