Cold rolled steel strip with improved drawing properties and method for producing same

Claim 1

A METHOD FFOR PRODUCING A FINISHED STEEL STRIP WITH IMPROVED DEEP DRAWING PROPERTIES, SAID METHOD COMPRISING THE STEPS OF: PROVIDING A SOLIDIFIED KILLED STEEL CONSISTING ESSENTIALLY OF 0.04 -0.006 WT. PERCENT CARBON , 0.02-0.50 WT. PERCENY MANGANESE, LESS THAN 0.015 WT. PERCENT NITROGEN, TITANIUM IN AN AMOUNT BY WEIGHT AT LEAST SIX TIMES THE COMBINED CARBON AND NITROGEN CONTENT, AND A BALANCE CONSISTING ESSENTIALLY OF IRON; HOT ROLLING SAID STEEL INTO HOT ROLLED STRIP, WITH A HOT ROLL FINISHING TEMPERATURE GREATER THAN 1,645*F; COLD ROLLING SAID HOT ROLLED STRIP INTO COLD ROLLED STRIP WITH A COLD REDUCTION OF AT LEAST 60 PERCENT; ANNEALING SAID COLD ROLLED STRIP, AT A TEMPERATURE EXCEEDING 1,285*F. AND BELOW THE TEMPERATURE AT WHICH AUSTENITE BEGINS TO FORM IN SAID STEEL, WITHOUT DECARBURIZING, FOR A TIME SUFFICIENT TO COMPLETELY RECRYSTALLIZE THE COLD ROLLED STRIP AND PRODUCE A CRYSTALLOGRAPHIC ORIENTATION IN WHICH THERE IS A RELATIVELY HIGH INCIDENCE, IN THE PLANE OF THE STRIP, OF CUBE ON CORNER CRYSTAL PLANES AND A RELATIVELY LOW INCIDENCE, IN THE PLANE OF THE STRIP, OF CUBE OF FACE CRYSTAL PLANES; SAID STRIP HAVING A GRAIN SIZE ANNEALING, AT LAST AS FINE AS 8.0 AND A CARBON CONTENT, AFTER ANNEALING ESSENTIALLY THE SAME AS THE CARBON CONTENT BEFORE ANNEALING; AND TEMPER ROLLING AFTER ANNEALING; SAID FINISHED STEEL STRIP HAVING AN AVERAGE PLASTIC STRAIN RATI O (R) OF AT LEAST 1.9 AND A STRENGTH, EXPRESSED AS 0.2 PERCENT PROOF STRESS, IN THE RANGE 15,000-25,000 PSI.

Claim 2

A METHOD FFOR PRODUCING A FINISHED STEEL STRIP WITH IMPROVED DEEP DRAWING PROPERTIES, SAID METHOD COMPRISING THE STEPS OF: PROVIDING A SOLIDIFIED KILLED STEEL CONSISTING ESSENTIALLY OF 0.04 -0.006 WT. PERCENT CARBON , 0.02-0.50 WT. PERCENY MANGANESE, LESS THAN 0.015 WT. PERCENT NITROGEN, TITANIUM IN AN AMOUNT BY WEIGHT AT LEAST SIX TIMES THE COMBINED CARBON AND NITROGEN CONTENT, AND A BALANCE CONSISTING ESSENTIALLY OF IRON; HOT ROLLING SAID STEEL INTO HOT ROLLED STRIP, WITH A HOT ROLL FINISHING TEMPERATURE GREATER THAN 1,645*F; COLD ROLLING SAID HOT ROLLED STRIP INTO COLD ROLLED STRIP WITH A COLD REDUCTION OF AT LEAST 60 PERCENT; ANNEALING SAID COLD ROLLED STRIP, AT A TEMPERATURE EXCEEDING 1,285*F. AND BELOW THE TEMPERATURE AT WHICH AUSTENITE BEGINS TO FORM IN SAID STEEL, WITHOUT DECARBURIZING, FOR A TIME SUFFICIENT TO COMPLETELY RECRYSTALLIZE THE COLD ROLLED STRIP AND PRODUCE A CRYSTALLOGRAPHIC ORIENTATION IN WHICH THERE IS A RELATIVELY HIGH INCIDENCE, IN THE PLANE OF THE STRIP, OF CUBE ON CORNER CRYSTAL PLANES AND A RELATIVELY LOW INCIDENCE, IN THE PLANE OF THE STRIP, OF CUBE OF FACE CRYSTAL PLANES; SAID STRIP HAVING A GRAIN SIZE ANNEALING, AT LAST AS FINE AS 8.0 AND A CARBON CONTENT, AFTER ANNEALING ESSENTIALLY THE SAME AS THE CARBON CONTENT BEFORE ANNEALING; AND TEMPER ROLLING AFTER ANNEALING; SAID FINISHED STEEL STRIP HAVING AN AVERAGE PLASTIC STRAIN RATI O (R) OF AT LEAST 1.9 AND A STRENGTH, EXPRESSED AS 0.2 PERCENT PROOF STRESS, IN THE RANGE 15,000-25,000 PSI.