Steel pipe having high ductility and high strength and process for production thereof
US6331216A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Dec 30, 1998 |
| Grant date | Dec 18, 2001 |
| Priority date | — |
| Expiry date | Dec 30, 2018 |
Classification
- Technology area (CPC C)Chemistry; Metallurgy
- CPC primaryC21D2211/005
- WIPO fieldMaterials, metallurgy
- WIPO sectorChemistry
Abstract
The steel pipe has a structure composed mainly of ferrite or ferrite plus pearlite or ferrite plus cementite. The steel pipe is characterized by grain size not greater than 3 .mu.m, preferably not greater than 1 .mu.m, elongation greater than 20%, tensile strength (TS:MPa) and elongation (E1:%) whose product is greater than 10000, and percent ductile fracture greater than 95%, preferably 100%, measured by Charpy impact test on an actual pipe at -100.degree. C. The structure is characterized by C: 0.005-0.03%, Si: 0.01-3.0%, Mn: 0.01-2.0%, and Al: 0.001-0.10% on a weight basis, and is composed of ferrite or ferrite and a secondary phase, with ferrite grains being not greater than 3 .mu.m and the secondary phase having an areal ratio not more than 30%. A steel pipe stock having the above-mentioned composition is heated at a temperature of (Ac.sub.1 +50.degree. C.) to 400.degree. C. and subsequently reduced at a rolling temperature of (Ac.sub.1 +50.degree. C.) to 400.degree. C. such that the cumulative reduction of diameter is greater than 20%. The reducing is preferably performed such that at least one of rolling passes reduces the diameter by more than 6% per pass. The steel pipe wi…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.