Method and system for controlling refining slag components in steelmaking refining process

Abstract

The invention discloses a control method and system for refining slag components in the steelmaking refining process, and the method comprises the steps: determining target components of a smelted steel grade, and calculating the types of inclusions stably existing in the steel grade; according to the target components and the types of the inclusions, the target components of the refining slag are determined, and then the physical property parameters of the refining slag are obtained; and determining the total mass of the refining slag by combining the physical property parameters of the refining slag. According to the invention, the operation process of production is simplified, the production efficiency of smelting is improved, the quality grade of products is improved, and the production cost of enterprises is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of metallurgy, and in particular to a method and system for controlling the composition of refined slag in a steelmaking and refining process. Background Art

[0002] The steelmaking and refining process of iron and steel metallurgy is an important link that determines the quality of steel products, and involves many operating processes. Steelmaking is usually carried out in a converter. After the steelmaking is completed, the molten steel needs to be transferred from the converter to the ladle container. This process is called converter tapping. Because steelmaking is a process of blowing oxygen into the molten steel for decarburization, which results in excessive oxygen remaining in the molten steel, and the converter slag has a high oxidizing property, that is, the FeO and MnO content is high, and it cannot be used directly as refined slag. Therefore, in the converter tapping process, it is necessary to add an oxygen control agent to the molten steel to reduce the oxygen content in the molten steel, and at the same time add a large amount of slag-making agents and modifiers to make new refined slag. Commonly used oxygen control agents include aluminum blocks, ferrosilicon, etc., and commonly used slag materials include pre-melted slag, lime, fluorite, etc.

[0003] The steelmaking and refining process cannot guarantee that the composition of the molten steel is exactly the same when each converter is tapped due to factors such as the original molten iron composition and the converter blowing time. In addition, the target composition of different steel grades is also different. These factors determine that the amount of alloy and slag added to the molten steel must also be different. The traditional method often uses a fixed slag composition, that is, all steel grades use the same refining slag system composition, fix the slag amount and alloy amount during the converter tapping process, and gradually adjust the refined slag composition to reach the target composition by adding a small amount of material multiple times during the refining process. Each time the material is added, it takes time to melt and mix, which prolongs the refining time and reduces efficiency. Therefore, the traditional method has the shortcomings and disadvantages of long feeding cycle, low refining efficiency, large fluctuation of refining slag composition, and high consumption of raw material energy. Summary of the invention

[0004] In order to solve the above technical problems, the present invention proposes a method and system for controlling the composition of refined slag in the steelmaking and refining process, which can realize the one-time addition of slag in the converter steelmaking process, hit the target composition of refined slag, simplify the production operation process, and improve the production efficiency of smelting.

[0005] On the one hand, to achieve the above-mentioned purpose, the present invention provides a method for controlling the composition of refined slag in a steelmaking and refining process, comprising:

[0006] Determine the target composition of the steel grade to be smelted and calculate the types of inclusions that are stable in the steel grade;

[0007] Determine the target composition of refined slag according to the target composition and the type of inclusions, and then obtain the physical property parameters of refined slag;

[0008] The total mass of the refined slag is determined based on the physical properties of the refined slag.

[0009] Preferably, the process of calculating the types of inclusions that are stably present in the steel grade is:

[0010] The equilibrium concentration of the steel-inclusion interface is obtained through the target composition in the smelting steel grade, and the equilibrium concentration of the steel-inclusion interface and the time are respectively derived to obtain the type of inclusions;

[0011] When the calculation time reaches a preset value, the inclusion composition no longer changes significantly, that is, the stably existing inclusion type is obtained.

[0012] Preferably, the equilibrium concentration of the steel-inclusion interface is:

[0013]

[0014]

[0015] Where, [M] * and [O] * is the concentration of component M and oxygen in the boundary layer of molten steel, wt%; [M] b is the concentration of component M in the molten steel, wt%; is the concentration of slag phase components, wt%; v M and v O are the stoichiometric numbers of component M and oxygen element respectively; F M is the definition constant; E M is the apparent equilibrium constant; ρ slag(inc) is the slag phase density, kg / m 3 ρ steel is the density of molten steel, kg / m 3 ; k is the mass transfer coefficient, m / s; M is the molar mass, kg / mol; k M is the mass transfer coefficient of component M, m / s; M M is the molar mass of component M, kg / mol.

[0016] Preferably, the process of determining the target composition of refined slag is:

[0017] According to the composition of the inclusion types, the composition and basicity of the refined slag are set to obtain the target composition of the refined slag, and the physical property parameters of the refined slag are obtained by calculation;

[0018] The physical property parameters of the refined slag include density, viscosity, sulfur control index, the ability of the refined slag to dissolve inclusions, and the rate at which the refined slag dissolves inclusions.

[0019] Preferably, the process of determining the total mass of the refined slag is:

[0020] Combined with the requirements of oxygen, nitrogen and sulfur control, the amount of fluorite and pre-melted slag added is fixed, and then the amount of aluminum block added and the amount of lime used are determined, and the slag amount is calculated to see if it meets the requirements. If it does not meet the requirements, lime and pre-melted slag are used to make up for it;

[0021] The amount of aluminum block added is the sum of the amount of aluminum alloy element added in the steel, the amount of aluminum added for deoxidation, the amount of aluminum added for slag reforming, and the amount of aluminum added for secondary oxidation consumption.

[0022] On the other hand, in order to achieve the above object, the present invention also provides a control system for controlling the composition of refined slag in the steelmaking and refining process, comprising:

[0023] Composition determination module: used to calculate the types of inclusions that are stable in the steel grade through the target composition of the smelted steel grade;

[0024] Refined slag physical property parameter determination module: used to determine the target composition of the refined slag according to the target composition and the type of inclusions, and then obtain the physical property parameters of the refined slag;

[0025] Refined slag total mass output module: used to determine the total mass of the refined slag in combination with the physical property parameters of the refined slag.

[0026] Preferably, the composition determination module includes an inclusion type determination unit, which is used to obtain the steel-inclusion interface equilibrium concentration through the target composition in the smelting steel grade, and to perform derivative calculations on the steel-inclusion interface equilibrium concentration and time respectively to obtain the inclusion type;

[0027] When the calculation time reaches the preset value, the inclusion composition no longer changes significantly, that is, the stably existing inclusion type is obtained.

[0028] Preferably, the refined slag physical property parameter determination module is used to set the composition and basicity of the refined slag according to the composition of the inclusion types, obtain the target composition of the refined slag, and obtain the physical property parameters of the refined slag by calculation;

[0029] The physical property parameters of the refined slag include density, viscosity, sulfur control index, the ability of the refined slag to dissolve inclusions, and the rate at which the refined slag dissolves inclusions.

[0030] Preferably, the refined slag total mass output module fixes the amount of fluorite and pre-melted slag added by combining the requirements of oxygen control, nitrogen control and sulfur control, and then determines the amount of aluminum block added and the amount of lime used, and calculates whether the slag amount meets the requirements. If it does not meet the requirements, lime and pre-melted slag are used to make up the difference;

[0031] The amount of aluminum block added is the sum of the amount of aluminum alloy element added in the steel, the amount of aluminum added for deoxidation, the amount of aluminum added for slag reforming, and the amount of aluminum added for secondary oxidation consumption.

[0032] The present invention also provides a computer device, comprising a memory, a processor and a computer program stored in the memory, wherein the processor executes the computer program to implement the steps of the control method.

[0033] Compared with the prior art, the present invention has the following advantages and technical effects:

[0034] (1) The present invention determines the target composition of the refining slag system based on the stable inclusions present in the molten steel, and at the same time considers the reactivity between the steel industry and the refining slag, so as to give full play to the functions of the refining slag in adsorbing and removing inclusions and controlling sulfur;

[0035] (2) The present invention adjusts the total mass of the refined slag in real time by considering whether there is a need for sulfur control, oxygen control, and nitrogen control in the refining process, thereby effectively utilizing the metallurgical effect of the refined slag and reducing raw material consumption;

[0036] (3) The present invention changes the current situation of fixed amounts of slag and alloy added during the converter steel-making process, and calculates the amounts of alloy and slag added during the converter steel-making process for each furnace according to the smelting conditions, thereby reducing the number of times materials are added to fine-tune the steel and slag compositions and the number of times electrodes are energized during the refining process, thereby improving the refining efficiency and the refining slag endpoint hit rate and reducing energy consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The drawings constituting a part of the present application are used to provide a further understanding of the present application. The illustrative embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0038] Figure 1 The present invention is a flow chart of a method for controlling the composition of refined slag in a steelmaking and refining process according to an embodiment of the present invention. DETAILED DESCRIPTION

[0039] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0040] It should be noted that the steps shown in the flowcharts of the accompanying drawings can be executed in a computer system such as a set of computer executable instructions, and that, although a logical order is shown in the flowcharts, in some cases, the steps shown or described can be executed in an order different from that shown here.

[0041] First, a brief description of steelmaking and its process:

[0042] Steelmaking refers to controlling the carbon content (generally less than 2%), eliminating harmful elements such as P, S, O, and N, retaining or increasing beneficial elements such as Si, Mn, Ni, and Cr, and adjusting the ratio between elements to obtain optimal performance.

[0043] The steelmaking process includes:

[0044] Charging: The operation of adding raw materials such as molten iron or scrap steel into an electric furnace or a converter is the first step in the steelmaking operation.

[0045] Slag making: The operation of adjusting the composition, basicity, viscosity and reactivity of slag in steel and iron production. The purpose is to smelt metal with the required composition and temperature through slag-metal reaction. For example, in oxygen top-blown converter slag making, the oxygen blowing operation is to generate slag with sufficient fluidity and basicity, which can transfer enough oxygen to the metal surface, so as to reduce sulfur and phosphorus to below the upper limit of the planned steel grade, and minimize the amount of splashing and slag overflow during oxygen blowing.

[0046] Slag discharge: The slag discharge or slag removal operation adopted during the smelting process according to different smelting conditions and purposes in electric arc furnace steelmaking. For example, when using the single slag method for smelting, the oxidized slag must be removed at the end of oxidation; when using the double slag method to make reducing slag, the original oxidized slag must be completely discharged to prevent phosphorus reversion, etc.

[0047] Molten pool stirring: supplying energy to the metal molten pool to make the molten metal and slag move, so as to improve the kinetic conditions of metallurgical reactions. Molten pool stirring can be achieved by means of gas, mechanical, electromagnetic induction and other methods.

[0048] Dephosphorization: A chemical reaction that reduces the phosphorus content in molten steel. Phosphorus is one of the harmful impurities in steel. Steel with a high phosphorus content is prone to brittle cracking when used at room temperature or lower temperatures, which is called "cold brittleness". The higher the carbon content in the steel, the more severe the brittleness caused by phosphorus. Generally, the phosphorus content in ordinary steel is specified to be no more than 0.045%, and high-quality steel requires even less phosphorus. The phosphorus in pig iron mainly comes from phosphates in iron ore. The thermodynamic stability of phosphorus oxide and iron oxide is similar. Under the reducing conditions of the blast furnace, almost all of the phosphorus in the charge is reduced and dissolved into the molten iron. If mineral processing cannot remove phosphorus compounds, dephosphorization can only be carried out outside the (blast) furnace or in an alkaline steelmaking furnace.

[0049] Bottom blowing of electric furnace: N2, Ar, CO2, CO, CH4, O2 and other gases are blown into the furnace molten pool according to the process requirements through the nozzle placed at the bottom of the furnace to accelerate melting and promote the metallurgical reaction process. The bottom blowing process can shorten the smelting time, reduce power consumption, improve dephosphorization and desulfurization operations, increase the residual manganese content in steel, and increase the metal and alloy recovery rate. It can also make the composition and temperature of molten steel more uniform, thereby improving steel quality, reducing costs and increasing productivity.

[0050] Melting period: The melting period of steelmaking mainly refers to open-hearth furnace and electric furnace steelmaking. The melting period of electric arc furnace steelmaking is from the start of power-on to the melting of all the furnace materials, and the melting period of open-hearth furnace steelmaking is from the addition of molten iron to the melting of all the furnace materials. The task of the melting period is to melt and heat the furnace materials as quickly as possible and to make the slag for the melting period.

[0051] Oxidation period and decarburization period: The oxidation period of ordinary power electric arc furnace steelmaking usually refers to the process stage from melting and cleaning of furnace charge, sampling and analysis to removing slag. Some people also believe that it starts from oxygen blowing or adding ore for decarburization. The main tasks of the oxidation period are to oxidize carbon and phosphorus in molten steel; remove gas and inclusions; and heat the molten steel evenly. Decarburization is an important operation process in the oxidation period. In order to ensure the purity of steel, the decarburization amount is required to be greater than about 0.2%. With the development of refining technology outside the furnace, most of the oxidation refining of electric arc furnaces has been moved to ladles or refining furnaces.

[0052] Refining period: The process of steelmaking in which some elements and compounds that are harmful to the quality of steel are removed from the molten steel through slag making and other methods, which are selected into the gas phase or discharged or floated into the slag through chemical reactions.

[0053] Reduction period: In the steelmaking operation of ordinary power electric arc furnace, the period from the end of oxidation to steel tapping is usually called the reduction period. Its main task is to make reducing slag for diffusion, deoxidation, desulfurization, control chemical composition and adjust temperature. The reduction period has been cancelled in high power and super power electric arc furnace steelmaking operation.

[0054] Refining outside the furnace: The steelmaking process of moving the molten steel that has been initially refined in the steelmaking furnace (converter, electric furnace, etc.) to another container for refining is also called secondary metallurgy. The steelmaking process is therefore divided into two steps: primary refining and refining. Primary refining: The charge is melted, dephosphorized, decarburized and alloyed in a furnace in an oxidizing atmosphere. Refining: The primary molten steel is degassed, deoxidized, desulfurized, inclusions are removed and the composition is fine-tuned in a container in a vacuum, inert gas or reducing atmosphere. The benefits of dividing steelmaking into two steps are: it can improve the quality of steel, shorten the smelting time, simplify the process and reduce production costs. There are many types of refining outside the furnace, which can be roughly divided into two categories: refining outside the furnace under normal pressure and refining outside the furnace under vacuum. According to different treatment methods, it can be divided into ladle treatment type refining outside the furnace and ladle refining type refining outside the furnace.

[0055] Molten steel stirring: stirring of molten steel during refining outside the furnace. It makes the composition and temperature of the molten steel uniform and can promote metallurgical reactions. Most metallurgical reaction processes are phase interface reactions, and the diffusion rate of reactants and products is the limiting link of these reactions. When the molten steel is in a static state, its metallurgical reaction rate is very slow. For example, it takes 30 to 60 minutes to desulfurize the static molten steel in an electric furnace; while it only takes 3 to 5 minutes to desulfurize the molten steel by stirring it in furnace refining. When the molten steel is in a static state, the inclusions float up and are removed, and the removal rate is slow; when the molten steel is stirred, the removal rate of inclusions increases exponentially and is related to the stirring intensity, type, characteristics and concentration of the inclusions.

[0056] Ladle wire feeding: feeding deoxidation, desulfurization and fine-tuning powders wrapped in iron sheets, such as Ca-Si powder, or directly feeding aluminum wire, carbon wire, etc. into the ladle to perform deep desulfurization, calcium treatment and fine-tune the carbon and aluminum components in the steel. It also has the function of cleaning the molten steel and improving the morphology of non-metallic inclusions.

[0057] The technical term "refined slag" in this embodiment is explained as follows:

[0058] Refined slag refers to the technology of mixing raw materials in a certain proportion and particle size, heating them below the melting point of the raw materials, sintering the raw materials together, and then crushing them into particles. The main components are CaO-CaF2-based, CaO-Al2O3-based, CaO-Al2O3-SiO2-based, and the forms of refined slag mainly include sintered type, pre-melted type and mixed type.

[0059] In the metallurgical process, the composition of slag has a very important influence on the cleanliness of molten steel. The highly oxidizing slag that enters the ladle after the converter taps out has a high content of unstable oxides such as FeO and MnO, which will continuously transfer oxygen to the molten steel, seriously affecting the aluminum recovery rate and the cleanliness of the molten steel, and ultimately leading to nozzle blockage and surface quality defects of the plate. Refining slag control technology has been applied to the production of IF steel by manufacturers such as Armco, Posco, and Nippon Steel in the last century. By reasonably controlling the composition of refined slag, the content of inclusions and harmful elements in the molten steel can be effectively reduced to obtain high-cleanliness steel. Therefore, it is particularly important to apply refined slag control technology on the basis of minimizing the amount of slag discharged during tapping.

[0060] A domestic factory currently uses the process of "top and bottom combined blowing converter → LF → RH → medium and thin slab continuous casting" to produce IF steel. The slag detection technology is used in the converter tapping process to control the thickness of the ladle slag layer at 50-80mm. When 1 / 2 of the steel is tapped, the regulator lime and fluorite are added to dilute the unstable oxides of FeO and MnO in the slag. After the steel is tapped, the metal aluminum-based reducing agent is added to the surface of the slag, and aluminum wire is fed into the steel. LF is used for electrode heating and slag reduction and modification. After the RH breaks through the air, some reducing agent is added to fine-tune the refined slag composition.

[0061] The oxidizability of the slag after the converter is high, w(FeO+MnO)=25%~40%. After the slag reduction treatment, w(FeO+MnO) in the slag drops sharply. After the modification is completed, the slag w(FeO+MnO) in the RH treatment process is 0.72%~5.38%, and in most cases it can be controlled below 3%, creating conditions for deoxidation and desulfurization of molten steel.

[0062] In order to enhance the absorption capacity of refined slag for inclusions, its composition must be controlled so that it is located in the low melting point area. There are three low melting point areas of about 1300℃ in the CaOAl2O3-SiO2 slag system. Among them, zones II and III have high SiO2 content and cannot be used for the refining treatment of aluminum deoxidized steel, while zone I has low SiO2 activity (about 10-4, with pure solid as the standard state) and is suitable for use as a refining slag system. During the RH treatment process, the composition of the refined slag is basically controlled near zone I, with a melting point of about 1335℃, which can well ensure the good fluidity of the refined slag.

[0063] Viscosity has a very close relationship with the mass transfer and heat transfer rate between slag and molten steel, and affects the rate of metallurgical reactions. When the CaO content in the slag is too high, the precipitation of solid particles in the slag will cause the slag viscosity to increase and the fluidity to deteriorate. However, since the refined slag contains more Al2O3, the problem of slag fluidity is effectively solved. From the viscosity diagram of the CaO-Al2O3-SiO2 slag system, it can be seen that the viscosity of the refined slag of the plant can be controlled in the low viscosity area (about 1.5~2Pa·s).

[0064] Inclusion removal performance

[0065] Once the inclusions in the steel float to the slag-steel interface, they should be firmly adsorbed by the slag and quickly dissolved. If the slag is not able to adsorb the inclusions sufficiently, the inclusions may be brought back into the molten steel by the steel flow. From the perspective of inclusion removal, the slag should maintain good wettability with the inclusions and have the ability to quickly dissolve the inclusions. The dissolution rate of Al2O3 in the CaO-Al2O3-SiO2 slag depends on many factors. Under the condition that the influencing factors such as temperature and stirring conditions remain unchanged, only the influence of the slag composition is considered.

[0066] Within the composition range of the refined slag, the relative dissolution rate of Al2O3 in the slag is relatively high. The relative dissolution rate of Al2O3 in the CaO-Al2O3-SiO2 slag system The basicity of the refined slag has a great influence on the deoxidation of molten steel. Studies have shown that with the increase of basicity and the decrease of SiO2 content in the slag, the deoxidation capacity of the refined slag increases. This is because the decrease in SiO2 content in the slag reduces its activity, thereby reducing or avoiding the secondary oxidation of the deoxidized steel liquid by SiO2 in the slag. The binary basicity of the refined slag is very high, w(CaO) / w(SiO2)=5~11. The ability of the ladle slag to absorb Al2O3 inclusions is maintained at a high level, while preventing the secondary oxidation caused by SiO2 and inhibiting the return of silicon and sulfur.

[0067] In addition to the basicity of the refined slag, the w(CaO) / w(SiO2) in the slag plays an important role in deoxidation. The test of the ultra-low carbon steel produced by the Mizushima Plant in Kawasaki, Japan, showed that when the top slag w(CaO) / w(SiO2)=1.4~1.8, the ability of the refined slag to adsorb Al2O3 inclusions reached the maximum. The refined slag of this plant basically meets the above requirements. The Al2O3 content in the RH outgoing ladle slag is significantly higher than the incoming value, indicating that inclusions continue to float up into the slag during the RH treatment process.

[0068] The free oxygen content in the steel after RH aluminum deoxidation is very low, and the molten steel is covered with high-basicity and high-reducing refined slag, which provides favorable thermodynamic conditions for desulfurization of the molten steel.

[0069] The optical basicity of slag indicates the ability of CaO in the slag to provide oxygen ions, and represents the strength of its ability to participate in desulfurization.

[0070] Research shows that the slag has the strongest desulfurization ability when the optical basicity is 0.78-0.82. The optical basicity of the refined slag is calculated to be 0.74-0.76, indicating that the refined slag has a strong desulfurization ability.

[0071] Based on the above description and the defects in the prior art, this embodiment proposes a method for controlling the composition of refined slag in the steelmaking and refining process, such as Figure 1 ,include:

[0072] Determine the target composition of the steel grade to be smelted and calculate the types of inclusions that are stable in the steel grade;

[0073] Determine the target composition of the refined slag according to the target composition and the type of inclusions, and then obtain the physical property parameters of the refined slag;

[0074] The total mass of the refined slag is determined based on the physical properties of the refined slag.

[0075] This embodiment changes the current situation of fixed addition amounts of slag and alloy in the converter steel-tapping process, calculates the addition amounts of alloy and slag in the converter steel-tapping process for each furnace according to the smelting conditions, thereby reducing the number of times materials are added to fine-tune the steel and slag composition and the number of times electrodes are energized during the refining process, thereby improving the refining efficiency and the refining slag endpoint hit rate and reducing energy consumption.

[0076] Furthermore, the process of calculating the types of inclusions that are stable in a steel grade is:

[0077] By smelting the target components in the steel grade, the equilibrium concentration of the steel-inclusion interface is obtained, and the equilibrium concentration and time of the steel-inclusion interface are derived and calculated to obtain the type of inclusions;

[0078] Among them, when the calculation time reaches the preset value, the inclusion composition no longer changes significantly, that is, the stable inclusion types are obtained.

[0079] Specifically, according to the internal control indicators of the enterprise, the target composition of the smelting steel grade is obtained, and the types of inclusions that stably exist in the steel grade are calculated.

[0080] The steps to calculate the stable inclusions of a steel grade from the target composition of the steel grade are as follows:

[0081] The reaction between the molten steel and inclusion system is a process of multiple chemical reactions coupled with each other. [M] is used to represent the concentration of component M in the molten steel; [M] * is the concentration of component M in the boundary layer of molten steel.

[0082] The general formula for the chemical reaction occurring at the interface is:

[0083]

[0084] Where, [M] is the concentration of component M in the liquid steel phase, wt%; [O] is the concentration of component O in the liquid steel phase, wt%; υ M is the stoichiometric number of component M, υ O is the stoichiometric number of component O, is the concentration of the product component, wt%.

[0085] When the reaction is in equilibrium, the equilibrium constant can be expressed as:

[0086]

[0087]

[0088] In the formula, K M is the equilibrium constant of the reaction; a is the activity, the steel liquid component is based on 1% by mass as the standard state, and the slag phase component is based on pure substance as the standard state; γ and f are the activity coefficients of the slag phase and steel liquid phase components respectively; (MvM O vO ) and [M] are the concentrations of slag phase and liquid steel phase components, wt%; E M is the apparent equilibrium constant.

[0089] In this example, it is assumed that there is steady-state mass transfer on both sides of the molten steel-inclusion interface, that is, there is no accumulation of substances on the interface, and the chemical reaction on the molten steel-inclusion interface is very fast, so the mass transfer in the molten steel and inclusion phase is the limiting link of the reaction. n The mass transfer flux equation is:

[0090]

[0091]

[0092] Where J is the molar flux density, mol / (m 2 ·s 2 );ρ is density, kg / m 3 ; k is the mass transfer coefficient, m / s; M is the molar mass, kg / mol; the superscripts “b” and “*” represent bulk and film, respectively; [] represents the concentration of molten steel components, and () represents the concentration of slag phase or inclusion phase components, wt%.

[0093] In order to solve the equation, it is also necessary to supplement the mass transfer flux conservation equation and the charge conservation equation:

[0094]

[0095]

[0096] Where n e,M is the charge number of each steel component, for example n e,Ca =2,n e,Al =3,n e,Si =4.

[0097] By combining the above equations, the concentration of each component at the interface can be calculated.

[0098]

[0099] In the formula, E M is the apparent equilibrium constant;

[0100] F M is a defined constant and is calculated as follows:

[0101]

[0102] In the formula, ρ slag(inc) is the density of slag phase (or inclusion phase), kg / m3 ρ steel is the density of molten steel, kg / m 3 .

[0103] According to the stoichiometric number v of the compound M The value of v is divided into two forms. For components such as CaO, SiO2, MnO, and MgO, M =1, the equation to be solved is a linear equation; for components such as Al2O3, v M =2, the equation to be solved is a quadratic equation.

[0104] By transforming formula (8), the interface [M] * The concentration of can be expressed as [O] at the interface * The function is as follows:

[0105]

[0106] The mass transfer due to the concentration difference between the bulk and the interface is:

[0107]

[0108] In the formula, A int is the interface area, m 2 ; k is the mass transfer coefficient of the component, m / s; V is the volume of each phase, m 3 .

[0109] Since the interface area between steel and inclusions is small and is a spherical interface, the surface renewal theory is used to calculate the mass transfer coefficient k in this embodiment. M,inc :

[0110]

[0111] In the formula, C k,inc is a constant, which is 0.03 in this embodiment; D is the diffusion coefficient, m 2 / s;u slip is the floating speed of inclusions in molten steel, calculated according to the following formula, m / s; d inc is the diameter of the inclusion, m.

[0112]

[0113] Where g is the acceleration due to gravity, 9.8m 2 / s; μ steel is the viscosity of the molten steel; ρ inc is the inclusion phase density, kg / m 3 .

[0114] In this embodiment, after calculating for about 1000 seconds, the inclusion composition no longer changes significantly, that is, the inclusion composition is stable.

[0115] Furthermore, the process of determining the target composition of the refined slag is as follows:

[0116] According to the composition of the inclusion types, the composition and basicity of the refined slag are set to obtain the target composition of the refined slag, and the physical property parameters of the refined slag are obtained by calculation;

[0117] Among them, the physical properties of refined slag include density, viscosity, sulfur control index, the ability of refined slag to dissolve inclusions, and the rate at which refined slag dissolves inclusions.

[0118] Specifically, first, according to the composition of inclusions, when the inclusions are Al2O3 and CaO-Al2O3 type inclusions, the CaO / Al2O3 mass ratio of the refined slag is set to 1.6-1.8, the basicity is 6-8, the MgO content in the refined slag is 6%, and the CaF2 content is 100kg (this item is set according to actual needs); when the inclusions are MgO-Al2O3 type inclusions, there is no requirement for the MgO content in the refined slag.

[0119] The target composition of refined slag is calculated according to the following formula:

[0120]

[0121]

[0122]

[0123] Wherein, R is the basicity of the refined slag; C / A is the CaO / Al2O3 mass ratio of the refined slag; m is the mass, kg.

[0124] The physical properties of refined slag are calculated according to the following formula:

[0125]

[0126]

[0127]

[0128]

[0129]

[0130]

[0131] Where ρ is density, g / cm 3 ; η is viscosity, Pa·s; C sis the sulfur control index; Zh is the Zh number, the ability of the reaction refining slag to dissolve inclusions; Ry is the Ry number, the rate at which the reaction refining slag dissolves inclusions; T is the actual refining temperature, °C; ρ T is the density of refined slag at actual refining temperature, kg / m 3 ρ 1400℃ is the density of refined slag at 1400℃, kg / m 3 , ρ slag is the refined slag density, kg / m 3 , η slag is the viscosity of refined slag, Pa·s, d p，0 is the initial diameter of the inclusion, m; ΔC is the saturation concentration difference of the inclusion in the slag, %; ψ is the dissolution rate of the inclusion in the slag, m 3 / s.

[0132] Furthermore, the process of determining the total mass of the refined slag is:

[0133] Combined with the requirements of oxygen, nitrogen and sulfur control, the amount of fluorite and pre-melted slag added is fixed, and then the amount of aluminum block added and the amount of lime used are determined, and the slag amount is calculated to see if it meets the requirements. If it does not meet the requirements, lime and pre-melted slag are used to make up for it;

[0134] The amount of aluminum block added is the sum of the amount of aluminum as an alloy element in steel, the amount of aluminum added for deoxidation, the amount of aluminum added for slag reforming, and the amount of aluminum consumed by secondary oxidation.

[0135] Specifically, in order to achieve the goal of hitting the refined slag composition, the total mass of the refined slag is determined in combination with the requirements of oxygen, nitrogen and sulfur control, and the amount of fluorite, pre-melted slag, aluminum blocks, lime and other slag materials is further calculated.

[0136] When there is a need to control nitrogen during the refining process, add 0.5t to the total slag volume. When there is a need to control sulfur during the refining process, recalculate the slag volume according to the following formula:

[0137]

[0138]

[0139] Where, L S is the distribution coefficient of sulfur in slag steel; [S]0 is the sulfur content of steel tapped from the converter; [S] is the target sulfur content at the end of refining, m slag is the slag mass, kg; m steel is the mass of molten steel, kg.

[0140] In this embodiment, first, the addition amount of fluorite (100kg) and pre-melted slag (250kg) is fixed. Then the addition amount of aluminum blocks is determined, which is divided into four categories, including aluminum alloy elements in steel, aluminum for deoxidation, aluminum for slag reforming, and aluminum consumed by secondary oxidation. The total addition amount of aluminum blocks is shown in the following formula.

[0141] m 铝块 =m 钢中Al +m 脱氧Al +m 渣改质Al +m 二次氧化Al (26);

[0142] Taking into account that converter slag will also enter the ladle during the steelmaking process and participate in slag formation, the quality and composition of the converter slag need to be considered.

[0143] The FeO content in converter slag is calculated by the converter endpoint oxygen activity, as shown in the following formula:

[0144] (FeO) = k FeO a O (27);

[0145] In the formula, k FeO is the coefficient, which is 400 in this embodiment; a O It is the oxygen activity of steel tapped from the converter.

[0146] Then determine the amount of lime, using the CaO / Al2O3 mass ratio. Finally, calculate whether the slag volume meets the requirements. If it does not meet the requirements, use lime and pre-melted slag to make up.

[0147] This embodiment also provides a control system for controlling the composition of refined slag in a steelmaking and refining process, comprising:

[0148] Composition determination module: used to calculate the types of inclusions that are stable in the steel grade through the target composition of the smelted steel grade;

[0149] Refined slag physical property parameter determination module: used to determine the target composition of the refined slag according to the target composition and the type of inclusions, and then obtain the physical property parameters of the refined slag;

[0150] Refined slag total mass output module: used to determine the total mass of the refined slag in combination with the physical property parameters of the refined slag.

[0151] Further, the composition determination module includes an inclusion type determination unit, which is used to obtain the steel-inclusion interface equilibrium concentration by smelting the target composition in the steel grade, and to perform derivative calculations on the steel-inclusion interface equilibrium concentration and time respectively to obtain the inclusion type;

[0152] When the calculation time reaches the preset value, the inclusion composition no longer changes significantly, that is, the stably existing inclusion type is obtained.

[0153] Furthermore, the refined slag physical property parameter determination module is used to set the composition and basicity of the refined slag according to the composition of the inclusion types, obtain the target composition of the refined slag, and obtain the physical property parameters of the refined slag by calculation;

[0154] The physical properties of refined slag include density, viscosity, sulfur control index, the ability of refined slag to dissolve inclusions, and the rate at which refined slag dissolves inclusions.

[0155] Furthermore, the refined slag total mass output module fixes the amount of fluorite and pre-melted slag added by combining the requirements of oxygen control, nitrogen control and sulfur control, and then determines the amount of aluminum block added and the amount of lime used, and calculates whether the slag amount meets the requirements. If it does not meet the requirements, lime and pre-melted slag are used to make up for it;

[0156] The amount of aluminum block added is the sum of the amount of aluminum added as an alloy element in steel, the amount of aluminum added for deoxidation, the amount of aluminum added for slag reforming, and the amount of aluminum added for secondary oxidation consumption.

[0157] This embodiment also provides a computer device, including a memory, a processor, and a computer program stored in the memory, characterized in that the processor executes the computer program to implement the steps of the control method.

[0158] In order to more clearly express the technical solution of the present invention, the following specific embodiments are provided to introduce the solution:

[0159] This embodiment takes the 700BL steelmaking and refining process as an example for research, and includes the following steps:

[0160] S1: The composition of stable inclusions in steel is calculated based on the target composition of the steel grade.

[0161] Read the internal control composition of 700BL steel, see Table 1:

[0162] Table 1

[0163] Temperature (C°) Mass(t) C Mn S P Si Alt Ca N Cr Ni Ti O 1600 260 0.0626 1.262 0.0011 0.0131 0.147 0.0290 0.00213 0.0038 0.22 0.01 0.094 0.0030

[0164] The equilibrium concentration of the steel-inclusion interface is obtained by solving equation (10), and the time is iterated according to equations (11)-(12) to obtain the final stable inclusion composition as shown below, which is mainly CaO-Al2O3 inclusions, as shown in Table 2.

[0165] Table 2

[0166] Mass(kg) CaO <![CDATA[Al2O3]]> <![CDATA[SiO2]]> MnO MgO FeO CaS <![CDATA[Ti2O3]]> 7.6215 34.51 43.79 4.98 0.11 0 0 0.06 16.55

[0167] S2: Determine the target composition of the refined slag based on the target composition of the steel grade and the type of inclusions, and calculate the sulfur control ability and inclusion removal ability of the refined slag.

[0168] The stable composition of inclusions is CaO-Al2O3 inclusions, so the CaO / Al2O3 mass ratio of the refined slag is 1.6-1.8, the basicity is 6-8, the MgO content in the refined slag is 6%, and the CaF2 content is 100kg. The design target composition of the refined slag is calculated according to formulas (15)-(17) as shown in Table 3.

[0169] Table 3

[0170] Mass(kg) CaO <![CDATA[Al2O3]]> <![CDATA[SiO2]]> MnO MgO FeO <![CDATA[Ti2O3]]> <![CDATA[CaF2]]> 3 55.05 28.74 6.88 0 6 0 0 3.33

[0171] The physical properties of the refined slag system are calculated using equations (18) to (23), as shown in Table 4:

[0172] Table 4

[0173] <![CDATA[Density (kg / m 3 )]]> Viscosity (Pa·s) <![CDATA[Desulfurization index, C S > <![CDATA[Sulfur capacity, L S > Zh Index Ry Index 2941 0.2446 867 <![CDATA[6.12×10 -7 ]]> <![CDATA[4.4×10 10 d p 3 ]]> <![CDATA[0.0054d p 3 ]]>

[0174] S3: Determine the total mass of refined slag based on the requirements of oxygen, nitrogen and sulfur control, and further calculate the amount of slag materials such as fluorite, pre-melted slag, aluminum blocks, lime, etc.

[0175] First, read the composition of the slag, as shown in Table 5:

[0176] Table 5

[0177] Element CaO <![CDATA[Al2O3]]> <![CDATA[SiO2]]> MnO MgO FeO <![CDATA[CaF2]]> Al Pre-slag modifier 43.09 48.24 2.98 0 1.66 1.12 2.29 0 Converter Modifier 49.23 41.82 2.89 0 1.15 1.02 3.29 0 Slag agent 50.2 37.77 3.33 0 3.41 1.52 2.29 0 Pre-melted refined slag 34.5 49.36 2.85 0 0 1.9 5.86 0 fluorite 0.32 1.73 29.02 0 0 0 68.16 0 lime 97.4 0.3 0 0 0 0 0 0 Aluminum Granules 0 0 0 0 0 0 0 100

[0178] The oxygen activity in the final molten steel of the converter was measured to be 0.05%. The FeO content in the slag of the converter was calculated by formula (27) to be 20%. The amount of slag of the converter was 0.75 tons, and the composition was shown in Table 6:

[0179] Table 6

[0180] Mass(t) CaO <![CDATA[Al2O3]]> <![CDATA[SiO2]]> MnO MgO FeO <![CDATA[CaF2]]> <![CDATA[P2O5]]> 0.75 47.51 1.67 13.74 2.91 10.41 20 0 3.83

[0181] Finally determine the amount of various materials.

[0182] When there is no sulfur control requirement in the 700BL steel refining process, the fixed fluorite and pre-melted refined slag addition amounts are 100kg and 250kg respectively. The amount of aluminum block added is calculated according to formula (26), and the amount of aluminum used to supplement the aluminum content in the steel is (m steel *0.029%), the amount of aluminum used for deoxidation is (m steel *0.05%*27*2 / (16*3)), the amount of aluminum used for slag reforming is (m slag *((FeO) / 72 / 1.5+(MnO) / 71 / 1.5)*27*2), the amount of aluminum lost by secondary oxidation (m steel*0.01%), assuming that 0.01% of the aluminum is burned by secondary oxidation. After summarizing, the amount of aluminum block added is 454.19kg. In addition to the aluminum that enters the molten steel, the rest of the aluminum all enters the slag in the form of Al2O3, so the total mass of Al2O3 in the refined slag can be obtained. Then, according to the CaO / Al2O3 ratio of the slag, the amount of lime is determined to be 1503.15kg. Therefore, the final addition is 1503.15kg of lime, 454.19kg of aluminum block (454.19kg of which enters the refined slag and is converted into 715.5kg Al2O3), 100kg of fluorite, 250kg of pre-melted refined slag, and the total slag amount is 3.32 tons.

[0183] When there is a need for sulfur control in the refining process, for example, when the sulfur content in the molten steel is 0.05% when the converter is tapped, and the target sulfur content of the steel grade is 0.0011, according to formulas (24) and (25), the amount of slag under the condition of desulfurization demand is calculated to be 4.79 tons, and the amount of slag added is: 1982.34 kg of lime, 454.19 kg of aluminum block, 100 kg of fluorite, and 1012.89 kg of pre-melted refined slag.

[0184] This embodiment designs special refining slag system components for different steel grades, and adjusts the amount of refining slag in real time in combination with process requirements such as sulfur control and nitrogen control, so as to achieve one-time addition of slag during the converter steelmaking process and hit the target composition of the refining slag, thereby solving the problems of "all steel grades use the same refining slag system" and "two or more times of adding materials during the refining process" in the traditional process, simplifying the production operation process, improving the production efficiency of smelting, improving the quality grade of products, and reducing the production cost of the enterprise.

[0185] The above are only preferred specific implementations of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A method for controlling the composition of refined slag in a steelmaking and refining process, characterized in that: include: Determine the target composition of the steel grade to be smelted and calculate the types of inclusions that are stable in the steel grade; Determine the target composition of the refined slag according to the target composition and the type of inclusions, and then obtain the physical property parameters of the refined slag; The total mass of the refined slag is determined based on the physical properties of the refined slag.

2. The control method according to claim 1, characterized in that: The process of calculating the types of inclusions that are stable in the steel grade is: The equilibrium concentration of the steel-inclusion interface is obtained through the target composition in the smelting steel grade, and the equilibrium concentration of the steel-inclusion interface and the time are respectively derived to obtain the type of inclusions; When the calculation time reaches a preset value, the inclusion composition no longer changes significantly, that is, the stably existing inclusion type is obtained.

3. The control method according to claim 2, characterized in that: The equilibrium concentration at the steel-inclusion interface is: Where, [M] * and [O] * is the concentration of component M and oxygen in the boundary layer of molten steel, wt%; [M] b is the concentration of component M in the molten steel, wt%; is the concentration of slag phase components, wt%; v M and v O are the stoichiometric numbers of component M and oxygen element respectively; F M is the definition constant; E M is the apparent equilibrium constant; ρ slag(inc) is the slag phase density, kg / m 3 ; ρ steel is the density of molten steel, kg / m 3 ; k is the mass transfer coefficient, m / s; M is the molar mass, kg / mol; k M is the mass transfer coefficient of component M, m / s; M M is the molar mass of component M, kg / mol.

4. The control method according to claim 1, characterized in that: The process of determining the target composition of refined slag is as follows: According to the composition of the inclusion types, the composition and basicity of the refined slag are set to obtain the target composition of the refined slag, and the physical property parameters of the refined slag are obtained by calculation; The physical property parameters of the refined slag include density, viscosity, sulfur control index, the ability of the refined slag to dissolve inclusions, and the rate at which the refined slag dissolves inclusions.

5. The control method according to claim 4, characterized in that: The process of determining the total mass of the refined slag is: Combined with the requirements of oxygen, nitrogen and sulfur control, the amount of fluorite and pre-melted slag added is fixed, and then the amount of aluminum block added and the amount of lime used are determined, and the slag amount is calculated to see if it meets the requirements. If it does not meet the requirements, lime and pre-melted slag are used to make up for it; The amount of aluminum block added is the sum of the amount of aluminum as an alloy element in steel, the amount of aluminum for deoxidation, the amount of aluminum for slag reforming, and the amount of aluminum consumed by secondary oxidation.

6. A control system for the composition of refined slag in the steelmaking and refining process, characterized in that: include: Composition determination module: used to calculate the types of inclusions that are stable in the steel grade through the target composition of the smelted steel grade; Refined slag physical property parameter determination module: used to determine the target composition of the refined slag according to the target composition and the type of inclusions, and then obtain the physical property parameters of the refined slag; Refined slag total mass output module: used to determine the total mass of the refined slag in combination with the physical property parameters of the refined slag.

7. The system according to claim 6, characterized in that The composition determination module includes an inclusion type determination unit, which is used to obtain the steel-inclusion interface equilibrium concentration through the target composition in the smelting steel grade, and to perform derivative calculations on the steel-inclusion interface equilibrium concentration and time respectively to obtain the inclusion type; When the calculation time reaches the preset value, the inclusion composition no longer changes significantly, that is, the stably existing inclusion type is obtained.

8. The system according to claim 6, characterized in that The refined slag physical property parameter determination module is used to set the composition and basicity of the refined slag according to the composition of the inclusion types, obtain the target composition of the refined slag, and obtain the physical property parameters of the refined slag by calculation; The physical property parameters of the refined slag include density, viscosity, sulfur control index, the ability of the refined slag to dissolve inclusions, and the rate at which the refined slag dissolves inclusions.

9. The system according to claim 6, characterized in that The refined slag total mass output module combines the oxygen control, nitrogen control and sulfur control requirements, fixes the amount of fluorite and pre-melted slag added, and then determines the amount of aluminum block added and the amount of lime used, and calculates whether the slag amount meets the requirements. If not, lime and pre-melted slag are used to make up for it; The amount of aluminum block added is the sum of the amount of aluminum alloy element added in the steel, the amount of aluminum added for deoxidation, the amount of aluminum added for slag reforming, and the amount of aluminum added for secondary oxidation consumption.

10. A computer device comprising a memory, a processor and a computer program stored in the memory, characterized in that: The processor executes the computer program to implement the steps of the control method according to any one of claims 1 to 5.

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