Microstructure and mechanical properties of the arc welded joint of 400 MPa grade ultrafine grained steel

Some conventional arc welding experiments, such as manual arc welding, carbon dioxide welding and submerged arc welding, were carried out on 400 MPa grade ultrafine grained steel. The microstructure and mechanical properties of the 400 MPa ultrafine grained steel in welded joint were tested and analyzed. The results show that the grain size grows up obviously in the heat affected zone (HAZ) of all the arc welded joints, the mechanical properties of the arc welded joints by manual arc welding and submerged arc welding decrease greatly, but these of the welded joints by carbon dioxide welding decrease slightly. Based on the test results, the carbon dioxide welding can be used to weld 400 MPa grade ultrafine grained steel directly in manufacture.