400MPa球墨铸铁光纤激光-MIG电弧复合焊接头的断裂特征

采用填充308L不锈钢焊丝光纤激光-MIG电弧复合焊方法,焊接厚度为5mm的风电关键部件用400 MPa级球墨铸铁,获得了表面成形良好且熔透的焊缝,研究了MIG电弧热输入对接头拉伸性能和断裂特征的影响.结果表明,电弧热输入较小时,接头的拉伸性能差,断裂沿熔合线发生,断口为脆性断口；电弧热输入较大时,接头的拉伸性能较好,断裂自半熔化区顶部沿母材发生,断口顶部为脆性断口,底部为韧性断口.接头断裂特征的差异是由接头中焊缝和半熔化区底部莱氏体的量的不同导致的.基于以上研究,获得了抗拉强度为346.4 MPa、断后伸长率为5.4％,断裂发生在母材上的优质接头.

Fracture characteristic of fiber laser-arc hybrid welded joints of 400 MPa grade ductile cast iron

Laser-MIG arc hybrid welding was used to weld 400 MPa grade ductile cast iron,which is used on key parts of wind power. The thickness of base metal is 5 mm,and 308L stainless steel wire was used as filler wire. The welds with good appearance and full penetration were obtained,and then the influence of welding conditions on tensile properties and fracture characteristic of joints was studied. The results show that the joint at low arc heat input has low tensile properties,fracture expands along the fusion line and it is brittle; the joint at high arc heat input has high tensile properties,fracture expands along base metal,which is brittle on the top of the joint and flexible at the bottom of the joint. The difference of joints fracture characteristic is caused by different quantities of ledebutire at the bottom of fusion zone and partial melting zone (PMZ) of the joints. Based on previous research results,a joint with the tensile strength of 346.4 MPa,the elongation of 5.4% was obtained and its fracture expands along base metal.