Effect of Welding Methods and Sequences on the Residual Stress Distribution of Wellded Joints

• Published in: JOURNAL OF THE JAPAN WELDING SOCIETY Vol. 24; no. 4; pp. 24 - 31
• Main Authors: Satoh, K., Kimura, K., Hoshi, R., Watanabe, M.
• Format: Journal Article
• Language: Japanese
• Published: JAPAN WELDING SOCIETY 1955
• ISSN: 0021-4787; 1883-7204; 1883-7204
• DOI: 10.2207/qjjws1943.24.4_24

In order to control the residual stress and distortion of welded joints, various welding methods such as symmetry, .step back, skip method etc. are used in actual works. In this report, we compared each other the residual stress distributions of the joints welded by these methods. In most case the joints of actual structure are welded under constrained state, and so the determination of welding sequence is one of the most important problems in actual works. In this repot, we used the constrained specimen as shown in Fig. 1, and discussed the effect of welding sequence on the residual, locked-in and weld stresses. For the sake of convenience, we call these experiments "Test I" and "Test II" respectively. Material used is SS 41 steel plate. The specimens in "test I" are 500×200×6 mm bead-welded specimens, 500×100×6mm and 500×100×19mm butt-welded specimens, which, are welded along the 500 mm edge. The welding methods and conditions are shown in Table 1. In "test II", we used the three welding sequences shown in Fig. 2. The residual stresses were measured by SR-4 strain meter. In "Test II" the locked-in stresses were at first measured by cutting the chain line in Fig. 1 and next the residual stresses were measured by usual trepanning method. The results of the tests are shown in Figs. 3, 4, 5, 7 and 8. Fig. 6 shows schematic diagram of the residual stress distribution of bead-welded plate. This diagram was obtained by simple stress analysis. We compared this diagram with the experimental results, and discussed the effect of welding methods and welding sequences. The distributions of residual stress in test I agree in most case with the schematic diagram, Fig .6, but the result of specimen A-4 (skip method) is a little different. In this specimen, transverse stress increases in spite of the decrease of longitudinal stress, and the peaks of residual stress are produced at the last bead. In test II, stress distributions are a little different from the schematic diagram. This difference is due to the disturbance of external constraint and the cross point of welded joint. At last we discussed which method and sequence is favorable from the view point of residual stress distribution. We adopted maximum stress and triaxial ratio as the criterion of comparison, where triaxial ratio is defined by |σ1+σ2+σ3|/3|σmax|. (σ1, σ2, and σ3 are principal stresses and σmax is maximum principal stress.) The maximum stress values and triaxial ratios are shown in Table 2 and 3. From these results we concluded as follows : (1) In the case that the thin plate is welded by one pass, skip method gives comparably small residual stress, but for thick plate welded by multiple pass, cascade block method is most favorable from the view point of residual stress distribution. (2) In constrained specimen, it is favoured to weld at first the shorter joint (for example vn and 'p'Y in specimen "D") before welding longer joint (for example gg' in specimen "D").