High-strength seamless steel pipe for oil well use having excellent resistance to sulfide stress cracking
US9708681B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Dec 18, 2012 |
| Grant date | Jul 18, 2017 |
| Priority date | — |
| Expiry date | Jun 4, 2033 |
Classification
- Technology area (CPC C)Chemistry; Metallurgy
- CPC primaryC21D2221/02
- WIPO fieldMaterials, metallurgy
- WIPO sectorChemistry
Abstract
A seamless steel pipe has a composition containing, by mass %, C: 0.15 to 0.50%, Si: 0.1 to 1.0%, Mn: 0.3 to 1.0%, P: 0.015% or less, S: 0.005% or less, Al: 0.01 to 0.1%, N: 0.01% or less, Cr: 0.1 to 1.7%, Mo: 0.40 to 1.1%, V: 0.01 to 0.12%, Nb: 0.01 to 0.08%, Ti: 0.03% or less, and B: 0.0005 to 0.003%, a structure composed of a tempered martensite phase as a main phase with a prior austenite grain size of 8.5 or more, and a hardness distribution in which in four portions 90° apart from each other in the circumferential direction, hardness is 295 HV10 or less in any one of an inner surface-side region at 2.54 to 3.81 mm from the inner surface of the pipe, an outer surface side-region at the same distance from the outer surface of the pipe, and a center of the thickness.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.