Effects of Quenchants on Impact Strength of Single-Vee Butt Welded Joint of Mild Steel

Abstract

The effects of quenching medium on the impact behaviour of mild steel welded joints were investigated, single – vee butt welded joint was employed in welding the samples. The welding was carried out at 100A and at a terminal voltage of 140V (14kW), using gauge 8 coated electrode (4mm size) throughout the welding processes. Four (4) quenching media were employed which are Brine solution (0.1 Molar concentration), two (2) Litres of water, two (2) Litres of diesel oil and abundant air. 8mm thick mild steel bars were used for the heat treatment process at variable annealed temperature steps of 2000C – 4000C – 6000C. The Izod impact machine was employed in carrying out the Impact Test. The results obtained from the test carried out show that quenching in brine solution gives least average impact strength while normalized in air gives highest average impact strength and is the mildest of all the quenchants. The overall results show that air was the best medium for quenching welded mild steel followed by diesel oil, then water and lastly brine solution for quenching welded parts or components under influence of impact or sudden loading. The results will enable engineers, welding personnel and roadside welders select the best and most economic quenchant that will be best suitable for quenching welded components or parts made of mild steel subjected to impact or shocking loading.