The bonding of an S45C steel insert to copper during cast welding and continuous cooling treatment ( including: furnace cooling; air cooling; oil quenching and water quenching) was investigated. The interface shear strength was determined using a push-out test. A cast welding layer formed between S45C steel and copper. After continuous cooling heat treatment, a cast welding layer was present near the S45C steel, an irregular layer near the copper matrix, and a middle layer between these two. X-ray diffraction analysis was used to determine that the interface layer consisted of carbon and CuFeO2. Electron probe microanalysis (EPMA) demonstrated that most iron atoms and carbons diffused into the copper matrix. The interface shear strength of the compound casting under furnace-cooling was the largest and that of the compound casting formed by water-quenching was the smallest, and all fractures in the cast welding layer occurred near the S45C steel matrix. (C) 2004 Kluwer Academic Publishers.