Bonding characteristics of spheroidal graphite cast iron and mild steel using electron beam welding process

The electron beam welding is applied for welding of mild steel to spheroidal graphite (SG) cast iron, and its weldability are investigated from the viewpoint of microstructure and mechanical properties. When the electron beam was radiated to a SG cast iron specimen, remelting of the surface and corresponding rapid cooling took place, and it resulted in formation of brittle fine-cementite structure whose hardness is over H-v = 700. As Ni is an alloying element that may prevent formation of cementite, we tried two kinds of welding methods with Ni addition and compared their results: one method is inserting a thin plate made of SG cast iron with a high Ni content between two base materials and then radiating electron beam to the plate, and other one is a metal active gas welding process using a Fe Ni wire. The bonding tensile strength of the former was some 400 MPa, which was larger than some 350 MPa of that of the latter. (C) 2004 Elsevier Ltd. All rights reserved.