Effect of heat treatment on the performance of 30MnB4 steel for being used as grade 10.9 bolt material

Abstract

Due to technological advancements, alloy steels are now widely used in producing high-strength bolts through various heat treatments. One of the essential features desired in bolts is their strength, as they are subject to heavy loads. This strength is referred to as bolt quality, and interest in heat treatment methods applied to increase the strength of alloy steels is increasing. The mechanical properties achieved from different heat treatment methods and chemical compositions vary. This study aimed to impart the mechanical properties of grade 10.9 steel bolts onto 30MnB4 steel by applying different heat treatments. The effects of tempering temperature on tensile strength, yield strength, elongation at break, reduction in cross-sectional area at break, hardness, and notch impact values at -20°C were examined by passing the prepared samples through five different tempering processes after preheating, annealing and quenching processes. The results revealed that the mechanical properties of grade 10.9 steel bolts were imparted to 30MnB4 steel at all tempering temperatures applied within the scope of the study. Yield strength, tensile strength, hardness, and -20°C notch impact values increased as tempering temperature decreased, while elongation at break decreased. This study adds 30MnB4 steel to the literature as an alternative material that can be used to produce grade 10.9 steel bolts. In addition, mechanical properties obtained depending on tempering temperatures have also revealed the usability of 30MnB4 steel for different applications requiring high strength and toughness values.