Steel plate excellent in shape freezing property and method for production thereof

A method for producing a thin ferritic steel sheet excellent in shape fixability comprising the steps of;

• hot rolling, with reheating to a temperature range of 1000° C. to 1300° C., or without reheating, a cast slab, containing, in terms of weight %,
• C:
• 0.001 to 0.3%,
• Si:
• 0.001 to 3.5%,
• Mn:
• less than 3%,
• P:
• 0.005 to 0.15%,
• S:
• less than 0.03%,
• Al:
• 0.01 to 3.0%,
• N:
• less than 0.01%,
• O:
• less than 0.01%, and remainder Fe and unavoidable impurities, with a total reduction rate of 25% or more at (Ar3−100) to (Ar3+100)° C.,
• terminating the hot rolling at (Ar3−100)° C. or more,
• cooling the hot rolled steel sheet, then coiling the cooled steel sheet, so that the steel sheet having a mean value of X-ray random intensity ratios of a group of {100} <011> to {223} <110> orientations at least at ½ of the sheet thickness, is 3.0 or more and a mean value of X-ray random intensity ratios of three orientations of {554} <225>, {111} <112>, and {111} <110> is 3.5 or less.

A method for producing a thin ferritic steel sheet excellent in shape fixability comprising the steps of;

• hot rolling, with reheating to a temperature range of 1000° C. to 1300° C., or without reheating, a cast slab, containing, in terms of weight %,
• C:
• 0.001 to 0.3%,
• Si:
• 0.001 to 3.5%,
• Mn:
• less than 3%,
• P:
• 0.005 to 0.15%,
• S:
• less than 0.03%,
• Al:
• 0.01 to 3.0%,
• N:
• less than 0.01%,
• O:
• less than 0.01%, and remainder Fe and unavoidable impurities, with a total reduction rate of 25% or more at (Ar3+50) to (Ar3+150)° C., and continuing the hot rolling with a total of reduction rates of 5 to 35% at (Ar3−100) to (Ar3+50)° C.,
• terminating the hot rolling at (Ar3−100) to (Ar3+50)° C.,
• cooling the hot rolled steel sheet, then coiling the cooled steel sheet, so that the steel sheet having a mean value of X-ray random intensity ratios of a group of {100} <011> to {223} <110> orientations at least at ½ sheet of the thickness is 3.0 or more and a mean value of X-ray random intensity ratios of three orientations of {554} <225>, {111} <112>, and {111} <110> is 3.5 or less.

A method for producing a thin ferritic steel sheet excellent in shape fixability comprising the steps of;

• roughing hot rolling, with a temperature range of 1000° C. to 1300° C., or without reheating, a cast slab containing, in terms of weight %,
• C:
• 0.001 to 0.3%,
• Si:
• 0.001 to 3.5%,
• Mn:
• less than 3%,
• P:
• 0.005 to 0.15%,
• S;
• less than 0.03%,
• Al:
• 0.01 to 3.0%,
• N:
• less than 0.01%,
• O:
• less than 0.01%, and remainder Fe and unavoidable impurities, exceeding a transformation temperature of Ar3,
• finish hot rolling at a temperature below an Ar3 transformation temperature,
• terminating the hot rolling at a temperature below an Ar3 transformation temperature, cooling the hot rolled steel sheet, then coiling the cooled steel sheet, so that the steel sheet having a mean value of X-ray random intensity ratios of a group of {100} <011> to {223} <110> orientations at least at ½ of the sheet thickness is 3.0 or more and a mean value of X-ray random intensity ratios of three orientations of {554} <225>, {111} <112>, and {111} <110> is 3.5 or less.