Spring steel
Spring steel includes: as a chemical composition, by mass %, C: 0.40% to 0.60%, Si: 0.90% to 2.50%, Mn: 0.20% to 1.20%, Cr: 0.15% to 2.00%, Ni: 0.10% to 1.00%, Ti: 0.030% to 0.100%, B: 0.0010% to 0.0060%, N: 0.0010% to 0.0070%, Cu: 0% to 0.50%, Mo: 0% to 1.00%, V: 0% to 0.50%, Nb: 0% to 0.10%, P: limited to less than 0.020%, S: limited to less than 0.020%, Al: limited to less than 0.050%, and a remainder including Fe and impurities, in a case where [Ti] represents a Ti content and [N] represents a N content by mass %, the chemical composition satisfies ([Ti]−3.43×[N])>0.03, and a total number density of a Ti carbide and a Ti carbonitride having a diameter of 5 nm to 100 nm is more than 50 piece/μm 3 .
1. A spring steel comprising: as a chemical composition, by mass %,
C: 0.42% to 0.58%,
Si: 0.90% to 2.50%,
Mn: 0.20% to 1.20%,
Cr: 0.15% to 2.00%,
Ni: 0.10% to 1.00%,
Ti: 0.030% to 0.100%,
B: 0.0010% to 0.0060%,
N: 0.0010% to 0.0070%,
Cu: 0% to 0.50%,
Mo: 0% to 1.00%,
V: 0% to 0.50%,
Nb: 0% to 0.10%,
P: limited to less than 0.020%,
S: limited to less than 0.020%,
Al: limited to less than 0.050%, and
a remainder comprising Fe and impurities,
wherein, in a case where [Ti] represents a Ti content and [N] represents a N content by mass %, the chemical composition satisfies
([Ti]−3.43×[N])>0.03, and
wherein a total number density of a Ti carbide and a Ti carbonitride having a diameter of 5 nm to 100 nm is more than 50 piece/μm 3 ,
wherein a tensile strength is 1,800 MPa or more, a reduction of area is 40% or more, and a Charpy impact value is 70 J/cm 2 or more, after a quenching and a tempering.
2. The spring steel according to claim 1 ,
wherein a delayed fracture strength ratio is 0.40 or more, after a quenching and a tempering.
3. A spring steel comprising: as a chemical composition, by mass %,
C: 0.42% to 0.58%,
Si: 0.90% to 2.50%,
Mn: 0.20% to 1.20%,
Cr: 0.15% to 2.00%,
Ni: 0.10% to 1.00%,
Ti: 0.030% to 0.100%,
B: 0.0010% to 0.0060%,
N: 0.0010% to 0.0070%,
Cu: 0% to 0.50%,
Mo: 0% to 1.00%,
V: 0% to 0.50%,
Nb: 0% to 0.10%,
P: limited to less than 0.020%,
S: limited to less than 0.020%,
Al: limited to less than 0.050%, and
a remainder comprising Fe and impurities,
wherein, in a case where [Ti] represents a Ti content and [N] represents a N content by mass %, the chemical composition satisfies
([Ti]−3.43×[N])>0.03, and
wherein a total number density of a Ti carbide and a Ti carbonitride having a diameter of 5 nm to 100 nm is more than 50 piece/μm 3 ,
wherein a tensile strength is 1,800 MPa or more, and a delayed fracture strength ratio is 0.40 or more, after a quenching and a tempering.
4. A spring comprising: as a chemical composition, by mass %,
C: 0.40% to 0.60%,
Si: 0.90% to 2.50%,
Mn: 0.20% to 1.20%,
Cr: 0.15% to 2.00%,
Ni: 0.10% to 1.00%,
Ti: 0.030% to 0.100%,
B: 0.0010% to 0.0060%,
N: 0.0010% to 0.0070%,
Cu: 0% to 0.50%,
Mo: 0% to 1.00%,
V: 0% to 0.50%,
Nb: 0% to 0.10%,
P: limited to less than 0.020%,
S: limited to less than 0.020%,
Al: limited to less than 0.050%, and
a remainder comprising Fe and impurities,
wherein, in a case where [Ti] represents a Ti content and [N] represents a N content by mass %, the chemical composition satisfies
([Ti]−3.43×[N])>0.03, and
wherein a total number density of a Ti carbide and a Ti carbonitride having a diameter of 5 nm to 100 nm is more than 50 piece/μm 3 ,
wherein a tensile strength is 1,800 MPa or more, a reduction of area is 40% or more, and a Charpy impact value is 70 J/cm 2 or more.