VIABILITY ASSESSMENT OF PALM KERNEL OIL-BITUMEN BLEND AS QUENCHING MEDIUM DURING AUSTEMPERING OF STEEL

Abstract

Viability assessment of palm kernel oil-bitumen blend as quenching medium during austempering of steel was carried out. The samples were austenitized at various temperatures range; 850-9500C. Microstructural analysis and mechanical tests were carried out on the austempered steel to underscore the level of severity and viability of the quenchant. These tests include tensile test, impact test and hardness test. Results of measured hardness indicate that  austempered 0.56%C and 0.76%C-steels posses higher hardness values; 502 and 513 HV compared to that of as-received same steel types (321 and 406 HV). This implies an improvement on the as-received sample as a result of formation of bainite structure and diffusion of carbon precipitates into the steel. A two-factorial empirical model expressed as; ξ = -0.0436₰2 – 0.0135ϑ2 + 2.4173₰ + 24.0915ϑ - 10263.83 derived to interpolate and extrapolate the relationship between the quenched steel hardness and austempering temperature & time indicated a quadratic relationship. Comparative analysis of the correlations between the steel hardness and austempering temperature & time as obtained from experiment and derived model indicated that they were all > 0.99. The maximum deviation of the model-predicted steel hardness (from experimental results) was less than 3.5%. This translated into over 96% operational confidence for the derived model as well as over 0.96 reliability response coefficients of quenched steel hardness to the operational influence of the austempering temperature and time.

 

KEYWORDS: Viability Assessment, palm kernel oil-bitumen blend, quenching medium, austempering, steel