Study of the Change in Microstructure and Crystal Structure of Pre-turned C22, C27, and C40 Carbon Steel Alloys after Hardning Heat Treatment

Abstract

This paper aims to conduct an experimental study to evaluate the extent of microstructural changes in carbon steel alloys previously processed by turning, after Hardning heat treatment. Due to the exposure of raw materials to cutting forces and high temperatures during the manufacturing of various products, some mechanical properties, such as hardness, are affected. Therefore, heat treatments are performed on machined and manufactured products to restore their crystalline structure and improve their properties. To verify this, the evaluation is conducted through microscopic examination of several samples of medium-carbon steel (C40) and low-carbon steel (C27,C22) before and after heat treatment. The microscopic examination of the crystalline structures of the samples after heat treatment reveals that the ferrite and pearlite structures were transformed into different shapes, reducing the ferrite volume and transforming the pearlite into thin folds called martensite. The presence of ferrite and pearlite phases, in addition to the martensite phase, was observed. These changes lead to improved mechanical properties of the steel, such as hardness.