High-strength steel sheet

Abstract

A high-strength steel sheet has high stretch flangeability after working and corrosion resistance after painting. The steel sheet contains, on the basis of mass percent, C: 0.02% to 0.20%, Si: 0.3% or less, Mn: 0.5% to 2.5%, P: 0.06% or less, S: 0.01% or less, Al: 0.1% or less, Ti: 0.05% to 0.25%, and V: 0.05% to 0.25%, the remainder being Fe and incidental impurities. The steel sheet has a substantially ferritic single phase, the ferritic single phase containing precipitates having a size of less than 20 nm, the precipitates containing 200 to 1750 mass ppm Ti and 150 to 1750 mass ppm V, V dissolved in solid solution being 200 or more but less than 1750 mass ppm.

1 . A high-strength steel sheet comprising, on the basis of mass percent, C: 0.02% to 0.20%, Si: 0.3% or less, Mn: 0.5% to 2.5%, P: 0.06% or less, S: 0.01% or less, Al: 0.1% or less, Ti: 0.05% to 0.25%, and V: 0.05% to 0.25%, the remainder being Fe and incidental impurities, having a substantially ferritic single phase, containing precipitates having a size of less than 20 nm, the precipitates containing 200 to 1750 mass ppm Ti and 150 to 1750 mass ppm V, V dissolved in solid solution being 200 or more but less than 1750 mass ppm. 
     
     
         2 . The high-strength steel sheet according to  claim 1 , further comprising, on the basis of mass percent, any one or two or more of Cr: 0.01% to 0.5%, W: 0.005% to 0.2%, and Zr: 0.0005% to 0.05%. 
     
     
         3 . The high-strength steel sheet according to  claim 1 , having a tensile strength TS of 780 MPa or more. 
     
     
         4 . The high-strength steel sheet according to  claim 1 , having a one-side maximum peel width of 3.0 mm or less after a tape peel test in a warm salt water immersion test. 
     
     
         5 . The high-strength steel sheet according to  claim 3 , having a one-side maximum peel width of 3.0 mm or less after a tape peel test in a warm salt water immersion test. 
     
     
         6 . The high-strength steel sheet according to  claim 1 , having a stretch flangeability λ 10  of 60% or more after rolling at an elongation percentage of 10%. 
     
     
         7 . The high-strength steel sheet according to claim  3, having a stretch flangeability λ   10  of 60% or more after rolling at an elongation percentage of 10%. 
     
     
         8 . The high-strength steel sheet according to  claim 2 , having a tensile strength TS of 780 MPa or more. 
     
     
         9 . The high-strength steel sheet according to  claim 2 , having a one-side maximum peel width of 3.0 mm or less after a tape peel test in a warm salt water immersion test. 
     
     
         10 . The high-strength steel sheet according to  claim 8 , having a one-side maximum peel width of 3.0 mm or less after a tape peel test in a warm salt water immersion test. 
     
     
         11 . The high-strength steel sheet according to  claim 2 , having a stretch flangeability λ 10  of 60% or more after rolling at an elongation percentage of 10%. 
     
     
         12 . The high-strength steel sheet according to  claim 3 , having a stretch flangeability λ 10  of 60% or more after rolling at an elongation percentage of 10%.