低融点銀ろうによる超硬合金のろう付

抄録

The present study was aimed at producing new Ag-based filler metals that have a melting point lower than that of a conventional Ag-based filler metal (BAg-24) for brazing cemented carbide and possess the ability to provide a high strength joint of cemented carbide. Using an Ag-based filler metal with a lower melting point (BAg0) that was a quaternary alloy of Ag-Cu-Zn-Sn system previously developed by authors, and Ag-based filler metals with Ni or Co element added into the BAg0, cemented carbide rods were brazed. Bending strength of the joint and the brazed layer microstructure were investigated. The following results were obtained in this study.
Bending strength of a joint brazed at 650°C using the BAg0 was about 85% that of a joint brazed at 750°C using the BAg-24. When Ni element was added into the BAg0, intermetallic compounds were formed in the brazed layer, and bending strength of a brazed joint was decreased. By adding a small amount of Co element into the BAg0, bending strength of a joint brazed at 650°C was improved and was equivalent to that of a joint brazed at 750°C using the BAg-24. However, excessive addition of the Co element made the bending strength of a joint decreased.