Case hardening steel with excellent fatigue properties
AssigneeNippon Steel & Sumitomo Metal Corporation
InventorsMasayuki Hashimura, Masafumi Miyazaki, Takashi Fujita, Hideaki Yamamura
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Abstract
A case hardening steel includes as a chemical composition, by mass %, C: 0.10% to 0.40%, Si: 0.01% to 0.80%, Mn: 0.1% to 1.5%, Cr: 0.35% to 2.0%, Al: 0.01% to 0.05%, REM: 0.0001% to 0.050%, O: 0.0001% to 0.0030%, Ca: 0.0050% or less as necessary, Ti: less than 0.005%, N: 0.015% or less, P: 0.03% or less, S: 0.01% or less, and the balance consists of Fe and impurities. The case hardening steel also includes a composition inclusion which is an inclusion containing REM, O, S, and Al, or an inclusion containing REM, Ca, O, S, and Al, to which TiN is adhered.
Claims3
A case hardening steel comprising as a chemical composition, by mass %:
- C:
- 0.10% to 0.40%;
- Si:
- 0.01% to 0.80%;
- Mn:
- 0.1% to 1.5%;
- Cr:
- 0.35% to 2.0%;
- Al:
- 0.01% to 0.05%;
- REM:
- 0.0001% to 0.050%;
- O:
- 0.0001% to 0.0030%;
- Ti:
- less than 0.005%;
- N:
- 0.015% or less;
- P:
- 0.03% or less;
- S:
- 0.01% or less;
- and
- the remainder comprising Fe and impurities,
- wherein the case hardening steel includes a composite inclusion which is an inclusion containing REM, O, S, and Al, to which TiN is adhered, and
- the sum of a number density of TiN having a maximum diameter of 1 μm or more which independently exists without adhesion to the inclusion, and a number density of MnS having a maximum diameter of 10 μm or more is 5 pieces/mm2 or less.
A case hardening steel comprising as a chemical composition, by mass %:
- C:
- 0.10% to 0.40%;
- Si:
- 0.01% to 0.80%;
- Mn:
- 0.1% to 1.5%;
- Cr:
- 0.35% to 2.0%;
- Al:
- 0.01% to 0.05%;
- Ca:
- 0.0050% or less;
- REM:
- 0.0001% to 0.050%;
- O:
- 0.0001% to 0.0030%;
- Ti:
- less than 0.005%;
- N:
- 0.015% or less;
- P:
- 0.03% or less;
- S:
- 0.01% or less;
- and
- the remainder comprising Fe and impurities,
- wherein the case hardening steel includes a composite inclusion which is an inclusion containing REM, Ca, O, S, and Al, to which TiN is adhered, and
- the sum of a number density of TiN having a maximum diameter of 1 μm or more which independently exists without adhesion to the inclusion, and a number density of MnS having a maximum diameter of 10 μm or more is 5 pieces/mm2 or less.
Dependencies are inferred from the claim text.