Butt welding

About: Butt welding is a(n) research topic. Over the lifetime, 7153 publication(s) have been published within this topic receiving 44467 citation(s).

A parametric study of residual stresses in multi-pass butt-welded stainless steel pipes

Abstract: Multipass circumferential butt-welding of stainless steel pipes is simulated numerically in a non-linear thermo-mechanical FE-analysis. In particular, the through-thickness variation at the weld and heat affected zone, of the axial and hoop stresses and their sensitivity to variation in weld parameters are studied. Recommendations are given for the through thickness variation of the axial and hoop stresses to be used when assessing the growth of surface flaws at circumferential butt welds in nuclear piping systems.

Material flow in butt friction stir welds in AA2024-T3

Abstract: The properties of a workpiece joined by friction stir welding (FSW) are directly related to the material flow around the tool. In the present work, the material flow is investigated by traditional metallography as well as X-ray and computer tomography (CT). By introducing a thin copper strip in the workpiece and welding through it, thus, acting as a marker material, detailed information about the flow field is gathered. The two- and three-dimensional CT images are used in parallel with micrographs for visualization of the flow field. Two procedures for estimating the average velocities for material flowing through the shear layer are presented. The procedures depend on the configuration of marker material relative to the welding direction, i.e. longitudinal and transverse. As such, the present work constitutes the first attempt in the literature to estimate flow velocities in FSW based on thorough experimental investigations.

Prediction of welding distortion and residual stress in a thin plate butt-welded joint

Abstract: In automotive industry, thin plate parts are commonly used. During assembling process, welding technology is usually employed because of high productivity. Welding distortion often occurs in thin plate welded structures due to relatively low stiffness. The distortion causes problems not only in the assembling process but also in the final product quality. Therefore, prediction and reduction of welding deformation have become of critical importance. In this study, three-dimensional, thermo-elastic–plastic, large deformation finite element method (FEM) is used to simulate welding distortion in a low carbon steel butt-welded joint with 1 mm thickness. To compare with the large deformation theory, the small deformation theory is also used to simulate the welding deformation and welding residuals stress. Meanwhile, the characteristics of welding temperature field, plastic strain distribution and welding residual stress in thin welded plates are also examined numerically. Experiments are also carried out to measure the welding distortion in the thin plate butt-welded joint. By comparing the simulation results with the measurements, it is found that the results predicted by the thermo-elastic–plastic, large deformation FEM match the experimental values well. Moreover, using the inherent strains obtained by the thermo-elastic–plastic FEM, an elastic FEM is also employed to estimate welding deformation in the same butt-welded joint. Comparing the results simulated by the elastic FEM with those predicted by the thermo-elastic–plastic FEM, it is verified that the inherent strain method can effectively predict the welding deformation in the thin plate butt-welded joint with 1 mm thickness.

Material flow and microstructure in the friction stir butt welds of the same and dissimilar aluminum alloys

Abstract: The material flow and microstructural evolution in the friction stir welds of a 6061-Al alloy to itself and of a 6061-Al alloy to 2024-Al alloy plates of 12.7 mm in thickness were studied under different welding conditions. The results showed that plastic deformation, flow, and mechanical mixing of the material exhibit distinct asymmetry characteristics at both sides of the same and dissimilar welds. The microstructure in dissimilar 6061-Al/2024-Al welds is significantly different from that in the welds of a 6061-Al alloy to itself. Vortex-like structures featured by the concentric flow lines for a weld of 6061-Al alloy to itself, and alternative lamellae with different alloy constituents for a weld of 6061-Al to 2024-Al alloy, are attributed to the stirring action of the threaded tool, in situ extrusion, and traverse motion along the welding direction. The mutual mixing in the dissimilar metal welds is intimate and far from complete. However, the bonding between the two Al-alloys is clearly complete. Three different regions in the nugget zone of dissimilar 6061-Al/2024-Al welds are classified by the mechanically mixed region (MMR) characterized by the relatively dispersed particles of different alloy constituents, the stirring-induced plastic flow region (SPFR) consisting of alternative vortex-like lamellae of the two Al-alloys, and the unmixed region (UMR) consisting of fine equiaxed grains of the 6061-Al alloy. Within all of these three regions, the material is able to withstand a very high degree of plastic deformation due to the presence of dynamic recovery or recrystallization of the microstructure. The degree of material mixing, the thickness of the deformed Al-alloy lamellae, and the material flow patterns depend on the related positions in the nugget zone and the processing parameters. Distinct fluctuations of hardness are found to correspond to the microstructural changes throughout the nugget zone of dissimilar welds.