STEEL TUBE FOR HIGH-PRESSURE FUEL LINE AND METHOD OF ITS PRODUCTION Russian patent published in 2011 - IPC F02M55/02 F16L19/02 C21D6/00 

FIELD: engines and pumps.

SUBSTANCE: proposed steel tube contains the following elements in wt %: Ca - 0.12-0.27; Si - 0.05-0.40; Mn - 0.8-2.0%, Fe and impurities making the rest. Note here that said impurities contain in wt %: Ca - 0001 or less, P - 0.02 or less and S - 0.01 or less. Note here that ultimate strength makes at least 900 N/mm² while maximum diametre of nonmetallic inclusions at depth of at least 20 mcm from steel tube surface doe not exceed 20 mcm. Besides steel tube may contain one or more of following elements in wt %: Cr - 1% or less, Mo - 1% or less, Ti - 0.04% or less, Nb - 0.04 or less and V - 0.1% or less. Proposed method comprises the following stages: steel tube is first quenched at temperature not lower that that of Ac₃ phase transition and tempered after quenching at temperature not higher than Ac₁ phase transition temperature.

EFFECT: longer life, higher resistance and reliability.