1999 Volume 85 Issue 7 Pages 531-537
The warm bonding process for 21Ni-6Cr-Fe/36Ni-Fe bimetal has been studied and we have confirmed that bond strength was improved drastically. Furthermore, the cause of improved bond strength has been pursued and the effect of warm bonding has been examined. The bond strength of warm bonded bimetal at 200°C was about doubled than that of cold bonded bimetal at room temperature. As a result of observation of the bonded surface separated from the bonded part, as for the warm bonded bimetal, tight bond traces were magnified 2.5 times than those of the cold bonded bimetal. Adsorption water on the surface of the material is released by heating before bonding, so oxygen which remained on the bonded part declined sharply. A calculated result of the relationship between bonding reduction and bond contribution area agreed with very well a tendency of measured results of the relationship between bonding reduction and bond strength. Therefore, the reason why the bond strength of warm bonding is higher, can be explained by the expansion of the bond contribution area. The bonding reduction can decrease in warm bonding, because the bond strength of the warm bonding at 200°C at 50% reduction is equal to the bond strength of the cold bonding at room temperature at 65% reduction. The range of manufacturing will be expanded in the case of warm bonding because a bonding load was reduced 30%.
