# US 8,147,623 B2 · Steel pipe as fuel injection pipe

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- Number: US 8,147,623 B2
- Document ID: US8147623B2
- Status: Granted
- Kind: B2
- Application number: 12/244,641
- Filed: 2008-10-02
- Published: 2009-03-26
- Granted: 2012-04-03
- Earliest claimed: 2006-04-13
- Assignees: Sumitomo Metal Industries, Ltd.
- Inventors: Kikuo Asada; Osamu Endo; Katsunori Nagao; Keisuke Hitoshio
- Web page: https://patentgrep.com/patent/US8147623B2

## CPC

- C22C 38/02: containing silicon
- C21D 8/10: during manufacturing of tubular bodies
- C21D 9/08: for tubular bodies or pipes
- C21D 9/14: wear-resistant or pressure-resistant pipes
- C22C 38/04: containing manganese
- F02M 55/02: Conduits between injection pumps and injectors {, e.g. conduits between pump and common-rail or conduits between common-rail and injectors}
- F02M 61/166: {Selection of particular materials}
- C21D 2211/004: Dispersions; Precipitations
- F02M 2200/03: Fuel-injection apparatus having means for reducing or avoiding stress, e.g. the stress caused by mechanical force, by fluid pressure or by temperature variations
- F02M 2200/9053: Metals
- Y10S 148/909: Tube
- C22C: ALLOYS (treatment of alloys C21D, C22F)
- C21D: MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING (surface treatment of metallic material involving at least one process provided for in class C23 and at least one process covered by this subclass C23F17/00; unidirectional solidification of eutectic materials or unidirectional demixing of eutectoid materials C30B)
- F02M: SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
- Y10S: TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS

## Abstract

To provide a steel pipe as a fuel injection pipe with high material strength, high internal pressure limit free from fatigue failure, prolonged fatigue life, and high reliability. A steel pipe as a fuel injection pipe of 500 N/mm2 or higher tensile strength comprising, by mass, C: 0.12 to 0.27%, Si: 0.05 to 0.40%, and Mn: 0.8 to 2.0%, and the balance being Fe and impurities, the contents of Ca, P, and S in the impurities being Ca: 0.001% or less, P: 0.02% or less, and S: 0.01% or less, respectively, characterized in that the maximum diameter of nonmetallic inclusions present in at least in a region extending from the inner surface of the steel pipe to a depth of 20 μm is 20 μm or less. Further, this steel pipe may contain, in place of a portion of Fe, at least one selected from among Cr: 1% or less, Mo: 1% or less, Ti: 0.04% or less, Nb: 0.04% or less, and V: 0.1% or less.

## Claims

### Claim 1

A seamless steel pipe as a fuel injection pipe, consisting essentially of:
by mass, C: 0.12 to 0.27%, Si: 0.05 to 0.40%, and Mn: 0.8 to 2.0%, and the balance being Fe and impurities, the contents of Ca, P, and S in the impurities being Ca: 0.001% or less, P: 0.02% or less, and S: 0.01% or less, respectively,
wherein the steel pipe has a tensile strength of 500 N/mm2 or higher and the microstructure of the steel pipe comprises bainite and ferrite; and
wherein the maximum diameter of nonmetallic inclusions present in at least in a region extending from the inner surface of the steel pipe to a depth of 20 μm is 20 μm or less.

### Claim 2 (depends on 1)

The seamless steel pipe as a fuel injection pipe according to claim 1, further containing, in place of a portion of Fe, at least one selected from among Cr: 1% or less, Mo: 1% or less, Ti: 0.04% or less, Nb: 0.04% or less, and V: 0.1% or less.