Showing papers on "Electric resistance welding published in 2023"

Characteristic of keyhole, molten pool and microstructure of oscillating laser TIG hybrid welding

Abstract: In this research, the dynamic change of laser keyhole of vertical oscillating laser keyhole was studied, and it was found that the laser keyhole depth was periodic. The keyhole depth decreased with the increase of oscillation amplitude and frequency, but the stability of the keyhole increased. This was closely related to the energy distribution of oscillating laser. The special energy distribution made the “two molten pools“ phenomenon appear in oscillating laser tungsten inert gas (TIG) hybrid welding, and the grains in the keyhole molten pool were smaller than those in the conduction molten pool. The narrow gap (NG) oscillating laser TIG hybrid welding (OL-T) was carried out, and the microstructure and mechanical properties of OL-T welding were compared with that of TIG welding and general laser TIG hybrid welding (L-T). The grain of the OL-T welding seam was refined because the OL-T welding had a lower line energy, which changed the crystalline morphology of the welding seam. The tensile strength of the weld joint was almost equivalent to that of TIG welding and base metal, reaching 559 MPa. It was observed that there was no lack of sidewall fusion in the welding seam of the NG OL-T welding, and the weld efficiency was much higher than that of TIG welding. The morphology of the molten pool in oscillating laser-TIG hybrid welding and the arc shape in the groove were collected using high-speed cameras. It was observed that the elimination of lack of sidewall fusion in NG welding mainly depended on the direct heating on the sidewall and stirring molten pool by oscillation laser.

The deformation analysis of friction stir welding with different clamping distances for large thin-walled joints

Abstract: Clamping scheme may change the local stiffness and affect the welding deformation which is very important for the large thin-walled joints connected by friction stir welding with heavy load and heat production. In this paper, the welding experiments of large thin-walled joints were conducted and the numerical simulation model is established based on three-dimensional stress mapping method. The accuracy of the numerical model is verified and welding deformation with various clamping distances is discussed. The restraint intensity index is employed to describe the influence of clamping distance on the stiffness of welding seam and welding deformation. The mechanism of welding deformation with the effect of clamping distance is well revealed by the analysis of welding stress and restraint intensity.

Difficulties and redressal in joining of aluminium alloys by GMA and GTA welding: A review

Abstract: The article reviews the difficulties and its redressal in fusion welding (especially the most used welding processes in the industry; gas metal arc (GMA) and gas tungsten arc (GTA) welding) of aluminium alloys. The more excellent thermal conductivity, solidification shrinkage, oxide formation, and thermal expansion coefficient cause more difficulties welding aluminium alloy than other materials. Welding parameters (such as welding current, welding voltage, shield gas flow rate, welding speed, torch location, etc.) have a complicated and non-linear relationship with the weld's quality and the joint's mechanical characteristics. Several techniques are suggested for improved weld quality and joint strength, including pulsing the current, post-weld heat treatment, proportional mixing of the shielding gases, speedy shielding gas injection, and many more. Due to various materials varied chemical and thermal characteristics, the GMA and GTA welding of dissimilar aluminium alloy exhibits more difficulties. To get around the challenges, adjusting the torch position and choosing a filler material that works with both aluminium alloys are practiced.

Quality characteristics and analysis of input parameters on laser beam welding of hairpin windings in electric drives

Abstract: Abstract The relevance of electric drives in individual mobility is continuously increasing. This requires the use of new manufacturing processes in automotive production. In modern stators, the so-called hairpin winding is used. The production process entails rectangular copper conductors (hairpin) to be contacted by laser beam welding. To avoid temperature peaks due to resistance heating in the current-carrying wire, a high cross-sectional area in the welding seam is required. Therefore, the pore volume must be considered. This is proven by thermographic investigations of electrically stressed hairpin connections. To optimize the welding process, effects of the previous manufacturing steps and the welding parameters themselves must be taken into account. This paper analyses systematically the impact of all translational and rotational deviations on the corresponding welding quality. The tests are performed by using a disk laser. A laser spot with a focus diameter of 170 μm is compared to a statically shaped beam, capable of distributing power in core and ring beam. As an additional parameter, the influence of oxygen content in the copper wire is investigated by using electrolytic tough pitch copper (Cu-ETP) and oxygen-free copper (Cu-OF). Furthermore, the interaction between an additional cutting step before contacting and the welding path is considered. X-ray computed tomography (CT) is used to analyse the welding quality. The main finding of the studies is the significant influence of the gap and height offset between the wire ends on the resulting cross-sectional area. In addition, a low oxygen content of the copper and the use of static beam shaping reduce weld spatters, porosity and increase process stability. Three geometries in the welding path perform better in gap bridging and cause less spatters.

Seam Properties of Overlap Welding Strategies from Copper to Aluminum Using Green Laser Radiation for Battery Tab Connections in Electric Vehicles

Abstract: Laser beam welding of metals has progressed dramatically over the last years mainly arising from joining applications in the field of electromobility. Allowing the flexible, automated manufacturing of mechanically, electrically, and thermally stressed components, the process is more frequently applied for joining highly reflective materials, for example for battery tab and busbar connections. The local, non-contact energy input favors this welding technology; however, joining of copper and aluminum sheets still poses a challenge due to the physical properties of the joining partners and intermetallic phases from dissimilar metal interaction, which reduce seam performance. The use of green laser radiation compared to infrared laser radiation offers the advantage of a significantly increased absorptivity for copper materials. A changed incoupling behavior is observed, and a lower deep penetration threshold has been already proven for 515 nm wavelength. When copper and aluminum are welded with the former as top sheet, this welding mode is essential to overcome limited aspect ratios from heat conduction welding. However, the opportunities of applying these beam sources in combination with spatial power modulation to influence the interconnection area of copper-aluminum joints have not yet been studied. The aim of this work is therefore to investigate the seam properties and process stability of different overlap welding strategies using green laser radiation for dissimilar metal welding. A microstructural analysis of the different fusion zones and mechanical strength of the joints are presented. In addition, the experimental parameter sets were analyzed regarding their application in battery module busbars by examining the electrical resistance and temperature distribution after welding. A parameter window was identified for all investigated welding strategies, with the stitched seam achieving the most stable results.

The Effect of Electrode Geometry and Pre-heating Treatment on Resistance Spot Welding Strength

Abstract: Resistance spot welding (RSW) is one of the most significant and common metal joining methods used in industries. The present paper discusses the comparative performance of resistance spot welding electrodes of nontraditional design with the traditional one of 8 mm contact diameter in welding a 1.5 mm thick low carbon steel sheet used in automobile structural bodies and bridges. The modified electrode tip surface center was machined to have three different holes of 2, 3, and 4 mm depth and three different diameters of 2, 4, and 6 mm producing nine different hollow electrode dimensions. As well as the influence of pre-heating temperature on the mechanical properties of the weld joint was investigated by considering the other main parameters of welding time, current, and force are constant. The shear tensile test and torsion test examinations are carried out to investigate the mechanical properties. Also, to interrupt the results, a macrograph examination was conducted to determine the nugget size formation. The results show that the increase or decrease in the strength of the weld joint is greatly influenced by the proper selection of the modified electrode geometries. Also, the results indicated that the maximum improvement in shear tensile strength and torsional strength is about 140% and 150% compared to the traditional one. Furthermore, pre-heating processes helped decrease the contact resistance at the faying surfaces and improve the weld tensile strength and torsional strength to about 141% and 171% at 200 oC. Moreover, improvement may be achieved by slightly increasing pre-heating temperatures

Effect of welding position and direction on the interfacial microstructure and mechanical properties of double-pass friction stir lap welded A6061/Q235 joints

Abstract: The mechanical properties of a conventional single-pass friction stir lap welding (FSLW) aluminum/steel joint were difficult to meet the ever-changing industrial requirements. In this work, double-pass dissimilar FSLW was adopted to improve the mechanical properties of the joints between A6061 aluminum alloy and Q235 steel plate. After the first pass of friction stir welding, the welding position and welding direction were altered during the second pass, resulting in the formation of four double-pass weld joints with various plate configurations. A double-pass joint enlarged the interfacial bonding area, which significantly improved the mechanical properties of the joints. Specifically, the ultimate tensile load of the joints was increased by 48.8 % when the second pass was located on the retreating side of the first pass in comparison with single-pass joints. In addition, the fracture mode of the double-pass joint shifted from the interface fracture of the single-pass joint to the internal fracture of the heat-affected zone.

Wire electrode of 5754 aluminum modified by PVD-thin film depositions

Abstract: Abstract Manufacturers of welding wire electrodes for GMAW welding adapt the alloy compositions of welding wire electrodes in order to adjust the weld pool behavior and the properties of the weld. Additively manufactured components in various sizes and with complex structures and multi-axial stress states place diverse demands on the material. The filler wire can significantly influence the material properties. The approach shown here describes the possibility of coating welding wire electrodes by physical vapor deposition, which enables flexible adjustment of the welding material composition. The element content in the weld metal can be adjusted within certain limits via the coating thickness. In the arc, applied thin-film coatings with coating thicknesses < 1 µm pass into the molten phase together with the substrate wire electrode according to ISO 18273—S Al 5754 (AlMg3). Microalloying elements such as TiB 2 or Ti added to the weld pool in this way change the composition and thus influence the microstructure in the weld metal. This results in a grain refinement of up to 46%, which in turn has a positive effect on hot cracking susceptibility. PVD-coated welding electrodes also show changes in arc characteristics. With increasing TiB 2 layer thickness, the arc length decreases by up to 44%, while the arc current increases. The fusion penetration behavior changes from a narrow finger-shaped to a round fusion penetration.

Solid-state welding

Abstract: The chapter presents the definitions and essence of cold welding, ultrasonic welding, and explosion welding. Shows schemes and main parameters of the welding processes, recommendations on their selection, features, and mechanisms of welded joints formation. Also, explains the influence of processes technological parameters, and welding conditions on metallurgical processes, formation of structure, and properties of welded joints. Moreover, presents the structure of welding equipment, advantages, disadvantages, and areas of application of the methods, product examples.

Influence of the Process Parameters on the Properties of Cu-Cu Ultrasonic Welds

Abstract: Ultrasonic welding (USW) is a solid-state welding process based on the application of high frequency vibration energy to the workpiece to produce the internal friction between the faying surface and the local heat generation required to promote the joining. The short welding time and the low heat input, the absence of fumes, sparks or flames, and the automation capacity make it particularly interesting for several fields, such as electrical/electronic, automotive, aerospace, appliance, and medical products industries. The main problems that those industries have to face are related to the poor weld quality due the improper selection of weld parameters. In the present work, 0.3 mm thick copper sheets were joined by USW varying the welding time, pressure, and vibration amplitude. The influence of the process variables on the characteristics of the joints and weld strength is investigated by using the analysis of variance. The results of the present work indicate that welding time is the main factor affecting the energy absorbed during the welding, followed by the pressure and amplitude. The shear strength, on the other hand, resulted mostly influenced by the amplitude, while the other parameters have a limited effect. Regardless the welding configuration adopted, most welds registered a failure load higher than the base material pointing out the feasibility of the USW process to join copper sheets.

Weld Quality Analysis of High-Hardness Armored Steel in Pulsed Gas Metal Arc Welding

Abstract: As improving fuel economy and performance through weight reduction in vehicles are recognized as important tasks, the defense industry is researching ways to reduce the weight of armor plates for combat vehicles and increase bulletproof performance and durability. Most armor plates in combat vehicles are manufactured using weld joints. High-hardness armor (HHA) is used to make armor plates; however, its mechanical properties deteriorate because of hydrogen embrittlement and high-temperature softening during welding. Welding defects, such as pores and cracks, occur frequently. In this study, HHA steel was subjected to single-pulse gas metal arc welding (GMAW), and the welding performance of the shielding gas and heat input was analyzed by the United States army tank-automotive and armaments command (TACOM) standard. The specimen cross-section was visually examined, and hardness, tensile, and impact tests were used to identify the mechanical properties based on the welding conditions. Additionally, flux cored arc welding (FCAW) and GMAW were used and compared, and spatter image analyses were used to assess the integrity of the welding process of the HHA plate applied to a combat vehicle. As a result of the experiment, as the CO2 content and heat input increased, the mechanical strength of the welded zone and the integrity of the welding process deteriorated.

An introduction to welding of metallic materials

Abstract: In this chapter, a short history of the welding process is given, in addition to the stages that welding processes were developed in the last century until now. A brief introduction of the principles of different types of welding processes based on the used source of energy is shown. Different types of welding processes are explained briefly. More details about manual metal arc welding are given as an example of arc welding. The metallurgical aspects and weldability of the metals, steel-based alloys, in particular, are explained, especially in fusion welding processes, with or without using filler metals, considering the effect of the chemical composition and microstructures of the fusion zone and heat-affected zone on the whole behavior of the weldments. General welding defects in metallic alloys are shown either in the fusion or solid-state welding methods. Moreover, pre and/or postheat treatments, to minimize the defects and residual stresses are shown. Appropriate testing methods to evaluate the mechanical and corrosion behavior of the weldments are explained. At the end of the chapter, the general advantages and disadvantages of welding processes are listed.

Optimization of Multi-Objective Process Parameters of TIG-MIG Hybrid Welding On EN24 Mild Steel Material Using the Grey-Based Taguchi Method

Abstract: Abstract Metal Industry and Machine Technology Development Enterprise is Ethiopia's leading manufacturing industry, producing a diverse range of industrial machinery and products. The main welding process used to join the products is MIG welding, which has several flaws, including low weld-metal toughness, spatter formation, undercut formation, and finally poor tensile strength and toughness. The company also uses TIG welding, which uses an inert gas to produce less smoke and fumes. While this technology produces precise welds, it is a time-consuming operation with a lower production rate. As a result, a special type of welding process is required that incorporates the properties of both types of welding processes. As a result, the hybrid TIG-MIG welding configuration was proposed. The optimization of process parameters of EN24 mild steel material for TIGMIG hybrid welding is presented in this paper. The test was carried out on a 6 mm EN24 mild steel plate. The butt joint configuration was used. MIG welding current, TIG welding current, MIG welding voltage, TIG welding voltage, and welding gun travel speed were used as process parameters. A single-level L27 orthogonal array is used to optimize process parameters. Tensile and hardness tests are used to evaluate the mechanical properties of the weld joint. The optimum level setting of the test, according to the mean effect plot of GRG, is MIG welding current of 200 A, MIG welding voltage of 15 V, TIG welding current of 200 A, TIG welding voltage of 18 V, and welding gun travel speed of 5 mm/s. The significant process parameters were investigated using ANOVA. MIG welding current and MIG welding voltage were significant factors in the ANOVA, with percentage contributions of 44.19% and 49.20%, respectively. Five confirmation tests were performed, and the results show that the mean grey relational grade of the conformation test was 0.7594, which falls within the 90% confidence interval, indicating that the experiment is reliable. Finally, MIG welding, TIG welding, and TIG-MIG hybrid welding processes were compared, with the results indicating that TIG-MIG hybrid welding has the highest hardness and tensile strength of all. Based on the findings, it is possible to conclude that the company should use the hybrid welding method to improve the weld joint's hardness and tensile strength.

Fundamentals of Dissimilar Metal Joining by Arc and Resistance Welding Processes

Abstract: This chapter presents the fundamentals, causes and remedies related to the common issues (asymmetric weld, unmixed zone, intermetallic compound, cracking of weld and HAZ, residual stress and distortion) encountered in joining of dissimilar metals combinations by arc, resistance welding. Fusion welding processes, namely GTAW, Pulse, cold metal transfer and Narrow gap variants of GMAW, SMAW and SAW, have been described considering the dissimilar metal joining. Additionally, dissimilar metal joining using brazing and braze welding has also been elaborated.

Dissimilar Welding of AISI 304 and AISI 310 Steels Using Metal Inert Gas Welding

Abstract: Thermal, mechanical and chemical properties decides the quality of welding dissimilar metals, as controlling of welding variables is difficult to achieve the desired output of weld joint. Welding of dissimilar metals is a difficult task, as one has to take care of the metallurgical changes taking place in both the metals due to heat produced during welding. Proper selection of welding variables plays an important role in obtaining sound weld joint. Austenitic stainless steel plates of AISI 304 and AISI 310 are welded by MIG welding. Three factors namely filler wire feed rate, welding current and edge included angle are taken as input variables of welding. Grain size and hardness are the output variables. Fifteen combinations of experiments are conducted by considering Box Benhken Design for three factors and three levels. The effect of welding variables on grain size and hardness of the welded joint was studied. The welding variables were optimised using Response optimizer for minimum grain size and maximum hardness of weld joint.

Resistance Spot Welding and Laser Welding Effect on Nickel Tab for Electric Vehicle Battery Development

Abstract: In this study, the joint ability of two different joining techniques, namely resistance spot welding and laser welding of nickel weld interfaces and joint microstructure were addressed. Similar materials of nickel joint were used to investigate the parallel connection of tab cells for electric vehicle (EV) battery development. It was found that using the parameters discussed, the joining of two similar nickel was successfully achieved via these welding methods. The results show that the material joints fabricated using laser welding had the highest average stress value of 155.86 MPa, whereas the average for nickel joints of resistance spot welding was 122.25 MPa. In addition, the results of FESEM analysis on the cross-section of the weld material also found that the length of the surface for the material being connected and affects the stress value. For resistance spot welding process, 0.09 s of welding time promoted the formation of sound weld beads with better control of penetration depth and excellent joint interface. Compared to the resistance spot welding process, laser welding produced a better weld interface, which contributes to a higher strength value.