Showing papers on "Shielding gas published in 1993"

Experimental study of laser‐induced plasma in welding conditions with continuous CO2 laser

Abstract: Laser‐induced plasmas obtained during a welding process have been studied Spectroscopic diagnostics and an integrating sphere collecting the reflected CO2 light are the principal diagnostics used in order to determine the spatial variations of the microscopic parameters such as electron density and temperature, and the energy absorption during this process For several experimental processing conditions of shielding gases, the main perturbing effects such as absorption and refraction of the CO2 laser radiation are quantified Several possibilities for reducing these perturbing effects are then discussed

Calculation of weld metal composition change in high-power conduction mode carbon dioxide laser-welded stainless steels

Abstract: The use of high-power density laser beam for welding of many important alloys often leads to appreciable changes in the composition and properties of the weld metal. The main difficulties in the estimation of laser-induced vaporization rates and the resulting composition changes are the determination of the vapor condensation rates and the incorporation of the effect of the welding plasma in suppressing vaporization rates. In this article, a model is presented to predict the weld metal composition change during laser welding. The velocity and temperature fields in the weld pool are simulated through numerical solution of the Navier-Stokes equation and the equation of conservation of energy. The computed temperature fields are coupled with ve-locity distribution functions of the vapor molecules and the equations of conservation of mass, momentum, and the translational kinetic energy in the gas phase for the calculation of the evap-oration and the condensation rates. Results of carefully controlled physical modeling experi-ments are utilized to include the effect of plasma on the metal vaporization rate. The predicted area of cross section and the rates of vaporization are then used to compute the resulting com-position change. The calculated vaporization rates and the weld metal composition change for the welding of high-manganese 201 stainless steels are found to be in fair agreement with the corresponding experimental results.

Process for high quality plasma arc and laser cutting of stainless steel and aluminum

Abstract: Plasma arc or laser cutting uses a mix of reactive (24a) and reducing gas flows (22a) to cut sheets (14) of stainless steel, aluminum and other non-ferrous metals. The reducing gas flow (22a) to the cut varies as a percentage of the total gas flow to maintain a reducing atmosphere down through the cut (12), but to leave a predominantly oxidizing atmosphere at the intersection of the cut (12) and the bottom surface (14B) of the sheet (14) being cut. In plasma arc cutting these flows can also be characterized as eithe a plasma gas flow (22a) that forms the arc, or a shield gas flow (24a) that surrounds the arc. The reactive gas is preferably a flow of air, oxygen, nitrogen, carbon dioxide or a combination of these gases. The reducing gas is preferably hydrogen, hydrogen 35, methane, or a mixture of these gases. For aluminum, the reactive gas is preferably air or nitrogen and the reducing gas is preferably methane or a mixture of methane and air. In laser cutting the reducing gases such as methane can be used by mixing them with reactive assist gases.

Investigation of the effect of welding parameters on weld quality of plasma arc keyhole welding of structural steels

Abstract: In the present investigation, the individual and interactive effects of the main welding parameters on weld quality of plasma arc keyhole welding of conventional structural steel, high strength microalloyed steel and strong formable microalloyed steel have been examined using welding of butt joints with a square groove in various welding positions, and welding of joint roots with a single-V-groove and the root face in the flat position. The most important welding parameters are welding current, welding speed and welding gases, especially plasma gas flow rate. Welding parameter combinations producing the best quality welds are presented. It is shown that it is possible to achieve defect-free high-quality welds with good strength and toughness properties, but the allowable range of variation of welding parameters, especially for the highest weld quality, is narrow. An argonhydrogen mixture for the plasma gas together with argon as shielding and backing gases give the best results with respect to weld quality.

Cored electrode with fume reduction

Abstract: A consumable welding electrode for electric arc welding in a shielding gas and producing reduced amounts of fume during said welding comprising in combination a steel sheath and a filler within the sheath. The filler including metallic aluminum powder and a dual stabilizing agent of sodium oxide and potassium oxide, wherein the dual stabilizing agent and said aluminum have about a 2.4:1 to 3.5:1 weight ratio.

Flux cored arc welding electrode

Abstract: A flux cored arc welding electrode of the type used with external shielding gas wherein the electrode comprises an outer ferrous sheath and a particulate fill material comprising an acidic flux system and alloying agents with the fill material including an arc stabilizer, titanium dioxide, calcium fluoride, an alloying system of 0-4.0 percent by weight of electrode selected from the class consisting of aluminum, silicon, titanium, carbon and manganese. Iron powder controls the percentage of the fill of the electrode and 0.2-1.0 percent by weight of electrode is polytetrafluoroethylene powder.

Welding assembly for feeding powdered filler material into a torch

Abstract: This publication discloses an assembly suited for feeding a powderized filler material in plasma welding. The invention is based on feeding the filler material flow first along a first channel (6), which is next divided into two separate channels (7) that are branched aside from said first channel (6). The forked branches (7) can further be divided into a plurality of branches (8, 9), and according to an advantageous embodiment, the manifold of feed channels exits into a feed nozzle (5, 11, 12, 13) of shielding gas and powderized filler material, said nozzle being provided with a plurality of grooves (11) along which the gas and powderized filler material enter the welding plasma of the torch and the gas flow becomes laminarized. The shielding gas and the filler material can be fed along a single manifold of channels and the tip of the torch can be made extremely small in size.

Shielding Gases for Arc Welding

Abstract: A shielding gas for flux cored arc welding. The specific gas combination is intended to promote significantly lower fume emission levels while providing equivalent or better welding performance.

Process for the electric welding of two weld parts

Abstract: The invention relates to a process for the electric welding of two weld parts by the flow of electric current through a welding point and the use of fluid such as an inert or protective gas to inhibit or prevent or eliminate oxidation at the welding point. The fluid is supplied through a continuous bore in one weld part and is directed toward the welding point, so that the fluid sweeps over the welding point radially from the bore. The fluid may be an inert gas such as argon or nitrogen, optionally mixed with carbon dioxide; alternatively the fluid may be aqueous liquid, the water being vaporized in the region of the welding point.

Arc characteristics in gas‐metal arc welding of aluminum using argon as the shielding gas

Abstract: A mathematical model has been developed describing transport phenomena in gas‐metal arc welding. In the statement of the model a cylindrical electrode was considered and attention was concentrated on representing the electrodynamic, heat‐transfer, and fluid‐flow phenomena in the plasma column. Solutions were generated for the axisymmetric Maxwell’s equations, Navier–Stokes equations, and thermal‐energy balance equation for variable properties. The specific system considered involved the use of an aluminum electrode and argon as the shielding gas. Several current levels were explored and the theoretical predictions of temperatures were found to be in good agreement with spectroscopically measured temperatures. This appears to have been the first time that gas‐metal arc‐welding problems were treated in such a fundamental manner.

A model for heat and mass input control in GMAW

Abstract: This work describes derivation of a control model for electrode melting and heat and mass transfer from the electrode to the work piece in gas metal arc welding (GMAW). Specifically, a model is developed which allows electrode speed and welding speed to be calculated for given values of voltage and torch-to-base metal distance, as a function of the desired heat and mass input to the weldment. Heat input is given on a per unit weld length basis, and mass input is given in terms of transverse cross-sectional area added to the weld bead (termed reinforcement). The relationship to prior work is discussed. The model was demonstrated using a computer-controlled welding machine and a proportional-integral (PI) controller receiving input from a digital filter. The difference between model-calculated welding current and measured current is used as controller feedback. The model is calibrated for use with carbon steel welding wire and base plate with Ar-CO[sub 2] shielding gas. Although the system is intended for application during spray transfer of molten metal from the electrode to the weld pool, satisfactory performance is also achieved during globular and streaming transfer. Data are presented showing steady-state and transient performance, as well as resistance to external disturbances.

Corrosion resistant welding of stainless steel

Abstract: A process for welding stainless steel tubing in the presence of an inert gas comprising a silicon base gas, in particular silane SiH₄. During the welding operation, a suitable quantity of silicon is deposited by chemical vapor deposition at the weld joint to significantly improve the corrosion resistance of the weld.

Study of gas tungsten arc welding in space (1st report)

Abstract: In the present paper, a new type GTA welding system using a hollow tungsten electorode is proposed to ignite and sustain a welding arc in a vacuum like the open space. In the developed system, Ar gas for discharge is supplied to arc space through the hollow tungsten electrode.The results of the present work are summarized as follows, (1) Even in a low pressure condition, a small quantity of Ar gas flow can ignite and sustain an arc discharge and the arc can melt the base metal.(2) In a low pressure condition, a stationary arc follows a transient arc. The period of the transient arc discharge increases with the decrease of Ar gas flow rate.(3) With the decrease of Ar gas flow rate, the arc voltage increases and the penetration of base metal (stainless steel) increases in size.

In-process monitoring in laser welding of automotive parts

Abstract: Spectral study was carried out to characterize laser induced plasma plume in terms of temperature and electron density in CO2 laser welding of mild steel sheet (0.8 mm thickness). The size and local properties of the plasma plume were determined by means of the Abel inversion technique and CCD camera observation. It was found that the height of the hot plasma core was very small, less than 0.5 mm. The maximum electron density in the plasma plume was approximately 1017/cm3 where the absorption loss of CO2 laser beam via inverse Bremsstrahlung was negligible in the plasma plume. In-process monitoring system using multi photo sensors with different aiming angles was developed to monitor CO2 laser welding of automotive parts, and effects of welding parameters including laser power, welding speed, flow rate of shielding gas and focal position were determined on the light intensity emitted from the welding zone. It was demonstrated that weld defects such as underfill and pits in lap and butt weld joints for automotive parts can be successfully detected by the on-line monitoring system.Spectral study was carried out to characterize laser induced plasma plume in terms of temperature and electron density in CO2 laser welding of mild steel sheet (0.8 mm thickness). The size and local properties of the plasma plume were determined by means of the Abel inversion technique and CCD camera observation. It was found that the height of the hot plasma core was very small, less than 0.5 mm. The maximum electron density in the plasma plume was approximately 1017/cm3 where the absorption loss of CO2 laser beam via inverse Bremsstrahlung was negligible in the plasma plume. In-process monitoring system using multi photo sensors with different aiming angles was developed to monitor CO2 laser welding of automotive parts, and effects of welding parameters including laser power, welding speed, flow rate of shielding gas and focal position were determined on the light intensity emitted from the welding zone. It was demonstrated that weld defects such as underfill and pits in lap and butt weld joints for aut...

Welding complicated, difficult-to-weld metal components

Abstract: The present invention is a method for welding difficult-to-weld metal components as illustrated in the welding of a receiver for a weapon. The method reduces net distortion by a number of techniques, including: (1) cooling the weld with Carbon Dioxide (CO 2 ) preheated with the welding torch tip; (2) use of not more than approximately 4% oxygen in the shield gas to enable hotter, faster welding; (3) the use of a reduced voltage and wire feed rate at the end of a weld to avoid cracking; (4) the intentional use of distortion to reduce net distortion; and (5) sequencing of welds to reduce distortion. Distortion can be introduced in the stamped parts as they are made or when placed in a fixture for welding that, when welded, have less distortion than before. Distortion can also be countered by welding parts in a sequence where a subsequent weld reduces the distortion of a previous weld. The process is illustrated as applied to a receiver for a weapon made by welding non-compatible and low carbon steels in a low tolerance configuration.

Method and apparatus for laser welding with an assist gas including dried air and the assist gas composition

Abstract: A laser welding method which provides improved welding quality, allowing excellent products to be produced. The mixture of inactive gas or nitrogen gas and 5% to 35% of oxygen gas in terms of volume ratio and that of inactive gas or nitrogen gas and not less than 25% of dried air in terms of volume ratio are employed as an assist gas in the lap and butt weldings and filler wire-inserted welding of metal materials filmed with low melting point substance.

Dual fluid atomizer exit orifice shield gas supply housing

Abstract: An atomizer used in boilers, furnaces, downstream contaminant removal processes and the like, to atomize the oil/liquid/slurry product being sprayed into such enclosures. This particular atomizer is configured with individual openings around each exit orifice in the atomizer such that a shield gas (normally air) in communication with these openings, is ejected from the atomizer fully surrounding the spray emitted from each exit orifice.

Laser beam welding method and jig used for the method

Abstract: PURPOSE:To make fine the rear of the face of weld of sheet metals and to obtain the face of weld of high quality having an improved shape when laser beam welding is performed. CONSTITUTION:When a butt part WT of the sheet metals W is irradiated with a laser beam LB from a laser beam machining head 5 which is moved along a butt line WL of the butt part WT to perform laser beam welding on the sheet metals W, back shielding gas G is blown against the rear of the face of weld of the sheet metals W. In addition, the jig 3 on which the sheet metals W are mounted and fixed is formed with a notched groove 29 in the direction of the butt line of the sheet metals W, provided with an injection opening 33 to inject the back shielding gas G on the upper surface along the butt line WL of the sheet metals W and a heat sink 31 provided with a path 37 for the back shielding gas to communicate with this injection opening 33 is engaged attachably and detachably with the notched groove 29.

Casting of high oxygen-affinity metals and their alloys

Abstract: A process for casting high oxygen affinity metals or metal alloys such as titanium through use of an induction furnace while preventing the pick up of contaminating gas by the metals or metal alloys during melting. An inert shielding gas such as nitrogen or argon or carbon dioxide is introduced as a liquid in a closed environment above the metal or metal alloys being melted such that there is preferably no more than approximately 1% contaminating gas in the gaseous environment proximate the surface of the molten metal or metal alloy. Simultaneously, the mold placed under the induction furnace is purged with a similar or different inert gas.

Gas shielded arc welding method for galvanized steel sheet, welding machine therefor and galvanized steel sheet product welding by the welding method and the machine

Abstract: PURPOSE:To perform welding of galvanized steel sheet while maintaining satisfactory welding workability by performing pulse MAG welding and short circuiting transfer welding alternately. CONSTITUTION:In consumable electrode welding, welding is performed with gas containing argon gas and gaseous carbon dioxide as shielding gas. Pulse MAG welding A superimposed with a pulse current and short circuting transfer welding B are then performed alternately. Oxygen gas of 2-7% is mixed into the shielding gas to perform welding. The gas shielded arc welding machine is provided with a short-circuit current setting device and a pulse current setting device, the output of each setting device is inputted to a changeover switch and output signals of the short-circuit current setting device and the pulse current setting device are outputted alternately according to an output signal from a frequency setting device. Consequently, the welding quality is improved, the decrease of bead external appearance is surpressed and lowering of working efficiency of spatter removing work, readjustment of a weld zone, etc., can be solved.

Heat flow and arc efficiency at high pressures in argon and helium tungsten arcs

Abstract: For control of welding underwater robotic systems, the arc characteristics and the heat quotation in cathode, arc column and anode (weld) were measured in GTAW with argon and helium shielding gas using the calorimetric method. The measurements were performed mainly in a pressure chamber. The pressure, the current and the arc length were varied from 0.1-6.0 MPa, 50-300 A and 2-11 mm, respectively. It was observed that the welding voltage is strongly dependent on system pressure for both shielding gases and an explicit minimum voltage/current was obtained for the argon arc characteristics at approximately 100 A. Furthermore, the field strength and the heat emission from the arc column increased exponentially with the pressure. A simple relation was developed to predict heat emission from the arc column and, consequently, for the arc efficiency. In addition, a calculation model for engineering use was derived based on the Ellenbaas-Heller equation to calculate the-heat flux from the arc to the weld (for both gases).

Fourth-generation inverters add artificial intelligence to the control of gma welding

Abstract: A new level of control has been achieved over the welding arc by using some of the latest techniques in artificial machine-intelligence computer control and by direct control of the short-circuit waveform. By controlling the short-circuit waveform in real time, these artificially intelligent power supplies control the instantaneous welding conditions and improve the GMAW process in terms of welding performance. These artificial-intelligent power supplies can yield many benefits. Among them are lower spatter levels, both in argon-based shielding gases and 100% CO[sub 2] shielding gases. Another benefit is faster arc speeds. In many cases the arc speeds can be 25% faster. Better productivity, through the better arc-striking capability and reduction of downtime associated with spatter on peripheral equipment, is another important factor. These power supplies are synergic and therefore provide for easier operator control. In addition, they have higher electrical efficiency; thus they yield lower operating cost.

Narrow groove welding of titanium using the hot-wire gas tungsten arc process

Abstract: From this study of automatic gas tungsten arc welding of commercially pure titanium, the following may be concluded: (1) automatic cold-wire GTAW and automatic hot-wire GTAW may be used to weld titanium in the open without contamination from the atmosphere when proper shielding is used; (2) automatic hot-wire GTAW exhibits substantial reductions in transverse weld shrinkage, as compared to manual GTAW; (3) increased deposition rates can be achieved with hot-wire additions to automatic gas tungsten arc welding; (4) automatic cold-wire GTAW and automatic hot-wire GTAW may be used with narrow groove joint designs; (5) direct viewing of the arc may be used to aid in torch placement and wire entry position.

Shielding-gas arc welding method and appertaining shielding gas

Abstract: The invention relates to shielding-gas arc welding methods making use of the melting (burning-off) electrode and also the non-melting electrode, which involve, during welding operations, continuously supplying the weld spot (welding point) adjacent to the electrode with a stream of shielding gas, the shielding gas being composed for a major part of argon and/or helium. Such welding methods are known in many versions, and quite generally they enable the most diverse materials (ferrous and non-ferrous materials) to be welded together satisfactorily. In a number of practical cases, e.g. with respect to aluminium welding, however, it is possible for welding to proceed in a non-optimal manner, not uncommonly particularly with respect to the important arc stability. This disadvantageous situation is improved markedly, according to the present invention, by the shielding gas being additionally mixed, in a proportion range of no more than from 20 to 5000 vpm, preferably from 50 to 3000 vpm (from 0.005 to 0.30 % by volume) with additions of heavy noble gases (Kr, Xe) and/or stable, simple biatomic or triatomic non-noble gases (H2,O2, CO2, N2O, NO2 and the like) and/or gaseous, stable organic compounds, preferably C1 to C4 hydrocarbons (CH4, C2H4), having ionisation energies between 8 and 17 eV, preferably 8 and 14.3 eV.

Shielding gas for use in the arc welding of aluminium

Abstract: In the TIG and MIG welding of aluminium, high-purity argon or high-purity argon/helium mixtures are used as the inert gas. In order to improve the welding process and the result obtained, the invention proposes that 80 to 250 vpdm, preferably 120 to 180 vpdm, of N2/N2O are added to the inert gas. Any ratio of N2 to N2O may be used.

Welding of aluminum powder alloy products

Abstract: A TIG weld produced from a rapidly solidified dispersion strengthened aluminum base alloy exhibits attributes of the alloy's microstructure extant prior to formation of the weld. TIG welding power is adjusted to minimize energy input into the weld. An arc gas contacts the weld to maximize rapid quenching thereof, while a second gas contacts the undersurface of the weld so that the undersurface of the weld is quenched. Cooling of the weld is further enhanced by a trailing gas selected from the group consisting of argon, nitrogen, helium, carbon dioxide and mixtures thereof.

Nozzle for side shielding of laser welding

Abstract: PURPOSE:To enable efficient side shielding at a low flow rate by constituting the nozzle adequate for use at the time of supplying a shielding gas to a part irradiated with a laser by a side shielding system in laser welding in such a manner that the shielding gas is forcibly blown to the part irradiated with the laser CONSTITUTION:This nozzle has a tubular gas suction part 5 which is formed at the front end of the nozzle 3A and successfully introduces the shielding to a weld zone, a hood part 6 which is communicated and connected with and to this gas suction part and covers the weld zone, and a discharge part 7 which is expanded and formed outward in order to discharge the shielding gas past this hood part 6 to the outside

Exothermically assisted shielded metal arc welding

Abstract: Heat input, which is most often directly related to electrical energy input, controls weld bead morphology and the evolution of microstructure. Exothermic reactions have been found to increase the heat input available during shielded metal arc (SMA) welding. The work presented in this paper was performed to determine how much heat can be attained from exothermic reactions and determine the influence of this additional heat on weld deposition. Consumable SMA welding electrodes were produced with reagents added to the flux coating. The flux additions to promote exothermic reactions consisted of magnesium plus hermatite (Fe{sub 2}O{sub 3}), aluminum plus hermatite, and a 50-50 wt% aluminum-magnesium alloy plus hermatite. With calorimetry, increasing concentrations of exothermic promoting additions were found to produce an increase in the effective heat input. Electrodes with sufficient exothermic additions were found to product 25{emdash}30% of the heat necessary for welding. Finally, the efficiency of the shielded metal arc welding process was determined with and without the reagent. Analysis of energy generation and utilization was performed to evaluate the use of pyrochemical flux reactions to produce exothermically assisted consumables. A model ha been developed to assist in the formulation of exothermically assisted SMA electrodes.

Spatter reduction technique

Abstract: A method of metal-inert gas arc welding which reduces spatter in the welding process, wherein a liquid (8), preferably a hydrocarbon, is dispersed in the inert gas during the welding process. At a weld site (2) the use of the liquid (8) dispersed in the gas prevents any spatter formed from adhering to any surfaces adjacent the welding hand piece (3). The liquid may be dispersed in the gas by passing the gas through the liquid in a container (7) located between the gas supply (12, 13) and the welding hand piece (3), or may be injected into the gas as a vapour or fine mist.