Abstract: The A572 joints are made with high current MAG welding shielded with helium-free gas in different heat input and the joints exhibit brittle failure in succedent face bend test. The fracture is examined by means of microscope, SEM and EDAX. The results show that the brittle failure is related to C and Ti content, inclusion and martensite in weld metal. In the bent test, the cracks are initiated at the inclusion and then propagate in cleavage fracture for the coarse martensile in the weld. It is concluded that the ductility of the joints can be improved by increasing heat input in welding to help the escaping of inclusion and the decreasing of martensite and C and Ti content.