Parametric study of cold wire tandem submerged arc welding of heavy gauge X70 linepipe steel

Abstract

Cold wire tandem submerged arc welding (CWTSAW) has been developed to improve the productivity (i.e., deposition rate and travel speed), and to control the weld and heat-affected zone (HAZ) geometry and mechanical properties of heavy gauge pipe. A series of CWTSAW trials were conducted on thick-wall American Petroleum Institute (API) X70 steel plates to investigate the effect of cold wire feed speed (CWFS), heat input (HI) and bevel design (BD) on the resulting geometry (e.g., height of reinforcement area (HRA), bead toe angle (BTA) and coarse grain heat-affected zone (CGHAZ) area) and micro-hardness of the weld and HAZ. The phase fraction of martensite-austenite (MA) constituents was measured using optical microscopy (OM) and scanning electron microscopy (SEM). Vickers micro-hardness measurements were taken of the weld metal and across the HAZ. The geometry and hardness measurements were statistically correlated with the weld parameters using Taguchi methodology. The results showed that the weld bevel design (BD) was the dominant factor influencing the HRA, CGHAZ area and BTA. Cold wire feed speed (CWFS) had a strong influence on the micro-hardness and phase fraction of MA constituents in the CGHAZ.

Influence of single and tandem-submerged Arc Welding on ASTM A572 Gr.50 steels

“…The addition of the cold wire reduces the overall heat introduced to the weldment, decreasing dilution and the coarse grain heat-affected zone (CGHAZ) area, while faster cooling rates result in lower microhardness values in the CGHAZ. Tailin Ren et al [17] investigated the critical role of optimizing process variables in CWTSAW to enhance productivity, control weld quality, and improve mechanical properties in heavy gauge pipe welding applications. The cold wire feed speed signi cantly in uences micro-hardness pro les by modifying local thermal cycles [18].…”