Galvannealed steel sheet

Patent metadata

Field	Value
Publication number	US-9821534-B2
Application number	US-201214373809-A
Country	US
Kind code	B2
Filing date	Jun 15, 2012
Priority date	Jan 23, 2012
Publication date	Nov 21, 2017
Grant date	Nov 21, 2017

Abstract

A galvannealed steel sheet includes a zinc coating layer containing 7 to 15% Fe on the surface of steel sheet including, C: 0.02% to 0.30%, Si: 0.01% to 2.5%, Mn: 0.1% to 3.0%, P: 0.003% to 0.08%, S: not more than 0.01%, Al: 0.001% to 0.20%, one or more selected from Ti: 0.03% to 0.40%, Nb: 0.001% to 0.2%, V: 0.001% to 0.2%, Mo: 0.01% to 0.5% and W: 0.001% to 0.2%. In the zinc coating layer, carbides with average particle size of 1 nm to 20 nm including one or more selected from titanium, niobium, vanadium, molybdenum and tungsten are present with a density of five or more particles per segment that is defined by the thickness of the coating layer and also by dividing a cross section of the coating layer at intervals of 1 μm in a direction perpendicular to the thickness of the coating layer.

First claim

The invention claimed is:

1. A galvannealed steel sheet comprising a zinc coating layer on the surface of a steel sheet, the zinc coating layer containing 7 to 15 mass % Fe, the steel sheet having a chemical composition comprising, by mass %, C: 0.02% to 0.30%, Si: 0.01% to 2.5%, Mn: 0.1% to 3.0%, P: 0.003% to 0.08%, S: not more than 0.01%, Al: 0.001% to 0.20%, one, or two or more selected from Ti: 0.03% to 0.40%, Nb: 0.001% to 0.2%, V: 0.001% to 0.5%, Mo: 0.01% to 0.5% and W: 0.001% to 0.2%, and the balance comprising Fe and inevitable impurities,
the zinc coating layer containing carbides including one, or two or more selected from titanium, niobium, vanadium, molybdenum and tungsten, the carbides having an average particle size of 1 nm to 20 nm, the carbides having a density of from five to fifty particles per segment,
the segment being defined by dividing a cross section of the coating layer at intervals of 1 μm in a direction perpendicular to the direction of the thickness of the coating layer (t 1 ), measured in μm, the segment having an area of (t 1 ×1) μm 2 .

2. The galvannealed steel sheet according to claim 1 , wherein the chemical composition of the steel sheet further includes, by mass %, B: 0.0002% to 0.005%.

3. The galvannealed steel sheet according to claim 1 , wherein the steel sheet is a hot rolled steel sheet.

4. The galvannealed steel sheet according to claim 2 , wherein the steel sheet is a hot rolled steel sheet.

Assignees

• Harako Daisuke
• Fushiwaki Yusuke
• Suzuki Yoshitsugu
• Nagataki Yasunobu
• Jfe Steel Corp

Inventors

• Harako Daisuke
• Fushiwaki Yusuke
• Suzuki Yoshitsugu
• Nagataki Yasunobu

Classifications

• B32B15/013 Primary

  one layer being formed of an iron alloy or steel, another layer being formed of a metal other than iron or aluminium · CPC title

• C22C38/12

  containing tungsten, tantalum, molybdenum, vanadium, or niobium · CPC title

• C23C2/28

  Thermal after-treatment, e.g. treatment in oil bath · CPC title

• C22C38/14

  containing titanium or zirconium · CPC title

• C21D8/0226

  Hot rolling · CPC title