High-strength hot-rolled steel sheet and method for producing the same
US10301693B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | May 2, 2016 |
| Grant date | May 28, 2019 |
| Priority date | — |
| Expiry date | May 2, 2036 |
Classification
- Technology area (CPC C)Chemistry; Metallurgy
- CPC primaryC22C38/58
- WIPO fieldMaterials, metallurgy
- WIPO sectorChemistry
Abstract
A steel slab having a composition containing C: more than 0.07% and 0.2% or less, Si: 2.0% or less, Mn: 1.0% to 3.0%, Al: 0.1% or less, Ti: 0.05% to 0.3%, and V: 0.05% to 0.3% on a mass percent basis is heated to 1100° C. or more and is subjected to rough rolling and finish rolling. In the finish rolling, the total rolling reduction of two final passes is 30% or more, and the finish rolling temperature ranges from (Ar3 transformation temperature) to (Ar3 transformation temperature+120° C.). Cooling is started within 2 seconds after the finish rolling. Coiling is performed at an average cooling rate of 40° C./s or more at a coiling temperature in the range of 300° C. to 500° C. The resulting high-strength hot-rolled steel sheet has a microstructure in which a bainite phase constitutes more than 90% by volume, the average lath interval of bainite is 0.45 μm or less, and the ratio of Fe-based carbide precipitated in bainite lath to all Fe-based carbide is 10% or more, has a high tensile strength of 900 MPa or more, and has significantly improved punchability in mass production.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.