Increased Hardness Value of Medium Manganese Steel Through Double Tempering, Hot Rolling, and Variation of Cooling Media

Abstract

Research has been conducted to enhance the hardness value of medium manganese steel through a heat treatment. Initially, this process begins with austenization at a temperature of 900°C, followed by tempering at 650°C and double tempering at 600°C, with each stage lasting 30 minutes. Subsequently, each stage concludes with a hot rolling process, after which air or water cools the material. As a result of these processes, the hardness tests revealed an increase in the hardness of medium manganese steel, reaching up to 389.70 BHN with a tensile strength of 827 MPa, which was notably achieved through air cooling. This significant increase in hardness is attributed to the emergence of the martensite phase and the presence of a large number of carbides, which are more evenly distributed after the double-tempering process. Additionally, small amounts of carbides were observed in the austenite matrix. Upon examination of the SEM fractography results, it was revealed that the fracture was mixed, with a cleavage area slightly larger than the dimple area. This observation suggests that despite its high hardness value, the sample retains good toughness.