Method of using a critical cold rolling stage to produce silicon-iron sheets

Claim 1

THE PROCESS OF PRODUCING SHEETS OF IRON-SILICON ALLOY HAVING A FACE TEXTURE, THE ALLOY CONSISTING ESSENTIALLY OF FROM 2% TO 5% SILICON, UP TO 1% OF AT LEAST ONE ELEMENT FROM THE GROUP CONSISTING OF MANGANESE, MOLYBDENIUM AND CHROMIUM, AND THE BALANCE BEING IRON EXCEPT FOR SMALL AMOUNTS OF ADDITIVES AND IMPURITIES, THE STEPS COMPRISING, COLD ROLLING IN AT LEAST TWO STAGES HOT ROLLED SHEET OF THE IRON-SILICON ALLOY HAVING A RANDOM GRAIN TEXTURE TO A FINAL GAUGE TO EFFECT A REDUCTION IN THICKNESS OF THE SHEET OF AT LEAST 93% IN AT LEAST ONE OF THE LAST TWO STAGES OR IN AT LEAST ONE OF THE LAST THREE STAGES OF COLD ROLLING WHEN MORE THAN TWO STAGES OF COLD ROLLING ARE APPLIED THERETO, THE REDUCTION IN THE THICKNESS IN THE OTHER STAGES BEING AT LEAST 30%, SUBJECTING THE COLD ROLLED SHEET TO AN INTERMEDIATE ANNEAL AT A TEMPERATURE OF FROM 800*C. TO 1100*C. BETWEEN EACH TWO SUCCESSIVE COLD ROLLING STAGES, AND FINALLY ANNEALING THE SHEET AT FINAL GAUGE THICKNESS AT A TEMPERATURE OF ABOVE 1100*C. FOR A PERIOD OF TIME SUFFICIENT TO EFFECT SUBSTANTIALLY COMPLETE SECONDARY RECRYSTALLIZATION THEREOF, THE SURFACE OF THE SHEET AT THE TIME OF INITIATION OF THE FINAL ANNEAL BEING FREE FROM ANY THICK, ADHERENT, CONTINUOUS OXIDE SURFACE LAYERS AND ANY SHEET SEPARATOR COATING OF A REFRACTORY MATERIAL PRESENT ON THE SURFACE BEING POROUS AND SUBSTANTIALLY NON-OXIDIZING TO THE SHEET SURFACE DURING THE FINAL ANNEALS, THE FINAL ANNEALING ATMOSPHERE BEING A REDUCE ATMOSPHERE SUBSTANTIALLY FREE FROM MOISTURE AND OTHER OXIDIZING COMPONENTS WHICH WOULD REACT WITH THE SURFACE OF THE SHEET, SO CORRELATING THE FINAL ANNEALING TEMPERATURE, THE FINAL ANNEALING ATMOSPHERE AND ANY MATERIAL PRESENT ON OR NEAR THE SURFACE OF THE SHEET THAT DURING THE INITIAL STAGES OF THE FINAL ANNEAL PRIOR TO THE OCCURENCE OF ANY APPRECIABLE RECRYSTALLIZATION ANY CONTINUOUS SURFACE OXIDES ON THE SHEET SURFACE WILL DISAPPEAR WHEREBY GRAIN NUCLEI HAVING FACES PARALLEL TO THE SHEET SURFACE PRESENT AT THE END OF THE PRIMARY RECRYSTALLIZATION WILL GROW PREFERENTIALLY TO OTHER GRAIN NUCLEI TO PRODUCE A FACE TEXTURE IN THE SHEET.