Showing papers on "Arc welding published in 1995"

Thermal efficiency of arc welding processes

Abstract: A study was conducted on the arc and melting efficiency of the plasma arc, gas tungsten arc, gas metal arc, and submerged arc welding processes The results of this work are extended to develop a quantitative method for estimating weld metal dilution in a companion paper Arc efficiency was determined as a function of current for each process using A36 steel base metal Melting efficiency was evaluated with variations in arc power and travel speed during deposition of austenitic stainless steel filler metal onto A36 steel substrates The arc efficiency did not vary significantly within a given process over the range of currents investigated The consumable electrode processes exhibited the highest arc efficiency (084), followed by the gas tungsten arc (067) and plasma arc (047) processes Resistive heating of the consumable GMAW electrode was calculated to account for a significant difference in arc efficiency between the gas metal arc and gas tungsten arc processes A semi-empirical relation was developed for the melting efficiency as a function of net arc power and travel speed, which described the experimental data well An interaction was observed between the arc and melting efficiency A low arc efficiency factor limits the power delivered to the substrate which, in turn, limits the maximum travel speed for a given set of conditions High melting efficiency is favored by high arc powers and travel speeds As a result, a low arc efficiency can limit the maximum obtainable melting efficiency

Apparatus and method for computerized interactive control, measurement and documentation of arc welding

Abstract: An apparatus and method for computerized interactive control, measurement and documentation of are welding utilizing a single power source that facilitates continuous precision welding Operational interactivity between the welding operations and the workpiece operations, in connection with predetermined optimum welding operational parameters, provides contemporaneous feedback of critical welding operational parameters to the welding operator, producing an alarm if welding is attempted outside a first predetermined range of deviation from optimum welding operational parameters and temporarily interrupting power to the welding operation if welding is attempted outside of a second predetermined range of deviation from the optimum welding operation parameters A complete log of the welding operational parameters is stored for subsequent retrieval and display, providing training and evaluation of welding operators as well as verification of compliance with required welding practices and procedures Methods of performing continuous precision welding, facilitating temperbead welding, training and qualifying welders for such operations and verifying practice and procedure compliance are available utilizing the above-described apparatus

Impact toughness of C-Mn steel arc welds : Bayesian neural network analysis

Abstract: Charpy impact toughness data for manual metal arc and submerged arc weld metal samples have been analysed using a neural network technique within a Bayesian framework. In this framework, the toughness can be represented as a general empirical function of variables that are commonly acknowledged to be important in influencing the properties of steel welds. The method has limitations owing to its empirical character, but it is demonstrated in the present paper that it can be used in such a way that the predicted trends make metallurgical sense. The method has been used to examine the relative importance of the numerous variables thought to control the toughness of welds.MST/3115

A robust method for vision-based seam tracking in robotic arc welding

Abstract: This paper presents a robotic seam tracking system which is aimed at achieving robustness against some welding noises such as arc glares, welding spatters, fumes etc. In particularly, a syntactic analysis is used to improve the extraction reliability of the joint features. The joint features thus obtained are used to extract the 3-dimensional information of the weld joint and then achieve the robot path correction. To show the performance of the developed system, a series of experiments on joint feature detection and robotic seam tracking are conducted for different types of weld joints. The results exhibit that the system is very robust to various welding noises as well as variations in appearance of weld joint and workpiece.

Method and apparatus for controlling and simultaneously displaying arc welding process parameters

Abstract: A system (and method) of controlling and simultaneously displaying arc welding torch parameters includes a power supply for supplying weld voltage and current to the torch in accordance with demand signals from a computer. The computer also supplies a demand motor speed to a motor for controlling the travel speed of the torch electrode relative to a workpiece or the fed rate of a filler wire to the weld area. The actual values of the weld voltage/current and the motor speed are fed back to the computer and displayed on a video color display in separate colors and in real time to enable on operator to readily correlate the actual with the demand parameter values. The position of the electrode relative to the workpiece is also fed back to the computer for presentation on the video display. In addition, deviations of the individual actual parameter values from acceptable tolerance limits are highlighted on the display.

Heat and metal transfer in gas metal arc welding using argon and helium

Abstract: This article describes a theoretical investigation on the arc parameters and metal transfer in gas metal arc welding (GMAW) of mild steel using argon and helium shielding gases. Major differences in the predicted arc parameters were determined to be due to large differences in thermophysical properties. Various findings from the study include that an arc cannot be struck in a pure helium atmosphere without the assistance of metal vapor, that a strong electromagnetic cathode force affects the fluid flow and heat transfer in the helium arc, providing a possible explanation for the experimentally observed globular transfer mode and that the tapering of the electrode in an argon arc is caused by electron condensation on the side of the electrode.

The particle size distribution, density, and specific surface area of welding fumes from SMAW and GMAW mild and stainless steel consumables

Abstract: Particle size distributions were measured for fumes from mild steel (MS) and stainless steel (SS); shielded metal arc welding (SMAW)and gas metal arc welding (GMAW) consumables. Up to six samples of each type of fume were collected in a test chamber using a micro-orifice uniform deposit (cascade) impactor. Bulk samples were collected for bulk fume density and specific surface area analysis. Additional impactor samples were collected using polycarbonate substrates and analyzed for elemental content. The parameters of the underlying mass distributions were estimated using a nonlinear least squares analysis method that fits a smooth curve to the mass fraction distribution histograms of all samples for each type of fume. The mass distributions for all four consumables were unimodal and well described by a lognormal distribution; with the exception of the GMAW-MS and GMAW-SS comparison, they were statistically different. The estimated mass distribution geometric means for the SMAW-MS and SMAW-SS consumables we...

Flux-cored wire for gas shield arc welding

Abstract: PROBLEM TO BE SOLVED: To provide a flux-cored wire for gas shield arc welding used for fillet welding, that good plasma resistance, bead shape, outward appearance and detachability of slag are obtd. even in the case of using the high speed horizontal fillet welding under high current welding condition, and a flux-cored wire for whole position welding, that the weldability in various weldings, is good including the metal dripping resistance in the vertical welding even in the case of using in the wide welding range containing the high current zone. SOLUTION: Relating to the flux-cored wire for gas shield arc welding constituted by filling the flux in a steel-made outer shell, an iron base Si-Mn alloy powder as the flux, consisting of, by weight, 0.40-1.20% C, 5-12% Si, 19-42% Mn and the balance Fe so as to satisfy Si >=11.89-2.92 C-0.077 Mn and having =1.0% based on the whole wt. of the wire, and further, 2.0-7.0% TiO2, 0.2-1.5% SiO2, 0.1-1.2% ZrO2 and 0.01-0.3% fluoride (converted into F) are contained.

Method of joining metal parts by fusion welding

Abstract: A method of joining metal parts by fusion arc welding in a weld of small volume includes the steps of providing the metal parts to be joined having a first side which accessible to a welding operation and a second side opposite the first side. The metal parts have welding surfaces shaped to have a first flank adjacent the first side and a second flank adjacent the second side, a step joining the flanks. Each part has a relief bulge formed in the second side adjacent the second flank, and a centering offset at the second flank to position the metal parts relative to one another for welding. The relief bulge is provided to ensure that the centering offsets melt during welding, and is shaped to have a sufficient size so that a predetermined melt-through point develops for melting of the centering offset during welding. The metal parts are positioned for welding by abutting the second flanks at the centering offset, the parts being positioned so that the first flanks define therebetween a first gap and the second flanks define therebetween a second gap, the second gap being narrower than the first gap. In a first welding step, the metal parts are joined at the second flanks by one of a fully automatic tungsten inert-gas welding process (GTAW) or gas metal-arc welding process (GMAW) to form multi-pass welding beads which extend over the entire width of the second gap, and thereafter, the first flanks are joined with a submerged-arc welding process by forming a plurality of welding beads bearing alternately against one and an opposite flank.

Gas metal arc welding fume generation using pulsed current

Abstract: While the fume generation rate of gas metal arc welding (GMAW) is lower than some other arc welding processes, the further reduction of welding fumes is of interest to companies using GMAW. Several researchers have reported lower fume generation rates for pulsed welding current compared to steady current. However, the range of welding parameters where these reduced fume levels can be expected has not been well documented. This paper describes a study of the effects of pulsed welding current on the amount of welding fume and ozone produced during GMAW using a range of welding parameters. Fume generation rates were measured for steady current and pulsed current GMAW of mild steel using copper-coated ER70S-3 welding wire and 95%Ar-5% CO 2 and 85% Ar-15% CO 2 shielding gases. The amount of fume generated during welding was determined by drawing fume through a fiberglass filter using the standard procedures contained in ANSI/AWS F1.2. Results of these measurements show that pulsed welding current can reduce fume generation rates compared to steady current. There is a range of welding voltage that produces the minimum fume generation rate for each wire feed speed with both pulsed and steady current. The data also show that using pulsed current does not guarantee lower fume generation compared to steady current. Welding parameters must be correctly controlled if pulsed current is to be used to reduce fume levels. Fillet welds were made to demonstrate that the pulsed current welding parameters that reduce fume also produce acceptable welds. No significant difference was found in the chemical composition of fumes from pulsed current compared to steady current. Fumes generated by both types of current are mixtures of iron, manganese and silicon oxides. Measurements of ozone generation rates show that the pulsed current welding parameters that reduce fume also increase ozone generation compared to steady current welding

Formation of molten droplets at a consumable anode in an electric welding arc

Abstract: A theoretical dynamic model has been developed to predict the formation of molten droplets on a moving wire electrode in a gas metal welding arc. Calculations have been made of the droplet shape and size as a function of the welding current by accounting for the electromagnetic pinch effect, surface tension, gravitation and momentum transfer due to motion of the solid wire electrode. Our calculations start with an artificial cylindrical liquid column which, for low currents, develops into a droplet which is close to spherical. However, for currents above about 250 A, the magnetic pinch constricts the column such that a smaller elongated droplet is formed.

MAG arc welding apparatus

Abstract: An MAG arc welding method and apparatus is capable of achieving a welding bead in a regular ripple pattern or in a suitable sectional form The welding power source generates the first welding current I1 and a second welding current I2 larger than the first welding current The wire melting speed is changed by switching between the first and the second welding currents The welding method or apparatus according to the invention generates the first arc length more than 2 mm and the second arc length more than the first arc length and switches between both arc length at a switching frequency F of 05 to 25 Hz The ratio of the second to the first welding currents is made to be in 103 to 120 In addition to a welding method to change the arc length by switching the first and the second welding currents at a constant wire feeding rate, the present welding method makes it possible to carry out the lap welding or butt welding even when there is a large gap The large gap requires a large amount of molten metal which is prepared by increasing the wire melting speed caused by an increase in the wire feeding rate by 5 to 20% The resultant reinforcement has a beautiful appearance

Method of welding a carbon steel and an austenitic stainless steel together and resultant structure

Abstract: Method of welding a carbon steel and a austenitic stainless steel involves using high density energy beam like a laser beam or electron beam Welding using high density energy beam is effective to obtain a high precision welding For the purpose of obtaining both high precision and no cracks, and no deformation, the method of the invention controls the structure of a weld portion to be a mixed structure of an austenitic structure and not greater than 20 wt % of a ferritic structure

Flux cored arc welding : arc signals, processing and metal transfer characterization

Abstract: Metal droplet transfer in flux cored arc welding (FCAW) was studied using electrical arc signals and droplets collected from the welding process. A large number of metal droplets from the FCAW experiments was collected. According to the size distribution of the droplets, several metal transfer modes could be identified amongst which spray transfer predominated. The electrical arc signals, in particular, voltage, were processed using the fast Fourier transform (FFT) technique. Characteristic spectral frequencies corresponding to different metal transfer modes were identified. The size distribution of the collected droplets correlated extremely well with these characteristic frequencies. The electrode melt rate, calculated using the characteristic frequencies identified from the FFT analysis, agreed closely with the measured melt rate. Results from the arc signal analysis and the FFT analysis showed that both arc voltage fluctuations (Δu) and characteristic frequencies of the FFT spectra were adequate to distinguish the different kinds of metal transfer modes in FCAW. Metal transfer mode maps, constructed using the two sets of results, were used to determine the optimal parameters for E71T-1, 1/16-in.-diameter electrode, and Ar-25%CO 2 shielding gas.

The Influence of Oxygen Additions on Argon-Shielded Gas Metal Arc Welding Processes

Abstract: It has been observed experi- mentally that small additions of oxygen to the argon shielding gas affect the gen- eral operation of GMAW processes. By theoretically modeling the arc column, it is shown that the addition of 2 to 5% oxy- gen to argon has an insignificant effect on the arc characteristics. This corresponds to the minor changes in the thermophys- ical transport and thermodynamic prop- erties caused by the oxygen addition. Therefore, it is concluded that the addi- tion of oxygen to the argon shielding gas mainly affects the anode and the cathode regions. From the literature, it was found that the formation of oxides initiates arc- ing at the cathode and decreases the movement of the cathode spots. These oxides can also improve the wetting conditions at the workpiece and the elec- trode. Finally, oxygen is found to affect the surface tension gradient and thereby the convective flow of liquid metal in the weld pool.

Microcomputer control energy automatic compensating argon arc welding power source

Abstract: A kind of microcomputor controlled energy self-compensation type argon arc welding power source including analog transistor main power source is installed with 8098 single chip processor minimal system and purified power source used in the system adopting special power source to monitor the chip The current and voltage signals taken from the main power source is sent through the photoelectric isolation to the single chip prcessor system, the current signal is closed loop contrrolled, and the electric arc welding voltage signal is open-loop controlled The welding current can be uniformly regulated, the slope of the output external characteristics can also be regulated uniformly When automatic or semiautomatic welding the thin plate, the variation of electric arc energy caused by arc length fluctuation or variation of network power source voltage can obtain the corresponding compensation to improve obviously the welding quality

Chemical Composition and Crystal Structure of Oxide Inclusions Promoting Acicular Ferrite Transformation in Low Alloy Submerged Arc Weld Metal.

Abstract: High toughness are requested in the weld metals for offshore steel structures and steel line-pipes used at low ambient temperatures. Micro-alloying of titanium and boron effectively improves the toughness of low-alloyed weld metals with tensile strength ranging between 490 and 590 N/mm2. It is well known that refined intragranular ferrite or acicular ferrite nucleates on titanium containing oxides. However, there have been few reports on the chemical composition at local positions of these effective inclusions and their crystal structures. Two types of submerged arc weld metals were used ; one is a silicon-and-manganese type weld metal with a ferrite with aligned second phase and the other is a titanium type one with the acicular ferrite. The mechanical and metallurgical examination included the microscopic observation, Charpy impact tests of the welds and the characterization of oxides in weld metals with X-ray diffractions and analytical electron microscope. The following facts were clarified from the above investigations. The oxides in the titanium bearing weld metal are crystallized in a form of (Mn, Ti) (Al, Ti)2O4 with angularly rugged surfaces, while the oxides of a Si-Mn type are amorphous with smooth spherical shape. Titanium as low as 0.005 wt% in a weld metal satisfactorily crystallized oxides if titanium is included in oxides with aluminum and manganese.

Occupational asthma due to gas metal arc welding on mild steel.

Abstract: Occupational asthma has been documented in electric arc welders exposed to manual metal arc welding on stainless steel. A subject is described who developed late and dual asthmatic reactions after occupational-type challenge exposure to gas metal arc welding on uncoated mild steel.

Estimation of regional pulmonary deposition and exposure for fumes from SMAW and GMAW mild and stainless steel consumables

Abstract: The particle size distributions and bulk fume densities for mild steel and stainless steel welding fumes generated using two welding processes (shielded metal arc welding [SMAW] and gas metal arc welding [GMAW]) were used in mathematical models to estimate regional pulmonary deposition (the fraction of each fume expected to deposit in each region of the pulmonary system) and regional pulmonary exposure (the fraction of each fume expected to penetrate to each pulmonary region and would be collected by a particle size-selective sampling device) Total lung deposition for GMAW fumes was estimated at 60% greater than that of SMAW fumes Considering both the potential for deposition and the fume specific surface areas, it is likely that for equal exposure concentrations GMAW fumes deliver nearly three times the particle surface area to the lungs as SMAW fumes This leads to the hypothesis that exposure to GMAW fumes constitutes a greater pulmonary hazard than equal exposure to SMAW fumes The implications of t

Analysis of TIG Welding Arc Using Boundary-Fitted Coordinates:

Abstract: The characteristics of argon arc in tungsten inert gas (TIG) welding have been studied by considering the electrode shape which has an effect on the current density distribution near the electrode ...

Analysis and design of variable frequency and phase-shift controlled series resonant converter applied for electric arc welding machines

Abstract: This paper presents the analysis and design of a variable frequency and phase-shift controlled series-resonant power converter applied as a power source for an electric arc welding machine with output ratings of 30 V and 130 A. The main switches of this power converter always hold zero-voltage switching (ZVS) from very light to full load. The conventional filter inductor is removed so as the assumption of a constant current sink is no longer valid, thus complicating the analyses dramatically. The operational principles of the power converter applied in a welding machine design are described in detail from which the voltage and current stresses imposed on the main components can be, therefore, derived and the design procedure can also be outlined. Computer simulations and experimental results obtained from a laboratory prototype are illustrated to confirm the analytical work.

Application of superconducting shields in current-limiting and special-purpose transformers

Abstract: The principles of operation and the design of power transformers based on superconducting shields have been considered. The laboratory prototypes of fault current-limiting and special-purpose (arc welding/furnace) transformers have been tested. The application of both low-T/sub c/ and high-T/sub c/ superconducting shields has been studied. >

Flux-cored wire and solid wire for arc welding

Abstract: A flux-cored wire for arc welding, wherein a specific surface area, which is defined by the equation of {(Sa/Sm)-1} where Sm is an apparent surface area and Sa is a real surface area in a region to be measured on a surface of the wire, is in the range of from 0.005 to -0.035; and molybdenum disulfide is stuck on the surface of the wire in an amount of from 0.004 to 0.24 g/m2, and no plating is applied on the surface of the wire. Moreover, a solid wire for arc welding wherein the specific surface area {(Sa/Sm)-1} is in the range of from 0.0005 to 0.05; and molybdenum disulfide is stuck on the surface of the wire in an amount of from 0.001 to 0.5 g/m2, and no plating is applied on the surface of the wire.

Method of controlling robot for use in arc welding

Abstract: A robot supports a welding torch for use in arc welding of a cylindrical welding object. The welding object is rotated about an axis and is controlled by a robot controller. The robot is operated to track the welding torch along a calculated welding line to continuously position the welding torch along the welding line. A reference circle is formed by rotation of one point on the welding object. A coordinate system is set with a center corresponding to the center of the reference circle. A laser sensor detects a point on the welding line, and the detected point is stored by using a distance r from a center O of the work coordinate system and a z-coordinate value z. As the cylindrical welding object is rotated by an angle θ corresponding to an interval between the position detected by the laser sensor and a calculated second position, the welding torch is moved to a position to coincide with the second position.

A theoretical study of a gas metal arc welding system

Abstract: A theoretical model of a gas metal arc welding system has been developed to make predictions of the anode temperature profile, welding arc length and arc current. The model incorporates a one-dimensional thermal model of the moving consumable anode and a two-dimensional model for the arc plasma. The model makes possible the calculation of the relationship between the welding arc current, wire feed rate and the supply voltages, for various wire diameters and shielding gases. The predicted welding current for a given wire feed rate shows good agreement with our experimental observation for operation in the spray transfer mode, for steel wire of two different diameters, assuming a workpiece sheath voltage of 15 V.