Steel for carburizing or carbonitriding use
AssigneeNippon Steel & Sumitomo Metal Corporation
InventorYoshihiro Daitoh
Life of this patent
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Abstract
A steel for carburizing or carbonitriding use consisting of, by mass %, C: 0.1 to 0.3%, Si: 0.01 to 0.15%, Mn: 0.6 to 1.5%, S: 0.012 to 0.05%, Cr: 0.5 to 2.0%, Al: 0.030 to 0.050%, Ti: 0.0006 to 0.0025%, N: 0.010 to 0.025%, and O: 0.0006 to 0.0012%, and, optionally, at least one selected from Mo≤0.5%, Ni≤1.5% and Cu≤0.4%, and the balance of Fe and impurities. P and Nb are P≤0.025% and Nb≤0.003% respectively. Formulas of [−5.0≤log (Ti×N)≤−4.4] and [−12.5≤log (Al2×O3)≤−11.7] are satisfied. Austenite grain coarsening is prevented even when the steel is heated in the process of carburizing or carbonitriding, and even under various hot forging temperatures. The steel has excellent bending fatigue strength after carburizing or carbonitriding.
Claims4
A steel for carburizing or carbonitriding use consisting of, by mass %;
- C:
- 0.18 to 0.3%,
- Si:
- 0.01 to 0.09%,
- Mn:
- 0.6 to 1.5%,
- S:
- 0.012 to 0.05%,
- Cr:
- 0.5 to 2.0%,
- Al:
- 0.030 to 0.050%,
- Ti:
- 0.0006 to 0.0025%,
- N:
- 0.010 to 0.025%, and
- O:
- 0.0006 to 0.0012%, and
- the balance of Fe and impurities, wherein P and Nb among the impurities are P:
- 0.025% or less and Nb:
- 0.003% or less respectively,
- and further the following formulas (1) and (2) are satisfied:
- −5.0≤log(Ti×N)≤−4.4 (1),
- −12.5≤log(Al2×O3)≤−11.7 (2),
- wherein each element symbol in the above formulas (1) and (2) represents the content by mass percent of the element concerned.
A steel for carburizing or carbonitriding use consisting of, by mass %;
- C:
- 0.18 to 0.3%,
- Si:
- 0.01 to 0.09%,
- Mn:
- 0.6 to 1.5%,
- S:
- 0.012 to 0.05%,
- Cr:
- 0.5 to 2.0%,
- Al:
- 0.030 to 0.050%,
- Ti:
- 0.0006 to 0.0025%,
- N:
- 0.010 to 0.025%,
- O:
- 0.0006 to 0.0012%, and
- at least one element selected from Mo:
- 0.5% or less, Ni:
- 1.5% or less, and Cu:
- 0.4% or less, and
- the balance of Fe and impurities, wherein P and Nb among the impurities are P:
- 0.025% or less and Nb:
- 0.003% or less respectively,
- and further the following formulas (1) and (2) are satisfied:
- −5.0≤log(Ti×N)≤−4.4 (1),
- −12.5≤log(Al2×O3)≤−11.7 (2),
- wherein each element symbol in the above formulas (1) and (2) represents the content by mass percent of the element concerned.
Dependencies are inferred from the claim text.