Microstructure and properties of AH36 steel joints by laser-submerged arc hybrid welding

The double-sided welding without groove for 16 mm thick AH36 steel plates was conducted by a laser-submerged arc hybrid welding process. The microstructures and mechanical properties of the laser zone and submerged arc zone of the welded joints were compared and analyzed. The results indicate that the laser zone and submerged arc zone are mainly composed of proeutectoid ferrite, massive ferrite, and fine acicular ferrite. The fusion zone and heat affected zone are mainly composed of a large amount of coarse bainite and a small amount of proeutectoid ferrite and massive ferrite. The microstructures of the laser zone are finer than those of the submerged arc zone. The microhardness of the welded joints presents an M-shaped distribution, and the maximum microhardness in the heat affected zone of the laser zone is about 275 HV. The tensile strengths of the welded joints in the laser zone and submerged arc zone are equivalent, being about 690 MPa, and the fracture locations are both in the base metal. The impact absorbed energies at the weld positions of the laser zone and submerged arc zone are close to 70 J. The impact absorbed energy at the fusion line of the laser zone is 86 J, which is 10.3% higher than that at the fusion line of the submerged arc zone. The impact absorbed energy in the heat affected zone of the laser zone is 78 J, which is 27.9% higher than that in the heat affected zone of the submerged arc zone.