Effects of Bath Temperature on Cooling Rate, Mechanical Properties and Microstructure of Medium Carbon Steel during Quenching Operations

Abstract

The effects of variations of bath temperatures of Selected Nigerian Vegetable oils on cooling rates, mechanical properties and microstructure of the quenched steel samples were investigated in this work. Cooling curves at different bath temperatures have been experimentally determined. From the cooling curves, the cooling ability variations were then analysed. The results obtained show that increasing bath temperatures increased the cooling rates of the quenched steel. These cooling rates are found to enhance mechanical strength with limited ductility of the quenched carbon steel. The hardness and tensile strength for palm kernel quenched sample increased from 40.8 HRC to 43 HRC. However, percentage elongation and impact values decreased from 0.28% to 0.21% and 9.5 N/mm² to 7.5 N/mm² respectively as bath temperature increases from 35 °C to 100 ºC. The results also showed that the microstructure of the quenched steel samples can be changed and significantly improved by varying the bath temperature. Reasons for variation in mechanical properties and microstructure are discussed.

Keywords: Quenching, temperature, vegetable oil, steel, cooling rate, mechanical properties.