Showing papers on "Butt welding published in 2005"

Optimization of Nd:YAG laser welding onto magnesium alloy via Taguchi analysis

Abstract: The use of an Nd:YAG laser for thin plate magnesium alloy butt welding was optimized using the Taguchi analytical methodology. The welding parameters governing the laser beam in thin plate butt welding were evaluated by measuring of the ultimate tension stress. The e7ectiveness of the Taguchi method lies in clarifying the factor that dominates complex interactions in laser welding. The factors can be the shielding gas, laser energy, convey speed of workpiece, point at which the laser is focused, pulse frequency, and pulse shape. Furthermore, 18 combinations of these six essential welding parameters were set and Taguchi’s method followed exactly. The optimal result was con=rmed with a superior ultimate tension stress of 169 MPa, 2.5 times larger to that from original set for laser welding. ? 2004 Elsevier Ltd. All rights reserved.

Computational prediction of out-of-plane welding distortion and experimental investigation - Awarded Central Electricity Generating Board Prize

Abstract: The main aim of the work was to investigate a simplified finite element simulation of the out-of-plane distortion caused by fusion butt welding. The thermal transient part of the simulation made use of a finite element analysis of the two-dimensional cross-section of the weld joint and the thermoelastic-plastic treatment was based on analytical algorithms describing transverse and longitudinal deformations, leading to predictions of transverse angular deformation and longitudinal contraction force. These results were then applied to a non-linear elastic finite element model to provide predictions of the final angular and overall deformations of the butt-welded plates. The validity of the simulation was investigated via full-scale tests on 4m x 1.4m x 5 mm steel plates, butt welded using a flux-cored Ar-CO2 metal-inert gas process. Thermography and thermocouple arrays were used to validate the thermal transient computations and out-of-plane deformations were measured using displacement transducers for transient deformations and a laser scanning system to measure the profiles of the whole plates before and after welding. The results of six full-scale tests are given and comparison with the simulations shows that the procedure provides good prediction of the angular and overall out-of-plane deformations. Prediction accuracy requires account to be taken of initial shape, gravity loading, and support conditions.

Welding robots

Abstract: Using robots in industrial welding operations is common but far from being a streamlined technological process. The problems are with the robots, still in their early design stages and difficult to use and program by regular operators; the welding process, which is complex and not really well known and the human-machine interfaces, which are unnatural and not really working. In this article, these problems are discussed, and a system designed with the double objective of serving R&D efforts on welding applications and to assist industrial partners working with welding setups is presented. The use of object-oriented and distributed software to assist industrial robotic welding applications is discussed. The system is explained in some detail and demonstrated using two test cases that reproduce two situations common in industry: multilayer butt welding and multipoint fillet welding.

Validation of three-dimensional finite element model for electron beam welding of Inconel 718

Abstract: A three-dimensional finite element model for the prediction of the distortion and residual stresses induced during electron beam welding is described. The model is validated by butt welding experiments on two Inconel 718 plates. A particular effort is made to determine a good model for the heat input. A combined conical and double ellipsoid heat source is used to model the deep penetration characteristic of the electron beam and this source is calibrated using the results from a separate thermodynamic simulation, using the ELSIM finite difference code. Parallel computation is used to reduce the overall simulation time in the coupled thermomechanical simulation of welding. The agreement between calculations and experiments is good with respect to the residual stresses. Measured and computed deformations agree qualitatively although they differ in magnitude.

Prediction of welding distortions and residual stresses in a pipe–flange joint using the finite element technique

Abstract: This paper presents a comparative study of three- and two-dimensional axisymmetric finite element (FE) analyses of a welded pipe–flange joint for residual stresses and deformations in order to identify their merits or demerits. Sequentially coupled thermal stress analysis is performed to simulate single pass metal inert gas welding. Butt weld geometry with a single 'V' for a 100 mm nominal diameter pipe and same sized weld neck type ANSI class #300 flange is used. The heat input is modelled by using the Goldak double ellipsoidal heat source model. Temperature dependent material properties are used and deposition of filler metal is obtained by element birth and death feature. Both thermal and structural FE models are validated with experimental measurements. Residual stresses predicted by two-dimensional model are generally on the higher side and hence more conservative. However, we conclude that the three-dimensional FE model is preferable for the prediction of flange face distortion since it is a vital parameter for flange joint performance.

Method for evaluating and/or comparing welding consumables

Abstract: Methods and systems are disclosed for characterizing a welding consumable, such as flux or an electrode, and/or for comparing two or more welding consumables for use in narrow gap deep groove welding operations, including creating test welds on fixtures having joint grooves of various angles for a given groove depth, followed by controlled standardized non-aggressive slag removal operations, and quantification of the amount of slag remaining in the groove, wherein the welding consumables are each characterized using the same fixtures, welding conditions, workpiece groove depths, groove angles, and removal operations, to construct a set of results, such as a table or rating, by which the individual welding consumables can be rated and/or a determination can be made as to which of two consumables provides superior performance with respect to ease of removal in deep groove welding operations.

Effect of Tool Geometry and Process Parameters on Material Flow in FSW of an AA 2024-T351 Alloy

Abstract: In this study the temperature distribution and the flow pattern of an embedded marker material were investigated when friction stir butt welding 4 mm thick 2024-T351 aluminium alloy plate using several welding tool combinations. Friction stir welded plates not embedded with the marker material were tested for micro-hardness and static tensile strength. Results indicated that the ultimate tensile strength of the friction stir welded material could be increased to values approaching that of the base material. The improvement in mechanical strength was found to depend largely on tool geometry in conjunction with weld travel speed. Tool geometry not only influenced the temperatures and micro-hardness experienced for both sides of the weld but also the marker material flow during joining. A micro-computer tomographic investigation of the marker flow indicated that the geometry of the welding tool pin had a significant influence on the material transport and distribution between each side of the interfacing workpieces.

Numerical simulation of welding-induced distortion in thin-walled structures

Abstract: A sequentially coupled thermal stress analysis approach is presented for modelling temperature and distortion profiles resulting from welding thin-walled structures. The material is modelled as thermo-elastic–plastic with isotropic strain hardening. The heat source is modelled as a three-dimensional (3-D) double ellipsoid, and 3-D finite element (FE) models are employed for predicting ensuing distortions. Comparisons between the simulation results and experiments performed for eight weld configurations are presented. The weld configurations include bead-on-plate, butt weld and tee joint welds with varying plate thicknesses. Temperature measurements using thermocouples and an infrared (IR) imaging radiometer are directly compared to the thermal simulations. Likewise, distortions measured directly on the experimental set-ups are compared to the FE distortion predictions. Very good correlation is obtained for temperature as well as distortion predictions between experimental and proposed numerical a...

Effects of pulsed and continuous Nd-YAG laser beam waves on welding of Inconel alloy

Abstract: In the present work a 2·5 kW high power Nd–YAG laser is used in the bead on plate (BOP) and butt welding of Inconel 690 plates of thickness 3 mm. Welding is performed using a rectangular laser pulse, for which the peak to base power ratio Wr is reduced from an initial value of 10 to a value of 1, maintaining an identical mean power of 1·7 kW. Therefore, the welding mode changes from a pulsed wave to a continuous wave. The BOP results indicate that the depth of the weld penetration increases at a lower travel speed and/or a higher value of Wr. In the butt welding process, as Wr is increased from 1 to 10, the cellular microstructure of the weld remains relatively unchanged, but the macroporosity formation ratio decreases from 7·1% to 0·6%. At low values of Wr, macroporosity is identified primarily in the root region. However, as Wr increases, the associated periodic high power increases the agitation of the molten pool and probably causes bubbles to float upwards. Consequently, at higher values of W...

Optimising multiple qualities of Nd:YAG laser welding onto magnesium alloy via grey relational analysis

Abstract: This work evaluates multiple quality optimisation of Nd:YAG laser welding onto magnesium alloy via grey relational analysis. The effectiveness of the grey relational grade lies in quantifying and judging the performance obtained using various combinations of laser welding parameters. The parameters are shielding gas, laser energy, travelling speed of workpiece, point at which the laser is focused, pulse frequency, and pulse shape in this work. Moreover, 18 combinations of these six essential welding parameters were set following Taguchi's method to evaluate the integrated performance. The welding parameters that govern the laser beam in thin plate butt welding were evaluated by measuring the ultimate tension stress, and both the depth and the width along the welding path. This integrated performance was then quantified and judged via grey relational analysis to obtain an optimised set-up for laser welding. The verifying test was proved to optimise the ultimate tension stress, depth and width along...

Residual stress evaluation of butt weld sample of high tensile strength steel using neutron diffraction

Abstract: Welding technique is utilized for many structures as a technique jointing some components. The residual stress, however, induced by welding affects the mechanical properties or failure mechanism. Therefore, it is important to know the residual stress states near the weld zone accurately for improving the reliability of structures. In this study, the residual stress distributions of a double-V butt weld plate were measured using neutron diffraction technique, and the generating mechanism of residual stresses was also discussed. The double-V butt weld plate was fabricated by using Ni-Cr steel (SNC631) which is one of the high tensile strength steel, and its residual stress distributions were measured using diffractometer for residual stress analysis (RESA) located in JRR-3 at Japan Atomic Energy Research Institute. At first, some coupon samples were cut from weld plate in order to measure the lattice constant in stress-free condition. As a result of measuring the lattice constant using coupon samples, the lattice constant was increasing near the weld zone because of some phase transformations such as martensitic transformation due to weld process. Secondly, the residual stress distributions of weld plate were measured with αFe110, αFe200, and αFe211. The residual stress distributions evaluated by each diffraction were almost the same profile throughout the welded plate since no plastic strain was observed near the weld zone. The residual stress near the weld zone was tensile stress of almost half value of yield strength of Ni-Cr steel. It might be reasons why we obtained these results that the tensile residual stresses did not reach yield strength since the transformation expansion of high tensile strength steel is larger than that of mild steel and the tensile residual stress starts to generate at low temperature. It was, therefore, confirmed that the neutron stress measurement can determine the residual stress distribution of welded sample of high tensile strength steel without consideration of the plastic deformation.

Welding machine and relative operating method

Abstract: A welding machine (1) having a welding unit (2) for generating a welding voltage/current, and at least one welding tool (3) connectable to the welding unit (2) by a cable (4) and supplied by the cable with welding voltage/current; the welding unit (2) has a closed protective casing (5), and a cooling unit (8) for cooling the welding tool (3) and/or cable (4) on command; and the welding machine also has a modular unit (16) containing the cooling unit (8) and insertable stably and in easily removable manner inside the casing (5) which is closed for protection of the welding unit (2), so as to be easily extracted and detached from the casing (5).

Residual Stresses Prediction for CO2 Laser Butt-Welding of 304-Stainless Steel

Abstract: Residual stresses are an integral part of the total stress acting on any component in service. It is important to determine and/or predict the magnitude, nature and direction of the residual stress to estimate the life of important engineering parts, particularly welded components. This work aims to introduce experimental models to predict residual stresses in the heat-affected zone (HAZ). These models specify the effect of laser welding input parameters on maximum residual stress and its direction. The process input variables considered in this study are laser power (1.03 - 1.368 kW), travel speed (26.48 – 68.52 cm/min) and focal point position (- 1 to 0 mm). Laser butt-welding of 304 stainless steel plates of 3 mm thick were investigated using a 1.5 kW CW CO2 Rofin laser as a welding source. Hole-drilling method was employed to measure the magnitude, and direction of the maximum principal stress in and around the HAZ, using a CEA-06- 062UM-120 strain gauge rosette, which allows measurement of the residual stresses close to the weld bead. The experiment was designed based on Response Surface Methodology (RSM). Fifteen different welding conditions plus 5 repeat tests were carried out based on the design matrix. Maximum principal residual stresses and their directions were calculated for the twenty samples. The stepwise regression method was selected using Design-expert software to fit the experimental responses to a second order polynomial. Sequential F test and other adequacy measures were then used to check the models adequacy. The experimental results indicate that the proposed mathematical models could adequately describe the residual stress within the limits of the factors being studied. Using the models developed, the main and interaction effect of the process input variables on the two responses were determined quantitatively and presented graphically. It is observed that the travel speed and laser power are the main factors affecting the behavior of the residual stress. It is recommended to use the models to find the optimal combination of welding conditions that lead to minimum distortion.

Single power supply twin-wire automatic submerged-arc welding machine

Abstract: The utility model relates to a single power supply twin-wire automatic submerged-arc welding machine, comprising a welding power and a welding machine. The welding machine comprises a welding car, a bracket, a welding control box, a dual wire reel, a welding flux bucket, a dual wire feeder and a welding wire guide mechanism. The welding power has the dual purpose outer performance of the flat characteristic and the convex characteristic, which can control the wire feeding speed and sustain the stability of the twin-wire arc. The welding machine has high speed of welding wire filling and melting, fast welding speed and low welding seam heat input, which is suitable for the thick plate weld, the thin plate butt welding, the edge weld, the overlap welding as well as the hard facing and the corrosion resistant surfacing.

Mechanical behaviour of overlap joints of titanium

Abstract: Increasing demand for lightweight vehicles as well as for laser welding for automotive technologies in high rate production have pushed the automotive industry to consider the use of expensive lightweight materials with high specific mechanical properties and, as for example titanium, high corrosion resistance. Butt welds have too stringent requirements in relation to laser positioning and clamping methods, so the move to overlap joints is justified. The changes in welding design have to be requalified, in order to determine the geometries that allow the optimum exploitation of the bearing properties of a material. In this paper, the mechanical properties of overlap joints of thin sheets of titanium Grade 2 and of an α/β alloy Ti–6Al–4V are investigated. The results presented allow a very precise classification of the two materials and should help engineers by indicating the optimum material for any given purpose. Ti–6Al–4V offers, for example, the highest strength when statically loaded, while, i...

Finite-element simulation of tack welds in girth welding of a pipe-flange joint

Abstract: Welding deformations play an important role in sealing capabilities and service life of welded pipe-flange joints A numerical procedure for modeling of tack welds in girth butt-welding of such joints is of vital importance for the prediction of transverse shrinkage and flange face deformation, which is directly related to the joint sealing capability This paper presents a 3-D finite element simulation of a pipe-flange joint to describe the numerical procedure for modeling of tack welds in circumferential joints Sequentially coupled nonlinear transient thermo-mechanical analysis is performed to simulate Metal Inert Gas (MIG) welding Single pass butt weld geometry with single “V” for 100 mm nominal diameter pipe with same sized weld neck type ANSI flange of class no 300 is used Temperature dependent material properties are used and deposition of filler metal is obtained by element birth and death feature The peak temperature of the tack during the butt-welding of the tacked model is concluded a key parameter for numerical prediction of deformations, whereas tack temperature has negligible effect on the residual stresses

A study on a vision sensor system for tracking the I-Butt weld joints

Abstract: In this study, a visual sensor system for weld seam tracking the I-butt weld joints in GMA welding was constructed. The sensor system consists of a CCD camera, a diode laser with a cylindrical lens and a band-pass-filter to overcome the degrading of image due to spatters and arc light. In order to obtain the enhanced image, quantitative relationship between laser intensity and iris opening was investigated. Throughout the repeated experiments, the shutter speed was set at 1/1000 second for minimizing the effect of spatters on the image, and therefore the image without the spatter traces could be obtained. Region of interest was defined from the entire image and gray level of the searched laser stripe was compared to that of weld line. The differences between these gray levels lead to spot the position of weld joint using central difference method. The results showed that, as long as weld line is within ±15° from the longitudinal straight line, the system constructed in this study could track the weld line successfully. Since the processing time is no longer than 0.05 sec, it is expected that the developed method could be adopted to high speed welding such as laser welding.

Consumable electrode type welding method

Abstract: A conventional consumable electrode type welding method has required the reversed operation of a robot manipulator and therefore excessive response time and acceleration/deceleration time, and inability of the feed/ supply of a welding wire to catch up with the melting speed of a welding wire has caused a larger arc length and an instable arc. A welding torch (4) is moved away from a base material (7) by a robot manipulator (9) while a welding wire (1) is being fed/supplied to thereby produce an initial arc with the welding wire (1) separated from the base material (7), whereby it is possible to reduce wasteful time without requiring a reversed operation to shorten a tact time, and stabilize arc at the starting end of welding to effectively reduce a “jerky stop”.

Narrow groove butt welding method for thick steel plate

Abstract: PROBLEM TO BE SOLVED: To provide a welding method that excels in arc stability even in the initial layer (i.e., bottom of a groove) of multi-layer welding and that enables stable penetration to be obtained, in performing narrow groove butt welding for a thick steel plate by a gas shielded arc welding method. SOLUTION: In the narrow groove butt welding method in which multi-layer gas shielded arc welding is performed on a thick steel plate using a welding steel wire composed of a steel wire containing 0.015-0.100 mass% rare earth elements; the gas shielded arc welding of the initial layer is performed under the conditions that a QL value determined by QL=I×E/[S×(G+5×tanθ)]/60 satisfies in the range of 1.5-10.0 and that a QH value determined by QH=[G×S×60×(G+tanθ)/(I×E)]+tanθ satisfies in the range ≥1.0. COPYRIGHT: (C)2007,JPO&INPIT

Device for clamping at least two components, especially aircraft components, in order to join the same by means of a welded seam formed between two edges of the components using friction stir welding

Abstract: The invention relates to a device for clamping at least two components (17, 18), especially aircraft components (17, 18), in order to join said components (17, 18) by means of a welded seam (22) formed between two edges of the components using friction stir welding. Each component (17, 18) is accommodated by several support elements (6-16) while a welding support (3) is disposed below the welded seam (22). Both sides of the welding support (3) are provided with at least one holding mechanism (4, 5) that can be impinged upon by a vacuum so as to clamp the components (17, 18). Said holding mechanisms (4, 5) that can be impinged upon by a vacuum allow the components (17, 18) to be clamped quickly and simply for joining the same using the previously known friction stir welding process. The inventive device can be adapted in an easy and flexible manner to a multitude of components (17, 18) having different geometries and/or dimensions by replacing a small number of parts, particularly the holding mechanisms (4, 5) and/or the welding support (3). One and the same device makes it possible to clamp a multitude of component types, above all components (17, 18) that are curved once and/or twice, for the friction stir welding process. The disclosed device can be used for raw components, e.g. metal sheets or similar, as well as for clamping and welding together complex, prefabricated individual components, e.g. entire fuselage shells or partial shells. Furthermore, the inventive device allows for greater advancing rates during friction stir welding as the dissipation of heat from the seam forming area (19) can be minimized by using low heat conductive materials for the holding mechanisms (4, 5) and/or the base (2).

Welding method for major repairing cathode of large aluminium electrolytic bath

Abstract: A welding method for repairing the cathode of large aluminium electrolyzer used to produce aluminium by electrolyzing includes cutting off the steel rod as cathode outside the position between internal surface of electrolyzer and cathode block, respectively repairing and smoothing the fractured surfaces, moving an electrically conductive connection plate with segment of steel rod in the internal cavity of electrolyzer for shielding magnetic field, convertional build-up welding, moving it out of the electrolyzer, matchying both fractured surfaces of steel rod, and butt welding.

Laser welding process

Abstract: The invention provides a method of making a component from first and second parts which are joined in a welding process wherein a laser beam is transmitted in a direction from a laser source and at least partly into a gap. The gap is made between edges of the component, and to enable a faster laser welding process, the laser has a focus point size which is at least of the size of the gap. To enable better control of the width of the gap, the invention further provides a method and components wherein one part is formed with a neck which extends into a complementary socket of the other part to prepare the parts for the welding process. The invention in particular concerns welding of brass.

Method and apparatus for diagnosing flash-butt weld zone of steel sheet

Abstract: PROBLEM TO BE SOLVED: To provide a method and an apparatus for diagnosing a flash-butt weld zone, which can easily and precisely diagnose a state of a weld zone, when a preceding steel sheet and a succeeding steel sheet are joined by flash-butt welding and then continuously fed into a continuous cold rolling mill for example, employing a flash-butt welder for an uncoiled steel sheet of about 1.0-10 mm in thickness and about 400-2500 mm in width. SOLUTION: In the flash-butt welder for joining the preceding steel sheet and the succeeding steel sheet in a continuous cold processing line, the quality of the weld zone is diagnosed based on a temperature distribution obtained by measuring temperature on the weld zone in the designated width from the weld line as a center, in the state before or after trimming of a bead within 10 seconds after the completion of upsetting. COPYRIGHT: (C)2006,JPO&NCIPI

Hoop with butt-welding joint and its making method and equipment

Abstract: The invention discloses a welding and pulling hooping for forming the beam and pile frame in construction project. The hooping uses the butt joint to replace current lapped hook of the hooping. In order to produce welding and pulling hooping, the method straightens the round steel bar, then bents and cuts off it, and it is welded into closed ring, and finally expands it into product. The mechanical producing line is made up of disk slice frame, straightening device, ringing and cutter, transmitter, ring butt welder, ring expansion puller. The quality is high and the construction is convenient, it can save steel material for 15-25%, upgrades the efficiency for 30 times.