Papers by Keyword: Weld Seam

Abstract: The study investigates the kinetics of plastic deformation propagation in a welded joint of 10G2FB steel after submerged arc welding. A metallographic analysis of the microstructure of the weld seam, fusion zone, and heat-affected zone was performed. Tensile testing and electron microscopy studies were conducted to determine the mechanisms of plastic deformation and crack initiation. It was found that the fusion zone is the most vulnerable to the formation of deformation defects, which can affect the durability of the structure. Recommendations for optimizing welding parameters to improve the mechanical properties of welded joints are proposed.

Abstract: The microstructure and impact toughness of joints of HG785D high strength steel welded by metal active gas shielded arc welding (80%Ar+20%CO2) was observed and analyzed. The result showed that the microstructure of weld seam was mainly composed of acicular ferrite, the impact energy of which was better. While the microstructure of HAZ with large size bainite and M-A island. Using the method of EBSD, it's also found that the effective grain size of weld seam was similar with fine grain HAZ. However the proportion of high-angle grain boundary in weld seam was much larger than that of HAZ. As a result, it could arrest propagating cracks and enhance the toughness.

Abstract: As new generation of low alloy high strength steel, WELDOX960 is extensively applied into heavy-duty fields including engineering machine etc. This paper adopts mixed gas protection welding to make multi-layer and multi-channel welding to low alloy high strength steel WELDOX960, using match methods with different intensities to prepare six groups of samples, respectively. The performances including joint tension and impact etc are tested for analysis after welding. The result shows that backing welding is the most important technique process in multi-layer and multi-channel welding, which has significant impact to joint performance, in the precondition that the strength is satisfied, if the material with lower strength is taken as backing layer, toughness and plasticity of the joint can be improved significantly. For example, tensile strength of sample 50-90 reaches 966.3Mpa, which is the same as 90-90, however, its toughness increases by 15%.

Abstract: This study investigates the influence of heat treatment on the properties of welded steels 1.4404 and 1.4571 of high thickness concerning the forming properties by rolling and the final properties. The weld seam is a region in the work piece where the material can have a higher resistance to deformation. The strength of the weld seam is often higher than in the parent metal. Therefore a suitable pre-heat treatment (1050°C for 30 min) was applied to the weld seam and heat affected zone within the cold rolling process to achieve a more homogeneous distribution of strength and ductility over the entire work piece. A second heat treatment (1050°C for 60 min) after the rolling was done to obtain the solution annealed structure of the steels. To compare the effect of the heat treatments and of the deformation during rolling (work hardening) tensile tests were performed after each process step. Here both materials behave slightly differently. Metallographic investigations show how the microstructure is influenced and give a clear picture of the fracture occurring. Force – time behaviour during rolling was monitored and provides information about the improvements by the preliminary heat treatment. Cold rolling of welded plates is characterized by a force peak just when the weld seam is within the gap of the rolls. The application of heat treatment has been found to lower that force peak and ensures less distortion in shape during the cold rolling passes.

Abstract: This paper studies the dynamic modeling of weld seam by using the laser vision sensor in virtual environment (VE). By introducing virtual guide (VG), lowering operative difficulty and showing high security can be obtained. Template matching is used to recognize remote weld seam, and the uniform contour of V is defined to represent the features of remote seam. Cubic spline interpolation is employed to construct the continuous model of the seam.

Abstract: Prototype observation and finite element analysis were carried out on a weld seam between a spiral case and a penstock of #6 generator in a certain power plant. According to the observation data and finite element calculated results, deformation and stress were analyzed for the weld seam in continuous operating stage (power generation, EL. 206.00). The results show that in the normal operation power generation stage, the strengths of the penstock, the spiral case and the weld seam are all satisfied; Even if the inlet water level reaches to EL. 275.00, the three parts are all safe (when the residual stress isn’t considered, the stress is far lower than the strength allowed values). However, the stress at point E is obviously higher, it is necessary to make further testing inspection. Finally the following suggestions are given: (1) the strain gauges should be arranged both circumferentially and axially, this is because the circumferential stress of weld seam is greater than axial stress; (2) the stiffener rings should be moved left by 50mm, thus the axial stress can be minimized and the circumferential stress can also be reduced.

Abstract: Deep drawing of square boxes of tailor-welded blanks (TWBs) was studied by experiment and simulation in this paper. When the tailor-welded square boxes with different thickness was drawn to square boxes, the weld seam moved towards the thick part on the bottom and towards the thin part on the wall of square boxes. If the blank-holder force was very small, the wrinkling will happen on the thin part. If the blank-holder was very large, fracture will occur on thin part. Draw beads and non-uniform blank-holder force were investigated to control the deformation of the TWBs workpieces in this paper. When using the draw beads during TWBs drawing, using draw beads in both sides was better measures to control the movement of the weld seam. When non-uniform blank-holder force was used to control the movement of weld seam of tailor-welded blanks, it should be choice that the non-uniform blank-holder force on thick part was a half of that on thin part. It was shown that draw beads give better effects on the control of TWBs drawing than other methods. The variation of thickness was little in the bottom, and the variation of thickness was obviously in the corner of bottom. The maximal variation of thickness of TWBs workpieces on different area was both about 90.1%.

Abstract: The stamping process of the tailor welded blank(TWB) was simulated by the software of DYNAFORM. The finite element model of a boxy part was founded, and the forming of different thickness and properties of the material was studied. Meanwhile, the influence of weld seam on forming result was analyzed. The results show that the weld seam model which founded by real properties can describe the plastic deformation and strain distribution more exactly in the forming process.

Abstract: This passage develops a set of arithmetic process for the image of the weld seam in flanges, which suits the weld process according to the feature of the seam. In terms of the arithmetic process for image, traditional methods are replaced by the opening and closing of mathematical morphology, which effectively smoothes the interferences of weld points, surface scratches, glistens and false edges, thus forming sharp and smooth image of weld seam. The arithmetic process of image proves to be brief and highly effective, which meets the practical need of the construction supported by the image of the weld seam. This passage also, taking weld seam as an example, focuses on the discussion of the erosion and dilation of the opening and closing calculations, which are of great value towards administering the process of processing editing the image.

Abstract: Longitudinal weld seams are an intrinsic feature in hollow extrusions produced with porthole dies. The formation of longitudinal weld seams is a solid bonding process, controlled by the local conditions in the extrusion die. Being the weakest areas within the extrusion cross section, it is desirable to achieve adequate properties of these weld seams. In our research, the concept of a weld seam integrity indicator as a means of quantifying bonding efficiency is introduced. The value of this indicator depends on a number of factors: the material flow within the die weld chambers, an adequate pressure level acting on the weld planes and finally the evolution of the metal microstructure. Optimisation of the welding conditions leads to a higher value of the weld seam integrity indicator and thus to improved weld seam properties. The objective of the research presented in this paper is to assess the feasibility of this concept. In lab-scale experiments, AA6060 and AA6082 aluminium alloy billets were formed into strips by means of the direct hot extrusion process. By utilising porthole dies a central longitudinal weld seam is formed. The effect of different geometries of the weld chamber and the processing conditions on the quality of the weld seam are investigated. Characterisation of these weld seams through mechanical testing, focusing on the ability of the weld seam area to accommodate plastic deformation following the onset of plastic instability, and microstructural analysis provides insight into bonding performance. The outcome of this characterisation provides a basis for an estimation of the weld seam indicator. Through computer modelling, the particular process conditions related to weld seam formation are calculated and correlated with the experimental results. The experimental results clearly demonstrate that weld seam formation is controlled by a combination of factors as described above. Inadequate fulfilment of these conditions, verified by the FE-simulations, is the cause of inferior weld seams, associated with low values of the weld seam integrity indicator. Through further elaboration of the concepts presented in this work, the weld seam integrity indicator is to be developed, with the future aim of predicting the weld seam performance through finite element simulations.