Seamless steel tube for fuel injection

Patent metadata

Field	Value
Publication number	US-10308994-B2
Application number	US-201515300810-A
Country	US
Kind code	B2
Filing date	Mar 20, 2015
Priority date	Apr 3, 2014
Publication date	Jun 4, 2019
Grant date	Jun 4, 2019

Abstract

A seamless steel tube has a particular composition and a structure with an average prior γ grain size of 150 μm or less in an axial cross-section after cold drawing and heat treatment. The structure retards the growth of a fatigue crack. The steel tube has a tensile strength TS of 500 MPa or more and good internal pressure fatigue resistance and is suitable for use as a fuel injection tube under high injection pressures. The composition of the steel tube may further contain at least one of Cu, Ni, Cr, Mo, and B; at least one of Ti, Nb, and V; and/or Ca.

First claim

The invention claimed is:

1. A seamless steel tube for fuel injection having a composition comprising, by mass, 0.155% to 0.21% C, 0.01% to 0.49% Si, 1.20% to 2.1% Mn, 0.005% to 0.25% Al, and 0.0010% to 0.010% N and containing, as impurities, 0.030% or less P, 0.025% or less S, and 0.005% or less O, the balance being Fe and incidental impurities, the composition satisfying condition (1):
[Al %]×[N %]≤27×10 −5   (1)

wherein Al % and N % are the contents (% by mass) of Al and N, respectively,
the steel tube having a structure with an average prior γ grain size of 150 μm or less in an axial cross-section after cold drawing and heat treatment, and
a tensile strength TS of 500 MPa or more.

2. The seamless steel tube according to claim 1 , wherein the composition further comprises, by mass, at least one of 0.70% or less Cu, 1.00% or less Ni, 1.20% or less Cr, 0.50% or less Mo, and 0.0060% or less B.

3. The seamless steel tube according to claim 1 , wherein the composition further comprises, by mass, at least one of 0.20% or less Ti, 0.050% or less Nb, and 0.20% or less V.

4. The seamless steel tube according to claim 2 , wherein the composition further comprises, by mass, at least one of 0.20% or less Ti, 0.050% or less Nb, and 0.20% or less V.

5. The seamless steel tube according to claim 1 , wherein the composition further comprises, by mass, 0.0040% or less Ca.

6. The seamless steel tube according to claim 2 , wherein the composition further comprises, by mass, 0.0040% or less Ca.

7. The seamless steel tube according to claim 3 , wherein the composition further comprises, by mass, 0.0040% or less Ca.

8. The seamless steel tube according to claim 4 , wherein the composition further comprises, by mass, 0.0040% or less Ca.

Assignees

• Jfe Steel Corp

Inventors

• Kawabata Yoshikazu
• Nishino Manabu
• Gunji Makio

Classifications

• C21D8/10

  during manufacturing of tubular bodies · CPC title

• F02M2200/9053

  Metals · CPC title

• C21D9/08

  for tubular bodies or pipes · CPC title

• C21D8/105

  Chemistry & Metallurgy · mapped topic

• C21D2211/001

  Austenite · CPC title