EFFECT OF THERMOMECHANICAL TREATMENTS ON MECHANICAL PROPERTIES AND MICROSTRUCTURE OF 55 Cr 3 SPRIG STEELS

Abstract

The effect of thermomechanical treatment on the microstructure and mechanical properties of 55Cr3 spring steel was studied. Thermomechanical treatment utilizes the hot deformation process so that, in addition to deformation, the microstructure is influenced in order to obtain favorable mechanical properties. Generally, increased strength with improvement in toughness. The aim of thermomechanical treatment is to form a supersaturated solid solution with non-recrysallized structure upon hot deformation and quenching. The steel is deformed when austenite is present in its stable state just above Ac3 and then quenched to martensite state, followed by tempering at a suitable temperature. For a large number of steel grades the thermomechanical treatment is one of the most effective possibilities to achieve a strength- toughness relation superior to that obtained after conventional heat treatment It has been found that thermomechanical treatment produces supenor hardness, strength, and impact compared to conventional heat treatment Tempering the resultant condition at high temperatures is the same as conventional heat treatment which causes a drop in strength values, whereas tempering at lower temperatures (300 & 400°C) maintain the hardness at high values.