Galvannealed Steel Sheet and Method for Producing the Same
OwnerTatsuya Nakagaito, Takayuki Futatsuka +3inventors
InventorsTatsuya Nakagaito, Takayuki Futatsuka, Hiroshi Matsuda, Yutaka Awajiya, Yasunobu Nagataki
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Abstract
A galvannealed steel sheet contains, by % by mass, about 0.05 to about 0.25% of C, about 2.0% or less of Si, about 1 to about 3% of Mn, about 0.1% or less of P, about 0.01% or less of S, about 0.3 to about 2% of Al, less than about 0.005% of N, about 1% or less of Cr, about 1% or less of V, about 1% or less of Mo, less than about 0.005% of Ti, and less than about 0.005% of Nb, and satisfies the relations, Si +Al >0.6% and Cr +V +Mo =0.1 to 2%, the balance being Fe and inevitable impurities.
Claims18
A galvannealed steel sheet including, by % by mass, about 0.05 to about 0.25% of C, about 2.0% or less of Si, about 1 to about 3% of Mn, about 0.1% or less of P, about 0.01% or less of S, about 0.3 to about 2% of Al, less than about 0.005% of N, about 1% or less of Cr, about 1% or less of V, about 1% or less of Mo, less than about 0.005% of Ti, and less than about 0.005% of Nb, and satisfying the relations, Si+Al≧0.6% and Cr+V+Mo=0.1 to 2%, the balance being Fe and inevitable impurities.
A galvannealed steel sheet including, by % by mass, about 0.05 to about 0.25% of C, about 2.0% or less of Si, about 1 to about 3% of Mn, about 0.1% or less of P, about 0.01% or less of S, about 0.3 to about 2% of Al, less than about 0.005% of N, about 1% or less of Cr, about 1% or less of V, about 1% or less of Mo, less than about 0.005% of Ti, and less than about 0.005% of Nb, and satisfying the relations, Si+Al≧0.6%, N≦0.007%−(0.003×Al)%, and Cr+V+Mo=0.1 to 2%, the balance being Fe and inevitable impurities.
A method for producing a galvannealed steel sheet, comprising:
- annealing, in a temperature range of about 730° C. to about 900° C., a cold-rolled steel sheet containing, by % by mass, about 0.05 to about 0.25% of C, about 2% or less of Si, about 1 to about 3% of Mn, about 0.1% or less of P, about 0.01% or less of S, about 0.3 to about 2% of Al, less than about 0.005% of N, about 1% or less of Cr, about 1% or less of V, about 1% or less of Mo, less than about 0.005% of Ti, and less than about 0.005% of Nb, and satisfying the relations, Si+Al≧0.6% and Cr+V+Mo=0.1 to 2%, the balance being Fe and inevitable impurities;
- cooling the annealed cold-rolled steel sheet at a cooling rate of about 3 to about 100° C./second;
- retaining the cooled cold-rolled steel sheet in a temperature range of about 350° C. to about 600° C. for about 30 to about 250 seconds;
- hot-dip galvanizing the cold-rolled steel sheet after the retention;
- and
- alloying the hot-dip galvanized cold-rolled steel sheet at a temperature of about 470° C. to about 600° C.
A method for producing a galvannealed steel sheet, comprising:
- annealing, in a temperature range of about 730° C. to about 900° C., a cold-rolled steel sheet containing, by % by mass, about 0.05 to about 0.25% of C, about 2% or less of Si, about 1 to about 3% of Mn, about 0.1% or less of P, about 0.01% or less of S, about 0.3 to about 2% of Al, less than about 0.005% of N, about 1% or less of Cr, about 1% or less of V, about 1% or less of Mo, less than about 0.005% of Ti, and less than about 0.005% of Nb, and satisfying the relations, Si+Al≧0.6%, N≦0.007%−(0.003×Al)%, and Cr+V+Mo=0.1 to 2%, the balance being Fe and inevitable impurities;
- cooling the annealed cold-rolled steel sheet at a cooling rate of about 3 to about 100° C./second;
- retaining the cooled cold-rolled steel sheet in a temperature range of about 350° C. to about 600° C. for about 30 to about 250 seconds;
- hot-dip galvanizing the cold-rolled steel sheet after the retention;
- and
- alloying the hot-dip galvanized cold-rolled steel sheet at a temperature of about 470° C. to about 600° C.
Dependencies are inferred from the claim text.