High-strength steel sheet and method for manufacturing the same

Patent metadata

Field	Value
Publication number	US-2016289784-A1
Application number	US-201415038223-A
Country	US
Kind code	A1
Filing date	Nov 13, 2014
Priority date	Nov 22, 2013
Publication date	Oct 6, 2016
Grant date	—

Abstract

A high-strength steel sheet and a method for manufacturing a high-strength steel sheet having excellent phosphatability and excellent corrosion resistance after electrodeposition coating has been performed, even in the case where the contents of Si and Mn are high. The method may comprise annealing a steal sheet by using a continuous annealing method, performing a heating process, controlling the maximum end-point temperature of a steel sheet in the annealing furnace, controlling the traveling time of the steel sheet, and controlling the dew point of the atmosphere.

First claim

1 . A method for manufacturing a high-strength steel sheet, the method comprising, when annealing by a continuous annealing method a steel sheet having a chemical composition comprising: C: 0.03% to 0.35%, by mass %, Si: 0.01% to 0.50%, by mass %, Mn: 3.6% to 8.0%, by mass %, Al: 0.01% to 1.0%, by mass %, P: 0.10% or less, by mass %, S: 0.010% or less, by mass %, and Fe and incidental impurities:
performing a heating process in an annealing furnace at a heating rate of 7° C./s or more at a temperature in the range of 450° C. to A° C., where A: 500≦A≦600; controlling the maximum end-point temperature of the steel sheet in the annealing furnace to be in the range of 600° C. to 700° C.; controlling the traveling time of the steel sheet in a steel sheet temperature range of 600° C. to 700° C. to be in the range of 30 seconds to 10 minutes; and controlling the dew point of the atmosphere in the steel sheet temperature range of 600° C. to 700° C. to be −40° C. or lower.

2 . The method for manufacturing a high-strength steel sheet according to claim 1 , wherein the chemical composition further comprises one or more elements selected from the group consisting of B: 0.001% to 0.005%, by mass %, Nb: 0.005% to 0.05%, by mass %, Ti: 0.005% to 0.05%, by mass %, Cr: 0.001% to 1.0%, by mass %, Mo: 0.05% to 1.0%, by mass %, Cu: 0.05% to 1.0%, by mass %, Ni: 0.05% to 1.0%, by mass %, Sn: 0.001% to 0.20%, by mass %, Sb: 0.001% to 0.20%, by mass %, Ta: 0.001% to 0.10%, by mass %, W: 0.001% to 0.10%, by mass %, and V: 0.001% to 0.10%, by mass %.

3 . The method for manufacturing a high-strength steel sheet according to claim 1 , the method further comprising, after performing the annealing by the continuous annealing method, performing electrolytic pickling in an aqueous solution containing sulfuric acid.

4 . A high-strength steel sheet, the steel sheet being manufactured according to the method for manufacturing a high-strength steel sheet of claim 1 ,
wherein the total amount of oxides of Fe, Si, Mn, Al, P, B, Nb, Ti, Cr, Mo, Cu, Ni, Sn, Sb, Ta, W, and V formed in a surface layer on each side of the steel sheet within 100 μm of a surface of the steel sheet is less than 0.030 g/m 2 .

5 . The high-strength steel sheet according to claim 4 , wherein the total amount of oxides of Fe, Si, Mn, Al, P, B, Nb, Ti, Cr, Mo, Cu, Ni, Sn, Sb, Ta, W, and V formed in the surface layer on each side of the steel sheet within 100 μm of the surface of the steel sheet is 0.0001 g/m 2 or more.

6 . The method for manufacturing a high-strength steel sheet according to claim 2 , the method further comprising, after performing the annealing by the continuous annealing method, performing electrolytic pickling in an aqueous solution containing sulfuric acid.

7 . A high-strength steel sheet, the steel sheet being manufactured according to the method for manufacturing a high-strength steel sheet of claim 2 ,
wherein the total amount of oxides of Fe, Si, Mn, Al, P, B, Nb, Ti, Cr, Mo, Cu, Ni, Sn, Sb, Ta, W, and V formed in a surface layer on each side of the steel sheet within 100 μm of a surface of the steel sheet is less than 0.030 g/m 2 .

8 . A high-strength steel sheet, the steel sheet being manufactured according to the method for manufacturing a high-strength steel sheet of claim 3 ,
wherein the total amount of oxides of Fe, Si, Mn, Al, P, B, Nb, Ti, Cr, Mo, Cu, Ni, Sn, Sb, Ta, W, and V formed in a surface layer on each side of the steel sheet within 100 μm of a surface of the steel sheet is less than 0.030 g/m 2 .

9 . The high-strength steel sheet according to claim 7 , wherein the total amount of oxides of Fe, Si, Mn, Al, P, B, Nb, Ti, Cr, Mo, Cu, Ni, Sn, Sb, Ta, W, and V formed in the surface layer on each side of the steel sheet within 100 μm of the surface of the steel sheet is 0.0001 g/m 2 or more.

10 . The high-strength steel sheet according to claim 8 , wherein the total amount of oxides of Fe, Si, Mn, Al, P, B, Nb, Ti, Cr, Mo, Cu, Ni, Sn, Sb, Ta, W, and V formed in the surface layer on each side of the steel sheet within 100 μm of the surface of the steel sheet is 0.0001 g/m 2 or more.

Assignees

• Jfe Steel Corp

Inventors

• Fushiwaki Yusuke
• Kawasaki Yoshiyasu

Classifications

• C22C38/02

  containing silicon · CPC title

• C25F1/06

  Iron or steel · CPC title

• C22C38/002

  containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60 · CPC title

• C22C38/16

  containing copper · CPC title

• C22C38/06

  containing aluminium · CPC title