Exterior panel and automobile including the same

Patent metadata

Field	Value
Publication number	US-11975765-B2
Application number	US-202118013149-A
Country	US
Kind code	B2
Filing date	Jun 30, 2021
Priority date	Jul 3, 2020
Publication date	May 7, 2024
Grant date	May 7, 2024

Abstract

There is provided an exterior panel including a steel sheet, the steel sheet including a flat portion, wherein in an outer-layer region of the flat portion, a microstructure contains, in volume fraction, ferrite of 80% or more, an average grain diameter of ferrite is 1.0 to 15.0 μm, an intensity ratio X ODF{001}/{111},S of ferrite is 0.30 or more to less than 3.50, when uEl 1 denotes a uniform elongation measured with a tensile test specimen cut from the flat portion, and uEl 2 denotes a theoretical uniform elongation that is derived from volume fractions, hardnesses, and average grain diameters of ferrite and martensite in a microstructure of an inside region of the flat portion, and a sheet thickness of the flat portion, uEl 1 /uEl 2 is 0.44 to 0.80.

First claim

The invention claimed is:

1. An exterior panel including a steel sheet, the steel sheet including a flat portion, wherein
in an outer-layer region of the flat portion,
a microstructure contains, in volume fraction, ferrite of 80% or more,
an average grain diameter of ferrite is 1.0 to 15.0 μm,
an intensity ratio X ODF{001}/{111},S between {001} orientation and {111} orientation of ferrite is 0.30 or more to less than 3.50, and
when uEl 1 denotes a uniform elongation measured with a tensile test specimen cut from the flat portion, and
uEl 2 denotes a theoretical uniform elongation that is derived by Formula (I) shown below from volume fractions, hardnesses, and average grain diameters of ferrite and martensite in a microstructure of an inside region of the flat portion, and a sheet thickness of the flat portion,
uEl 1 /uEl 2 is 0.44 to 0.80:
uEl 2 =−0.057Hf×Vf/100−0.055Hm×Vm/100−0.35d −1/2 −0.571h+27.2  (I)

where the meaning of each symbol in Formula (I) above is as follows:
Hf: Vickers hardness (HV 0.01) of ferrite in the inside region
Hm: Vickers hardness (HV 0.01) of martensite in the inside region
Vf: Volume fraction (%) of ferrite in the inside region
Vm: Volume fraction (%) of martensite in the inside region
d: Average grain diameter (μm) in the inside region calculated from Formula (II) shown below
d =( df×Vf+dm×Vm )/( Vf+Vm )  (II)

df: Average grain diameter (μm) of ferrite in the inside region
dm: Average grain diameter (μm) of martensite in the inside region
h: Sheet thickness (mm) of the flat portion.

2. The exterior panel according to claim 1 , wherein a sheet thickness of the flat portion is 0.20 to 0.60 mm.

3. The exterior panel according to claim 1 , wherein a tensile strength of the steel sheet is 300 to 650 MPa.

4. An automobile comprising the exterior panel according to claim 1 .

5. The exterior panel according to claim 2 wherein a tensile strength of the steel sheet is 300 to 650 MPa.

6. An automobile comprising the exterior panel according to claim 2 .

7. An automobile comprising the exterior panel according to claim 3 .

8. An automobile comprising the exterior panel according to claim 5 .

Assignees

• Nippon Steel Corp

Inventors

• Sawa Yasunori
• Nagano Mai
• Nishimura Ryuichi

Classifications

• B62D29/007 Primary

  predominantly of special steel or specially treated steel, e.g. stainless steel or locally surface hardened steel · CPC title

• C21D9/46

  for sheet metals · CPC title

• C22C38/02

  containing silicon · CPC title

• C22C38/42

  with copper · CPC title

• C22C38/44

  with molybdenum or tungsten · CPC title