Steel sheet and fabrication method thereof

Patent metadata

Field	Value
Publication number	US-9486984-B2
Application number	US-201514703895-A
Country	US
Kind code	B2
Filing date	May 5, 2015
Priority date	May 5, 2014
Publication date	Nov 8, 2016
Grant date	Nov 8, 2016

Abstract

Provided is a steel sheet including an iron-based material, a first coating layer disposed on the iron-based material, and a second coating layer disposed on the first coating layer, wherein the first coating layer includes a zinc alloy and the second coating layer consists essentially of chromium and carbon.

First claim

What is claimed is:

1. A steel sheet, comprising an iron-based material, a first coating layer disposed on the iron-based material, and a second coating layer disposed on the first coating layer, wherein the first coating layer comprises a zinc alloy and the second coating layer consists essentially of chromium and carbon, and chromium of the second coating layer has a crystal structure with carbon doped in the chromium crystal structure, wherein a content of carbon in the second coating layer is greater than 10 at. %.

2. The steel sheet as claimed in claim 1 , wherein the zinc alloy is a zinc-nickel alloy, a zinc-cobalt alloy, or a combination thereof.

3. The steel sheet as claimed in claim 1 , wherein the zinc alloy is a zinc-nickel alloy, and a proportion of nickel thereof is between 16 at. % and 30 at. %.

4. The steel sheet as claimed in claim 1 , wherein the zinc alloy is a zinc-nickel alloy, and a proportion of nickel thereof is about 20 at. %.

5. The steel sheet as claimed in claim 1 , wherein a reduction potential of the zinc alloy is less than a reduction potential of the iron-based material by at least 100 mV.

6. The steel sheet as claimed in claim 1 , wherein a melting point of the zinc alloy is higher than an austenitizing temperature of the iron-based material.

7. The steel sheet as claimed in claim 1 , wherein thicknesses of each of the first coating layer and the second coating layer are respectively 2 μm to 100 μm and 0.1 μm to 10 μm.

8. A fabrication method of a steel sheet, comprising:
providing an iron-based steel material;
forming a first coating layer on a surface of the iron-based steel material; and
forming a second coating layer on the first coating layer, wherein the first coating layer comprises a zinc alloy and the second coating layer consists essentially of chromium and carbon, and chromium of the second coating layer has a crystal structure with carbon doped in the chromium crystal structure, wherein a content of carbon in the second coating layer is greater than 10 at. %.

9. The method as claimed in claim 8 , further comprising forming a surface layer on the second coating layer, wherein the surface layer comprises ZnCr 2 O 4 .

10. The method as claimed in claim 9 , wherein the surface layer further comprises ZnO and Cr 2 O 3 .

11. The method as claimed in claim 8 , further comprising performing a heating step to remove substantially all carbon in the second coating layer.

12. The method as claimed in claim 8 , further comprising performing a heating step to oxidize chromium on a surface of the second coating layer and remove substantially all carbon in the second coating layer.

13. The method as claimed in claim 12 , wherein the heating step makes zinc in the first coating layer diffuse to the surface of the second coating layer.

14. The method as claimed in claim 13 , wherein the heating step oxidizes zinc that is diffused to the surface of the second coating layer.

Assignees

• Univ Nat Taiwan
• China Steel Corp

Inventors

• Lin Chao-Sung
• Chen Tsung-Jung
• Wu Chun-Hung

Classifications

• Y10T428/1259

  Oxide · CPC title

• C22C38/04

  containing manganese · CPC title

• C23C8/10

  Oxidising · CPC title

• Y10T428/12611

  Oxide-containing component · CPC title

• C23C28/345

  with at least one oxide layer · CPC title