The Study of the Effect of O2 Contamination on Discoloration at Root Pass Welding of Titanium Grade 2 Pipe ASTM B 861 Using Gas Tungsten Arc Welding

DOI: 10.14416/j.ind.tech.2024.08.011

Abstract

This study investigates the discoloration of as-welded titanium pipes using gas tungsten arc welding (GTAW) in accordance with the NORSOK standard M601:2016, which provides guidelines for welding and inspecting titanium piping. A key focus of this research centers on the precision of visual inspections, particularly when employing a borescope to examine the root weld within the pipe. The principal objective is to establish a standardized reference table for evaluating the discoloration of as-welded titanium pipes at the root, considering both visual inspections conducted with and without a borescope. The GTAW process was conducted under controlled conditions by deliberate manipulation of oxygen concentration in the Argon atmosphere, ranging from 50, 100, 300, to 700 parts per million (ppm). Furthermore, travel speed was regulated to create variations in heat input. A comparative analysis was conducted, contrasting images obtained inside the pipe using a borescope with images of the root after a lengthwise cut. The findings reveal that the images captured through the borescope exhibit darker shading; however, this divergence does not compromise the quality of interpretation. Notably, oxygen concentrations exceeding 100 ppm led to significant discoloration, rendering the material unsuitable for use at any travel speed.