Numerical Simulation of Residual Stresses due to Multipass Welding in High Strength Steel Plates and Validation against Experimental Measurements

Multipass arc welding is commonly used for thick plates assemblies in shipbuilding. Sever thermal cycles induced by the process generate inhomogeneous plastic deformation and residual stresses. Metallurgical transformations contribute at each pass to the residual stress evolution. Since residual stresses can be detrimental to the performance of the welded product, their estimation is essential and numerical modelling is useful to predict them. Finite element analysis of multipass welding of a high strength steel is achieved with a special emphasis on mechanical and metallurgical effects on residual stress. A welding mock-up was specially designed for experimental measurements of in-depth residual stresses using contour method and deep hole drilling and to provide a simplified case for simulation. The computed results are discussed through a comparison with experimental measurements.

A New Approach to Simulate HSLA Steel Multipass Welding through Distributed Point Heat Sources Model

Mechanical properties of welded joints depend on the way heat flows through the welding passes. In multipass welding the reheating of the heat affected zone (HAZ) can form local brittle zones that need to be delimited for evaluation. The difficulty lies in the choice of a model that can simulate multipass welding. This study evaluated Rosenthal’s Medium Thick Plate (MTP) and the Distributed heat Sources (DHS) of Mhyr and Gröng models. Two assumptions were considered for both models: constant and temperature-dependent physical properties. It was carried out on a multipass welding of an API 5L X80 tube, with 1016 mm (42″) external diameter, 16 mm thick and half V-groove bevel, in the 3G up position. The root pass was welded with Gas Metal Arc Welding (GMAW) process with controlled short-circuit transfer. The Flux Cored Arc Welding (FCAW) process was used in the filling and finishing passes, using filler metal E111T1-K3M-JH4. The evaluation criteria used were overlapping the simulated isotherms on the marks revealed in the macrographs and the comparison between the experimental thermal cycle and those simulated by the proposed models. The DHS model with the temperature-dependent properties presented the best results and simulated with accuracy the HAZ of root and second welding passes. In this way, it was possible to delimit the HAZ heated sub-regions.