Metallurgical characteristics of double-sided arc welding in high strength structural steels

Two 690 MPa-yield steels (100 ksi), ASTM A 514 and Domex 100XF, were welded with newly developed Double-Sided Arc Welding (DSAW) process and evaluated. DSAW is a novel arc process in which the workpiece is disconnected from the power supply and the two torches are used to establish arcs on both sides of the workpiece to close the current loop. As a result, the welding current is forced to flow through the workpiece in the thickness direction. This configuration and current flow direction improves the concentration of the arc energy distribution, provides a mechanism to guide the arc into the keyhole, and introduces strong electromagnetic force into the weld pool, causing a stirring effect. In the two tested steels, a deep, narrow and symmetrical penetration weld profile was produced, a relative even hardness distribution across entire weld joint was formed, and significant grain refinement in weld metal was achieved. The columnar structure in weld metal was altered due to the change of solidification pattern. Fine equiaxed grain structure is the typical feature of weld metal of DSAW process. This provides structural isotropy and chemical homogeneity. This also reduces the risk of solidification cracking and reduces residual stress of weld joint.