The effects of different casting techniques on the hardness, energy absorbance and impact strength of sand-cast Pb-Sb-Cu alloys

Abstract

The effect of casting technique on the impact strength, energy absorbance and hardness of sand cast Pb-Sb-Cu alloys was studied following casting of the alloys using three techniques. Cooling of the alloys after casting was carried out in water, air and furnace in order to vary the micro-structure of the alloys produced. Copper addition to the base alloy was by dispersion of the Cu powder within the Pb-Sb matrix using the three casting techniques. The results showed that Technique A, which involved simultaneous addition of Cu powder and pouring of the molten Pb-Sb into the mould conferred higher impact strength and better energy absorbance on the Pb-Sb-Cu alloys produced, compared to alloys from Techniques B (involving addition of Cu powder intermittently as pouring of Pb-Sb into the mould was going on) and C (involving pouring a stirred mixture of heated Pb-Sb alloy and powdered Cu into the mould). Hardness of the Pb-Sb-Cu alloys was independent of the casting techniques used, but highly dependent on the cooling rate imposed by the cooling medium. Irrespective of the casting technique used, cooling the Pb-Sb-Cu alloys in water conferred higher hardness on the alloys, while higher impact strength and energy absorbance were conferred on the alloys following furnace cooling. Increased Cu addition (up to a maximum of 8.26%) to the Pb-Sb alloy increased correspondingly the impact strength, energy absorbance and hardness of Pb-Sb-Cu alloys so produced.

Keywords: Casting technique, sand casting, Pb-Sb-Cu alloy, copper powder

International Journal of Natural and Applied Sciences, 5(3): 195-202, 2009