Electromagnetic devices such as motors, generators, magnets, and solenoids, use stacked laminations made from silicon-iron (Si--Fe) for example for providing efficient flux paths for the operation thereof. The laminations must be suitable stacked together either using mechanical fasteners or by welding. Exemplary mechanical fasteners include straps, keys, and rivets suitable positioned in the laminations for holding them together. However, the laminations are typically pre-machined for accepting the mechanical fasteners such as by being punched or providing apertures therefor, which premachining induces stress in the laminations. A pulsed annealing operation is therefore typically required for reducing the residual stresses for minimizing magnetic core losses therefrom. The location of the fasteners themselves may also lead to inefficient flux paths within the laminations decreasing the efficiency of the device.
Welding, on the other hand, necessarily heats the laminations which adversely affects the magnetic properties thereof and may distort the laminations. This may require a pulsed-heat treatment to reclaim the lost magnetic properties and remove the distortions.
Conventional TIG welding is one process known to provide excessive heat into the laminations necessarily requiring the pulsed-heat treatment thereof. Excessive heat input into the laminations may also cause physical distortion thereof which must be suitably corrected in order to obtain a satisfactory product.
It is also known to use a conventional CO.sub.2 laser for welding stacked laminations for reducing the heat input thereto and reducing both thermal distortion thereof and the degradation of magnetic properties therein. However, CO.sub.2 lasers when conventionally used for welding are typically operated as continuous-wave lasers and therefore continuously input heat into the welded member although such heat input is significantly less than that from conventional TIG welding. Continuously applied welding heat and the resulting continuous, substantially uniform weld bead may still degrade the magnetic properties of the laminations from excessive heat.