Formation of glass film on silicon steel by strip annealing

Claim 1

A PROCESS OF PRODUCING AN INSULATIVE GLASS FILM ON THIN COLD ROLLED SILICON STEEL STRIP, WHICH COMPRISES COATING SAID STRIP WITH A THIN COATING OF A SUBSTANCE CHOSEN FROM THE GROUP CONSISTING OF THE OXIDES AND HYDROXIDES OF THE ALKALINE EARTH METALS, AND PASSING SAID STRIP THROUGH A HOT ZONE AT SUCH A SPEED THAT IT REACHES A TEMPERATURE SUBSTANTIALLY BETWEEN 1900* AND 2200*F. IN A WET DECARBURIZING ATOMOSPHERE CONTAINING FREE HYDROGEN, SAID ATMOSPHERE BEING REDUCING TO IRON AND OXIDIZING TO SILICON, WHEREBY TO OXIDIZE SILICON THEREIN TO SILICA AT AND NEAR THE STRIP SURFACES, AND TO DEHYDRATE THE SAID COATING AND CAUSE THE ALKALINE EARTH METAL OXIDE TO COMBINE WITH SAID SILICA, THE TIME OF PASSAGE OF SAID STRIP THROUGH SAID HOT ZONE BEING SUCH AS TO PRODUCE AN OXIDATIVE EFFECT ON SILICON THEREIN SUBSTANTIALLY EQUIVALENT TO THAT PRODUCED BY THE PASSAGE OF SILICON STEEL STRIP .002 IN. THICK THROUGH SUCH HOT ZONE FOR A TIME AT LEAST ABOUT 20 SECONDS, IN WHICH HOT ZONE THE TEMPERATURE REACHES 2100*F.