Petroleum Casing Composition for Online Quenching Without Cracking
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Solution Overview
Problem
Existing seamless steel pipes for oil and gas wells face issues of high energy consumption, resource waste, and cracking risks during quenching due to complex stress states and large grain sizes, despite using processes like hot rolling and quenching/tempering, which are inefficient and costly.
Innovation Solution
A high-strength petroleum casing pipe with optimized chemical compositions (C: 0.06-0.15%, Si: 0.3-0.5%, Mn: 1.5-2.2%, La+Ce: 0.002-0.006%, Ti≤0.05%, Al: 0.01-0.03%, N≤0.008%) and a manufacturing process utilizing residual heat for online quenching and tempering, avoiding offline quenching steps to reduce costs and energy consumption while enhancing toughness and strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If offline quenching and tempering heat treatment is used after hot rolling, then steel strength is improved, but energy consumption increases and production efficiency decreases
Solution Approach 1:
The patent combines the quenching and tempering heat treatment processes into a single integrated online heat treatment step performed immediately after hot rolling, while the steel pipe is still at high temperature. This merging of processes eliminates the need for separate offline quenching and tempering operations, reducing energy consumption and improving production efficiency while maintaining the required steel strength.
Solution Approach 2:
The patent performs quenching and tempering heat treatment while the steel pipe is still at high temperature from hot rolling, before the steel cools down to room temperature. This preliminary action utilizes the residual heat from hot rolling, avoiding the need to reheat the steel for separate offline heat treatment, thereby reducing energy consumption and improving production efficiency.
2Productivity
If online quenching is used to reduce energy consumption, then production efficiency improves, but cracking risk increases due to complex stress state and large grain size
Solution Approach 1:
The patent optimizes the chemical composition parameters of the steel, specifically controlling carbon content at 0.06-0.15% and carbon equivalent at 0.38-0.48%, to achieve appropriate hardenability. This parameter optimization allows the steel to undergo online quenching without excessive hardening that would cause cracking, while still achieving the required strength and production efficiency.
Solution Approach 2:
The patent uses a composite alloying system containing C, Si, Mn, La, Ce, Ti, and Al elements in specific proportions. This composite material approach creates a synergistic effect where the combination of elements provides both the hardenability needed for online quenching and the toughness required to prevent cracking, resolving the contradiction between production efficiency and reliability.
3Strength
If high carbon equivalent steel is used to achieve high strength, then steel strength improves, but susceptibility to quenching cracking increases
Solution Approach 1:
The patent precisely controls the carbon equivalent parameter within the range of 0.38-0.48%, avoiding excessive carbon content that would increase cracking susceptibility. This parameter optimization allows the steel to achieve high strength through online quenching and tempering while maintaining sufficient toughness to resist quenching cracks.
Solution Approach 2:
The patent introduces rare earth elements (La and Ce) as intermediary elements that modify the steel's microstructure and improve its hardenability. These intermediary elements enable the steel to achieve high strength with lower carbon equivalent, thereby reducing susceptibility to quenching cracking while maintaining production efficiency.
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 achieves high yield strength (552-965 MPa), tensile strength (≥689 MPa), elongation (≥20%), and transverse Charpy impact energy (≥80 J), ensuring efficient production with improved mechanical properties and reduced environmental impact.
Implementation Method 1
After hot rolling, they need to be cooled to room temperature and then reheated in a quenching heating furnace for quenching heat treatment
Implementation Method 2
This process not only wastes the residual heat of the steel pipe after rolling (the temperature of the steel pipe after rolling is usually 900° C. or higher)
Implementation Method 3
online quenching+tempering heat treatment
Data Source
AI summary
Disclosed is a high-strength petroleum pipe casing, which contains Fe and inevitable impurity elements, and further contains the following chemical elements in percentage by mass: 0.06-0.15% of C, 0.3-0.5% of Si, 1.5-2.2% of Mn, 0.002-0.006% of rare earth (La, Ce), less than or equal to 0.05% of Ti, 0.01-0.03% of Al, and greater than 0 but less than or equal to 0.008% of N. Correspondingly, also disclosed is a manufacturing method for the high-strength petroleum pipe casing. The manufacturing method comprises the steps: (1) smelting and casting; (2) perforation; (3) rolling; (4) sizing; (5) online quenching: controlling the temperature of the pipe casing body before cooling to be not lower than 780° C.; water cooling the outer surface of the pipe casing, the cooling speed being 40-100° C./s, and controlling the final cooling temperature to be not higher than 100° C.; (6) tempering, wherein the tempering temperature is controlled to be 500-620° C., and the heat preservation time is 40-70 min; and (7) hot straightening.