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US 2025/0027181 A1Published application
Cold rolled steel sheet and method of manufacturing same
AssigneePosco
InventorYoung-Roc Im
Life of this patent
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Abstract
The present disclosure relates to a cold rolled steel sheet having excellent weldability, strength and formability and a method of manufacturing the same. An aspect of the present disclosure is to provide a cold-rolled steel sheet having excellent weldability, strength, and formability, and a method of manufacturing the same. As set forth above, according to an aspect of the present disclosure, a cold-rolled steel sheet having excellent weldability, strength, and formability and a method of manufacturing the same may be provided.
Claims17
A cold-rolled steel sheet, comprising by weight:
- C:
- 0.14 to 0.16%, Si:
- 0.3 to 0.6%, Al:
- 0.01 to 0.3%, Mn:
- 2.6 to 3.0%, Cr:
- 0.01 to 0.25%, Mo:
- 0.15 to 0.4%, B:
- 0.0001 to 0.005%, Nb:
- 0.001 to 0.05%, Ti:
- 0.001 to 0.05%, P:
- 0.04% or less (excluding 0%), S:
- 0.01% or less (excluding 0%), N:
- 0.01% or less (excluding 0%), with a remainder of Fe and other unavoidable impurities, wherein the following Relational Expressions 1 and 2 are satisfied,
- wherein a microstructure consists of retained austenite:
- more than 1% and 5% or less, fresh martensite:
- 10% or more and less than 25%, bainite:
- less than 20% (excluding 0%), tempered martensite:
- 55% or more and less than 80%, and ferrite:
- 5% or less (including 0%),
- 234×[C]−29×[Si]−128×[Al]+29×[Mn]+10×[Cr]−17×[Mo]−37×[Nb]−49×[Ti]+100×[B]≥80 [Relational Expression 1]
- 5×[C]+[Si]+0.5×[Al]≤1.5 [Relational Expression 2]
- where a content of each element in the above Relational Expressions 1 and 2 refers to % by weight.
19 more elements
A method for manufacturing a cold-rolled steel sheet, comprising:
- heating a slab including by weight:
- C:
- 0.14 to 0.16%, Si:
- 0.3 to 0.6%, Al:
- 0.01 to 0.3%, Mn:
- 2.6 to 3.0%, Cr:
- 0.01 to 0.25%, Mo:
- 0.15 to 0.4%, B:
- 0.0001 to 0.005%, Nb:
- 0.001 to 0.05%, Ti:
- 0.001 to 0.05%, P:
- 0.04% or less (excluding 0%), S:
- 0.01% or less (excluding 0%), N:
- 0.01% or less (excluding 0%), with a remainder of Fe and other unavoidable impurities, wherein the following Relational Expressions 1 and 2 are satisfied;
- finish hot rolling the heated slab at a temperature within a range of 830 to 980° C. to obtain a hot-rolled steel sheet;
- coiling the hot-rolled steel sheet at a temperature within a range of 450 to 700° C.;
- cold rolling the coiled hot-rolled steel sheet to obtain a cold-rolled steel sheet;
- continuously annealing the cold-rolled steel sheet at a temperature within a range of 800 to 840° C.;
- primarily cooling the continuously annealed steel sheet at an average cooling rate of less than 10° C./s to a primary cooling end temperature of 550 to 650° C.;
- secondarily cooling the primarily cooled steel sheet at an average cooling rate of 10° C./s or more to a secondary cooling end temperature of 320 to 360° C.;
- and
- reheating the secondarily cooled steel sheet to a temperature within a range of 380 to 480° C.,
- 234×[C]−29×[Si]−128×[Al]+29×[Mn]+10×[Cr]−17×[Mo]−37×[Nb]−49×[Ti]+100×[B]≥80 [Relational Expression 1]
- 5×[C]+[Si]+0.5×[Al]≤1.5 [Relational Expression 2]
- where a content of each element in the above Relational Expressions 1 and 2 refers to % by weight.
22 more elements
Dependencies are inferred from the claim text.