Case-hardening steel excellent in cold forgeability and low carburization distortion property
This invention provides a case-hardening steel excellent in cold forgeability and low carburization distortion property that exhibits low deformation resistance and high limit compressibility when cold, namely, a case-hardening steel excellent in cold forgeability and low carburization distortion property comprising, in mass %, C: 0.07% to 0.3%, Si: 0.01% to 0.15%, Mn: 0.1% to 0.7%, P: 0.03% or less, S: 0.002% to 0.10%, Al: 0.01% to 0.08%, Cr: 0.7% to 1.5%, Ti: 0.01% to 0.15%, B: 0.0005% to 0.005%, N: 0.008% or less, and the balance of Fe and unavoidable impurities, and having a metallographic structure comprising 65% or greater of ferrite and 15% or less of bainite.
1. A case-hardening steel excellent in cold forgeability and low carburization distortion property used in cold forged large components and complexly shaped components consisting of, in mass %,
C: 0.07% to 0.3%,
Si: 0.01% to 0.15%,
Mn: 0.1% to 0.7%,
P: 0.03% or less,
S: 0.002% to 0.10%,
Al: 0.01% to 0.08%,
Cr: 0.7% to 1.5%,
Ti: 0.01% to 0.029%,
B: 0.0005% to 0.005%,
N: 0.008% or less, and
the balance of Fe and unavoidable impurities,
and having a metallographic structure comprising 65% or greater of ferrite and 15% or less of bainite by means of a cooling rate of 0.3° C./sec or less, and having cold deformation resistance of 650 MPa or less.
2. The case-hardening steel of claim 1 , wherein the steel does not include Mo.
3. A case-hardening steel excellent in cold forgeability and low carburization distortion property used in cold forged large components and complexly shaped components consisting of, in mass %,
C: 0.07% to 0.3%,
Si: 0.01% to 0.15%,
Mn: 0.1% to 0.7%,
P: 0.03% or less,
S: 0.002% to 0.10%,
Al: 0.01% to 0.08%,
Cr: 0.7% to 1.5%,
Ti: 0.01% to 0.029%,
B: 0.0005% to 0.005%,
N: 0.008% or less, and
the balance of Fe and unavoidable impurities,
wherein the steel does not include Mo, and having a metallographic structure comprising 65% or greater of ferrite and 15% or less of bainite and having cold deformation resistance of 650 MPa or less.
4. The case-hardening steel of claim 1 or claim 3 , wherein Ti: 0.01% to 0.026.
5. The case-hardening steel of claim 1 or claim 3 , wherein the limit compressibility is 51% or greater.
6. The case-hardening steel of claim 1 or claim 3 , wherein the case-hardening steel is selected from a cold forged large component and a complexly shaped component.
7. The case-hardening steel of claim 5 , wherein the steel is a helical gear.