Showing papers on "Gas metal arc welding published in 2007"
TL;DR: In this paper, a unified comprehensive model was developed to simulate the transport phenomena occurring during the gas metal arc welding process, where an interactive coupling between arc plasma; melting of the electrode; droplet formation, detachment, transfer, and impingement onto the workpiece; and weld pool dynamics all were considered.
287 citations
TL;DR: In this article, the effects of various welding parameters on welding penetration in Erdemir 6842 steel having 2.5mm thickness welded by robotic gas metal arc welding were investigated.
182 citations
TL;DR: In this article, the influence of pulsed current TIG welding parameters on tensile properties of AA 6061 aluminium alloy weldments was investigated. And the results showed that pulsed currents can improve the mechanical properties of the welds compared to those of continuous current welds.
165 citations
TL;DR: In this paper, the microstructure and properties of aluminium-zinc coated steel lap joints made by a modified metal inert gas CMT welding-brazing process was investigated, and it was found that the nature and the thickness of the high-hardness intermetallic compound layer formed at the interface between the steel and the weld metal during the welding process varied with the heat inputs.
147 citations
TL;DR: In this article, an experimental study of shielding gases aimed at analysing arc stability and transfer modes, as well as, fume formation, having in view the achievement of a better working environment for welders.
112 citations
TL;DR: In this paper, the stability condition of a hybrid laser CO 2 -GMAW welding process was investigated by analyzing the influence of several process parameters, such as the filler metal transfer mode on the stability of the whole process.
102 citations
TL;DR: In this paper, the results of gas metal arc welding plasma operated in pure argon and in a mixture of CO2 at a dc current of 326?A. The results show a reduction of the plasma conductivity and transfer from spray arc to globular arc operation with increasing CO2 concentration.
Abstract: We report on investigations of gas metal arc welding plasma operated in pure argon and in a mixture of argon and CO2 at a dc current of 326?A. The spatially resolved electron densities and temperatures were directly obtained by measuring the Stark widths of the Ar?I 695.5?nm and Fe?I 538.3?nm spectral lines.Our experimental results show a reduction of the plasma conductivity and transfer from spray arc to globular arc operation with increasing CO2 concentration. Although the electron density ne increases while approaching the core of the plasma in the spray-arc mode, a drop in the electron temperature Te is observed. Moreover, the maximum Te that we measure is about 13?000?K. Our experimental results differ from the Haidar model where Te is always maximum on the arc axis and its values exceed 20?000?K. These discrepancies can be explained as a result of underestimation of the amount of metal vapours in the plasma core and of the assumption of local thermal equilibrium plasma in the model.
101 citations
TL;DR: In this article, the minimum net energy input for proper operative and metallurgical weldabilities is studied using two different welding modes: the melt-in or conduction mode and the keyhole mode.
98 citations
TL;DR: In this article, a novel technique based on artificial neural networks (ANNs) for prediction of gas metal arc welding parameters was presented, where the ANN controller was trained with the extended delta-bar-delta learning algorithm.
94 citations
TL;DR: In this article, the effect of welding current on the quality of weld joint and obviously on tensile shear and tensile-peel strengths of galvanized chromate steel sheets having 1.2mm thickness in electrical resistance spot welding was investigated.
89 citations
TL;DR: In this paper, the effects of interwire distance and Ar-CO2 gas mixture ratio on an abnormal arc voltage and arc interruption were investigated in tandem pulsed gas metal arc welding, where the occurrence of arc interruption by the electromagnetic interaction between the two adjacent arcs becomes a problem.
Abstract: In the tandem pulsed gas metal arc welding, the occurrence of arc interruption by the electromagnetic interaction between the two adjacent arcs becomes a problem. In order to clarify this problem, effects of interwire distance and Ar–CO2 gas mixture ratio on an abnormal arc voltage and arc interruption are investigated. The abnormal arc voltage and the arc interruption frequently occur with pulse peak currents which are supplied alternately to two wires. In addition, both phenomena occur in trailing arc which is located on molten pool at base current duration remarkably. There is most number of abnormal arc voltage and arc interruption times in trailing when the interwire distance is 10 mm, because a deflected length of trailing arc by the electromagnetic interaction becomes the longest. Moreover, the CO2 mixture ratio in shielded gas affects the occurrence of abnormal arc voltage and arc interruption. The abnormal arc voltage and arc interruption do not occur when CO2 gas mixture ratio is equal t...
TL;DR: In this article, the effect of pulse parameters has been studied by considering their hypothetically proposed summarised influence defined by a dimensionless factor ϕ ǫ = [( I b / I p ) ft b ], mean current and arc voltage.
TL;DR: In this article, a detailed experiment of CO2 laser-Tungsten inert gas (TIG) hybrid welding with different shielding gas methods was carried out on the 316L stainless plate, and the results demonstrate that full weld penetration denoting efficient synergetic effect only can be obtained under the appropriate shielding gas parameters.
25 Jun 2007-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, the effect of pulsed current and post weld aging treatment on tensile properties of argon arc welded AA7075 aluminium alloy has been revealed, where four different welding techniques have been used to fabricate the joints and they are: (i) continuous current GTAW (CCGTAW), (ii) pulsed currents GTAW, (iii) continuous currents GMAW (CGMAW), and (iv) pulses current GMAWS (PCGMAWS) processes.
Abstract: This paper reveals the effect of pulsed current and post weld aging treatment on tensile properties of argon arc welded AA7075 aluminium alloy. This alloy has gathered wide acceptance in the fabrication of light weight structures requiring high strength-to-weight ratio, such as transportable bridge girders, military vehicles, road tankers and railway transport systems. The preferred welding processes of high strength aluminium alloy are frequently gas tungsten arc welding (GTAW) process and gas metal arc welding (GMAW) process due to their comparatively easier applicability and better economy. Weld fusion zones typically exhibit coarse columnar grains because of the prevailing thermal conditions during weld metal solidification. This often results inferior weld mechanical properties and poor resistance to hot cracking. In this investigation, an attempt has been made to refine the fusion zone grains by applying pulsed current welding technique. Four different welding techniques have been used to fabricate the joints and they are: (i) continuous current GTAW (CCGTAW), (ii) pulsed current GTAW (PCGTAW), (iii) continuous current GMAW (CCGMAW) and (iv) pulsed current GMAW (PCGMAW) processes. As welded joint strength is much lower than the base metal strength and hence, a simple aging treatment has been given to improve the tensile strength of the joints. Current pulsing leads to relatively finer and more equi-axed grain structure in GTA and GMA welds. In contrast, conventional continuous current welding resulted in predominantly columnar grain structures. Post weld aging treatment is accompanied by an increase in tensile strength and tensile ductility.
25 Apr 2007-Metallurgical and Materials Transactions B-process Metallurgy and Materials Processing Science
TL;DR: In this article, three-dimensional numerical simulations were conducted to study temperature distributions and fluid flows during formation of humped beads in high speed gas metal arc welding (GMAW).
Abstract: Three-dimensional numerical simulations were conducted to study temperature distributions and fluid flows during formation of humped beads in high speed gas metal arc welding (GMAW). Based on simulation and experimental results, the physical mechanisms associated with humping phenomenon were investigated and two conditions responsible for hump formation were identified: the formation of thin liquid channel induced by surface tension pinching force and premature solidification of the melt in the thin channel that divides the weld pool into a front and rear portion. A strong backward fluid flow that produced an accumulation of melt at the rear of the weld pool increased the size of humps. Although surface tension was shown to be important in hump formation, Marangoni flow induced by negative surface tension gradients was not significant for hump formation. The simulation results clarified the fluid flow associated with two different hump shapes. Experimental welds without bead humping were made at a lower travel speed and were also simulated to illustrate the differences in heat and fluid flow from humped beads.
TL;DR: In this paper, a wide study on the hybrid CO2 LASER-MIG welding and investigates the influence of the shielding gas both on the stability of the process and on the dimensional characteristics of the weld bead.
TL;DR: In this paper, a double-electrode gas metal arc welding (DE-GMAW) was developed to increase the melting current while the base metal current can still be controlled at a desired level.
Abstract: Gas metal arc welding (GMAW) is the most widely used process for metal joining because of its high productivity and good quality, but analysis shows that the fundamental characteristic restricts conventional GMAW from further increasing the welding productivity. A novel GMAW process, refereed to as double-electrode GMAW or DE-GMAW, thus has been developed to make it possible to increase the melting current while the base metal current can still be controlled at a desired level. This fundamental change provides an effective method to allow manufacturers to use high melting currents to achieve high melting speed and low base metal heat input. A series of experiments have been conducted to uncover the basic characteristics of this novel process. Results obtained from analyses of high-speed image sequences and recorded current signals suggest that DE-GMAW can lower the critical current for achieving the desired spray transfer, shift the droplet trajectory, reduce the diameter of the droplet, and increase the speed and (generation) rate of the droplets.
TL;DR: In this article, the effect of active flux on the depth/width ratio in AZ31B magnesium alloy was investigated and the microstructure and mechanical properties of the tungsten inert gas (TIG) welding seam were studied.
Abstract: Five single oxide fluxes—MgO, CaO, TiO2, MnO2, and Cr2O3—were used to investigate the effect of active flux on the depth/width ratio in AZ31B magnesium alloy. The microstructure and mechanical property of the tungsten inert gas (TIG) welding seam were studied. The oxygen content in the weld seam and the arc images during the TIG welding process were analyzed. A series of emission spectroscopy of weld arc for TIG welding for magnesium with and without flux were developed. The results showed that for the five single oxide fluxes, all can increase the weld penetration effectively and grain size in the weld seam of alternating current tungsten inert gas (ACTIG) welding of the Mg alloy. The oxygen content of the welds made without flux is not very different from those produced with oxide fluxes not considering trapped oxide. However, welds that have the best penetration have a relatively higher oxygen content among those produced with flux. It was found that the arc images with the oxide fluxes were only the enlarged form of the arc images without flux; the arc constriction was not observed. The detection of arc spectroscopy showed that the metal elements in the oxides exist as the neutral atom or the first cation in the weld arc. This finding would influence the arc properties. When TIG simulation was carried out on a plate with flux applied only on one side, the arc image video showed an asymmetric arc, which deviated toward the flux free side. The thermal stability, the dissociation energy, and the electrical conductivity of oxide should be considered when studying the mechanism for increased TIG flux weld penetration.
TL;DR: The effects of activating fluxes on welding arc were investigated in this article, where a special set of water-cooling system and stainless steel were used as parent material and high-speed camera system and oscillograph were used for capturing instantaneous arc shape and arc voltage respectively.
TL;DR: In this paper, a hollow axis motor driven high speed rotation arc system for narrow gap welding (NGW) was developed and some welding experiments were carried out to investigate the characteristics of welding wire melting and weld formation for this new process.
Abstract: The present paper develops a hollow axis motor driven high speed rotation arc system for narrow gap welding (NGW), and introduces the features of this system. Some welding experiments were then carried out to investigate the characteristics of welding wire melting and weld formation for this new process. Experimental results show that the melting rate of wire increases and the residual melting ball diameter of wire tip decreases respectively with an increase in rotation speed, and this melting rate is higher in pulsed welding and NGW respectively than in dc and flat plate welding. Furthermore, the arc rotation can obviously improve the penetration into NGW groove sidewalls and bead shape, and thus the system has been used to weld practical NGW joints successfully.
TL;DR: In this paper, an analysis of the arc energy influence on the weld bead geometry allows determining the mechanisms that occur during ATIG welding with fluorides, and it seems that fluoride activating effect could depend on the fluoride lattice energy and/or the ionic radius of the element.
Abstract: The mechanisms of the inorganic powders, named activating flux and used in ATIG welding process, are not well identified. Oxides and fluorides usually compose activating fluxes. The present paper studies the fluoride activating effect. The analysis of the arc energy influence on the weld bead geometry allows determining the mechanisms that occur during ATIG welding with fluorides. It seems that fluoride activating effect could depends on the fluoride lattice energy and/or the ionic radius of the element. Fluorides act on the arc physics only. An arc energy densification is observed. Furthermore, an arc temperature increase, find out with optical emission spectrometry, characterises the fluoride activating effect. The fluorides do not affect the weld bead surface chemistry. Marangoni convection movements stay centrifugal as in TIG welding and do not favour a penetration increase.
TL;DR: In this paper, different welding techniques were used to evaluate the mechanical performance of weldments of HY-80 steel, and the effects of welding methods on weld metal microstructure and mechanical properties including weld metal tensile strength and Charpy V-notch impact toughness over the temperature range −20 to 20°C were investigated.
TL;DR: A neural network based on the generalized delta rule algorithm was adapted to control the process of GMAW, such as welding speed, arc voltage and wire feeding speed, and the width and depth of the weld joint have been selected as neurons in the input layer of the neural-network algorithm.
Abstract: Welding has been widely used as a process to join metallic parts. But because of hazardous working conditions, workers tend to avoid this task. Techniques to achieve the automation are the recognition of joint line and process control. A CCD (charge coupled device) camera with a laser stripe was applied to enhance the automatic weld seam tracking in GMAW (gas metal arc welding). The adaptive Hough transformation having an on-line processing ability was used to extract laser stripes and to obtain specific weld points. The three-dimensional information obtained from the vision system made it possible to generate the weld torch path and to obtain information such as the width and depth of the weld line. In this study, a neural network based on the generalized delta rule algorithm was adapted to control the process of GMAW, such as welding speed, arc voltage and wire feeding speed. The width and depth of the weld joint have been selected as neurons in the input layer of the neural-network algorithm. The input variables, the width and depth of the weld joint, are determined by image information. The voltage, weld speed and wire feed rate are represented as the neurons in the output layer. The results of the neural-network learning applied to the welding are as follows: learning ratio 0.5, momentum ratio 0.7, the number of hidden layers 2 and the number of hidden units 8. They have significant influence on the weld quality.
09 Jun 2007
TL;DR: In this paper, the relationship of nugget diameter and welding current was investigated, and hardness distribution along welding zone was also investigated, the results indicated that increasing welding current gave large diameter.
Abstract: In this study, austenitic stainless steel type 304 were welded by resistance spot welding. The relationship of nugget diameter and welding current was investigated. Hardness distribution along welding zone was also investigated. The results indicated that increasing welding current gave large nugget diameter. The welding current did not much affected the hardness distribution.
TL;DR: In this paper, the transient complex heat transfer and fluid flow in molten metal and arc plasma during the gas metal arc welding process was analyzed and the model predicts the formation, growth, detachment, and transfer of droplets from the tip of a continuously fed electrode under the influences of several competing forces including gravity, electromagnetic force, arc pressure, plasma shear stress, and surface tension.
Abstract: This article analyzes the transient complex heat transfer and fluid flow in molten metal and arc plasma during the gas metal arc welding process. The model predicts the formation, growth, detachment, and transfer of droplets from the tip of a continuously fed electrode under the influences of several competing forces including gravity, electromagnetic force, arc pressure, plasma shear stress, and surface tension. Simulations were conducted for five different current levels to study the effects of current on the distributions of temperature, velocity, pressure, and current density in the droplet and/or the arc plasma. Agreement between the simulated results and published experimental data was obtained.
TL;DR: A series of experiments examining the effects of welded boundaries on the localised blast load response of mild steel plates is presented in this paper, where two types of welding are examined, TIG and MIG welding.
TL;DR: In this article, the effect of the shielding gas concentration on the weld shape was studied for the moving bead on plate TIG welding of SUS304 stainless steel under He-O2 mixed shielding.
Abstract: The effect of the shielding gas concentration on the weld shape was studied for the moving bead on plate TIG welding of SUS304 stainless steel under He–O2 mixed shielding. The small addition of oxygen to the helium base shielding gas can precisely control the oxygen content in a liquid pool and the weld shape. Oxygen is a surface active element for stainless steel. When the oxygen content in the liquid pool is above the critical value of ∼ 70 ppm, the weld shape suddenly changes from a wide shallow type to a deep narrow one due to the change in the Marangoni convection from the outward to inward direction on the liquid pool surface. Weld shape variations influenced by the welding parameters including welding speed, welding current and electrode tip work distance under pure He and He–0.4%O2 mixed gas shielding were systematically investigated. The investigation results showed that the final shape of the TIG weld depends to a large extent on the pattern and magnitude of the Marangoni convection on t...
TL;DR: In this paper, hot cracking was observed to propagate from the heat affected zone (HAZ) under the welding bead into the weld metal right after a welding bead was deposited on the thin plate.
Abstract: Plates of 3–5 mm in thickness were extracted from an AZ91D ingot and then butt joints of the plates were produced using tungsten inert gas (TIG) welding method. The TIG arc was also used to deposit welding beads on some of the thin plates. No cracking was found in the butt joints. However, hot cracking was always observed to propagate from the heat affected zone (HAZ) under the welding bead into the weld metal right after a welding bead was deposited on the thin plate. Metallographic and fractographic evidence was obtained to show that the hot cracking is 'liquation cracking' in the partially melted HAZ under the high thermal stresses. In the butt joints, the weld metal has the finest grains, highest strength and best ductility, and the HAZ was found to be the 'weakest link'.
TL;DR: In this article, a procedure for combined laser pre-treating and laser welding of the nitrided samples was presented, aimed at minimising the negative effect of the laser beam on the structural integrity of the base and welded material.
Abstract: A research work is described on the development of defects in laser repair welding of a surface-treated tool steel. Repair welding tests were carried out on plasma-nitrided and on chrome-plated type 1.2738 steel plates. Welding defects in the chrome-plated samples were mainly due to chrome and oxygen overalloying of the weld metal, leading to extensive hot cracking. Cracks of the surface chrome deposit in the HAZ due to welding stresses were also detected. In the nitrided samples, welding resulted in the copious formation of gas pores due to nitrogen release during weld metal solidification. A procedure for combined laser pre-treating and laser welding of the nitrided samples was thus presented. The procedure is aimed at minimising the negative effect of the laser beam on the structural integrity of the base and welded material. The results of the microstructural analyses revealed that a significant reduction in defects could be achieved by the proposed method in the nitrided samples.
TL;DR: In this paper, the energy source properties of gas tungsten arc (GTA) strongly depend on the physical property of arc plasma, and the effect of metal vapour on the characteristics of heat flux into a base metal is still not clear.
Abstract: The energy source characteristics of gas tungsten arc (GTA) strongly depend on the physical property of arc plasma. In welding processes, it has been experimentally confirmed that metal vapour evaporated from a high temperature weld pool drastically changes the property of arc plasma and decreases its temperature. However, the effect of metal vapour on the characteristics of heat flux into a base metal is still not clear owing to the difficulty in experimental studies of arc plasma. In the present paper, the energy source property of helium GTA mixed with metal vapour was numerically analysed. It was found that the intense radiation generated from dense metal vapour decreases heat flux into a base metal and contracts the current density distribution especially near the arc axis.