It is also a solid-state welding process, which means that the materials do not melt during the creation of a bond, which provides the opportunity to join dissimilar materials. With this process, it is possible to join tubular products as well as sheet materials, depending on the coil which is used.
Joining of conventionally non-weldable materials, in a quick and cost-effective manner, such as dissimilar material joints. Development of complex workpieces or new products, which were previously not possible with the conventional joining processes.
Contact-free: no marks of forming tools and processing of coated or sensitive materials is possible.
There is no heat, radiation, gas or smoke, shielding gas, which is less harmful for the operator. In hostile environments machines can perform the joining operation, avoiding supplementary investments in operator safety.
It is possible to improve the work conditions of the welder or operator, since the technology is environmentally clean. One workpiece has to withstand the impact of the other, so it is possible that a mandrel or support is required to prevent deformation. The Belgian Welding Institute has acquired large experience with the electromagnetic pulse welding process.
If there is sufficient industrial interest, BWI wants to further investigate this very innovative welding process and to demonstrate its potential benefits for the industry. Science, Technology and Medicine open access publisher.Publish, read and share novel research. Welding of Magnesium AlloysParviz Asadi1, Kamel Kazemi?Choobi2 and Amin Elhami3[1] School of Mechanical Engineering, College of Engineering, University of Tehran, Tehran, Iran[2] Research Center for Advanced Materials and Mineral Processing, Faculty of Materials Engineering, Sahand University of Technology, Tabriz, Iran[3] Department of Mechanical Engineering, Tehran Central Branch, Islamic Azad University, Tehran, Iran1. The weld is stronger than the weakest base material : during material testing the crack appears outside the weld area. It is an ecological welding process, since no heat, radiation, gas or welding fumes are produced. Nowadays, due to the increasing international competition, companies need faster and more economic production techniques and are forced to decrease the production costs to remain competitive.
Very little objective knowledge is available concerning the technical feasibility of the use of these processes for relevant industrial applications, nor concerning the possible increase of productivity or the weld quality, and therefore concerning the economic advantages that the use of these innovative processes can lead to. The research centre of Belgian Welding Institute has investigated this welding technique and has demonstrated the potential advantages for the industry.
These processes allow to join a wide variety of materials in a fast, error-free and therefore more cost-effective manner.
Contributed by the Manufacturing Engineering Division of ASME for publication in the JOURNAL OF MANUFACTURING SCIENCE AND ENGINEERING. This paper investigated the effect of magnetic pulse welding (MPW) condition (welding power, surface scratches, and contamination) on the establishment of welding between aluminum and copper tubes, and the associated welding mechanisms. As the only turntable belt and phonograph specialist with the most extensive selection of turntable belts, we supply replacement belts designed for specific turntables. This joining technology makes use of electromagnetic forces for deformation and joining of workpieces. The discharge current induces a strong transient magnetic field in the coil, which generates a magnetic pressure, which causes one workpiece to impact with another workpiece.
The explosive deformation force is however created in a safe way, by using electromagnetic forces generated by an induction coil.
From the point of view of the potential applications, which are mostly factory-made parts, this is not necessarily a disadvantage. The previous projects were focused on the application of the process for joining tubular applications. Welding con?guration (a) with a shroud gas feed tube and (b) in a gas box (Zhu et al., 2005). Diagrams of fiber laser welding system and experimental arrangement, (a) IPG fiber laser installed on a KUKA robot, (b) welding head (Wang et al., 2011). Optical micrographs showing (a) microstructure near the interface between the FZ and HAZ for a ZE41A-T5 alloy joint and (b) close-up view of Fig. Schematic diagram showing the initial impact and flattening of the sheets during MPW (Berlin, 2011).7. IntroductionMagnesium is the sixth most abundant element on the Earth’s surface, with virtually inexhaustible supplies in the oceans. The working principle of the welding process is based on the use of electromagnetic forces to deform and to weld workpieces. Therefore no heat affected zone is created, and no loss of material properties takes place.
The largest impact can be expected of a productivity increase by using new innovative production techniques. By participation in this research project, companies got an insight in the possibilities of these new processes. The results showed that higher applied power and surface scratches in tangential direction were in favor for good weld, and oil on the surface prevented welding.
We do not force fit a generic or OEM belt and size to a turntable—sadly a very common practice today.
This process also offers the possibility to join dissimilar materials, which are difficult to weld using the conventional welding processes. This means that after welding, parts can immediately be unloaded and further processed with standard equipment. Electromagnetic pulse welding of sheet materials, which currently receives more and more attention, is considered as quite promising, due to the many advantages this process offers. It is the third most plentiful element dissolved in seawater, with an approximate concentration of 0.14% (Busk, 1987).
Since this sophisticated welding process doesn't use heat to realise the weld, it offers important advantages with regard to the conventional welding techniques! A large amount of energy is compressed and discharged in an extremely short period of time. This also means that the welded workpieces can be unclamped immediately after welding and can be further processed immediately.
Over recent years the industrial output of magnesium alloys has been rising by almost 20% per annum. CuAl intermetallics with different atomic ratios were identified by energy dispersion spectrum (EDS) chemical analysis and by microscratching test. Combination of diffusion bonding with superplastic forming which is used for superplastic wrought AZ31. Magnesium and its alloys, as the lightest structural material, are about 40% lighter than aluminium and as much as about 78% lighter than steel. Also other dissimilar and similar metals that have been welded successfully (see table below). This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. It is demonstrated that using magnesium alloys results in a 22–70% weight reduction, compared to using alternative materials (Kulekci, 2008). Both currents (in the coil and in the external workpiece) induce magnetic fields, which oppose each other. The reaction forces between the opposing magnetic fields are forcing the external part towards the internal part at high velocity to cause welding.
For achieving the successful weldment and using this process, the design of working coil is the most important factor, because working coil has to generate a high-intensity magnetic field on the surface of the workpiece during the process. Therefore, the objective of this study is to analyze the distribution of electromagnetic force of square working coil for magnetic pulse welding. Additionally, these alloys have limited fatigue and creep resistance at elevated temperatures (Mordike and Ebert, 2001). For this, FE-model has been developed to analyze the distribution of electromagnetic force; after that, distribution of electromagnetic force, results of numerical analysis and experimental results for verifying the developed FE-model were compared. Because of the hexagonal close-packed (HCP) crystal structure, magnesium alloys also have a limited ductility and cold workability at room temperature (Sanders et al., 1999). These alloys have about the same corrosion resistance in common environments as mild steel, but are less corrosion resistant than aluminium alloys (Busk, 1987). The shape and material of square working coil were decided through literature surveys.
Thus, magnesium alloy usage has been limited due to its poor corrosion resistance and low ductility. For the experiment, an MPW equipment W-MPW manufactured by WELDMATE Co., Ltd. In order to overcome these problems, new alloys, such as Mg-AZ91D, have been developed and have improved corrosion resistance (Munitz et al., 2001). The property pro?les demanded by automobile and other large-scale potential users of magnesium have revealed the need for alloy development. After the experiment, leakage test was used to verify the weldability. Also weld joints were observed on longitudinal cross-section by microscope. The electromagnetic force generated was the greatest one at the center adjacent to square working coil, decreasing as moving into the edge. These results are similar to the output data from developed electromagnetic FE-model where electromagnetic force decreases as moving into the corners of square working coil. It is also common to classify magnesium alloys into those for room and elevated temperature applications. Aluminium and zinc, added either singly or in combination, are the most common alloying elements for room temperature applications because at elevated temperatures the tensile and creep properties degrade rapidly (Marya et al. The two or one letter is followed by numbers which represent the nominal compositions of these principal alloying elements in weight percentage, rounded off to the nearest whole number. Despite the good castability of some mentioned alloys (such as Mg-AZ91D alloys), it is not always possible or economically favourable to cast complex magnesium parts.
Joining of magnesium parts, which may be crucial for these applications, is still restricted.
It is, thus, very desirable that joining technologies be developed and made accessible for industrial applications (American Society of Metals [ASM], 1990).Welding and joining processes are essential for the development of practically every manufactured product.
However, these processes often appear to consume greater fractions of the product cost and to create more of the production difficulties than might be expected (ASM, 1993). Because there are many fusion welding processes, one of the greatest difficulties for the manufacturing engineer is to define which process will produce satisfactory properties at the lowest cost. Any change in the part geometry, material, value of the end product, or size of the production run, as well as the availability of joining equipment, can influence the choice of joining method. Magnesium alloy components may be joined using mechanical clasps as well as a variation of welding methods including tungsten arc inert gas (TIG), plasma arc welding, electron beam welding (EBW), laser beam welding (LBW), friction stir welding (FSW), explosion, electromagnetic welding, ultrasonic welding, and resistance spot welding (RSW).2. Introduction The car industry is currently working to accommodate the conflicting requirements of both environmental legislation and customer demands for high performance and safety by developing a light-weight vehicle [1]. So the light weight materials such as aluminum and magnesium have been applied in automation.


Especially, development of aluminum space frame for automotive body structure has been carried out in recent years [2].
However, when only light materials are used in automotive body structure, they cannot satisfy the required intensity and strong property, and it is imperative to weld light weight materials with existing used ones. The effectiveness of laser welding depends greatly on the physical properties of the material to be welded. Accordingly, it has been required to study on welding of dissimilar metals [1] due to the different physical properties between materials. Magnesium alloys possess certain inherent characteristics such as low absorptivity of laser beams, strong tendency to oxidize, high thermal conductivity, high coef?cient of thermal expansion, low melting and boiling temperatures, wide solidi?cation temperature range, high solidi?cation shrinkage, form low melting point constituents, low viscosity, low surface tensions, high solubility for hydrogen in the liquid state, and absence of colour change at the melting point temperature.
Welding as existing fusion welding generally causes not only defects, such as solidification, cracking, porosity and oxidation, but also transformation and corrosion. Therefore, some processing problems and weld defects can be observed in laser welding of magnesium alloys such as unstable weld pool, substantial spatter (Haferkamp et al., 2001), strong tendency to drop through for large weld pools, sag of the weld pool (especially for thick workpiece), undercut (Lehner and Reinhart, 1999), porous oxide inclusions, loss of alloying elements, excessive pore formation (particularly for die castings) (Zhao and DebRoy, 2001), liquation and solidi?cation cracking (Marya and Edwards, 2000). For this reason, more attention has been paid to magnetic pulse welding process as a kind of solid-state welding these days. CO2 and Nd:YAG lasersLasers have been promoted as potentially useful welding tools for a variety of applications.
The electrical energy stored in the magnetic pulse power source is discharged instantaneously as a high current to the working coil by a trigger discharge, and thus an induced current is generated at the conductive outer workpiece positioned within the working coil.
The availability of high-power continuous-wave (CW) carbon dioxide (CO2) and neodymium-doped yttrium aluminium garnet (Nd:YAG) lasers and the limitations of current welding technology have promoted interest in deep-penetration welding in the past twenty years using these devices.
For successful magnetic pulse welding, it is important to develop a working coil that can gain enough electromagnetic force for welding.
The weldability of magnesium alloys was reported to be signi?cantly better with the Nd:YAG laser due to its shorter wave length. Leong investigated welding AZ31 alloy using both CO2 and pulsed Nd:YAG laser, and illustrated the dif?culties of CO2 welding.
The extensive knowledge in this complicated area is not easily obtained, as the variety of experimental setups and the complicated dynamic interaction between different phenomena in the welding process are extremely difficult to describe in a closed analytical form. He concluded that Nd:YAG laser was more suitable for magnesium alloy welding (Leong, 1998). Laser powerThe penetration depth with laser welding is directly related to the power density of the laser beam and is a function of incident beam power and beam diameter. For a constant beam diameter, penetration typically increases as the beam power is increased.
It is well known that high power density at the workpiece is crucial to obtain keyhole welding and to control the formation of welds.
Lower irradiance incident upon the workpiece would reduce the spatter as well as the loss of high vapour pressure constituents. It is reported that lower power level and slower speed lead to better weld quality (Cao et al., 2006). A loss of tensile strength was found with Nd:YAG laser power lower than 2kW (Lehner and Reinhart, 1999).
Welding speedThe effects of welding speed on penetration depth and weld width at different levels of power for CO2 and Nd:YAG lasers are shown in Fig. It can be seen that the penetration depth and weld width both decrease linearly with increasing welding speed. Consequently, the objective of this research is to develop FEmodel for square working coil in magnetic pulse welding which is a basic research for manufacturing the automotive space frame.
For this study, first, the shape and material of coil were decided through literature survey. Though similar welding parameters are used, various magnesium alloys exhibit different welding performance due to their different thermo-physical properties.
The comparison between the calculated and measured results was finally done to verify the developed electromagnetic FE-model. Because of the difference in their thermal properties, much more studies, therefore, is needed to systematically investigate the laser welding characteristics of different magnesium alloys.When the laser energy input was more than that required for a full penetration, large holes or weld dropout could be observed. This could be due to the long interaction time or the higher power density, while the low viscosity liquid is not able to sustain the welding pool.
The ripple phenomenon has been associated with growth rate fluctuations due to the effects of surface tension of the weld pool during solidification. 7 shows the crown increased rapidly with increasing the welding speed and decreasing the beam power. Shielding gasIt is well known that magnesium is highly susceptible to oxidation and thereby elaborate protection from the atmosphere is required (Dilthey et al., 1998). Good shielding can prevent burning or porosity and protect the laser optics from metal slag. Helium, with a high ionization potential of 24.5 eV and good thermal conductivity, has a high plasma formation threshold.
Development of Square Working Coil 2.1. To identify the best shielding gas, blind welds of AZ91 alloy were produced using helium, argon and nitrogen (Yu et al., 2009). Magnetic Pulse Welding The magnetic pulse welding is a solid-state, cold-welding process that is accomplished when a magnetic pulse causing a high-velocity impact between two materials, resulting in a true metallurgical bond [8].
The principle of magnetic pulse welding is based on the physical phenomena of magnetic fields induced by an electric current [9]. A comparative study of two kinds of inert shielding gases He and Ar for laser welding process showed that He gas possesses a better shielding effect for the laser generated magnesium alloy pool than Ar gas, because of its higher dissociation energy and better conductivity (Dhahri et al., 2001b). It is well known that two conductors with their electric currents travelling in opposite direction repels due to the interaction of their oppositely orientated magnetic fields induced. For CO2 laser welding process, the satisfied seams with smooth surface, deep penetration depth, large ratio of weld depth to weld width and high weld strength, could only be produced under the protection environment of much more expensive He gas.
Figure 1 shows in the initial coil, the inductor, a current impulse which in turn, generates a current of the opposite direction in the outer workpiece. In contrast, for the YAG laser welding process, sound seams could be readily obtained under the protective environment of much cheaper Ar gas. A electromagnetic force to the initial coil causes the outer workpiece to impact at a tremendous force and speed at the inner workpiece, resembling an explosion taking about 20 millionths of a second [7]. It can be concluded that YAG laser is the first choice for the laser welding of magnesium alloys considering weld quality and economic factors (Dhahri et al., 2001b). It was found that the shielding gas con?guration could have a signi?cant effect on the weld quality. To generate the high-current impulse an arrangement of capacitors, an arrestor-discharge and a working coil has been constituted the core of the magnetic pulse module, as shown in Figure 2 [10,11].
When the gas from the feed tube above the weld is not aligned with the traverse direction, a side cut would occur as shown in Fig. The capacitors, special high-voltage capacitors with extremely low self-inductance, can store charge up to a certain maximum level that is determined by the arrestor-discharge, which creates a short, highcurrent pulse in the work coil [6].
Fiber laserFiber laser, as the third generation of industrial laser, is rapidly developing in recent years due to a number of advantages such as compact size, long transmission distance, high efficiency, superior beam quality and high power output (peak output is up to 50 kW).
In the fields of joining steel and aluminium alloys, fiber laser has made a big progress in experimental studies and industrial applications, showing a great potential to replace conventional Nd:YAG and CO2 lasers. It is reported that the UTS of the joint decreases, but the yield strength increases after fiber laser welding of fine-grained magnesium alloy (Yu et al., 2009). On the other hand, laser power plays a big role in the characterization of fiber laser welding of AZ31B magnesium alloy. The principle of the magnetic pulse welding process [7].
If the alloy is in a fully tempered state, the loss of precipitates may lead to the HAZ overaged. If the alloy is susceptible to grain growth, the grains will grow in the HAZ which leads to decrease in mechanical properties (Cao et al., 2006). A signi?cant grain coarsening can be observed in the HAZ in wrought AZ31 alloy, however, in all laser welded cast alloys, no grain coarsening occurs within the HAZ zone. PorosityThe presence of porosity in the weld is one of the major concerns during laser beam welding of magnesium alloys. The high porosity is also one of the most important factors to reduce the failure strength of welded joints undergoing higher heat input, even though their grain size in the FZ is similar to or even smaller than that of the base metal (Wang et al., 2011).
During the tensile test, because of stress concentration around the porosities, the micro-crakes usually initiate from these weakest positions, and then propagate to fracture the joints (Zhao and Debroy, 2001). Magnesium has significantly high solubility for hydrogen in the liquid phase and the porosity in magnesium alloys is dependent on the amount of dissolved hydrogen (Stolbov et al., 1990).
The tolerable hydrogen gas content in welds may depend on a number of factors such as the parameters of the welding process, alloy composition, local solidi?cation time, thermal gradient, weld structure, and inclusion concentration (Cao et al., 2006).
However, no acceptable hydrogen content limits have ever been reported for laser welded joints of magnesium alloys.
It was recognized that the porosity in fiber laser welds of AM60, AE42 and AS41 cast magnesium alloys was mainly caused by the growth of the initial pre-existing pores. Imperfect collapse of the keyhole and turbulent ?ow in the weld pool could also been linked with porosity formation. Thus, decreasing heat input is effective to reduce the porosity in fiber laser welds of magnesium alloys. 14a hydrogen porosity is the dominant pore in laser welded die-cast magnesium alloys because of their extremely high initial gas contents. Clearly, production of weldable and heat treatable die-castings necessitates the reduction of gas contents in magnesium alloys (Cao et al., 2006). It is proposed that well-controlled remelting of the FZ leads to removal of gas bubbles and reduced porosity in the FZ. When die cast magnesium alloys remelt during laser beam welding, the gas can be enlarge due to heating (thermal expansion) and thus leading to the release of the gas pressure.
Finally, the growth of porosity leads to expansion and coalescence of the pores, causing the formation of large pores in the fusion zone as shown in Fig. In most magnesium alloys, an increase in alloying elements will generally increase the solidi?cation temperature range. Shape and Material As I mentioned before, magnetic pulse welding uses the electromagnetic force from current discharged through the working coil which develops a repulsive force between the induced currents flowing parallel and in the opposite direction in the workpice to be welded. The large freezing temperature range, large solidi?cation shrinkage, high coefficient of thermal expansion, and low melting point intermetallic constituents potentially make magnesium alloys susceptible to heat affected zone liquation cracking and solidi?cation cracking in FZs (Marya and Edwards, 2002). However, the theoretical analysis for development of perfected working coils considering various factors hasn’t been established yet. In addition, a number of magnesium alloys are thought to be susceptible to stress corrosion cracking.
Nevertheless generally the considered factors were classified into a shape and an electric property [10]. The susceptibility to solidi?cation cracking is evaluated using the circular-patch-weldability test and operating windows of welding parameters are identi?ed (Lathabai et al., 2003). Second, distribution an electromagnetic force by the interaction between working coil and outer pipe should be investigated after selecting materials that electric resistance is low and that has enough intensity mass possible to resist electromagnetic force on processing. The alloys containing up to 6% Al and up to 1% Zn possess good weldability, while the alloys containing over 6% Al and up to 1% Zn are moderately crack sensitive, because of the occurrence of low melting-point constituents (Mg17Al12).


Even without Al, the alloys containing over 3% Zn are highly susceptible to solidi?cation cracking and dif?cult to weld (Marya et al., 2000). On the other hand, hot tearing is mainly in?uenced by joint composition, microstructure, welding process parameters, and joint design.
A compression coil is the solenoid type surrounding processed materials which is welded from outside direction to inside.
Oxidation of magnesium is increased at high temperatures, resulting in the formation of a surface magnesium oxide layer (Cao et al., 2006). The amorphous structure of MgO ?lms in solid pure magnesium generally performs an important role as a protective layer to prevent further oxidation at low temperature, but the ?lms easily become porous and loose with the temperature increase. It is reported that the addition of Ca to the pure Mg as well as the addition of Al and Y to the Mg–Ca alloys can further improve oxidation resistance.
The entrapment of surface oxides into the molten pool during welding is an important source for oxide inclusions in laser welded magnesium alloys.
A plate coil which located on and under the processed material was employed in plate welding [3]. Therefore, the shape of solenoid-typed compression coil was chosen between compression coil and expansion one that are used in joining of pipes because it is located in the outside of the specimens. In addition it has no size limit as well as simple connection magnetic pulse power source.
Loss of alloying elementsThe relatively high vapour pressure of liquid magnesium compared with aluminium points to the potential problem of evaporative losses, particularly if zinc is also present as an alloying addition. The evaporation will cause a variation of chemical composition in the FZ, especially at high laser power density. Minimizing the irradiance incident upon the workpiece would decrease the loss of high vapour pressure elements (ASM, 1993).
Further work is needed to fully understand the main influencing factors to build up the quantitative relationship between the element loss of evaporation and welding process parameters.3.
Gas tungsten arc weldingGas-Tungsten Arc Welding (GTAW), also known as HeliArc, Tungsten Inert Gas (TIG), and tungsten arc welding, was developed in the late 1930s when a need to weld magnesium became apparent. Russell Meredith developed a welding process using the inert gas helium and a tungsten electrode to fuse magnesium.
TIG welding is used extensively for welding stainless steel, aluminium, magnesium, copper, and reactive materials (for example, titanium and tantalum).
This joining method replaced riveting as a method of building aircraft with aluminium and magnesium components (ASM, 1993). This process uses the heat, generated by an electric arc struck between a non-consumable tungsten electrode and the workpiece, to fuse metal in the joint area, and produce a molten weld pool.
The arc area is shrouded in an inert or reducing gas shield to protect the weld pool and the non-consuming electrode. The process may be operated autogenously (without filler), or filler may be added by feeding a consumable wire or rod into the established weld pool. For direct current (DC) operation, the tungsten may be connected to either output terminal, but is most often connected to the negative pole.
Shielding gas is directed into the arc area by the welding torch, and a gas lens within the torch distributes the shielding gas evenly over the weld area.
Welding currentCurrent is one of the most important process parameters to control in any welding operation, because it affects the penetration depth, welding speed, deposition rate, and weld quality. Shielding gasesThe preferred gas for the AC-TIG welding of magnesium is argon, although helium and argon–helium mixtures may be used. Argon gives a wide, shallow penetration weld bead, but will leave the weld bright and silvery in appearance.
Analysis Method and Procedure After shape and material of coil was chosen, electromagnetic force needed to welding should be confirmed. However, there is a limitation for electromagnetic force Table 1.
For transition metal alloys, when the welding path is coated with chemical fluxes, a technique exists of flux-assisted gas tungsten arc welding (FA-TIG).
Generally, fluxes allow full penetration welding at greater rates using relatively inexpensive gas tungsten arc as the heat source.
Using argon shielding and chloride fluxes, magnesium alloy welding tests showed an increase in weld penetration (Marya and Edward, 2002).
Resistance spot weldingResistance spot welding is the localized joining of two or more metal parts together by the heat, generated using resistance to the flow of electric current through workpieces, which are held together under force by electrodes.
The contacting surfaces in the region of current concentration are heated by a short-time pulse of low-voltage and high-amperage current. When the flow of current ceases, the electrode force is maintained till the weld metal cools down and solidifies. The electrodes are retracted after each weld, which usually is completed in a fraction of a second. RSW can be separated into Silicon Controlled Rectifier (SCR) AC resistance welding and inverter DC resistance welding (Hwang et al., 2010). For high electrical conductivity of magnesium and low heat generation in the weld, high welding currents are required.
Weld microstructureThe joint, achieved by a technique of resistance spot welding, consists of the weld nugget and the heat affected zone.
The weld nugget consists of the cellular dendritic structure at nugget edge, accompanied by equiaxed dendritic structure within its centre for AZ31 alloy (Fig.
Effect of welding parameters on joint propertiesAs weld current increases, the nugget width increases as well. Because this force is decided by interactions of electromagnetic and workpiece model development of numerical analysis can be a useful means. This effect is proved for both SCR AC resistance welding and inverter DC resistance welding which is shown in Table 1. In both RSW welding technics cracks and pores have been found, affecting the properties of weld.
In the case of magnesium alloys, the welding part rapidly expands and retracts during welding and quickly cooling down, because of high coefficient of linear expansion.
The magnetic field of the workpiece is expressed from Equations (2) to (5). To these differential relations, the constitutive relations are included from Equations (6) and (7). When a high frequency current flows through a conductor, the current tends to flow on the conductor surface. The magnitude of the current is exponentially decreased with the depth of penetration into the conductor. Figure 4 shows a schematic diagram for magnetic pulse welding this study. Table 2 shows the material properties for working coil and outer pipe. Current was inputted into the working coil as a sine wave function. Not only the magnitude was 500 kA a, but also the frequency was 25 kHz for the experiment. To avoid the calculation complexity of energy transformation, current was employed as the excitation in the present analysis.
Results and Discussion Figure 5 shows distributions of the magnetic flux density of the square working coil. Magnetic flux is increased at the upper part of a coil and concentrated in adjacent corner of coil.
Especially, Figure 6(c) indicates the distribution of the electromagnetic force of inside square coil. The maximum electromagnetic force generated in coil is about 951 N and in the edge about 503 N was measured. When interaction between a square coil and Al pipe is being processed, the collision of Al pipe is caused because the electromagnetic force acts from surface to inside of the Al pipe. These phenomena occurred because current is accumulated in the corner of the square coil compared with the solenoid coil at discharging of current.
Setup and Procedure To test for the developed working coil efficiency test, as show in Figure 7, the experimental employed in this study is a W-MPW manufactured by WELMATE CO., LTD. After experimenting, the (a)(b)(c) Figure 6.
In addition, ultrasonic cleansing was carried out for approximately 10 minutes within acetone in order to remove grease. And then the weldment was observed by microscopic on circumferential cross section. Results and Discussion Figure 9 shows the measured waveform while discharging the energy charged in working coil. The sin-waveform of decreasing vibration was recorded and it took about 25 us to peak current needed to welding. The weldment and section of welded part were presented at Figure 10.
These results are similar to the output data from electromagnetic model that electromagnetic force decreases as moving into the corners as shown Figure 6. The maximum electromagnetic force generated in coil is about 951 N and in the edge about 503 N was measured. The generated electromagnetic force is the greatest at the centre adjacent to coil, decreasing as moving into the edge. Park, “Design of Joints for the Automotive Space frame with Electromagnetic Forming and Adhesive Bonding,” Ph.D.
Thesis, Graduate School of the Seoul National University, Seoul, 2004 K. Kobayashi, “Production and Fabrication Technology Development of Aluminium Useful for Automobile Lightweights,” Advanced Engineering Materials, Vol. Yang, “Numerical Simulation of the Magnetic Pressure in tube Electromagnetic Bulging,” Journal of Materials Processing Technology, Vol. Sato, “High-Speed Forming of Metal Sheets by Electromagnetic Force,” JSME International Journal, Vol. Kapoor, “Modeling of the Electromagnetic Forming of Sheet Metals: State of the Art and Future Need,” JSME International Journal, Vol. Barber “Magnetic Pulse Welding of Tubing: Exploring the Cold Welding Process,” Fabricator, Vol. Daehn, “Modeling of Electromagnetically Formed Sheet Metal,” Journal of Materials Processing Technology, Vol.



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