Showing papers on "Welding published in 1987"

Audio visual instructional system

Abstract: A tool-workpiece instructional system is provided for simulating operation on a workpiece in the form of a welding site as shown on a display, by a student using a tool such as a welding torch simulator. The torch is a mock-up of as real torch, having mock values and torch tip, but is not supplied with any gas. A light pen and mercury switches are mounted inside to detect torch position and angular position relative to the display. A computer with a control program uses information regarding parameters of torch location relative to the display, including torch angle, torch distance to the display, torch position as projected on the plane of the display, welding rod position (as detected by a touch screen on top of the display) and oxygen and acetylene valve positions of the welding torch, and uses the parameters to determine what would happen to a welding site during a real weld and addresses appropriate segments in a video disc player to display a simulation of the welding site in real time.

Using infrared imaging to monitor and control welding

Abstract: The technique and arrangement of distributed, real time, intelligent control of welding including IR detection and measurement of process conditions, and controlling process parameters in view of a knowledge base including a predetermined rule set for interpreting the results of IR detection. The arrangement includes a multilevel communication scheme internally and between hardware nodes of the arrangement, and the data-driven scheduling of inference processes under direction of a semantic network.

Device for training welders

Abstract: A device for training, evaluating and providing practice for welders and particularly welders and welder students that use MIG, TIG and welding devices that employ movable consumable welding rods The device includes a video monitor having a cathode ray tube, the face of which has visual displays thereon, including displays from which simulated welding parameters can be entered and displays which simulate different welding joints with a welding target to be followed by the operator while holding the selected welding tool The present device uses a microprocessor and related electronic devices programmed to generate the displays and to control the various machine operations The device also includes a unique way to produce the various control responses necessary to the operation including optical and electromagnetic responses

Methods for weld repairing hollow, air cooled turbine blades and vanes

Abstract: A mask particularly useful in the weld repair of air cooled gas turbine blades and vanes contains a mixture of ceramic particles in a liquid carrier. The mask is applied onto the surface of the blade or vane, and into the cooling holes. Following a sintering treatment, an inert, thermally stable, electrically nonconductive ceramic mask is produced, which is easily removed after welding.

Effect of rapid solidification on stainless steel weld metal microstructures and its implications on the Schaeffler diagram

Abstract: An investigation was carried out to determine the effect of rapid solidification on the weld metal microstructure of austenitic stainless steels and its implication on the ferrite constitution diagram. A wide variety of stainless steels were laser beam welded at different welding speeds and laser power levels. The results indicate that both weld pool cooling rate and the postsolidification solid-state cooling rates have a profound effect on the microstructures. For the steels investigated, the microstructures ranged from duplex austenite ([gamma]) + ferritic ([sigma]) to fully austenitic or fully ferritic. These microstructures were found to be sensitive to both cooling rates and composition. The observed results are rationalized based on rapid solidification theory. Observations of this investigation indicate that solidification rates and postsolidification cooling rates have a profound effect on the observed microstructures, thus making it impossible to predict the microstructures of rapidly cooled weld metal from the conventional constitution diagrams. The influence of the observations made in this investigation on the Schaeffler diagram is demonstrated, and possible corrections to the constitution diagram incorporating the cooling rate effects are proposed. 23 refs., 17 figs., 3 tabs.

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.

A keyhole model in penetration welding with a laser

Abstract: Discusses the interaction of conditions in the liquid metal surrounding the keyhole which is formed when a laser is used as the source of power for welding, with conditions in the vapor itself. The transfer of power and matter across the interface is considered, and a simple model set up for the energy interchange and vapor flow in the keyhole itself. The principal processes are identified. The model is then used to calculate keyhole shapes, and the variation with depth of the related quantities is found.

Mechanism of alloying element vaporization during laser welding

Abstract: Vaporization of alloying elements is a serious problem in the laser welding of many important engineering alloys. Since the available mass transfer correlations are not applicable for credible assessment of the rates of transport of vaporized species in the gas phase, the role of gas phase mass transfer in the overall vaporization of alloying elements was examined by conducting several critical experiments. The rates of transport of alloying elements in the weld pool were determined from numerically computed fluid flow fields. Since the weld pool is surrounded by plasma during laser welding, the role of plasma in the vaporization of alloying elements was physically modeled by allowing molten copper drops to vaporize isothermally both in the presence and absence of plasma. The transport of alloying elements in both liquid and gas phases was found to be rapid and the overall vaporization rates were controlled by the plasma influenced intrinsic vaporization of alloying elements at the weld pool surface. The experimentally obtained rates of vaporization of alloying elements from laser melted stainless steel weld pools were compared with the corresponding theoretically calculated values.

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.

Method for laser beam welding metal matrix composite components

Abstract: A substantially homogeneous metal matrix composite conduction weld between first and second metal matrix composite components is formed by placing the components into abutting position, with a major portion thereof spaced from each other, and directing a laser beam through the spacing onto the intersection and oscillating the beam across the intersection to form a shallow pool of metal matrix composite while feeding a metal matrix composite filler wire into the pool. The laser beam and filler wire are moved along the intersection such that solidification of the molten pool containing the filler wire metal matrix composite is effected, to form the weld line, without separation of the metal matrix composite into separate phases. The filler wire may be preheated and pressure may be applied, either to one or both components in a direction transverse the plane of the intersection or to the weld line in the direction of the plane of the intersection.

Twin spot laser welding

Abstract: A novel multiple spot laser welding apparatus includes a bendable mirror capable of deformation, which receives a laser beam at a single reflective surface thereof. A deformation device deforms the single reflective surface of the bendable mirror to provide a plurality of laser sub-beams to a workpiece, generating laser spots on surfaces thereof. The apparatus can be used in a laser welding method that provides a common weld pool formed by laser spots transverse to the weld seam. Another laser welding method provides multiple laser spots oriented along a weld seam producing a common weld pool therebetween. Still another laser welding method provides multiple laser spots along a weld seam producing distinct weld pools.

Machine vision seam tracking method and apparatus for welding robots

Abstract: The invention relates to a machine vision seam tracking method and apparatus for welding robots, particularly to an apparatus which can automatically detect the deviation between an actual welding seam and a taught path where the apparatus so as to correct the welding path, comprises an image forming means and an image processor. Through the image forming means, a light coming from a common light source, after being condensed and transmitted, can be projected onto a workpiece to form a line of light across the welding seam. A solid state camera disposed along the direction of the welding seam can detect the image of the welding seam which in turn is transmitted to the image processor. The image processor preferably is a microcomputer which comprises software for processing the images respectively formed by the butt, fillet, lap and V-groove joints so as to calculate the deviation, including the positional error across the welding seam as well as the distance variation between the welding torch and the workpiece (the so called height of the welding torch), existing between the actual welding seam and the taught path. A controller of the welding robot can convert the error signals of the welding path into the corresponding data by which the coordinates of the welding robot can be corrected to align with the actual welding seam.

Water cooled semi-automatic welding gun

Abstract: A liquid cooled welding gun assembly is adapted to be operatively connected to a power, gas, and weld wire feed mechanism through a cable assembly and a connector assembly. The welding gun assembly includes a front connector block and the connector assembly includes a rear connector block. Power, gas and cooling liquid hoses are contained within the cable assembly and intercommunicate the connector block of the welding gun assembly with the rear connector block. The welding gun assembly includes a liquid cooled nozzle assembly. In an alternative embodiment, a nozzle of the nozzle assembly has an internal cooling passage therein. The nozzle assembly includes alternative diffusers having longitudinally directed gas flow passages therein. A hose coupling assembly is provided for facilitating connecting and disconnecting the various power, gas and liquid hoses from the conductor blocks. In an alternate embodiment, the connector block is replaced by a robotic body and a robotic conductor tube assembly is attached thereto for robotic welding.

Ultrasonic flaw detecting method and apparatus

Abstract: A method for ultrasonically detecting flaws in a welded portion of a pipe by using an ultrasonic wave phased array probe having an array of a plurality of transducer elements for emitting and receiving ultrasonic wave beams, wherein at least one monitoring probe is located in the vicinity of the welded portion to receive the ultrasonic wave beam, whereby peak values of the ultrasonic wave beams are detected within a predetermined gate, a maximum peak value of the detected peak values is determined to determine a pilot beam having the maximum peak value, and effective beams which reach the portion of the welding portion to be tested are determined from the determined pilot beam.

Laser welding head for sleeve-to-tube welding

Abstract: A laser welding head for welding a sleeve within a tube by fusing the interface between the sleeve and tube with a laser beam. The laser welding head has a cylindrical housing adapted to be inserted inside of the sleeve, a focusing lens for focusing a laser beam transmitted through the housing, and a welding mirror for directing the focused beam out of the housing and into contact with the sleeve. The welding mirror is maintained a predetermined distance from the inside surface of the sleeve and a motor and drive assembly are used to rotate the welding head within the sleeve. Shield gas is supplied to the welding head and passes about the periphery of the focusing lens for cooling the focusing lens and the welding mirror before being discharged into contact with the weld area. A recessed aperture is provided within the discharge outlet to prevent molten material from the weld site from splattering into the housing and onto the mirror or lens. Multiple pass welds are preferred for attaching each end of the sleeve to the tube with the preferred weld paths being either multiple discrete weld paths or continuous overlapping helical weld paths at each end of the sleeve.

Metal demolition shears

Abstract: A heavy duty shear featuring removable knife seats, knife blades and wear plates is disclosed. The removable components serve to protect the shear from excessive wear, and may be replaced with minimal labor in the field and without welding or cutting.

Invertor type DC resistance welding machine

Abstract: Disclosed is an invertor type DC welding machine incorporating constant-voltage control to assure a high and reliable quality of weld. The pulse width of the high-frequency output of the invertor circuit is controlled at the invertor switching rate by the constant-voltage control on a feedback loop basis in which a DC weld voltage applied to the workpieces to be welded between electrodes is detected and is compared with the value of a reference weld voltage to produce an error signal for controlling the operation of the invertor circuit, so that the DC weld voltage is maintained constant regardless of variations in the resistance of the portion to be welded during a welding operation. A timing system is further provided which momentarily monitors the change in the resistance between electrodes to terminate the welding operation at an optimum time after a nugget is produced in the porton to be welded.

Percussion weld monitoring

Abstract: The quality of a percussion weld is sensed by measuring and analyzing certain features of the weld current signature. Instantaneous current is measured by a Hall sensor and permits isolation of the welder from the monitoring system. Weld quality is strongly correlated to the time to vaporize the nib separating the parts, and the dwell time to forge the parts together after nib explosion. A weld is assumed defective if nib time is too short or dwell time is too long. These quality parameters may be supplemented by weld and forge timing, line voltage, and acoustic information; a weld is rejected if any of these are outside of acceptance limits. Experiments on the percussion welding of silver-cadmium oxide to brass show that cadmium-oxide is decomposed and expelled by the forge pressure and the joint is a silver to brass weld.

Rotary welding member made of resin

Abstract: A rotary welding member made of synthetic resin material comprising a post portion, and a disk-shaped flange portion integrally mounted on one end of the post portion and having at least one groove in the mounting surface thereof for permitting air to flow therethrough with respect to an exterior periphery surface portion of the flange portion whereby excess frictional heat generated during the rotary welding process is effectively dissipated.

Method of welding

Abstract: Virgin metal and metal alloy components are welded with and without filler material using a laser without cleaning the surfaces to be joined of mill scale and/or surface oxides, paints grease and other forms of contamination, and without edge preparation. The uncleaned, unprepared surfaces are placed in contact with each other, and a 100% through the thickness laser keyhole weld without filler metal is made in one pass, full penetration is achieved by two laser keyhole welds without filler metal (one made from each side), or resistively heated filler wire is fed into the metal pool of a laser conduction weld in one or more passes along each side of the confronting surfaces to be joined. Quality welds are made despite gaps of varying size up to about 0.125 inches between the parts to be joined.

Machine for welding roof membranes

Abstract: A device for welding portions of two overlapping roof membranes wherein a fastening means has been fastened to the lower of the two membranes and wherein there are portions of both overlapping membranes on both sides of the fastening means. The device includes a welding means which can apply welds to the membranes on both sides of the fastening means simultaneously. The welding means includes a nozzle having two outlets, with each outlet applying a heat sealing weld on one side of the fastening means. The device also includes a pair of weighted stitcher wheel assemblies which help to eliminate air pockets for underneath the roof membranes and to maintain the proper alignment of the overlapping membranes. The invention also includes a welding process using the above-mentioned device.

Method and apparatus for cutting and welding steel strips

Abstract: A method, for butt-welding steel strips using a laser beam are disclosed, in which opposite ends of preceding and succeeding steel strips fed continuously are cut and the cut end edges thus formed are welded by butt welding using a laser. The cutting and butting at the time of welding are effected with one edge of the preceding steel strips adjacent to the opposite ends of the succeeding steel strips aligned to be parallel with the center line of travel of the continuous processing line. When effecting the alignment, the preceding or succeeding steel strip is attracted by an electromagnetic chuck on a work table in the continuous processing line and is pulled by the chuck toward a reference block provided with an alignment edge parallel to the center line of travel of the processing line to bring the edge of the sheet into contact with the reference block. The alignment is done in this state.

Laser welding method

Abstract: A laser welding method and apparatus for welding stacked coated members in which voids in the welds are positively eliminated. A spacer is disposed between the two members to be welded. This provides a path for discharging gas formed by heating the coating material. The method and apparatus of the invention are useful for the laser welding of base members coated with metals having a lower melting point than the metal of the base, paints and oils. Preferably, the width of the gap is in a range of 0.1 mm to 0.5 mm.

Method and apparatus for measuring and controlling indentation in resistance welding

Abstract: Apparatus and accompanying methods for use therein for measuring and controlling weld indentation during resistance welding operations are disclosed. During a welding operation, the apparatus measures changes in a distance separating a reference point located on an electrode assembly and a region situated on the surface of the workpiece being welded wherein the region is not substantially indented by the electrode. Specifically, a distance measuring system first establishes the location of the surface relative to the electrode before any welding current is passed through the weld area. The indentation is repeatedly measured by detection of ultrasonic echoes from the surface of the material being welded. Such measurements are taken at frequent intervals during the current flow period during which the weld is being formed in order to determine on a continuous basis the indentation of the electrode into the surface. The welding power may be terminated when the measured indentation reaches the desired value. In order to obtain more precise control of the indentation, the rate at which indentation occurs can be measured and the welding power can be changed on a half cycle by half cycle basis to increase or decrease the indentation rate according to a desired indentation program.

Method and apparatus for continuous production of tubular bodies by means of laser longitudinal seam welding

Abstract: Method and apparatus for the continuous industrial production of tubular bodies in which coated or uncoated steel strip is formed to a slit tube and the opposite strip edges are longitudinally seam welded at high speed by a laser beam of high energy density under protective gas with or without supply of additive material, and after a preparation adapted to the narrow melt zone and bringing together of the strip edges a fusion welding with subsequent controlled cooling and upsetting is carried out which results in a seam geometry suitable for any further processing.

Upwelling in the liquid region surrounding the keyhole in penetration welding with a laser

Abstract: In penetration welding with a laser, the pressure in the keyhole is in excess at atmospheric pressure. A pressure gradient related to this is produced in the liquid region surrounding it, with the result that there is a flow parallel to the axis of the laser. The velocity of this flow is found as a function of the material constants, and the volume flow rate calculated. From this it is possible to construct an estimate of the elevation or depression of the surface of the weld. the shape of the surface cross section is discussed, and some deductions made about the pressure distribution in the liquid metal.

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.