Cast-Bonding of Flake Graphite Cast Iron and Stainless Steel Using Evaporative Pattern Casting Process

Flake graphite cast iron and stainless steel were bonded using evaporative pattern casting process with various gating system and pouring conditions. Microstructure, hardness, shear strength and fatigue limit near the bonding interface were examined. Results obtained were summarized as follows : (1) In cast-bonding of flake graphite cast iron FC 250 and stainless steel SUS420J2, gas deffects at the bonding interface were able to be avoided by adequate gating system, insulating sleeve and gas evacuation. (2) State of bonding and microstructures at the interface were influenced markedly by pouring temperature. With pouring temperature of 1723 K, the bonding was mainly mechanical, but with 1823 K, diffusion bonding was obtained. (3) Carbides and double carbides were observed near the bonding interface of the cast-bonding. The hardness of the bonding region increased 3 to 4 times to the level of the base metal. (4) In shearing and tearing tests, strength of the bonding region was improved 2 to 4 times to that in base metal. (5) The bending fatigue limit of the bonding region was approached to that of SUS420J2. Then, it was improved 1.5 to 1.7 times to the level of the base metal.