Microstructure formation of the weld by high nickel ductile iron homogeneous welding electrode

Aimed at the welding difficulties of cast iron that the weld is easy to form the ledeburite and quenched microstructures as well as weld crack during welding. The welding experiment was conducted by using high nickel ductile iron homogeneous welding electrode. The effects of welding technologies on joint microstructure and properties of the homogeneous weld produced by the welding electrode had been researched in detail. The results indicate that the microstructure of the high nickel ductile iron homogeneous weld is composed of fine columnar austenite dendrite, spheroidal graphite and a little intergranular carbide. With the increase of welding current, the morphology of columnar dentrite in the weld tends to be coarsening, the graphite nodularity increases, and the number of intergranular carbides increases. When the welding current is constant, with the increase of preheat temperature, the graphite morphology becomes worse, the amount of carbides precipitated increases, so the tensile strength of the joint decreases and the hardness increases. By using the high nickel ductile iron homogeneous welding electrod, along with the large welding current technology at room temperature, the microstructure and mechanical properties of the weld could be controlled effectively and the high quantity homogeneous weld with excellent machining property can be obtained.