Joining of Dissimilar Materials Using the Electromagnetic Pulse Technology

Joining of dissimilar materials using the electromagnetic pulse technology

The electromagnetic pulse technology uses magnetic forces to deform or join workpieces. The energy stored in a capacitor bank is discharged rapidly through a magnetic coil (figure 1). A ring-shaped coil is placed over a tubular workpiece. The magnetic field produced by the coil generates eddy currents in the tube. These currents, in turn, produce their own magnetic field. These two opposing magnetic fields result in a repelling force between the coil and the tube. As a consequence, the tube collapses onto the internal workpiece, creating a joint. Under precisely controlled conditions a solid-state weld can be realised.

Solid-state welding processes like electromagnetic pulse welding provide the possibility to weld dissimilar materials. In order to evaluate the feasibility of the process for industrial applications, the weldability of several material combinations was investigated (see figures 2 and 3). Welding experiments were performed with tubes with a diameter of 25 and 45 mm and with various wall thicknesses. The weld quality was assessed based on metallographic examination, hardness measurements and destructive testing.

Since electromagnetic pulse welding has some limitations, electromagnetic pulse crimping was investigated as alternative, as this process variant has some advantages compared to electromagnetic pulse welding. Axial crimp joints for axial loads were realised using internal workpieces with a double groove design (see figure 4 and 5). In order to optimise the groove design in a structured way and to minimise the amount of required experiments, the Design of Experiments method was used.

As a conclusion, both variants of the electromagnetic pulse process will be compared and evaluated.

Figure 1

Figure 2 : Copper - aluminium weld

Figure 3 : Copper-brass weld

Figure 4 : Crimp joint of steel components

Figure 5 : Section of the joint of figure 4