Method for manufacturing high strength galvanized steel sheet and high strength galvanized steel sheet

Patent metadata

Field	Value
Publication number	US-10837074-B2
Application number	US-201314384298-A
Country	US
Kind code	B2
Filing date	Mar 7, 2013
Priority date	Mar 19, 2012
Publication date	Nov 17, 2020
Grant date	Nov 17, 2020

Abstract

A method for manufacturing a high strength galvanized steel sheet and a high strength galvanized steel sheet are provided. A base steel sheet having a chemical composition comprising C: 0.03% to 0.35%, Si: 0.01% to 0.50%, Mn: 3.6% to 8.0%, Al: 0.001% to 1.000%, P≤0.10%, S≤0.010%, and the balance comprising Fe and incidental impurities, on a percent by mass basis, is subjected to annealing and galvanization treatment, wherein the maximum steel sheet temperature in an annealing furnace is 600° C. or higher and 700° C. or lower, the steel sheet transit time in a temperature region of the maximum steel sheet temperature of 600° C. or higher and 700° C. or lower is specified to be 30 seconds or more and 10 minutes or less, and the dew point in an atmosphere is specified to be −45° C. or lower.

First claim

The invention claimed is:

1. A method for manufacturing a high strength galvanized steel sheet having a zinc coating layer with an amount of deposition of coating of 20 to 120 g/m 2 per one surface on the surface of a base steel sheet having a chemical composition comprising C: 0.03% to 0.35%, Si: 0.01% to 0.50%, Mn: 3.6% to 8.0%, Al: 0.001% to 1.000%, P≤0.10%, S≤0.010%, and the balance comprising Fe and incidental impurities, on a percent by mass basis, the method comprising the step of subjecting the base steel sheet to annealing and galvanization treatment in a continuous galvanizing line, wherein:
the maximum steel sheet temperature in an annealing furnace is 600° C. or higher and 700° C. or lower, and
the steel sheet transit time in a temperature region of the maximum steel sheet temperature of 600° C. or higher and 700° C. or lower is specified to be 30 seconds or more and 10 minutes or less, and the dew point in an atmosphere is specified to be −45° C. or lower; and
an amount of oxides of at least one selected from Fe, Si, Mn, Al and P generated in a surface layer within 100 μm from the base steel sheet surface just below the zinc coating layer is reduced to less than 0.030 g/m 2 per one surface.

2. The method for manufacturing a high strength galvanized steel sheet, according to claim 1 , wherein after the galvanization treatment is applied, an alloying treatment is further applied by heating the steel sheet to a temperature of 450° C. or higher and 600° C. or lower to specify the Fe content in the zinc coating layer to be within the range of 8 to 14 percent by mass.

3. A method for manufacturing a high strength galvanized steel sheet having a zinc coating layer with an amount of deposition of coating of 20 to 120 g/m 2 per one surface on the surface of a base steel sheet having a chemical composition comprising C: 0.03% to 0.35%, Si: 0.01% to 0.50%, Mn: 3.6% to 8.0%, Al: 0.001% to 1.000%, P≤0.10%, S≤0.010%, at least one selected from B: 0.001% to 0.005%, Nb: 0.005% to 0.050%, Ti: 0.005% to 0.050%, Cr: 0.001% to 1.000%, Mo: 0.05% to 1.00%, Cu: 0.05% to 1.00%, and Ni: 0.05% to 1.00%, and the balance comprising Fe and incidental impurities, on a percent by mass basis, the method comprising the step of subjecting the base steel sheet to annealing and galvanization treatment in a continuous galvanizing line, wherein:
the maximum steel sheet temperature in an annealing furnace is 600° C. or higher and 700° C. or lower, and
the steel sheet transit time in a temperature region of the maximum steel sheet temperature of 600° C. or higher and 700° C. or lower is specified to be 30 seconds or more and 10 minutes or less, and the dew point in an atmosphere is specified to be −45° C. or lower; and
an amount of oxides of at least one selected from Fe, Si, Mn, Al, P, B, Nb, Ti, Cr, Mo, Cu, and Ni generated in a surface layer within 100 μm from the base steel sheet surface just below the zinc coating layer are less than 0.030 g/m 2 per one surface.

4. The method for manufacturing a high strength galvanized steel sheet, according to claim 3 , wherein after the galvanization treatment is applied, an alloying treatment is further applied by heating the steel sheet to a temperature of 450° C. or higher and 600° C. or lower to specify the Fe content in the zinc coating layer to be within the range of 8 to 14 percent by mass.

5. The method for manufacturing a high strength galvanized steel sheet, according to claim 3 , wherein the base steel sheet has a chemical composition consisting of C: 0.03% to 0.35%, Si: 0.01% to 0.50%, Mn: 3.6% to 8.0%, Al: 0.001% to 1.000%, P≤0.10%, S≤0.010%, at least one selected from B: 0.001% to 0.005%, Nb: 0.005% to 0.050%, Ti: 0.005% to 0.050%, Cr: 0.001% to 1.000%, Mo: 0.05% to 1.00%, Cu: 0.05% to 1.00%, and Ni: 0.05% to 1.00%, and the balance consisting of Fe and incidental impurities.

6. The method for manufacturing a high strength galvanized steel sheet, according to claim 3 , wherein the amount of oxides of at least one selected from Fe, Si, Mn, Al and P generated in a surface layer within 100 μm from the base steel sheet surface just below the zinc coating layer is reduced to less than 0.030 g/m 2 per one surface.

Assignees

• Jfe Steel Corp

Inventors

• Fushiwaki Yusuke
• Kawasaki Yoshiyasu
• Nagataki Yasunobu

Classifications

• C21D9/46 Primary

  for sheet metals · CPC title

• C23C2/06 Primary

  Zinc or cadmium or alloys based thereon · CPC title

• C22C38/58

  with more than 1.5% by weight of manganese · CPC title

• C22C38/04

  containing manganese · CPC title

• C23C2/40

  Plates; Strips · CPC title