Finite element modelling of a submerged arc welding process
S.W. Wen*, P. Hilton, D.C.J. Farrugia
British Steel, Swinden Technology Centre, Moorgate Road, Rotherham S60 3AR, UK
Abstract A multi-wire submerged arc welding (SAW) process has been modelled using a general purpose ®nite element package ABAQUS. The paper explainsbrie¯y the welding process and its application in thick wall linepipe manufacturing. Corresponding 2D and 3D ®nite element (FE) models of the SAW process are presented. FE analyses were carried out to investigate the heat transfer characteristics in the fusion and heat affected zones during welding. The effect of process parameters and weldment geometry have been evaluated with and without theconsideration of residual stresses and strains induced from the forming processes prior to welding. Comparisons of FE predictions with experimental results are presented where it is appropriate. It is shown that the geometrical distortion and residual stresses and strains caused by welding can be minimised through process optimisation. It is therefore demonstrated that ®nite element analysis can beapplied to better understand the SAW process and hence be a useful tool for future process development and control with the view of optimising product properties. # 2001 Elsevier Science B.V. All rights reserved.
Keywords: Welding; Finite element; Residual stress and strain
1. Introduction Arc welding is a complex process which involves the interaction of physical, chemical and mechanicalphenomena that are currently far from being understood, such as plasma±metal interaction, metal±gas/¯ux reaction, weld pool ¯uid ¯ow, electromagnetic stirring, phase transformation, heat transfer, weld metal chemistry, heat affected zone (HAZ) microstructure, residual stress, mechanical properties, etc. [1,2]. Previously, researchers and scientists have devoted much of their effort to welding physicalmetallurgy, weld metal and HAZ microstructure characterisation, and welding process optimisation. Recently, numerical simulation has been increasingly used as a tool to assist welding process analysis and optimisation, and in particular applied to the prediction of welding induced residual stress and strain [2±8]. Residual stress and strain induced by arc welding processes have been recognised as amajor factor affecting the ®nal in-service performance of the weldment, such as fatigue and brittle fracture behaviour (including sulphide stress corrosion cracking). Traditional methods for welding induced residual stress and strain characterisation are mainly experimental, and include hole drilling, X-ray, neutron diffraction, ultrasonic and demountable mechanical gauge measurement. However, theapplication of these methods in practice is usually limited by either cost or accuracy.
Numerical simulation based on ®nite element (FE) techniques, therefore, offers a comprehensive solution for the prediction of residual stress and strain as well as welding distortion in welded structures. Andersson  analysed the residual stress distributions in the top andbottom surfaces of the parent plate near the weld during a butt SAW process using a 2D FE approach. The phase transformation during cooling was considered using a volumetric dilatation technique, which was believed to be of primary importance to the residual stress analysis of weldment. Comparison between FE predictions and experimental measurements showed that, although the predicted thermal historyagreed well with experiment, discrepancies existed between the FE results and the measured values in terms of residual stresses. The commercial software package SYSWELD was used by Roelens  for modelling several multipass SAW welding processes, in which the FE models developed were validated under ®ve cases against experimental measurements in terms of thermal history, phase distribution as...