Showing papers on "Arc welding published in 2012"

Gas tungsten arc and laser beam welding processes effects on duplex stainless steel 2205 properties

Abstract: A comparative study on the influence of gas tungsten arc welding (GTAW) and carbon dioxide laser beam welding (LBW) processes on the size and microstructure of fusion zone FZ then, on the mechanical and corrosion properties of duplex stainless steel DSS grade 2205 plates of 6.4 mm thickness was investigated. Autogenous butt welded joints were made using both GTAW and LBW. The GTA welded joint was made using well established welding parameters (i.e., current ampere of 110 A, voltage of 12 V, welding speed of 0.15 m/min and argon shielding rate of 15 l/min). While optimum LBW parameters were used (i.e., welding speed of 0.5 m/min, defocusing distance of 0.0 mm, argon shielding flow rate of 20 l/min and maximum output laser power of 8 kW). The results achieved in this investigation disclose that welding process play an important role in obtaining satisfactory weld properties. In comparison with GTAW, LBW has produced welded joint with a significant decrease in FZ size and acceptable weld profile. The ferrite–austenite balance of both weld metal WM and heat affected zone (HAZ) are influenced by heat input which is a function of welding process. In comparison with LBW, GTAW has resulted in ferrite–austenite balance close to that of base metal BM due to higher heat input in GTAW. However, properties of LB welded joint, particularly corrosion resistance are much better than that of GTA welded joint. The measured corrosion rates for LBW and GTAW joints are 0.05334 mm/year and 0.2456 mm/year, respectively. This is related to the relatively small size of both WM and HAZ produced in the case of LBW. In other words, properties of welded joints are remarkably influenced by FZ size rather than the produced austenite–ferrite balance.

Characterization of Joint Quality in Ultrasonic Welding of Battery Tabs

Abstract: Manufacturing of lithium-ion battery packs for electric or hybrid electric vehicles requires a significant amount of joining such as welding to meet desired power and capacity needs. However, conventional fusion welding processes such as resistance spot welding and laser welding face difficulties in joining multiple sheets of highly conductive, dissimilar materials with large weld areas. Ultrasonic metal welding overcomes these difficulties by using its inherent advantages derived from its solid-state process characteristics. Although ultrasonic metal welding is well-qualified for battery manufacturing, there is a lack of scientific quality guidelines for implementing ultrasonic welding in volume production. In order to establish such quality guidelines, this paper first identifies a number of critical weld attributes that determine the quality of welds by experimentally characterizing the weld formation over time. Samples of different weld quality were cross-sectioned and characterized with optical microscopy, scanning electronic microscopy (SEM), and hardness measurements in order to identify the relationship between physical weld attributes and weld performance. A novel microstructural classification method for the weld region of an ultrasonic metal weld is introduced to complete the weld quality characterization. The methodology provided in this paper links process parameters to weld performance through physical weld attributes.Copyright © 2012 by ASME and General Motors

Exposure to Inhalable, Respirable, and Ultrafine Particles in Welding Fume

Abstract: This investigation aims to explore determinants of exposure to particle size-specific welding fume. Area sampling of ultrafine particles (UFP) was performed at 33 worksites in parallel with the collection of respirable particles. Personal sampling of respirable and inhalable particles was carried out in the breathing zone of 241 welders. Median mass concentrations were 2.48 mg m(-3) for inhalable and 1.29 mg m(-3) for respirable particles when excluding 26 users of powered air-purifying respirators (PAPRs). Mass concentrations were highest when flux-cored arc welding (FCAW) with gas was applied (median of inhalable particles: 11.6 mg m(-3)). Measurements of particles were frequently below the limit of detection (LOD), especially inside PAPRs or during tungsten inert gas welding (TIG). However, TIG generated a high number of small particles, including UFP. We imputed measurements

Dual-spectrum digital imaging welding helmet

Abstract: Arc welding systems, methods, and apparatus that provide dual-spectrum, real-time viewable, enhanced user-discrimination between arc welding characteristics during an arc welding process. Welding headgear is configured to shield a user from harmful radiation and to include a digital camera or cameras to provide dual-spectrum (i.e., both visible spectrum and infrared spectrum) real-time digital video image frames. The welding headgear is also configured with an optical display assembly for displaying real-time digital video image frames to the user while wearing the headgear during an arc welding process. Image processing is performed on the visible and infrared spectrum video image frames to generate dual-spectrum video image frames providing an integrated and optimized view of both the visible and thermal characteristics of the arc welding process which can be viewed by the user on the optical display assembly in real time.

Microstructure and mechanical properties of aluminum 5083 weldments by gas tungsten arc and gas metal arc welding

Abstract: The mechanical properties and microstructural features of aluminum 5083 (AI5083) weldments processed by gas tungsten arc welding (GTAW) and gas metal arc welding (GMAW) are investigated. Weldments processed by both methods are mechanically softer than the parent material AI5083, and could be potential sites for plastic localization. It is revealed that AI5083 weldments processed by GTAW are mechanical more reliable than those by GMAW. The former bears higher strength, more ductility, and no apparent microstructure defects. Perceivable porosity in weldments by GMAW is found, which could account for the distinct mechanical properties between weldments processed by GTAW and GMAW. It is suggested that caution should be exercised when using GMAW for AI5083 in the high-speed-train industry where such light weight metal is broadly used.

The Effect of Gas Metal Arc Welding (GMAW) Processes on Different Welding Parameters

Abstract: Gas Metal Arc Welding (GMAW) process is leading in the development in arc welding process which is higher productivity and good in quality. In this study, the effects of different parameters on welding penetration, microstructural and hardness measurement in mild steel that having the 6 mm thickness of base metal by using the robotic gas metal arc welding are investigated. The variables that choose in this study are arc voltage, welding current and welding speed. The arc voltage and welding current were chosen as 22, 26 and 30 V and 90, 150 and 210 A respectively. The welding speed was chosen as 20, 40 and 60 cm/min. The penetration, microstructure and hardness were measured for each specimen after the welding process and the effect of it was studied. As a result, it obvious that increasing the parameters value of welding current increased the value of depth of penetration. Other than that, arc voltage and welding speed is another factor that influenced the value of depth of penetration. The microstructure shown the different grain boundaries of each parameters that affected of the welding parameters.

Improving arc joining of Al to steel and Al to stainless steel

Abstract: Gas-tungsten arc welding (GTAW) with controlled heat input could avoid the formation of massive brittle Al–Fe intermetallics during solidification in dissimilar-metal joining of aluminum to steel. In the first part of the present study an Al–Mg alloy was joined to galvanized steel by GTAW with an Al–Si filler metal. The weld solidification microstructure was explained based on the Al–Mg–Si phase diagram. Ultrasonic vibration during GTAW increased the joint strength by 27%. Grain refinement, decreased Fe–Al intermetallics, and increased microhardness in both the heat-affected zone and the weld were observed, thus explaining the improved joint strength. In the second part, an Al–Mg alloy was joined to 304 stainless steel using a Zn-15Al filler metal with a noncorrosive flux core. The weld solidification microstructure was explained based on the Al–Zn–Mg phase diagram. Postweld heat treatment (PWHT) at 280 °C for 30 min doubled or even tripled the joint strength depending on the Al-sheet thickness. Dissolution of coarse Zn-rich particles at the weld/steel interface was observed after PWHT, thus eliminating these weak particles from the interface. The formation of Zn-rich particles near the interface and their dissolution by PWHT were explained based on the Al–Fe–Zn phase diagram.

Effects of Activating Flux on Weld Bead Geometry of Inconel 718 Alloy TIG Welds

Abstract: The purpose of this work is to investigate the effects of activating fluxes and welding parameter to the penetration and depth-to-width ratio (DWR) of weld bead of Inconel 718 alloy welds in the tungsten inert gas (TIG) welding process. In the activating flux with TIG (A-TIG) welding process, the single-component fluxes used in the initial experiment were SiO2, NiO, MoO3, Cr2O3, TiO2, MnO2, ZnO, and MoS2. Based on the higher DWR of weld bead, four fluxes were selected to create six new mixtures using 50% of each original flux. The A-TIG weldment coated 50% SiO2 + 50% MoO3 flux and 75° of electrode tip angle were provided with better welding performance. In addition, the experimental procedure of flux-bounded TIG (FB-TIG) welding with the same welding conditions and flux produced full penetration of weld bead on a 6.35 mm thickness of Inconel 718 alloy plate with single pass weld.

Ultrasonic welding of dissimilar metals, AA6061 and Ti6Al4V

Abstract: Ultrasonic welding of Ti6Al4V sheet and A6061 aluminum alloy sheet was conducted. The influence of ultrasonic welding parameters on the mechanical properties, the interface microstructure, the micro-hardness and the composition diffusion of the welded joint was investigated. It was shown to be possible to join Ti6Al4V sheet and A6061 aluminum alloy sheet through ultrasonic welding. After ultrasonic welding, the hardness of both the matrices increased, and there appeared to be some amount of diffusion across the welding interface. Various welding pressures and welding times were used and the strength of the welded joint was at its optimal value with a welding pressure of 0.4 MPa and a welding time of 170 ms.

Local Exhaust Ventilation for the Control of Welding Fumes in the Construction Industry—A Literature Review

Abstract: Arc welding is a common unit operation in the construction industry, where frequent changes in location and welding position make it more difficult to control fume exposures than in industries where fixed locations are the norm. Welders may be exposed to a variety of toxic airborne contaminants including manganese (Mn) and hexavalent chromium (CrVI). Local exhaust ventilation (LEV) is a well-known engineering control for welding fumes but has not been adopted widely in the construction industry. This literature review presents data on the performance of a variety of LEV systems for welding fume control from the construction (five references), shipyard (five references), and other industries. The studies indicate that LEV can reduce fume exposures to total particulate, Mn, and CrVI to levels below currently relevant standards. Field studies suggest that 40-50% or more reduction in exposure is possible with portable or fixed LEV systems relative to natural ventilation but that correct positioning of the hood and adequate exhaust flow rates are essential. Successful implementation of extraction guns for gas metal arc welding (GMAW) and flux core arc welding has been demonstrated, indicating that a successful balance between extraction airflow and shielding gas requirements is possible. Work practices are an important part of achieving successful control of fume exposures; in particular, positioning the hood close to the arc, checking exhaust flow rates, and avoiding the plume. Further research is needed on hood size effects for controlling welding fume with portable LEV systems and identifying and overcoming barriers to LEV use in construction.

Immunotoxicology of arc welding fume: Worker and experimental animal studies

Abstract: Arc welding processes generate complex aerosols composed of potentially hazardous metal fumes and gases. Millions of workers worldwide are exposed to welding aerosols daily. A health effect of welding that is of concern to the occupational health community is the development of immune system dysfunction. Increased severity, frequency, and duration of upper and lower respiratory tract infections have been reported among welders. Specifically, multiple studies have observed an excess mortality from pneumonia in welders and workers exposed to metal fumes. Although several welder cohort and experimental animal studies investigating the adverse effects of welding fume exposure on immune function have been performed, the potential mechanisms responsible for these effects are limited. The objective of this report was to review both human and animal studies that have examined the effect of welding fume pulmonary exposure on local and systemic immune responses.

Effect of Activated Flux on the Microstructure and Mechanical Properties of 9Cr-1Mo Steel Weld Joint

Abstract: Tungsten inert gas (TIG) welding process is generally used to produce high quality weld joints of 9Cr-1Mo steel. However, there is limitation associated with the depth of penetration achievable in single pass autogenous welding. Specific activated flux has been developed in the present work to enhance the depth of penetration up to 6 mm in single pass by A-TIG welding. 9Cr-1Mo steel A-TIG weld joint using activated flux was made in single pass welding while the multipass TIG weld joint using modified 9Cr-1Mo filler wire was made in seven passes. The enhancement in depth of penetration during A-TIG welding process for this steel was attributed to arc constriction. The strength properties of the A-TIG weld joint was superior to that of the multipass TIG weld joint. The multipass TIG weld joint exhibited slightly improved impact toughness than the A-TIG weld joint in PWHT condition. Therefore, there was no degradation in the microstructure and mechanical properties of the weld joint produced by A-TIG welding...

Effect of zinc coatings on joint properties and interfacial reactions in aluminum to steel ultrasonic spot welding

Abstract: Dissimilar joining of aluminum to steel sheet in multimaterial automotive structures is an important potential application of ultrasonic spot welding (USW). Here, the weldability of different zinc-coated steels with aluminum is discussed, using a 2.5-kW USW welder. Results show that soft hot-dipped zinc (DX56-Z)-coated steel results in better weld performance than hard (galv-annealed) zinc coatings (DX53-ZF). For Al to hard galv-annealed-coated steel welds, lap shear strengths reached a maximum of ~80% of the strength of an Al-Al joint after a 1.0 s welding time. In comparison, welds between Al6111-T4 and hot dipped soft zinc-coated steel took longer to achieve the same maximum strength, but nearly matched the Al-Al joint properties. The reasons for these different behaviors are discussed in terms of the interfacial reactions between the weld members.

A Comparative Study on Direct and Pulsed Current Gas Tungsten Arc Welding of Alloy 617

Abstract: the aim of this article is to evaluate the mechanical and microstructure properties of Inconel 617 weldments produced by direct current electrode negative (DCEN) gas tungsten arc welding (GTAW) and pulse current GTAW. In this regard, the micro structural examinations, impact test and hardness test were performed. The results indicated that the joints produced by direct mode GTAW exhibit poor mechanical properties due to presence of coarse grains and dendrites. Grain refining in pulse current GTAW is reason of higher toughness and impact energy than DCEN GTAW. Further investigations showed that the epitaxial growth is existed in both modes that can strongly affect the mechanical behavior of the joints in heat affected zone (HAZ).

Ultrasonic-vibration assisted arc-welding of aluminum alloys

Abstract: The structure and hardness of the surface-welds and fusion-welds made on a 2017A aluminum alloy waveguide using the MIG and TIG methods with and without the participation of ultrasonic vibrations were examined. Cross-sections of the fusions and surface-welds thus obtained were observed in a microscope and the hardness distributions were determined. The aim of the study was to analyze the effects of the ultrasonic vibrations applied to the melted metal pool by a vibrating substrate which in our experiments was a waveguide. The interactions of the ultrasonic vibrations with the molten metal during its solidification and also with the heat-affected zone were examined at various phases of the vibration wave. The ultrasonic vibrations affected the structure of a weld. These changes are strongly depended on the wave phase.

Arc welding control method and arc welding device

Abstract: An arc welding control method performs welding of a work by alternately repeating a short-circuit period for short-circuiting a welding wire to a work and an arc period for regenerating an arc to perform arc discharge. The control is performed so that the welding output current immediately after regeneration of the arc is maintained higher than the welding output current immediately before the arc regeneration for a predetermined period of time.

Prediction of the weld pool geometry of TIG arc welding by using fuzzy logic controller

Abstract: The present paper describes fuzzy logic simulation of tungsten inert gas welding (TIG) process to predict the weldment macrostructure zones' shape profile characteristics. The prediction of the weld pool geometry together with the shape of the heat affected zone (HAZ) was accomplished taking into account of TIG welding process parameters such as arc traverse speed, welding current and arc length. Structural steel plates of 8 mm thickness were used for the experiments. Full factorial design of experiment methodology was followed while selecting the input process parameters (control factors). These control factors were having three levels. The TIG weld pool geometry profiles' (boundaries of thermal cycle zones) like the weld bead reinforcement, penetration and heat affected zones were the responses from the experiment. A series of 27 experiments were carried out for collecting the data. The experimental data were then used for building a fuzzy logic model to predict the effects of control factors on the responses. A graphical mapping scheme was employed for the graphical representation of the macrostructure zones' shape profiles including that of HAZ. The model was also tested for a number of test cases to establish it's adequacy. The fuzzy logic modeling technique employed in the present investigation can be used for online prediction of the TIG weldment shape profiles. The methodology adopted in the present investigation indicated adequacy of fuzzy logic model for predicting the TIG weld-pool geometry and HAZ.