Abstract
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.
Highlights
Technical structures often consist of dissimilar metals, in order to meet for example, lightweight requirements, take advantage of special material properties and enable cost reduction by replacement of an expensive material
There are certain strategies to accelerate the first workpiece called “flyer” up to several hundred meters per second and arrange the collision with the fixed workpiece called “parent.” The pressure can be generated by Lorentz forces that act between a coil and the workpiece, the detonation of an explosive, the vaporization of foils, or pulsed lasers
The identification of suitable welding parameters and the inline quality assurance are difficult to realize due to the process durations in the range of a few microseconds, the intense magnetic fields and the destructive forces that occur in the vicinity of the impact zone and that act on any sensors located there
Summary
Technical structures often consist of dissimilar metals, in order to meet for example, lightweight requirements, take advantage of special material properties and enable cost reduction by replacement of an expensive material. The heat input and the IMP formation, respectively, can be reduced significantly, enabling the production of durable joints. MPW is suitable for smaller structures with wall thicknesses of the order of some millimeters. It requires a sufficient electrical conductivity of the flyer to induce eddy currents and build up the magnetic pressure. If these boundary conditions are fulfilled, the process is predestined for the line production of dissimilar metal joints with a good repeatability. Conclusions are drawn regarding the applicability of the presented methods
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