Showing papers on "Shielded metal arc welding published in 2013"

Advanced device for welding training, based on augmented reality simulation, which can be updated remotely

Abstract: The invention relates to an advanced device for welding training, based on augmented reality simulation, which can be updated remotely and which allows simulation of all types of industrial welding, i.e. coated electrode (SMAW), MIG/MAG (GMAW, FCAW) and TIG (GTAW), all types of materials and all types of existing joints in all welding positions (1F to 4F, 1G to 6G, 6GR), providing a very exact simulation of the behaviour of a real welding machine through the use of augmented reality technology which allows interaction between different elements in multiple layers, all of which is implemented on a system for checking, monitoring and evaluating students, which allows the teacher to test the student in real time without the teacher being present in the training room, including from a remote station.

Number size distribution of fine and ultrafine fume particles from various welding processes.

Abstract: Studies in the field of environmental epidemiology indicate that for the adverse effect of inhaled particles not only particle mass is crucial but also particle size is. Ultrafine particles with diameters below 100 nm are of special interest since these particles have high surface area to mass ratio and have properties which differ from those of larger particles. In this paper, particle size distributions of various welding and joining techniques were measured close to the welding process using a fast mobility particle sizer (FMPS). It turned out that welding processes with high mass emission rates (manual metal arc welding, metal active gas welding, metal inert gas welding, metal inert gas soldering, and laser welding) show mainly agglomerated particles with diameters above 100 nm and only few particles in the size range below 50 nm (10 to 15%). Welding processes with low mass emission rates (tungsten inert gas welding and resistance spot welding) emit predominantly ultrafine particles with diameters well below 100 nm. This finding can be explained by considerably faster agglomeration processes in welding processes with high mass emission rates. Although mass emission is low for tungsten inert gas welding and resistance spot welding, due to the low particle size of the fume, these processes cannot be labeled as toxicologically irrelevant and should be further investigated.

Manganese in Occupational Arc Welding Fumes—Aspects on Physiochemical Properties, with Focus on Solubility

Abstract: Physicochemical properties, such as particle sizes, composition, and solubility of welding fumes are decisive for the bioaccessibility of manganese and thereby for the manganese cytotoxic and neurotoxic effects arising from various welding fumes. Because of the diverse results within the research on welding fume solubility, this article aims to review and discuss recent literature on physicochemical properties of gas metal arc welding, shielded metal arc welding, and flux-cored arc welding fumes, with focus on solubility properties. This article also presents a short introduction to the literature on arc welding techniques, health effects from manganese, and occupational exposure to manganese among welders.

Systems and methods for welding electrodes

Abstract: The invention relates generally to welding and, more specifically, to welding wires for arc welding, such as Gas Metal Arc Welding (GMAW) or Flux Core Arc Welding (FCAW). In one embodiment, a tubular welding wire includes a sheath and a core. Further, the core includes a carbon source and an agglomerate having a Group I or Group II compound, silicon dioxide, and titanium dioxide. Additionally, the carbon source and the agglomerate together comprise less than 10% of the core by weight.

Digital Control for an Arc Welding Machine Based on Resonant Converters and Synchronous Rectification

Abstract: This paper presents a field-programmable gate array (FPGA)-based generation of optimized drive signals for resonant converters using synchronous rectification (SR) applied to an arc welding machine. The proposed digital implementation makes the most of the FPGAs capabilities by setting in open loop the arc welding current with enough resolution to establish precisely the operation point, according to the welding technique and metal part requirements. It also optimizes other parameters of interest such as the initial and final welding transient. The resulting system is very flexible because is valid for Tungsten inert gas, shielded metal arc welding, and metal inert gas welding techniques. A novel ad-hoc SR control algorithm for current mode operation that eliminates the dead-times of the power MOSFETs' switching period is proposed. Finally, the experimental results are presented including an efficiency comparison between diodes and SR solutions.

Development of a highly efficient hot-wire laser hybrid process for narrow-gap welding—welding phenomena and their adequate conditions

Abstract: The purpose of this work is to develop hot-wire laser welding for narrow-gap joints. Test pieces of ASTM A 304 stainless steel with a gap width of 3 mm were used. With welding by tentative filler rod made of Inconel 600 alloy, melting phenomena of the molten pool and the weld bead formation during welding were investigated by in situ observation using a high-speed camera. Variations in the main welding parameters such as wire current, wire feeding position, laser irradiation angle, and wire feeding angle were investigated to determine appropriate conditions. Experiments showed that under the optimum welding conditions, hot-wire laser welding was able to produce complete weld deposition with very low dilution of the base metal. An experiment on laser beam reflection indicated that the laser beam reflected from the molten pool was a crucial phenomenon to explain the formation of the weld bead, especially in terms of melting the side groove wall of the base metal. Welding parameters as mentioned above significantly affected weld quality. Furthermore, in the case of welding with filler wire ER NiCrCoMo-1, the Vickers hardness distribution along the transverse welding direction was examined to evaluate weld properties and the bonding strength at the fusion interface was examined in a tensile test, and the results showed that there was no great difference in the hardness profile throughout the cross section of the weld plate. Additionally, metallurgical examination of the fracture surface revealed the rupture occurred at the weld metal, probably because the bonding at the fusion interface was stronger than the weld metal. Therefore, the development of laser welding with hot wire can advance the multi-pass weld for an ultra-narrow-gap joint.

Keyhole welding with CF-TIG (cathode focussed GTA)

Abstract: In this paper, the results for keyhole welding of stainless steel 1.4301 and mild steel 1.0117 with a cathode focussed gas tungsten arc process are presented. These tests were carried out in preparation for welding the root faces of Y- or double V-groove weld preparations of thick metal plates. Welded plate thicknesses range from 6 to 10 mm for stainless steels and 6 to 12 mm for mild steels. Welding speeds are in the range of 20 to 115 cm/min at currents from 400 to 800 A. Especially for stainless steel, a big range of applicable and stable process parameters could be found. The process also works fine for mild steel even though the achievable parameter range is smaller.

Effect of Welding Passes on Heat Affected Zone and Tensile Properties of AISI 304 Stainless Steel and Chrome-Manganese Austenitic Stainless Steel

Abstract: This paper aims at a systematic comparison of effect of single, double and triple pass welding on heat affected zone and tensile strength of AISI 304 stainless steel and chrome-manganese austenitic stainless steel. Degree of sensitization (DOS) increased with increase in number of passes and highest DOS (35.53%) was obtained for triple pass welding of chrome-manganese austenitic stainless steel. The decrease in tensile strength is relatively more in chrome-manganese austenitic stainless steel as compared to AISI 304 SS. The mode of failure for AISI 304 SS was ductile fracture, whereas chrome-manganese austenitic stainless steel failed due to intergranular brittle fracture.

Gas Metal Arc Welding Process Modeling and Prediction of Weld Microstructure in MIL A46100 Armor-Grade Martensitic Steel

Abstract: A conventional gas metal arc welding (GMAW) butt-joining process has been modeled using a two-way fully coupled, transient, thermal-mechanical finite-element procedure. To achieve two-way thermal-mechanical coupling, the work of plastic deformation resulting from potentially high thermal stresses is allowed to be dissipated in the form of heat, and the mechanical material model of the workpiece and the weld is made temperature dependent. Heat losses from the deposited filler-metal are accounted for by considering conduction to the adjoining workpieces as well as natural convection and radiation to the surroundings. The newly constructed GMAW process model is then applied, in conjunction with the basic material physical-metallurgy, to a prototypical high-hardness armor martensitic steel (MIL A46100). The main outcome of this procedure is the prediction of the spatial distribution of various crystalline phases within the weld and the heat-affected zone regions, as a function of the GMAW process parameters. The newly developed GMAW process model is validated by comparing its predictions with available open-literature experimental and computational data.

Computational Modeling of Microstructural-Evolution in AISI 1005 Steel During Gas Metal Arc Butt Welding

Abstract: A fully coupled (two-way), transient, thermal-mechanical finite-element procedure is developed to model conventional gas metal arc welding (GMAW) butt-joining process. Two-way thermal-mechanical coupling is achieved by making the mechanical material model of the workpiece and the weld temperature-dependent and by allowing the potential work of plastic deformation resulting from large thermal gradients to be dissipated in the form of heat. To account for the heat losses from the weld into the surroundings, heat transfer effects associated with natural convection and radiation to the environment and thermal-heat conduction to the adjacent workpiece material are considered. The procedure is next combined with the basic physical-metallurgy concepts and principles and applied to a prototypical (plain) low-carbon steel (AISI 1005) to predict the distribution of various crystalline phases within the as-welded material microstructure in different fusion zone and heat-affected zone locations, under given GMAW-process parameters. The results obtained are compared with available open-literature experimental data to provide validation/verification for the proposed GMAW modeling effort.

Weld pool temperatures of steel S235 while applying a controlled short-circuit gas metal arc welding process and various shielding gases

Abstract: The temperature determination of liquid metals is difficult and depends strongly on the emissivity. However, the surface temperature distribution of the weld pool is an important characteristic of an arc weld process. As an example, short-arc welding of steel with a cold metal transfer (CMT) process is considered. With optical emission spectroscopy in the spectral region between 660 and 840 nm and absolute calibrated high-speed camera images the relation between temperature and emissivity of the weld pool is determined. This method is used to obtain two-dimensional temperature profiles in the pictures. Results are presented for welding materials (wire G3Si1 on base material S235) using different welding CMT processes with CO2 (100%), Corgon 18 (18% CO2 + 82% Ar), VarigonH6 (93.5% Ar + 6.5% H2) and He (100%) as shielding gases. The different gases are used to study their influence on the weld pool temperature.

Microstructural Transformations of Dissimilar Austenite-Ferrite Stainless Steels Welded Joints

Abstract: This research studies the metallurgical transformations happening during the SMAW welding of AISI 316L austenitic stainless steel with AISI 430 ferritic stainless steel. Two different electrodes, AWS E309L austenitic and AWS E2209-16 duplex stainless steels 3.2 mm diameter, were used to perform the study. The joining was made with a single pass welding and keeping a low heat input ranging from 700 - 1000 J/mm. The influence of the type of electrode and the heat input on the microstructural evolution of the heat affected and the fusion zone was evaluated. Differences between δ ferrite morphology were found for both weld metals. The heat affected zone of the ferritic side showed grain coarsening and grain refinement with martensite at the grain boundaries. Tensile strength was similar for both welding conditions. Microhardness and δ ferrite percent were measured as well.

Microstructural Analysis of Ballistic Tests on Welded Armor Steel Joints

Abstract: The deformation and fracture behavior of welded joints made from quenched and tempered steel closely conforming to AISI 4340 were investigated. Due to weld thermal cycles and under matching fillers, the welded armor steel joints showed poor ballistic performance compared with the base metal (BM). The problems encountered in the past were reduced by depositing a soft austenitic stainless-steel buttering layer in between the BM and the hardfaced layer. This method showed enhancement in ballistic performance and good weld integrity. In this investigation, an attempt is made to investigate the microstructure after ballistic testing on the weld metal zone consisting of the hardfaced interlayer. The results reveal the microstructural characteristics before and after ballistic testing of armor steel welds fabricated using the shielded metal arc welding (SMAW) process.

Welding of nickel-based alloy 617 using modified dip arc processes

Abstract: The widespread application of nickel-based alloys as structural materials in chemical, nuclear and power generation industries is often limited due to weldability issues. Technological and metallurgical problems such as lack of fusion or hot cracking require specific welding guidelines as well as knowledge of the welding metallurgy to produce welds that fulfill high quality requirements. Due to the lower heat input modified dip arc welding is a potential alternative joining technique for hot crack sensitive nickel-based alloys. This paper contributes to the application of modified dip arc processes for butt welding of alloy 617 (2.4663). The influence of reduced heat input on microstructural and mechanical properties were investigated. Particular attention was given to the occurrence of hot cracking in the weld metal and base metal HAZ (heat-affected zone) using light optical microscopy, EDS analysis and electron probe microanalysis. The results indicate that the modified dip arc processes provide excellent weld quality and economic efficiency. However, microstructural observations showed that hot cracking in the form of microcracks could not be completely avoided. The modified dip arc welded joints exhibited good tensile strength and impact toughness. The mechanical properties are comparable to commonly GMA (gas metal arc) pulsed arc welding and are not influenced by the microcracks.

Characterization of duplex stainless steel weld metals obtained by hybrid plasma-gas metal arc welding

Abstract: Despite its high efficiency, autogenous keyhole welding is not well-accepted for duplex stainless steels because it causes excessive ferrite in as-welded duplex microstructure, which leads to a degradation in toughness and corrosion properties of the material. Combining the deep penetration characteristics of plasma arc welding in keyhole mode and metal deposition capability of gas metal arc welding, hybrid plasma - gas metal arc welding process has considered for providing a proper duplex microstructure without compromising the welding efficiency. 11.1 mm-thick standard duplex stainless steel plates were joined in a single-pass using this novel technique. Same plates were also subjected to conventional gas metal arc and plasma arc welding processes, providing benchmarks for the investigation of the weldability of the material. In the first place, the hybrid welding process enabled us to achieve less heat input compared to gas metal arc welding. Consequently, the precipitation of secondary phases, which are known to be detrimental to the toughness and corrosion resistance of duplex stainless steels, was significantly suppressed in both fusion and heat affected zones. Secondly, contrary to other keyhole techniques, proper cooling time and weld metal chemistry were achieved during the process, facilitating sufficient reconstructive transformation of austenite in the ferrite phase.

Mass Transfer of Nickel-Base Alloy Covered Electrode During Shielded Metal Arc Welding

Abstract: The mass transfer in shielded metal arc welding of a group of nickel-base alloy covered electrodes according to AWS specification A5.11-A5.11M was investigated by directly measuring their deposited metal compositions. The results indicate that the chromium mass-transfer coefficient is in the range of 86 to 94 pct, iron in the range of 82 to 89 pct, manganese in the range of 60 to 73 pct, niobium in the range of 44 to 56 pct, and silicon in the range of 41 to 47 pct. The metal mass-transfer coefficient from the core wire is markedly higher than that from the coating. The basicity of slag, the metal contents in the flux coating, and the welding current together affect the mass transfer. As the basicity of slag increases, the mass-transfer coefficients of Mn, Fe, and Cr slightly increase, but those of Nb and Si decrease significantly. As the niobium and manganese contents increase in the coating, their mass-transfer coefficients also increase. However, iron is different. The content of iron in the coating in the range of 8 to 20 wt pct results in the optimal effective mass transfer. The lower, or higher, iron content leads to lower mass-transfer coefficient. As the welding current increases, the mass-transfer coefficients of niobium and manganese decrease, but chromium and silicon increase. Iron has the lowest mass-transfer coefficient when welded under the operating current of 100 A.

Characterization of Duplex Stainless Steel Weld Metals Obtained by Hybrid Plasma-Gas Metal Arc Welding (Caracterização de Soldas de Aço Inoxidável Duplex Obtidas por Soldagem Híbrida MIG-Plasma)

Abstract: Despite its high efficiency, autogenous keyhole welding is not well-accepted for duplex stainless steels because it causes excessive ferrite in as-welded duplex microstructure, which leads to a degradation in toughness and corrosion properties of the material. Combining the deep penetration characteristics of plasma arc welding in keyhole mode and metal deposition capability of gas metal arc welding, hybrid plasma – gas metal arc welding process has considered for providing a proper duplex microstructure without compromising the welding efficiency. 11.1 mm-thick standard duplex stainless steel plates were joined in a single-pass using this novel technique. Same plates were also subjected to conventional gas metal arc and plasma arc welding processes, providing benchmarks for the investigation of the weldability of the material. In the first place, the hybrid welding process enabled us to achieve less heat input compared to gas metal arc welding. Consequently, the precipitation of secondary phases, which are known to be detrimental to the toughness and corrosion resistance of duplex stainless steels, was significantly suppressed in both fusion and heat affected zones. Secondly, contrary to other keyhole techniques, proper cooling time and weld metal chemistry were achieved during the process, facilitating sufficient reconstructive transformation of austenite in the ferrite phase.

Effect of Welding Heat Input on Grain Size and Microstructure of 316L Stainless Steel Welded Joint

Abstract: Influences of heat input on the microstructure and grain size of shielded metal arc welded 316L stainless steel joints were studied. Three heat input combinations were selected from the operating window of the shielded metal arc welding process and welded joints made using these combinations were subjected to microstructural evaluations so as to analyze the effect of thermal arc energy on the microstructure and grain size of these joints. The results of this investigation indicate that the microstructure of the weld zone and the fusion zone are austenite and a small amount of ferrite while the microstructure of the heat affected zone (HAZ) are austenite and a small amount of MC type carbides, and it can be seen that the amount of ferrite in the weld zone decreases with heat input. For the joints investigated in this study, the average grain size in the HAZ increases with heat input.

Systems and methods for low-manganese welding wire

Abstract: The invention relates generally to welding and, more specifically, to welding wires for arc welding, such as Gas Metal Arc Welding (GMAW) or Flux Core Arc Welding (FCAW). In one embodiment, a tubular welding wire includes a sheath and a core. The tubular welding wire includes less than approximately 0.4% manganese metal or alloy by weight, and the tubular welding wire is configured to form a weld deposit having less than approximately 0.5% manganese by weight.

Arc Welding Technology for Automotive Steel Sheets

Abstract: Recent research progresses of arc welding techniques are described, focusing on the automotive chassis members or body members. As for welded joint performance, static strength and fatigue strength are improved with increasing of steel strength less than 780 MPa tensile strength. Additionally, galvanized steel sheets contribute to corrosion resistance of weld parts. Developed welding materials have made it possible to improve welding activities such as reducing spatters, gap allowance or weldability of galvanized steel sheets. In contrast, components of the steel sheet also effects on welding phenomenon, a flat bead geometry is obtained by increasing Si content of steel sheets. Low heat input welding such as CMT (Cold metal transfer) welding has begun to use for body welding and cross tension strength of advanced high tensile strength steel are improved by CMT applied arc spot welding.

Pipeline welding method

Abstract: The invention discloses a pipeline welding method which includes the steps: firstly, processing and assembling a weld joint to form a correct welding joint form; secondly, selecting a GTAW (gas tungsten arc welding) and SMAW (shielded metal arc welding) combined welding method for welding; and thirdly, performing post-weld heat treatment for the finished weld joint The root is made of welding materials fine in anti-cracking performance, and the GTAW method is selected to effectively inhibit the cracking tendency of the root The strength of the weld joint is guaranteed by the combined strength of two kinds of welding materials, and the overall strength of the joint is higher than the strength of a base material

Laser-assisted plasma arc welding of stainless steel

Abstract: A plasma arc and a low-power/high beam quality laser beam were coaxially combined into one process in order to obtain a more efficient and stable arc for thin sheet welding applications. Theoretical discussion of interaction mechanisms between the laser beam and the plasma arc and results of bead-on-plate welding trials carried out on AISI 304 stainless steel will be presented. Measurements were made of electrical and geometrical arc properties with and without assistance from the laser beam. Additionally, the impact of the laser beam on the weld seam geometry was evaluated. The results showed that the use of the additional low-power laser beam is capable of producing significant process improvements in comparison to the individual plasma arc process alone with respect to arc stability and welding performance.