Microstructure and Properties of Graphitized Free-Cutting Steel

Abstract

This article describes the metallographic studies and the tensile tests of quenched and high-temperature tempered samples of graphitized free-cutting steel and the experience of machining graphitized samples. The experimental results have shown that the microstructure of the graphitized steel is comprised mainly of ferrite and graphite, and graphite particles are distributed both along grain boundaries and inside them. The morphology of graphite is presented by a spherical shape (average diameter of ~10 μm). The ratio of the yield stress to the ultimate strength is 0.59, and the machinability coefficient is k_T = 5.4241. The microstructure of steel samples after quenching and high-temperature tempering is comprised mainly of secondary sorbite. In this case, the ratio of the yield stress to the ultimate strength is 0.82.