Welding consumable research for austempered ductile iron (ADI)

The microstructure of austempered ductile iron (ADI) weld metal mainly consists of bainitic ferrite, retained austenite and graphite nodules in this investigation. Cu, Ni, Mn and Mo all have favorable effect on austemperability of the weld, and the most pronounced increase in the austemperability is brought about by Mo. Cu and Ni have little effect on the tensile strength, but they can improve the ductility of ADI weld due to increased retained austenite volume fraction. Increasing weld Mn or Mo content results in impairing the ductility of ADI weld, which is mainly attributed to the formation of martensite or carbide enriched with Mo in eutectic cell boundary region. The weld alloyed with 0.54% Cu, 0.71% Ni, 0.32% Mn and 0.19% Mo has not only high austemperability but also exceptional combination of the mechanical properties, the critical bar diameter (Dc), tensile strength and elongation being 42 mm, 1142 MPa and 9.5%, respectively. They can match those of low-alloy ADI.