Effect of Normalizing and Hardening on Mechanical Properties of Spring

Abstract

This study was carried out to investigate the effect of heat treatment (Normalizing and Hardening) on the mechanical properties of springs. The springs were made from mild steel rod having a diameter of 6 mm, a total of 15 springs were made. The springs were then subjected to various heat treatment processes which included; normalizing, hardening and tempering. The heat treated springs were then subjected to various test in other to determine their mechanical properties, these included; impact toughness test, hardness test and tension test. The normalized spring had more strength, was harder and was much tougher than both the annealed and as received springs. The water quenched springs were the hardest of all the heat treated springs, were very brittle and had the lowest percentage elongation. Their strength was also lower than that of the normalized and as received springs. The water quenched and tempered springs had better mechanical properties required for spring making, they had the optimum combination of hardness, strength and tough-ness when compared with the other heat treated springs.