High-strength steel member

Abstract

A high-strength steel member having a predetermined chemical composition, having a tensile strength of 1,000 MPa or higher, containing 0.10% or more of, in terms of percent (%) by area, at least one Ti precipitate that has an average size of from 30 to 200 nm in terms of an average equivalent circle diameter and is selected from the group consisting of a Ti carbide, a Ti nitride, and a composite compound thereof, at a location of 1 mm in depth from a surface of the steel member, and containing 0.5 ppm by mass or more of non-diffusible hydrogen that is released in a temperature range of from 400 to 800° C. in a thermal desorption hydrogen analysis.

1 . A high-strength steel member having a chemical composition of, in terms of percent (%) by mass:
 C: from 0.10 to 0.50%,   Si: from 0.02 to 2.00%,   Mn: from 0.05 to 2.00%,   Cr: from 0.10 to 2.00%,   Ti: from 0.20 to 1.00%,   N: from 0.0020 to 0.0250%,   Al: from 0 to 0.100%,   V: from 0 to 0.50%,   Nb: from 0 to 0.50%,   Mo: from 0 to 1.00%,   B: from 0 to 0.0100%,   Cu: from 0 to 2.00%,   Ni: from 0 to 3.00%, and   a balance consisting of Fe and impurities,   having a tensile strength of 1,000 MPa or higher,   containing 0.10% or more of, in terms of percent (%) by area, at least one Ti precipitate that has an average size of from 30 to 200 nm in terms of an average equivalent circle diameter and is selected from the group consisting of a Ti carbide, a Ti nitride, and a composite compound thereof, at a location of 1 mm in depth from a surface of the steel member, and   containing 0.5 ppm by mass or more of non-diffusible hydrogen that is released in a temperature range of from 400 to 800° C. in a thermal desorption hydrogen analysis.   
     
     
         2 . The high-strength steel member according to  claim 1 , having a chemical composition including, in terms of percent (%) by mass, one or more of
 Al: from 0.005 to 0.100%,   V: from 0.01 to 0.50%,   Nb: from 0.01 to 0.50%, or   Mo: from 0.01 to 1.00%.   
     
     
         3 . The high-strength steel member according to  claim 1 , having a chemical composition including, in terms of percent (%) by mass,
 B: from 0.0003 to 0.0100%.   
     
     
         4 . The high-strength steel member according to  claim 1 , having a chemical composition including, in terms of percent (%) by mass, one or both of Cu: from 0.05 to 2.00% or Ni: from 0.05 to 3.00%. 
     
     
         5 . The high-strength steel member according to  claim 1 , wherein the Ti precipitate has an average aspect ratio of from 1.0 to 3.0. 
     
     
         6 . The high-strength steel member according to  claim 2 , having a chemical composition including, in terms of percent (%) by mass,
 B: from 0.0003 to 0.0100%.   
     
     
         7 . The high-strength steel member according to  claim 2 , having a chemical composition including, in terms of percent (%) by mass,
 one or both of Cu: from 0.05 to 2.00% or Ni: from 0.05 to 3.00%.   
     
     
         8 . The high-strength steel member according to  claim 2 , wherein the Ti precipitate has an average aspect ratio of from 1.0 to 3.0. 
     
     
         9 . The high-strength steel member according to  claim 3 , having a chemical composition including, in terms of percent (%) by mass,
 one or both of Cu: from 0.05 to 2.00% or Ni: from 0.05 to 3.00%.   
     
     
         10 . The high-strength steel member according to  claim 3 , wherein the Ti precipitate has an average aspect ratio of from 1.0 to 3.0. 
     
     
         11 . The high-strength steel member according to  claim 4 , wherein the Ti precipitate has an average aspect ratio of from 1.0 to 3.0. 
     
     
         12 . A high-strength steel member comprising a chemical composition, in terms of percent (%) by mass:
 C: from 0.10 to 0.50%,   Si: from 0.02 to 2.00%,   Mn: from 0.05 to 2.00%,   Cr: from 0.10 to 2.00%,   Ti: from 0.20 to 1.00%,   N: from 0.0020 to 0.0250%,   Al: from 0 to 0.100%,   V: from 0 to 0.50%,   Nb: from 0 to 0.50%,   Mo: from 0 to 1.00%,   B: from 0 to 0.0100%,   Cu: from 0 to 2.00%,   Ni: from 0 to 3.00%, and   a balance comprising Fe and impurities,   having a tensile strength of 1,000 MPa or higher,   containing 0.10% or more of, in terms of percent (%) by area, at least one Ti precipitate that has an average size of from 30 to 200 nm in terms of an average equivalent circle diameter and is selected from the group consisting of a Ti carbide, a Ti nitride, and a composite compound thereof, at a location of 1 mm in depth from a surface of the steel member, and   containing 0.5 ppm by mass or more of non-diffusible hydrogen that is released in a temperature range of from 400 to 800° C. in a thermal desorption hydrogen analysis.