High-strength galvanized steel sheet

Patent metadata

Field	Value
Publication number	US-9994939-B2
Application number	US-201515519730-A
Country	US
Kind code	B2
Filing date	Aug 19, 2015
Priority date	Oct 17, 2014
Publication date	Jun 12, 2018
Grant date	Jun 12, 2018

Abstract

A high-strength galvanized steel sheet comprising a cold-rolled steel sheet, an intermetallic compound formed on the cold-rolled steel sheet, and a galvanizing layer formed on the intermetallic compound, the cold-rolled steel sheet having a specific composition and a microstructure having a martensite area ratio of 7% or more and less than 25% and a ferrite area ratio of 50% or more and which includes a base metal surface portion in which the amount of internal oxides per single side is 0.05 g/m 2 or less.

First claim

The invention claimed is:

1. A high-strength galvanized steel sheet comprising a cold-rolled steel sheet, an intermetallic compound formed on the cold-rolled steel sheet, and a galvanizing layer formed on the intermetallic compound, the cold-rolled steel sheet having a composition comprising, by mass %:
C: 0.06% or more and 0.09% or less;
Si: 0.30% or less;
Mn: 1.7% or more and 2.3% or less;
P: 0.001% or more and 0.020% or less;
S: 0.010% or less;
Mo: 0.05% or more and 0.30% or less;
N: 0.005% or less;
Al: 0.01% or more and 0.10% or less; and
the remainder being Fe and inevitable impurities,
wherein the cold-rolled steel sheet (i) has a microstructure having a martensite area ratio in a range of 7% to less than 25% and a ferrite area ratio of 50% or more, and (ii) includes a base metal surface portion in which an amount of internal oxides per single side is 0.05 g/m 2 or less on an oxygen basis,
the intermetallic compound comprises Al in a range of 0.03 g/m 2 or more and 0.12 g/m 2 or less and Fe 2 Al 5 with an average grain size of less than 0.7 μm,
the galvanizing layer comprises 0.15%≤Al %≤0.30%, where Al % represents the content (by mass %) of Al in the galvanizing layer, the galvanizing layer having a surface roughness Ra in a range of 0.8 μm or more and 1.6 μm or less, the galvanizing layer having a glossiness (G value) in a range of 750 or more and 850 or less, and
in the galvanizing layer, the zinc basal plane orientation ratio Zn (002)/(004) is in a range of 30% or more and 60% or less, Zn (002)/(004) being defined by equation (1):

Zn
⁡

(
002
)

/

(
004
)

=

{

Zn
⁢

⁢
crystal
⁢

⁢
orientation
⁢

⁢
of
⁢

⁢

(
002
)

⁢

⁢
plane

}

×

100
/

{

Zn
⁢

⁢
crystal
⁢

⁢
orientation
⁢

⁢
of
⁢

⁢

(
004
)

⁢

⁢
plane

}

⁢

⁢

Zn
⁢

⁢
crystal
⁢

⁢
orientation
⁢

⁢
of
⁢

⁢

(
xyz
)

⁢

⁢
plane

=

I

(
xyz
)

/

∑

I

(
xyz
)

I

std
⁡

(
xyz
)

/

∑

I

std
⁡

(
xyz

Assignees

• Jfe Steel Corp

Inventors

• Suzuki Yoshitsugu

Classifications

• Y10T428/12799

  Next to Fe-base component [e.g., galvanized] · CPC title

• C22C38/02

  containing silicon · CPC title

• C22C38/04

  containing manganese · CPC title

• Y10T428/1259

  Oxide · CPC title

• C22C18/04

  with aluminium as the next major constituent · CPC title