VAR Ingot Solidification Controller for Pool Shape Feedback
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Solution Overview
Problem
Current vacuum arc remelting (VAR) processes lack effective closed-loop feedback control for ingot pool shape, leading to material defects and inability to manage process upsets that affect pool depth and shape during non-steady state operations.
Innovation Solution
A state-space control method using linearized and reduced-order models of heat conduction and mass conservation equations to directly control ingot pool shape by adjusting melting current and electrode feed rate, incorporating spectral methods for approximate solutions and incorporating feedback from a high-order simulation model to manage pool depth set-points.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If open loop control with indirect pool shape control is used, then device complexity is reduced, but manufacturing precision of ingot pool shape deteriorates
Solution Approach 1:
The patent implements closed-loop feedback control by continuously measuring actual pool depth and shape parameters and comparing them with set-point values. The controller automatically adjusts electrode feed rate and melting current based on the deviation between actual and desired pool characteristics, thereby achieving precise pool shape control while maintaining reasonable system complexity through automated feedback mechanisms.
Solution Approach 2:
The patent replaces indirect mechanical control methods with direct electronic control of pool shape parameters. By using electronic sensors to measure pool depth and shape, and electronically adjusting electrode feed rate and current, the system achieves more precise control compared to traditional mechanical open-loop methods, while the electronic control system manages complexity efficiently.
2Productivity
If constant melt rate control is used, then productivity is maintained, but reliability of pool shape control deteriorates during process upsets
Solution Approach 1:
The controller continuously monitors pool depth and shape parameters and automatically adjusts electrode feed rate and melting current in response to process upsets. This feedback mechanism maintains pool shape stability even when melt rate fluctuations occur, ensuring reliable control during non-steady state operations while preserving overall productivity.
Solution Approach 2:
The patent implements dynamic control that allows the system to adapt to changing conditions during the VAR process. The controller can modify electrode feed rate and current in real-time based on actual pool characteristics, enabling the system to handle process upsets and non-steady state conditions while maintaining productivity through automated adjustments rather than constant manual intervention.
3Manufacturing precision
If high-order mathematical models are used for direct pool shape control, then manufacturing precision is improved, but device complexity increases
Solution Approach 1:
The patent replaces complex high-order mathematical models with an electronic control system that directly adjusts electrode parameters based on measured pool characteristics. This electronic feedback control approach achieves the same pool shape precision as complex mathematical models but with significantly reduced system complexity and easier implementation in practical control 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
Enables precise control of ingot pool shape during steady and non-steady states, reducing material defects and allowing for dynamic optimization of the solidification process, even during process upsets, by providing direct feedback and control over pool depth.
Implementation Method 1
a direct current electrical arc is struck between the electrode (cathode) and some starting material (e.g. metal chips) at the bottom of the crucible (anode). The arc heats and eventually melts both the starting material and the electrode tip.
Implementation Method 2
a molten metal, bowl-shaped pool is located at the very top of the solidified ingot forms due to heat from the electrical arc and dripping liquid metal from the electrode
Data Source
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AI summary
The invention comprises 2-dimensional and 3-dimensional versions of a model-based ingot solidification controller for the vacuum arc remelting process. The invention predicts the pool depth as a function of radial position from ingot certerline and time. Unlike the prior art, the invention provides an effective means of controlling the ingot pool depth through normal process upsets; and is a closed loop system with respect to pool depth or shape. The prior art VAR process control does not respond to process upsets that affect pool shape but not melt rate. A method of closed-loop feedback control of the pool depth/shape allows control of the pool shape directly and in response to process upsets that directly affect solidification. Additionally, the invention allows dynamic control of the pool shape so that process control can be optimized during non-steady state operation at the process' beginning and end.