Method of manufacturing drawing steel

Claim 1

A PROCESS OF PRODUCING NON-AGING MILD STEEL SHEET STOCK FOR DRAWING PURPOSES, SAID STOCK INITIALLY CONTAINING AT LEAST ABOUT .03% CARBON AND AT LEAST ABOUT .004% NITROGEN, WHICH COMPRISES REDUCING SAID FERROUS MATERIAL TO GAUGE, HEAT TREATING IT IN A DECARBURIZING ATMOSPHERE HAVING A DEW POINT OF AT LEAST ABOUT 60*F. AND CONSISTING ESSENTIALLY OF NITROGEN IN PREPONDERANT QUANTITY, SUFFICIENT HYDROGEN TO PREVENT OXIDATION OF THE IRON DIOXIDE AND CARBON MONOXIDE, WHEREBY TO REDUCE ITS CARBON CONTENT TO A VALUE NOT GREATER THAN ABOUT .005%, AND THEREAFTER HEAT TREATING IT IN A FURNACE HAVING AN ATMOSPHERE PREPONDERANTLY OF HYDROGEN WITH A DEW POINT OF AT LEAST ABOUT 100F., SAID ATMOSPHERE HAVING A PARTIAL PRESSURE OF NITROGEN SUFFICIENTLY LOW TO PERMIT THE REDUCTION OF NITROGEN IN THE FERROUS MATERIAL TO THE RANGE OF ABOUT .001% TO ABOUT .0005% AND LOWER, WHILE ALSO REDUCING THE CARBON CONTENT TO A VALUE NOT GREATER THAN ABOUT .002%, AND CONTINUING THE LAST MENTIONED HEAT TREATMENT WHILE PASSING THE SAID ATMOPHERE CONTINUOUSLY OVER THE SURFACES OF THE FERROUS MATERIAL AND OUT OF THE FURNACE, UNTIL THE EFFLUENT ATMOSPHERE CEASES TO SHOW TRACES OF AMMONIA.