Showing papers on "Arc welding published in 2001"
TL;DR: In this article, a generation chamber and sampling system was designed to characterize aerosols from a popular welding system that utilized either gas metal arc welding or flux cored arc welding techniques and the results demonstrated that the welding alloy had a marked effect on the particle size distribution, morphology and chemical aspects of the resultant fume.
198 citations
Patent•
20 Sep 2001
TL;DR: In this article, a flux-cored wire which is excellent in welding activity in all position welding, and excellent in the strength and low-temperature toughness of weld metal as welded (AW) and after PWHT is presented.
Abstract: Provided is a flux-cored wire which is excellent in welding activity in all position welding, and excellent in the strength and low-temperature toughness of weld metal as welded (AW) and after PWHT. The flux-cored wire contains the proper amount of C, Si, Mn, Ni, B, Mg, V, Ti oxide, metal Ti, Al oxide, metal Al, Si oxide, metal fluoride, P and Nb.
136 citations
TL;DR: In this article, the peak temperatures attained at different points during deposition of weld beads in stainless steel and low carbon steel weld pads were compared, and the residual stress patterns developed, the change in the peak tensile stress with the deposition of welding beads and the relation between peak temperatures and residual stresses in the weld pads are discussed.
134 citations
TL;DR: In this article, the effect of vacuum on weld penetration and porosity formation was investigated in high-power cw CO2 and YAG laser welding, and it was shown that no porosity was present in the materials welded at lower pressures.
Abstract: The effect of vacuum on weld penetration and porosity formation was investigated in high-power cw CO2 and YAG laser welding. It was consequently confirmed in welding with both lasers that the penetration was slightly deeper in aluminum alloys and austenitic stainless steel with a decrease in the ambient pressure. It was also revealed that no porosity was present in the materials welded at lower pressures. The reason for no porosity formation in vacuum was examined by observing keyhole behavior, bubble and porosity formation situation, and liquid flow in the molten pool during high-power YAG laser welding under various conditions through the microfocused x-ray real-time observation system. It was confirmed in the coaxial Ar or He shielding gas that a lot of bubbles were generated near the bottom part of the molten pool from the tip of a fluctuated keyhole and resulted in large pores. On the other hand, under the vacuum conditions, no bubbles were formed in the melt pool from the keyhole, although the middl...
126 citations
Patent•
20 Nov 2001
TL;DR: In this article, a monitor for an electric arc welder as the welder performs a selected arc welding process by creating actual welding parameters, such as arc current and arc voltage, between an advancing welding wire and a workpiece, where the process involves an arc and is defined by a series of rapidlyrepeating wave shapes constituting a weld cycle with a cycle time.
Abstract: A monitor for an electric arc welder as the welder performs a selected arc welding process
by creating actual welding parameters, such as arc current and arc voltage, between an advancing
welding wire and a workpiece, where the process involves an arc and is defined by a series of rapidly
repeating wave shapes constituting a weld cycle with a cycle time, the wave shapes are each
segmented into time states having command signals corresponding to the actual parameters and a
time duration. The monitor selects a specific wave shape state, reads one of the actual parameters,
compares the actual read parameter with a function of the command signal corresponding to the
actual parameter, and uses the comparison to generate a characteristic of the welding process during
the selected state.
121 citations
TL;DR: In this paper, the authors reviewed the development of underwater wet welding processes over the past 25 years and developed welding consumables with improved control over diffusible hydrogen and porosity.
Abstract: Developments in underwater wet welding processes over the past 25 years are reviewed. Shielded metal arc welding with rutile base coated electrodes is still by far the most common wet welding process in use. Research and development of wet welding electrodes has led to improvements in the control of hydrogen content, porosity, chemical composition, and microstructure of the weld metal. Additional work is required to develop welding consumables with improved control over diffusible hydrogen and porosity. Development of techniques such as temper bead welding has allowed successful wet welding repairs on steels having carbon equivalents greater than the traditional limit of 0.40. Alternative wet welding processes such as flux cored arc welding and friction welding are under development, but have yet to become widely accepted.
102 citations
Patent•
22 Aug 2001
TL;DR: An electric arc welder powered by a plurality of liquid organic fuel cells is described in this article, where the fuel cells are stacked together to produce the desired arc voltage and current between an electrode and the workpiece.
Abstract: An electric arc welder powered by a plurality of liquid organic fuel cells The fuel cells use a methanol/water mixture as the organic feed The fuel cells produce carbon dioxide as a reactive product which is used an a shielding gas during the arc welding process The fuel cells are stacked together to produce the desired arc voltage and current between an electrode and the workpiece The arc welder includes a welding current to control the current wave shape through the electrode and to control or increase the voltage through the electrode
91 citations
TL;DR: In this paper, simulations of flow fields in the weld pool resulting from different temperature dependencies of the coefficient of surface tension are presented, and the effect of the temperature-dependent coefficient is identified as one of the primary driving forces of the liquid melt.
Abstract: In welding, the resulting weld-seam geometry may vary significantly although using constant process parameters and steels with the same material number. One likely reason for this are small variations in the concentration of sulfur, phosphorus, oxygen, and other chemical elements that are well within the tolerance of the standard of a specific alloy. These substances act as surfactants and even marginal changes strongly effect the temperature-dependent coefficient of surface tension. In simulations of conventional electric arc welding and laser heat conduction welding, the effect of the temperature-dependent coefficient of surface tension (Marangoni effect) has been identified as one of the primary driving forces of the liquid melt. In laser deep penetration welding simulations this effect has been widely neglected, so far. In this contribution, simulations of flow fields in the weld pool resulting from different temperature dependencies of the coefficient of surface tension are presented. The simulations...
85 citations
TL;DR: In this paper, a sensor to detect the state of the keyhole for keyhole process control has been proposed and developed, which measures the electrical effect of the plasma cloud generated during keyhole plasma arc welding.
Abstract: Keyhole plasma arc welding achieves much deeper penetration than do all other existing arc welding processes. Because of its ability to penetrate thicker material, the control of the keyhole in plasma arc welding becomes critical. From an analysis of the physical process, a sensor to detect the state of the keyhole for keyhole process control has been proposed and developed. This sensor measures the electrical effect of the plasma cloud generated during keyhole plasma arc welding. It is found that the plasma cloud, which rapidly decreases to zero upon establishment of the fully penetrated keyhole, can be used to detect the state of the keyhole reliably. The effectiveness of the proposed sensor for detecting the keyhole state has been verified during pulse keyhole plasma arc welding.
70 citations
TL;DR: An alternating current pulsed metal inert gas (MIG) welding power source has been developed for welding thin sheets of aluminium alloys and the process features are investigated in this paper, which successfully counteract the problem of burnthrough in welding of thin sheet joints and greatly improve the bridging ability for wide gap joints.
Abstract: An alternating current (ac) pulsed metal inert gas (MIG) welding power source has been developed for welding thin sheets of aluminium alloys and the process features are investigated. Advantages such as high wire melting coefficient, low heat input, shallow penetration, and increased reinforcement height are obtained at high values of electrode negative ratio (ratio of electrode negative current integration to electrode negative plus electrode positive current integration over one pulse cycle). These features successfully counteract the problem of burnthrough in welding of thin sheet joints and greatly improve the bridging ability for wide gap joints. Thin sheet joints can be welded at high speed and with low distortion. By integrating the present welding power source with a welding robot, welding process and current waveform parameters can be defined by key operations in the teach pendant. It is possible to switch between welding processes such as ac pulsed MIG, direct current (dc) pulsed MIG, lo...
67 citations
Patent•
04 Dec 2001TL;DR: In this article, a control method for arc welding is proposed, where position control of an electrode or a torch is performed while adjusting welding conditions on the basis of optical information obtained from arc light generated during an arc welding process.
Abstract: A control method for arc welding wherein position control of an electrode or a torch is performed while adjusting welding conditions on the basis of optical information obtained from arc light generated during an arc welding process. Illuminance, which forms the optical information obtained from the arc light, has a certain mutual relationship with the arc length or the torch height, so that the weld control is accomplished based on the illuminance. The control method includes a step of comparing illuminance with reference information based on the mutual relationship, and a step of adjusting the welding conditions on the basis of a result of comparison.
TL;DR: In this article, a dynamic force balance model was proposed by introducing the inertial force to predict metal transfer in arc welding, where the dynamics of the pendant drop was modelled as a linear time-varying second-order system and the spring constant and electromagnetic force were calculated for the ellipsoidal drop.
Abstract: A dynamic force balance model is proposed by introducing the inertial force to predict metal transfer in arc welding. The dynamics of the pendant drop is modelled as a linear time-varying second-order system and the spring constant and electromagnetic force are calculated for the ellipsoidal drop. Two methods are employed to estimate the spring constant: numerical calculation for the ellipsoidal drop and a closed-form equation for the spherical drop at equilibrium. The inertial force is produced by drop oscillation and it is applied to the drop-detaching criterion. Since the inertial force reaches half the electromagnetic force at the transition current, it influences drop detachment with current increase. The proposed dynamic force balance model predicts the resonance frequency and detaching drop size with reasonable accuracy.
TL;DR: This work aims at improving the measurement accuracy of arc length using the spectrum of are light at a particular wavelength during gas tungsten arc welding (GTAW) with argon shield by studying effects of welding parameters on spectral distributions.
Abstract: During arc welding, the arc heats and melts the workpiece as heat flux. When the welding current is given, the distribution and the intensity of the heat flux are determined by the length of the are. The measurement and control of the are length are fundamental in robotic and automated welding operations. Length of welding arc determines the distribution of the arc energy and thus the heat input and width of the weld. This work aims at improving the measurement accuracy of arc length using the spectrum of are light at a particular wavelength during gas tungsten arc welding (GTAW) with argon shield. To this end, effects of welding parameters on spectral distributions were studied. To verify the effects of base metal and arc length, the arc column was also sampled horizontally as Layers for spectral analysis. Results show that spectral lines of argon atoms are determined by are length, independent of welding parameters other than the current. Based on these findings, a compact arc light sensor has been designed to measure the arc length with adequate accuracy. A closed-loop arc length control system has been developed with the proposed sensor.
Patent•
28 Feb 2001
TL;DR: In this paper, a real-time control signal (224) was generated for an electric arc welding process having welding voltage and welding current, and the derivative value representing the desired control signal was derived by dividing the welding voltage difference between the first and second times by the welding current difference.
Abstract: A method of generating a real time control signal (224) for use in an electric arc welding process having welding voltage and welding current, said method comprising: measuring the welding voltage and welding current at a first time (200), momentarily changing either the welding voltage or welding current by less than about 10 %, then measuring the welding voltage and the welding current after the change at a second time (204), determining the welding voltage difference between the first time and the second time (220), determining the welding current difference between the first time and the second time (220), producing a derivative value representing the desired control signal by dividing the welding voltage difference between the first and second times by the welding current difference between the first and second times (220) and generating the control signal (224) by the derivative value.
Patent•
12 Sep 2001
TL;DR: In this paper, a flux-cored wire for gas-shielded arc welding is described, which is filled with a flux that satisfies the following conditions and has excellent performance in welding mild steel and high-tensile steel.
Abstract: (57) [Summary] [PROBLEMS] A specific correlation formula is formed between specific components such as K 2 O, Na 2 O, and SiO 2 , which are composed of metals and oxides such as Ti, Si, Mg, K, and Na. The present invention provides a flux-cored wire for gas shielded arc welding, which is filled with a flux that satisfies the following conditions and has excellent performance in welding mild steel and high-tensile steel. The flux-cored wire for gas shielded arc welding according to the present invention is based on the total weight of a wire including a metal sheath as an outer shell, and is calculated as TiO 2 in terms of Ti and Ti oxide: 3. 0 to 8.0 wt%, Si and Si oxide in terms of SiO 2 : 0.5 to 2.0 w t%, metal Mn and alloy in terms of Mn: 1.5 to 3.5 wt%, and C: 0.02 to 0.10 wt%, Mg and Mg oxide in terms of MgO: 0.5 to 1.5 wt%, sum of compounds of Na 2 O and K 2 O: 0.2 wt% or less, ZrO Zr and Zr oxides at 2 converted value: 0.1-0.5% and, Al 2 O 3 in terms of values of Al and Al oxide: 0.2 to 0.8% and made of the same time, It is characterized by being within the range of the following expressions 1 and 2. (Formula 1) 0.1 ≦ (2K 2 O + Na 2 O) / SiO 2 ≦ 0.3 (Formula 2) 1.6 ≦ (FeO + MnO + MgO) / (SiO 2 + Al 2 O 3 + 0.4TiO 2 ) ≦ 2.1
Patent•
27 Feb 2001
TL;DR: In this paper, a hot wire welding method and system rely upon a welding torch with a nonmelting electrode, a melting metal filler wire that is fed into a weld puddle created by welding arc, a microprocessor controller for controlling (i) current of the main welding arc and feed speed, and (iii) hot wire current for heating the filler wire.
Abstract: A hot wire welding method and system rely upon a welding torch with a non-melting electrode, a melting metal filler wire that is fed into a weld puddle created by welding arc, a microprocessor controller for controlling (i) current of the main welding arc, (ii) filler wire feed speed, and (iii) hot wire current for heating the filler wire. The method and system also rely upon a main welding power supply for supplying the main welding arc and a secondary DC supply for supplying the hot wire current. The hot wire current is automatically controlled by the microprocessor to supply the correct amount of current to the filler wire in response to changes in wire feed speed.
Patent•
22 May 2001
TL;DR: In this paper, a power supply connectable to a source of AC line voltage for AC electric arc welding by an AC arc current across a welding gap between an electrode and a workpiece, the power supply comprises a high capacity transformer that converts said line voltage to an AC output voltage, and a rectifier that converts the output voltage to a DC voltage between a positive terminal and a common terminal at generally zero volts.
Abstract: A power supply connectable to a source of AC line voltage for AC electric arc welding by an AC arc current across a welding gap between an electrode and a workpiece, the power supply comprises a high capacity transformer that converts said line voltage to an AC output voltage, and a rectifier that converts the AC output voltage to a DC voltage between a positive terminal and a common terminal at generally zero volts and a negative terminal and the common terminal. The power supply has a first switch that connects the positive terminal to the common terminal across the gap when a gate signal is applied to the first switch, a second switch for connecting the negative terminal to the common terminal across the gap when a gate signal is applied to the second switch and a pulse width modulator operated for generating pulses at a frequency of at least about 18 kHz. A logic network has a first circuit for directing the pulses to the first switch for a first time, a second circuit for directing the pulses to the second switch for a second time and a controller to alternately operate first and second circuits to create AC arc welding current.
Patent•
08 Oct 2001TL;DR: In this paper, a 6-axis robot, a camera and a robot controller/vision processor are applied to a wire-fed plasma welding process to identify the part, construct a weld path based on the part's individual contour, and calculate a trajectory (with or without sinusoidal oscillation) for the robot arm to follow.
Abstract: A gas turbine component can be refurbished and/or repaired with an arc welding process that is used in conjunction with a 6-axis robot, a camera and a robot controller/vision processor. Applied to a wire fed plasma welding process, the vision system identifies the part, constructs a weld path based on the part's individual contour, and calculates a trajectory (with or without sinusoidal oscillation) for the robot arm to follow.
Patent•
21 Nov 2001
TL;DR: In this article, the authors proposed a spectrum expansion communication part which transmits and receives a control signal by a spectrum diffusion communication method between the wire feeding device WSR2 and the welding power supply WER2 via a power cable.
Abstract: PROBLEM TO BE SOLVED: To solve the problem that a workability is poor and a control cables are likely to cause disconnection because bundled and integrated control wires must be moved together with a wire feeding equipment which is separated from a welding power supply, when transported. SOLUTION: The consumable electrode type arc welding equipment is a type in which an output control power supply PS for a standby welding period is provided in a welding power supply WER2, a control power supply SP incorporating a feeding device which inputs a control voltage from a power cable is provided in a wire feeding device WSR2, a spectrum expansion communication part which transmits and receives a control signal by a spectrum diffusion communication method between the wire feeding device WSR2 and the welding power supply WER2 via a power cable. The control voltage, which the control power supply SP incorporating a feeding device inputs, is supplied from the output control power supply PS for a standby welding period during a welding standby period, supplied from an arc voltage during a welding period, and supplied from a no-load voltage of the welding power supply WER2 during a period of a no-load voltage output. COPYRIGHT: (C)2003,JPO
TL;DR: In this article, the purpose of the filler material is to compensate for the differences in chemical and physical properties of both materials, and the welded joints were subjected to deep drawing.
Journal Article•
TL;DR: Genetic algorithms can determine near-optimal settings of welding process parameters within a large search space with relatively few experiments as mentioned in this paper, but they require a large number of experiments and are computationally expensive.
Abstract: Genetic algorithms can determine near-optimal settings of welding process parameters within a large search space with relatively few experiments.
Patent•
29 Jan 2001
TL;DR: In this article, a method for preventing collisions between robots by causing a first robot to stop or pause so that a second robot may safely pass by or perform a specified operation is presented.
Abstract: A method for preventing collisions between robots by causing a first robot to stop or pause so that a second robot may safely pass by or perform a specified operation. Once the second robot has completed its operation then the first robot is allowed to resume operation. Each robot automatically stops when it reaches a certain point in its job. The robots communicate with a central controller which allows the robots to resume operation when the central controller has determined that all of the robots have reached their respective correct positions. This prevents collisions between robots which are operating in the same area, especially those robots operating on the same workpiece. This method works with existing robot welders, does not require modifications to the robots, and does not require expensive spatial analysis computer programs, which may not even be available for the type of processor used in a particular robot. The present invention also provides a method for specifying a compartment entry point for a welding operation based upon data provided from a CAD program. The present invention also provides a method for automatically determining the starting and ending coordinates of a weld using a touch-sensing capability of the robot. The present invention also provides a method for automatically tracking the joint for a welding seam by periodically measuring the coordinates of the components by using the touchsensing feature of the robot. The present invention also provides a method for automatically determining the position of a torch to provide for an optimum angle of attack for a welding operation based upon data, such as beam height and flange overhang, provided from a CAD program. The present invention also provides a method for automatically tracking the joint for a welding seam by weaving (dithering) the torch along the desired path, measuring the arc welding current at peak deviations from the travel path, and comparing the measured current on the two different sides of the weld to determine whether the torch is on the seam. The present invention also uses this method to automatically track the edge of a component for applying a welding bead to the edge of the component. The present invention also provides for automatically selecting a welding program from a standard set of welding programs based upon data from a CAD program.
TL;DR: In this paper, an investigation has been conducted of the weldability of 0.2mm-thick sheet aluminum, brass, and copper in small-scale resistance spot welding using a high-frequency inverter and a capacitor-discharge power supply.
Abstract: An investigation has been conducted of the weldability of 0.2-mm-thick sheet aluminum, brass, and copper in small-scale resistance spot welding using a high-frequency inverter and a capacitor-discharge power supply. The results have been compared to those of previous investigations using a line-frequency alternating current power supply. The effects of electrode materials and process parameters on joint strength, nugget diameter, weld-metal expulsion and electrode-sheet sticking were studied. This work has also provided practical guidelines for selection of power supplies, process parameters (welding current/pulse energy, welding time/pulse width, electrode forces, etc.) and electrode materials for small-scale resistance spot welding of thin sheet aluminum, brass and copper.
TL;DR: A novel technique, that combines both FLC and neural network (NN) techniques is presented to control the gas tungsten arc welding (GTAW) process, verified to be highly effective in an arc-welding process in which the welds bead width is regulated.
01 Nov 2001
TL;DR: In this article, a new deposition process for directly building cylindrical parts of the 5356 aluminium alloy with variable polarity gas tungsten arc welding (VPGTAW) is presented.
Abstract: This paper presents a new deposition process for directly building cylindrical parts of the 5356 aluminium alloy with variable polarity gas tungsten arc welding (VPGTAW). The relationship between the geometric sizes of the deposited layer and the welding parameters is investigated. A machine vision sensor is used to monitor and control the arc length that is a key welding parameter in the achievement of a uniform deposition. By optimizing the depositing speed and the thickness of the depositing layer, there is no need for a cooling system to cool the part. Three-dimensional parts with diVerent wall thicknesses and diVerent shapes are successfully obtained. The surfaces of the deposited parts are smooth and uniform.
TL;DR: It was found that UVR from CO(2) arc welding is actually hazardous for the eye and skin, and the effective irradiance is inversely proportional to the square of the distance from the arc, is strongly dependent on the direction of emission from the arcs, and tends to increase with welding current.
Abstract: The arcs associated with arc welding emit high levels of ultraviolet radiation (UVR), and this often causes acute injuries in the workplace, particularly photokeratoconjunctivitis. It is important to know the level of UVR emitted by arc welding under various conditions, as this information will help in evaluating potential UVR hazards in welding workplaces and taking protective measures against it. In this study, the ACGIH effective irradiance for UVR was measured experimentally for CO2 arc welding in order to evaluate its UVR hazards. A welding robot was used in the experiment in order to realize reproducible and consistent welding operations. The effective irradiance at 1 m from the arc was in the range 0.28-7.85 W/m 2 (28-785 |xW/cm 2 ) under the study conditions. The corresponding permissible exposure time per day is only 4-100 s, suggesting that UVR from CO2 arc welding is actually hazardous for the eye and skin. It was found that the effective irradiance is inversely proportional to the square of the distance from the arc, is strongly dependent on the direction of emission from the arc with a maximum at 50-60° from the plate surface, and tends to increase with welding current. © 2001 British Occupational Hygiene Society. Published by Elsevier Science Ltd. All rights reserved
TL;DR: In this paper, the history of the use of hydrogen as a combustible or shielding gas in welding is discussed, and the advantages of using hydrogen in gas processes are discussed and compared.
TL;DR: A degree of relationship between predicted and measured fume formation rates is demonstrated but the model does not at this stage provide a reliable predictive tool.
Abstract: Prediction of fume formation rate during metal arc welding and the composition of the fume are of interest to occupational hygienists concerned with risk assessment and to manufacturers of welding consumables. A model for GMAW (DC electrode positive) is described based on the welder determined process parameters (current, wire feed rate and wire composition), on the surface area of molten metal in the arc and on the partial vapour pressures of the component metals of the alloy wire. The model is applicable to globular and spray welding transfer modes but not to dip mode. Metal evaporation from a droplet is evaluated for short time increments and total evaporation obtained by summation over the life of the droplet. The contribution of fume derived from the weld pool and spatter (particles of metal ejected from the arc) is discussed, as are limitations of the model. Calculated droplet temperatures are similar to values determined by other workers. A degree of relationship between predicted and measured fume formation rates is demonstrated but the model does not at this stage provide a reliable predictive tool.
TL;DR: In this paper, a simple apparatus for the study of tungsten inert gas (TIG) welding arcs is described permitting data collection over short time periods for operating currents in the range 50-150 A.
Abstract: It is well known that the use of Langmuir probes in `high' pressure plasmas (atmospheric and above) is extremely difficult due to the high degree of collisionality. In addition, electric arcs used in industry are highly non-homogeneous. In particular the degree of ionization varies from zero at the arc edges to values close to full ionization near the axis. Existing probe theories are therefore inappropriate. The `traditional' use of the characteristic curve for arc temperature and particle density mapping is time consuming and also leads to errors due to the collisional nature of the discharge. Existing probe theories are examined with respect to the application at high pressure and in this, the first of a series of papers, an interpretation based on different assumptions is presented. A simple apparatus for the study of tungsten inert gas (TIG) welding arcs is described permitting data collection over short time periods (~0.1 s) for operating currents in the range 50-150 A. Difficulties encountered with probe applications are discussed highlighting the need for further theoretical developments. The axial electric field is given by the derivative of the measured potential with respect to the axial position and shown to be in agreement with previous estimations. Results are discussed with reference to the sparse previous publications concerned with high pressure arc plasmas.
Patent•
26 Jan 2001TL;DR: In this article, a system for controlling an arc welding system operating in a dip transfer mode is described, where the control system is operative to control the current output from a power source so as to apply a current pulse during the arcing phase of the welding system.
Abstract: A system 11 for controlling an arc welding system 10 operating in a dip transfer mode is disclosed. The control system is operative to control the current output from a power source so as to apply a current pulse during the arcing phase of the welding system which is operative to form a molten droplet on the electrode of the welding torch 13 which is within a predetermined threshold size range, The control system 11 is then operative to clamp the current output from the power source 12 so that bridge rupturing occurs at relatively low current levels to thereby significantly reduce spatter during bridge rupturing.