Effect of Weld Groove Area on Distortion of Butt Welded Joints in Submerged Arc Welding

Introduction

During welding cycle, complex strains occur in the weld metal and the base metal regions near the weld. As a result, residual stresses remain after welding and distortions are produced. Correcting unacceptable weld distortion is extremely costly. In addition, excessive distortion cause mismatches of joints, thus increasing the possibility the welding defects. Excessive lateral distortion decreases buckling strength of structural members that are subjected to compressive loading (Masubuchi, 1996). Thus, the development of proper techniques for reducing and controlling distortion would lead to more reliable welded structures with a reduction in fabrication cost. The stresses resulting from the strains combine and react to produce internal forces, causing shrinkage of the material. Depending on the shrinkage pattern, various structural deformations such as bending, buckling and rotation take place, and these deformations are referred as welding distortions (Mandal et al., 1997).

In arc welding processes, due to rapid heating and cooling, the work piece undergoes an uneven expansion and contraction in all the directions and leading to distortion in different directions of the work piece. Angular distortion is one such defect that makes the work piece distort in angular directions around the weld interface. The extent of angular distortion depends on the width and depth of the fusion zone relative to plate thickness, the type of joint, the weld pass sequence, the thermo mechanical material properties, heat input and the process parameters (Vinokurov, 1977). Hence, various investigations were made to study the effects of various parameters on angular distortion. Kihara and Masubuchi (1956) have studied various welding process parameters, including the shape of the groove and the degree of restraint; affect the angular distortion in butt joints. Hirai and Nakamura (1955) made investigation to determine the values of angular changes and coefficient of rigidity for angular changes as a function of plate thickness and weight of the electrode consumed per unit length of weld.