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Showing papers on "Welding published in 2000"


Journal ArticleDOI
TL;DR: In this paper, the authors developed a basic understanding of the evolution of microstructure in the dynamically recrystallized region and to relate it to the deformation process variables of strain, strain rate, and temperature.

726 citations


Journal ArticleDOI
TL;DR: In this paper, the effects of friction-stir welded aluminum alloy 7050 in a T7451 temper to investigate the effects on the microstructure and mechanical properties were investigated.
Abstract: Aluminum alloy 7050 was friction-stir welded (FSW) in a T7451 temper to investigate the effects on the microstructure and mechanical properties. Results are discussed for the as-welded condition (as-FSW) and for a postweld heat-treated condition consisting of 121 °C for 24 hours (as-FSW + T6). Optical microscopy and transmission electron microscopy (TEM) examination of the weld-nugget region show that the FS welding process transforms the initial millimeter-sized pancake-shaped grains in the parent material to fine 1 to 5 µm dynamically recrystallized grains; also, the FS welding process redissolves the strengthening precipitates in the weld-nugget region. In the heat-affected zone (HAZ), the initial grain size is retained, while the size of the strengthening precipitates and of the precipitatefree zone (PFZ) is coarsened by a factor of 5. Tensile specimens tested transverse to the weld show that there is a 25 to 30 pct reduction in the strength level, a 60 pct reduction in the elongation in the as-FSW condition, and that the fracture path is in the HAZ. The postweld heat treatment of 121 °C for 24 hours did not result in an improvement either in the strength or the ductility of the welded material. Comparison of fatigue-crack growth rates (FCGRs) between the parent T7451 material and the as-FSW + T6 condition, at a stress ratio of R = 0.33, shows that the FCG resistance of the weldnugget region is decreased, while the FCG resistance of the HAZ is increased. Differences in FCGRs, however, are substantially reduced at a stress ratio of R = 0.70. Analysis of residual stresses, fatigue-crack closure, and fatigue fracture surfaces suggests that decrease in fatigue crack growth resistance in the weld-nugget region is due to an intergranular failure mechanism; in the HAZ region, residual stresses are more dominant than the microstructure improving the fatigue crack growth resistance.

460 citations


Journal ArticleDOI
Lin Li1
TL;DR: In this paper, a review of the direct applications of high-power diode lasers for materials processing including soldering, surface modification (hardening, cladding, glazing and wetting modifications), welding, scribing, sheet metal bending, marking, engraving, paint stripping, powder sintering, synthesis, brazing and machining is presented.

265 citations


Journal ArticleDOI
TL;DR: In this article, material flow in friction stir welds has been visualised using embedded marker materials and the fidelity of the visualisation technique has also been demonstrated, showing that the friction stir welding process can be roughly described as an in situ extrusion process wherein the tool shoulder, the weld backing plate, and the cold base metal outside the weld zone form an extrusion chamber which moves relative to the workpiece.
Abstract: Material flow in friction stir welds has been visualised using embedded marker materials. The fidelity of the visualisation technique has also been demonstrated. Results from the flow visualisation show that the friction stir welding process can be roughly described as an in situ extrusion process wherein the tool shoulder, the weld backing plate, and the cold base metal outside the weld zone form an ‘extrusion chamber’ which moves relative to the workpiece. Deviation from this description occurs primarily at the top surface of the weld where significant material transport occurs owing to the action of the rotating tool shoulder. The transport caused by the shoulder leads to a small amount of circulation about the longitudinal axis of the weld with material moving primarily from trailing to leading sides at the top of the weld and primarily from leading to trailing near the middle and bottom of the weld.

242 citations


Journal ArticleDOI
TL;DR: In this paper, high vacuum electron beam welding (EBW-HV), CO2 laser beam welding and gas tungsten arc welding (TIG), as well as optical microscope (OM) observation and microhardness measuring of 0.5 mm thick sheets of commercial purity titanium (C.P. Ti) have been studied via EBW, HV, LBW and TIG.
Abstract: Microstructures, properties and technical parameters of welding specimen of 0.5 mm thick sheets of commercial purity titanium (C.P. Ti) have been studied via high vacuum electron beam welding (EBW-HV), CO2 laser beam welding (LBW) and gas tungsten arc welding (TIG), as well as optical microscope (OM) observation and microhardness measuring. The results indicate that the EBW is more suitable for C.P. Ti sheets welding, and the welding seam without defects can be obtained. The tensile strength and microhardness of joints are corresponding to matrix structure. The full-penetration butt welds are obtained by TIG, but they have many defects such as wide weld-seam, big deformation and coarse grains. The LBW has many advantages such as the narrowest weld-seam, the least deformation and the finest grains. The fine grains are good for properties of weld seam, but the LBW should be studied again for the reasons of unstable welding technologies and strict condition.

224 citations


Journal ArticleDOI
TL;DR: In this paper, the authors evaluated the use of activated flux TIG (ATIG) welding for the austenitic stainless steels with fluxes of only one major component and found that even the very simple flux that was used can greatly increase the penetration of the weld bead.

205 citations


Journal ArticleDOI
TL;DR: In this article, analytical and numerical models of linear friction welding of Ti6Al4V (numbers indicate wt%) are established to predict temperature rises during the initial phase of the process, which is of importance in forming sound welds.
Abstract: Analytical and numerical models of linear friction welding of Ti6Al4V (numbers indicate wt.%) are established to predict temperature rises during the initial phase of the process, which is of importance in forming sound welds. Both model predictions are compared with experimental data. The numerical model is used to explain the physical conditions that control the ability to weld under certain process conditions. The effects of the exothermic reaction of titanium with oxygen during the extrusion phase are also discussed.

188 citations


Journal ArticleDOI
TL;DR: In this article, the weld fusion zones and the interfaces with the base materials were characterised in detail using light and transmission electron microscopy, showing that the stainless steel weld metals solidified dendritically, while the 16-8-2 (16%Cr-8%Ni-2%Mo) weld metal showed a predominantly cellular substructure.
Abstract: For joining type 316LN austenitic stainless steel to modified 9Cr–1Mo steel for power plant application, a trimetallic configuration using an insert piece (such as alloy 800) of intermediate thermal coefficient of expansion (CTE) has been sometimes suggested for bridging the wide gap in CTE between the two steels. Two joints are thus involved and this paper is concerned with the weld between 316LN and alloy 800. These welds were produced using three types of filler materials: austenitic stainless steels corresponding to 316, 16Cr–8Ni–2Mo, and the nickel-base Inconel 182 1 . The weld fusion zones and the interfaces with the base materials were characterised in detail using light and transmission electron microscopy. The 316 and Inconel 182 weld metals solidified dendritically, while the 16–8–2 (16%Cr–8%Ni–2%Mo) weld metal showed a predominantly cellular substructure. The Inconel weld metal contained a large number of inclusions when deposited from flux-coated electrodes, but was relatively inclusion-free under inert gas-shielded welding. Long-term elevated-temperature aging of the weld metals resulted in embrittling sigma phase precipitation in the austenitic stainless steel weld metals, but the nickel-base welds showed no visible precipitation, demonstrating their superior metallurgical stability for high-temperature service.

186 citations


Journal ArticleDOI
TL;DR: The most dominant mechanism for increased penetration is considered to be arc constriction rather than a change in the surface tension of the molten pool as mentioned in this paper, which is the most common mechanism used in tungsten inert gas welding.
Abstract: Mechanisms by which active fluxes increase the penetration of conventional tungsten inert gas (TIG) welds (so called A-TIG welds) are reviewed. The most dominant mechanism for increased penetration is considered to be arc constriction rather than a change in the surface tension of the molten pool. An experimental programme of work was carried out using A-TIG flux in combination with a number of welding processes. The plasma process was investigated as it gives greater penetration than conventional TIG welding by increasing current density. The CO2 laser and electron beam processes which do not rely on a current carrying arc as the heat source for welding were also investigated. Macrosections taken from the welds made by these processes showed that the A-TIG flux was only effective when the weld pool was produced by an arc or plasma. Where there was no arc or plasma present, the flux had little effect.

183 citations


Journal ArticleDOI
TL;DR: In this article, a trimetallic joint involving modified 9Cr-1Mo steel and 316LN austenitic stainless steel as the base materials and Alloy 800 as the intermediate piece was investigated.

150 citations


Patent
24 Nov 2000
TL;DR: In this article, the voltage and current conditions of the welding arc are instantly transferred within the visual range of the helmet wearing operator by the use of lights, illuminated bar graphs, light projections, illuminated see-through displays, or the like, located in proximity to the helmet viewing window.
Abstract: Apparatus for monitoring manual arc welding procedures for providing to the welder real-time monitoring of the welding characteristics to achieve optimum welds. The voltage and current conditions of the welding arc are instantly transferred within the visual range of the helmet wearing operator by the use of lights, illuminated bar graphs, light projections, illuminated see-through displays, or the like, located in proximity to the helmet viewing window wherein, through such monitoring, the operator is constantly aware of the arc conditions during welding.

Journal ArticleDOI
TL;DR: In this paper, the interrelationship between keyhole and plasma behavior was examined, and it was revealed that the keyhole fluctuates frequently and changes its size and shape, corresponding to the intermittent bubble formation.
Abstract: Laser welding can produce a deeply penetrated bead at high speed. However, in high power cw CO2 laser welding, the characteristic porosity is easily formed in the weld metal, but its formation mechanism has not been well understood. Therefore, the authors have conducted systematic studies of the elucidation of porosity formation mechanism and the development of preventive remedies. They have revealed that many bubbles are formed, mainly from the bottom tip of the keyhole by intense evaporation of the metal. It has also been revealed that the keyhole fluctuates frequently and changes its size and shape, corresponding to the intermittent bubble formation. The majority of bubbles are trapped at the solidifying front in the rear part of the molten pool. However, there are few reports that deal with the simultaneous observation of keyhole and plasma dynamic behavior as well as the formation of bubbles and porosity. In this study, therefore, the interrelationship between keyhole and plasma behavior was examined...

Journal ArticleDOI
TL;DR: In this article, a tool set, a simple stand alone hydraulic bulging fixture, was developed to expand the tubes under bi-axial loading conditions, along with analytical methods and finite element simulation, for tubular workpieces.

Patent
11 Aug 2000
TL;DR: In this article, a welding unit consisting of a welding device and a protection unit is described, in particular a protective screen for an operator or a welder. And the welding device is at least composed of an electrical source, a welding torch, and a control unit.
Abstract: This invention relates to a welding unit comprising a welding device (1) and a protection unit (28), in particular a protective screen (29) for an operator or a welder. The protection unit (28) has an electrically operable, commandable- and/or controllable visor (31) with a control device (32). The welding device (1) or the welding unit is at least composed of an electrical source (2), a welding torch (10) and a control unit. The protection unit (28) has a transmitter and/or a receiver (33), which is connected to the control device (32). The transmitter and/or receiver (33) is connected to the welding unit or welding device (1) or the welding torch (10) via a connecting cable (35) or by wireless means. Darkening of the protective visor (31) occurs after the control unit or the welding torch sends out a signal to the transmitter and/or receiver (33) which is relayed to the control device (32) after activation of a start switch (27) disposed on a welding torch (10) or on the welding device (1) or by virtue of a start command.

Journal ArticleDOI
TL;DR: In this paper, the influence of the interfacial reaction between the matrix and reinforcement has on the fracture behavior of an aluminium alloy reinforced with SiC particles when it is arc welded.

Journal ArticleDOI
TL;DR: In this paper, a model of keyhole formation due to sideways melt displacement is proposed, which allows us to study the keyhole geometry as a function of the main operating parameters such as welding speed, laser incident intensity, or sample material.
Abstract: A model, which generalizes the concept of keyhole formation due to sideways melt displacement, allows us to study the keyhole geometry as a function of the main operating parameters such as welding speed, laser incident intensity, or sample material. It is based on a drilling velocity whose combination with the welding velocity causes the inclination of the front keyhole wall. This front inclination is shown to be stationary and stable all along the front side. The penetration depth results from the product of this drilling velocity and a characteristic time defined as the beam diameter divided by the welding speed. By using a ray-tracing procedure, the dynamics and the complete keyhole geometry can be determined by taking into account the possible multiple reflections inside the keyhole and a simplified description of the closure process of the rear keyhole wall. It is shown that for usual conditions of laser irradiation, this rear keyhole wall cannot be stationary all along its surface and only an adequate laser intensity distribution can make it stationary. The interest of elongated focal spots or twin spots is then demonstrated. At high welding velocity the front wall is inclined and is composed of several layers resulting from the successive reflections. The rear wall fluctuates around an apparent equilibrium, and corresponding fluctuations occur at maximum penetration depth. At low welding speeds, the keyhole appears to be more symmetric as a consequence of the multiple reflections between the rear and the front keyhole walls.

PatentDOI
TL;DR: In this paper, an improved method and apparatus for joining aluminum alloy panels (29, 29) was presented, where a stringer panel overlaps a skin panel and a friction stir weld pin tool penetrates through one panel and at least partially into another panel.
Abstract: The present invention provides an improved method and apparatus for joining aluminum alloy panels (29, 29)(e.g. 2090-T83 aluminum lithium alloy). The method preliminarily positions two panels (28, 29) next to each other so that a stringer panel (28) overlaps a skin panel (29). A friction stir weld pin tool (10) penetrates through one panel (28) and at least partially into another panel (29). The panel material around the pin tool (10) is frictionally heated.

Journal ArticleDOI
TL;DR: In this paper, the use of fuzzy logic in the Taguchi method to optimise the submerged arc welding process with multiple performance characteristics is reported, including arc current, arc voltage, welding speed, electrode protrusion, and preheat temperature.
Abstract: The use of fuzzy logic in the Taguchi method to optimise the submerged arc welding process with multiple performance characteristics is reported in this paper. An orthogonal array, the signal-to-noise ratio, multiresponse performance index, and analysis of variance are employed to study the performance characteristics in the submerged arc welding process. The process parameters, namely arc current, arc voltage, welding speed, electrode protrusion, and preheat temperature are optimised with considerations of the performance characteristics, including deposition rate and dilution. Experimental results are provided to confirm the effectiveness of this approach.

Journal ArticleDOI
TL;DR: In this paper, a newly contrived clamping method along the weld line of the tailor-welded blank during forming is proposed, which reduced the maximum strain along the welding line by approximately one-fifth in the part examined.

Journal ArticleDOI
TL;DR: In this article, the results of GTA-welding of dissimilar aluminium alloys of the series 5xxx and 6xxx for plate thickness of 1.5, 3 and 5mm are presented.

Patent
03 May 2000
TL;DR: In this paper, an improved laser welded work piece, such as an automotive body panel, and a system and method for the manufacture thereof are described, as well as an improved system for manufacturing the welded piece including a laser welder and a laser weld inspection device and system.
Abstract: The present invention relates generally to an improved laser welded work piece, such as an automotive body panel, and a system and method for the manufacture thereof. The invention is also directed to an improved system for manufacturing the welded work piece including an improved laser welder and a laser weld inspection device and system.

Journal Article
TL;DR: In this article, mathematical models were developed to relate the process parameters and the weld bead quality parameters in submerged arc welding of pipes, and the optimization of weld bead volume was carried out using the optimization module available in the MATLAB version 4.2b software package.
Abstract: As a part of a study and analysis on the effects of process parameters on weld bead volume in submerged arc welding (SAW) of pipes, mathematical models were developed to relate the process parameters and the weld bead quality parameters. Further, the optimization of weld bead volume was carried out using the optimization module available in the MATLAB version 4.2b software package. The mathematical models thus developed for optimization are also helpful in predicting the weld bead quality parameters and in setting process parameters at optimum values to achieve the desirable weld bead quality at a relatively low cost with a high degree of repeatability and increased production rate. Total volume of the weld bead, an important bead parameter, was optimized (minimized), keeping the dimensions of the other important bead parameters as constraints, to obtain sound and superior quality welded pipes. Sensitivity analysis was also carried out to predict the direct and few interaction effects of important bead parameters on the total volume of the weld bead, and the results are presented in graphical form. The results of the sensitivity analysis are very useful in understanding the interdependence of various weld bead quality parameters in controlling the volume of the weld bead, to improve weld quality, to increase productivity with the available welding facilities and to minimize the total welding cost.

Patent
06 Nov 2000
TL;DR: In this paper, a welding device (1) or an electricity supply (2) comprising a control device (4) which is preferably formed by a microprocessor control device having a memory unit, a power component (3), in particular an inverted electricity supply and additional components such as a welding torch (10), a wire feed device (11) etc.
Abstract: The invention relates to a welding device (1) or an electricity supply (2) comprising a control device (4) which is preferably formed by a microprocessor control device having a memory unit, a power component (3), in particular an inverted electricity supply and additional components such as a welding torch (10), a wire feed device (11) etc, which are connected by an appropriate interface to said welding unit (1) or the electricity supply (2). An additional module (27) for recovering a biometric body characteristic of a person, such as for example an electronic finger print, speech recognition, iris recognition, facial feature recognition, dynamic handwriting recognition or transponder recognition is connected to the control device (4) or welding device (1) or said electrical supply (4).

Journal ArticleDOI
TL;DR: In this article, material flow in two friction stir welds produced using different welding parameters was visualized using embedded marker materials and the fidelity of the visualization technique was demonstrated. But the details of the weld formation mechanism have been the subject of some debate.
Abstract: Friction Stir Welding (FSW) is a relatively new process for joining of metals. The process was invented in 1992 at The Welding Institute, Cambridge, UK. FSW is particularly well suited to use in highly alloyed aluminum because it is a solid state process; therefore, no undesirable, brittle, low-melting eutectic phases are formed during the welding process. The microstructure of a typical friction stir weld is that of a wrought product. The details of the weld formation mechanism have been the subject of some debate. Previous work on elucidation of flow patterns in friction stir welds indicated that the process may be described as an in-situ extrusion. Material flow in two friction stir welds produced using different welding parameters was visualized using embedded marker materials and the fidelity of the visualization technique was demonstrated. Flow of material in the friction stir welds was observed to depend strongly on the temperature of the weld. In this paper, welding temperature measurements are combined with tensile test data to further promote understanding of the process in 2XXX, 5XXX, 6XXX, and 7XXX series aluminum alloys. Weld parameters (spindle rotation rate and welding speed) and time-temperature histories are correlated with the global and local tensile properties, and microstructure of the resulting welds.

Patent
15 Jun 2000
TL;DR: In this paper, information pertaining to characteristics of metal welding electrode wire and which characteristics are useful in connection with adjusting welding parameters in an arc welding process and selecting between operating modes in a welding system are encoded on welding wire and/or on other memory components such as bar code labels and tags, RFID cards, IC cards, and Touch Memory buttons.
Abstract: Information pertaining to characteristics of metal welding electrode wire and which characteristics are useful in connection with adjusting welding parameters in an arc welding process and/or selecting between operating modes in a welding system are encoded on welding wire and/or on other memory components such as bar code labels and tags, RFID cards and tags, IC cards, and Touch Memory buttons, and the memory device is scanned prior to and/or at the point of use of the welding wire for enabling tracking of product distribution, manual and/or automatic selection of an operating mode for the welding system, manual and/or automatic adjustment of welding parameters in a given operating mode, consumables inventory, and the like.

Journal ArticleDOI
TL;DR: In this paper, a comprehensive experimental investigation of the resistance welding of carbon-fibre and reinforced polyetherimide (PEI) laminates is presented, where lap-shear and double-cantilever-beam specimens were resistance welded by using fabric and unidirectional heating elements.

Journal ArticleDOI
TL;DR: In this paper, a coupled thermal-electrical-mechanical analysis was employed to predict the nugget development during resistance spot welding (RSW) of Al-alloys.
Abstract: This paper develops a model to predict the nugget development during resistance spot welding (RSW) of Al-alloys. The model employs a coupled thermal-electrical-mechanical analysis and accounts for phase change and convective transport in the weld pool. The contact area and the pressure distribution are determined from a coupled thermal ? mechanical model. The model calculates time varying interface pressure. The knowledge of interface pressure allows for accurate prediction of interfacial heat generation. Temperature-dependent thermal-electrical-mechanical properties are used. The predicted nugget shape and size agree well with experimental data. The proposed model can be applied to predict the effects of the welding parameters and the electrode shapes on the nugget development.

Patent
26 Oct 2000
TL;DR: In this article, a friction stir welding machine with a table for supporting parts to be welded and a frame extending over the table is described, where a first drive is supported by a first element of the frame and is operatively connected to a spindle having a tool, and the first drive disengages from the spindle after the tool contacts the material.
Abstract: A friction stir welding machine includes a table for supporting parts to be welded and a frame extending over the table. A first drive is supported by a first element of the frame and is operatively connected to a spindle having a tool. The first drive moves the tool in a first direction, and the first drive disengages from the spindle after the tool contacts the material. A second drive is supported by a second element of the frame and is operatively connected to the spindle for moving the tool into the parts at a joint, thereby initiating friction stir welding process. The friction stir welding machine has a pair of rollers mounted in a roller support with an axis of rotation substantially perpendicular to an axis of rotation of the tool. The rollers contact a surface of the material in response to the tool penetrating the material to a desired depth. The roller support is pivotally mounted to the spindle and has a pivot axis substantially perpendicular to both an axis of rotation of the rollers and the axis of rotation of the tool. The work supporting table of the friction stir welding machine has a vacuum hold down system for securing the parts to the table.

Patent
16 Mar 2000
TL;DR: An electric arc welding apparatus for depositing molten metal from an advancing welding wire into a weld puddle in an open root between two juxtapositioned plates where the root extends in a welding path and is formed by converging walls terminating in generally parallel walls spaced to define a gap as discussed by the authors.
Abstract: An electric arc welding apparatus for depositing molten metal from an advancing welding wire into a weld puddle in an open root between two juxtapositioned plates where the root extends in a welding path and is formed by converging walls terminating in generally parallel walls spaced to define a gap, which apparatus comprises a contact holder with a wire outlet, a switching power supply directing welding current to the wire as the wire passes from the outlet toward the open root, with the advancing wire defining an electrode stick out between the contact holder and the weld puddle, a circuit for sensing the length of the stick out, and control means for adjusting the welding current as a function of the sensed stick out length.

Journal ArticleDOI
TL;DR: In this paper, the effects of CO2 and Nd-YAG laser beam processing parameters and the properties of the most common wrought aluminium alloys on the characteristics of welded joints are discussed.
Abstract: Laser beam welding is now a common manufacturing method for a wide range of steel products from automobiles to razor blades. However, the process has only recently been approved for critical applications involving aluminium alloys, notably in the aerospace and automotive industries. The properties of aluminium alloys influence the interaction between the beam and the material to a far greater extent than for steels. The challenge of developing industrial welding procedures has therefore been considerable. The present review describes the effects of CO2 and Nd–YAG laser beam processing parameters and the properties of the most common wrought aluminium alloys on the characteristics of welded joints. Porosity, solidification cracking, and poor weld bead geometry are shown to be the most frequently encountered imperfections. These can be eliminated through the use of appropriate filler materials, process gases, material preparation, and in some instances, adaptive control systems. Very little work has...