IP Library › Granted Patent US 9,902,135

Granted Patent B2

US 9,902,135 · App. 14/417,876 · Granted Feb 27, 2018

Galvanized steel sheet for hot forming

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Quick Facts

Patent No.: US 9,902,135
App. No.: 14/417,876
Granted: Feb 27, 2018
Kind: B2

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Abstract

A galvanized steel sheet for hot forming, the galvanized steel sheet including a galvanized film provided on a surface of a steel sheet, wherein the steel sheet has a chemical composition consisting of, in mass %, C: 0.02% to 0.58%, Mn: 0.5% to 3.0%, sol. Al: 0.005% to 1.0%, a predetermined element(s) as necessary; Si: less than or equal to 2.0%, P: less than or equal to 0.03%, S: less than or equal to 0.004%, N: less than or equal to 0.01%, and the balance: Fe and impurities, wherein a content of Mn in a portion from an interface of the steel sheet and the galvanized film to a depth of 5 μm is more than or equal to 0.3 mass %, wherein the galvanized film has a plating coverage of 40 g/m 2 to 110 g/m 2 , an Al content of more than or equal to 150 mg/m 2 within the galvanized film, and an Al concentration of less than or equal to 0.5 mass %, and wherein the galvanized steel sheet is used for an application in which the galvanized steel sheet is heated to 700° C. or above and is then subjected to hot forming.

Claims (77)

1. A galvanized steel sheet for hot forming, the galvanized steel sheet comprising a galvanized film provided on a surface of a steel sheet,

wherein the steel sheet has a chemical composition consisting of, in mass %,

C: 0.02% to 0.58%,

Mn: 0.5% to 3.0%,

sol. Al: 0.005% to 1.0%,

Ti: 0% to 0.20%,

Nb: 0% to 0.20%,

V: 0% to 1.0%,

W: 0% to 1.0%,

Cr: 0% to 1.0%,

Mo: 0% to 1.0%,

Cu: 0% to 1.0%,

Ni: 0% to 1.0%,

B: 0% to 0.010%,

Mg: 0% to 0.05%,

Ca: 0% to 0.05%,

REM: 0% to 0.05%,

Bi: 0% to 0.05%,

Si: less than or equal to 2.0%,

P: less than or equal to 0.03%,

S: less than or equal to 0.004%,

N: less than or equal to 0.01%, and

the balance: Fe and impurities,

wherein a content of Mn in a portion from an interface of the steel sheet and the galvanized film to a depth of 5 um is more than or equal to 0.3 mass %,

wherein the galvanized film has a plating coverage of 40 g/m 2 to 110 g/m 2 , an Al content of more than or equal to 150 mg/m 2 within the galvanized film, and an Al concentration of less than or equal to 0.5 mass %, and

wherein a metallographic structure of the steel sheet in the portion from the interface of the steel sheet and the galvanized film to the depth of 5 um has a ferrite area percentage of more than or equal to 60%.

2. The galvanized steel sheet for hot forming according to claim 1 , wherein the steel sheet comprises one or more selected from the group consisting of, in mass %,

Ti: 0.01% to 0.20%,

Nb: 0.01% to 0.20%,

V: 0.1% to 1.0%, and

W: 0.1% to 1.0%.

3. The galvanized steel sheet for hot forming according to claim 1 , wherein the steel sheet comprises one or more selected from the group consisting of, in mass %,

Cr: 0.1% to 1.0%,

Mo: 0.1% to 1.0%,

Cu: 0.1% to 1.0%,

Ni: 0.1% to 1.0%, and

B: 0.0010% to 0.010%.

4. The galvanized steel sheet for hot forming according to claim 2 , wherein the steel sheet comprises one or more selected from the group consisting of, in mass %,

Cr: 0.1% to 1.0%,

Mo: 0.1% to 1.0%,

Cu: 0.1% to 1.0%,

Ni: 0.1% to 1.0%, and

B: 0.0010% to 0.010%.

5. The galvanized steel sheet for hot forming according to claim 1 , wherein the steel sheet comprises one or more selected from the group consisting of, in mass %,

Mg: 0.0005% to 0.05%,

Ca: 0.0005% to 0.05%, and

REM: 0.0005% to 0.05%.

6. The galvanized steel sheet for hot forming according to claim 2 , wherein the steel sheet comprises one or more selected from the group consisting of, in mass %,

Mg: 0.0005% to 0.05%,

Ca: 0.0005% to 0.05%, and

REM: 0.0005% to 0.05%.

7. The galvanized steel sheet for hot forming according to claim 3 , wherein the steel sheet comprises one or more selected from the group consisting of, in mass %,

Mg: 0.0005% to 0.05%,

Ca: 0.0005% to 0.05%, and

REM: 0.0005% to 0.05%.

8. The galvanized steel sheet for hot forming according to claim 4 , wherein the steel sheet comprises one or more selected from the group consisting of, in mass %,

Mg: 0.0005% to 0.05%,

Ca: 0.0005% to 0.05%, and

REM: 0.0005% to 0.05%.

9. The galvanized steel sheet for hot forming according to claim 1 , wherein the steel sheet comprises, in mass %,