Papers by Keyword: Welding

Abstract: This paper reports an experimental study of laser welding on duplex stainless steel UNS S32205 employed in the oil and natural gas industries. A pulsed Nd:YAG laser was used to weld the specimens. Bead on plate condition was used. Scanning Electron and Optical microscopy was applied to measure and analyze the cross-sectional of the weld bead. From the experimental results, it was found that the shape and size of the welded spot depend not only on the laser energy, but also on the pulse duration and the focus position. Metallographic observations showed that the microstructure of the weld metal was characterized by large ferrite grains with intra and inter-granular austenite. Large voids delimited by the molten zone boundary were observed in weld beads with low pulse duration. The heat affected zone resulting from the welding is pretty much absent and no cracks were detected.

Abstract: Within deep drawing processes, welding represents an innovative approach to optimising the branched process chains which entail uneconomic process steps in production and transport lines. Previous applications of thermal joining processes in presses required a downstream process step for joining standardised functional elements such as nuts. Within the scope of this publication, a weldable tool system is presented which offers the possibility of welding a deep drawing component to an automatically added non-standardised holder in a single-step deep drawing process without additional dwell time in the bottom dead point. In order to realise this innovative tool system, the interdependencies of deep drawing and projection welding are considered to enable a splash-free welding on flat and curved component areas, such as the rounding of a punch edge. Based on experimental research a special concept for the tool kinematics of welding electronics is drawn up which is based on press kinematics. In addition, this article also deals with electric insulation and the forming forces which have an impact on the welding electrodes integrated into the active surface of the forming tool. Thus, the joining process becomes independent from the type of press.

Abstract: This paper aims to present some specific aspects regarding the heat affected zone in microwave polymer welding. It presents several results of investigation of the physical and mechanical modification of the HDPE100 polymer when the microwave heating is applied. Burst stress, elongation and relaxation modulus are subject of this research, as well as the information regarding the crystallization rate and elongation viscosity. To reveal the type of the structure and its transformation, Differential Scanning Calorimetry (DSC) was used. The recorded values for rate of crystallization are appropriate for the welding process, but it has negative effect when plastic deformation at high temperature (as in the extrusion process) is applied. The microwave heating produced a 12-20% decreasing of the plasticity with the increasing of the amount of heat introduced into the material (from 65 W power and 10 s heating to 130 W and 40 s). After the microwave heating, the material showed low values for the elongation viscosity, which means not very fluid material and a necessity to apply high temperatures during the processing by welding or plastic deformation.

Abstract: Paper presents the main pollutants of the working environment at welding under flux, methodical determination which the main chemical reactions resulting in pollution and pollution coefficient calculation. A number of welding working regime in order to achieve a coefficient of minimal pollution. The experimental results demonstrate that the process of welding under flux is less polluting than manual arc welding and coated electrode but more polluting than the process of welding in protective gas environment. It shows the influence of welding regime parameters for the most important gas pollutants.

Abstract: Paper presents the main pollutants that appear Gas metal arc welding, the main chemical reactions take place in the melting bath where results the pollutants, determining the impact on the working environment by calculating the coefficient of pollution. The optimization of welding process gives a coefficient of minimum pollution and determines the influence of welding parameters of the system on the appearance of major pollutants elements.

Abstract: Hot gas welding has been used in the process of polypropylene (PP) welding in many applications. It was appropriate for various multipart productions such as plastic constructions, automotive parts, tanks and pipeline. However, the surface properties of welded areas were varied particularly at each zone and thus affected numerous scratch resistances. The microstructure of scratch trace, hardness and scratch wear rate were studied by scanning electron microscope, hardness tester and scratch tester, respectively. From the results, it was found that the deformation of PP was induced with welding process. The scratch trace was showed that it related with decreasing of hardness properties.

Abstract: Photometric stereo works on recovering the shape and reflectance properties of an object using multiple images taken in variable lighting conditions. In this study, a system has been implemented to construct a height field from 12 images of an object. The algorithm which is able to calibrate the lighting direction, find the normals and color albedo at each pixel have been optimized to compute the surface which best fit the normals. This algorithm was also implemented to the welding product to reconstruct the shape of welding bead.

Abstract: In view of the current welding industry, there is no automated programming tool for the welding path of square battery cover. According to differential geometry theory, the principle of nonlinear error is analyzed. Then a simplified model for nonlinear error is established. Based on these, an efficient algorithm based on nonlinear error is proposed. According to the proposed algorithm, two instantiation of the algorithm are presented. Therefore, the proposed algorithm is simple, reliable, and efficient. It adapts to the requirement of two mainstream spuare battery covers perfectly.

Abstract: In the present research work the determination of residual stress distribution in welded non-oriented electrical steel samples is discussed. Tungsten Inert Gas and Electron Beam Welding were used as the welding methods. The residual stresses induced by welding estimated by the magnetic, non-destructive method of Barkhausen noise and were compared with the values resulting from the semi-destructive method of X-ray diffraction Bragg-Brentano (XRD-BB). In order to evaluate accuracy and reliability of the magnetic methods applied, the steel samples were subjected in both compressive and tensile stress and the magnetic noise values were correlated to residual stress values through an appropriate calibration curve. Furthermore, the fluctuations of the residual stresses in the welding zones of the welded samples were discussed on the basis of the experimental evidence and the microstructural changes occurring during welding. It was found that the residual stress determined by MBN method was in good agreement with the XRD-BB results. However, the residual stress determined by magnetic permeability method was not in good agreement with the XRD-BB results. In contrast to the XRD-BB method, the magnetic techniques required a precise calibration procedure in all zones with noticeably different microstructure.

Abstract: This work presents two-dimensional model of exothermal chemical reaction propagation at the conditions of dissimilar materials conjugation when ignition is carried out from end. The melting of the reagent is taken into account in the model. The convergence of numerical algorithm was studied. It was demonstrated that conversion regimes are different for various properties of conjugated materials.