Use of nitrogen-bearing base coatings in the manufacture of high permeability silicon steel

Claim 1

In a process for producing electromagnetic silicon steel having a cube-on-edge orientation and a permeability of at least 1850 (G/O e ) at 10 oersteds, which process includes the steps of: preparing a melt of silicon steel consisting essentially of, by weight, up to 0.07% carbon, from 2.6 to 4.0% silicon, from 0.03 to 0.24% manganese, from 0.01 to 0.09% of material selected from the group consisting of sulfur and selenium, from 0.015 to 0.04% aluminum, up to 0.0035% boron, up to 0.02% nitrogen, up to 0.5% copper, balance iron; casting said steel; hot rolling said steel into a hot rolled band; cold rolling said steel, decarburizing said steel; and final texture annealing said steel; the improvement comprising the steps of coating the surface of said steel with a base coating consisting essentially of: (a) 100 parts, by weight, of at least one substance selected from the group consisting of boron, boron compounds, sulfur, sulfur compounds, selenium, selenium compounds, and oxides and hydroxides of magnesium, calcium, aluminum, titanium and manganese; and (b) 0.5 to 50 parts, by weight, of at least one nitrogen-bearing compound selected from the group consisting of (NH 4 ) 2 SO 4 , Fe(NO 3 ) 3 , Al(NO 3 ) 3 , Mg(NO 3 ) 2 and Zn(NO 3 ) 2 ; and final texture annealing said steel; said steel's texture and magnetic properties being, in part, attributable to said nitrogen bearing compound.