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US 2024/0182996 A1Published application
Steel material for hot forming, hot-formed member, and manufacturing method therefor
AssigneePosco
InventorsSea-Woong Lee, Jin-Keun Oh, Seong-Woo Kim, Sang-Heon Kim, Hyo-Sik Chun, Sang-Bin Han
Life of this patent
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Abstract
The present invention relates to: a steel material for hot forming, used for a vehicle and the like; a hot-formed member; and a method for manufacturing same. In the method, when the formed steel material is skin pass rolled, rolling pressure and roughness of skin pass rolling rolls are controlled so that bendability can be improved.
Claims12
A steel material for hot forming comprising, by weight:
- 0.04 to 0.45% of carbon (C);
- 1.5% or less of silicon (Si) (excluding 0%);
- 0.2 to 2.5% of manganese (Mn);
- 0.05% or less of phosphorous (P);
- 0.02% or less of sulfur (S);
- 0.01 to 0.1% of aluminum (Al);
- 0.01 to 5.0% of chromium (Cr);
- 0.02% or less of nitrogen (N), and a balance of iron (Fe) and inevitable impurities,
- wherein a surface roughness factor calculated by the following [Relationship 1] is 1.8 μm or less,
- Surface
-
- Roughness
-
- Factor
- =
- Rt
- 100
- +
- 10
- ×
- Rdq
- [
- Relationship
-
- 1
- ]
- where Rt is defined as a vertical distance between a highest peak and a deepest valley in a random measurement section on a surface of a steel sheet, and Rdq is a root mean square of a slope of the peak in a random measurement section on the surface of the steel sheet.
24 more elements
A method for manufacturing a steel material for hot forming, the method comprising operations of:
- obtaining a cold-rolled steel sheet using a steel slab comprising, by weight:
- 0.04 to 0.45% of carbon (C);
- 1.5% or less of silicon (Si) (excluding 0%);
- 0.2 to 2.5% of manganese (Mn);
- 0.05% or less of phosphorous (P);
- 0.02% or less of sulfur (S);
- 0.01 to 0.1% of aluminum (Al);
- 0.01 to 5.0% of chromium (Cr);
- 0.02% or less of nitrogen (N), and a balance of Fe and inevitable impurities;
- and
- skin pass rolling the cold-rolled steel sheet to satisfy the following [Relationship 2],
- √{square root over (P×Raroll)}≤40, (ton·μm)1/2 [Relationship 2]
- where P is rolling force during skin pass rolling, and Raroll is arithmetic average roughness (Ra) of a skin pass rolling roll.
10 more elements
12-17 (canceled)
Dependencies are inferred from the claim text.