STEEL PIPE FOR HIGH-PRESSURE FUEL PIPE AND HIGH-PRESSURE FUEL PIPE COMPRISING IT

摘要

FIELD: metallurgy.;SUBSTANCE: invention relates to metallurgy. To ensure high reliability, the steel pipe for a high-pressure fuel pipe has the following chemical composition, mass%: C from 0.12 to 0.27, Si from 0.05 to 0.40, Mn from 0.3 to 2.0, Al from 0.005 to 0.060, N from 0.0020 to 0.0080, Ti from 0.005 to 0.015, Nb from 0.015 to 0.045, Cr from 0 to 1.0, Mo from 0 to 1.0, Cu from 0 to 0.5, Ni from 0 to 0.5, V from 0 to 0.15, B from 0 to 0.005, Fe and impurities are the rest, content of Ca, P, S and O in impurities is, mass%: Ca 0.001 or less, P 0.02 or less, S 0.01 or less, O 0.0040 or less, and also has a metal microstructure consisting of a tempered martensitic structure or a mixed martensite structure of tempering and tempered bainite, in which the size of the preceding austenite grain is 10.0 or more, the steel pipe having a tensile strength of TS 800 MPa or more, and its critical internal pressure is [0.3 × TS × α] or more, where α= [(D/d)^2-1]/[0.776 × (D/d)²], D: outer diameter of the steel pipe (mm) and d: internal diameter of the steel pipe (mm).;EFFECT: providing high reliability steel pipe for high pressure fuel pipe.;4 cl, 5 tbl