Abstract
Zinc alloys used had various copper contetents of 1.0, 1.5, 2.0 and 2.5%. They were melted under vacuum lower than 0.1mm Hg in a furnace of special design and subsequently pressurized by nitrogen up to 2, 6 or 9.5 kg/cm2 at 600°C. The melt was poured into a metal mold of Y-block form throuhg a small tap hole in the bottom of graphite crucible, where the mold was watercooled. As compared with alloy ingots cast under an atmospheric pressure, the ingots cast under high pressures had the following features: there was found no shrinkage hole at the intersection of the Y-block castings; the size of crystal grains grew with increasing the pressure; as a result of tensile strength test it was found that the bottom part of the ingots was stronger than the other part of them; the tensile strength was increased with increasing the pressure up to 6 kg/cm2 but reversely decreased when the pressure was increased up to 9.5 kg/cm2; the efeffect of pressurs was the most distinct in the alloy having copper content in a range between 1.5 and 2.0%; in the case of zinc alloy of 2.0% copper its grain size was finest when casting was made under 6.0 kg/cm2.
