Research On Molten Steel Liquid Level Measurement Method Based On Slag Ion Characteristics

In the continuous casting production,the tundish molten steel liquid level is one of the important process parameters to ensure the smooth progress of continuous casting production.The real-time measurement and control of the tundish molten steel level has a direct impact on stable casting,prevention of steel leakage accidents,improvement of billet quality and increase of the life of the tundish lining.However,due to the temperature of the tundish steel water up to 1600℃,and the slag of the type and the changing physical form above the molten steel,the existing contactless or non-contact sensors and measurement methods can not be obtained in the application of continuous casting tundish.So the tundish molten steel level measurement is still a difficult problem in the metallurgical process.In this work,based on the difference between the slag ion characteristics and the electronic properties of molten steel,the principle of measuring the molten steel liquid level based on the principle of slag ionic properties is proposed,and the corresponding measurement method is established:electrochemical properties of the medium were obtained using two electrodes of different materials.The electrode forms a galvanic cell in the slag to generate a voltage signal,and only the conduction voltage disappears in the molten steel.The difference between the voltage signals is used to determine the slag-steel interface,combined with the existing laser triangle ranging technology in the laboratory get real-time liquid level of molten steel.Aiming at the measurement method proposed in this article,the following researches are carried out by means of metallurgical field experiments and laboratory simulations:(1)Feasibility verification of molten steel level measurement method based on slag ion characteristics.In order to identify the slag ions and the electronic properties of the molten steel,the anode uses a high melting point inactive metal for conducting the electronic circuit,and the cathode uses a high melting point and a reactive material to generate an oxidation reaction with the slag.In the slag,the electrode and the slag produce a redox reaction to form a galvanic cell,and a voltage signal is generated between the electrodes;in the molten steel,due to the electronic characteristics of the molten steel,the electrode and the molten steel only serve as electron conduction,and the voltage between the electrodes disappears.Therefore,the slagsteel-water interface is determined by the jump of the voltage signal between the electrodes.According to the nature of the metal in the periodic table,the feasibility of the new method is verified in the metallurgical field environment by using electrodes with different melting points and more active materials.The test shows that the method is feasible and applicable.(2)Design of laboratory simulation study scheme for molten steel liquid level measurement method and electrochemical mechanism based on slag ion characteristics.In the laboratory environment,a resistance heating furnace was used to simulate the tundish environment with double-layer corundum.An experimental scheme for different kinds of electrode materials and slag ratio was designed for the universality and reliability of the measurement method.According to the Gibbs free energy spectrum analysis,the electrodes were made of inert metal(tundish)and graphite as experimental reaction cathode materials.The electrode material and the steel slag sample after the end of the experiment were analyzed by electron microscopy and X-ray energy spectroscopy.The morphology of the amplified electrode was combined with the results of the energy spectrum scanning to identify the substances and reactions that specifically participated in the reaction on the electrode surface.The process explains the specific origin of the voltage signal.(3)Study on the electrochemical reaction mechanism of slag-electrode-steel.In the molten steel liquid level measurement experiment of different kinds of electrode materials and slag ratio,the retained electrode sample and the slag-steel water sample were analyzed by electron microscopy and X-ray energy spectroscopy,and the galvanic cell reaction process was obtained:the cathodic reaction was On the surface of the electrode material and the slag,the graphite electrode and the ruthenium electrode themselves lose electrons and become high-valence oxides.The tungsten electrode of the anode material acts as a protective electrode to function as a conducting circuit,and the main reaction occurring on the surface thereof is a process in which electrons become elemental.Since the tungsten electrode itself is also oxidized and dissolved in the slag at a high temperature,a redox reaction with the cathode material is performed to form a tungsten-iron alloy attached to the surface of the cathode material.Graphite as a cathode material will be affected by the tungsten-iron alloy coating to inhibit the electrochemical reaction.The ruthenium electrode is not affected as a cathode material.(4)Research on reliability and accuracy of molten steel liquid level measurement method based on slag ion characteristics.Considering the different slag types and different electrode materials,the reliability and accuracy of the molten steel level measurement are studied by the amplitude of the voltage at the molten steel-slag interface during the electrode lift process.Comparing the performance of the graphite electrode and the ruthenium electrode as cathode materials,it was found that the tundish electrode can see a significant voltage hopping signal amplitude of 200-400 mv during electrode insertion and lifting.As the cathode material,the graphite electrode has a voltage jump of 100-200 mv only when it first drops to the steel slag interface,and the voltage jump is not obvious when it is lifted.The life of the tantalum electrode is also reproducible over the graphite electrode.The tantalum electrode is used as the ideal electrode material,and the measured molten steel liquid level error is±2mm,which verifies the accuracy of the measurement results.The influence of binary alkalinity on the acquisition law of voltage signal is analyzed.The analysis of the influence of binary alkalinity on the acquisition of the voltage signal shows that the electrical signal can be obtained under the acidic,neutral and alkaline conditions of the binary alkalinity of the slag,and it can be obtained when the alkalinity is 2 The electrical signal is stable and the amplitude is large.