Showing papers on "Arc welding published in 2013"

A comparative study of pulsed Nd:YAG laser welding and TIG welding of thin Ti6Al4V titanium alloy plate

Abstract: This paper reports on a study aiming at comparing properties of the Ti6Al4V titanium alloy joints between pulsed Nd:YAG laser welding and traditional fusion welding. To achieve the research purpose, Ti6Al4V titanium alloy plates with a thickness of 0.8 mm were welded using pulsed Nd:YAG laser beam welding (LBW) and gas tungsten arc welding (TIG), respectively. Residual distortions, weld geometry, microstructure and mechanical properties of the joints produced with LBW and TIG welding were compared. During the tensile test, with the aid of a high speed infrared camera, evolution of the plastic strain within tensile specimens corresponding to LBW and TIG welding were recorded and analyzed. Compared with the TIG, the welded joint by LBW has the characters of small overall residual distortion, fine microstructure, narrow heat-affected zone (HAZ), high Vickers hardness. LBW welding method can produce joints with higher strength and ductility. It can be concluded that Pulsed Nd:YAG laser welding is much more suitable for welding the thin Ti6Al4V titanium alloy plate than TIG welding.

Advanced gas metal arc welding processes

Abstract: There is an increased requirement in the automotive, food and medical equipment industries to weld heat-sensitive materials, such as thin sheets, coated thin plates, stainless steel, aluminium and mixed joints. Nevertheless, relevant innovations in arc welding are not widely known and seldom used to their maximum potential. In the area of gas metal arc welding welding processes, digitalisation has allowed integration of software into the power source, wire feeder and gas regulation. This paper reviews developments in the arc welding process, particularly the effect of the set-up of the welding process parameters on waveform deposition. It is found that good weldability, good mechanical joint properties and acceptable process efficiency can be obtained for thin sheets through advanced power source regulation, especially over short circuiting, controlled polarity and electrode wire motion. The findings presented in this paper are valuable for waveform and deposition prediction. The need is furthermore noted for an algorithm that integrates gas flow parameters and wire motion control, as well as a variable sensor on the tip of the electrode, permitting flexibility of control of the current and the voltage waveform.

Autonomous weld seam identification and localisation using eye-in-hand stereo vision for robotic arc welding

Abstract: One of the main difficulties in using robotic welding in low to medium volume manufacturing or repair work is the time taken to programme the robot to weld a new part. It is often cheaper and more efficient to weld the parts manually. This paper presents a method for the automatic identification and location of welding seams for robotic welding using computer vision. The use of computer vision in welding faces some difficult challenges such as poor contrast, textureless images, reflections and imperfections on the surface of the steel such as scratches. The methods developed in the paper enables the robust identification of narrow weld seams for ferrous materials combined with reliable image matching and triangulation through the use of 2D homography. The proposed algorithms are validated through experiments using an industrial welding robot in a workshop environment. The results show that this method can provide a 3D Cartesian accuracy of within ±1 mm which is acceptable in most robotic arc welding applications.

Systems, methods, and apparatuses for monitoring weld quality

Abstract: An arc welder including an integrated monitor is disclosed. The monitor is capable of monitoring variables during a welding process and weighting the variables accordingly, quantifying overall quality of a weld, obtaining and using data indicative of a good weld, improving production and quality control for an automated welding process, teaching proper welding techniques, identifying cost savings for a welding process, and deriving optimal welding settings to be used as pre-sets for different welding processes or applications.

Autonomous seam acquisition and tracking system for multi-pass welding based on vision sensor

Abstract: Automatic welding technology is a solution to increase welding productivity and improve welding quality, especially in thick plate welding. In order to obtain high-quality multi-pass welds, it is necessary to maintain a stable welding bead in each pass. In the multi-pass welding, it is difficult to obtain a stable weld bead by using a traditional teaching and playback arc welding robot. To overcome these traditional limitations, an automatic welding tracking system of arc welding robot is proposed for multi-pass welding. The developed system includes an image acquisition module, an image processing module, a tracking control unit, and their software interfaces. The vision sensor, which includes a CCD camera, is mounted on the welding torch. In order to minimize the inevitable misalignment between the center line of welding seam and the welding torch for each welding pass, a robust algorithm of welding image processing is proposed, which was proved to be suitable for the root pass, filling passes, and the cap passes. In order to accurately track the welding seam, a Fuzzy-P controller is designed to control the arc welding robot to adjust the torch. The Microsoft Visual C++6.0 software is used to develop the application programs and user interface. The welding experiments are carried out to verify the validity of the multi-pass welding tracking system.

Solid-state welding of aluminum to copper—case studies

Abstract: This paper describes procedures for the joining of aluminum with copper via solid-state welding. Welding of dissimilar materials in order to reach a high strength and durable joints is a reasonable and outstanding challenge for industrial and especially for automotive applications. Nowadays, wiring and electrical systems, as for example batteries, turn out to be main drivers for new developments in the field of dissimilar joining technologies. Joining of aluminum to copper through a melting process leads to brittle intermetallic compounds, which cause failure of the joint already during cool down. Solid-state welding technologies allow the welding below melting temperature, so that phenomena at the interface, which lead to the formation of intermetallics under different conditions, are of interest to the resulting joint properties. Not only mechanical properties, but electrical resistivity and heat conduction are strongly dependent on those effects. Diffusion welding is performed as a model welding procedure, while friction stir welding and hybrid friction diffusion bonding are investigated as technological welding processes in this paper.

Numerical simulation of droplet detachment in pulsed gas–metal arc welding including the influence of metal vapour

Abstract: A numerical model of the droplet detachment of a gas–metal arc welding process is presented. The model is based on the volume of fluid method and focuses on the detailed description of the interaction between the arc and the anodic wire electrode. The influence of metal vapour on the arc plasma and the arc attachment at the wire is taken into account. The formation of metal vapour at the wire is described self-consistently as a function of the wire temperature by the help of the Hertz–Knudsen–Langmuir equation. Results are presented for a pulsed gas–metal arc welding process with a wire of mild steel and argon as the shielding gas.

Cold cracking tests—an overview of present technologies and applications

Abstract: Hot crack prevention in materials production and processing is an essential prerequisite for welded component safety. The causes of hot cracking can ultimately be attributed to the occurrence of metallurgical effects and to structural loads. More than 140 hot cracking test procedures have hitherto been developed for determining the hot cracking resistance. In principle, they are divided in self-restraint and externally loaded hot cracking tests with diverse process variants. Only some of the hot cracking tests are international standardized. Although various factors are known that encourage or prevent hot cracking, it is often not possible even with defined welding conditions to draw immediate conclusions about the hot cracking resistance of a welded component alone from a metallurgical composition of the base and filler materials. Based on an evaluation of the existing theories relating to hot cracking susceptibility assessment, this study summarizes the major hot cracking test procedures and highlights the application limits of the test procedures by presenting overviews along with explanations. It shows that weld hot cracking tests can generally be used to rank materials, welding consumables, and welding conditions. The evaluation of hot cracking test results and of their transferability among one another and to real components always requires consideration of the close relationships between metallurgy, welding process, and parameters, respectively, and prevailing restraint conditions.

System and method providing combined virtual reality arc welding and three-dimensional (3d) viewing

Abstract: A real-time virtual reality welding system including a programmable processor-based subsystem configured to generate simulation data corresponding to elements of a welding environment in virtual reality space; a three-dimensional (3D) conversion unit operatively connected to the programmable processor-based subsystem and configured to convert at least a portion of the simulation data, representative of at least a portion of the virtual welding environment, to 3D data in a stereoscopic 3D transmission format; and a 3D display-facilitating device operatively connected to the 3D conversion unit and configured to receive the 3D data from the 3D conversion unit and facilitate displaying of a stereoscopic representation of the 3D data.

Welding of titanium alloy by Disk laser

Abstract: The following article describes results of investigations on influence of laser welding parameters on the weld shape, quality and mechanical properties of 2.0 mm thick butt joints of titanium alloy Ti6Al4V (Grade 5 according to ASTM B265) welded with a new generation disk laser TRUMPF TRUDISK 3302, emitting at 1030 nm, with maximum output power 3300 W at circular laser beam spot, characterized by laser beam divergence 8.0 mm•mrad. The test butt joints of Ti6Al4V titanium alloy sheets were prepared as single square groove (I-type joint) and one-side laser welded without an additional material, at a flat position, using a specially designed system for shielding gas (purity 99.999%). The investigations at the initial stage were focused on detailed analysis of influence of the basic laser welding parameters such as laser power and welding speed on the shape and quality of single bead produced during bead-on-plate welding. Then the optimal parameters were chosen for laser welding of 2.0 mm thick butt joints of the titanium alloy Ti6Al4V. Edges of the titanium alloy sheets were melted in argon atmosphere by the laser beam focused on the top surface of butt joints. The test welded joints were investigated by visual inspection, metallographic examinations, hardness and micro-hardness measurements and mechanical tests such as tensile tests and bending tests. It was found that the welding mode is a keyhole welding and providing high quality of joints requires a special techniques and conditions of laser welding, as well as special gas shielding nozzles is required.

Cold Metal Transfer joining of magnesium AZ31B-to-aluminum A6061-T6

Abstract: Automotive manufacturers are faced with increasing pressure to reduce vehicle weight, improve fuel economy, reduce emissions, and enhance vehicle safety and performance. Therefore, an increasing number of vehicle structures are built using a combination of dissimilar materials such as steel, aluminum and magnesium. Though the advantages are potentially huge, this hybrid fabrication approach raises substantial technical challenges to the design of vehicle structures and the associated joining processes. Once two elements (e.g., magnesium–aluminum, aluminum–steel) are mixed in a high temperature welding pool, brittle intermetallic phases (IMP) can be easily formed. Experimental observations showed that a series of intermetallic phases will greatly reduce the mechanical performance of the welded dissimilar materials. In this study, welding of 1 mm thick magnesium AZ31B-to-1 mm thick aluminum A6061-T6 using a 1.6 mm diameter aluminum filler wire 4047 was investigated. Cold Metal Transfer (CMT) arc welding technique was adopted. The key feature of this process is that the motion of the wire has been integrated into the overall control of the process. The wire retraction motion assists droplet detachment during the short circuit, thus the metal can transfer into the welding pool without the aid of the electromagnetic force. In this way the heat input and spatter can be controlled and the IMP formation minimized thereby improving the joint strength. Extensive experiments were performed and analyzed. It was found that although extensive efforts have been exercised to control the heat input, Mg-rich intermetallic γ-Al 12 Mg 17 and Al-rich intermetallic β-Al 3 Mg 2 were still produced in the weld. Fracture surfaces of CMT welded AZ31B–Al6061-T6 joints exhibited the Mg-rich intermetallic ( γ-Al 12 Mg 17 ) which contributes to the weld strength degradation. To improve the joint, minimizing the content of the intermetallics especially Mg-rich intermetallics ( γ-Al 12 Mg 17 ) is essential.

The effect of arc behavior on weld geometry by high-frequency pulse GTAW process with 0Cr18Ni9Ti stainless steel

Abstract: Based on 0Cr18Ni9Ti austenitic stainless steel plate (h = 6 mm), a study on arc behavior by ultrasonic frequency pulse gas tungsten arc welding (GTAW) process has been carried out. The results show that with the increasing pulse frequency, an obvious pinch effect of arc plasma has been detected and also the increment of arc voltage, stiffness, and force. Then, the method, combining weld appearance and numerical simulation, has been adapted for weld behavior on the basis of arc behavior by ultrasonic frequency pulse GTAW process. As a result of arc shrinkage, the root radius of arc decreased, which caused narrower weld bead. The larger arc force led to more depression of pool surface that made the downward heat source and external force point, which had been important to increasing weld penetration. Meanwhile, the mobility of molten pool was enhanced by weld behavior compared with conventional GTAW process.

Influence of metal vapour on arc temperatures in gas-metal arc welding: convection versus radiation

Abstract: The presence of metal vapour in gas–metal arc welding has been shown to have two strong effects on the arc plasma: a decrease in temperature throughout the arc, and the formation of a local temperature minimum near the arc axis. These effects have been attributed, on the basis of different computational models, to either the increased radiative emission associated with the presence of metal vapour in the arc plasma, or the influence of the metal vapour influx on convective flow in the arc. This question is investigated using a three-dimensional computational model in which the production and the transport of metal vapour are taken into account self-consistently. Parameters relevant to welding of thin sheets of aluminum are examined. For these conditions, it is found that the first effect (the decrease in temperature throughout the arc) is due to both the increased radiative emission and the influence of the metal vapour influx on flow. The second effect (the local temperature minimum, which in this case occurs just below the wire electrode) is a consequence of the influence of aluminum vapour produced from the wire electrode on flow in the arc. By examining published results and the energy balance in the plasma, it is shown that for welding of steel with higher arc currents, the increased radiative emission can lead to a local temperature minimum at a greater distance from the wire electrode.

Thermal plasma properties for Ar–Al, Ar–Fe and Ar–Cu mixtures used in welding plasmas processes: I. Net emission coefficients at atmospheric pressure

Abstract: This article is devoted to the calculation of the net emission coefficient (NEC) of Ar?Al, Ar?Fe and Ar?Cu mixtures at atmospheric pressure for arc welding processes. The results are given in data tables for temperatures between 3?kK and 30?kK, for five plasma thicknesses (0, 0.5, 1, 2, 5?mm) and ten concentrations of metallic vapours (pure gas, 0.01%, 0.1%, 1%, 5%, 10%, 25%, 50%, 75% and pure metal vapours in mass proportions). The results are in good agreement with most of the works published on the subject for such mixtures. They highlight the influence of three parameters on the radiation of the plasma: the NEC is directly related to temperature and inversely related to plasma radius and is highly sensitive to the presence of metal vapours. Finally, numerical data are supplied in tables in order to develop accurate computational modelling of welding arc and to estimate both qualitatively and quantitatively the influence of each metallic vapour on the size and on the shape of the weld pool.

Microstructure and mechanical properties of a thick-section high-strength steel welded joint by novel double-sided hybrid fibre laser-arc welding

Abstract: In this paper, a novel double-sided hybrid fibre laser-arc welding procedure was developed to join 30 mm thick, high-strength steel, and this procedure was compared with conventional double-sided arc welding The welded joint was divided into two zones, the laser zone and the arc zone, and the microstructure and mechanical properties of the welded joint in these zones were investigated in detail The results indicated that the laser zone and arc zone predominately consisted of lath martensite with a high dislocation density The average grain sizes of the laser zone and the arc zone were smaller than that of the base metal The results also indicated that the laser zone and the arc zone possessed higher strength when compared with the base metal because of the fine lath martensite Meanwhile, the strength observed in the laser zone was slightly higher than that of the arc zone due to the small average effective grain size On the contrary, the toughness of the base metal was higher than the toughness in the laser zone and the arc zone because of massive polygonal ferrites Meanwhile, a significant increase in the toughness of the laser zone when compared with the arc zone occurred due to an increase in the prevalence of grain boundaries with large misorientation angles

Welding systems having non-contact temperature measurement systems

Abstract: Welding systems including welding torch assemblies are provided. The welding torch assembly may include a welding torch adapted to be utilized in a welding operation to establish a welding arc between the welding torch and a workpiece. Shielding gas may be supplied to the welding torch for establishment of a gas shielding area around a weld pool. The welding torch assembly may also include a temperature sensing system having a non-contact temperature sensor coupled to the welding torch and adapted to sense a temperature of the workpiece at a location outside of the molten weld pool.

Determination of submerged arc welding process parameters using Taguchi method and regression analysis

Abstract: This paper details the application of Taguchi technique and regression analysis to determine the optimal process parameters for submerged arc welding (SAW). The planned experiments are conducted in the semiautomatic submerged arc welding machine and the signal-to-noise ratios are computed to determine the optimum parameters. The percentage contribution of each factor is validated by analysis of variance (ANOVA) technique. Multiple regression analysis (MRA) is conducted using statistical package for social science (SPSS) software and the mathematical model is built to predict the bead geometry for any given welding conditions.

Investigation on weldability of magnesium alloy thin sheet T-joints: arc welding, laser welding, and laser-arc hybrid welding

Abstract: Four welding methods, including laser welding, gas tungsten arc (GTA) welding, laser–GTA hybrid welding, and laser–GTA hybrid welding with cold welding wire, are used to investigate the weldability of T-joints of magnesium alloy thin sheet. Stake welding process is presented in this paper in order to overcome the defects, such as stress concentration and deformation, and improve the accessibility of T-joints in fillet welding process. The effect of heat source type on weldability of T-joints is analyzed. The microstructures and mechanical properties are investigated. Experimental results indicate that comparing with the other three welding methods, laser–GTA hybrid welding with cold welding wire is the most effective process for T-joints of magnesium alloy thin sheet. In this process, T-joints are full penetration and the toes are smooth and round, and besides, reinforcement forms on the upside of weld bead by the filled wire. The mechanical properties of T-joints made with laser–GTA hybrid welding with cold welding wire achieve 90 % of that of base metal and are superior to that without welding wire.

The technology and welding joint properties of hybrid laser-tig welding on thick plate

Abstract: The technologies of autogenous laser welding and hybrid laser-TIG welding are used on thick plate of high strength lower alloy structural steel 10CrNiMnMoV in this article. The unique advantages of hybrid laser-TIG welding is summarized by comparing and analyzing the process parameters and welding joints of autogenous laser welding laser welding and hybrid laser-TIG welding. With the optimal process parameters of hybrid welding, the good welding joint without visible flaws can be obtained and its mechanical properties are tested according to industry standards. The results show that the hybrid welding technology has certain advantages and possibility in welding thick plates. It can reduce the demands of laser power, and it is significant for lowering the aspect ratio of weld during hybrid welding, so the gas in the molten pool can rise and escape easily while welding thick plates. Therefore, the pores forming tendency decreases. At the same time, hybrid welding enhances welding speed, and optimizes the energy input. The transition and grain size of the microstructure of hybrid welding joint is better and its hardness is higher than base material. Furthermore, its tensile strength and impact toughness is as good as base material. Consequently, the hybrid welding joint can meet the industry needs completely.

Thermal plasma properties for Ar–Cu, Ar–Fe and Ar–Al mixtures used in welding plasmas processes: II. Transport coefficients at atmospheric pressure

Abstract: This article is devoted to the calculation of thermodynamic properties (mass density, enthalpy and specific heat at constant pressure) and transport coefficients (viscosity, electrical conductivity, thermal conductivity and combined diffusion coefficients) of mixtures of argon and aluminum, iron and copper vapour at atmospheric pressure. Data are presented for the temperature range 300 to 30 000 K, for different concentrations of the metal vapours. The dependence of the properties on metal vapour type and concentration are discussed. Mixtures of argon and metal vapour occur in the arc welding and in other plasma applications. Tabulations of the data are presented, and will be of use in computational modelling of such applications.

Recent developments in modeling of heat transfer during TIG welding-a review

Abstract: This paper is an attempt to list the recent developments in the area of arc welding heat transfer simulation. Fusion welding modeling is a broad area where a number of research groups were spending their efforts to get solutions for both research and industrial problems. Starting from fundamentals of arc physics, heat transfer, microstructure models, thermal stress, and modern techniques like pattern recognition comes into picture while considering the complete solution of welding-related problems. These areas are developing almost independently and there are only few efforts to couple them together as computational welding mechanics, which includes the computational fluid mechanics, magneto hydrodynamics, thermo mechanical problems, and computational material science. Here, an effort is made to list down major developments in this area and to plot the present state of research on the TIG welding heat transfer modeling by giving priority to last few years of research.

Microstructure and wear properties of nickel-based surfacing deposited by plasma transferred arc welding

Abstract: Nickel-based alloy coating was deposited on AISI 304 L stainless steel substrate using plasma transferred arc welding (PTAW). Microstructure and tribological characteristics of the coating were studied. The as-deposited microstructure mainly consists of Ni-rich γ (Ni, Fe) phase, Cr 7 C 3 , CrB, Cr 3 C 2 , M 23 C 6 , Ni 3 B, and Ni 3 Si. Compared with that of the 304 L stainless steel substrate, the wear resistance of the coating greatly improves. The wear test demonstrates that the wear mechanism depends on wearing time and applied load. When the wearing time is short, the wear mechanism is abrasive wear under low load and adhesive wear under high load. When the time is relatively long, the wear mechanisms are adhesive wear and oxidation wear under low load; fatigue wear appears under high load.

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.

Study on the application for electromagnetic controlled molten pool welding process in overhead and flat position welding

Abstract: In fusion welding, gravity makes a molten metal flow downward and it sometimes causes an irregular shaped weld bead and weld defects such as an undercut. To solve this problem, the authors propose a new electromagnetic controlled molten pool welding process method which controls the molten metal flow by using upward electromagnetic forces, and the applicability of this method to industry is examined. In flat position welding with excessive heat input, the molten metal tends to sag down and an undercut defect is likely to occur. It is found that the upward electromagnetic force given by adjusting the conditions of magnetic field can lift the molten metal up, resulting in the remarkably improved shape of a penetration bead. It is further found that, even in overhead position welding, a well shaped penetration bead without undercuts is obtained by adjusting the welding touch angle as well as magnetic field conditions.