Showing papers on "Arc welding published in 1987"

Method and device for controlling a short circuiting type welding system

Abstract: A method and device for controlling a power supply for arc welding in a manner to reduce spatter when the power supply is employed for depositing metal from a welding wire or electrode onto a workpiece by the short circuiting transfer mode wherein a welding current causes the welding wire to alternate between a short circuit condition and an arc condition with metal transfer occurring during a short circuit condition. This method and device includes the concept of shifting the welding current to a background current value in response to a short circuit condition, holding the welding current generally at the background current level for a preselected time, then allowing the welding current to reach the normal unimpeded current level, and causing the holding step to be terminated before the selected time in response to a detected arc condition. This concept provides a predetermined low current condition immediately upon establishing a short circuit between the welding wire or electrode and the workpiece, which low current condition is retained long enough to convert what otherwise would be a spatter-laden momentary short circuit to a short circuit where metal is transferred to the workpiece. Further, the method and device detects the slope of the welding current or voltage and shifts the welding current to the low background current level when the welding current reaches its maximum value just before breakage of the metal from the wire thus reducing the spatter energy when the molten metal breaks from the wire.

Pulsed arc welding

Abstract: A pulsed arc welding system includes a current pulse generating circuit and a background current generating circuit. The lowest arc voltage across the arc load is detected during a predetermined time period immediately preceeding the onset of each current pulse. The pulse repetition rate is controlled on the basis of this detected voltage so that the detected arc voltage becomes constant.

Stabilized welding power source including a series-resonant current-regulated converter using a transformer having an air-gapped core

Abstract: A pulse arc welding power supply incorporating one or more series resonant converters (SRC) for converting D.C. power to A.C. power which is then rectified to supply welding current. Each series resonant converter includes a series resonant tank circuit consisting of a capacitor, an inductor and the primary winding of a transformer whose secondary winding supplies current to the welding arc. The undesirable secondary output capacitor of the prior art is eliminated, as all the capacitance in the series resonant circuit is located on the primary side of the transformer. Current sensors sense the ringing current in the resonant circuit and also the load current and produce respective feedback signals which are used to control the switching frequency of an SCR bridge in the tank circuit, thereby maintaining the welding current at a desired value. Inner and outer current regulating loops, including a ramp generator, compensate for non-linearity in the continuous conduction mode of the SRC by limiting the switching frequency of the SCRs. a fault-predicting circuit also further limits the switching frequency in the continuous current mode for additional protection.

Mathematical modeling of melting rates for submerged arc welding

Abstract: The effects of welding current, arc voltage, wire diameter, electrode extension (EE), electrode polarity, power source type and flux classification on melting rates (MR) have been evaluated for the submerged arc welding process. The results show that for a given heat input, greater melting rates are obtained when higher current, longer electrode extension, smaller diameter electrodes and electrode negative polarity are used. Arc voltage, power source type and flux classification do not have any significant influence on melting rates. Mathematical models to correlate process variables and melting rates have been computed from the data.

Pulsed arc welding method, apparatus and shielding gas composition

Abstract: Metal deposition rate is increased with reduced energy input in pulsed arc welding with a consumable electrode and a shielding gas mixture of argon, helium and carbon dioxide, the helium content being in the range from about 16% to about 25% and the carbon dioxide content being from about 1% to 4%. The component gases are stored in separate containers until the welding operation during which precisely metered flows of each are entrained by a metering valve and directed to the weld region. Consistently finished welds are produced, on stainless steel, low alloy steels and nickel based alloys as well as other weldable ferrous metals, including during out of position welding operations.

A study of the heat transfer during arc welding with applications to pure metals or alloys and low or high boiling temperature materials

Abstract: An analysis of the heat transfer during arc welding has been carried out. The study is applicable to pure metals or alloys and to low or high boiling temperature materials and includes the effects of conduction, radiation, evaporation, boiling, and variable properties. Two evaporation models were studied and the results were compared with experimental data for stainless steel. The penetration depth was also calculated for lead, a low boiling temperature material, and the results were compared with previous calculations and with experimental data.

The physics of fusion welding. Part 1: The electric arc in welding

Abstract: The electrical characteristics of the arc as used in welding technology are considered, giving some attention to problems of arc reignition and stability, and to the means of assessing the suitability of power sources for welding operations. The behaviour of thermionic and nonthermionic cathodes is reviewed and recent developments in the investigation of nonthermionic cathodes are described. Work on the arc column is divided into sections on properties and fluid dynamics, following which the behaviour of the column during welding is reviewed in relation to specific problems such as arc force, arc stiffness, magnetic effects and arc blow. A final section covers the anode, particularly in relation to the tungsten/argon arc and its use in the gas tungsten arc welding process.

Inclusion effects on submerged-arc weld microstructure

Abstract: Bead-on-plate welds were produced using twenty four fused reagent grade submerged arc welding fluxes, selected from three flux systems, SiO2-MnO-FeO, MnO-CaF2 and SiO2-CaO-CaF2. The welds were processed using AISI 1010 steel coupons, and a Lincoln L-50 AWS type A5.17) welding wire with a constant heat input of 3.0 kJ mm−1. The three flux systems were selected because of their different oxygen potentials and their ability to produce welds with a wide oxygen range (70 to 1400 p.p.m.). Qualitative and quantitative metallography and chemical analysis were performed on the welds. Inclusion morphology and volume fraction are observed to be affected by flux composition Inclusions of 1 μm in size and greater are associated with grain boundary and blocky proeutectoid ferrites, while inclusions 0.64 μm and smaller are linked with the presence of acicular ferrite.

Consumable welding electrode and method of using same

Abstract: An improved consumable electric arc welding electrode having an outer ferrous metal sheath, such as a low carbon steel sheath, which is formed around a generally concentric core of compressed particulate fill material to be used for depositing an all weld metal of steel in multiple passes with a minimum tensile strength of about 72,000 psi and a minimum elongation of about 22 percent wherein the fill material includes aluminum in an amount greater than about 1.50 percent of the total electrode weight to provide a correlated amount of aluminum in the deposited metal. This improvement involves a particulate fill material producing a combination of nickel and manganese content in the range of 2.5-4.0 percent by weight of the total electrode with the nickel being greater than about 0.5 percent, the manganese being in the range of 0.7-2.0 percent and both the aluminum and the carbon in the fill material being properly controlled whereby the deposited all weld metal, when the sheath and core materials are melted and deposited, has a percentage by weight of aluminum greater than about 1.20 percent and a percentage of carbon by weight of less than about 0.12 percent.

A Study on the Three-Dimensional Analysis of the Transient Temperature Distribution in Gas Tungsten Arc Welding:

Abstract: The transient temperature distribution in the gas tungsten arc (GTA) welding process was analysed by employing a three-dimensional finite element model. In the formulation, the solution domain which moves with the welding heat source was introduced to minimize the number of elements, and consequently the computation time of the three-dimensional program. Since the moving solution domain is small compared with the real weld structure, there are two kinds of boundaries, namely, solid metal-atmosphere boundary and solid metalsolid metal boundary. The heat loss through the solid metal-solid metal boundary was considered through a conduction heat flow and the heat flow through the solid metal-atmosphere boundary through a convection heat flow. As the solution domain moves with the progress of welding, new boundary conditions and new elements were generated in front of the heat source, while some elements disappeared in the rear of it. The initial temperature distribution of the new elements was determined by c...

Method for controlling gas metal arc welding

Abstract: The heat input and mass input in a Gas Metal Arc welding process are controlled by a method that comprises calculating appropriate values for weld speed, filler wire feed rate and an expected value for the welding current by algorithmic function means, applying such values for weld speed and filler wire feed rate to the welding process, measuring the welding current, comparing the measured current to the calculated current, using said comparison to calculate corrections for the weld speed and filler wire feed rate, and applying corrections.

Monitoring facility for electric welding equipment, in particular as used for metal box manufacture

Abstract: The invention relates to the art field of resistance welding utilizing rollers in conjunction with a continuous copper wire electrode and effected with welding current that remains constant on average, at least within each half-period. According to the invention, the weld between members (generally tinned metal strip) can be monitored by measuring the current that flows through the circuit created by the electrode wire, this being a function of the welding resistance that registers between the welding rollers; the value of the current thus measured is compensated in respect of the inductive effects produced by the magnetic field originating from the welding current, and relayed in digital form to a microprocessor that compares it with given maximum and minimum limits within which the reading must fall for quality of the weld to be assured.

Welding arc initiator

Abstract: An improved inert gas shielded tungsten arc welder is disclosed of the type wherein a tungsten electrode is shielded within a flowing inert gas, and, an arc, following ignition, burns between the energized tungsten electrode and a workpiece. The improvement comprises in combination with the tungsten electrode, a starting laser focused upon the tungsten electrode which to ignite the electrode heats a spot on the energized electrode sufficient for formation of a thermionic arc. Interference problems associated with high frequency starters are thus overcome.

Ac arc welding power source

Abstract: PURPOSE: To prevent switching elements from being broken down by arranging constitution to absorb the counter electromotive force by a reactor by a free wheel circuit to prevent the counter electromotive force from being impressed on the switching elements at the time of changing over polarity with AC arc welding. CONSTITUTION: At the time of changing over an arc current from a reversed polarity side current to a straight polarity side current, after the switching element S 1 is turned off, a free wheel current is carried for a prescribed period of time and the switching element S 3 is then turned off. After this, after an interval of a dead time period, the switching element S 2 to control the straight polarity side current and the switching element S 4 to apply the straight polarity free wheel current are turned on. By this method, it is prevented that the counter electromotive force is impressed on the switching elements and the switching elements are broken down. COPYRIGHT: (C)1989,JPO&Japio

Titanium-clad steel and a method for the manufacture thereof

Abstract: A titanium-clad steel and a method for its manufacture are disclosed. The titanium-clad steel comprises a steel base metal, a nickel insert which is bonded to the steel base metal, a low-carbon ferrous metal insert which contains at most 0.01 weight % of carbon and which is bonded to the nickel insert, and cladding of a titanium-based metal which is bonded to the low-carbon ferrous metal insert. A manufacturing method therefor comprises preparing a 4-layer clad assembly comprising the above materials, sealing the outer seams of the clad assembly by shielded arc welding, performing degassing treatment on at least the confronting surfaces of the inserts, heating the clad assembly to a temperature of 500°-1050° C., and performing hot rolling. The resulting titanium-clad steel has a high bonding strength.

Method of forming stub ends

Abstract: A method of forming stub ends used for joining pipes together by depositing successive layers of weld metal on the outer circumference of a rotating length of pipe. Initial layers having a common forward edge but of decreasing width are deposited to provide metal for the machining of a radius joining the flange to the pipe. Thereafter, successive layers of weld metal of substantially the same width and the same common forward edge are deposited to form the flange. The method is preferably practiced by inert gas shielded pinch arc welding to provide an integral flanged stub end made up completely of weld metal. The resulting structure is substantially uniform and homogeneous with a desirable grain structure, and is pore and defect free. The method further provides economical manufacture of flanged stub ends with relatively little waste of materials.

Arc welding capable of multi-mode welding

Abstract: An electric welding control circuit incorporates a mode selection switch to enable the welder to be used in a selected one of several operational modes, such as a rod welder, a MIG, a TIG or a spot/stitch welder. A wire feed motor is used in the MIG mode to feed welding wire to the electrodes. A regulating circuit controls the speed of the wire feed motor as a function of the welding electrode voltage. A zener diode in the regulating circuit turns on a switching transistor to cause the feed motor to run at a normal speed when the voltage is between predetermined limits and a second zener diode senses a loss of arc to slow the feed. In a spot/stitch mode, a timer is used to time the spot periods, the timer operation being dependent on the presence of an arc as detected by the regulating circuit so as to commence the timed period when the arc is struck.

Arc length control for plasma welding

Abstract: For use with plasma arc welding apparatus, a control system is set forth. The plasma arc welding apparatus includes a plasma arc power supply (12), a contactor (20), and an electrode assembly for moving the electrode (32) relative to a work piece (22). The electrode assembly is raised or lowered by a drive motor (24). The present apparatus includes plasma arc adapter (48) connected across the power supply to measure the voltage across the plasma arc. The plasma arc adapter forms a DC output signal input to a differential amplifier (60). A second input (58) is defined by an adjustable resistor (56) connected to a DC voltage supply to enable operator control. The differential amplifier forms an output difference signal provided to an adder circuit (64). The adder circuit then connects with a power amplifier (68) which forms the driving signal for the motor. In addition, the motor connects to a tachometer (70) which forms a feedback signal delivered to the adder to provide damping, thereby avoiding servo loop overshoot.

Covered arc-welding electrode

Abstract: A covered arc welding electrode includes a steel core wire and a flux which is applied to the outside periphery of said steel core wire. The welding electrode can form a superior crack-resisting weld zone even if fluctuating stresses are continually applied to a base metal while the base metal is welded. The flux includes 40 to 60% metal carbonate, 10 to 25% metal fluoride and 4 to 25 metal oxide by weight. The flux comprises 24 to 32% of the total weight of said electrode. The composition of the welding electrode includes 0.005 to 0.05% carbon, 0.1 to 1.1% silicon, 1.5 to 2.5% manganese, not more than 0.007% sulfur and not more than 0.25% nickel by weight and the manganese/sulfur ratio is more than or equal to 350 to 1. In addition, the welding electrode can include 0.01 to 0.10% rare earth metal by weight. In which case, the Mn content may be 1.0 to 2.5% by weight and the manganese/sulfur ratio may be more than or equal to 270 to 1. In addition, the composition of the welding electrode can include titanium and zirconium, the total content of which may be less than or equal to 1.2% the total weight of the electrode, and/or aluminum and magnesium, the total content of which may be less than or equal to 1.2% of the total weight of the electrode.

The physics of fusion welding. Part 2: Mass transfer and heat flow

Abstract: The second part of the review covers mass and heat transfer in fusion welding, other than that specifically related to the arc column. Metal transfer is considered under the headings of flux-shielded and gas-shielded processes. The major portion of experimental work is concerned with the gas-shielded processes, for which a substantial amount of quantitative information is available on such matters as transfer modes, drop rates, drop temperature, the effect of shielding gas and the effect of pressure. The development of specialised power sources for the gas metal arc process is considered. Flow in the weld pool has been studied for those cases (for example, submerged arc welding) where it is mechanically induced, and for gas tungsten arc welds where electromagnetic or surface tension forces may dominate. The extensive literature on heat flow in the workpiece is briefly reviewed, and recent developments in welding process modelling are surveyed.

Method and apparatus for generating an ultra low current plasma arc

Abstract: A method and apparatus for generating a plasma arc used in arc welding, arc transformation hardening, minute working, etc. A plasma gas used for generating a plasma arc includes xenon. A tungsten electrode having a diameter of 0.5 millimeters or less is used. Thus, an extremely low plasma arc current of 0.1 amperes or less can be produced in a stabilized manner.

The Weldability of an Al-Li-Cu Alloy

Abstract: The development of low-density aluminum-lithium alloys for aerospace applications provides industry with an attractive alternative to fiber-reinforced composites for reducing weight while maintaining the fabrication cost advantages of aluminum. In this study, gas metal arc (GMA), gas tungsten arc (GTA), and electron beam (EB) welding processes were used to evaluate the potential fusion weld-ability of alloy 2090 (Al-2.2 Li-2.7 Cu-0.12 Zr). The results indicate that, with proper filler alloy selection, 2090 may be easily welded with a low sensitivity to weld solidification cracking. The weld porosity of 2090, the source of which is hydrogen enriched surface oxides, may be eliminated by chemically or mechanically milling the surface prior to welding. The dominant modification in the heat-affected zone of 2090 weldments is dissolution of strengthening phases. This degradation is reduced by the use of high energy density heat sources, such as an electron beam, or post-weld thermal treatments.

Microstructure and phase transformations in duplex 316 manual metal arc weld metals: the role of carbon

Abstract: The nature and kinetics of the phase transformation of metastable δ-ferrite in two duplex stainless steel manual metal arc weld metals has been studied at two carbon levels. 0.042 and 0.076 w t%. The lean deposit exhibited a rapid transformation to intermetallic phases on post-weld heat treatment, whilst the higher carbon deposit retained sable δ-ferrite after similar heat treatment. These results appear to be consistent with previously published transformation models for similar materials.

Optical Spectral Radiometric/Laser Reflectance Method For Noninvasive Measurement Of Weld Pool Surface Temperatures

Abstract: A unique experimental method has been developed for measuring weld pool surface temperatures. An equation for determining temperature was developed based on Planck's blackbody spectral distribution of emissive power, the definition of spectral directional emissivity, Lambert's cosine law for diffuse emitters, and Kirchhoff's law for spectral directional reflectivity. The necessary measurements are the spectral directional emissive power and the spectral directional emissivity of the weld pool surface. Detailed pool surface temperature measurements were made of gas tungsten arc (GTA) welding of 1.5mm thick stainless steel (SS) 304 plates using an argon cover gas. Because argon plasma arc spectroscopy measurements over molten SS 304 revealed insufficient emission gaps, the spectral emissive power was measured by high speed film radiometry as the arc was shut off so as to obtain information at the instant the obscuring arc emissions disappear. Similar measurements were made of the spectral directional reflectivity (and thus the spectral directional emissivity) by reflecting a focused laser beam off the weld pool. Detailed weld pool surface temperature maps were generated.

Agricultural Mechanics: Fundamentals & Applications

Abstract: Part I: Exploring careers in agricultural mechanics. Mechanics in the world of agriculture. Career options in agricultural mechanics. Part II: Using the agricultural mechanics shop. Shop orientation and procedures. Personal safety in agricultural mechanics. Reducing hazards in agricultural mechanics. Shop clean-up and organization. Part III: Hand woodworking and metal working. Hand tools, fasteners and hardware. Layout tools and procedures. Selecting, cutting and shaping wood. Fastening wood. Finishing wood. Indentifying, making, cutting and bending metal. Fastening metal. Part IV: Power tools in the agricultural mechanics shop. Portable power tools. Wood-working with power machines. Metalworking with power machines. Part V: Project planning. Sketching and drawing projects. Figuring a bill of materials. Selecting, planning and building a project. Part VI: Tool fitting. Repairing and reconditioning tools. Sharpening tools. Part VII: Gas heating, cutting, brazing and welding. Using propane and oxyacetylene equipment. Cutting with oxyfuels. Brazing and welding with oxyacetylene. Part VIII: Arc welding. Selecting and using arc welding equipment. Arc welding mild steel. Part IX: Painting. Preparing wood and metal for painting. Selecting and applying painting materials. Part X: Small gas engines. Small engine maintenance. Small engine adjustment and repair. Part XI: Electricity and electronincs. Electrical principles and wiring materials. Installing branch circuits. Electronics in agriculture. Motors and controls. Part XII: Plumbing, hydraulic and pneumatic systems. Plumbing. Drainage and irrigation technology. Hydraulic, pneumatic and robotic power. Part XIII: Concrete and masonry. Part XIV: Agricultural structures. Planning and constructing agricultural structures. Aquaculture, greenhouse and hydroponics structures.

Control of deposition rates in hot wire TIG welding

Abstract: (1987). Control of deposition rates in hot wire TIG welding. Welding International: Vol. 1, No. 8, pp. 736-742.

Conceptual development of an adaptive real-time seam tracker for welding automation

Abstract: The paper presents the concept of a real-time seam tracking system for welding automation and the initial design for building a prototype. The ARTIST - Adaptive Real-Time Intelligent Seam Tracker - uses a robot-held, laser based vision system for automation of arc welding processes, and is currently under development at the Applied Research Laboratory of The Pennsylvania State University. The design of ARTIST builds upon the concept of a zero-pass technique where 3D information of the seam geometry is collected and processed for real time guidance and control of the welding torch trailing behind the laser-based vision sensor. This zero-pass concept eliminates the need for pre-programming of the weld path and thus potentially enhances the welding cycle time for small batches. The ARTIST is designed to support multipass arc welding and to handle any tack welds which are encountered during the seam welding operation.