Vacuum Molten Steel Decarburization Endpoint Using Carbon Estimation
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Solution Overview
Problem
Existing methods for estimating carbon concentration in molten steel during vacuum decarburization refining lack accuracy, particularly in the ultralow carbon concentration range, leading to inefficiencies and prolonged refining times.
Innovation Solution
A decarburization refining method that combines oxygen-blowing and rimmed decarburization treatments, utilizing an oxygen budget and decarburization reaction models to accurately estimate carbon concentration, with equations to calculate carbon removal and determine the end of refining.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If exhaust gas analysis is used to estimate carbon concentration, then carbon content can be monitored during decarburization refining, but estimation accuracy is insufficient particularly in ultralow carbon concentration ranges
Solution Approach 1:
The patent introduces an oxygen potential sensor as an intermediary measurement tool that indirectly reflects carbon concentration through its relationship with the decarburization reaction equilibrium. Instead of directly measuring carbon concentration which is difficult in ultralow ranges, the system measures oxygen potential ([O]) which can be accurately detected and uses it as a proxy indicator. The oxygen potential serves as a mediator that correlates with carbon concentration through the chemical equilibrium relationship, enabling accurate monitoring without direct carbon measurement.
Solution Approach 2:
The patent replaces the mechanical/chemical analysis method (exhaust gas analysis) with an electrical sensing method (oxygen potential measurement). The exhaust gas analysis system relies on physical sampling and chemical analysis instruments with inherent accuracy limitations. The oxygen potential sensor uses electrochemical measurement principles to directly detect the thermodynamic state of the molten steel, providing superior measurement precision especially in ultralow carbon ranges where gas analysis becomes unreliable.
2Manufacturing precision
If decarburization refining is continued to ensure low carbon concentration, then target carbon level can be achieved, but processing time increases and tapping temperature decreases
Solution Approach 1:
The patent implements a feedback control system where the oxygen potential sensor continuously monitors the decarburization process in real-time. The measured oxygen potential values are fed back to the control system, which automatically determines when the target carbon concentration has been reached based on the established relationship between oxygen potential and carbon concentration. This feedback mechanism eliminates the need for operator intuition and prevents over-processing, thereby optimizing both precision and productivity.
Solution Approach 2:
The patent performs preliminary characterization to establish the relationship between oxygen potential and carbon concentration before actual production. Through offline experiments and modeling, the system pre-determines the oxygen potential values corresponding to various carbon concentration levels. This preliminary work enables the online system to quickly and accurately determine endpoint without trial-and-error during actual steelmaking, improving both precision and efficiency.
3Ease of operation
If operator intuition is used to determine end of decarburization, then operation is simple, but determination accuracy is low leading to delayed process completion
Solution Approach 1:
The patent enables the system to determine the endpoint automatically without requiring operator expertise or judgment. The oxygen potential sensor and control system work together to self-determine when decarburization is complete based on pre-established criteria. The system serves itself by automatically interpreting the sensor data and making the endpoint determination, eliminating the need for operators to develop intuition through experience while maintaining ease of operation.
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 determination of the end of decarburization, reducing refining time and improving processing efficiency by accurately estimating carbon concentration in molten steel.
Implementation Method 1
an oxygen-blowing decarburization treatment of blowing an oxidizing gas onto molten steel under reduced pressure to perform a decarburization treatment
Implementation Method 2
a rimmed decarburization treatment of stopping feeding of oxygen sources including the oxidizing gas to the molten steel after the oxygen-blowing decarburization treatment has been performed and of performing a decarburization treatment under reduced pressure
Data Source
AI summary
A decarburization refining method for molten steel under reduced pressure. The method includes an oxygen-blowing decarburization and a rimmed decarburization. Using operation data taken at a time when oxygen-blowing decarburization is started and a time when oxygen-blowing decarburization is ended, an amount of carbon removed while the oxygen-blowing decarburization is performed is estimated. Based on the estimated amount of carbon removed, a carbon concentration in molten steel at a time when the rimmed decarburization is started is estimated. Using the estimated value as the carbon concentration in molten steel at the time when the rimmed decarburization is started, a change over time in the carbon concentration in molten steel while the rimmed decarburization is performed is calculated. Based on the calculated change over time in the carbon concentration in molten steel while the rimmed decarburization is performed, a determination is made about a time when the rimmed decarburization is ended.