Investigation of Impact Toughness of SMAW, GMAW, and FCAW of API X60 Pipeline Steel

Abstract

Pipelines are a cost effective and efficient technique for transmission and distribution of oil and gas both nationally and internationally. To be able to transport such an enormous amount of gas over thousands of miles and under high pressure, it is necessary to use pipeline steel that has an ideal combination of weldability, strength, and toughness. To construct such an extensive network of pipelines, a variety of welding techniques have been adopted. The welding process includes various welding parameters, filler materials, and heating input, all of which directly influence the toughness of the parent materials. The present study investigates the impact toughness of x60 welded pipe steel by using Charpy test. Three V-notch specimens were tested from the base metal, three specimens from both weld-zone (WZ) and heat affected zone (HAZ) for shield metal arc (SMAW), gas metal arc (GMAW) and flux core arc welding (FCAW) processes. The specimens were tested at temperatures of -196°C, -40°C, -20°C, 0°C, and 20°C. Heat input for SMAW, GMAW and FCAW is 2.34 kJ/mm, 2.13 kJ/mm and 1.91 kJ/mm respectively. The GMAW process exhibited the highest impact toughness in both zones regardless of the testing temperatures. Conversely, the lowest impact toughness values were observed in the heat-affected zone of the SMAW process and the weld zone of the FCAW process. The test results show that the WZ absorbed more energy than the base materials, and the HAZ absorbed less energy.