Fuel Injection Steel Pipe Fatigue Life via Inclusion Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Steel pipes for fuel injection in diesel engines face challenges in achieving high tensile strength while maintaining adequate internal pressure fatigue resistance, leading to reduced critical internal pressure and fatigue life, especially when subjected to high internal pressures.
Innovation Solution
The development of steel pipes with a specific chemical composition (C: 0.12-0.27%, Si: 0.05-0.40%, Mn: 0.8-2.0%, and optional Cr, Mo, Ti, Nb, V, with impurities limited) and a manufacturing process involving quenching and tempering after final cold drawing, which restricts the size of nonmetallic inclusions near the inner surface to prevent fatigue fractures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the tensile strength of steel pipe material is increased to meet high internal pressure requirements, then the material strength is enhanced, but the fatigue life is reduced due to decreased critical internal pressure
Solution Approach 1:
The patent applies parameter changes by precisely controlling the chemical composition parameters (C: 0.12-0.27%, Si: 0.05-0.40%, Mn: 0.80-2.00%, and optional Cr, Mo, Ti, Nb, V) and processing parameters (quenching temperature Ac3+30℃ to Ac3+1150℃, tempering temperature 200-650℃) to achieve a tensile strength of ≥900 MPa while maintaining fatigue resistance through optimized material properties
Solution Approach 2:
The patent applies local quality by controlling the distribution and size of nonmetallic inclusions specifically near the inner surface of the pipe, restricting inclusion size to prevent fatigue fracture initiation at this critical location while maintaining overall material strength through the specified chemical composition and heat treatment
2Duration of action of stationary object
If the critical internal pressure is reduced to extend fatigue life, then the fatigue life is prolonged, but the steel pipe cannot withstand high internal pressures required for reducing black smoke emissions
Solution Approach 1:
The patent simultaneously optimizes multiple parameters including chemical composition (C, Si, Mn, Cr, Mo, Ti, Nb, V contents), heat treatment parameters (quenching temperature Ac3+30℃ to Ac3+1150℃, tempering temperature 200-650℃), and inclusion size control to achieve both high critical internal pressure (≥900 MPa tensile strength) and extended fatigue life
Solution Approach 2:
The patent creates a composite microstructure through controlled alloying and heat treatment, combining multiple elements (C, Si, Mn, Cr, Mo, Ti, Nb, V) in specific proportions to achieve a microstructure that provides both high strength and fatigue resistance, effectively creating a material with superior combined properties
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution provides steel pipes with a tensile strength of not lower than 900 N/mm² and enhanced internal pressure fatigue resistance, effectively increasing the critical internal pressure and reducing the likelihood of fatigue fractures, thereby reducing black smoke emissions and CO₂ emissions from diesel engines.
Implementation Method 1
a manufacturing process involving quenching and tempering after final cold drawing
Data Source
AI summary
There is provided a steel pipe for fuel injection pipe that assures prolonged fatigue life and high reliability by securing a high critical internal pressure, at which fatigue fracture does not occur, while the material strength is high. A steel pipe for fuel injection pipe consisting of, by mass percent, C: 0.12 to 0.27%, Si: 0.05 to 0.40%, and Mn: 0.8 to 2.0%, the balance being Fe and impurities, the impurities containing Ca: 0.001% or less, P: 0.02% or less, and S: 0.01% or less, wherein the tensile strength thereof is not lower than 900 N/mm2, and the maximum diameter of a nonmetallic inclusion present during at least 20 µm depth from the inner surface of the steel pipe is not larger than 20 µm. Further, this steel pipe can contain one or more kinds of Cr: 1% or less, Mo: 1% or less, Ti: 0.04% or less, Nb: 0.04% or less, and V: 0.1% or less.