Seamless Steel Pipe for Steam Injection Yield Strength
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Solution Overview
Problem
Current steel pipes for steam injection in the asphalt extraction process from oil sand lack sufficient high-temperature strength, with yield stresses at 350°C being lower than the required 555 MPa, limiting the use of higher temperature and pressure steam for more efficient asphalt extraction.
Innovation Solution
A seamless steel pipe with a specific chemical composition (C: 0.03-0.08%, Si: 0.05-0.5%, Mn: 1.5-3.0%, Mo: 0.4-1.2%, Al: 0.005-0.100%, Ca: 0.001-0.005%, N: 0.002-0.015%, P: ≤0.03%, S: ≤0.01%, Cu: ≤1.5%, and optional Cr, Nb, Ti, Ni, V) that is water-cooled after hot working, quenched, and tempered to achieve a yield stress of at least 600 MPa at 350°C.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional steel compositions and annealing processes are used, then manufacturing simplicity is maintained, but yield strength at 350°C remains below 555 MPa
Solution Approach 1:
The patent applies parameter changes by optimizing the chemical composition parameters (C: 0.03-0.08%, Si: 0.05-0.5%, Mn: 1.5-3.0%, Mo: 0.4-1.2%, etc.) and heat treatment parameters (water cooling rate, quenching temperature, tempering temperature) to achieve yield strength ≥600 MPa at 350°C, resolving the contradiction between strength improvement and manufacturing complexity
Solution Approach 2:
The patent creates a composite microstructure consisting of martensite and retained austenite through controlled cooling and heat treatment processes. This composite microstructure provides both high strength (martensite) and ductility (retained austenite), achieving yield strength ≥600 MPa at 350°C while maintaining manufacturability
2Productivity
If higher temperature and pressure steam is used, then asphalt extraction efficiency is improved, but the risk of hydrogen-induced cracking and weldability deterioration increases
Solution Approach 1:
The patent changes the chemical composition parameters, particularly controlling C content (0.03-0.08%) to avoid excessive carbide formation that would reduce toughness, while optimizing Mn (1.5-3.0%) and Mo (0.4-1.2%) contents to enhance high-temperature strength and resistance to hydrogen-induced cracking, enabling safer use of higher temperature steam
Solution Approach 2:
The patent prioritizes bulk material properties (chemical composition and microstructure) over complex protective measures, using a cost-effective composition formulation that inherently provides resistance to hydrogen-induced cracking and maintains weldability, avoiding the need for expensive additional protective systems
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 steel pipe achieves enhanced high-temperature strength and toughness, allowing for the use of higher temperature and pressure steam while maintaining weldability and reducing the risk of hydrogen-induced cracking.
Implementation Method 1
water cooling the seamless steel pipe after rolling from a temperature of not lower than the A 3 point to a temperature of 450°C or lower
Implementation Method 2
quenching the water cooled seamless steel pipe from a temperature of higher than the Ac 3 point and at most 1000°C
Implementation Method 3
tempering the quenched seamless steel pipe at a temperature of at most the Ac 1 point
Data Source
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AI summary
There is provided a steel pipe for steam injection having high yield stress even at 350°C. The seamless steel pipe for steam injection according to the present invention has a chemical composition comprising, by mass percent, C: 0.03 to 0.08%, Si: 0.05 to 0.5%, Mn: 1.5 to 3.0%, Mo: more than 0.4 to 1.2%, Al: 0.005 to 0.100%, Ca: 0.001 to 0.005%, N: 0.002 to 0.015%, P: at most 0.03%, S: at most 0.01%, and Cu: at most 1.5%, the balance being Fe and impurities. The seamless steel pipe is manufactured by being water cooled after hot working and by being quenched and tempered.