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.