TENSILE STRENGTH COMPARISON OF FOUNDRY SAND CORES BONDED WITH DIFFERENT GRADES OF NIGERIAN GUM ARABIC EXUDATES

Abstract

The empirical tensile strength values of baked sand cores bonded with each of the four commercial grades of exudates of Nigerian gum Arabic (acacia species) were experimentally measured using established standard procedures in foundry industry. The experimental test specimens which were shaped like the number 8 were made from silica sand bonded with different grades of gum Arabic exudates. The specimens were classified, oven baked at 1600C, 2000C, 2200C and 2500C for periods of 1-3 hours, oven cooled and then subjected to strength tests using a standard universal strength machine in foundry shop of Ajaokuta Steel Company Limited, Nigeria. The research result showed that expendable foundry sand cores bonded with Nigerian gum Arabic baked at 1600C for 1-3 hours didn’t reach optimum strength. Grades 1 and 2 acacia bonded cores gave peak tensile strength when baked at 2000C. Those bonded with grades 3 and 4 gum Arabic gave optimum tensile strength when baked at 2200C. At 2500C, cores were observed to burn and loose strength. For process economics gum Arabic grade 4 is best for foundry core application as it was cheapest in price and cores bonded with it attained required tensile strength at least baking temperature within the ...