Hardness and Toughness Investigation of ASSAB 705 Steel by Various Tempering Temperatures

Abstract

ASSAB 705 steel is a machinery steel that used in several industries due to its mechanical properties, for components manufacturing. Hardening process is applied to ASSAB 705 to increase mechanical strength thereby increasing hardness. Conversely, an increase in the hardness value will decrease toughness value so that components are easily damaged due to heavy workloads. The optimal combination of hardness and toughness enhances abrasion resistance and maintains component strength against working loads. It is necessary to investigate parameters of hardening process and its effect on the hardness and toughness of ASSAB 705 steel. This study used Design of Experiment with Taguchi method and ANOVA statistical analysis. Hardening parameter with austenite temperature factor, quench media, and tempering temperature, is used to optimize the combination of hardness-toughness value of ASSAB 705 steel. Results of this research show that tempering temperature is the most influential factor on hardness and toughness values. Optimal combination of mechanical strength is obtained at a hardness value of 50.78 HRC (increase of 44.85%) and a toughness value of 1.15 J/mm2 (increase of 109.09%). These values ​​were obtained from the hardening method: austenite temperature of 825°C, oil quench medium, and tempering temperature of 180°C. The desirability value for combination of hardening process parameters is 0,682802.