Study of the Effect of Quenchants on the Machinability of Heat Treated Mild-Steel

Abstract

Heat treated steels that are quenched rapidly show an increase in hardness and toughness but also show an increase in brittleness which could lead to a higher surface roughness and low material removal rate while machining. Hence, the choice of quenchants has a significant effect on the hardness of low carbon steels. In this research work, the effect of some selected quenchants on the mechanical properties of heat treated and machined mild steel was investigated. Four samples of the carbon steel rods were furnace heated at 8500C and quenched with water, molten salt, potash alum and used engine oil. Central Composite Designs of Design Expert version 12 was used to plan the experiment. Machining factors used were, speed (100-450 rpm), feed rate (0.01-0.03 mm/rev), depth of cut (1-2mm). Surface roughness and material removal rate as well as the results of quenchant characterization were the responses studied. The favored quenchant was oil with the lowest surface roughness, hardness and material removal rate of 0.33μm and 187.78BHN and 0.020133mm3/min respectively. This is because the use of oil resulted in the highest reduction in surface roughness and enhanced material removal rate.