Pressure Welding Process Research Articles

Enabling magnetic pulse welding for dissimilar tubular arrester cable joints

Climate change exacerbates the need for resource-efficient and cost-effective production processes across manifold industries, including the field of electrical connections. This specific field is characterized by a conflict of objectives, i.e., weight reductions while maintaining joint strength and electrical conductivity. From a material point of view, the use of aluminum as a conductor material is suitable for this application, as it is lighter than copper, a classical conductor material. Electrical conductors are often used in the form of flexible cables, so-called stranded wires. This type of conductor as well as the fact that the sole use of aluminum in electrical systems is not feasible, e.g., because the predetermined connection terminals of power electronic components are made of copper, creates a substantial demand for dissimilar aluminum-copper cable arrester joints. However, traditional fusion-based welding processes have proved incapable of reliably producing these dissimilar aluminum-copper joints because of thermophysical effects and chemical incompatibilities, the latter eventually leading to the formation of intermetallic phases. These phases adversely affect the quality of the joint in terms of both mechanical and electrical performance. Yet, magnetic pulse welding, a pressure welding process, is ideally suited for producing dissimilar metal joints on the basis of a low energy input during the welding process. Consequently, the formation of intermetallic phases is restrained. However, magnetic pulse welding has not been sufficiently investigated for the reliable contacting of stranded cables to tubular arresters. As a result, this paper focuses on the fabrication of tubular stranded cable arrester joints using magnetic pulse welding. To shed light on possible material combinations, aluminum-to-aluminum and copper-to-copper joints as well as their dissimilar counterparts are welded. Subsequently, the joints are characterized with regard to their microstructure and quasi-static material strength. Electrical characterization comprises the four-wire Kelvin measurement method to evaluate the resistance of the electrical joints. The results demonstrate that magnetic pulse welding is ideally suited to join the aforementioned material combination and joint configuration due to its process characteristics eventually leading to material continuity. As a result, the stranded wires are welded to the tubular arresters rather than crimped. Consequently, a comparative analysis of the joint properties with those of the joining partners shows that the measured electrical resistances and mechanical tensile forces may be considered very good.

Study on notch tensile properties of Magnetically Impelled Arc Butt (MIAB) welded carbon steel tubes

Magnetically Impelled Arc Butt (MIAB) welding is a pressure welding process that uses the circumferential rotating arc to cause uniform heating of the faying surfaces. In this work, notched tensile testing of MIAB welded Carbon steel was carried out to determine the notch sensitivity of Thermo-Mechanically Affected Zones (TMAZ) and to compare the notch tensile property of these zones with the base metal property. In MIAB welding, after sufficient melting of the faying surface, a short pulse of high current is applied to expel the molten metal and impurities from the interface before welding. Insufficient expulsion and formation of Light Band (LB) zone at weld interface resulted in lower Notch Tensile Strength (NTS). Incomplete expulsion with lower upset current at the weld interface contributes to lower Normalized Notch Strength Ratio. Instead higher upset current contributed to higher NTS due to complete expulsion and stronger acicular ferrite formation. Other TMAZs away from the weld interface showed higher notch tensile strength with Notch Strength Ratio (NSR) and Normalized Notch Tensile Strength Ratio (NTSN) greater than unity.

Improving and monitoring the magnetic pulse welding process between dissimilar metals

Conventional fusion welding of dissimilar metals is often limited due to the different thermo-physical properties of the joining partners. In consequence, brittle intermetallic phases (IMC) can occur. Utilizing a pressure welding process like magnetic pulse welding (MPW) reduces the risk of IMCs significantly. Furthermore, this welding process has an outstanding short process duration in the range of a few microseconds, which makes it predestined for mass production. At the same time, this advantage challenges the process observation, inline-quality assurance hardware, and the design of the tool coils. The paper presents two strategies for reducing the energy input during MPW to increase the tool coil lifetime. The first approach, the introduction of a reactive nickel interlayer between steel and aluminum, leads to a significant welding energy reduction. Compared to aluminum samples joined by laser welding, the load-bearing capability of the resulting hybrid MPW driveshaft samples is higher in static torsion tests and similar in cyclic tests. The second approach is based on a novel process monitoring system that helps to analyze the characteristic light emission. The capability of the process monitoring system is presented on the example of a MPW-joined multimaterial part made of stainless steel, aluminum, and copper.

An experimental study and analysis of various cylindrical pin diameters in friction stir welded AA7075-T6 and A384.0-T6 aluminium alloys of butt joint

The Friction Stir Welding is one of the solid state pressure welding processes. To evaluate the joint characteristics, the three factors viz. Speed of the Tool rotation, Speed of weld process and various diameters of cylindrical pin are taken in to account. Without using any filler material, the two materials are joined by the application of the stirring action and an applied axial load using rotation of welding tool. The tool design, size and the shape will vary according to the material to be joined. The aim of the design of the tool is not to remove the materials but to develop the sufficient heat and the uniform mixing of the materials to join work pieces. During the mixing of the materials, the flow of the materials will affect the welding quality. So tooling design, size and shapes are the most important factors. In this article same thickness of the aluminium dissimilar materials were used with different diameters of the tool pin in cylindrical shape. The design of Experimental investigation has been performed and subsequently the major finding has been discussed. The ultimate tensile strength has been identified as 102.98 MPa.

Correlations between the Surface Topography and Mechanical Properties of Friction Stir Welds

Friction stir welding is a modern pressure welding process, which is particularly suitable for aluminum alloys. Several studies have been conducted to investigate the interrelations between the process parameters, such as the welding speed and the tool rotational speed, and the resulting mechanical properties of the joint. This study explored the connections between the surface topography of the welds, such as the flash height and the seam underfill, and their mechanical properties (ultimate tensile strength; elongation at break; and Vickers hardness). For this purpose, a total of 54 welding experiments at three different welding speeds were conducted using the aluminum alloy EN AW-6082-T6. The welded specimens were examined using visual inspection, topographic analysis, metallography, hardness measurements, and uniaxial tensile tests. Afterward, a statistical analysis was performed in order to determine the correlation coefficients between the surface topography and the mechanical properties of the welds. The strongest correlations were between the surface topography and the ultimate tensile strength. Thereby, the most pronounced relations were found between the seam underfill as well as the arc texture formation of the weld and its ultimate tensile strength. The interrelations between the surface topography and the elongation at break, as well as the hardness of the welds, were less pronounced. The higher the welding speed became, the less pronounced the interrelations were. The results show the potential of a non-destructive monitoring system based on the topography to support the prediction of the acceptability of welded parts.

An Assessment of Non Consumable Welded Joint- Friction Stir Spot Welding

Friction stir spot welding (FSSW) is a pressure weldingprocess where the workpieces are operated below their melting points. FSSW is one of the processes derived from Friction Stir Welding (FSW) Technology. Friction stir welding was invented by The Welding Institute (TWI) in 1991 and proven experimentally. FSSW is found to be environment friendly and a very efficient process. This process is rapidly growing and is replacing the resistance spot welding. FSSW have various applications which include industries like automobile, aerospace, ship building, construction and electrical.FSSW has been successfullyused to join several materials used in the above mentioned industries. Inthis review, FSSW studies are briefly summarised in terms different parameters for joining processes.

Uticaj neusklađenosti na granične krive širenja zamornih prslina osnovnih materijala tipa S690KL, S960KL i S960TM i njihovih, elektrolučno u zaštiti gasa, zavarenih spojeva

Nowadays, one of the basic trends in the industry is the environmental impact reduction, in other words the weight decreasing of structural elements and structures, which can be approached by applying different high strength steels. In case of different steel structures, the main manufacturing and joining technology is the welding, the conventional and advanced methods of fusion and pressure welding processes. Beside the weight decreasing, the reliability and safety requirements according to steel structures have significant grown. During the welding process, the welded parts are affected with heat-effect and mechanical loads, which result in inhomogeneous welded joint. The inhomogeneity of the welded joints appears both in microstructural (local) and in geometrical (both local and global) aspects. The changes in microstructure and geometry appear in deflections (basically acceptable), or rather in failures (basically unacceptable); and these influence both the behaviour and the loadability of welded joints. Discontinuities in base materials and their welded joints have especially high danger in case of cyclic loading conditions, which are typical for different structures and structural elements (e.g. bridges, vehicles). There are different standards and prescriptions containing fatigue crack propagation limit curves and rules for the prediction of the crack growth; simple and two-stage crack growth relationships can be found in the literature, most frequently based on the Paris-Erdogan law. The paper summarizes and presents the results according to our fatigue crack growth investigations on Weldox 700E and Weldox 960E quenched and tempered (Q+T) and on Alform 960M thermomechanically treated (TM) high strength steel base materials and their gas metal arc welded joints. The mismatch effect has also been studied; matched, overmatched, undermatched and matched/overmatched (mixed-matched) welded joints were investigated. 15 mm thick plates were used for the investigations, statistical aspects were applied both for presenting the possible crack locations in the real plates, as well as for processing the measured data. Furthermore, the results will be compared with each other, and fatigue crack propagation limit curves will be derived using simple crack growth relationship.

Pressure Welding Processes of Tubular Parts and Pipe Segments

Abstract The joining of tubular (hollow, sectioned) parts to each other or for rods, sheet-like pieces and occasionally for pipe segments, is often achieved by using technology that uses a pressure welding process. These processes use mostly electrical, thermochemical or mechanical energy, and the implementation is butt, stud or projection welding. Most the pressure welding processes are suitable for the joining of different quality materials. This article summarizes the possible process variations.

Exploration of magnetically impelled arc butt welded SA210GrA tubes for boiler applications

Abstract Magnetically impelled arc butt (MIAB) welding is a pressure welding process used for joining of pipes and tubes with an external magnetic field affecting arc rotation along the tube circumference. In this work, MIAB welding of SA210GrA tubes were carried out to study the microstructure of weldedments. The effect of arc current on the weld interface is also detailed and is found to be defect free at higher values of arc currents. The results reveal that MIAB welded specimens shows superior structural property correlation for high pressure applications with an added benefit of improved productivity at lower cost. The study will enable the use of MIAB welding for high pressure applications in power and defence sectors.

High cycle fatigue and fatigue crack propagation design curves for 5754-H22 and 6082-T6 aluminium alloys and their friction stir welded joints

Friction stir welding (FSW) is a dynamically developing version of pressure welding processes. Nowadays, learning the properties and behaviour of the welded joints is an important direction of investigation, especially under cyclic loading. The research work aimed (i) to demonstrate the behaviour of FS welded joints under cyclic loading conditions and (ii) to determine fatigue design curves for two aluminium alloys and their welded joints made by the FSW process. Experiments were performed on 5754-H22 and 6082-T6 aluminium alloys and their welded joints; high cycle fatigue (HCF) and fatigue crack propagation (FCG) tests were performed. Statistical approaches were applied during the experiments and the evaluation process. HCF design curves were determined based on the staircase method and FCG design curves were determined by our own previously developed six-step method. The results of the HCF and FCG tests on FS welded joints confirm the applicability of the applied FSW technology and show good correspondence with results of the comparative base materials and welded joints that can be found in the literature. Based on our experimental results and the evaluation methods used, statistically established parameters of HCF and FCG design curves were calculated.

Features of Plasma-Electrolytic Coatings Formation on Metalware Surface

The paper presents the principal advantages of plasma-electrolytic coating method that characterize it as a highly promising technology. It is shown that these advantages are provided by the integrated nature of the effect, representing a combination of the main types of impacts on a surface: electrical, thermal, mechanical and chemical. This combination distinguishes the method of plasma-electrolytic treatment from many other widespread in up-to-date technology combinations composed generally of two types of impacts. It is suggested that the process of plasma-electrolytic coating is carried out by the mechanism of metal pressure welding that is confirmed by the results of tests for determining quality ratings of coatings. It is shown the thermodynamic and kinetic unity of these processes that allows plasma-electrolytic coating to be put in class of metal pressure welding processes and to consider the processes of coating by plasma-electrolytic method and pressure welding from a common methodological framework. The paper presents the results of the structure and composition studies of zinc plasma-electrolytic coatings on a strip for armoring cables of group A (GOST 3559-75). The researches were carried out using scanning electron microscopy, microroentgenspectral analysis and differential scanning calorimetry.

Reflection and Mode Conversion of Fundamental Torsional Guided Wave Mode From Lack of Bonding in Induction Pressure Welding

Interaction of fundamental torsional ultrasonic pipe guided mode T(0, 1) from defects caused by induction pressure welding (IPW) process is studied using three-dimensional (3D) finite element (FE) analysis validated by experiments. Defects are assumed as cross-sectional notches along the weld bond-line, and both surface-breaking and embedded features are considered. Results show that T(0, 1) mode reflection from weld defects is strongly influenced by features of the weld itself. However, with supplementary results such as the mode-converted flexural F(1, 3) and F(1, 2) modes and circumferential variation of T(0, 1) reflection, there is potential for an effective screening solution.

Синергетическая концепция формирования металлических покрытий плазменно-кавитационным способом и их свойства

The paper presents the principal advantages of the method of plasma-cavitating coatings formation that characterize it as a highly promising technology. It is shown that these advantages are provided by the integrated nature of the effect, representing a combination of the main types of impacts on a surface: electrical, thermal, mechanical and chemical. This combination distinguishes the method of plasma-cavitating treatment from many other widespread in up-to-date technology combinations composed generally of two types of impacts. It is proposed that the process of plasma-cavitating coatings formation is carried out by the mechanism of metal pressure welding that is confirmed by the results of tests for determining quality ratings of coatings. The thermodynamic and kinetic unity of these processes is shown that allows plasma-cavitating coating to be put in class of metal pressure welding processes and to consider the processes of coating by plasma-cavitating method and pressure welding within a common methodological framework.

Experimental- and numerical-based studies for magnetically impelled arc butt welding of T11 chromium alloy tubes

Magnetically impelled arc butt (MIAB) welding is a pressure welding process used for joining of pipes and tubes with an external magnetic field affecting arc rotation along the tube circumference. Past studies based on experiments and finite element analysis (FEA) suggested that the weld quality can be significantly improved by proper adjustment of its input parameters such as current, voltage, flux density, etc. Experiments are useful for understanding the physics behind the process, but the quantification and optimization of the MIAB process needs a thorough numerical investigation. Therefore, the present work presents a combined experimental and numerical study for investigating the arc speed indicator of the T11 grade chromium alloy tubes of the MIAB process. Firstly, experiments on the MIAB process are conducted, and the arc speed is measured based on the four inputs (welding current, welding voltage, magnetic coil current, and voltage). This is followed by introduction of a numerical approach of multi-gene genetic programming (MGGP) to formulate a functional relationship between arc speed and the four design variables. The statistical error metrics based on the square of correlation coefficient, relative error (%), and root mean square were used to validate the model performance against the experimental data. The proposed model can be utilized to select the best combination of input variables to optimize the arc speed, which has a vital role in governing the weld quality. In addition, 2-D analysis conducted reveals that the welding current influence the arc speed of the clay the most followed by coil current and coil voltage.

Design and Fabrication of Friction Stir Welding End-Effector for an ABB IRB1410 Robot

<p>The paper propose modelling and fabrication of friction stir welding end-effector for ABB IRB1410 robot. A dynamically developing version of pressure welding processes, join material without reaching the fusion temperature called friction stir welding. As friction stir welding occurs in solid state, no solidification structures are created thereby eliminating the brittle and eutectic phase’s common to fusion welding of high strength aluminium alloys. In this paper, Friction stir welding is applied to aluminum sheets of 2 mm thickness. A prototype setup is developed to monitor the evolution of main forces and tool temperature during the operation. Pressure of a gripper plays a major role for tool rotation and developing torque. Fabrication of the tool has done. Force calculations are done by placing the sensors on the outer surface of gripper. Methods of evaluating weld quality are surveyed as well.</p>

Experimental and Simulation Modeling of Nickel-Based Superalloy Pressure Welding Process

The paper presents the results of finite element analysis of plastic deformation in the contact zone of dissimilar superalloys subjected to pressure welding. The results are compared for the two cases: with and without relief on the surfaces of parts to be welded. It is shown that the relief made on the surface can either decrease or increase the area of deformation stagnant zones, depending on the relief shape. The results of simulations are compared with the experimental test results.

Investigation of Cold Pressure Welding: Cohesion Coefficient of Copper

Joining materials by forming is an interesting approach to the manufacture of hybrid (multi material) parts. By establishing a cold pressure weld between metallic surfaces, high quality joints with superior properties can be achieved. Reliable cold welding conditions are difficult to set up, however, since the weld initiation requires extraordinary clean, virtually sheer surfaces. Until today such conditions could only be achieved under a high vacuum conditions. Various studies on cold pressure welding reported that under vacuum welds can be established at significantly lower deformation than in a normal atmosphere. Since adverse deformation is currently needed in industrial cold pressure welding processes like the cold roll cladding of metal bands, a new process with in-line electrochemical surface treatment, is investigated. The ECUF process is intended to supply clean and thereby highly activated surfaces to the cold pressure welding process.This paper presents first results on the weld-ability of copper specimens with regard to the influence of the welding environment: air, argon and KCl solution. Butt welds were made by pressure welding of previously fractured specimens.

Characterization of magnetically impelled arc butt welded T11 tubes for high pressure applications

Abstract Magnetically impelled arc butt (MIAB) welding is a pressure welding process used for joining of pipes and tubes with an external magnetic field affecting arc rotation along the tube circumference. In this work, MIAB welding of low alloy steel (T11) tubes were carried out to study the microstructural changes occurring in thermo-mechanically affected zone (TMAZ). To qualify the process for the welding applications where pressure could be up to 300 bar, the MIAB welds are studied with variations of arc current and arc rotation time. It is found that TMAZ shows higher hardness than that in base metal and displays higher weld tensile strength and ductility due to bainitic transformation. The effect of arc current on the weld interface is also detailed and is found to be defect free at higher values of arc currents. The results reveal that MIAB welded samples exhibits good structural property correlation for high pressure applications with an added benefit of enhanced productivity at lower cost. The study will enable the use of MIAB welding for high pressure applications in power and defence sectors.

Behaviour of AlMg3 Base Material and its Friction Stir Welded Joints under Cyclic Loading Conditions

The friction stir welding (FSW) is a dynamically developing version of the pressure welding processes. Nowadays, the knowing of the properties and the behaviour of the welded joints is an important direction of the investigations, especially under cyclic loading. The research work aimed (i) to demonstrate the behaviour of the FSW welded joints under cyclic loading conditions; (ii) to confirm the applicability of the used friction welding technology. Experiments were performed on 5754-H22 aluminium alloy and its welded joints; both high cycle fatigue (HCF) and fatigue crack propagation (FCG) tests were executed. HCF limit curves were determined based on staircase method. Statistical behaviour of the base material and the welded joints under FCG was represented by the cutting of the specimens, in other words by the using of different crack paths. FCG limit curves can be determined by own developed six step method. The investigations and their results were compared with each other and with the results can be found in the literature.

Effect of applied current on the formation of defect in PWR nuclear fuel rods in resistance pressure welding process

The welding of zirconium alloy components is one of the most critical processes in the fabrication of nuclear fuel rods used in pressurized water reactors. For this, various welding processes, such as gas tungsten arc welding, electron beam welding, laser beam welding, and resistance pressure welding (RPW), are used around the world. In Korea, the RPW process is being used to fabricate nuclear fuel assembly fuel rods. This study investigated changes in the weldment shape owing to welding conditions such as welding current, welding force, and overlapping. The welding soundness of the weldment was evaluated by hydraulic burst test. The welding temperature of the weld zone was measured using a thermal infrared method. Discontinuous black spots in the weld line, regarded as a non-bonding defect, were confirmed as spots caused by the carbide precipitation of zirconium during welding.