Abstract An improved surface on sheet steel having a carbon content below 0.01%, preferably below 0.003%, for subsequent porcelain enameling or the deposition of a metal or organic, e.g., paint, coating thereon or in preparation of the sheet steel for a subsequent laminating operation, is provided by subjecting the sheet steel having a carbon content below about 0.1% by weight to oxidation in the presence of air under conditions to build up on the surface of the sheet steel undergoing oxidation an oxide layer having a thickness in the range 0.1-1.5 mils and such that the oxidized sheet steel exhibits a gain in weight of at least about 0.5 grams per square foot of oxidized surface, followed by subjecting the resulting oxidized sheet steel to reduction in an atmosphere consisting essentially of nitrogen and hydrogen, preferably at a temperature isothermal with the aforesaid oxidation temperature, such as at a temperature in the range 1000*-1500*F., to reduce substantially all of the oxide layer to metal and then subjecting the resulting oxidized-reduced sheet steel to decarburization at a temperature in the range 1000*1500*F. in an atmosphere consisting essentially of nitrogen, hydrogen and water vapor.
A METHOD OF TREATING AN OPEN COIL OF SHEET STEEL PRIOR TO COATING SAID SHEET STEEL WITH A PORCELAIN ENAMEL COATING SAID SHEET STEEL HAVING A THICKNESS IN THE RANGE FROM ABOUT 14 GAUGE TO ABOUT 28 GAUGE AND HAVING A CARBON CONTENT BELOW ABOUT 0.1% BY WEIGHT WHICH COMPRISES SUBJECTING SAID COIL OF SHEET STEEL TO OXIDATION IN CONTACT WITH AIR AT A TEMPERATURE IN THE RANGE 1000*-1500*F FOR A PERIOD OF TIME SUFFICIENT TO PRODUCE ON THE SURFACE OF SAID SHEET STEEL EXPOSE TO THE AIR AN OXIDE LAYER HAVING A THICKNESS IN THE RANGE FROM ABOUT 0.1 TO ABOUT 1.5 MILS THE RESULTING OXIDIZED COIL OF SHEET STEEL EXHIBITING A GAIN IN WEIGHT IN THE RANGE FROM ABOUT 0.5 TO ABOUT 7.0 GRAMS PER SQUARE FOOT OF SURFACE EXPOSED TO THE AIR SUBJECTING THE OXIDIZED COIL OF SHEET STEEL O A REDUCING ATMOSPHERE CONSISTING ESSENTIALLY OF NITROGEN AND HYDROGEN AT A TEMPERATURE IN THE RANGE FROM ABOUT 1000*F TO ABOUT 1500*F
Claim 2
Independent Claim
164 words
A METHOD OF TREATING AN OPEN COIL OF SHEET STEEL PRIOR TO COATING SAID SHEET STEEL WITH A PORCELAIN ENAMEL COATING SAID SHEET STEEL HAVING A THICKNESS IN THE RANGE FROM ABOUT 14 GAUGE TO ABOUT 28 GAUGE AND HAVING A CARBON CONTENT BELOW ABOUT 0.1% BY WEIGHT WHICH COMPRISES SUBJECTING SAID COIL OF SHEET STEEL TO OXIDATION IN CONTACT WITH AIR AT A TEMPERATURE IN THE RANGE 1000*-1500*F FOR A PERIOD OF TIME SUFFICIENT TO PRODUCE ON THE SURFACE OF SAID SHEET STEEL EXPOSE TO THE AIR AN OXIDE LAYER HAVING A THICKNESS IN THE RANGE FROM ABOUT 0.1 TO ABOUT 1.5 MILS THE RESULTING OXIDIZED COIL OF SHEET STEEL EXHIBITING A GAIN IN WEIGHT IN THE RANGE FROM ABOUT 0.5 TO ABOUT 7.0 GRAMS PER SQUARE FOOT OF SURFACE EXPOSED TO THE AIR SUBJECTING THE OXIDIZED COIL OF SHEET STEEL O A REDUCING ATMOSPHERE CONSISTING ESSENTIALLY OF NITROGEN AND HYDROGEN AT A TEMPERATURE IN THE RANGE FROM ABOUT 1000*F TO ABOUT 1500*F
Claim 3
Dependent Claim
30 words
A method in accordance with claim 1 wherein said fugitive organic binder is removed and the ceramic frit is fired to produce on the sheet steel a porcelain enamel coating.
Claim 4
Dependent Claim
26 words
A method in accordance with claim 2 wherein the fugitive binder is a curable organic binder and wherein the organic binder is removed by thermal decomposition.
Claim 5
Dependent Claim
26 words
A coil of sheet steel prepared by the method of claim 1 and having a coating of a ceramic frit dispersed in cured fugitive organic binder.