Brazing behaviour of some 18K jewellery gold alloys with different melting points

One of the concerns in manufacturing jewellery is the optimisation of gold alloys with regard to their brazability. In jewellery the maintaining of mechanical and metallurgical properties and of the carats of the manufactured jewel after brazing and after re-heating operations has to be considered. These problems were investigated studying the behaviour of three kinds of alloys having 18 K and different melting points. We focused on a new filler metal (i.e. Au-Ag-Zn-Cu) joining two commercial coloured gold based alloys (i.e. Au-Cu-Ag and Au-Cu-Ag-Pd). Several joints, performed in two different geometrical conditions (i.e. butt and superimposed joints), were produced using an air-propane flame as brazing source.