Magnetic Pulse Welding Research Articles

Analytical Estimation of Electromagnetic Pressure, Flyer Impact Velocity, and Welded Joint Length in Magnetic Pulse Welding

Magnetic pulse welding involves the joining of two metallic parts in a solid state by the use of a short and intense electromagnetic impulses and the resulting impact between the parts. The coalesced interface undergoes visco-plastic deformation at a high strain rate and exhibits a wavy shape at a microscopic scale. A practical estimation of the electromagnetic pressure, impact velocity and welded joint length as a function of the process conditions and the electromagnetic coil geometry is required but currently not available. Three novel analytical relations for the estimation of the electromagnetic pressure, impact velocity, and welded joint length for magnetic pulse welding of tubes and sheets, are presented. These relations were developed systematically, following a dimensional analysis, and validated for a wide range of conditions from independent literature. The comparison of the analytically computed results and the corresponding values reported in the literature has illustrated that the proposed analytical relations can be used for the estimation of the electromagnetic pressure and impact velocity for the magnetic pulse welding of tubes and sheets with a good level of confidence. The analytically calculated results for the welded joint length show a little discrepancy with the corresponding experimentally measured values. Further investigations and more experimentally measured results are required to arrive at a more comprehensive analytical relation for the prediction of welded joint length.

Magnetic-pulse welding of copper rings with steel parts using single-turn inductor

The Paton Welding Journal, 2022, №01. International Scientific-Technical and Production Journal «The Paton Welding Journal» «The Paton Welding Journal» has been published monthly since 2000 in English, ISSN 0957-798X. «The Paton Welding Journal» is a cover-to-cover English translation of the «Avtomaticheskaya Svarka» (Automatic Welding) journal. The «Avtomaticheskaya Svarka» journal has been published monthly since 1948 in Russian, ISSN 005-111X.

Effects of Discharge Current on Velocity of Moving Sheet and Joining Property in Welded Sheet Processed by Magnetic Pulse Welding

A systematic experiment was performed for four types of welding circuit with different circuit inductances and a common welding coil, where each circuit inductance is given by the sum of a different remaining inductance and a common effective inductance. It was demonstrated that increasing the circuit inductance causes adverse effects on the discharge current, resulting in a long first collision time and a low deformation velocity of the moving sheet. When the circuit inductance increases from 0.0587 μH to 0.2280 μH, the maximum current decreases from 223 kA to 132 kA at a discharge energy of 2.0 kJ. With the decrease in discharge current, the deformation velocity of the sheet decreases from 383 m∙s-1 to 164 m∙s-1. The higher the circuit inductance is, the lower the deformation velocity of the sheet is. With the lower velocity, the shearing load of the resulting welded sheet further decreases, ultimately leading to joining failure. However, in the circuit with a minimum inductance of 0.0587 μH, it is possible to weld an aluminum alloy sheet to a 1 GPa class high-strength steel sheet. It has been clarified that the decrease in circuit inductance improves the joining property of a welded sheet.

Magnetic Pulse Hybrid Joining of Polymer Composites to Metals

To lighten their vehicles, car manufacturers are inclined to substitute steel structures with aluminum alloys or composites parts. They are then faced with the constraints inherent to dissimilar (galvanized steel/aluminum) or hybrid (metal/composite) assemblies. Recent developments in magnetic pulse welding seems to offer a viable route. Very fast, this process can be robotized and generates a very localized heating system which limits the formation of intermetallic and damage the composite. Low energy consumption, without filler metal or smoke it is recognized as an environmentally friendly process. In this paper, electromagnetic pulse welding is exploited to assemble polymer composite to metals. Two techniques, a metallic insert in polymer composite or an external patch, have been tested with possible design considerations.

Interfacial microstructure and bonding mechanism of the Al/Ti joint by magnetic pulse welding

Magnetic pulse welding is performed to join Al/Ti dissimilar metals. A gradient structure composed of amorphous, nano-scale and ultrafine equiaxed grains is formed at the Al/Ti dissimilar metals joint interface. The formation of Al-Ti systematic amorphous is attributed to lattice collapse and super-diffusion resulted from high strain rate collision. Nano scale crystallization of amorphous is the result of limited time and energy input experienced by the materials located at the interface. Dynamic recrystallization is the main reason for the formation of ultrafine equiaxed grains at the Al side.

Improving the quality of Al-Fe tube joints manufactured via magnetic pulse welding using an inclined-wall field shaper

Due to the mismatched impact parameters between the velocity and the angle, a joint with an unbonded zone in the middle and the microdefects at the interface was fabricated by magnetic pulse welding (MPW). In this study, an oblique angle in the working zone was prefabricated to make an inclined-wall field shaper (FS) for MPW and thereby improve the quality of the joint. The effects of the span and size of the inclined wall on the impact parameters were evaluated by numerical simulations. With increasing span, the location where the maximum impact velocity occurred approached the free end of the joint. With increasing size of angle, the initial impact angle evidently increased. The microstructure indicated that the flat interface was changed into the wavy one, and the thick transition layer with microdefects could be removed using an inclined-wall FS. The double bonding zone was changed into the single one, which formed a continuous range with a length of above 3 mm where the impact parameters matched with each other. The length of the unbonded zone in the initial collision zone decreased from about 1 mm to 0.3 mm via using an inclined-wall FS with the span of 6.4 mm and the size of 5°. Shear test results showed that the zones with high strength were merged in the initial collision region. The maximum shear strength of about 81 MPa could be obtained using an inclined-wall FS with the size of 3° and the span of 6.4 mm, which was increased by 33% higher than that without an inclined wall.

Probing magnetic pulse welding of aluminium and steel sheets

Magnetic pulse welding is used to join overlapped thin sheets of dissimilar materials in solid state, which is not easy by fusion welding due to severe thermomechanical distortion and the formation of brittle intermetallic compounds. An intense electromagnetic pulse is employed that causes an impact between the overlapped parts leading to plastic deformation and rapid coalescence along the interface thereby posing a challenge to monitor the evolution of joint. An effort combining experimental investigation and numerical process modelling is presented here for a quantitative understanding of magnetic pulse welding of thin AA5754 and DC04 steel sheets with a flat linear coil of Cu-OFHC alloy. The numerical model couples an electromagnetic and a dynamic mechanical analysis to compute the transient electromagnetic pressure and the progressive impact between the parts and the plastic deformation that the parts experience for a given coil and sheet geometry and materials. The computed results of the impact velocity of the flyer on the target, the top and bottom part in the overlapped assembly, and the flyer–target contact length are examined against the corresponding experimentally measured results for several process conditions. The computed results are further used to elucidate the progressive nature of the evolution of the joint. Overall, the computational model has served as an important tool to uncover the underlying phenomena and identify suitable range of process conditions to produce a defect-free weld in magnetic pulse welding of sheets.

Effect of the post-weld heat treatment temperature on the mechanical properties and microstructure of magnetic pulse welded Al/Fe tubes

Post-weld heat treatment (PWHT) can improve the microstructure and properties of welded joints. Here, the effect of the PWHT temperature on the microstructure and mechanical properties of Al/Fe tube joints manufactured by magnetic pulse welding (MPW) was investigated systematically. The results indicated that PWHT improved the distribution of the chemical composition in the thick transition layer (thickness >10 μm), with only a slight change in thickness. In contrast, the thickness of the thin transition layer (thickness ≤10 μm) increased significantly upon increasing the temperature. Micropores, radial cracks, and axial cracks were repaired to different degrees below 250 °C, but axial cracks propagated in the axial direction when the temperature exceeded 250 °C. The local shear strength 3 mm from the free end reached about 58 MPa, which was almost two times greater than that without PWHT at 250 °C. Once this temperature was exceeded, the shear strength decreased; thus, the optimal PWHT temperature was 250 °C, at which the microstructure and mechanical properties were improved better.

Microstructure characteristics and mechanical properties of Al/Mg joints manufactured by magnetic pulse welding

The effective connection of 1050 Al and AZ31 Mg was realized by magnetic pulse welding. The maximum tensile-shear force of the dissimilar Al/Mg metal lap joint reached 97% of that of the 1050 Al alloy base material by optimizing the process parameters. The microstructure of dissimilar Al/Mg welded joints was analysed by Scanning Electron Microscope (SEM), Energy Dispersive Spectrometer (EDS) and Electron Backscattered Diffraction (EBSD). The results show that the key to obtaining high shear strength of Al/Mg dissimilar metal joints is mainly due to the following two reasons. On the one hand, grain refinement and element interdiffusion occur at the interface. On the other hand, no intermetallic compounds are formed at the interface.

Magnetic Pulse Welding of D9 Steel Tube to SS316LN End Plug

Magnetic Pulse Welding of D9 Steel Tube to SS316LN End Plug

Mechanical degradation of magnetic pulse welded Al–Fe joint in neutral salt environment

The urgent need in lightweight of vehicle body promoted the application of multi materials with high specific strength, and this involves the reliable welding of dissimilar materials. In this study, AA5052 aluminum alloy and HC420LA steel were welded by magnetic pulse welding. The mechanical degradation of the dissimilar Al–Fe joint after different salt spray corrosion duration was investigated. The atomic force microscopy-scanning Kelvin probe force microscopy (AFM-SKPFM) and immersion tests were also performed. The fracture of the Al–Fe joint was observed by optical microscopy, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The ultimate shear strength of the Al–Fe joint only declines for 10% after three weeks' corrosion. Crevice corrosion is found in the overlapping region, and galvanic corrosion and stress corrosion occur in the weld region. The corrosion in the flat welding interface is mainly galvanic corrosion due to the high corrosion driving force, while the corrosion in the wave welding interface is mainly stress corrosion.

Magnetic Pulse Welding Conditions for High-Tensile Steel of 1 GPa Class and 6061-T6 Aluminum Alloy Sheets

Magnetic Pulse Welding Conditions for High-Tensile Steel of 1 GPa Class and 6061-T6 Aluminum Alloy Sheets

Investigation of residual stresses in planar dissimilar magnetic pulse welds by neutron diffraction

Residual stresses are investigated for the first time in a dissimilar AA1050–DP450 steel magnetic pulse weld using neutron diffraction. Close to the joint interface, tensile residual stresses are observed in the Al sheet and compressive residual stresses are identified in the steel sheet. At the interface, longitudinal tensile stresses are dominant on the aluminum side and transverse and normal stresses show similar behavior. On the steel side, normal stresses remain small, and longitudinal and transverse residual stresses have a similar trend. It was identified that close to this tensile region in aluminum, residual stresses in steel become more compressive. These residual stress distributions essentially result from (i) the respective yield strengths of Al and steel and (ii) the high strains and high strain rates borne by both alloys due to the impact of the Al flyer sheet on the steel sheet during the process. The asymmetrical shape of the rectangular joint line entailed a lower magnitude of residual stresses along the short side of the weld.

Joining of aluminum alloy and dissimilar metal material by magnetic pulse welding～Joining conditions for magnetic pulse welding～

Joining of aluminum alloy and dissimilar metal material by magnetic pulse welding～Joining conditions for magnetic pulse welding～

Experimental and Numerical Investigations into Magnetic Pulse Welding of Aluminum Alloy 6016 to Hardened Steel 22MnB5

By means of magnetic pulse welding (MPW), high-quality joints can be produced without some of the disadvantages of conventional welding, such as thermal softening, distortion, and other undesired temperature-induced effects. However, the range of materials that have successfully been joined by MPW is mainly limited to comparatively soft materials such as copper or aluminum. This paper presents an extensive experimental study leading to a process window for the successful MPW of aluminum alloy 6016 (AA6016) to hardened 22MnB5 steel sheets. This window is defined by the impact velocity and impact angle of the AA6016 flyer. These parameters, which are significantly dependent on the initial gap between flyer and target, the charging energy of the pulse power generator, and the lateral position of the flyer in relation to the inductor, were determined by a macroscopic coupled multiphysics simulation in LS-DYNA. The welded samples were mechanically characterized by lap shear tests. Furthermore, the bonding zone was analyzed by optical and scanning electron microscopy including energy-dispersive X-ray spectroscopy as well as nanoindentation. It was found that the samples exhibited a wavy interface and a transition zone consisting of Al-rich intermetallic phases. Samples with comparatively thin and therefore crack-free transition zones showed a 45% higher shear tensile strength resulting in failure in the aluminum base material.

Influence of Material Properties on Interfacial Morphology during Magnetic Pulse Welding of Al1100 to Copper Alloys and Commercially Pure Titanium

During magnetic pulsed welding (MPW), a wavy interface pattern can be observed. However, this depends on the specific material combination being joined. Some combinations, e.g., steel to aluminum, simply provide undulating waves, while others, e.g., titanium to copper, provide elegant vortices. These physical features can affect the strength of the joint produced, and thus a more comprehensive understanding of the material combination effects during MPW is required. To investigate the interfacial morphology and parent material properties dependency during MPW, tubular Al1100 and various copper alloy joints were fabricated. The influence of two material properties, i.e., yield strength and density, were studied, and the interface morphology features were visually investigated. Results showed that both material properties affected the interface morphology. Explicitly, decreasing yield strength (Cu101 and Cu110) led to a wavy interface, and decreasing density (Cu110 and CP-Ti) resulted in a wave interface with a larger wavelength. Numerical analyses were also conducted in LS-DYNA and validated the interface morphologies observed experimentally. These simulations show that the effect on shear stresses in the material is the cause of the interface morphology variations obtained. The results from this research provide a better fundamental understanding of MPW phenomena with respect to the effect of material properties and thus how to design an effective MPW application.

Influence of Copper Interlayers on the Magnetic Pulse Welding Process between Aluminum and Steel

Magnetic pulse welding (MPW) is a promising joining technology for the large-scale production of dissimilar metallic joints. Although the heat input is comparatively low, the temporary occurrence of high temperatures in the joining gap was found to play an important role during the joint formation. It is possible that the melting or even the boiling temperature of the involved materials will be exceeded, and fusion welding will occur. The purpose of this study is to investigate the influence of target materials with different thermal properties on the joint formation and weld seam characteristic. Therefore, MPW between steel targets and aluminum flyers was performed with and without copper coatings on steel. The lower melting temperature of copper compared to steel had no significant effect on the appearance of the mixed zones in the interface and the amount of molten target material or aluminum, respectively. Nevertheless, the comparison of the higher impact energies showed, that the copper interlayer can lead to a decrease in the weld length or a degradation of the weld quality due to an extended intermetallic phase formation or cracks. This result is important for the parameter adjustment of magnetic pulse welding processes.

Experimental investigation and optimization on field shaper structure parameters in magnetic pulse welding

Magnetic pulse welding is a high-speed welding technology, which is suitable for welding light metal materials. In the magnetic pulse welding system, the field shaper can increase the service life of the coil and contribute to concentrating the magnetic field in the welding area. Therefore, optimizing the structure of the field shaper can effectively improve the efficiency of the system. This paper analyzed the influence of cross-sectional shape and inner angle of the field shaper on the ability of concentrating magnetic field via COMSOL software. The structural strength of various field shapers was also analyzed in ABAQUS. Simulation results show that the inner edge of the field shaper directly affects the deformation and welding effect of the tube. So, a new shape of field shaper was proposed and the experimental results prove that the new field shaper has better performance than the conventional field shaper.

On the complete interface development of Al/Cu magnetic pulse welding via experimental characterizations and multiphysics numerical simulations

A complex Al/Cu magnetic pulse welding interface is systematically investigated using experimental characterizations and numerical simulations. A Coupled electromagnetic-mechanical simulation is proposed to compute the impact velocity and impact angle along the entire interface. This model allows to further understand the formation mechanism of various interface characteristics during MPW. The results revealed that the impact velocity gradually decreases in conjunction with the gradual increase of the impact angle. These simulations elucidate the experimentally observed successive interface morphologies, i.e., the unwelded zone, vortex zone, intermediate (IM) layers and wavy interface. Microstructural characterizations show that the IM layers are formed by mechanical mixing combined with melting and are characterized by highly heterogeneous porous zone with random sizes and distributions of void. Subsequently, an Eulerian simulation is proposed to investigate the thermomechanical effects during the wave formation which vastly influence the joint quality. The predicted wavy morphologies, temperature distribution and average equivalent plastic strain along the interface provided a better understanding on the formation steps of the experimentally observed wave morphologies. The actual kinematics during wave generation revealed that the wave was formed with repeated deformation of the interface material. The wave amplitude increases with increasing jetting angle; while the wavelength increases with increasing collision point velocity. The ratio between collision point velocity and impact velocity is found to be the most suitable parameter for explaining the influence of the collision parameters on the wavelength. These results indicate that the combination of the Coupled electromagnetic-mechanical simulation and Eulerian simulation can help us investigate the governing mechanisms of complex interface morphologies and further used to optimize the processing parameters during high speed impact welding.

Magnetic pulse welding of aluminum to steel tubes using a field-shaper with multiple seams

A field-shaper is a device that can significantly improve the efficiency of a magnetic pulse welding process. There is usually a seam to change the direction of the induced current in the field-shaper. However, this seam causes the electromagnetic force to be unevenly distributed in the circumferential direction, and it is difficult to weld near it. To improve the uniformity of magnetic pulse welding, a novel multi-seam field-shaper is investigated in this paper. Both numerical simulation and experimental study are carried out. The effects of the number of seams, the length of the seams, and the discharge voltage on the welding performance of a magnetic pulse tube are studied. In this work, when the number of seams in the field-shaper is four, and the length of the short seam is 16 mm, the field-shaper facilitates a uniform circumferential distribution of the electromagnetic force. The measurements and simulation of free tube-compression and tube-welding are performed using a multi-seam field-shaper. The results show that a magnetic pulse welding system with a multi-seam field-shaper can significantly improve the circular deformation uniformity of a 5052 aluminum-alloy tube.