Technological characterization and optimisation of a copper base diecasting alloy

The need to optimise the chemical composition of a diecasting alloy as a function of the technological properties requested by the casting process, led to the development of test apparatus and procedures that allow a comparative assessment of the castability performances in a steel tool and the chemical interaction between the liquid alloy and the die steel. Tests were carried out on a number of copper base alloy, some of which have been modified in order to optimise the technological properties requested by the end product, taking also into account that the alloy is intended to be cast by cold chamber diecasting machine in a hot work steel die. To evaluate the casting behaviour of the alloy in a high thermal conductivity die, a vacuum suction test in a small diameter steel pipe was designed and set up. The measure of the suction length through the pipe due to the pressure difference, allowed a comparison of the fluidity between the tested alloys, at different overheating casting temperatures, and traditional diecasting copper alloy of known performances, taken as the reference alloy. Test results, in terms of suction length and solidified flow front shape, led to the adjustment of chemical composition of a new alloy with better casting performances, overcoming the traditional alloy’s ones. Some static tests were also carried out in order to evaluate the interaction between the liquid alloy and the die steel at high temperature and the effect of alloy iron content and lubricant film on die steel/copper alloy soldering.