摘要
本文考察了一侧经手弧焊,另一侧经埋弧自动焊焊接接头的显微组织,并用扫描电镜对断口进行了分析。在此基础上,研究了接头的冷弯开裂及断裂行为。结果表明:只有埋弧焊一侧产生冷弯开裂或断裂现象。冷弯初期,在过热区出现裂纹,但在随后的弯曲过程中无明显扩展,这是由于裂纹周围的显微组织具有较大的抗裂纹扩展阻力。冷弯后期,焊缝产生裂纹并迅速扩展而断裂,这主要是由于条虫状气孔的存在所致,而显微气孔及少量的球状显微夹杂对断裂仅起着促进作用。
Based on the investigation of mierostructure of the welded joints and the fracture surfaces with SEM, the cracking and fracture behavior of the 20g steel joints welded with SMAW on one side and then with ASAW on the another side were studied. The results show that the cracking and fracture only occured in the ASAW side of the joints. The crack emerged in the overheated zones during the initial stage of bend tes t, but extended extremly slowly due to great resistance to the crack extending in the microstructure surrounding the crack tip. During the later stage, another crack emerged in the weld, extended rapidly and led to fracture, which mainly resulted from the presence of wormholes. In addition, the micro-blowholes and micro-inclusions had the effect to promote the process of the fracture.
关键词
焊接
接头
冷弯
开裂
断裂
Welded joints
Bend test
Cracking
Fracture.
