Production method of carburized steel component and carburized steel component
A production method of a carburized steel, which improves a gas carburizing property of a steel having a high Si content and suppress deterioration of productivity, includes preliminary and main gas carburizing processes. In the preliminary gas carburizing process, a steel having a chemical composition that contains C, Si, Mn, and Cr and, in mass %, satisfies Formula (1) is subjected to a gas carburizing treatment at a carburizing temperature T p ° C. that satisfies Formula (A) for 10 minutes to less than 20 hours. In the main gas carburizing process, a gas carburizing treatment is performed at a carburizing temperature T r (° C.) that satisfies Formula (B) for a carburizing time t r minutes. 6.5<3.5[Si %]+[Mn %]+3[Cr %]≤18 (1) 800≤ T p <163×ln( CP +0.6)−41×ln(3.5×[Si %]+[Mn %]+3×[Cr %])+950 (A) 4<13340/( T r +273.15)−ln( t r )<7 (B) Where, CP in the formula is substituted by a carbon potential during carburization in the preliminary carburizing process.
1. A production method of a carburized steel component comprising:
a preliminary gas carburizing process, wherein a steel component having a chemical composition that consists of: by mass %, C: 0.1 to 0.4%, Si: 0.7 to 4.0%, Mn: 0.2 to 3.0%, Cr: 0.5 to 5.0%, Al:
0.005 to 0.15%, S: not more than 0.3%, N: 0.003 to 0.03%, 0: not more than 0.0050%, P: not more than 0.025%, Nb: 0 to 0.3%, Ti: 0 to 0.3%,
V: 0 to 0.3%, Ni: 0 to 3.0%, Cu: 0 to 3.0%, Co: 0 to 3.0%, Mo: 0 to 1.0%, W: 0 to 1.0%, B: 0 to 0.005%, Ca: 0 to 0.01%, Mg: 0 to 0.01%, Zr: 0 to 0.05%, Te: 0 to 0.1%, and rare earth metals: 0 to 0.005%, with the balance being Fe and impurities, and that satisfies Formula (1), is subjected to a gas carburizing treatment at a carburizing temperature T p ° C. that satisfies Formula (A) for 10 minutes to less than 20 hours; and
a main gas carburizing process, wherein successively following the preliminary gas carburizing process, a gas carburizing treatment is performed at a carburizing temperature T r ° C. that satisfies Formula (B) for a carburizing time t r minutes, wherein
the carburizing temperature T r is higher than the carburizing temperature T p
6.5<3.5[Si %]+[Mn %]+[Cr %]≤18 (1)
800 ≤T p <163×ln( CP+ 0.6)−41×ln(3.5×[Si %]+[Mn %]+3×[Cr %])+950 (A)
4<13340/( T r +273.15)+ln( t r )<7 (B)
where, [Si %], [Mn %], and [Cr %] in the formulae are substituted by the Si content, Mn content, and Cr content in mass % in the steel component, the term ln( ) represents natural logarithm, and CP is substituted by a carbon potential during carburization in the preliminary gas carburizing process.
2. A carburized steel component, comprising:
a base metal having a chemical composition that consists of, by mass %,
C: 0.1 to 0.4%,
Si: 0.7 to 4.0%,
Mn: 0.2 to 3.0%,
Cr: 0.5 to 5.0%,
Al: 0.005 to 0.15%,
S: not more than 0.3%,
N: 0.003 to 0.03%,
O: not more than 0.0050%,
P: not more than 0.025%,
Nb: 0 to 0.3%,
Ti: 0 to 0.3%,
V: 0 to 0.3%,
Ni: 0 to 3.0%,
Cu: 0 to 3.0%,
Co: 0 to 3.0%,
Mo: 0 to 1.0%,
W: 0 to 1.0%,
B: 0 to 0.005%,
Ca: 0 to 0.01%,
Mg: 0 to 0.01%,
Zr: 0 to 0.05%,
Te: 0 to 0.1%, and
rare earth metals: 0 to 0.005%, with the balance being Fe and impurities, and that satisfies Formula (1); and
a carburized layer formed on the base metal, wherein C content of an outer layer of the carburized layer is not less than 0.5%,
Si content, Mn content, and Cr content of the outer layer of the carburized layer satisfy Formula (2),
a depth of effective hardened layer is 0.3 to less than 1.5 mm, and an area fraction of oxide in a depth range of 10±3 μm from the surface of the carburized layer is 7 to 50%:
6.5<3.5[Si %]+[Mn %]+3[Cr %]≤18 (1)
3.5[Sis %]+[Mns %]+3[Crs %]≤9 (2)
where, [Si %], [Mn %], and [Cr %] in Formula (1) are substituted by the Si content, Mn content, and Cr content in mass % in the base metal, respectively, and [Sis %], [Mns %], and [Crs %] in Formula (2) are substituted by the Si content, Mn content, and Cr content in mass % of the outer layer of the carburized layer, respectively.
3. The carburized steel component according to claim 2 , wherein at least one of the following element selected from the group consisting of:
Nb: 0.02 to 0.3%,
Ti: 0.02 to 0.3%, and V: 0.02 to 0.3% is present.
4. The carburized steel component according to claim 3 , wherein
at least one of the following element selected from the group consisting of:
Ni: 0.2 to 3.0%,
Cu: 0.2 to 3.0%,
Co: 0.2 to 3.0%,
Mo: 0.05 to 1.0,%,
W: 0.05 to 1.0%, and B: 0.0006 to 0.005% is present.
5. The carburized steel component according to claim 3 , wherein
at least one of the following element selected from the group consisting of:
Ca: 0.0005 to 0.01%,
Mg: 0.0005 to 0.01%,
Zr: 0.0005 to 0.05%,
Te: 0.0005 to 0.1%, and
rare earth metals: 0.0001 to 0.005% is present.
6. The carburized steel component according to claim 4 , wherein
at least one of the following element selected from the group consisting of:
Ca: 0.0005 to 0.01%,
Mg: 0.0005 to 0.01%,
Zr: 0.0005 to 0.05%,
Te: 0.0005 to 0.1%, and
rare earth metals: 0.0001 to 0.005% is present.
7. The carburized steel component according to claim 2 , wherein
at least one of the following element selected from the group consisting of:
Ni: 0.2 to 3.0%,
Cu: 0.2 to 3.0%,
Co: 0.2 to 3.0%,
Mo: 0.05 to 1.0%,
W: 0.05 to 1.0%, and B: 0.0006 to 0.005% is present.
8. The carburized steel component according to claim 4 , wherein
at least one of the following element selected from the group consisting of:
Ca: 0.0005 to 0.01%,
Mg: 0.0005 to 0.01%,
Zr: 0.0005 to 0.05%,
Te: 0.0005 to 0.1%, and
rare earth metals: 0.0001 to 0.005% is present.
9. The carburized steel component according to claim 2 , wherein
at least one of the following element selected from the group consisting of:
Ca: 0.0005 to 0.01%,
Mg: 0.0005 to 0.01%,
Zr: 0.0005 to 0.05%,
Te: 0.0005 to 0.1%, and
rare earth metals: 0.0001 to 0.005% is present.