Parametric investigation of the submerged arc welding method used in warships

In this study, the mechanical and structural integrity of weld seams after joining DH36 grade structural steel by submerged arc welding at low temperatures were evaluated by both destructive and non-destructive testing methods. Tensile test, flexure test, radiographic inspection, visual inspection and penetrant tests were performed on 15 specimens prepared with different parameters. In order to reduce the adverse effects of low temperatures, pre-annealing in the range of 100-200 °C was carried out before welding, thus stabilising the cooling rate and reducing the risk of cracks. As a result of the tensile tests, an average yield strength of 504.6 MPa, tensile strength of 517.0 MPa and elongation rate of 8.88% were obtained. The low standard deviation values indicate that the mechanical properties are homogeneous between the samples. However, the tensile strength of SBTÜ 1 specimen was below the minimum value with 497 MPa and was evaluated negatively. This was attributed to unsuitable welding parameters. Sequential pore defects were detected in SBTU 12 and SBTU 14 specimens in radiographic examination and it was evaluated that wire contamination, high moisture content or excessive welding speed were the source of these defects. No cracks or ruptures were observed in bending tests. In the visual inspection, metallic bath perforation was determined in SBTÜ 6 and SBTÜ 8 samples and it was stated that the use of root pass or copper substrate would be appropriate. As a result, the parameters used in SBTÜ 15, 4, 7, 10, 5, 6, 3 and 16 samples were found to be successful. The study shows that when appropriate welding parameters are selected, DH36 steel can be joined safely at low temperatures and can provide high performance in heavy manufacturing industry.