Seamless steel tube for fuel injection
AssigneeJfe Steel Corporation
InventorsYoshikazu Kawabata, Manabu Nishino, Makio Gunji
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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.
Claims8
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.
Dependencies are inferred from the claim text.