The Effects of Temper Bead Welding Technique on Weld Integrity for In-Service Welding of Carbon Steels

Abstract

The maintenance of pipeline infrastructure is a significant integrity consideration for the pipeline industry. Employing traditional repair techniques, whereby to conduct repairs when the pipeline is shut-down and drained, can result in significant losses to revenue and production. There is industry demand for repair techniques that allow both scheduled and emergency ‘in-service’ weld repair techniques to be developed. As a result, in-service welding with the temper bead technique is becoming increasingly common for repair operations. During in-service welding, the two most prevalent metallurgical concerns are burn-through and hydrogen induced cracking (HIC). The risk of burn-through can be limited through appropriate welding parameter and heat input control during welding. The temper bead welding technique utilizes special bead placement to ensure appropriate heat flow throughout the weld zone to metallurgically improve resistance to HIC. In this study, a series of shielded metal arc welding (SMAW) coupons were produced on 0.250″ thick carbon steel plates subjected to water-cooling. Single and double-layer deposits were made. The second layer tempering bead heat input was purposely varied from plate to plate. The first layer of the welds were all performed using similar welding parameters, so the “tempering” effect from the second weld layer on the metallurgical properties of the resultant welds could be examined. To further expand the understanding of important procedural variables for in-service welding applications, this study investigates the effect of welder technique on the weldment properties achieved during temper bead welding.