Microstructure and corrosion resistance of butt joint of 1Cr18Ni9Ti+Q235 composite plate

Four different automatic welding techniques were applied for butt welding of the composite pipe that has a clad layer of 1Cr18Ni9Ti with a thickness of 3 mm and a substrate layer of Q235 with a thickness of 10 mm. The properties of the joint,including microstructure,tensile strength,bend strength,impact toughness,electrochemical and intergranular corrosion resistance,were evaluated. The results indicate that the phase of the clad layer welded by tungsten inert gas welding (TIG) is austenite with a little ferrite. The electrochemical corrosion resistance of the joint is similar to that of the base metal in hydrochloric acid of 1 mol/L and no intergranular corrosion is observed. The phase of the TIG welded joint of the substrate layer is martensite laths that have high strength and excellent toughness. But both the joints of the substrate layer and the clad layer welded by submerged arc welding have poorer mechanical properties and corrosion resistance,respectively.