THE EFFECT OF CASTING IN A HELIUM ATMOSPHERE ON THE COOLING RATE AND TENSILE PROPERTIES OF RESIN-BONDED SAND CASTINGS

摘要

The work presented here was aimed at examining the effect of replacing air by helium during casting of aluminium alloys in a resin-bonded sand casting process. Helium has a thermal conductivity about 4 to 5 times greater than that of air, and would be expected to increase cooling rates and improve mechanical properties of castings. Plates of different thicknesses (5, 10, 20 and 50 mm) were cast in a Sr-modified A356 alloy, in air and in a >95vol. percent helium atmosphere. Cooling rates were enhanced by the use of helium by 59 percent to 84 percent over the solidification range. The mechanical properties were improved in the as-cast condition by up to 16 percent for the yield stress, by up to 14 percent for the maximum stress, and by up to 5 percent for the maximum strain.