Metal treatment – Stock – Ferrous
Reexamination Certificate
1999-10-12
2001-06-19
Yee, Deborah (Department: 1742)
Metal treatment
Stock
Ferrous
C148S334000, C148S335000, C420S104000, C420S105000, C420S109000, C420S110000
Reexamination Certificate
active
06248187
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a corrosion resistant steel excellent in resistance to corrosion by carbon dioxide, most suitable for oil well steel pipes and line pipes for production and transportation of gas, petroleum, etc. used in the field of energy, or a steel for plants, and corrosion resistant oil well steel pipes.
BACKGROUND ART
A steel material such as a carbon steel or a low alloy steel is used for oil well steel pipes, line pipes, etc. for the production and transportation of petroleum, gas, and the like. For highly corrosive petroleum and gas wells, a carbon steel, or the like material is used while corrosion inhibitors are added to petroleum, etc., or a stainless steel material such as 13% Cr steel is used as the material itself. A sufficient service period of the oil well steel pipes and line pipes has thus been ensured.
However, use of a stainless steel for oil wells, etc., the life of which is short is overly expensive in terms of cost efficiency because the stainless steel is costly. On the other hand, there is a trend towards avoiding the use of corrosion inhibitors because of their adverse effects on the environment. Accordingly, the development of steel materials capable of ensuring the resistance to corrosion to a certain degree has been expected. In order to answer the expectations, a steel containing 0.5 to 5% of Cr is proposed in Japanese Unexamined Patent Publication (Kokai) No. 57-5846. However, the patent publication merely discloses in examples inventive steels containing from 0.5 to 2.1% of Cr.
Furthermore, when a steel containing Cr is used, the steel must have a good balance between the strength and the low temperature toughness. Although the balance therebetween is greatly influenced by the metallic structure, Japanese Unexamined Patent Publication (Kokai) No. 57-5846 defines no metallic structure of the steel material.
DISCLOSURE OF INVENTION
An object of the present invention is to provide a corrosion resistant steel excellent in resistance to corrosion by carbon dioxide and seawater, most suitable for oil well steel pipes and line pipes for production and transportation of gas, petroleum, etc. used in the field of energy, or a steel for plants, and excellent in strength and low temperature toughness, and corrosion resistant oil well steel pipes.
The present invention is characterized by that the Cr content and the metal structure most suitable for a corrosion resistant steel excellent in resistance to corrosion by carbon dioxide are defined, and provides corrosion resistant steels and corrosion resistant oil well steel pipes as disclosed in (1) to (5) below.
(1) A corrosion resistant steel excellent in resistance to corrosion by carbon dioxide, comprising, based on weight, up to 0.30% of C, up to 1.0% of Si, 0.2 to 2.0% of Mn, 2.1 to less than 5.0% of Cr, up to 0.03% of P, up to 0.02% of S, up to 0.10% of Al, up to 0.015% of N and the balance of Fe and unavoidable impurities, and having a martensitic structure.
(2) A corrosion resistant steel excellent in resistance to corrosion by carbon dioxide, comprising, based on weight, up to 0.30% of C, up to 1.0% of Si, 0.2 to 2.0% of Mn, 2.1 to less than 5.0% of Cr, up to 0.03% of P, up to 0.02% of S, up to 0.10% of Al, up to 0.015% of N, one or more elements selected from Cu, Ni and Mo in an amount of up to 1% and the balance of Fe and unavoidable impurities, and having a martensitic structure.
(3) A corrosion resistant steel excellent in resistance to corrosion by carbon dioxide, comprising, based on weight, up to 0.30% of C, up to 1.0% of Si, 0.2 to 2.0% of Mn, 2.1 to less than 5.0% of Cr, up to 0.03% of P, up to 0.02% of S, up to 0.10% of Al, up to 0.015% of N, one or more of Cu, Ni and Mo in an amount of up to 1%, one or more of 0.001 to 0.2% of Ti, 0.01 to 0.5% of Nb and 0.0005 to 0.003% of B and the balance of Fe and unavoidable impurities, and having a martensitic structure.
(4) The corrosion resistant steel excellent in resistance to corrosion by carbon dioxide according to any one of (1) to (3), wherein the steel has a yield strength of at least 550 MPa.
(5) A corrosion resistant oil well steel pipe characterized by that the oil well steel pipe is produced from the corrosion resistant steel excellent in resistance to corrosion by carbon dioxide according to any one of (1) to (4).
The martensitic structure herein designates an as quench-hardened martensitic structure or a tempered martensitic structure. The martensitic structure is usually tempered to increase the low temperature toughness and give a material having a desired range of strength.
REFERENCES:
patent: 56-93856 (1981-07-01), None
patent: 57-19322 (1982-02-01), None
patent: 10-17980 (1998-01-01), None
Asahi Hitoshi
Nose Koichi
Kenyon & Kenyon
Nippon Steel Corporation
Yee Deborah
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