Hybrid laser-arc welding of laser- and plasma-cut 20-mm-thick structural steels

It is already known that the laser beam welding (LBW) or hybrid laser-arc welding (HLAW) processes are sensitive to manufacturing tolerances such as gaps and misalignment of the edges, especially at welding of thick-walled steels due to its narrow beam diameter. Therefore, the joining parts preferably have to be milled. The study deals with the influence of the edge quality, the gap and the misalignment of edges on the weld seam quality of hybrid laser-arc welded 20-mm-thick structural steel plates which were prepared by laser and plasma cutting. Single-pass welds were conducted in butt joint configuration. An AC magnet was used as a contactless backing. It was positioned under the workpiece during the welding process to prevent sagging. The profile of the edges and the gap between the workpieces were measured before welding by a profile scanner or a digital camera, respectively. With a laser beam power of just 13.7 kW, the single-pass welds could be performed. A gap bridgeability up to 1 mm at laser-cut and 2 mm at plasma-cut samples could be reached respectively. Furthermore, a misalignment of the edges up to 2 mm could be welded in a single pass. The new findings may eliminate the need for cost and time-consuming preparation of the edges.

Optimization of Argon Gas Metal Arc Welding Process Parameters with Regard to Tensile Strength for AISI 310 Stainless Steel Using Taguchi Technique

Gas metal arc welding (GMAW) is the leading process in the development of arc welding process for higher productivity and quality. In this study, the effect of process parameters of argon gas welding on the strength of T type welded joint of AISI 310 stainless steel is analyzed. The Taguchi technique is used to develop the experimental matrix and tensile strength of the welded joint is measured using experimental method and finite element method. Optimization of input parameter is performed for the maximum tensile strength of welded joint using ANOVA. The results showed that welding speed is the most significant factor affecting the tensile strength followed by voltage in argon gas metal arc welding (AGMAW) process. Argon gas welding process performance with regard to the tensile strength is optimized at voltage: 18.5 V, wire feed speed: 63 m/min and welding speed: 0.36 m/min.

Numerical and Experimental Validation of Gas Metal Arc Welding on AISI 441 Ferritic Stainless Steel Through Mechanical and Microstructural Analysis

Residual stresses and strains, distortion, heat affected zone (HAZ), grain size changes and hardness variation during gas metal arc welding (GMAW), are fundamental aspects to study and control during welding processes. For this reason, numerical simulations of the welding processes represent the more frequently used tool to better analyse the several aspects characterizing this joining process with the aim to reduce lead time and production costs. In the present study an uncoupled 3D thermo-mechanical analysis was carried out by two commercial finite element method (FEM) software to model an experimental single bead GMAW of AISI 441 at different process set-up. The experimental HAZ and measured temperatures were used to calibrate the heat source of both the used numerical codes, then a validation procedure was done to test the robustness of the two developed analytical procedures. One software was used to predict the residual stresses and strains and the distortions of the welded components, while in the second software a user routine was implemented, including a physical based model and the Hall-Petch (H-P) equation, to predict grain size change and hardness evolution respectively. The results demonstrate that the predicted mechanical and microstructural aspects agree with those experimentally found showing the reliability of the two codes in predicting the thermal phenomena characterizing the HAZ during the analysed welding process.