基于优化的SUS301L-HT不锈钢激光-MAG复合焊接工艺施焊,获得了质量等级优异的接头。采用光学显微镜对接头组织进分析,分析结果表明:焊缝的软化最为严重,其组织为奥氏体柱状晶和铁素体;热影响区发生不同程度的回复和再结晶,其硬度高于焊缝。针对接头强度薄弱的焊缝区进行裂纹扩展测试,研究不同阶段的裂纹扩展特性及断口特征,讨论焊缝组织对裂纹扩展过程的影响,结果表明:铁素体是疲劳裂纹的起源位置,并成为裂纹的优先扩展通道。对工艺进行进一步优化可以改善焊缝的裂纹扩展抗力。

Herein,a joint with quality of excellent grade was obtained based on an optimal laser-metal active gas arc welding (MAG) hybrid-welding process for SUS301L-HT stainless steel. The microstructure characteristics of the welded joint were analyzed through optical microscopy. The analysis showed that the weld exhibited the most serious softening, and its microstructure comprised columnar austenite grains and ferrite. The heat affected zone (HAZ) exhibited different degrees of recovery and recrystallization, and its hardness was higher than that in the weld. The crack growth testing was conducted in the weak area of joint strength (weld) to study the crack propagation characteristics and fracture feature at different stages and to discuss the impact of the weld microstructure on the crack growth process. Results indicated that ferrite was usually the initiation site of fatigue cracks and the preferred crack propagation channel. Resistance to crack propagation in the fusion zone can be improved through further process optimization.