Limit of Al content in Fe-Si electrical steels

The precipitation structure of Fe-Si-Al strips containing different amounts of Al produced by different technologies was investigated by transmission scanning electron microscopy. It was found that the core loss is strongly correlated with the number of precipitates with 0.1-μm diameter. A comparison of the microstructure and the core-loss values of the samples clearly shows that these precipitates are the most harmful to these magnetic properties. The number and the size distribution of the precipitates can be controlled by the Al content of the material. The Al was effective up to 0.5 mass% content using the standard one-strand annealing technology