Showing papers on "Arc welding published in 1985"

Metal transfer in arc welding as a varicose instability. I. Varicose instabilities in a current-carrying liquid cylinder with surface charge

Abstract: This paper considers, largely in the context of metal transfer in arc welding, the stability of a viscous, current-carrying fluid cylinder with surface charge. Simple expressions are obtained between the characteristics of instability growth and the dependence of these on 'process parameters'. For liquid metals it is found that viscous effects are negligible while electrostatic effects exert a stabilising influence and may have a number of interesting effects on stability (particularly at low wire currents).

An Implementation of Model-Based Visual Feedback for Robot Arc Welding of Thin Sheet Steel:

Abstract: Using conventional robots for metal/inert-gas (MIG) arc welding on thin (1- to 2-mm) sheet steel pressings is restricted by the difficulty of maintaining accurate fit-up and fixturing. Dimensional ...

Arc welding instruction monitor

Abstract: A monitor designed to aid in the instruction of electric arc welding. The device is electrically isolated from the welder arc voltage by an optical coupling device which provides an isolated output signal linearly proportional to either arc voltage or arc current. Audio alarms are triggered when the arc voltage is either too high or too low indicating arc lengths that are too low indicating arc lengths that are too long or too short to provide acceptable weld quality. A self test switch is included to demonstrate the upper and lower voltage alarm operation.

Metal transfer in arc welding as a varicose instability. II. Development of model for arc welding

Abstract: For pt.I see ibid., vol.18, p.1431 (1985). A model of metal transfer in open arc welding is developed which provides a framework for predicting the influence of welding parameters in steady and pulsed current welding. It is found possible to present results in terms of simple expressions which are in broad agreement with available observations. Considered here are aspects such as droplet evolution, detachment frequency and size, selection of pulse parameters, influence of electrostatic stress on transfer, drop dynamics and the relationship between balance of force approaches to transfer and the present instability model.

Method of producing weld overlay of austenitic stainless steel

Abstract: A method of producing a weld overlay on a ferrous base metal surface, by applying to the surface by electric arc welding a plurality of layers of an austenitic stainless steel filler of specific composition, and providing a flux which produces a substantially fully austenitic overlay at least in the uppermost layer. The overlay has improved machinability, metal-to-metal wear resistance and corrosion resistance, and the capability of work hardening.

Method of protecting eyes from welding rays in arc welding and apparatus therefor

Abstract: A method of protecting eyes from welding rays in arc welding and an apparatus therefor are disclosed which are capable of closing a filter plate over a period from right before the generation of arc welding rays to the termination of the generation to fully intercept the rays, to thereby effectively protect the eyes of an operator from the rays. The invention is constructed in a manner such that a controller carries out the on-off control of a voltage applied from a filter power source to a PLZT filter plate depending upon a signal supplied from a detection circuit thereto when the detection circuit detects a built-up current occurring in a welding current, to thereby carry out the actuation of the filter plate.

Nozzle for gas-shielded arc welding

Abstract: A nozzle for gas-shielded arc welding, having a support ring (4) engaged with a welding torch (2), a cylindrical nozzle member (6) engaging a support ring (4), and a means (8) for fixing the nozzle member (6) to the support ring (4). The nozzle member (6) is made of a heat-resisting non-conductive material, and spatter is rarely deposited on the nozzle member (6). The nozzle member (6) is formed so that it can be fixed under pressure to the support ring (4), and this member can be manufactured easily. This nozzle can be used effectively, especially, as a nozzle for carbon dioxide arc welding.

Microstructure and phase transformations in duplex 316 submerged arc weld metal, an ageing study at 700° C

Abstract: The transformation of metastableδ-ferrite has been studied in two duplex stainless steel weld metals. The kinetics and the nature of the equilibrium phases produced, depend upon the localized microsegregation of chromium and molybdenum to theδ-ferrite laths in the as-welded state. A transformation model is proposed which suggests that a longer term stability of theδ-ferrite may be achieved by alterations in the basic 316L composition used for the production of submerged arc weld metals.

Fiber optic seam tracking apparatus

Abstract: An arc welding head (13) suitable for robotic welding has a fiber optic bundle (12) and remotely located laser light source (24) which is imaged onto an end of the fiber optic bundle (12) and optically linked to substantially a single fiber of the fiber optic bundle (12). The light source (24) is then repetitively scanned across the coherent arrangement of fibers within the bundle (12), such that, a substantial portion of the transmitted light will be sequentially delivered to each individual fiber within a row of fibers and subsequently delivered to a workpiece (11). This arrangement provides a high signal to noise ratio making the laser light reflected from the workpiece (11) easily distinguishable from the optical "noise" generated by the welding arc flash.

Arc welding adaptive process control system

Abstract: A robotic arc welding system has an integrated vision sensor to image and analyze the weld scene in real time. The most effective weld puddle geometry discriminants for use in an adaptive feedback control, to assure full penetration welds, are weld puddle area and maximum width. The adaptive control system determines a puddle geometry error and a correction to nominal welding current to change the heat input to the weld pool, regulating a combination of puddle area and width, or only puddle area under some welding conditions, to control weld quality during the welding process. Arc voltage is modulated to reflect changes in welding current and maintain constant arc length.

Consumable electrode type pulse arc welding machine

Abstract: A consumable electrode type pulse arc welding machine is provided with means for controlling a welding output of the welding machine and the control means comprises a short-circuiting detector circuit for detecting the number of times of short-circuiting n occurring between an electrode wire and a weld part of a base metal at predetermined time intervals during a welding operation, a processing unit for calculating n d =n s -n, where n s is a preset number of short-circuiting times, and a control means for controlling a welding output of the welding machine by decreasing the welding arc voltage in accordance with the magnitude of n d , when n d is larger than zero, and by increasing the welding arc voltage in accordance with the magnitude of |n d |, when n d is smaller than zero.

GTA Weld Cracking-Alloy 625 to 304L

Abstract: Autogenous gas tungsten arc welds joining alloy 625 and 304L stainless steel were found to be susceptible to weld solidification cracking. Utilization of pulsed current GTA welding produced a higher sensitivity to solidification cracks than continuous current welding. Spot Varestraint tests show that the sensitivity of this dissimilar metal combination to cracking exists over the entire range of dilutions while the greatest sensitivity is in 304L stainless steel rich compositions. Auger electron spectroscopy indicates that segregation of sulfur and phosphorous to the interdendritic phase promotes the hot cracking.

Ultrasonic monitoring and control during arc fusion welding

Abstract: Ultrasonic examinations were first shown to be capable of detecting weld pools in 1978 using simple N.D.T. techniques and manual metallic arc welding. Further work, using submerged arc welding, demonstrated that the best technique was to employ shear waves operated from the upper plate surface. A control alogarithm relating beam path length to welding current was identified and used to control penetration depths to within 1mm of desired depth. Utilising ultrasonic beam spread has been shown also to monitor the seam immediately in front of the weld pool. Seam tracking simultaneously with penetration control is therefore possible from one piece of apparatus.

Arc welding power source with response delay compensating control

Abstract: An arc welding power source utilizing welding current from a two-step voltage conversion comprising a first target value setting circuit means for setting a first current target value V1 corresponding to a desired value of welding current, a current control circuit for controlling the welding current in accordance with the first current target value V1, a second target value setting circuit means for setting a second current target value V2 higher than the first current target value for satisfying a predetermined current waveform in response to an abrupt load variation, and a rapid operation current control circuit for controlling the welding current in accordance with the second current target value V2. Thus, even if the welding load tends to abruptly vary and the welding current tends to largely exceed the first current target value V1, the welding current is clipped by the second current target value V2 by the rapid operation current control circuit having a rapid response so as to maintain the actual welding current in the allowable V1 -V2 range.

Gas shielded arc welding method

Abstract: PURPOSE: To execute welding of good mechanical properties with high efficiency with extremely few defects by using a flux-cored wire contg. specific ratios of components to weld steel plates having non-cleaned surfaces and welding these steel plates in an independent gas of CO 2 , Ar or H 2 contg. a specific ratio of O 2 or a gaseous mixture composed thereof. CONSTITUTION: The flux-cored wire contg. 0.2% C, 0.3W1.5% Si, 0.5W3.0% Mn and 0.5W8.5% TiO 2 to improve the mechanical properties and appearance of weld zones A, B is used for welding A, B of the steel plates 1, 2 having the non-cleaned surfaces such as painted or rusted surfaces. Other elements to reinforce the weld zone, for example, Ni, Cr, etc. may be incorporated in the wire at the specific ratio or below and Bi, Pb, etc. contributing to the improvement of weldability may also be incorporated therein. The steel plates are welded by using such flux-cored wire in the independent gas of CO 2 , Ar or H 2 contg. ≥5vol.% O 2 or the gaseous mixture composed thereof. The welding of the good mechanical properties with the extremely few pits and blowholes is thus executed with good workability. COPYRIGHT: (C)1986,JPO&Japio

Arc welding power source

Abstract: PROBLEM TO BE SOLVED: To control plurality of small size high frequency transformers with the driving circuit of a single inverter, to easily make its handling operation and to make the installing space small by connecting inputting sides of plurality of transformers of an equal turn ratio of the inputting side and the outputting side to the outputting end of an inverter circuit, and installing a rectifying circuit at each outputting side of the transformers. SOLUTION: A high frequency alternating current voltage outputted from an inverter circuit 3 is stepped down to a voltage suitable for welding with high frequency transformers 4a, 4b, converted to direct current with rectifying circuits 21a, 21b, and it is supplied to terminals 23, 24. The high frequency transformers 4a, 4b are made to flow with the current so that the output voltages are made equally, respectively, because the high frequency transformers 4a, 4b have the same specification in this executing state, so 1/2 of welding current is made respectively to flow to the output side turn wire and the rectifying circuits 21a, 21b of the high frequency transformers 4a, 4b. In the high frequency transformer 4, the value of the inside impedance is dispersed caused on the dispersion of the production time, further, in a diode, the value of forward direction voltage step-down is dispersed, however, there is practically no problems.

Sensor-based control systems for arc welding robots☆

Abstract: Arc welding is one of the most important areas of application for industrial robots. In most manufacturing situations, uncertainties in dimensions of the part, geometry of the joint, and the welding process itself make the use of sensors essential to maintaining weld quality. In this paper three types of control systems for arc welding robots are described: (1) tracking systems for centering the weld puddle over the joint, (2) weld process controls for maintaining proper seam width and penetration, and (3) supervisory controls for sequencing welding operations. These control functions have been implemented successfully in production using a computer vision sensor integrated into the welding torch. Experimental results are presented demonstrating the capabilities of the system.

Vision processing and control of robotic Arc welding system

Abstract: A microprocessor-based control system is presented for a Gas Tungsten Arc Welding (GTAW) process to join thin sheet metal parts. The system uses a welding robot, a vision sensor, and an image processor to control the welding torch in real-time. A vision-processing algorithm is developed to compute weld puddle geometry parameters from the noisy image of the molten pool. The weld quality is controlled by regulation of puddle area, puddle width, arc length, and puddle center over the joint. Experimental results indicate successful operation of the control system with heat sink disturbances in the weld fixture.

Underwater arc welding

Abstract: Portable welding apparatus for use in underwater arc welding comprising a housing through whose wall extends a welding gun. The housing has an aperture for fitment over an item to be welded to a structure and the housing has a gas inlet for evacuation of water from the housing in use. The apparatus preferably includes a rotatable housing portion on a fixed base so that welding can be performed around items which are contained wholly within the housing, thereby ensuring a dry environment for the well under water.

Method of controlling multi-layer welding

Abstract: In the multi-layer welding of a joint of two pieces of metal to be welded by arc welding, the proper number of passes and the desired tracing positions of a welding torch for each layer are automatically established during the welding of the preceding layer. The welding torch is subjected to a Y-axis control so as to maintain constant the arc voltage or current during the welding and simultaneously the torch is caused to weave in the direction of an X-axis within the groove. The tracing of the groove by the torch is accomplished by controlling the weaving turning positions of the torch in accordance with the X-axis and Y-axis direction displacement data of the torch and the torch displacements in the X-axis direction are compared with a predetermined value thereby determining the proper number of passes to be made in the welding of the next layer.

Method of welding nitrogen-containing alloys

Abstract: A method for improving the weld strength, structure and crevice corrosion resistance of nitrogen-containing alloy weldments by adding nitrogen to the inert gas used for shielding during the welding operation.

Time resolved optical spectra from MIG welding arc ignitions

Abstract: Optical radiation from MIG (GMAW) welding arc ignitions has been measured with a rapid scan spectrometer. The time resolved spectral measurements reveal a substantial overshoot of ultraviolet radiation during the ignition phase of a 200 A aluminum arc. Calculations which follow the ACGIH guidelines show that, at a welding current of 300 A, the unprotected eye at a distance of 0.5 m may suffer a “flash” after the reception of radiation from only one ignition.

Spectra of optical radiation from welding arcs.

Abstract: It is important to determine spectra of optical radiation from light sources at workplaces, because they usually emit lights of various wavelengths simultaneously and these differ in their degree of harmfulness. Spectra of optical radiation (wavelength range: 200-1, 000 nm) from the arc of various arc welding processes were measured, using a multichannel detector system. For each process, a stable relative spectrum (a shape of the spectrum) was obtained in spite of the fluctuations in intensity. The relative spectrum is determined mainly by the welding material, such as steel or aluminum, regardless of the other parameters. Especially, it is independent of the diameter of wire, arc current and arc voltage, which have an influence only on the absolute intensity of the radiation.

Process and apparatus for partially or fully mechanised inert gas (protective gas) joint welding

Abstract: The invention starts from the known WIG or plasma welding process using an inert gas, with weld (filler) material being supplied as a welding rod (wire). According to the invention, the welding rod is introduced into the torch in such a way that it is located in the arc between the end of the non-consumable electrode and the workpiece and accordingly passes in an electroless dripping manner into the arc. Accordingly, the torch is equipped with a welding rod feed, by means of which the rod can be introduced into the nozzle channel of the torch and accordingly into the arc.

EXPOSURE OF WELDERS TO FUMES, Cr, Ni, Cu AND GASES IN DUTCH INDUSTRIES

Abstract: The exposure of welders in Dutch industries to total particulate, chromium, nickel and copper fume during the welding of unalloyed, stainless and high alloyed steels has been investigated. The exposure to the gases NO2, NO and ozone is also discussed. The results are presented in tables and graphs. The correlation between the arc-time factor and the welding fume concentration in the breathing zone appeared to be bad MMA-welding fumes of stainless steel contain mainly soluble hexavalent chromium. During MIG and TIG welding the fumes contain chromium which was insoluble in water and not hexavalent. The nickel was insoluble in water in all three processes. In comparison with the Dutch occupational health standards, it appears that the dust exposure is often higher than the limit value of 5 mg m3 in M MA and gas-shielded arc welding. The exposure to chromium is usually higher than the standard of 0.05 mg m 3 lor hexavalent chromium and the standard o[0.5 mg m-3 lor total chromium in MMA welding of stainless steel, and the exposure to copper fumes during welding of copper is usually higher than the standard of 02 mg m3. Among the gaseous contaminants NO2, NO and ozone, only ozone with MIG welding of aluminum gives concentrations in the breathing-zone exceeding the standat'd of 0.2 mg m3(0.1 ppm).