US 12,709,791 B2Granted

High-strength galvannealed steel sheet having excellent powdering resistance and manufacturing method therefor

AssigneePosco

InventorsYu-Mi Ha, Jun-Sung Yeom, Ji-Ho Hong

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Abstract

Provided is a galvannealed steel sheet having excellent powdering resistance, and a manufacturing method therefor. The galvannealed steel sheet includes: base iron; and an alloying hot-dip galvanized layer provided on the surface thereof. The base iron includes, by weight %; 0.003 to 0.009% of carbon (C); 0.05% or less of silicon (Si); 0.4 to 1.0% of manganese (Mn); 0.04 to 0.09% of phosphorus (P); 0.01% or less of sulfur (S); 0.005% or less of nitrogen (N); 0.1% or less of aluminum (S.Al); 0.05 to 0.08% of molybdenum (Mo); 0.005 to 0.03% of titanium (Ti); 0.02 to 0.045% of niobium (Nb); 0.06 to 0.1% of copper (Cu); 0.0015% or less of boron (B), and a balance of Fe and inevitable impurities. An average thickness of a gamma (γ) phase present at an interface between the base iron and the alloying hot-dip galvanized layer is 0.20 μm or less.

Claims8

Dependent claims

A galvannealed steel sheet, comprising:

base iron;
and
an alloying hot-dip galvanized layer provided on at least one surface of the base iron,
wherein the base iron includes, by weight %;
0.003 to 0.009% of carbon (C);
0.05% or less of silicon (Si);
0.4 to 1.0% of manganese (Mn);
0.04 to 0.09% of phosphorus (P);
0.01% or less of sulfur(S);
0.005% or less of nitrogen (N);
0.1% or less of aluminum (S.Al);
0.05 to 0.08% of molybdenum (Mo);
0.005 to 0.03% of titanium (Ti);
0.02 to 0.045% of niobium (Nb);
0.06 to 0.1% of copper (Cu);
0.0015% or less of boron (B), and a balance of Fe and other inevitable impurities, the base iron satisfying the following Relational expression 1,
wherein an average thickness of a gamma (γ) phase present at an interface between the base iron and the alloying hot-dip galvanized layer is 0.20 μm or less, and
wherein the alloying hot-dip galvanized layer, by weight %, comprises 0.05 to 0.3% of aluminum (Al);
10 to 20% of iron (Fe), and a balance of zinc (Zn) and other inevitable impurities,
0.08
≤
[
Ti
]
/
{
4
⁢
8
⋆
(
[
Mo
]
/
96
+
[
Si
]
/
28
)
}
≤
0
.
3
[
Relational
⁢
expression
⁢
1
]
in the Relational expression, [Ti], [Mo], and [Si] are contents (wt %) of titanium (Ti), molybdenum (Mo), and silicon (Si) contained in the base iron, respectively.

53 more elements

A manufacturing method for a galvannealed steel sheet, comprising operations of:

preparing a cold-rolled steel sheet including, by weight %:
0.003 to 0.009% of carbon (C);
0.05% or less of silicon (Si);
0.4 to 1.0% of manganese (Mn);
0.04 to 0.09% of phosphorus (P);
0.01% or less of sulfur(S);
0.005% or less of nitrogen (N);
0.1% or less of aluminum (S.Al);
0.05 to 0.08% of molybdenum (Mo);
0.005 to 0.03% of titanium (Ti);
0.02 to 0.045% of niobium (Nb);
0.06 to 0.1% of copper (Cu);
0.0015% or less of boron (B), and a balance of Fe, and other inevitable impurities, the cold-rolled steel sheet satisfying the following Relational expression 1;
dipping the cold-rolled steel sheet in a hot-dip galvanizing bath at an inlet temperature of 490 to 500° C., based on a surface temperature of the cold-rolled steel sheet to provide a plated steel sheet having a hot-dip galvanized layer formed thereon;
and
heating the plated steel sheet to a temperature range of 500 to 560° C. to subject the plated steel sheet to alloying,
0.08
≤
[
Ti
]
/
{
4
⁢
8
⋆
(
[
Mo
]
/
96
+
[
Si
]
/
28
)
}
≤
0
.
3
[
Relational
⁢
expression
⁢
1
]
in the Relational expression 1, [Ti], [Mo], and [Si] are contents (wt %) of titanium (Ti), molybdenum (Mo), and silicon (Si) contained in the cold-rolled steel sheet, respectively.

50 more elements

Dependencies are inferred from the claim text.

Facts

Application: 18/265,412Filed 9 Dec 2021
Priority: KR 10-2020-017335311 Dec 2020
Published: US 2024/0026511 A125 Jan 2024
Granted: 18 Aug 2026
Term ends: Not estimatedThe source records don’t support an estimate.

Classification29 codes

C23C 2/024
Pretreatment of the material to be coated, e.g. for coating on selected surface areas: by cleaning or etching
B32B 15/013
All layers being exclusively metallic: one layer being formed of an iron alloy or steel, another layer being formed of a metal other than iron or…
C21D 8/0226
Characterised by the working steps: hot rolling
C21D 8/0236
Characterised by the working steps: cold rolling