High-strength flat steel wire excellent in hydrogen induced cracking resistance

Abstract

A high-strength flat steel wire contains, by mass %: C: 0.25 to 0.60%; Si: greater than 0.50% and less than 2.0%; Mn: 0.20 to 1.50%; S: 0.015% or less; P: 0.015% or less; Cr: 0.005 to 1.50%; Al: 0.005 to 0.080%; N: 0.0020 to 0.0080%; and one or two of Ca: 0 to 0.0050% and Mg: 0 to 0.0050% to satisfy [Ca]+[Mg]>0.20×[S], with the balance composed of Fe and impurities, the high-strength flat steel wire has tensile strength of 1000 MPa or more, an average value of Hv hardness measured in a cross section perpendicular to a longitudinal direction of 320 or more and less than 450, a standard deviation σHv of the measured value of 15 or less, and a width/thickness ratio of not less than 1.5 nor more than 10. [Ca], [Mg], and [S] represent contents of respective elements by mass %.

1 - 4 . (canceled) 
     
     
         5 . A high-strength flat steel wire excellent in hydrogen induced cracking resistance, containing, by mass %:
 C: 0.25 to 0.60%;   Si: greater than 0.50% and less than 2.0%;   Mn: 0.20 to 1.50%;   S: 0.015% or less;   P: 0.015% or less;   Cr: 0.005 to 1.50%;   Al: 0.005 to 0.080%;   N: 0.0020 to 0.0080%; and   one or two of Ca: 0 to 0.0050% and Mg: 0 to 0.0050% to satisfy the following expression <1>, wherein:   components which are optionally contained include:   Ti: 0.10% or less;   Nb: 0.050% or less;   V: 0.50% or less;   Cu: 1.0% or less;   Ni: 1.50% or less;   Mo: 1.0% or less;   B: 0.01% or less;   REM: 0.10% or less; and   Zr: 0.10% or less;   the balance is composed of Fe and impurities; and   tensile strength is 1000 MPa or more, an average value of Hv hardness measured in a cross section perpendicular to a longitudinal direction is 320 or more and less than 450, a standard deviation σHv of the measured value is 15 or less, and a width/thickness ratio is not less than 1.5 nor more than 10,
   [Ca]+[Mg]>0.20×[S]  <1>
 
   where [Ca], [Mg], and [S] in the above expression <1> represent contents of respective elements by mass %.   
     
     
         6 . The high-strength flat steel wire excellent in the hydrogen induced cracking resistance according to  claim 5 , further containing, by mass %, at least one or two or more selected from Ti: 0.001 to 0.10%, Nb: 0.001 to 0.050%, and V: 0.01 to 0.50%. 
     
     
         7 . The high-strength flat steel wire excellent in the hydrogen induced cracking resistance according to  claim 5 , further containing, by mass %, at least one or two or more selected from Cu: 0.01 to 1.0%, Ni: 0.01 to 1.50%, Mo: 0.01 to 1.0%, and B: 0.0002 to 0.01%. 
     
     
         8 . The high-strength flat steel wire excellent in the hydrogen induced cracking resistance according to  claim 6 , further containing, by mass %, at least one or two or more selected from Cu: 0.01 to 1.0%, Ni: 0.01 to 1.50%, Mo: 0.01 to 1.0%, and B: 0.0002 to 0.01%. 
     
     
         9 . The high-strength flat steel wire excellent in the hydrogen induced cracking resistance according to  claim 5 , further containing, by mass %, at least one or two selected from REM: 0.0002 to 0.10%, and Zr: 0.0002 to 0.10%. 
     
     
         10 . The high-strength flat steel wire excellent in the hydrogen induced cracking resistance according to  claim 6 , further containing, by mass %, at least one or two selected from REM: 0.0002 to 0.10%, and Zr: 0.0002 to 0.10%. 
     
     
         11 . The high-strength flat steel wire excellent in the hydrogen induced cracking resistance according to  claim 7 , further containing, by mass %, at least one or two selected from REM: 0.0002 to 0.10%, and Zr: 0.0002 to 0.10%. 
     
     
         12 . The high-strength flat steel wire excellent in the hydrogen induced cracking resistance according to  claim 8 , further containing, by mass %, at least one or two selected from REM: 0.0002 to 0.10%, and Zr: 0.0002 to 0.10%. 
     
     
         13 . A high-strength flat steel wire excellent in hydrogen induced cracking resistance, containing, by mass %:
 C: 0.25 to 0.60%;   Si: greater than 0.50% and less than 2.0%;   Mn: 0.20 to 1.50%;   S: 0.015% or less;   P: 0.015% or less;   Cr: 0.005 to 1.50%;   Al: 0.005 to 0.080%;   N: 0.0020 to 0.0080%; and   one or two of Ca: 0 to 0.0050% and Mg: 0 to 0.0050% to satisfy the following expression, wherein:   components which are optionally contained include:   Ti: 0.10% or less;   Nb: 0.050% or less;   V: 0.50% or less;   Cu: 1.0% or less;   Ni: 1.50% or less;   Mo: 1.0% or less;   B: 0.01% or less;   REM: 0.10% or less; and   Zr: 0.10% or less;   the balance comprises Fe and impurities; and   tensile strength is 1000 MPa or more, an average value of Hv hardness measured in a cross section perpendicular to a longitudinal direction is 320 or more and less than 450, a standard deviation σHv of the measured value is 15 or less, and a width/thickness ratio is not less than 1.5 nor more than 10,
   [Ca]+[Mg]>0.20×[S]
 
   where [Ca], [Mg], and [S] in the above expression represent contents of respective elements by mass %.