Process for producing sheets of magnetic materials

Claim 1

IN A PROCESS FOR MAKING MAGENTIC ALLOY SHEET FROM AN ALLOY COMPRISING BY WEIGHT, FROM 25% TO 45% COBALT, UP TO 5% OF AT LEAST ONE ELEMENT SELECTED FROM THE GROUP CONSISTING OF VANADIUM AND CHROMIUM, AND THE BALANCE IRON EXCEPT FOR SMALL AMOUNTS OF IMPURITIES, THE DELETERIOUS IMPURITIES AMOUNTING TO NO MORE THAN 0.02%, THE STEPS COMPRISING, MELTING THE ALLOY, SUBJECTING THE ALLOY TO SUBATMOSPHERIC PRESSURE WHILE IN THE MOLTEN CONDITION, CASTING AN INGOT OF THE ALLOY, HEATING THE INGOT IN A PROTECTIVE ATOMSPHERE TO A TEMPERTURE IN THE RANGE FROM 950*C. TO 1200*C., HOT ROLLING THE INGOT IN A PROTECTIVE ATMOSPHERE TO FORM STRIP, REHEATING THE STRIP TO A TEMPERATURE IN THE RANGE FROM 850*C. TO 1000*C. FOR FROM 1 TO 10 MINUTES, RAPIDLY QUENCHING THE STRIP TO PRODUCE A DUCTILE STRUCTURE, COLD ROLLING THE STRIP TO EFFECT A REDUCTION OF AT LEAST 50% TO A SHEET OF PREDETERMINED THICKNESS, FINAL ANNEALING THE SHEET AT A TEMPERATURE OF 850*C. FOR FROM ABOUT 10 MINUTES TO FOUR HOURS IN AN ATMOSPHERE OF DRY HYDROGEN HAVING A DEW POINT OF -45*C. OR LOWER, COOLING THE SHEET IN A MAGNETIC FIELD OF AT LEAST 1.5 OERSTEDS AT A RATE OF FROM 1*C. PER MINUTE TO 5*C. PER MINUTE TO A TEMPERATURE OF FROM 550*C. TO 750*C., AND THEN RAPIDLY COOLING THE SHEET, THE SHEET WHEN TESTED IN TOROIDAL CORE FROM BEING CHARACTERIZED BY A HYSTERESIS CURVE OF A HIGH DEGREE OF RECTANGULARITY AS INDICATED BY A BY/BM RATIO OF AT LEAST ABOUT 70%, AND A 400 C.P.S. CORE LOSS OF LESS THAN 25 WATTS PER POUND AT 16 TO 18 KILOGAUSS.