Hot rolled steel sheet having an ultrafine grain structure and process for producing steel sheet
AssigneeKawasaki Steel Corporation
InventorsEiko Yasuhara, Akio Tosaka, Osamu Furukimi
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Abstract
A hot rolled steel sheet comprises ultrafine ferrite grains as a main phase and fine second phase particles. The ferrite grains have an average grain size of not less than 2 μm but less than 4 μm. The second phase has an average particle size of not more than 8 μm and in not less than 80% of the second phase, the spacing of the second phase particle with the closest second phase particle is not less than the second phase particle size. The steel sheet has an ultrafine grain structure, superior mechanical characteristics, reduced anisotropy in its mechanical characteristics and high formability. A process for producing the steel sheet is also disclosed.
Claims10
A hot rolled steel sheet having an ultrafine grain structure, comprising ferrite as a main phase and a second phase, said second phase comprising at least one phase selected from the group consisting of pearlite, bainite, martensite and retained austenite, said ferrite having an average grain size of not less than 2 μm but less than 4 μm, said second phase having an average particle size of not more than 8 μm and in not less than 80% of the second phase, the spacing of the second phase particle with the closest second phase particle being not less than the second phase particle size.
A hot rolled steel sheet having an ultrafine grain structure, comprising ferrite as a main phase and a second phase, said ferrite having an average grain size of not less than 2 μm but less than 4 μm, said second phase having an average particle size of not more than 8 μm and in not less than 80% of the second phase, the spacing of the second phase particle with the closest second phase particle being not less than the second phase particle size,
- wherein the hot rolled steel sheet comprising by weight percent:
- C:
- more than 0.01 to 0.3%;
- Si:
- not more than 2.0%;
- Mn:
- not more than 3.0%;
- P:
- not more than 0.5%;
- and
- Ti:
- 0.03 to 0.3%;
- and
- the balance Fe and incidental impurities.
Dependencies are inferred from the claim text.