Showing papers on "Arc welding published in 1991"

Apparatus and method of controlling a welding cycle

Abstract: An improvement in a short circuiting arc welding apparatus of the type including a power supply for causing a welding current of different levels to pass through a welding wire extending at variable extension distances from a holder and between the wire and a workpiece at a molten metal pool on the workpiece. This improvement includes control means for maintaining a generally constant wattage in the wire during the plasma boost portion of the arcing condition as the extension distance from the holder changes. Further, the improvement involves controlling the plasma or arcing condition after a plasma boost by a current curve gradually decreasing from the plasma boost portion toward the background current level for the system.

Fundamentals of welding metallurgy

Abstract: Metallurgical presentation of the general welding processes and characteristics of the welding operation Thermal and thermochemical study of welding Introduction to the metallographical examination of welds Formation of the fusion zone Solidification of the weld metal Solid phase transformations during welding (heating) Solid phase transformations during welding (cooling) Hardening and cold cracking in steel welding Heat treatments for steel welds Metallurgical aspects of destructive and non-destructive weld tests.

D-C arc welding apparatus

Abstract: A d-c arc welding apparatus including an engine-driven welder converting the a-c power generated by an engine-driven alternator into d-c power for use as the drive power of the welder, a battery-driven welder using a battery as the drive power of the welder, and a changeover switch for selecting between a high-power mode in which the above-mentioned welding d-c outputs are connected in parallel and fed to the welding apparatus, and a low-power mode in which either of the above-mentioned welding d-c outputs is supplied independently to the welding apparatus.

The chemistry and structure of wear-resistant, iron-base hardfacing alloys

Abstract: The chemistry and microstructure of iron-base alloys resistant to galling wear were determined by using optical microscopy and scanning electron microscopy (SEM). Castings and weld overlays, deposited by the gas tungsten arc and plasma arc welding (GTAW and PAW, respectively) processes, were evaluated. The microstructure typically consisted of a primary austenitic matrix, eutectic carbides (M7C3 type), and noneutectic carbides. Processing techniques that resulted in high cooling rates yielded microstructures with finer features, less complete partitioning of alloying elements to the carbides, and improved resistance to galling wear. Carbon and manganese appeared to improve resistance to galling wear. Nickel was detrimental to galling wear resistance.

Structure of metal container having trunk pipe and branch pipe, and manufacturing method and apparatus therefor

Abstract: A welded metal container for a sheath 1 or 1A of gas insulated switch gear comprises a trunk pipe 2, 21 and a branch pipes 3, 31, 32 welded to the trunk pipe 2,21 by arc welding A or laser beam welding LB and flanges welded to the each end portion of the trunk pipe 2, 21 and branch pipes 3, 31, 32 by the laser beam welding After the arc welding A, the ends of trunk pipe 1, 21 and branch pipes 3, 31, 32 are machined precisely and flanges 4a, 4b, 4c, 4d, 4f and 4g are welded to the end portions of the trunk pipe 2, 21 and branch pipes 3, 31, 32

Convertible arc welding system

Abstract: In a convertible TIG, MIG or plasma arc welding system, a cylindrical docking body mountable in a socket at a welding station, has utilities passages therethrough for receiving an elongated metal electrode, shielding and plasma gases, welding potential and cooling water. The electrode passage is threaded at one end to interchangeably mount any of a plurality of electrode feed assemblies for consumable wire or tungsten electrodes. An output fixture is mounted at the other end of the body to receive the electrode and the plasma or shielding gas and pass them from the body. A nozzle assembly is removably mountable on the other end of the docking body in surrounding relationship with the output fixture and the associated tip assembly and communicates with the shielding gas passage for passing shielding gas to the working end of the nozzle. The docking body has internal channels among the passages so as to circulate cooling water through both the output fixture and the nozzle assembly. The working end of the nozzle assembly interchangeably mounts any of a plurality of gas directing assemblies for directing gases relative to the arc. The system can be converted among TIG, MIG and plasma arc welding by simply changing the electrode feed assembly, the tip assembly and the gas directing assembly. Alternatively, the entire nozzle assembly can be replaced with one designed for TIG or MIG welding.

Welding Zinc‐Coated Steel with a Laser and the Properties of the Weldment

Abstract: This paper discusses the lap welding of zinc‐coated mild steel sheet using a laser. This process is of great interest to the manufacturers of cars, washing machines and other components made from sheet steel and subject to corrosion. Conventional and high‐energy density welding of this material results in explosive ejection of the zinc vapor and an unsatisfactory weld. Several techniques are presented for the removal of the zinc from the interface or the control of the zinc vapors. Of the processes discussed in the paper the use of a gap between the sheets to vent the zinc vapor is shown to produce satisfactory welds. The resulting welds made both by this gap technique and by welding uncoated material were tested for fatigue, impact resistance, mechanical strength, hardness and corrosion resistance to salt solutions. The welds were made using a variety of lasers and the comparison in performance of these lasers is presented.

Effective heat input in pulsed current gas metal arc welding with solid wire electrodes

Abstract: In this work, the heat input of the welding arc, calculated from the measured values for voltage and current, is compared to the heat gained by the weldment for pulsed and nonpulsed current welding. The effects of shielding gas composition, arc length, weld geometry and weld position on heat transfer are examined. Methods for calculating the heat received by the weld during pulsed current welding are discussed

Theory of Weldability of Metals and Alloys

Abstract: 1. Welding. 2. Thermal Cycle in Welding. 3. Strain Stress Welding Cycle. 4. Heat Affected Zone. Precipitation processes in the heat affected zone. Grain growth in the underbead zone. Behaviour of inclusions in heat affected zones. Properties of the heat affected zone. 5. The Weld Metal. The melting stage. Gas absorption in welds. Stage of weld metal solidification. Segregation and liquation. Stage of microstructural transformation. Properties of weld metals. 6. Weld Joint Cracking. Hot cracking. Cold cracking. Lamellar tearing. Stress relieve cracks. 7. Heat Treatment of Welded Joints. Review of requirements and prescriptions of classification societies concerning annealing. Temperature of stress relief heat treatment. Rate of heating and cooling. Mechanical modes of stress relaxation. Recrystallization heat treatment and annealing with partial recrystallization. 8. Selection of Steels for Welded Structures. 9. Weldable Structural Steels. 10. Weldability of Chromium, CrMo and CrMoV Steels. Metallurgy of base material. Heat treatment. Welding processes. Selection of filler material. Weldability. Post welding heat treatment. Microstructure and properties of weld metal. Operational properties of weld joints. Thermal embrittlement. 11. Steels for Cryogenic Temperatures. Metallurgical background. Austenite decomposition diagrammes for nickel steels. Heat treatment. Thermal embrittlement. Weldability. Selection of filler material. 12. Welding of High-Alloy Steels. Austenitic manganese steels. 13. Welding of Stainless Steels. Fundamental characteristics of weldability and the welding process. Stainless steels: Martensitic Ferritic Austenitic Duplex ferrite-austenite Martensitic austenitic Precipitation-hardened Practice in welding. 14. Cast Iron. Weldability of cast iron. 15. Nickel and its Alloys. 16. Copper Alloys. Weldability. Post welding heat treatment. 17. Weldability of Aluminium Alloys. Crackability tests. Choice of filler materials. Preparation for joining. Weldability. Welding. 18. Magnesium Alloys. Welding. 19. Cobalt. 20. Titanium, Tantalum, Zirconium, Hafnium and Niobium. 21. Welding of Beryllium, Uranium, Molybdenum, Vanadium, Gold, Silver and Lead. Summary. References. Index.

Cored electrode wires

Abstract: A cored electrode wire for pulsed electric arc welding, wherein said core includes from 2.5 to 12% calcium fluoride, from 2 to 8% calcium carbonate, from 0.2 to 2% silicon dioxide and from 0.5 to 1.5% of a fused mixed oxide. Also disclosed is a cored electrode wire for pulsed electric arc welding, wherein said core contains from 4 to 15% elemental manganese and from 2 to 8% elemental silicon, the remainder of the core comprising fused mixed oxide, desired alloying components and iron powder. In each of the above cases, the wire is suitable for use with the following welding pulse parameters: pulse energy: 8 to 250 J and preferably 10 to 120 J; pulse frequency: 10 to 500 Hz and preferably 15 to 350 Hz; background current: 8 to 250 A and preferably 10 to 100 A; wire feed speed: 1 to 20 m/min and preferably 4 to 17 m/min.

Gas metal arc welding and shielding gas therefor

Abstract: A welding method and shielding gas therefor which enables the use of gas metal arc welding to produce smooth welds with little or no surface oxidation and without encountering arc instability during the metal deposition.

Arc welding method and apparatus

Abstract: A method of consumable electrode arc welding is shown wherein the leading consumable electrode wire is mounted in parallel with a trailing filler wire, the latter inserted into a molten metal bath. Welding current is divided between the consumable electrode wire and the filler wire. These modifications improve the wettable boundary of the molten metal bath, prevent defects in the weld, and provide a high speed, highly efficient and high quality method of welding carbon steels, alloy steels, as well as aluminum and its alloys in a fully automatic as well as a semiautomatic operation. In an apparatus utilizing the above method, a single torch contains the consumable electrode and filler wire. One or more insulating contact tubes containing filler wire are mounted in a gas shield in parallel with a conductive contact tube containing consumable electrode wire. The unit is small in size and light-weight, and thus convenient for a welder to carry or hold during operation. Appropriate selection of one of the filler wires provided allows multidirectional operation without reorienting the torch. The unit produces a high-quality weld at rapid welding rates and is suitable for automatic and semiautomatic operation.

Shielding gas mixture for welding superalloys

Abstract: This invention discloses a novel shielding gas mixture for use in gas shielded arc welding processes. The shielding gas of this invention may be used in a wide variety of processes when welding various superalloy compositions. In the broad range, the composition contains, in percent by volume, 5 to 12 helium, 0.1 to 0.9 carbon dioxide and the balance argon. The typical composition contains about 10 helium, about 0.25 to 0.55 carbon dioxide and the balance argon plus impurities.

Welding material for low coefficient of thermal expansion alloys

Abstract: The invention provides a welding material for welding iron containing low CTE alloys. The filler metal contains 25-55% nickel, 0-30% cobalt, 0.05-0.5% carbon, 0.25-5% niobium and balance iron with incidental impurities. The welding material also is operable with fluxes for submerged arc welding. In addition, the welding material may be configured to function as a flux coated or flux-cored electrode.

Submerged arc flux and method of making same

Abstract: A granular flux suitable for submerged arc electric welding comprising particles of composite fluxing ingredients of the agglomerated or fused type combined with a halogenated polymer as a reducing agent for diffusible hydrogen in the resulting weld metal and a method of making this granular flux wherein the polymer is mixed with the flux particles and then heated to a temperature above the melting temperature of the polymer and below the vaporization temperature of the polymer.

Analyses of electrode heat transfer in gas metal arc welding

Abstract: The present study examines the thermal processes occurring in moving electrodes for GMAW with the objectives of 1) determining which phenomena are important in controlling the melting rate and 2) explaining the formation of a tapering tip observed for some combinations of electrode materials and shielding gases

Flexible portable container for carrying and maintaining arc welding electrodes at use temperature and method for maintaining arc welding electrodes at use temperature

Abstract: A combination of a layered leather pouch and a flat flexible unified structure of a heater utilizing an exothermic composition for the purpose of creating and maintaining an arc welding rod inside the pouch at a temperature range between about 28 degrees C and about 139 degrees C, the pouch having a walled off compartment made of specifically perforated suede, the compartment being adapted to receive and hold one or more heaters having sufficient heat generating capacity to maintain the rod in the temperature range for an extended period of at least 3 hours and to be portably and safely worn adjacent a welder on his belt.

Shielding gas for arc welding of aluminum

Abstract: A shielding gas for the arc welding of aluminum consists of argon or mixtures of argon and helium. The shielding gas also includes an admixture of 80 ppm to 250 ppm of nitrogen.

A Study on Prediction of Welding Current in Gas Metal arc Welding Part 2: Experimental Modelling of Relationship Between Welding Current and Tip-to-Workpiece Distance and its Application to Weld Seam Tracking System

Abstract: The weld joint tracking sensor is indispensable to improve the flexibility of the arc welding robot application. Recently, some sensing methods that utilize the electric arc signal, or more correct...

Development of residual stress and surface cracks in laser treated low carbon steel

Abstract: Scripta ME?~LLJR3iCA Vol. 25, pp. 779-784, 199! Pergamon Press plc et M.~,e~AL[A Printed in the U.S.A. All rights reserved DEVELOPMENT OF RESIDUAL STRESS AND SURFACE CRACKS IN LASER TREATED LOW CARBON STEEL B.A. Van Bmssel, H.J. Hegge and J.Th.M. De Hosson Department of Applied Physics, Materials Science Centre, University of Groningen, Nijenborgh 18, 9747 AG Groningen, The Netherlands R. Delhez, Th.H. de Keijser, N.M. Van der Pers Laboratory of Metallurgy, Rotterdamseweg 137, 2628 AL Delft, The Netherlands (Received January 17, 1991) Introduction Laser surface melting is a powerful technique to produce wear resistant layers. It combines the advantages of local hardening, alloying and high quench rates. The latter may result in new metastable phases with novel tribological properties. Despite these advantages laser melting may produce residual stresses in the surface layer which may affect the wear performance and the sensitivity to fatigue and fracture. As is known from conventional welding technologies [ 11, local heating may cause detrimental stresses. During a laser treatment a similar situation is created and consequently residual stresses are being detected [2,3,41. In former studies however average stress intensities are measured over a laser track. Here results of measurements will be reported which present a better insight in stress variations within and in the neighbourhood of a laser pass. Another aspect of a laser treatment is the occurrence of some cracks in the surface. In principle cracks are preferential sites for fatigue or corrosion fracture [5,6,7]. Here the main interest concentrates on the residual stresses produces by a continuous COz laser treatment and effects on fracture in a low carbon steel CK 22. With respect to cooling rate and heat input a continuous laser can be placed in between a short pulse laser and electric arc welding. Applying a short pulse laser it is possible to produce a shock wave. By rapid heating plastic deformation occurs and even evaporation of a thin surface layer [8,91. Although the interaction time of a continuous laser beam is larger, deformation effects may be expected as is confirmed by the residual stresses found. In welding heat is maintained during a time lapse which is long enough to anneal a large amount of the defects. In contrast to this, the thermal cycle of a laser treatment is much shorter, which may prevent annealing effects. Experiment

Formation of stainless steel layer on mild steel by welding arc cladding

Abstract: The discrete microstructural characterization and the formation of stainless steel layer on mild steel where produced in cladding deposits, and fusion boundary region were investigated using tungsten inert gas (TIG) arc, high current pulsed arc and constricted plasma arc. The experimental procedure involved making bead-on-plate method for controlled travel speed, employing filler metal by using tungsten inert gas arc, pulsed current gas tungsten arc and transferred plasma arc, with subsequent sectioning and examination of the reaction interface. For TIG arc cladding, using filler metal of small diameter the deposit does not become stainless steel, but on using 3.2 mm diameter filler metal it becomes stainless steel with less than 50% dilution. For pulsed arc cladding, the complete stainless steel is not obtained on account of the existence of an incomplete mixture, particularly at the fusion boundary region. However, on using a large diameter filler metal at a pulse frequency of 500 Hz, the complete stainless steel microstructure has been accomplished. The plasma arc cladding can be achieved in such a way that the conversion into stainless steel on the mild steel surface — which is the microstructures of cellular austenite in cladding deposit and cellular dendritic austenite containing δ or σ-phase in fusion boundary region — is possible irrespective of the melt penetration and the dilution. The following conditions were found to be beneficial for the formation of stainless steel microstructure layer on the mild steel: using large diameter filler metal, below 50% dilution, and further rendering arc localized and constricted.

Method of welding a first to a second metal plate

Abstract: A method of welding a first metal plate to a second metal plate including the steps of affixing a back-up bar by use of spaced welding tacks to the flat surface of a first metal plate, forming an abutting edge on the second metal plate a series of alternating lands and slots, the slots extending through the entire thickness of the second metal plate and the length of the slots being substantially greater than the length of the lands, positioning the formed edge of the second metal plate so that the lands thereof engage the flat surface of the first metal plate and a substantially continuous slot is formed between the plates and in which the second metal plate is in engagement with the back-up bar to form a joint, arc welding with a consumable electrode in the substantially continuous slot to form a weld, the weld penetrating portions of the flat surface of the first metal plate, the entire abutting edge of the second metal plate and a portion of the back-up bar and melting the lands and the welding tacks and in which the welding step is preferably performed in one pass.

Laser Welding of Titanium Alloy

Abstract: (1991). Laser Welding of Titanium Alloy. Welding International: Vol. 5, No. 5, pp. 346-351.

A Study on an Arc Sensor for Gas Metal Arc Welding of Horizontal Fillets An S-shaped fillet weld was successfully tracked using the quadratic curve-fitting method for sensing

Abstract: The weld joint tracking sensor is indispensable for improving the flexibil­ ity of arc welding robot applications. Re­ cently, some sensing methods that utilize the electric arc signal, or more correctly the welding current in GMA welding, have been developed and are prevalently in use. The welding current is directly af­ fected by the contact tip-to-workpiece distance for the given welding voltage and wire feed speed. Armed with a means of measuring the welding current, the tip-to- workpiece distance and then the weld joint geometry can be obtained by weav­ ing the arc back and forth across the line of travel. Knowledge of the weld joint geometry relative to the welding gun per­ mits the welding gun to trace the joint. In this study, the welding current signal was fitted to a curve, which is inversely proportional to the trace of contact tip- to-workpiece distance by using the qua­ dratic curve-fitting method in order to ex­ tract useful information on the welding gun position from the welding current sig­ nal. Furthermore, the availability of the curve-fitted welding current signal was in­ vestigated and a joint tracking system for horizontal fillet joints was developed by using this curve-fitting method.

Evidence from inclusion chemistry of element transfer during submerged arc welding

Abstract: The complex changes in composition during the submerged arc welding of C-Mn steels have been related to flux composition and weld metal inclusions, which form the final reaction products. High-temperature reactions in the arc plasma (particularly those involving oxygen, fluorine, calcium and magnesium) are followed at lower temperatures by reactions in the slag and the weld pool

Automatic welding apparatus

Abstract: An automatic welding apparatus for non-consumable-electrode-type arc welding comprises a mechanism which is adapted to feed a second wire in the molten pool and to oscillate this second wire in synchronism with the oscillation of the welding torch and the conventional wire and at a position where both wires are opposed to each other in an axis perpendicular to weld line. An automatic welding apparatus for consumable-electrode-type arc welding comprises a mechanism which is adapted to feed a second wire in the molten pool and to oscillate this second wire in synchronism with the oscillation of the welding torch and at a position where both wires are opposed to each other in an axis perpendicular to weld line.

Consumable electrode type arc welding machine

Abstract: PURPOSE: To form and output an optimal output signal by predicting switching of the next short circuit arc by using an inference obtained by a fuzzy theory, based on a feedback signal of an output arc state. CONSTITUTION: A fuzzy inference part 1 inputs feedback signals of an output arc state outputted from a current detecting part 5, a voltage detecting part 4, and a short circuit arc period time counting part 3, and infers the next short circuit start and the arc generation time by a fuzzy theory, and a waveform control part 2 constitutes an output waveform, based on an output from this fuzzy inference part 1, and an optimal arc state is obtained. COPYRIGHT: (C)1992,JPO&Japio