Effect of using different backing plate materials in autogenous TIG welding on bead geometry, microhardness, tensile strength, and fracture of 1020 low carbon steel

Abstract This work examines the behavior of using different backing plate materials on weld bead geometry, microhardness, tensile strength, and fracture of 1020 low carbon steel. Autogenous tungsten inert gas welding was performed with and without the use of backing plates. Two different backing plates were tested. It was found that the maximum depth-to-width ratio of 0.63 was obtained when welding was performed without the use of backing plate. It is recommended that backing plates with high thermal conductivity values should be used when faster cooling rates are required; however, if deeper weld penetration is required, the recommendation is not to use any backing plate. The maximum ultimate tensile stress was found to be 412 MPa when welding was performed using 2024 aluminum alloy as a backing plate. On the other hand, the minimum ultimate tensile strength of 373 MPa was obtained when the welding was performed without any backing plate. Using aluminum plates as backing material improved the welded metal strength by only 2%. In addition, the fracture surfaces of the samples were examined by scanning electron microscopy. The use of backing plates depending on their thermal behavior increases brittleness and decreases the ductility of the metals being welded.