Effect of The Processes of Self-Tempering and Tempering on The Mechanical Characteristics and the Character of Fracture of Low-Carbon Martenstic Steel Quenched in Air

Resumo

Abstract—The influence of the processes of self-tempering and tempering on the mechanical characteristics and structure of low-carbon martensitic steel after air-quenching has been considered in this work. The processes of martensite decomposition (self-tempering) that started upon cooling continue in the steel in the course of subsequent tempering at 200, 300, 400, and 500°C with the formation of a ferrite–carbide mixture of different degrees of dispersion. Upon tempering at temperatures of 200–400°C, a monotonic increase is noted in the yield stress by 11%; the tempering at 500°C leads to a 3% reduction in the yield stress. The character of the fracture of the samples was studied using scanning electron microscopy; this study has confirmed the phenomenon of temper brittleness in the steel at temperatures of 300 and 500°C, which is in good agreement with the results of mechanical tests.