Shinichi Sekiguchi

Mechanical properties of spheroidal graphite cast iron and stainless steel welded joints by electron beam welding

Studies have been conducted on the structures and mechanical properties of spheroidal graphite cast iron (FCD400 and 600) and stainless steel (SUS304) welded joints, developed by direct welding and pure Ni insert-type electron beam welding (hereinafter referred to as “pure Ni welding”). Regarding results, the melting and solidifying areas showed a structure of dendrites or cell-dendrites for direct welding and for pure Ni welding. Both microstructures were austenitic. The average hardness at the melting and solidifying areas was 399 HV for direct welding and 233 HV for pure Ni welding, which were significantly low values. In the tensile test of the welded joints, the joint efficiency for direct welding was 72%, which was significantly low. In contrast, the joint efficiency for pure Ni welding was 93%, showing excellent joint performance. In the impact test of the welded joints, the impact value for pure Ni welding showed an increased trend along with an increase of the testing temperature. In addition, in the fatigue test of the welded joints, the fatigue strength for direct welding and pure Ni welding increased more than that of the FCD400 base material. The fatigue limits were 255 MPa and 260 MPa, respectively.