Effect of Postweld Heat Treatment on the Mechanical Properties of Weld in a Medium Carbon Steel

Abstract

This paper presents the result of an investigation of the effect of postweld heat treatment on the mechanical properties of weld in 0.36%C medium Carbon Steel. Samples were prepared and welded using Shielded Metal Arc Welding (SMAW) process with a low hydrogen electrode. The welded samples were subjected to postweld heat treatment (stress relief) at four different temperatures: 550°C, 600°C, 650°C and 700°C followed by air-cooling. Microstructural examination was carried out to determine the change in microstructure before and after postweld heat treatment. The mechanical properties of the samples were also tested before and after the heat treatment. It was established that a hard microstructure, susceptible to Hydrogen Induced Cracking (HIC), was formed in the heat affected zone of the as-welded samples and that postweld heat treatment improved the mechanical properties of the weld and substantially reduced or eliminated the risk of HIC.