Projection Welding Research Articles

Analysis of projection welding in relation to the non-parallelism of electrodes

The article contains the analysis of projection welding in relation to the non-parallel location (non-parallelism) of electrodes. For a thin-walled flat element, e.g., sheet metal with two embossed projections, calculations were conducted for different angles between the upper electrode and the lower electrode. The calculation involved the use of the SORPAS 3D software. The analysis included the distribution of temperature, power density, electrode displacement, the volume of molten metal in the weld nugget, nugget diameters, and energy supplied to the weld. The article presents the comparison of results obtained for various angles between the electrodes of the welding machine. The results of numerical calculations were verified experimentally through technological welding tests and destructive tests (peeling/metallographic). The convergence of the experimental and numerical results was satisfactory. The tests involved a typical element used in the automotive industry, i.e., a nut with two embossed projections in the flat part. The article represents quite an innovative new approach to multiple-projection welding from a numerical calculation point of view. Such an approach allows the researcher to identify the phenomena taking place in the process. The article also presents a new approach to the analysis of multi-projection welding as regards the non-parallelism of electrodes. The results enabled the determination of phenomena taking place in the multi-projection welding process as well as the boundary conditions in relation to which the process became improper (unstable).

Development of a Quality Control System Using Modal Analysis to Evaluate a Multi-Point Projection Welding Process.

The article presents the results of the development and research regarding the application of modal analysis to the evaluation of a multi-point projection welding process. The quality control system is based on the information provided by modal analysis for the entire welding station after the previously completed welding process. The research is carried out due to the lack of an effective method for assessing the course of the multi-spot projection welding process in the case of a single current circuit passing through many points at the same time. A study of the applicability of modal analysis in investigating the quality of a multipoint joint was conducted for four DIN 928 nuts welded to a steel profile. The aim of the study was to determine the influence of weld defects on the displacement of resonant frequencies. To realize the objective, the dynamic properties of the entire welding station, including the sample in the frequency domain, were investigated. In the first stage of the study, a finite element method was used to perform modal analysis and examine the form of vibrations for the individual natural frequencies of the welding fixture including the sample. Then, quality verification using the dynamic resistance method was performed, which was compared later with the modal approach. The last stage of the study was to conduct modal analysis in the frequency domain to verify the numerical studies.

Investigation on the Effect of Projection Types on Stud Weld Strength by Taguchi Method

In this study, the effect of different weld projections on the mechanical properties of stud welds was analyzed using the Taguchi experiment planning method, using a projection welding machine with a capacity of 100 kVA with MFDC transformer. The samples were subjected to the tensile rupture force test with a destructive test device. The aim of this study was to ensure product safety by capturing the spot-welding quality, which is determined by the specifications of the automotive main industry, using a bolt with a lower weight. In this study, 1.5 mm WSS-M1A365-A11 uncoated steel sheet and 8.8 quality M6x1.00x25 triple projection uncoated welding bolts and 8.8 quality M6x1.00x18.5 ring shaped weld bolts were used as stud welding bolts. Different welding times, different welding currents and different welding clamping forces were used on the WSS-M1A365-A11 steel sheet samples in the stud welding operation with bolts. Taguchi analysis showed that ring shaped stud weld bolts required welding parameters of 32 ms welding time, 27 kA welding current and 500 daN welding force, while triple projection stud welding was found to perform the best optimum weld with 23 ms welding time, 18 kA welding current and 350 daN force.

Numerical investigation of flash formation and asymmetrical cooling in resistance projection welding

In resistance projection welding, the softened material is squeezed out from the joint area. The two workpieces being joined together often have different geometries, leading to asymmetrical cooling. The flash formation and asymmetrical cooling are not well quantified in the literature. This study developed a coupled electrical-thermal-mechanical model with adaptive remeshing and glued contact activation techniques for projection welding of steel fitting to a steel shell. The model was used to calculate the evolution of temperature distribution in the fitting and shell for welds made under two different hold times. The cooling rates were then inputted into a literature model to predict the joint hardness values, which correlated well with the experimental data. Additionally, the main factors for the accurate prediction of flash shape and size were the use of temperature-activated glued contact and high-temperature flow stress. Specifically, a combination of no glued contact and low flow stress can lead to an overprediction of the flash geometry.

Non-destructive characterization of resistance projection welded joints by ultrasonic and passive magnetic flux density testing

The weld of resistance projection welded joints is not visible from outside. Therefore, visual evaluation is restricted, and visual inspection is not possible at all. So far, the parameters of the welding process are monitored and controlled. In addition, the welds are periodically tested destructively to determine the quality of the welds. No industrial standard has yet been established in the field of non-destructive testing (NDT) for projection welded joints. This study focuses on NDT of projection welds using two different ultrasonic imaging inspection systems and the passive magnetic ux density testing (pMFT) method. The ultrasonic inspection systems commercially available and established in the field of NDT of spot welds. Both systems are originally designed for the NDT of spot welds and not for projection welds. Unlike the ultrasonic systems, the pMFT is still in laboratory status. The method has originally been developed to evaluate spot welds and is also used in this study to evaluate projection welds. The applicability of the investigated systems to projection welding is investigated in order to derive mandatory development steps to achieve reliable results. The pMFT method shows also good results for NDT of spot welds In this contribution, the measurement and evaluation concept of the three NDT systems for projection welded joints is presented. The NDT results are discussed in the context of the corresponding destructive results in terms of tensile forces and fracture areas. Advises for further development of all investigated systems are given.

Optimised projection welding of steel Bars

The article presents tests aimed at optimising the welding of bars, made of steel AISI1005 (ø 4.2 mm), in a cruciform configuration (i.e. using the cross-wire welding process). The authors identified research gaps and carried out a detailed numerical analysis of these cases. The research-related calculations involved the use of SORPAS software. The new areas of research included (i) bars with protective zinc coatings having various thicknesses of 0 µm, 5 µm, 10 µm and 30 µm, (ii) various welding current rise times (up-slope) and (iii) single and multi-pulse welding cycles. The tests were carried out using a DC 1 kHz inverter welding machine; the results concerning welding up-slope times were compared with those obtainable using a conventional AC 50 Hz welding machine. The results of the study, in the form of a welding technology with various values of up-slope time, have been implemented in industry. The inventive idea is protected by patent no. P.229445 at the Polish Patent Office.

A new resistance insert spot welding method for injection-molded FRP–steel component

For weight reduction, multi-material designs comprising metal and fiber-reinforced plastic (FRP) components in vehicle body structures have been increasingly used. However, the commonly used resistance spot welding (RSW) technology for car body assembly cannot be employed to join sheet metal and FRPs, limiting the use of FRPs. To solve this problem, a novel resistance insert spot welding (RISW) technique was developed in this work for RSW of steel parts and FRP structure parts made by injection molding. Small inserts were developed by using finite element method and experiments that may be welded to different micro-alloyed and dual-phase sheet steels using the projection welding method. The usual flange width of original equipment manufacturers could be kept unchanged. Using the developed insert and welding parameters, the maximum temperature in the FRPs surrounding the inserts was limited to 255 °C, minimizing the damage to polyamide 6 (PA6) material (with 40 wt% glass fiber). A weldability range between 2.5 and 7 kA could be achieved. The joining strength of RISW between a micro-alloyed HC340 steel in 0.75 mm and 1.5 mm thickness and a 2.5 mm/3.0 mm PA6-GF40 material is 20 to 80% higher than self-piercing riveting (SPR). For high-speed loading, RISW strength increases by 39 to 56% further. Finally, RISW was successfully applied to an FRP–steel roof-frame sub-assembly that consists of 19 simultaneously integrated inserts, achieving 10% weight reduction.

Understanding the bonding mechanism in short-time resistance projection welding: a comprehensive analysis

Capacitor discharge welding (CDW) is characterized by a pulsed electrical current profile. It is primarily utilized for resistance projection welding tasks, offering high power densities and short welding times. According to the latest findings, the welding process can be divided into different phases: contacting, activating, material connection, and holding pressure. During the activation phase, high-speed video-imaging reveals the generation of metal vapor which effectively eliminates impurities and oxide layers from the contact zone. The result of this is an activated surface. The purpose of this paper is to describe the physical effects of the bonding mechanism during short-time resistance welding. The Chair of Joining Technology and Assembly at the Technische Universität Dresden has a laboratory facility that can interrupt the welding current at any desired time during capacitor discharge welding. This allows different welding current profiles with always the same current rise time to be scientifically investigated. The experimental findings were supplemented with simulative analyses to clarify the bonding mechanism in resistance projection welding. Three different surface conditions are considered to generalize the findings on the bonding mechanism. Temperature and current density distributions were assessed to provide a physical description of the activation phase. The power density in the joining zone at different interruption times is determined, which gives an indication of activation by metal vaporization. The material connection is determined experimentally for the same interruption times. The numerical simulation model can be used to describe the bonding mechanism in short-time resistance welding. In resistance welding, the bond is formed due to the molten phase (solidification structure). In short-time resistance welding, the bond is formed due to surface activation by metal vaporization.

Design, manufacturing and thermal analysis of a honeycomb-inspired PCM-filled cold plate

In recent times, electric vehicles (EVs) have been seen as an environment-friendly alternative to conventional vehicles. Lithium-ion battery packs power the EVs today due to their low self-discharge and higher efficiency as compared to the other battery chemistries. These batteries operate in an optimal temperature range. This calls for effective thermal management of these battery packs. Cold plates are a viable method for the thermal management of these packs. An active method of thermal management uses a coolant flowing through the cold plates, maintaining the battery pack temperature. Another approach to cold plate design is the use of Phase Change Materials (PCMs) as a passive cooling method. This paper suggests possible designs for the cooling plates, one using an active method of cooling and the other based on a PCM. The design considerations, thermal performance and manufacturing methods for both are discussed and analyzed. Results show that the PCM-based cold plate maintains the temperature with a very low thermal gradient for relatively shorter discharge durations, whereas the coolant flow-based cold plate shows a better performance for longer discharge durations. Finally, a 3-stage manufacturing process involving - Blanking, Indenting, and Projection Welding has been proposed to manufacture the two types of cold plates.

On the Optimization of Resistance Projection Welding Process

The resistance projection welding process for weld nuts has several parameters to reach good joint quality. In this study, three welding parameters were chosen, such as electrode force, welding period and welding current to examine the process. Design of experiments was prepared to optimize the conditions. The three above mentioned parameters were changed systematically with Response Surface Method, where the linear and the quadratic effects of the parameters can be estimated. During the experiments three output parameters, such as ultimate torque, weld spatter and inspection of screw were determined, and optimization were performed for the resistance projection welding process of the weld nut

Microstructure and Properties of Phosphorus Bronze/Brass Joints Produced by Resistance Projection Welding

In this work, we fabricated lap joints between embossed projection phosphorus bronze and flat brass through resistance projection welding (RPW). The experimental results indicated that the bronze projection moves into the softer brass without being deformed during the welding process. The tensile shear loads of the joint reached a maximum value of 273.6 N at a welding current of 5.5 kA. Under this circumstance, a reaction layer, including a columnar crystal solidification layer and a diffusion layer, is formed at the interface beside the boundary of bronze. The EDS line scan shows an elemental transition diffusion layer of about 1.5 μm between the H62 brass columnar crystal and XYK-6 phosphorus bronze. The fracture occurred on the XYK-6 side, passing through the bump instead of the welding interface, resulting in intactness of the welding interface. The results revealed that resistance projection welding is an effective method for welding copper alloys, suggesting the bright prospects of this technology in welding electrical parts.

Optimization and Improvement of the Projection Welding of Nut Based on Regression Analysis

Since it has the advantages of high production efficiency, no shunting effects, and the ability to arrange solder joints on narrow locations without the limitation of point distance, projection welding of nut has been widely used in the automotive industry. This paper presents a new welding quality prediction and analysis framework by using regression analysis techniques. The relationship between the welding parameters (welding time, welding current and electrode force) and the Pull-out load of the M6 welded square nut and the 1.5 mm thick pickled hot-rolled steel was obtained by multiple nonlinear regression analysis. The influence and interaction of welding parameters on the Pull-out load are discussed. Using this regression model, a better combination of process parameters can be obtained. The mechanical properties, microstructure and microhardness of welded joints were also investigated.

Copper-aluminium joining by novel locked projection welding process

Copper-aluminium joining by novel locked projection welding process

Quality monitoring of projection welding using machine learning with small data sets

Capacitor discharge welding is an efficient, cost-effective and stable process. It is mostly used for projection welding. Real-time monitoring is desired to ensure quality. Until this point, measured process quantities were evaluated through expert systems. This method is strongly restricted to specific welding tasks and needs deep understanding of the process. Another possibility is quality prediction based on process data with machine learning. This requires classified welding experiments to achieve a high prediction probability. In industrial manufacturing, it is rarely possible to generate big sets classified data. Therefore, semi-supervised learning is investigated to enable model development on small data sets. Supervised learning models on large amounts of data are used as a comparison to the semi-supervised models. A total of 389 classified weld tests were performed. With semi-supervised learning methods, the amount of training data necessary was reduced to 31 classified data sets.

Microstructure and joint performance during resistance projection welding of sensor support

A pyramid-shaped protruding structure was adopted to realize the connection of sensor support and mounting plate, which increased the local current density and realized the rapid melting of the metal in the bonding zone. The new welding method had high precision and realized one-time muti-spot welding. The microstructure and mechanical properties of the welded joints were studied. The hardness distribution of the joint increased from the base metal to the nugget due to the formation of martensite after welding. The average compression-shear force of the joint first increased and then decreased with the increase of current. The joint fractured along the bonding line, the fracture mode of the joint was quasi-cleavage fracture.

Influence of the Process Input Parameters on the Cross-Wire Weld Breaking Force

Cross-wire welding is a type of electric resistance welding called projection welding that is used in the production of a variety of products. This paper deals with the case where steel wires of equal radii are joined together to form a reinforced steel mesh. The objective of the study is to determine the correlation between the welding parameters and the breaking force of the weld. Each weld is cut out from the given wire mesh and tested separately by destructive testing on the universal testing machine. A modular testing fixture was constructed for the tests. Although the tests are still in the initial stage, the results already give a good insight into the influence of the process input parameters on the breaking strength of the weld.

Case Study About Resistance Projection Welding of Aluminized Steel Parts

Resistance projection welding is a non-polluting mechanized process used to obtain an assembly between similar or dissimilar metallic materials. The main advantages of this welding process are the possibility to achieve many different welded points at the same time and the long life of the electrodes compared to the spot-welding process. The paper analyses the effects of thin aluminium coating existing on mild steel parts of on the correct formation of welding points when assembling moulds for the manufacture of baking bread. From optical and electron microscopy analyses it resulted that some adjacent welded points show an interrupted fusion line, sprinkled with elongated islands of aluminium-rich compounds. The paper presents the effect of changing the values ​​of the welding parameters on the weld spot size, in correlation with the Al-rich inclusions that appear on the weld fusion zone. The best results have been obtained when the welding parameters values were the follows: electrode pressure of 2.6 bar, welding power of 19.18kVA and welding time of 7ms. The problems that occur when electric resistance welding of parts with aluminium coating have been highlighted, being useful for specialists who make products using this welding process.

The Effect of Preheating Current on the Melting Behavior of Bolt Projection Welding of Al-Si Coated Hot-Stamped Boron Steel

This study evaluated the effect of preheating on early stage melting behavior of a Al-Si coated hot stamped boron steel bolt during projection welding. A large amount of heat was generated in the early stage of projection welding. Because of the large heat generation, a rapid collapse of the projection occurred and a molten coating layer remained on the interface of the welded part. This caused welding defects such as expulsion and porosity. However, preheating helped remove the molten Al-Si coating layer by pushing it out toward the outer edge of the molten pool. This suggests that preheating can effectively minimize or remove the molten coating layer within the weld. Preheating also prevented the rapid collapse of the projection by partially melting the projection, and thus improving the contact area. These phenomena can prevent the concentration of current density at the weld interface and hence decrease heat generation. Finally, the preheating current improved nugget quality by promoting the stable growth of the melted metal and by preventing expulsion and porosity.

The Influence of Manufacturing Technology on the Properties of Chromium-Bronze Electrodes for Contact Relief Welding of Reinforcing Rods

The article discusses an effective, in comparison with common, technology of manufacturing chromium bronze electrodes for resistance projection welding of reinforcing bars. Within the framework of this technology, a method for preparing a melt with alloying with a multicomponent element, including basic elements, a matrix of copper powder and a filler of nanostructured chromium particles, is considered. The technology is based on a combined molding-plastic deformation process and makes it possible to obtain a finished resistance welding electrode of type D in one operation. The results of microstructural, X‑ray micro-spectral and local energy dispersive (micro) analysis of electrode samples obtained by different technologies, explaining the main nature of the loss of electrode performance, are presented. The results of fractographic studies of the contact surface of the electrodes are considered. Electrical conductivity and mechanical properties were studied for all electrode samples. The results of tests on a resistance welding machine with an assessment of the wear of the electrodes and the reasons for their failure are presented

프로젝션용접에서 돌기 크기에 따른 용접 특성

Purpose: Projection welding is a resistance welding method in which materials are welded using the heat generated by passing an electric current to the projection of the metal base material. In this study, the characteristics of the projection welding quality were considered in terms of the projection size for the strut of a car rear suspension module.<BR>Methods: Five welded specimens with a projection size ranging from 0.4 mm to 1.4 mm in intervals of 0.2 mm were prepared, and the corresponding surface appearance, tensile strength, and nugget diameter were compared.<BR>Results: For a projection size of 0.8 mm or higher, the tensile strength satisfies all the specifications, and the projection height of 1.2 mm corresponds to the highest quality. For a projection size of 0.6 mm or higher, the nugget diameter satisfies the specifications. However, the projection size of 1.2 mm exhibits a large standard deviation.<BR>Conclusion: Considering the obtained results, the projection size and lower specification of the nugget diameter are recommended to be increased to 1.2 mm and 6.0 mm, respectively.