Diode laser scribing of non-oriented 3 wt% Si-steel for core loss reduction

The electrical power industries are experiencing a considerable energy loss in transformers and motors because of inefficiencies caused by core loss. The objective of our research is to investigate any effect of laser scribing on the reduction of the core loss in the low cost, non-oriented steels used in numerous utility applications. A 15 W diode laser transmitted through fiber optics was used to scribe 0.35 mm thick, non-oriented 3 wt% Si steel. The magnetic properties including the core loss and permeability were evaluated both before and after laser scribing. A maximum core loss reduction of 0.08 W kg−1 at a magnetic induction of 1 T and a 21% increase in relative permeability were obtained at the optimum laser parameters. These results are comparable to those of laser scribed, expensive grain-oriented steels. The core losses were further reduced using a treatment procedure consisting of laser scribing, chemical etching, and stress relief annealing performed in sequence. The laser scribing method is simpler, energy efficient, and can be implemented in the production line.