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This research has shown that it is possible to enrich with Si electrical sheet steels by utilising a combination of CVD (chemical vapour deposition) and diffusion. CVD conditions at 900 deg C, utilising 2 % SiH4 in Ar for three minutes alternated with four minutes of annealing conditions (Ar only) in the same reactor at 1050 deg C for a total time of four hours, increased the Si content in the F10 electrical sheet from the original 1.0 % to over 6.0 %. Steady CVD conditions at 1100 deg C for one hour increased the Si content of the same F10 samples to about 3.5 %. The magnetic behaviours (reduced loss) of the resulting Si enriched samples were similar to those of the upper classes of commercial materials having approximately twice the Si content of each original sample. The Si diffusion constant into the magnetic sheet steel was experimentally calculated from GDOES (glow discharge optical emission spectroscopy) depth profiles and it was found to be 1.2x10 -11 m2/s and 0.8x10-11 m2/s in the Si concentration ranges 2.7 to 3.5 wt.-% and 2.5 to 2.7 wt.-%, respectively. The results indicated that a series of CVD apparatus with increasing partial pressures of the Si carrying gas in the vapour phase would be a much more efficient method for Si enrichment. However, in this case the long diffusion time does not seem to make the industrialisation of the process feasible.