Machinability of Copper-Zinc Alloy Castings

Abstract

The casting specimens are made of copper-zinc alloy (i.e. brass). Of the latter there are seven sorts according to zinc ingredient ratio in the range of 10∼40%. Turning and drilling tests have been experimented. Research has been conducted of the correlation between the chemical composition or the microscopic structure and the machinability in the viewpoint of the cutting resistance, the unit net horsepower, the surface roughness, and the torque or the drilling time under constant load drilling among others. The results are as follows;
With the α-phase alloy with zinc ingredient in the range of 10∼30%, the cutting resistance and the unit net horsepower decrease with the rise of zinc content, but, when the alloy changes from α-single phase to (α+β)-phase with zinc content in the range of 30∼40%, the cutting resistance and the unit net horsepower increase, and this inclination is especially distinct in the case of the small side rake angle.
In this experiment, the surface roughness is generally well, and there is not so much difference by the alloyed zinc content. To be precise, however, the rough surface gets improved with the rise of the zinc content and increase in side rake angle.
In drilling under constant load, the torque corresponding to the zinc content is not so changeable and the inclination is not so distinct, but, the drilling time changes clearly according to zinc content in α-single phase and increases again if the alloy becomes in (α+β)-phase with increase of zinc content.