High-Strength Seamless Steel Pipe for Toughness and Hydrogen Resistance
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Solution Overview
Problem
Existing seamless steel pipes for airbag accumulators face challenges in achieving high strength, low-temperature toughness, and hydrogen embrittlement resistance while also meeting the demand for weight reduction and environmental recyclability.
Innovation Solution
A seamless steel pipe with a specific chemical composition and production process, including elements like C, Si, Mn, P, S, Cu, Ni, Cr, Mo, Ti, Nb, Ca, Al, N, V, B, Mg, and REM, balanced to achieve a tensile strength of 1200 MPa or more, with low-temperature toughness and hydrogen embrittlement resistance properties, using formulas to optimize element contents and grain size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the tensile strength is increased to 1200 MPa or more to meet weight reduction demands, then the wall thickness can be reduced, but the hydrogen embrittlement resistance deteriorates
Solution Approach 1:
The patent applies parameter changes by precisely controlling the chemical composition parameters (C: 0.05-0.20%, Si: 0.05-0.50%, Mn: 0.40-1.50%, P: 0.025% or less, S: 0.020% or less, Cu: 0.10-0.50%, Ni: 0.10-0.50%, Cr: 0.10-1.20%, Mo: 0.10-0.50%, Ti: 0.005-0.050%, Nb: 0.005-0.100%, Ca: 0.0005-0.0025%, Al: 0.080% or less, N: 0.0100% or less, V: 0-0.100%, B: 0-0.0050%, Mg: 0-0.0050%, REM: 0-0.0050%) and heat treatment parameters (austenitizing temperature: 800-950°C, holding time: 5-30 minutes, cooling rate: 10-50°C/sec) to achieve both high tensile strength (≥1200 MPa) and sufficient hydrogen embrittlement resistance (critical hydrogen concentration: 2.5 ppm or more).
Solution Approach 2:
The patent employs composite material principles by creating a multi-element alloy steel composition that combines the benefits of various elements: C provides strength, Si provides hardenability, Mn provides hardenability and toughness, Cr and Mo provide hardenability and tempering resistance, Ti and Nb provide grain refinement, and Ca controls inclusion morphology. This composite approach allows simultaneous achievement of high strength and hydrogen embrittlement resistance.
2Strength
If the tensile strength is increased to 1200 MPa or more, then the weight can be reduced, but the low-temperature toughness may deteriorate
Solution Approach 1:
The patent applies parameter changes by optimizing the chemical composition (particularly C: 0.05-0.20%, Mn: 0.40-1.50%, Cr: 0.10-1.20%, Mo: 0.10-0.50%, Ti: 0.005-0.050%, Nb: 0.005-0.100%) and heat treatment parameters (austenitizing temperature: 800-950°C, holding time: 5-30 minutes, cooling rate: 10-50°C/sec, tempering temperature: 300-450°C, holding time: 5-30 minutes) to achieve both high tensile strength (≥1200 MPa) and excellent low-temperature toughness (vTrs100: -100°C or lower).
Solution Approach 2:
The patent employs composite material principles by creating a multi-element alloy steel composition that combines the benefits of various elements: C provides strength, Mn provides hardenability and toughness, Cr and Mo provide hardenability and tempering resistance, Ti and Nb provide grain refinement, and Ca controls inclusion morphology. This composite approach allows simultaneous achievement of high strength and low-temperature toughness.
3Strength
If quenching and tempering is used to achieve high strength, then the tensile strength increases, but the production complexity increases
Solution Approach 1:
The patent applies parameter changes by optimizing the heat treatment parameters (austenitizing temperature: 800-950°C, holding time: 5-30 minutes, cooling rate: 10-50°C/sec, tempering temperature: 300-450°C, holding time: 5-30 minutes) to achieve high tensile strength (≥1200 MPa) while maintaining a manageable production process. The specific parameter ranges are designed to achieve the desired strength with standard industrial heat treatment equipment and procedures.
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 seamless steel pipe achieves high strength, excellent low-temperature toughness, and improved hydrogen embrittlement resistance, ensuring reliability and safety in airbag systems.
Implementation Method 1
austenitizing at a temperature of 800 to 950°C for 5 to 30 minutes, followed by rapid cooling at a rate of 10 to 50°C/sec, and then tempering at a temperature of 300 to 450°C for 5 to 30 minutes
Implementation Method 2
rapid cooling at a rate of 10 to 50°C/sec
Implementation Method 3
Ti: 0.005 to 0.050%, Nb: 0.005 to 0.100%
Implementation Method 4
a critical hydrogen concentration of the seamless steel pipe is 2.5 ppm or more
Data Source
AI summary
There is provided a seamless steel pipe that has high strength and excellent low-temperature toughness and has hydrogen embrittlement resistance properties. The seamless steel pipe has a chemical composition described in the specification, and the chemical composition satisfies [5C+Mo+Cr≥1.00], and satisfies [GN−1.96×(Mn+70P+100N)≥7.50] and [GN−1.37×(Mn+85P−30Ca)≥8.90] in conjunction with a prior-y grain size number GN. The seamless steel pipe has a tensile strength of 1200 MPa or more, and a critical hydrogen concentration of 2.5 ppm or more.