Showing papers on "Spot welding published in 1996"

The aluminum spot weld

Abstract: Weld conditions which promote long tip life for aluminum spot welds are not necessarily associated with high weld quality in terms of freedom from defects such as porosity, cracks and expulsion. Schedules which produce good weld nuggets in terms of the peel test and long tip life may not produce a good response in terms of fatigue life. The fatigue life range is optimized by maximizing the weld nugget diameter, i.e., by employing a weld schedule which may lead to expulsion and weld porosity. Weld strength, in both peel and overlap shear configurations, was found to be linearly dependent upon weld diameter. In the peel test, the strength was also dependent upon the base metal thickness, in that for a given thickness, there is a critical diameter for the transition between weld fracture and nugget pull-out. For a given nugget diameter, if pull-out is observed then the strength is greater than if fracture occurs through the weld. In the shear test, the opposite response was observed, the strength for nugget pull-out being less than that for weld shear failure. Weld pull-out was found only for the thinnest base metal thickness tested and the shear load depended only upon the weldmore » diameter over the range of thicknesses tested. Maximum strength in an aluminum spot weld is obtained by maximizing the weld nugget diameter for that thickness of material.« less

Transport Phenomena During Resistance Spot Welding

Abstract: Unsteady, axisymmetric transport of mass, momentum, energy, species, and magnetic field intensity with a mushy-zone phase change in workpieces and temperature, and magnetic fields in electrodes during resistance spot welding, are systematically investigated. Electromagnetic force, joule heat, heat generation at the electrode–workpiece interface and faying surface between workpieces, different properties between phases, and geometries of electrodes are taken into account. The computed results show consistencies with observed nugget growth, electrical current, and temperature fields. The effects of the face radius and cone angle of the electrode, parameters governing welding current, electrical contact resistance, magnetic Prandtl number, electrical conductivity ratio, and workpiece thickness on transport phenomena are clearly provided.

Developments in characterization of resistance spot welding of aluminum

Abstract: Automotive industry interest in aluminum is growing rapidly in Europe and North America. Resistance spot welding and weldbonding will be key techniques in the volume production of aluminum vehicles. A monitoring system has been developed to collect process data during single-phase alternating current (AC) and medium-frequency direct current (MFDC) inverter resistance welding. Features extracted from the captured data are used to characterize spot welding and to identify a range of process phenomena. Statistical analysis has been applied to investigate the relationship between the extracted features and the conventional physical parameters, e.g., weld size and static tensile strength. Welding trials using both MFDC and AC welding equipment have been carried out using aluminum of different gauges and surface conditions. Results on the Al-Mg alloy AA-5754 have shown that the monitoring methods developed previously for steel do not appear to be generally applicable to aluminum. No single parameter can accurately quantify weld quality. Multiple regression methods can, however, provide good prediction of nugget diameter and static strength. This has proved effective even when only electrical variables are logged, removing the need for measurement of other process signals, e.g., electrode displacement or force.

Contact resistances in spot welding

Abstract: The contact resistance of several aluminum alloys with different surface conditions was measured as a function of the applied current and under different applied loads. The magnitude of the contact resistance varied over a wide range of values, depending upon load and surface condition. Usually the contact resistance decreased with an increase in load, but if a surface lubricant was present, an increase in resistance was observed. Extensive plastic deformation occurred under the loading conditions imposed by the electrode tips. A cup and cone profile was found at the contact region of the faying surface after unloading. Under slowly varying currents, ∼1 Ms, electrical breakdown effects were observed when the potential across the surfaces was ∼0.2 V. The nature of the change was ascribed to metallic conduction and local fusion rather than oxide film breakdown. Under rapidly varying currents, ∼10 7 A/s, typical of a spot welding operation, the contact resistance was found to decrease to ∼20 pΩ within the first quarter cycle of weld current, irrespective of the initial surface condition of the aluminum alloy. Continued weld current inputs caused a further decrease in the contact resistance to ∼10 pΩ. It is concluded that the results of contact resistance tests may be influenced by the test procedure if large currents are used that develop a significant potential difference, >0.2 V, across the interface.

アルミクラッド鋼インサート抵抗溶接法の検討 鋼/アルミニウムの異材接合に関する研究(第1報)

Abstract: The dissimilar spot welding of aluminum and steel sheet with insert of aluminum clad steel sheet was investigated. The study was conducted considering the application to the fabrication of automobile body, which effective to decrease its weight. To clarify the properties of intermetallic compounds to be formed at the steel and aluminum bonding interface, the mechanical properties were measured using the balks of four kinds of intermetallic compound in Fe-Al binary system. The mechanical properties of spot welded joint of aluminum and steel sheet with or without insert of aluminum clad steel sheet were measured using cross tension test and the microstructure of welded joint by this process were observed.The intermetallic compounds of FeAl and Fe3Al had comparatively higher ductility and the Fe2Al5 and FeAl3 had high hardness and low ductility, so that the Fe2Al5 intermetallic compound were formed at spot welded zone of the aluminum and steel resulting in the deterioration of strength. The dissimilar metal spot welded joint by using insert of aluminum clad steel sheet had excellent tensile strength in cross tension test and fractured in the base metal of aluminum alloy. Two nuggets of aluminum to aluminum and steel to steel were obtained independently by this process. These two nuggets and clad interface by hot rolling contributed to keeping the joint strength. It was confirmed the dissimilar welded joint of aluminum and steel having the strength equal to that of similar welded of aluminum alloy were obtained using this process.

Further Refinement of a Methodology for Fatigue Life Estimation in Resistance Spot Weld Connections

Abstract: The overall objective of this research is to develop a general model of fatigue crack propagation in resistance spot-welded joints. An important feature of this development is that the model and accompanying methodology should be accessible to designers evaluating fatigue response of structures containing multiple welds. This objective is achieved by examining the stress state around a resistance spot weld. A general expression for the structural stress around the weld is formulated that is dependent only on the loading immediately surrounding the weld; as such, it is specimen independent. In previous work [1] it was found that structural stress could be successfully used to estimate life for crack initiation and growth to a length of 0.01 in. (0.254 mm) in resistance spot welds, and that this period represents less than 30% of the total life in as-welded joints. It is important to note that estimation of this period is highly dependent on fatigue-related material properties. In Ref 2 it was shown that structural stress can be related to crack propagation life through linear elastic fracture mechanics. Using the resulting relationship between structural stress and life, life estimations were made for a variety of HSLA steel specimens (e.g., tensile-shear, coach peel) in a number of conditions (e.g., as-welded, prestressed) and were compared with experimentally measured lives. Life estimations were within a factor of 3 of measured lives. In the current work, the methodology developed in Ref 2 for estimating propagation life is extended by explicitly considering the effects of axial loading and of load ratio on life estimates. In addition, issues related to creating an appropriate finite element model are addressed, and a number of modeling guidelines are established. Total life estimations are made and compare favorably with experimentally measured lives of welds in mild steels in a variety of specimen configurations.

A theoretical study on electrical and thermal response in resistance spot welding

Abstract: The effect of contact resistance including constriction and contamination resistance has been a major hurdle for the thermoelectrical analysis of the resistance spot welding process. In this paper, a simple model was suggested and used for calculating the electrical and thermal response of the resistance spot welding process to investigate the influence of contacting forces on the formation of weld nuggets. The electrode surface of the contact interface was assumed to be axisymmetric and its microasperities to have a trapezoidal cross-section. These microasperities were considered as the one-dimensional contact resistance elements in the finite element formulation. The contamination film was assumed to be a nonconducting oxide layer, which is very brittle, so that it is broken to some number of pieces when a contacting pressure is being applied. The crushed films were assumed to be distributed at regular intervals and to conserve their size and number during the welding process. The simulation results revealed that the proposed model can be successfully used to predict the effect of the contact resistance on the electrical and thermal response of the resistance spot welding process.

An Experimental Study of Resistance Spot Welding in 1 mm Thick Sheet of Low Carbon Steel

Abstract: Investigations on the influence of welding parameters such as welding current, electrode force and weld time in resistance spot welding processes have been carried out with the help of a specially developed simulator. The effect of these parameters on dynamic contact resistance as well as on the quality of weld joint in terms of weld joint strength, nugget diameter, etc., was studied and conclusions have been made. Experiments have been carried out on 1 mm thick St1203 (DIN 1623) type of steel. Experimental observations were analysed statistically to obtain an empirical relationship between weld strength and the welding process parameters and subsequently a polynomial relation of second order has been fitted with a satisfactory degree of reliability. From these results welding lobes were also drawn which will provide information on different conditions needed for specified weld strength and also ensure a minimum guaranteed strength at those combinations. The possibility of using dynamic contact resistance...

Theory of forces and stresses in spot welded overlap joints

Abstract: The complete equations describing simple relations between forces and stresses at the weld spot of overlap joints are presented, and applied to specimens used in industry as an example. The equations are also modified in respect to a measuring method for determining the weld spot forces. The essential components of the theoretical description are: an orthogonal reference system at the weld spot positioned according to the principal loading direction, the decomposition of the weld spot forces into joint face forces and «eigenforces», the weld spot modelled as a rigid core for evaluating the stresses connected with the joint face forces, and a homogeneous distribution of the stresses resulting from the «eigenforces». The assumptions and possible complications of the method under engineering aspects and the details of the rigid core model are described in separate publications.

Role of sulfur and processing variables on the temporal evolution of weld pool geometry during multikilowatt laser beam welding of steels : The beneficial effects of sulfur on weld pool size and shape are strongly dependent on controlling convective heat transfer

Abstract: Temporal evolution of weld pool geometry during multikilowatt conduction mode laser spot welding of steels is examined by conducting over eighty carefully planned experiments and concomitant analysis of the data by numerical simulation of heat transfer and fluid flow. The variables investigated are the concentration of sulfur in steel, laser power, power density and irradiation time. The results show that the mere presence of sulfur is not a guarantee of high weld metal aspect ratio. To achieve a beneficial aspect ratio in steels containing sulfur, processing variables must be controlled carefully so that convective heat transfer in the weld pool is important. Only when convective heat transfer is important, i.e., at high Peclet numbers, concentration of sulfur affects both the temporal evolution and the final shape and size of the weld pool. At a given laser power and concentration of sulfur, power density is an important factor in controlling the temporal evolution of weld pool geometry. In the first few seconds of laser-material interaction, the temperature profiles, fluid flow, and the shape and size of the weld pool change significantly. Heating of the workpiece continues with time much after the weld pool geometry is essentially fully developed. Our current understanding of heat transfer and fluid flow in welding can serve as a basis for improved understanding of the temporal evolution of weld metal shape and size for high-power conduction-mode welding of steels with different sulfur contents.

Method and apparatus for electrical resistance spot welding

Abstract: An improved welding apparatus and method of use including a pair of opposed electrodes mounted on arms which are fixed against outward displacement during the application of the welding current. One of the arms includes a cylinder for moving an electrode to and away from the work piece. The cylinder includes a pilot operated check valve which permits a one-way flow of hydraulic fluid while the weld current is applied. The check valve prevents movement of the electrode away from the work piece during expansion of the weld nugget, however, permits inward movement of the electrode after the nugget is softened.

Temporal pulse shaping and solidification cracking in laser welded Al-Cu alloys

Abstract: Solidification cracking in pulsed laser welds is a result of complex interactions between the alloy composition, the welding process conditions and the resulting solidification process, and the thermomechanical strains that are generated during welding. In pulsed laser welding, temporal shaping of the laser beam pulse has been reported to reduce or eliminate solidification cracking; however, a fundamental understanding of the influence of the temporal pulse shape on the cracking event has yet to be established. In this study, the cracking sensitivity of overlapped Nd:YAG laser spot welds was determined for binary aluminum-copper alloys. A pulse shape was then developed which reduced cracking in individual spot welds in Al-3.73 wt.% Cu. Using a numerical model, the thermal conditions during welding were predicted and were shown to be significantly different for two different pulse shapes. The resulting microstructures of the welds were examined and the primary dendrite spacing was shown to be in good agreement with the numerical predictions. Overlapped welds made using the temporally-shaped pulses also exhibited significantly less cracking. The results show that temporal pulse shaping can be effective for reducing cracks in both individual and overlapping spot welds.

Manufacturing method for automotive frame

Abstract: An automotive frame is assembled by joining fins of extrusions formed of aluminum alloy by resistance spot welding. The fins are formed integrally with each extrusion by extrusion. Alternatively, the extrusions may be joined together through a node part having fins. In this case, the fins of each extrusion are joined by resistance spot welding to the fins of the node part. The node part includes a body formed by extrusion and a side plate penetration-welded to the body by laser welding. The side plate functions as the fins of the node part.

Spot welding of aluminium and steel sheet with an insert of aluminium clad steel sheet: Dissimilar metal joining of aluminium and steel sheet (1st Report)

Abstract: Summary This paper describes an investigation of the dissimilar metal spot welding of aluminium and steel sheet with an aluminium clad steel sheet insert. The study relates to application of this system in automotive fabrication in an effort to reduce motor vehicle weight. To ascertain the mechanical properties of the intermetallic compounds formed at the steel and aluminium bond interface, measurements were performed using four types of Fe‐Al binary system intermetallic compound. The mechanical properties of spot‐welded joints in aluminium and steel sheet with and without insertion of an aluminium clad steel sheet were measured by the cross tension test, and the microstructures of the welded joints then formed were observed. The intermetallic compounds FeAl and Fe3Al have a relatively high ductility, and Fe2Al5 and FeAl3 have a high hardness and low ductility. Fe2Al5 intermetallic compounds were formed in the spot‐welded zones of the aluminium and steel sheet, resulting in loss of strength. The dissimila...

Motor-driven X-type resistance spot welding gun

Abstract: A motor-driven X-type resistance spot welding gun. A servo-controlled motor torque is converted into force to drive gun arms and into electrode force by using a reduction gear without converting rotational output of the motor into rectilinear motion. The two arms are respectively attached to an output shaft of the reduction gear or a case, and the rotational output of the motor can be converted into swing-wise movement to close and open the arms. The electrode tips on the arms nip a workpiece to apply electrode force to the workpiece, and current is passed through the workpiece to perform spot welding. A motor, a reduction gear and the like are assembled on a common base to form a driving unit so that an arm actuator for the X-type resistance spot welding gun is formed. The same driving unit can be used commonly to various X-type gun models. The independent properties of functions of a bracket for attaching the welding gun to a robot are improved. Since properties of the arm actuator and the bracket are not dependent on a welding unit of the gun (portion through which welding current flows), the production cost for a manufacturer and maintenance cost for a user are reduced.

Combined ultrasonic and resistance pressure welding

Abstract: In a process for improving weld characteristics and quality in resistance pressure welding, e.g. spot welding and roller seam welding, the joint area to be welded is subjected to ultrasound. An arrangement for carrying out the method comprises using one of the electrodes (7) at the same time as sonotrode. .

Optimum position controlling method of spot welding electrode

Abstract: PROBLEM TO BE SOLVED: To provide an optimum electrode position controlling method capable of preventing occurrence of the spatter by controlling the position of a welding gun in the welding electrode pressing direction to the position where the desired quality is obtained. SOLUTION: A welding gun 12 to which a lower welding electrode 10L is fixed, and a servo motor to vertically drive an upper welding electrode 10U are mounted on a robot arm 16. An encoder is installed on the servo motor, and the present position signal of the upper electrode 10U is monitored and inputted to a control part 18, and the pressure force of the electrodes 10U, 10L is inputted in the control part 18. The control part 18 makes a control by the command from the servo motor so that the position X of the electrode 10U is the commanded value. Because a weld zone generates a nugget through thermal expansion during energization, the pressure can be reduced when the weld zone is contracted. Forced insertion of the electrode by the excessive pressure when the nugget grows is eliminated, and generation of the spatter can be suppressed. COPYRIGHT: (C)1998,JPO

Battery interconnecting structure

Abstract: PROBLEM TO BE SOLVED: To offer battery interconnecting structure in which a plurality of unit cells are connected together so as to form a storage battery module of a required output voltage. SOLUTION: The plane part 5 of a connection piece 1 is welded to a metal electrode 10 of each unit cell A by means of projection welding, and the cylindrical part 4 of the connection piece 1 is welded to the metal armor 11 of the unit cell B. Projections 2 and 3 for projection welding are formed on the same radius which may take a plurality of values, so that the path of the inter-connection current becomes minimum, which allows adoption of a material having a large thickness or small resistivity to the connection piece 1, so that it is practicable to achieve both a connection with less electric resistance and a coupling of high mechanical strength.

アルミクラッド鋼と鋼およびアルミニウムとのスポット溶接-インサート材を用いた鋼とアルミニウムの異種金属接合(第1報)-

Abstract: This paper deals with the resistance spot weldability of an aluminum clad steel sheet to a steel or an aluminum sheet, and the dissimilar metal joining of a steel to an aluminum sheet with an aluminum clad sheet as an intermediate layer. The clad sheet was produced by hot rolling of steel and aluminum sheets with a direct resistance heating process. The mechanical properties of the clad sheet were between those of the steel and the aluminum sheet, and the peel strength was satisfactorily high.Materials used in spot welding were a 0.8 mm-thick EDDQ steel sheet, a 1.0 mm-thick aluminum-magnesium alloy sheet and the 0.8 mm-thick clad sheet which has a thickness ratio of aluminum/steel 1.1. The spot welding of the steel sheet to the steel side of the clad sheet and the aluminum sheet to the aluminum side of the clad sheet were successful. The spot welding of the steel sheet to the aluminum sheet by using the clad sheet as intermediate layer was also successful. However, thin intermetallic compound layer was formed at the steel/aluminum interface of the clad sheet due to the spot welding thermal cycle. The suitable welding current ranged between the values suitable for steel to steel and for aluminum to aluminum.The tensile shear strength and the U-tension strength of steel-clad-aluminum joints were higher than those of steel-aluminum direct joints and close to those of aluminum-aluminum joints. These results from mechanical tests suggest that the existence of intermetallic compound layers at steel/aluminum interfaces of the clad sheets were not detrimental to the strength of the steel-clad-aluminum joints. The fracture mode of these joints varied with the welding current.

Method and apparatus for determining an evaluation time interval and method and apparatus for assessing the quality of a spot weld based on a variation in temperature in the evaluation time interval

Abstract: A method and an apparatus for ascertaining an evaluation time interval for assessing the quality of a spot weld based on a course of a temperature at the weld, call for a course of a variable which is unequivocally associated with the temperature to be ascertained for a multiplicity of reference spot welds of differing quality, and for the courses of the variable to be compared with each other. A time interval which is determined from the comparison of the courses is used as the evaluation time interval, and the courses are significantly different from each other and have a sequence which corresponds to a sequence of the qualities of the associated reference spot welds. An allocation of the quality of any spot weld can be carried out simply and precisely by using values of the temperature-dependent variable within the evaluation time interval.

インサート材を用いた鋼とアルミニウムの異種金属接合 （第１報） アルミクラッド鋼と鋼およびアルミニウムとのスポット溶接:インサート材を用いた鋼とアルミニウムの異種金属接合(第1報)

Abstract: This paper deals with the resistance spot weldability of an aluminum clad steel sheet to a steel or an aluminum sheet, and the dissimilar metal joining of a steel to an aluminum sheet with an aluminum clad sheet as an intermediate layer. The clad sheet was produced by hot rolling of steel and aluminum sheets with a direct resistance heating process. The mechanical properties of the clad sheet were between those of the steel and the aluminum sheet, and the peel strength was satisfactorily high.Materials used in spot welding were a 0.8 mm-thick EDDQ steel sheet, a 1.0 mm-thick aluminum-magnesium alloy sheet and the 0.8 mm-thick clad sheet which has a thickness ratio of aluminum/steel 1.1. The spot welding of the steel sheet to the steel side of the clad sheet and the aluminum sheet to the aluminum side of the clad sheet were successful. The spot welding of the steel sheet to the aluminum sheet by using the clad sheet as intermediate layer was also successful. However, thin intermetallic compound layer was formed at the steel/aluminum interface of the clad sheet due to the spot welding thermal cycle. The suitable welding current ranged between the values suitable for steel to steel and for aluminum to aluminum.The tensile shear strength and the U-tension strength of steel-clad-aluminum joints were higher than those of steel-aluminum direct joints and close to those of aluminum-aluminum joints. These results from mechanical tests suggest that the existence of intermetallic compound layers at steel/aluminum interfaces of the clad sheets were not detrimental to the strength of the steel-clad-aluminum joints. The fracture mode of these joints varied with the welding current.

Effect of number of welds in spot welded and weldbonded arrays on static failure load of individual spot welds and adhesive bond

Abstract: A comparison of the strengths of spot welded and weldbonded arrays has been made for up to 15 welds in the array. In a spot welded array, the joint strength is linearly related to the number of welds in the array. For weldbonded arrays, the overall joint strength depends on the number of welds in the array and the adhesive modulus. With less than five welds in the array and using a high modulus adhesive, the joint strength is constant and equals the strength of the adhesive component. At a larger number of welds, the joint strength is a function of the weld strength. Similar trends were observed with a low modulus adhesive. In this case, there was evidence to suggest that the strength of the adhesive was enhanced in the presence of spot welds.

Ocular hazards of industrial spot welding.

Abstract: Any welding process is perceived to be a radiation hazard to the eye. Site visits were made to an automotive assembly plant to assess the levels of optical radiation and other hazards on the production line. Measurements were taken with a scanning spectro-radiometer and optical power and energy meters at operating working distances at spot welding stations where nonrobotic procedures were performed. Ultraviolet (UV) irradiance levels produced while spot welding with electrodes operating at 10 to 15 kA and 10 to 20 V were several orders of magnitude below recommended safety limits for industrial exposure. Flashes were rich in visible light and infrared (IR) radiation, but not at hazardous levels. The principal hazards in manual spot welding with high-current electrodes are high-speed droplets of molten metal produced by the process. These are easily defended against by wraparound polycarbonate eye shields. Language: en

Impact welding of foils by water jets

Abstract: Impact welding is a practical and economically feasible process for the solid-phase welding of similar and dissimilar metals. The versatile process is applicable to combinations of materials usually considered incompatible using more conventional joining methods. Thus, unlike with other spot welding methods, it is possible to use impact spot welding to join two metals of widely different melting points. Considerable research is needed to gain a thorough understanding of this process, its potential and possible new applications. Impact spot welding is similar to the familiar explosive welding process. Impact spot welding can be brought about by the action of a high-velocity object, such as projectile, on the material comprising the impacting object-target interface. The projectile impinging onto the top surface of a flyer plate at the target provides the energy of collision. Subsequently, the flyer plate moves with the projectile toward the base plate. A second impact occurs between the center of the bulge of the flyer plate and the base plate. The central collision of impact spreads radially out with an angle of collision. This oblique collision is an important feature of this process. The manner in which the flyer plate deforms due to the impact of a high-speedmore » object is significant in defining spot welding geometry. The deformation is produced by a combination of elastic, plastic and hydrodynamic wave propagation involving normal, bending and shear stresses. Metallic materials are forcibly driven together by the use of an impactor in such a way that a strong metallurgical bond is formed. Therefore, the use of either explosives or impactors, which may be water jets or solid projectiles, is incidental. Bonding results, in general, only from the impact of the two or more materials. In this sense the resulting bonding may be called impact bonding instead of explosive bonding.« less

Indirect type resistance spot welding device

Abstract: PURPOSE: To reduce the strain and the deformation of a work after welding by pressing the work with a guide before bringing an electrode into contact with the work. CONSTITUTION: A resistance spot welding device is constituted with an electrode 4 fitted to a pressurizing device 5, a cylindrical guide 1 arranged at the outer periphery of the electrode, a coil spring 3 hanging down the guide 1 to the pressurizing device 5 and a rubber ring 2 arranged at the lower end of the guide 1. By this constitution, at the time of descending the electrode 4, etc., with the pressurizing device 5 to the work 7 laid on a jig 6, firstly, the rubber 2 is brought into contact with the work 7, and the work 7 is widely held. Successively, at the time of exceeding the elastic load of the rubber 2 and the coil spring 3, the electrode 4 is brought into contact with the work 7 to hold the work 7. In this condition, the resistant spot welding is executed and at this time, it is prevented that the rubber 2 is melted.