High-strength seamless steel pipe for oil country tubular goods and method of producing the same
US10876182B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Sep 10, 2015 |
| Grant date | Dec 29, 2020 |
| Priority date | — |
| Expiry date | Dec 26, 2036 |
Classification
- Technology area (CPC C)Chemistry; Metallurgy
- CPC primaryC21D2211/008
- WIPO fieldMaterials, metallurgy
- WIPO sectorChemistry
Abstract
A high-strength seamless steel pipe for oil country tubular goods comprising, by mass %, C: 0.20% to 0.50%, Si: 0.05% to 0.40%, Mn: 0.3% to 0.9%, P: 0.015% or less, S: 0.005% or less, Al: 0.005% to 0.1%, N: 0.006% or less, Mo: more than 1.0% to 3.0% or less, V: 0.01% to less than 0.05%, Nb: 0.001% to less than 0.01%, B: 0.0003% to 0.0030%, O: 0.0030% or less, and Ti: 0.003% to 0.025%, and wherein Ti/N: 2.0 to 5.0 is satisfied, a volume fraction of a tempered martensitic is 95% or more, prior austenite grains have a grain size number of 8.5 or more, and in a cross-section perpendicular to a rolling direction, the number of nitride-based inclusions having a grain size of 4 μm or more is 100 or less per 100 mm2, the number of nitride-based inclusions having a grain size of less than 4 μm is 1000 or less per 100 mm2, the number of oxide-based inclusions having a grain size of 4 μm or more is 40 or less per 100 mm2, and the number of oxide-based inclusions having a grain size of less than 4 μm is 400 or less per 100 mm2.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.