Showing papers on "Electric resistance welding published in 1981"

Weld quality monitor

Abstract: Weld arc voltage, weld arc current and weld arc travel speed are monitoredn a real-time basis during the welding process. Each monitored quantity or parameter is compared directly with a reference value indicative of a high quality weld, and an alarm is activated when a preselected variation in the measured and the reference quantities occurs. The monitored quantities are also used to calculate additional welding parameters, including heat input, weld bead area and cooling rate. These parameters are also compared to ideal reference values in order to control weld quality. The sensors used for measuring the welding parameters are selected so as to provide minimal interference with the welding process. For example, Hall effect transductors are used for current measurements, while a unique opto-electronic noncontacting sensor is used for measuring the weld speed.

Low expansion laser welding arrangement

Abstract: An arrangement for laser beam welding wherein at least one of the components being welded is formed of a material which is substantially transparent to radiation at the wavelength of the laser welding beam. A layer of welding material is placed over the surface area of the weld joint, and is a type of material which is substantially absorbent of radiation at the wavelength of the laser welding beam. The welding material is then irradiated by the laser beam through the component which is substantially transparent thereto for a sufficient period of time to cause melting of the welding material and fusion thereof to the two components being welded. The present invention has particular applicability to welding with a Nd-YAG laser of components formed of silica-containing material, such as fused silica or titanium silicate, and wherein the welding material placed at the weld surface area is a titanium based material. The present invention is also particularly attractive for weld locations which are physically inaccessible to direct irradiation, but can be irradiated through the material which is substantially transparent to the laser welding beam.

Infrared Temperature Sensing of Cooling Rates for Arc Welding Control.

Abstract: : It is known that the weld metal mechanical properties of quenched and tempered steels are dependent upon cooling rate, which is presently indirectly controlled by specification of heat input. A method to directly control weld metal cooling rate would result in more consistency in achieving required mechanical properties. In the present investigation the use of commercial infrared sensing equipment was explored as a means of real-time monitoring of weld metal cooling rate. Infrared equipment has a distinct advantage over other temperature detecting systems in that it requires no physical contact with the work, thus affording a minimum amount of interference with the welding process, and is therefore a potentially useful detector for an adaptive feedback welding control system based on cooling rate. It was found that infrared thermography appears to offer considerable promise for welding control by providing weld metal cooling rates which are: (1) reproducible, (2) sensitive to variations in welding conditions, and (3) relatable to cooling rates as measured by plunged thermocouples. (Author)

A Computational Model of Backlay Welding for Controlling Residual Stresses in Welded Pipes

Abstract: Intergranular Stress Corrosion Cracking (IGSCC) has been a problem in Boiling Water Reactor (BWR) piping systems. One method for retarding IGSCC is to eliminate tensile residual stresses at the pipe inner surface in the heat affected zone produced by the welding process. A method called backlay welding can be effective in producing compressive residual stresses at the pipe inner surface. This paper describes a computational model and its use in examining the effectiveness of the backlay welding process. The model has demonstrated an ability to predict weld-induced residual stresses for a variety of pipe sizes and welding conditions. Computational results for backlay welding are in agreement with residual stress data. The mechanisms causing residual stresses and the effect of the number of backlay weld layers on residual stresses are discussed.

Electrical stud welding device for welding studs of different diameters without pre-testing adjusting welds

Abstract: The disclosure concerns an electrical stud-welding device with a welding head and a stud holder fastened thereto in a detachable manner. The stud-welding device is of the type that can be regulated with respect to various welding parameters, such as charging voltage, capacitance, plunge velocity, weld current, weld time, and plunge damping and providing means for weld studs of different dimensions without the need to perform test welds, thus also allowing automatic change of the stud holder, by designing the stud holder as a data carrier for several specific, variable welding-parameters, and data-acquisition units which can be acted upon by the stud holder arranged on the stud-welding device and a central, device-specific data-processing unit associated with the stud-welding device, and provided for the acquired data, which unit sets the controlled variables in accordance with the data that were determined.

Feedback welder control system

Abstract: A control system for resistance welders of the type in which welding current is supplied to a workpiece through a transformer. The system assures weld quality by monitoring the change in resistance across the weld during the welding operation without the need for auxillary leads or separate sensing transducers at or near the workpiece and automatically terminates the welding current when a quality weld is made as determined by resistivity characteristics of the weld. The system monitors discrete changes in the characteristics of the current in the primary of the welding transformer which occur as a result of changes in weld resistance. The system compares the monitored current characteristics of the welding current with a plurality of parameters indicative of a quality weld and terminates the welding current when a selected number of monitored characteristics are within selected parameters.

Welding wire for automatic arc welding

Abstract: A welding wire for automatic arc welding, which is particularly suitable for use in build-up welding operation for the purpose of providing hard surface to a metal die. The welding wire consists of a continuous tubular metal casing and a core composition charged in the interior of the casing and comprises such amounts of Ni, Si, B, Nb and C as essential alloying elements that the deposited metal contains at least 40% of Ni, 3-8% of Si, 0.1-0.4% of B, 0.3-1.8% of Nb and 0.2-1.5% of C, all by weight. Preferably, either a practically pure Ni strip or an Fe-Ni alloy strip is used as the material of the casing, and the core composition in the form of a powder mixture contains necessary amounts of Ni, Si, B, Nb and C, optionally with the addition of a small amount of Zr. The deposited metal given by this welding wire has high wear resistance and good antifrictional property and seldom suffers from weld cracks.

Power factor monitoring and control system for resistance welding

Abstract: A power factor monitoring and control system for controlling the quality of a spot weld made in the automotive industry on assembly line welders (36). The quality and strength of a spot weld can be correlated to a drop in resistance (74) during the fusion process. Rather than measuring this resistive drop at the welding electrodes by attaching external sensing means thereto, the control system of the present invention makes use of the phenomenon that a resistive drop also causes a change in the total load power factor (50) further resulting in a change to the current extinction angle of a weld half cycle. By determining the amount of increase or decrease that has occurred in the current extinction angle during a weld or a group of welds, a basis for the control of the welding heat is obtained.

Projection for resistance welding of soft metals

Abstract: A projection for use in electrical resistance welding of sheet metals and thin-wall parts, a method of fabricating such projection and the use of the same are disclosed. The flanks of the projection possess internally thereof an angle of about 40° to 75° and externally an angle of about 40° to 100°, and the strength of the material at the region of the flanks is about 50% greater than the strength of the neighboring basic material. The method of forming the projection contemplates fabricating the same through plastic deformation of the basic material and the dimensionally exact shaping is accomplished by compression molding of the flowable metal between a punch and die of a tool.

Microstructure in the weld region in seam welded and resistance welded Zircaloy 4 tubing

Abstract: The microstructure of tungsten inert gas (TIG)-arc welding and resistance welding in Zircaloy 4 tubing is described in relation to the phases present. Differences in microstructure between the weld zone and base tubing are discussed in terms of the phase transformations that take place during the very different thermal cycles occurring in both processes and a comparison between them is made. A feature of the weld region is the presence of a coarse grained Widmanstatten structure in the TIG welding while a martensitic-type structure or very fine Widmanstatten structure is present in resistance welding.

Resistance welding system for projection welding

Abstract: A resistance welding system having a low-inertia movable welding head coupled to a stationary welding transformer which is of low mutual reactance. Through an appropriate timing circuit and control, a high-energy pulse of current, of very short time duration, is transmitted through the welding transformer to the movable welding head. The welding head, which contacts a projection on overlapping components, effects a rapid welding of the components, and the welding head rapidly follows up the melting of the projection due to its low inertia.

Highhtensile electricallyyconductive copper alloy

Abstract: PURPOSE:To obtain a Cu alloy having superior electrical conductivity and mechanical strength by alloying Cu with a specified amount of Cr and Zr or Cr, Zr and Si. CONSTITUTION:Cu is alloyed with 0.3-1.5wt% Cr and 0.03-0.14wt% Zr or further alloyed with 0.01-0.08wt% Si. The resulting Cu alloy has superior electrical conductivity and mechanical strength, and it is used as a superior electrode material for resistance welding and a superior material for electrical apparatus.

Resistance welding control method

Abstract: PURPOSE:To equalize and improve a welding quality, by operating a firing angle of a switching element so that inter-welding electrode voltage exceeds a reference value which has been decided in advance, by one degree at least, in case of spot welding for controlling a welding current. CONSTITUTION:During a constant limited time t1 from start of power application, it only compares interchip voltage of each cycle and a reference value V0. In case when a current has flowed normally, the interchip voltage attains the reference value V0 after t2 from start of operation, therefore, in the section of t2, welding is performed until power application is finished without performing a changing operation of a firing angle of a switching element such as a thyristor, etc. In case when there is no cycle at all of interchip voltage exceeding V0 in the section t1 as shown by a broken line, owing to drop of input voltage, etc., the firing angle is operated by a prescribed extent in the section t2. This operation is continuously executed until the interchip voltage attains to V0. When it attains to V0 at the point of Tp, after Tp, the interchip voltage is monitored, and until it shows a decreasing tendency, the firing angle is operated in the direction where a current is decreased by a prescribed extent in order at every cycle.

Copper bimetal brazed resistance welding electrode

Abstract: A bi-metal resistance welding electrode has a dispersion strengthened copper tip and a high conductivity copper shank. The electrode is made by forming a tip member in two successive upsetting operations to produce a tip member having a coating of high conductivity copper covering substantially all of one end thereof. A solid, high conductivity copper, cylindrical billet is formed and brazed to the tip member at its coated end to form an extrusion blank. The extrusion blank is back extruded with the high conductivity copper material being worked substantially, while only partially back extruding the tip portion of the extrusion blank.

Device and method for repairing conductor path breaks by welding

Abstract: To repair conductor path interruptions on printed circuit boards by means of micro-resistance welding, a specifically shaped metallic part is sucked on a central electrode by use of vacuum. The central electrode lowers the part so as to bridge the conductor path interruption to be repaired. On each side of the central electrode an outer electrode is provided which are lowered into contact with ends of the shaped part to provide independent micro-resistance welding at each end thereof by use of separate welding pulses, with the central electrode functioning in common for each welding.

Method and system for dual control of resistance welding

Abstract: A method and system for controlling resistance welding whereby the preferred quality of resistance welding can be ensured automatically during the welding process by controlling the electrode pressure so that the electrode resistance changes in accordance with a reference resistance curve, or by additionally controlling the electrode voltage so that the electrode voltage changes in accordance with a reference voltage curve. The system according to the present invention comprises an electrode voltage sensor, an electrode current sensor, a reference resistance generator, a reference voltage generator, a differential amplifier, a pressure control device, a current controller and so on.

Spot welding method of high tension steel plate

Abstract: PURPOSE:To improve fatigue strength of a spot welding joint, by specifying the relation between a welding current and time, and between a temper current and time, in a method for executing temper electrification after spot welding electrification to high tension steel. CONSTITUTION:A high tension steel plate which contains 0.06-0.40pts.wt. C, and has 0.06-0.06% Ceq (carbon equivalent) shown by the expressionI, and >=35kg/mm. tensile strength is subjected to spot welding electrification, and after that, spot welding is executed by temper electrification. In this case, a value (index) of the expression II by a temper electrification current It, a welding electrification current Io, a temper electrification time Tt and a welding electrification time To is set to 0.25-0.82. This value has a physical meaning showing a ratio of calorie by electrification, and fatigue strength can be improved beyond the limits of the condition for improving the conventional static strength.

Resistance welding machine

Abstract: The resistance welding machine of this invention has an arm carrying a movable electrode and provided with a supporting bore, a power receiving bushing fitted in the supporting bore, and a power feeding shaft mounted on the main body of the welding machine on which a second electrode, is also mounted The power feeding shaft is received by the bore of the power receiving bush to support the arm while supplying electric power to the movable electrode A plurality of grooves are formed in the inner peripheral surface of the power receiving bushing to receive powders generated as a result of local wear due to sliding contact between the power feeding shaft and the power receiving bushing The grooves are filled with grease which adsorbs and holds the powders

Explosion Welding: A Review

Abstract: A general review of explosion welding with particular emphasis on metallurgical effects is presented. Explosion welding is basically a solid-phase welding process, in which explosives are used to accelerate the parts to be joined into a high velocity oblique collisions, is fundamental to the welding process. The jetting action coupled with the collapsing flyer plate produce a unique weld interface, with very interesting metallurgical properties. The relationship of the welding parameters to the metallurgical properties is discussed.

Method and apparatus for butt welding of plastic pipes of large diameter

Abstract: The welding apparatus serves for the purpose of butt-welding of plastic pipes of diameters larger than 500 mm. All the work is performed by means of the welding apparatus from inside the pipe. Thereby the working time is reduced, the welding quality ensured, and the installation becomes faster. Lifting cranes and heating tents become unnecessary. A novelty is also the possibility of welding pipes together at an angle position. As the welding apparatus is collapsible, it may also be advantageously used for repair work on old pipes in the ground (relining), with a minimum exposure of the pipes.

Method of and apparatus for producing can bodies welded along the longitudinal seam

Abstract: In conventional methods for welding can bodies along their longitudinal seams, high frequency substantially rectangular a.c. currents are used for the welding current to avoid the problem of arcing found in d.c. welders. However, the high frequency a.c. current causes an undesirable degree of heating which produces eddy currents and necessitates cooling equipment. To overcome this problem, a method of producing can bodies welded along their longitudinal seam is provided in which the length of a half wave of the substantially rectangular welding current is matched in length and concurrent with the amount of time required for a can body to pass between the welding electrodes.

Method and device for determining quality in resistance welding

Abstract: A device (for example, Figure 6) according to the invention and employing a suitable method defines the welding quality achieved in a resistance-welding operation as "good" or "reject" by independently or simultaneously comparing the values obtained in each case for the electrode voltage, the electrode current flow time, the number of electrode voltage pulses above an initial value and/or the integral of a difference between the excess of the electrode voltage with respect to a basic voltage and said basic voltage with appropriate reference values, and, in addition, by also comparing the resistance measured between the electrodes (2a, 2b) with a reference resistance value. The relatively inexpensive device determines the welding quality with high precision even if shunt current paths are produced by deformed or pinched electrode tips.

Method for fabricating open web steel joists

Abstract: In the method of welding open web steel joists a chord member is formed by bending a web in an undulating configuration. The chord is welded to the webs by simultaneously clamping and resistance welding to form four welds. The weld current is applied by a series of time controlled intermittent impulses of electrical current. The weld electrodes used are of unequal resistance so as to balance the heat generated.

Method and system for determining weld quality in resistance welding

Abstract: A method and system for determining weld quality in resistance welding in such a manner that acceptance or unacceptance is determined by comparing with their respective reference values the electrode voltage, the electrode current time, the number of electrode voltage pulse signals in excess of the reference value, and the integral of difference between the electrode voltage in excess of a base voltage and the base voltage, independently or simultaneously, in addition to the comparison of the electrode resistance with its reference value. The relatively low-priced system according to the present invention can determining weld quality accurately even when the electrode tips are deformed or crushed so as to form other current path areas.

Control system for resistance welding

Abstract: A system for resistance welding in which the welding voltage between the electrodes is controlled by changing the pressure applied to the electrodes or the firing phase angle of the welding current in accordance with a reference voltage curve or a reference voltage integration curve. The system comprises a voltage sensor, a reference voltage generator, a differential amplifier, and a pressure control device, or a calculating unit for determining an appropriate firing phase angle of the welding current. The system thus improved can ensure a stable, good welding quality, since the welding voltage is always controlled by a series of optimum welding voltages, during the welding process, in accordance with a reference voltage curve with respect to time, preferably in terms of cycles of the welding current.

Electric resistance welding using energy beam in combination

Abstract: PURPOSE:To perform welding of high quality free from welding defects using relatively simple device by irradiating an energy beam to an apex which becomes the welding point of an wedge-shaped object to be welded and making combined use with electric resistance welding. CONSTITUTION:High frequency voltage is applied to contacts 4, 4 disposed on the edge part 2 of a tubular body 1 for manufacturing an electric welded tube etc. to heat the edge part 2, and welding is performed at the apex of the wedge- shape. An energy beam F is irradiated in the direction of the apex of the wedge by a laser irradiating device and mirrors 6, 7, 8, 9 etc., and the corner part 21 and thick central part 22 of the edge part are heated uniformly to prevent occurrence of welding deffects. Efficiency of uniform heating can be increased by supplying highly ionizing gas to a space just in front of the apex of the wedge of the weld zone to generate plasma, and work efficiency of welding can be improved by controlling heat input of welding automatically.

Method and device for production of welded can body

Abstract: PURPOSE:To prevent splashing by peak current and to make stable welding in a wide welding current range possible in welding a can body of a non-ferrous metallic plate or various surface treated steel plates as a blank material, by forming the welding current waveform into a square waveform. CONSTITUTION:In the stage of using thin steel sheets such as tin plates, TFS, zinc plated steel sheets or the like or sheets of non-ferrous metals such as Al, Cu alloys or the like as a blank material, superposing both end edge parts thereof and subjecting said parts to seam welding, a rectifier for voltage controllable DC current, a switching circuit for converting the DC current to square wave AC and a chopping mechanism for controlling the switching circuit are contained in a welding power source. If the welding current is converted to the square wave current having no peaks with said power source, there is no plashing by peak current because of the absence of peak current unlike with ordinary sine wave current, and the stable welding is made possible in a wide current value range.

Electrical energy source for a resistance welding machine

Abstract: The electric energy source for a resistance-welder comprises a static reversing device, a welding transformer, and a first static frequency converter (10) comprised of semiconductor elements, of which the output alternating voltage has a frequency and a pulse wave-form different from the frequency and the pulse wave-form of the supply voltage provided to the reversing device. In order to vary on a large range the pulse wave-form, the amplitude and the pulse ratio, the source comprises at least a second frequency converter (11) mounted in parallel on the first frequency converter (10) and of which the output alternating voltage may be added, in phase synchronism, to the output alternating voltage of the first frequency converter (10) in the primary circuit of the welding transformer (12).