Characterising Residual Stresses in a Dissimilar Metal Electron Beam Welded Plate

AbstractDissimilar metal welded components are becoming increasingly common in industrial applications especially in the nuclear sector. Dissimilar metal welding refers to the joining of two materials from different alloy groups. One of the basic requirements of the dissimilar metal welded joint is that the joint strength should be greater than or equal to that of the weakest member and a careful characterisation of the joint is crucial before considering the applicability of the dissimilar metal welded components. The current paper explores the feasibility of an electron beam welded joint between ferritic/martensitic Grade 91 or more commonly known as modified P91 and austenitic 316LN stainless steel, without the addition of any filler material. The residual stress distribution arising from the welding is determined from measurements using neutron diffraction experiment and predictions using finite element analysis. The measured data has been analysed using Rietveld and single peak fits. The finite element analysis was conducted on a two-dimensional cross-sectional model using ABAQUS code, implementing the effects of solid-state phase transformation experienced by P91 steel. The predicted residual stresses are compared with the experimental measurements and conclusions are drawn on the final residual stress distribution

Finite Element Simulation of Laser Welding in a P91 Steel Plate

New methods for joining materials used in advanced nuclear power plants are of interest to increase the efficiency and productivity. Optimised joints require narrow heat affected zones, low residual stress, strain and distortion. This requires research into a large range of aspects including the nature of the joining processes, characterisation of the joint materials and the integrity of joints in manufacture and service. Of particular interest is the laser welding of the P91 steel used extensively in the power plants. The objective of this paper is to fully characterise the laser welding process using numerical modelling techniques and compare the measured residual stresses for P91 steel welds induced by the welding process with the predicted residual stresses by numerical simulation. The FE simulation consists of thermal analysis and a sequentially coupled structural analysis. Solid state phase transformation is included in the analysis to account for the volumetric changes due to martensitic transformation during cooling. The neutron diffraction technique is used to measure the residual stresses in the welded plate. The measurements are compared with the simulation results and the characteristics of the residual stress distribution and the influence of phase transformations are discussed.</jats:p