Multilayer Slab Casting Control for Boundary Layer Stability
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Solution Overview
Problem
Conventional methods for continuous casting of multilayered slabs fail to accurately control the boundary layer level, leading to potential mixing of molten steel in the surface and inner layers, which affects the quality of the slab.
Innovation Solution
A control method using a molten metal level meter and flowmeter to measure and control the supply flow rates of the surface and inner layers, with a Luenberger-type observer estimating the boundary layer level and adjusting the nozzle stoppers to maintain target values, ensuring precise control of the boundary layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional control methods (injection amount sum operation or indirect level control) are used, then the control system is simple to operate, but the boundary layer level cannot be controlled with high accuracy, leading to potential mixing of molten steel layers
Solution Approach 1:
The patent implements a feedback control system where the boundary layer level is continuously measured (or estimated) and compared with the target level, and the injection amounts of surface layer and inner layer are adjusted based on the deviation to maintain accurate boundary layer level control
Solution Approach 2:
The patent introduces an observer as an intermediary component that estimates the boundary layer level based on measurable quantities (surface layer level and injection amounts) when direct measurement is not available, enabling indirect but accurate control of the boundary layer level
2Reliability
If direct boundary layer level control is implemented, then mixing of molten steel layers is prevented, but the control system becomes more complex requiring precise measurement and adjustment mechanisms
Solution Approach 1:
The control system continuously monitors the boundary layer level (directly or through observer estimation) and adjusts the injection amounts of surface layer and inner layer in real-time to prevent mixing, ensuring reliable layer separation
Solution Approach 2:
The patent replaces direct mechanical measurement of boundary layer level with an observer-based estimation system that uses electrical/electronic sensors (molten metal level meter for surface layer) and flow measurements to calculate the boundary layer level, reducing mechanical complexity
3Manufacturing precision
If injection amounts are adjusted frequently to maintain boundary layer level, then control accuracy is improved, but the response time increases when nozzle clogging or flow rate changes occur
Solution Approach 1:
The feedback control system detects deviations in boundary layer level (or estimated level) caused by nozzle clogging or flow rate changes and immediately adjusts injection amounts to restore the target level, minimizing recovery time
Solution Approach 2:
The observer continuously estimates the boundary layer level in advance, allowing the control system to detect potential mixing conditions before they occur and take corrective action proactively
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 approach allows for accurate control of the boundary layer level, preventing mixing of molten metals and resulting in high-quality multilayered slabs.
Implementation Method 1
a molten metal level meter (9) that measures a surface layer level (y1) that is a position of a molten metal level in the mold
Implementation Method 2
a flowmeter (10) that measures a supply flow rate of the molten metal
Implementation Method 3
a static magnetic field band is formed between a relatively upper molten metal supply position and a relatively lower molten metal supply position in the mold so that a magnetic line extends in a direction perpendicular to a casting direction
Data Source
AI summary
A control method of a continuous casting process is a method that injects molten metal from a surface layer nozzle and an inner layer nozzle into a mold and separates the molten metal of a surface layer and the molten metal of an inner layer, the control method including, using a molten metal level meter that measures a surface layer level and a flowmeter that measures a supply flow rate of the molten metal, estimating a boundary layer level on the basis of a measured value of the surface layer level, a measured value of the supply flow rate of the molten metal, and a calculated value of the supply flow rate of the molten metal, and controlling the supply flow rate of the molten metal of the surface layer nozzle and the supply flow rate of the molten metal of the inner layer nozzle.