Method for manufacturing high strength galvanized steel sheet

• US 10,449,751 B2
• Filed: 03/07/2013
• Issued: 10/22/2019
• Est. Priority Date: 03/19/2012
• Status: Active Grant

• Current Assignee: JFE Steel Corporation (JFE Holdings Incorporated)
• Original Assignee: JFE Steel Corporation (JFE Holdings Incorporated)
• Inventors: Fushiwaki, Yusuke, Kawasaki, Yoshiyasu, Nagataki, Yasunobu
• Primary Examiner(s): La Villa, Michael E.
• Application Number:
  US14/386,234
• Publication Number:
  US 20150030881A1
• Time in Patent Office: 2,420 Days
• CPC Class Codes: B32B 15/013 one layer being formed of an iron alloy or steel, another layer being formed of a metal other than iron or aluminium
• CPC Class Codes: B32B 15/04 comprising metal as the main or only constituent of a layer, which is next to another layer of the same or of a different material next to a bituminous or tarry layer B32B11/08; next to a water-setting substance layer B32B13/06; next to a glass layer B32B17/061; next to a cellulosic plastic layer B32B23/042
• CPC Class Codes: B32B 15/043 of metal B32B15/01 takes precedence
• CPC Class Codes: B32B 15/18 comprising iron or steel B32B15/011, B32B15/012 and B32B15/013 take precedence
• CPC Class Codes: C21D 1/26 Methods of annealing
• CPC Class Codes: C21D 8/0284 Application of a separating or insulating coating
• CPC Class Codes: C21D 9/46 for sheet metals
• CPC Class Codes: C21D 9/561 with a controlled atmosphere or vacuum
• CPC Class Codes: C22C 38/02 containing silicon
• CPC Class Codes: C22C 38/04 containing manganese
• CPC Class Codes: C22C 38/06 containing aluminium
• CPC Class Codes: C22C 38/12 containing tungsten, tantalum, molybdenum, vanadium, or niobium
• CPC Class Codes: C22C 38/14 containing titanium or zirconium
• CPC Class Codes: C22C 38/16 containing copper
• CPC Class Codes: C22C 38/18 containing chromium
• CPC Class Codes: C22C 38/20 with copper
• CPC Class Codes: C22C 38/22 with molybdenum or tungsten
• CPC Class Codes: C22C 38/26 with niobium or tantalum
• CPC Class Codes: C22C 38/28 with titanium or zirconium
• CPC Class Codes: C22C 38/32 with boron
• CPC Class Codes: C22C 38/40 : with nickel
• CPC Class Codes: C22C 38/42 : with copper
• CPC Class Codes: C22C 38/44 : with molybdenum or tungsten
• CPC Class Codes: C22C 38/48 : with niobium or tantalum
• CPC Class Codes: C22C 38/50 : with titanium or zirconium
• CPC Class Codes: C22C 38/54 : with boron
• CPC Class Codes: C23C 2/02 : Pretreatment of the material to be coated, e.g. for coating on selected surface areas C23C2/30 takes precedence
• CPC Class Codes: C23C 2/022 : by heating
• CPC Class Codes: C23C 2/024 : by cleaning or etching
• CPC Class Codes: C23C 2/06 : Zinc or cadmium or alloys based thereon
• CPC Class Codes: C23C 2/28 : Thermal after-treatment, e.g. treatment in oil bath
• CPC Class Codes: C23C 2/40 : Plates; Strips
• CPC Class Codes: C23C 30/005 : on hard metal substrates
• CPC Class Codes: Y10T 428/12799 : Next to Fe-base component [e.g., galvanized]

Abstract

A method for manufacturing a high strength galvanized steel sheet which has a zinc coating layer with an amount of deposition of coating of 20 to 120 g/m² 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, is provided. In annealing and galvanization treatment of the base steel sheet in a continuous galvanizing line, the maximum steel sheet temperature in an annealing furnace is 600° C. or higher and 750° C. or lower, the steel sheet transit time in a temperature region of the steel sheet temperature of 600° C. or higher and 750° 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 −10° C. or higher.

Claims

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/m² 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 750°

C. or lower,

the steel sheet transit time in a temperature region of the steel sheet temperature of 600°

C. or higher and 750°

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 −

10°

C. or higher, and

0.010 to 0.100 g/m² per one surface of oxides of at least one selected from Fe, Si, Mn, Al, P, B, Nb, Ti, Cr, Mo, Cu, and Ni are formed the surface layer within 100 μ

m from the base steel sheet surface just below the zinc coating and, in addition oxides containing Mn are present in the grains of the base steel sheet within 1 μ

m from the grain boundaries of the base steel sheet in the surface layer within 10 μ

m from the base steel sheet surface just below the zinc coating layer.

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. The method for manufacturing a high strength galvanized steel sheet, according to claim 1, wherein the chemical composition further contains 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%, on a percent by mass basis.

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 1, wherein the atmosphere of the annealing furnace is composed of nitrogen, hydrogen, and incidental impurities, and wherein the dew point is controlled by introducing humidified nitrogen.