Heat-treated steel material and method of manufacturing the same
AssigneeNippon Steel & Sumitomo Metal Corporation
InventorsShinichiro TABATA, Kazuo HIKIDA, Nobusato KOJIMA, Naomitsu MIZUI
Life of this patent
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Abstract
A heat-treated steel material includes: a chemical composition expressed by, in mass %: C: 0.16% to 0.38%; Mn: 0.6% to 1.5%; Cr: 0.4% to 2.0%; Ti: 0.01% to 0.10%; B: 0.001% to 0.010%; Si: 0.20% or less; P: 0.05% or less; S: 0.05% or less; N: 0.01% or less; Ni: 0% to 2.0%; Cu: 0% to 1.0%; Mo: 0% to 1.0%; V: 0% to 1.0%; Al: 0% to 1.0%; Nb: 0% to 1.0%; REM: 0% to 0.1%; and the balance: Fe and impurities; and a structure expressed by: retained austenite: 1.5 volume % or less; and the balance: martensite.
Claims8
A heat-treated steel material comprising:
- a chemical composition expressed by, in mass %:
- C:
- 0.16% to 0.38%;
- Mn:
- 0.6% to 1.5%;
- Cr:
- 0.4% to 2.0%;
- Ti:
- 0.01% to 0.10%;
- B:
- 0.001% to 0.010%;
- Si:
- 0.20% or less;
- P:
- 0.05% or less;
- S:
- 0.05% or less;
- N:
- 0.01% or less;
- Ni:
- 0% to 2.0%;
- Cu:
- 0% to 1.0%;
- Mo:
- 0% to 1.0%;
- V:
- 0% to 1:0%;
- Al:
- 0% to 1.0%;
- Nb:
- 0% to 1.0%;
- REM:
- 0% to 0.1%;
- and
- the balance:
- Fe and impurities;
- and
- a structure expressed by:
- retained austenite:
- 1.5 volume % or less;
- and
- the balance:
- martensite.
A method of manufacturing a heat-treated steel material, comprising:
- heating a steel sheet to a temperature of an Ac3 point or higher;
- next cooling the steel sheet to a Ms point at a cooling rate equal to a critical cooling rate or more;
- and
- next cooling the steel sheet from the Ms point to 100° C. at a 35° C./second average cooling rate or more, wherein
- the steel sheet comprises a chemical composition expressed by, in mass %:
- C:
- 0.16% to 0.38%;
- Mn:
- 0.6% to 1.5%;
- Cr:
- 0.4% to 2.0%;
- Ti:
- 0.01% to 0.10%;
- B:
- 0.001% to 0.010%;
- Si:
- 0.20% or less;
- P:
- 0.05% or less;
- S:
- 0.05% or less;
- N:
- 0.01% or less;
- Ni:
- 0% to 2.0%;
- Cu:
- 0% to 1.0%;
- Mo:
- 0% to 1.0%;
- V:
- 0% to 1.0%;
- Al:
- 0% to 1.0%;
- Nb:
- 0% to 1.0%;
- REM:
- 0% to 0.1%;
- and
- the balance:
- Fe and impurities.
Dependencies are inferred from the claim text.