Showing papers on "Spot welding published in 1991"

Analysis and development of a real-time control methodology in resistance spot welding

Abstract: The single-parameter, inprocess monitor and automatic control systems for the resistance spot welding process have been studied by many investigators. Some of these have already been commercialized and used by sheet metal fabricators. These control systems operate primarily on one of the three process parameters: maximum voltage or voltage drop, dynamic resistance, or thermal expansion between electrodes during nugget formation. Control systems based on voltage or dynamic resistance have been successfully implemented for industrial appl ications. A great amount of experience on these two control methods has been accumulated through trial-and-error approaches. The expansion-based control system is not commonly utilized due to lack of experience and understanding of the process. Since the expansion displacement between electrodes during welding responds directly to the weld nugget formation, this control parameter provides a better means to produce more precise spot welds. However, the control algorithm of this method is more complex than that for the other two methods. Fruitful development of such a system cannot be obtained by trial-and-error approaches. This paper presents a systematic approach to develop the expansion-based control algorithm for resistance spot welding. The finite element method was used to simulate the welding process and to determine the physical response of C. L. TSAI, W. L. DAI and D. W. DICKINSON are with the Department of Welding Engineering and J. C. PAPRITAN is with the Department of Agricultural Engineering, The Ohio State University, Columbus, Ohio. the joint material to the various welding conditions. Direct correlations between nugget formation and expansion displacement between electrodes were obtained. By systematic computer simulations, the weldability characteristic curves for resistance spot welding were developed. These weldabi l i ty curves show inadequate welding conditions that would cause nugget expulsion and current shunting. A welding duration curve, which shows appropriate time for squeeze, weld and hold cycles, was developed and used as a basis for in-process resistance spot welding control.

Fracture mechanics analysis of fatigue resistance of spot welded coach‐peel joints

Abstract: Resistance spot welding is the most widely used joining method in automobile manufacture. The number, location, and quality of welds are some of the factors that influence the performance of welded subassemblies, and body panel structures. Therefore, design optimization requires knowledge of not only sheet metal behavior, but also weld behavior under service loadings. A linear elastic fracture mechanics approach was employed in this study to estimate the fatigue lives of spot welds subjected to tearing loads in a coach-peel specimen. Using a finite element method (FEM), the initial J-integral values for five coach-peel joints, each with different geometries, were calculated. Fatigue tests conducted on the same weld geometries provided life data. The experimental data were used to derive a relationship between the initial elastic J-integral values (ΔJe) and the fatigue life. It was found that the total fatigue life (Nf) of a weld at one applied stress range is related to its range of J-integral value such that a ΔJe vs Nf log-log plot gives a straight line relationship. This relationship can be used to evaluate the effects of geometrical variables on the fatigue life of coach-peel joints. The results show that, within the dimension range studied here, the effects of geometrical variables on the fatigue resistance can be ranked in the following decreasing order: weld eccentricity, sheet thickness and weld nugget diameter.

Factors Affecting Nugget Growth With Mushy-Zone Phase Change During Resistance Spot Welding

Abstract: An unsteady, axisymmetric model is first proposed to investigate extensively effects of the physical, thermal, and metallurgical properties and welding conditions on nugget growths with mushy-zone phase change during resistance spot welding. The electromagnetic force, joule heat and interfacial heat generation, and cooling effects of electrodes are taken into account. Fluid patterns, temperature fields, and solute distributions in the liquid, solid, and mushy zones are determined. Results show that the computed nugget growths and temperature fields are consistent with experimental data. Variations of properties strongly affect the nugget growth. The maximum velocity in the weld nugget is found to be small and around 5 mm/s.

Method for checking a spot welded portion and spot welding machine

Abstract: A decrease amount in plate thickness at a spot weld is detected at a predetermined time period when application of pressure is still maintained after termination of power supply to electrodes for spot welding. The decrease amount is correlated with the magnitude of diameter of nugget formed by spot welding, e.g., a larger diameter of nugget signifies a stronger the joint, and therefore, the quality of joint at the spot weld can be examined on the basis of the detected decrease amount. Since a value obtained by integrating plate thickness detection data of the spot weld during the predetermined time period is correlated, as the decrease amount is, with the magnitude of the diameter of a nugget, the quality of the joint may also be examined on the basis of this integrated value. There is provided, in a spot welding machine, a detector for detecting a stroke position of a cylinder for pressing electrodes or a detector for detecting a position of displacement of a tip portion of an arm interlocked with the movement of the electrodes and the distance between the electrodes, i.e., plate thickness, can be indirectly detected by the detector without adversely affecting efficiency of the spot welding work.

Method for resistance welding steel and aluminum material

Abstract: PURPOSE: To form the part to be welded with enough welding strength between the steel material and aluminum base material without dropping the productivity and to make the use of the general purpose alternative current spot welding machine possible by coating on the surface of the welded steel material. CONSTITUTION: In the case for welding the steel material and the aluminum material, the metal or alloy having the melting point under the melting point of the aluminum material is coated by the thickness 2-20μm on the surface of the steel material to be made in contact with the aluminum material, then the steel material and the aluminum material are resistance-welded. As the coating material, Al, Al-Zn, AL-Si, Zn, etc., are used. The coating layer is melted at the welding time, the minute projecting and recessing parts are formed on the joining boundary face, because the steel material and the aluminum material are joined through this joining boundary face, the joining strength is improved. COPYRIGHT: (C)1992,JPO&Japio

Joining method for steel material and aluminum-base material

Abstract: PURPOSE:To join the steel material to the aluminum-base material with high joint strength by the weldbonding method. CONSTITUTION:Aluminum or an aluminum alloy with 2-20mum thickness is applied on the joining face of steel material 10 which is one material to be joined and a hot setting adhesive 30 of an epoxy system, etc., is applied thereon. This steel material is superposed on aluminum-base material and spot-welded together and then, the steel material and the aluminum-base material are integrated into one body by hardening of the adhesive 30. Accordingly, since a hard and rugged alloy layer is formed on a spot weld zone, welding strength is increased and a joint having resistance to stress added before the adhesive is hardened is obtained. In addition, adhesive strength itself is increased as compared with the case where Zn-base material is applied.

Weldability of intercritical annealed dual-phase steel with the resistance spot welding process

Abstract: Optimum welding parameters for producing maximum joint strength in dual-phase steel are established and the cause of weakening in the weldment is identified as tempering of martensite in the HAZ.

Spot resistance welding method and welding electrode for implementing the method

Abstract: The subject of the present invention is a method of spot resistance welding at least two metal pieces (1, 2). The method consists in pressing the pieces (1, 2) between two electrodes (3, 4), in determining the overall resistance between the electrodes (3, 4), and the contact resistances of each electrode (3, 4) with the piece (1, 2) with which it is in contact, in calculating the contact resistance between the said pieces by the difference between the overall resistance and the sum of the resistances of each piece and of the piece-electrode contact resistances, in determining the actual intensity of the electric welding current, and in adjusting the various welding parameters for the said pieces (1, 2) in order to maintain a constant optimal intensity of the electric welding current. The subject of the present invention is also a welding electrode for implementing the method.

Resistance spot welding method for steel sheet and aluminum alloy sheet

Abstract: PURPOSE: To provide a joined part having sufficient joining strength by arranging an anode electrode tip 3 and a cathode electrode tip 4 of a DC resistance spot welding machine on an aluminum alloy sheet and a steel sheet, respectively to perform spot welding. CONSTITUTION: The aluminum alloy sheet 2 and the steel sheet (mild steel sheet) 1 are superposed on each other, the anode electrode tip 3 and the cathode electrode tip 4 are abutted on the aluminum alloy sheet 2 side and the steel sheet 1 side, respectively and spot welding is performed under specified conditions by using the DC resistance spot welding machine. A nugget 5 is formed on the joined interface between the steel sheet 1 and the aluminum alloy sheet 2 on an cross section of a cut part of an obtained test piece. Consequently, the steel sheet and the aluminum alloy sheet are subjected to spot welding and the joined part having the sufficient joining strength can be formed. This welding method is useful in welding of the steel sheet and the aluminum alloy sheet required at the diversified manufacturing stages of automobiles. COPYRIGHT: (C)1993,JPO&Japio

Determining Weld Quality in Pulsed Nd:YAG Laser Spot Welds

Abstract: For pulsed Nd:YAG laser spot welding applications, the development of optimum welding procedures ought to include various measures of weld size and quality, such as weld diameter, depth, surface contour and porosity. A split‐specimen technique has been developed that, despite the small size of the welds, allows such measurements to be made faster and more accurately than the traditional metallurgical technique involving sectioning, polishing and etching. In the split‐specimen technique, spot welds are made along a carefully prepared butt joint, cooled in liquid nitrogen and then fractured rapidly by an impact load. The accuracy and precision of this technique, relative to sectioned welds, were examined using welds on austenitic stainless steel. The influence of the roughness of the butting joint surfaces on measured weld dimensions was determined. It was found that measurements could be made more easily and with less error using the split‐specimen technique, provided that the surface center‐line average (...

Method for the automated manufacture of wound electrical components by contacting thin insulated wires to terminal elements on the basis of laser welding

Abstract: In a method for automated manufacture of wound electrical components by contacting thin insulated wires to terminal elements on the basis of laser welding, only the terminal element is melted by direct laser irradiation to form a welding spot at the location provided for the welding. The wire is subsequently embedded into the welding spot as soon as the welding spot has cooled to such an extent that the wire subsequently only melts superficially. During the course of continuous winding of winding carriers, the insulated winding wire is wound into the welding spot produced on the respective terminal element, and is thereby pressed by the winding tension into the melt which solidifies to form the welded connection.

Spot welding inspecting apparatus

Abstract: The present invention relates to a spot welding inspecting apparatus for inspecting a weld between two metal plates which are subjected to spot welding without destroying the metal plates or weld. A pair of knife gauges having an interval therebetween larger than the diameter of the weld are inserted between the welded metal plates by a continuous impact of the hammer which is driven by a compressed air and pushed between the metal plates so as to clamp the weld. Thereafter, the piston is moved so that the knife gauges may approach the weld to indicate the distance between the knife gauges with the index.

Method and device for forming three-dimensional stereoscopic model

Abstract: PURPOSE:To form a three-dimensional stereoscopic model with an opaque wire from a graphic displayed on CAD, FAX, etc., thereby creating a sensation full of existing feel and volume. CONSTITUTION:A metal wire alpha is successively drawn out in tracing a nozzle 2 along the contours of the displayed graphic. After setting the wire for a required position for a three-dimensional construction with a holding jig 3, a voltage is applied between the holding jig 3 and the wire formation 6, which is built up from underside, by means of a welding power source 5, and the setting part is continuously built up by a spot welding. Thus, an object of the displayed graphic is formed by repeating this operation.

Production of alpha type titanium alloy sheet

Abstract: PURPOSE:To produce the alpha type titanium alloy sheet having a fine-grain structure of small anisotropy by cutting a hot rolled coil to a cut sheet shape, and back rolling the cut sheets at a specific heating temp. and draft in the direction orthogonal with the hot rolling direction with steel sheet as covering sheets. CONSTITUTION:The slab of the alpha type titanium alloy is heated and a hot rolled coil is produced by a continuous strip mill. The cut sheets are cut out of this coil and the sheets are subjected to surface polishing and pickling and thereafter, lime is applied thereon as a mold release agent and the slab for back rolling is assembled. This slab is formed by spot welding 3 of the covering sheets 2 consisting of a carbon steel on top and bottom of two sheets of the cut sheets 2 so as to cover these sheets. The cut sheets are back rolled at the heating temp. of >=800 deg.C and =40% and <=90% in the direction orthogonal with the hot rolling direction. The alpha type titanium alloy sheet having the fine-grain structure of the small anisotropy is obtd. in this way.

Spot-welding electrode

Abstract: The welding electrode is composed of an elongate body (7) and a tip (6), between which a spacer (8) is inserted. The spacer (8) is made of a metal or alloy whose electrical resistivity is lower than that of the metal or alloy of the body (7) and the tip (6). Rapid initial heating of the tip (6) is thus obtained, which makes it possible to weld, without any difficulty, metal sheets coated with a priming paint layer or a protective layer which has to be thermally destroyed at the points of welding.

Titanium nitride or carbonitride coated copper component - used esp. in resistance or arc welding or in electrical switches

Abstract: A copper-based component, with a titanium nitride or carbonitride coating, is new. The coating is pref. 1-10 (esp. 1.5-4) microns thick. Prods. of the component involves opt. plasma-assisted, PVD or CVD. USE/ADVANTAGE - The component may be a resistance spot, roller seam or projection welding electrode, a component (esp. shielding gas nozzle, electrode clamping sleeve or wire contact nozzle) of a TIG or MGA welding torch or a component of an electrical switch element.

Instrument for detecting consumed degree of electrode tip

Abstract: PURPOSE:To accurately decide consumed degree of an electrode tip, to execute grinding of the electrode tip with the optimum timing and to prevent deterioration of welding quality by radiating light on surface of the electrode tip in a resistance welding machine and measuring intensity of this reflected light. CONSTITUTION:On the surface of electrode tips 2a, 2b for welding in the resistance welding machine 1 of a spot welding machine, etc., the light is projected from projecting element X in a projecting device 3 and this reflected light is received with photodetector Y in a light receiving device 4 and signal level of this reflected light is compared with the preset prescribed threshold value in a deciding device 20 to accurately decide the consumed degree on the surface of electrode tip. By this decision, the deterioration of welded quality caused by excess wearing of the electrode tip 2a, 2b or shortening of the service life by grinding the electrode tip at early time under condition, which can be yet sufficiently used, with a dresser is prevented.

Robotic welding system with parallel degrees of freedom

Abstract: This paper considers some problems concerning robotic welding of large structures. If spot welding is applied, then the task consists of fast motions between welding points, and at each point the end effector stops and maintains position for a short time. Similar examples can be found in arc welding applications. Since large structures and, accordingly, large robots are considered, a significant problem appears when extremely nonuniform motion is required. One way to solve this problem is to introduce parallel degrees of freedom. Two methods for this distribution of motion to parallel degrees of freedom are discussed. The theory resulted in the design of a large portal robot with high dynamic capabilities.

Spot welding inspection device

Abstract: PURPOSE:To improve the detection accuracy of the diameter of a nugget by deciding the diameter of the nugget from the ratio of a potential difference across spot welding and a reference potential difference nearby the spot welding. CONSTITUTION:Electric feed terminals 1 and 1a are arranged at both ends of a measuring head 3 and three potential difference measurement terminals 2, 2a, and 2b are provided between the terminals 1 and 1a to measure potential differences V and V0 at two positions. A current is supplied to the terminals 1 and 1a from a DC current source 4. A current polarity converting device 5 is provided to switch the polarity of the DC current. Potential difference of the terminals 2, 2a, and 2b are switched through a multiplexer 9 and measured by a fine potential different meter 8. The measured potential differences are transferred to a computer 6. The computer 6 decides the nugget diameter of the spot welding from the potential difference distribution. At this time, the potential difference between the terminals 2 and 2a is regarded as the reference potential difference V0 and the nugget diameter is decided from the ratio V/V0 of the potential difference V between the terminals 2a and 2b to the potential difference V0.

Spot welding tongs

Abstract: An articulated pair of spot welding tongs comprising two supports (1,2) of the male and female type, each having a fork joint and an orifice, and two interchangeable arms (3,5), each carried by one of the supports. Each support is made from aluminum and treated by hard anodizing. A pin (13) traverses the two orifices, and carries two plates (39,40), each plate comprising a metal support plate covered by a coating based on fluorocarbonated fibers. The welding tongs can be used for a long period of time without any need for changing the insulating elements.

Device for teaching robot for spot welding

Abstract: PURPOSE:To easily and accurately teach a spot position and a spot angle of spot welding to a robot by detecting optically an angle of an electrode chip with respect to materials to be welded by using a beam sensor CONSTITUTION:The robot 1 is operated manually and the tip of the beam sensor 7 is brought close to a master member for the spot position Beam light is projected on the surface of the master member from a light emitting member 8 provided on the beam sensor 7 and reflected light is received by a light receiving member 9 and converted into an electrical signal which is sent to a detection unit 13 This signal is amplified by an amplifier 15 and an angle for the surface of the master member of a shank 6 is determined by this signal When a converted angle is 0 - 2 deg, it is determined as correct straightness and a lamp 17 is lit up and a buzzer 18 sounds to inform a teacher 24 The robot 1 stores the spot position and the spot angle by a welding chip to be fitted to a chip holder 4 by switching a teaching button 25 of the teacher 24 ON This step is repeated until the next spot position

Manufacture of spot welding electrode tip

Abstract: PURPOSE: To provide a simple manufacturing method obtaining uniform material quality of a spot welding electrode tip of automobile parts and electronic parts as a main purpose according to this invention. CONSTITUTION: In the spot welding electrode tip to spot-weld materials to be welded by spot welding, the master particle surface of Cu is formed into a specified shape by using capsule powder formed by covering it by slave particles of W, Cr, Be, Zr, Al 2 O 3 or ceramic particles, etc., and micro-capsuling it and then, solidifying this by plasmasintering, according to this invention. COPYRIGHT: (C)1992,JPO&Japio

Manufacture of press product

Abstract: PURPOSE:To prevent the generation of a crack and to improve accuracy of press-forming by forming projectingly tongue-like parts on each end of panel members superposed on each other and spot-welding the tongue-like parts to carry out press-forming thereon. CONSTITUTION:The tongue-like parts 5 are formed projectingly on each end 4 of the panel members 3A and 3B superposed on each other and the tongue-like parts 5 are joined together by spot welding and then, press-formed. Consequently, the stress generated due to bending is diffused and absorbed by extensions of the tongue-like parts 5 and the crack is prevented from being generated on a heat-affected zone, etc. In addition, malleability to the same extent as raw material can be obtained on a joined part by spot welding by extensions of the tongue-like parts 5 and accuracy of press-forming is improved.

Laser beam welding machine

Abstract: PURPOSE:To improve optical axis adjusting accuracy at the time of welding by providing a rotary table to mount a laser beam splitting part, fiber optical parts and laser beam emitting optical parts at the positions in opposition. CONSTITUTION:The laser beam welding machine is provided with the rotary table part 9 which mounts the laser beam splitting part 2 to split a laser beam, the fiber optical parts 3a and 3b to lead the laser beam to machining points in opposition on workpieces 5a and 5b and the laser beam emitting optical parts 4a and 4b and rotates around the workpieces 5a and 5b. An optical axis of the workpieces 5a and 5b held by collect chucks 6a and 6b is adjusted by a Z stage and an X-Y stage 8. The laser beam is split equally and emitted from the laser beam emitting optical parts to the machining points. The laser beam emitting optical parts move to the optional positions around the workpieces by the rotary table 9 while maintaining the positions in opposition mutually to perform spot welding. After spot welding, the laser beam emitting optical parts make a half-round around the workpieces to perform seam welding. By this method, thermal strain is offset and optical axis adjusting accuracy can be improved.

Spot welding equipment

Abstract: PURPOSE:To reduce the cost of the spot welding equipment and to simplify its constitution by operating selectively plural spot welding guns by using a common control means CONSTITUTION:Pressurizing cylinders 12 of the spot welding guns 10A and 10B are connected with a pressure source 40 via solenoid valves 30A and 30B Primary winding l1 of a transformer 50A is connected with a power source 70 via a switch circuit 60 and primary winding l1 of a transformer 50B is connected in parallel with the primary wiring l1 of the transformer 50A In addition, secondary winding l2 of the transformers 50A and 50B are connected with electrode chips 11 and 11 of the welding guns 10A and 10B, respectively The switch circuit 60 is provided with two thyristors 61 and 62 whose gates are connected with a timer contactor 80 When a robot controller 90 then adds a valve driving signal and a valve selecting signal to the timer contactor, the two spot welding guns 10A and 10B operate selectively