Research On Welding Procedures And Properties Of Dissimilar Metal Welded Joint

The study of dissimilar welded joints prepared by shielded metal arc welding process using electrode A312 is conducted in detail. The welding of 12mm thick 16MnR steel and the 10 mm thick lCrl8Ni9 steel is made. The study on the mechanical properties of dissimilar joint are carried out, and the as-welded and the post-weld heat-treated joint corrosion tests have been performed under the conditions of the different corrosion concentration and the different corrosion duration which simulates the practical environments the welding construction operates. The research on the corrosion resistance property of dissimilar welded joint metals in the different zone is conducted by means of SEM, EDS and X-RD analytical technique.The test results show that the tensile strength and the impact work of the dissimilar joints at ambient temperature are higher than those of 16MnR base metal, the microhardness peak value is got in fusion zone adjacent to base metal 16MnR. When the welded joints are held 2 hours under 650℃, 750℃and 850℃, respectively, the corrosion resistance of dissimilar joint becomes better with the increase of heat treatment temperature. There is a maximum average corrosion rate for the joint treated under 650℃, holding 2 hours, the hardness value fluctuates greatly, therefore, the worst corrosion resistance of the dissimilar welded joint is got. When the post-weld heat-treated joints are held 30mins, 60mins, 90mins, 120mins respectively at 650℃, the average corrosion rate increases with the increase of holding duration. The corrosion tests of dissimilar welded joints are conducted in NaOH corrosion liquid with the concentration 10% , 30% , 50% and 70%. The corrosion resistance property of as-welded joint decreases rapidly in concentration 50% corrosion liquid, but for post-weld heat treated joints holding 2 hours under 650℃, the corrosion resistance property of dissimilar joint begins to decrease after the concentration up to 30%. With the increase of corrosion test duration, the average corrosion rate of both as-welded and post-weld heat-treated joints increases, but the average corrosion rate of post-weld heat-treated joints increases more obviously, and the microhardnessvalue changed greatly.