Effects of Heat Treatment Process on Mechanical Properties of Medium Carbon Steel

Pham Thi Hang

doi:10.31817/vjas.2021.4.4.07

Abstract

In order to select an appropriate heat treatment process for an industrial application of S45C medium carbon steel, it is necessary to investigate the influence of technological parameters during the heat treatment process such as heating temperature, holding time and cooling medium on the microstructure and mechanical properties. In this study, the experiments were conducted in various heating temperatures, holding times and cooling mediums for specimens made of S45C steel. Then, the relationship between the microstructure and the hardness of the steel was examined. The obtained results show that the heating temperature and cooling medium strongly affect the microstructure of this steel, leading to considerable changes in the hardness. The hardness of S45C steel was markedly improved when heated above 800oC and cooled in water. Moreover, the holding time needs to be carefully calculated to obtain finer grain structure to prevent an increase in the brittleness.

Highlights

Carbon steels can be classified into four main groups as low carbon steel, medium carbon steel, relatively high carbon steel, and high carbon steel depending on the percentage of the carbon in the steel
In order to investigate the effect of heating temperature, holding time, and cooling medium on the microstructure and mechanical properties of S45C steel, the experiments were carried out in different conditions (Table 2)
Due to the considerable amount of ferrite phase, the hardness of this steel before heat treatment was quite low with a value of about 12HRC on average

Summary

Introduction

Carbon steel is defined as a combination of iron, carbon, and some other impurity elements with a quantity of carbon of less than 2.4%. From the Fe-Fe3C phase diagram, the critical points where the phase transformation occurs for S45C steel (with 0.45% carbon) are determined Another important parameter of heat treatment is the holding time. The high-temperature phase austenite in steel might transform into various phases such as coarse pearlite, bainite, or martensite depending upon the cooling rate (Schindler et al, 2009; Adeyemi & Adedayo, 2009) These phases will considerably change the mechanical properties of the steel after the heat treatment process (Jo et al, 2020). The experiments were conducted in different conditions to investigate the influence of the heat treatment factors such as heating temperature, holding time, and cooling medium on the microstructure and mechanical properties of S45C steel. Some conclusions on the appropriate condition for the heat treatment process for S45C were induced

Materials and Methods

Experimental setup

Results and Discussion

Conclusions