Distortion Control during Welding of AH36 Plates

摘要

One of the major problems during welding is the occurrence of distortion. Approximately 30% of the total labor cost is spent on the straightening of distorted components in the shipbuilding industry [1]. Residual stresses are always present after welding; these stresses are often in the order of the yield strength of a material and can have a negative influence on the strength of welded structures. Considerable efforts have been made in controlling welding distortion prior to during or after welding. Pre and post-processing treatments can be costly and time consuming, and require skilled workers. In-process methods do not require additional pre or post-processing steps. A widely accepted group of these in-process techniques apply heating sources in addition to the welding heat source to reduce welding distortion. Transient Thermal Tensioning (TTT) is one of these methods, which alter the temperature field and thereby the stresses in the work-piece resulting in a reduction of welding distortion. In this paper, TTT is applied during gas metal arc butt welding of 6 mm thick AH36 steel using special acetylene-air burners as side heaters. It is shown that out-of-plane deformation of the plates is reduced by 70%. In order to understand the distortion reduction mechanism in TTT during welding, 3D thermal-mechanical finite element models have been constructed and validated by temperature and distortion measurements. The numerical results are compared to the experimental measurements.