Heavy Wall Steel Pipe Cooling for Stable Strength
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Solution Overview
Problem
It is difficult to stably adjust the strength of heavy wall steel pipes with composition A to the target strength of 95 to 140 ksi through a single quenching and tempering (Q-T) operation, as existing methods either increase heat treatment costs or impair weldability and corrosion resistance.
Innovation Solution
A method involving a specific cooling process where a high-temperature steel pipe is dipped in water while rotating, with an axial stream applied to the inside surface and an impinging stream to the outside surface, achieving improved cooling capacity and ensuring quenching is effective to the central portion of the pipe, with specific velocity and timing parameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a single Q-T operation is used for heavy wall steel pipes with composition A, then heat treatment cost is reduced, but strength cannot be stably adjusted to target strength
Solution Approach 1:
The invention changes the cooling parameters by introducing high-velocity water streams (axial stream at 7 m/s or more and impinging stream at 9 m/s or more) to achieve sufficient quenching depth in heavy wall steel pipes during a single Q-T operation, thereby stabilizing strength at target levels while maintaining production efficiency
2Manufacturing precision
If quenching is repeated multiple times to achieve target strength, then strength adjustment precision is improved, but heat treatment cost increases
Solution Approach 1:
The invention modifies the cooling medium parameters by using high-velocity water streams with specific flow rates (axial stream ≥7 m/s, impinging stream ≥9 m/s) to achieve adequate quenching depth in a single operation, eliminating the need for repeated quenching cycles and reducing heat treatment costs
3Strength
If alloy content is increased to improve quench hardenability, then strength is improved, but weldability and corrosion resistance are impaired
Solution Approach 1:
The invention changes the cooling process parameters (water stream velocity, flow rate, application timing) rather than material composition, achieving sufficient quenching depth and target strength (95-140 ksi) without increasing alloy content, thereby preserving weldability and corrosion resistance
Solution Approach 2:
The invention replaces chemical means (alloy addition) with physical means (mechanical water cooling system with optimized flow parameters) to achieve the desired quenching effect and strength levels
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
This method allows for stable adjustment of steel pipe strength to the target range of 95 to 140 ksi with a single Q-T operation, enhancing cooling capacity and maintaining weldability and corrosion resistance.
Implementation Method 1
a cooling water flow (axial stream) is applied to both sides of the steel pipe along the direction of axis
Implementation Method 2
quenching is performed while applying a cooling water flow
Implementation Method 3
heat treatment (Q-T) of seamless steel pipes and electric resistance welded steel pipes, in particular, heavy wall steel pipes
Data Source
Figure 1
AI summary
In the conventional art, it is difficult to stably adjust the strength of a heavy wall steel pipe to a target strength of 95 to 140 ksi (= TS: 655 to 965 MPa) by one Q-T operation. Specifically, a method for manufacturing a heavy wall steel pipe includes a cooling step in which a steel pipe, with a wall thickness of 1/2 inch or more, that has been heated to the gamma range (i.e., austenite region) is dipped in water while supporting and rotating the steel pipe about the axis of pipe, an axial stream which is a water flow in the direction of axis of pipe is applied to the inside surface of the steel pipe under rotation in the water, and an impinging stream which is a water flow impinging on the outer surface of the pipe is applied to the outer surface of the steel pipe under rotation in the water. The rotation is performed at a circumferential velocity of pipe of 4 m/s or more, the application of the axial stream and the impinging stream is started within 1.1 s after the entire steel pipe is dipped, and continued until the temperature of the steel pipe is decreased to 150°C or lower, the pipe flow velocity of the axial stream is set at 7 m/s or more, and the discharge flow velocity of the impinging stream is set at 9 m/s or more.