A water model experiment method for simulating movement of liquid in an electric furnace under electromagnetic effect

Abstract

The application discloses a water model experiment method for simulating the movement of liquid steel in an electric furnace under electromagnetic effect, and belongs to the electric furnace metallurgy field in the steel metallurgy, and specifically comprises the following steps: firstly, electromagnetic stirring force generated by the electric furnace on the liquid steel prototype and stirring force generated by a magnetic force stirrer on the water model are calculated respectively; according to the similarity principle, the similarity relationship between the electromagnetic stirring force of the prototype and the stirring force of the water model is calculated to ensure the similarity of the two; then, the parameters and the type of the magnetic force stirrer are determined according to the similarity relationship; the magnetic force stirring device including the magnetic force stirrer and the stirrer is installed on the water model according to the determined type of the magnetic force stirrer, including bottom or top installation; finally, the magnetic force stirrer is powered on according to the parameters of the magnetic force stirrer, the magnetic force stirrer works, the stirrer is driven to rotate at a constant speed, the cyclone of the water solution is formed, and the movement state of the liquid steel in the electric furnace under the electromagnetic effect is simulated. The application can intuitively simulate the movement behavior of the liquid steel by using the hydrodynamic experiment.

Description

Technical Field

[0001] This invention belongs to the field of electric furnace metallurgy in iron and steel metallurgy, and specifically relates to a water model experimental method for simulating the movement of molten steel in an electric furnace under electromagnetic effects. Background Technology

[0002] An electric furnace is a device that uses direct current or alternating current to generate a high-temperature electric arc zone to melt and smelt metals. The electromagnetic field of direct current or alternating current acts on conductive molten steel, generating a Lorentz force that causes the molten steel to rotate and form eddy currents. This effect is called electromagnetic stirring.

[0003] In a direct current (DC) electric furnace, the magnetic field generated by the electrodes acts on the molten steel, creating eddy currents that interact with the magnetic field, generating a rotational force that propels the molten steel to rotate. Because the conduction direction of direct current is fixed, the resulting eddy currents are stable and powerful. Although the magnetic field generated by three-phase alternating current is alternating, the superposition of these magnetic fields on the molten steel results in eddy currents with a stable direction of motion. Therefore, for electric furnaces of the same power, a DC electric furnace will have a more powerful electromagnetic stirring effect on the molten steel than an AC electric furnace.

[0004] Electromagnetic stirring can effectively improve the uniformity of molten steel, promote the mixing of slag and molten steel, accelerate heat and mass transfer, and thus improve the quality of molten steel.

[0005] Practical studies in factories using energized electrodes or electromagnetic stirring devices installed around the furnace have yielded some progress in simulating electromagnetic stirring in electric arc furnaces using physical models. Some studies have used low-melting-point metal alloys, such as tin, lead, bismuth, and mercury, to simulate the electromagnetic properties and flow behavior of molten steel. However, due to the opacity of metals, it is difficult to observe the internal movement of the liquid, and the cost is high. Some metals, such as lead and mercury, also have toxic side effects, making the experiments quite challenging.

[0006] By reducing the size between the model and the actual metallurgical reactor, and utilizing the principle of similarity of dimensionless numbers such as Reynolds number and Euler number, the dynamic characteristics of aqueous fluids (such as flow velocity and pressure) can be simulated to predict the flow behavior of metallurgical reactors under the same conditions. This is an important tool for predicting actual phenomena through laboratory models.

[0007] Using water or salt water as the simulation medium in a water model can effectively simulate the flow behavior of molten steel, but it cannot simulate the electromagnetic stirring characteristics of molten steel. This is mainly because water and molten steel have vastly different electrical conductivities; the conductivity of saturated salt water differs from that of low-carbon molten steel by 10%. 5 At levels above a certain order of magnitude, the rotational motion of water is almost imperceptible when using electromagnetic stirring. Therefore, there are currently no physical experiments using water models to simulate the eddy current effect created by electromagnetic stirring.

[0008] If we can simulate the flow behavior of electromagnetically stirred molten steel through water model experiments, achieve visualization effects, obtain parameters such as fluid velocity and temperature, and do so at a low cost and with no side effects, it will solve the problem that water models cannot simulate the formation of eddies in electromagnetically stirred molten steel.

[0009] The traditional stirring method introduced in water model experiments is the air blowing method. As we all know, air blowing and electromagnetic stirring are two methods with completely different principles and modes of operation, so they are not suitable for simulating the movement of molten steel formed by electromagnetic stirring.

[0010] Another approach is to use a rotating paddle to create vortices, similar in form to the eddies in electromagnetic stirring, and to simulate this using a motor-driven paddle in a water model. Unlike electromagnetic stirring, this method requires a shaft to drive the paddle or impeller head, disrupting the closed molten steel system. In contrast, the electromagnetic field created by energizing electrodes in molten steel is a closed system, unaffected by the rotating shaft. Mechanical stirring mixes liquids or slurries in a container through the rotation of paddles. Electromagnetic stirring induces a rotating magnetic field at the bottom of the container, driving the liquid or slurry to rotate and achieve mixing. Mechanical rotation generates high shear forces, making it difficult to use in closed systems; therefore, mechanical stirring with a rotating paddle is unsuitable for simulating the eddies created by electromagnetic stirring.

[0011] Based on the principle that like poles repel and unlike poles attract in magnetic fields, a magnetic stirrer uses a magnetic field to drive a magnetic stir bar placed in a container to rotate in the liquid, thus achieving the purpose of stirring a closed liquid system. Stirrers are generally also equipped with a temperature control system, which can control the temperature and heat simultaneously with stirring.

[0012] The differences between magnetic stirrers and electromagnetic stirrers are as follows: Magnetic stirrers use an external magnet to drive a rotor, while electromagnetic stirrers use electromagnetic induction to generate a rotating magnetic field that drives the liquid; magnetic stirrers use a rotating rotor to drive the liquid flow, while electromagnetic stirrers generate a vortex rotation of the entire liquid. More importantly, both utilize electromagnetic force to drive stirring, and the shear forces they generate are similar, making them suitable for closed systems and avoiding mechanical wear and contamination.

[0013] Therefore, in terms of principle and actual working conditions, it is entirely feasible to use a magnetic stirrer to simulate electromagnetic stirring in the water model experiment of an electric arc furnace; moreover, electromagnetic stirring can also provide feedback for parameter selection in the actual production process. Summary of the Invention

[0014] To address the aforementioned problems, this invention proposes a water model method for simulating the movement of molten steel in an electric furnace under electromagnetic effects. This method overcomes the difficulty of water models simulating the formation of eddies in molten steel under electromagnetic stirring, and can intuitively simulate the motion behavior of molten steel using hydrodynamic experiments.

[0015] The specific steps of the water model method for simulating the movement of molten steel in an electric furnace under electromagnetic effects are as follows:

[0016] Step 1: Calculate the electromagnetic stirring force generated by the electric furnace on the prototype molten steel.

[0017] F p ==I p B p L p sinα

[0018] In the formula, F p The electromagnetic stirring force represents the prototype of the molten steel; I p Represents current; B p L represents the magnetic field strength generated by the electric current. p α represents the distance from the current to the molten steel; α is the direction of the current relative to B. p The angle between directions; the subscript p indicates the prototype.

[0019] Step 2: Calculate the stirring force generated by the magnetic stirrer in the water model;

[0020] F m =kB m I m Nd

[0021] Among them, F m The force exerted on the liquid in the water model represents the stirring force; k represents the scaling factor; B m I represents the magnetic field strength generated by the magnetic stirrer. m The magnetic stir bar represents the magnetization intensity; N represents the rotational speed of the magnetic stir bar; d represents the diameter of the magnetic stir bar; and the subscript m indicates a water model.

[0022] Step 3: Based on the principle of similarity, select the similarity criterion that uses pressure difference to represent the flow relationship during the fluid flow process, and calculate the similarity relationship between the electromagnetic stirring force of the prototype and the stirring force of the water model to ensure that the two are similar.

[0023] The formula for calculating the similarity criterion is:

[0024] F p / S p *g / (ρ p *v p 2 ) = F m / S m *g / (ρ m *v m 2 )

[0025] S p S represents the area of ​​the prototype subjected to pressure; mThe area of ​​the water model subjected to pressure is represented by g; g represents the acceleration due to gravity, and ρ represents the surface area of ​​the water model subjected to pressure. p ρ represents the density of the original molten steel. m The density of the original water; v p The fluid velocity v represents the prototype of molten steel. m Indicates the fluid velocity of the water prototype;

[0026] Step 4: Determine the parameters and model of the magnetic stirrer based on the similarity relationship of stirring forces;

[0027] The parameters include the geometry, current, rotation speed, shape, and stirring direction of the stir bar, which are used to determine the model of the magnetic stirrer.

[0028] Step 5: According to the determined magnetic stirrer model, install the magnetic stirring device, including the magnetic stirrer and stir bar, on the water model;

[0029] The installation method includes two types: bottom installation or top installation.

[0030] 1) Bottom installation: After filling the water model with liquid, place the stir bar inside the bottom of the water model. Place the magnetic stirrer on the bottom outside the water model, with the stir bar directly above the center of the magnetic stirrer. Turn on the power to make the magnetic stirrer move and drive the stir bar to rotate.

[0031] 2) Top installation: Place the stir bar on top of the liquid in the water model, place a tray on the stir bar, and place the magnetic stirrer on the tray, directly above the stir bar. Turn on the power to make the magnetic stirrer move and drive the stir bar to rotate.

[0032] The number of magnetic stirring devices is variable, and the number of stir bar components is determined by the current supplied to the DC or AC furnace. One stir bar component is placed at each current supply point. When the magnetic stirring devices are operating, the rotation direction of the molten steel caused by the DC or AC furnace is determined by electromagnetic rules such as the left-hand rule, and the rotation direction of the stir bar components is consistent with this.

[0033] Step 6: Power on the magnetic stirrer according to its parameters. The magnetic stirrer will then operate, causing the stir bar to rotate at a constant speed, forming a swirling flow of the aqueous solution, simulating the movement of molten steel in an electric furnace under electromagnetic effects.

[0034] The advantages of this invention are:

[0035] 1. The present invention provides a water model method for simulating the movement of molten steel in an electric furnace under electromagnetic effects. The equipment used is simple and readily available. In particular, there are a wide variety of magnetic stirrers and stir bar types and sizes available. Different experimental requirements can be met by selecting different models of magnetic stirrers and stir bar types of different shapes and sizes.

[0036] 2. The present invention provides a water model method for simulating the movement of molten steel in an electric furnace under electromagnetic effects. Through the principle of similarity, the stirring energy of molten steel in an electric furnace under electromagnetic effects is similar to the stirring energy of a magnetic stirrer in a water model. The magnetic stirrer can obtain a wide range of stirring energies, thus easily satisfying the similarity between the two.

[0037] 3. The present invention provides a water model method for simulating the movement of molten steel in an electric furnace under electromagnetic effects. It is simple to operate, and the stirring element in the device is small in size and can be placed at the bottom or above the liquid surface, allowing for flexible position adjustment.

[0038] 4. The present invention provides a water model method for simulating the movement of molten steel in an electric furnace under electromagnetic effects. This method overcomes the problem that traditional electric furnace water model experiments cannot simulate electromagnetic stirring flow. It can intuitively simulate the movement behavior of molten steel and can also be promoted in metallurgical water model experiments under other similar conditions. Attached Figure Description

[0039] Figure 1 This is a flowchart of a water model method for simulating the movement of molten steel in an electric furnace under electromagnetic effects, according to the present invention.

[0040] Figure 2 This is an example diagram of the magnetic stirring device described in this invention installed at the bottom of a water model.

[0041] Figure 3 This is a comparison diagram of the stirring vortex rotation of the steel liquid and water model in the example of the present invention.

[0042] Among them, 1-top electrode, 2-electric arc, 3-electric furnace molten steel, 4-electric furnace lining, 5-bottom anode, 6-magnetic stirrer, 7-tray, 8-stirring bar, 9-water model solution, 10-electric furnace water model lining; Detailed Implementation

[0043] The present invention will now be described in further detail with reference to the accompanying drawings.

[0044] This invention provides a water model method for simulating the movement of molten steel in an electric arc furnace under electromagnetic effects. It is applicable to simulating the movement behavior of molten steel in an electric arc furnace under electromagnetic stirring within a water model, or other experiments that require simulating the stirring caused by electromagnetic effects when immersed in molten metal. By installing a magnetic stirring device on the water model, the electromagnetic stirring motion of molten steel in a DC or AC electric arc furnace can be simulated.

[0045] like Figure 1 As shown, the specific steps are as follows:

[0046] Step 1: Calculate the electromagnetic stirring force generated by the electric furnace on the molten steel;

[0047] F p ==I p B p Lp sinα

[0048] In the formula, F p The electromagnetic stirring force acting on the prototype of molten steel is represented by Newtons (N); I p Represents electric current, measured in amperes (A); B p L represents the magnetic field strength produced by an electric current, measured in Tesla (T). p The distance from the current to the molten steel is represented by meters (m); α is the angle between the current direction and the B direction, which is 90°; the subscript p indicates the prototype.

[0049] Step 2: Calculate the stirring force generated by the magnetic stirrer in the water model;

[0050] F m =kB m I m Nd

[0051] Among them, F m The force exerted on the liquid in the water model represents the stirring force, measured in Newtons (N); k represents the proportionality constant, typically set to 1; B m The magnetic field strength generated by a magnetic stirrer is represented by the unit Tesla (T); I m The magnetization of the magnetic stir bar is represented by amperes per meter (A / m); N represents the rotational speed of the magnetic stir bar in revolutions per second (rps); d represents the diameter of the magnetic stir bar in meters (m), and the subscript m indicates a water model.

[0052] Step 3: Based on the principle of similarity, select the similarity criterion that uses pressure difference to represent the flow relationship during the fluid flow process, and calculate the similarity relationship between the electromagnetic stirring force of the prototype and the stirring force of the water model to ensure that the two are similar.

[0053] The similarity criterion used is the Euler criterion, calculated using the following formula:

[0054] F p / S p *g / (ρ p *v p 2 ) = F m / S m *g / (ρ m *v m 2 )

[0055] S p S represents the area of ​​the prototype subjected to pressure; m The area of ​​the water model subjected to pressure is represented by g; g represents the acceleration due to gravity, and ρ represents the surface area of ​​the water model subjected to pressure. p This indicates the density of molten steel, expressed in kilograms per cubic meter (kg / m³).3 );ρ m The density of the original water; v p The velocity of the molten steel prototype is expressed in meters per second (m / s); v m Indicates the fluid velocity of the water prototype;

[0056] Step 4: Determine the parameters and model of the magnetic stirrer based on the similarity relationship of stirring forces;

[0057] The parameters include the geometry of the stir bar, current, rotation speed, shape, and stirring direction, which determine the model of the magnetic stirrer.

[0058] Step 5: Based on the determined magnetic stirrer parameters, install the magnetic stirring device, including the magnetic stirrer and stir bar, on the water model;

[0059] The installation method includes two types: bottom installation or top installation.

[0060] 1) Bottom installation: After filling the water model with liquid, place the stir bar inside the bottom of the water model. Place the magnetic stirrer on the bottom outside the water model, with the stir bar directly above the center of the magnetic stirrer. Turn on the power to make the magnetic stirrer move and drive the stir bar to rotate.

[0061] 2) Top installation: Place the stir bar on top of the liquid in the water model, place a tray on the stir bar, and place the magnetic stirrer on the tray, directly above the stir bar. Turn on the power to make the magnetic stirrer move and drive the stir bar to rotate.

[0062] The number of magnetic stirring devices is variable, and the number of stir bar components is determined by the current supplied to the DC or AC furnace. One stir bar component is placed at each current supply point. When the magnetic stirring devices are operating, the rotation direction of the molten steel caused by the DC or AC furnace is determined by electromagnetic rules such as the left-hand rule, and the rotation direction of the stir bar components is consistent with this.

[0063] Step 6: Power on the magnetic stirrer according to its parameters. The magnetic stirrer will then operate, causing the stir bar to rotate at a constant speed, forming a swirling flow of the aqueous solution, simulating the movement of molten steel in an electric furnace under electromagnetic effects.

[0064] Furthermore, depending on the experimental requirements, a recording device can be placed outside the water model to record the flow state of the solution, and a mixing time recorder can be placed inside the water model to measure the mixing time of the solution. Alternatively, other devices can be used to measure the motion parameters of the fluid and observe the similarity.

[0065] Example 1:

[0066] The water model simulation stirring method for simulating the movement of molten steel in a DC electric furnace under electromagnetic effects is as follows: Figure 2As shown, after the water model is filled with liquid, a stir bar is placed in the center of the bottom of the water model, and a magnetic stirrer is placed in the center of the bottom outside the water model. When the power is turned on, the magnetic stirrer moves and drives the stir bar to rotate.

[0067] Example 2:

[0068] The water model simulation stirring method for simulating the movement of molten steel in a DC electric furnace under electromagnetic effects is as follows: a stir bar is placed at the center of the top of the liquid in the water model, a tray is placed on the stir bar, and a magnetic stirrer is placed on the tray, directly above the stir bar. Power is applied to make the stir bar rotate.

[0069] Example 3:

[0070] The water model simulation stirring method for simulating the movement of molten steel in a three-phase AC electric furnace under electromagnetic effects is as follows: After the water model is filled with liquid, three stir bar elements are placed at the bottom of the water model corresponding to the three electrodes of the electric furnace. Three magnetic stirrers are placed directly below the three stir bar elements outside the water model. Power is applied to make the three stir bar elements rotate in the same direction.

[0071] Example 4:

[0072] The water model simulation stirring method for simulating the movement of molten steel in a three-phase AC electric furnace under electromagnetic effects involves placing three stir bar elements on the top of the liquid in the water model corresponding to the three electrode heads of the electric furnace. A tray is placed on the stir bar elements, and three magnetic stirrers are placed on the tray, each located directly above the stir bar elements. Power is applied to make the stir bar elements rotate in the same direction.

[0073] The calculations for Example 1 are as follows:

[0074] A certain 150t DC electric arc furnace is a traditional open-top electric furnace with a nominal furnace capacity of 150t. The steel tapping method is eccentric bottom type. The power supply consists of a transformer and a rectifier, etc. It is equipped with a top electrode and a set of bottom anodes with an electrode diameter of 700mm. The geometric parameters of the prototype and water model are shown in Table 1.

[0075] Table 1

[0076]

[0077] The power supply parameters for the prototype and the water model are shown in Table 2.

[0078] Table 2

[0079]

[0080] Calculating the electromagnetic stirring force generated by an electric furnace on molten steel is quite difficult, as it is affected by various factors such as the magnitude of the current and voltage, the distribution of the electromagnetic field, the properties of the molten steel, and the furnace structure. Based on calculations, the electromagnetic stirring force generated by this furnace on the molten steel is approximately 1 × 10⁻⁶. 4 Newton.

[0081] Based on the principle of similarity, the similarity ratio of the stirring force is taken as 5000 using the similarity criterion. In the water model experiment, the magnetic flux is taken as 0.1T, the magnetization intensity is 1A / m, the stirring speed is 500rpmin, and the length is 0.04m. The stirring force generated by the magnetic stirrer in the water model is estimated to be about 2 Newtons.

[0082] The specific method for simulating the movement of molten steel in a DC electric furnace under electromagnetic effects using a water model stirring method is as follows:

[0083] After filling a 1 / 8 scale water model with aqueous solution, place a 0.04m long stir bar at the bottom center of the water model. Place a magnetic stirrer at the bottom center outside the water model and power it on to rotate the stir bar at 500 rpm. Depending on the experimental requirements, a recording device can be placed outside the water model to record the solution flow state, and a mixing time recorder can be placed inside the water model to measure the mixing time. Alternatively, other devices can be used to measure the fluid motion parameters.

[0084] like Figure 3 As shown, when the electrodes of a DC electric furnace are energized, the molten steel rotates counterclockwise. In the water model, when the magnetic stirrer is energized, the stirring direction formed by the top or bottom stirrers is also counterclockwise.

Claims

1. A water model experiment method for simulating the movement of liquid in an electric furnace under electromagnetic effects, characterized in that, The specific steps are as follows: Step one, respectively calculate electromagnetic stirring force F generated by electric furnace to liquid steel prototype p And stirring force F generated by magnetic stirrer in water model m ; Step two, according to the similarity principle, the similarity criterion of the fluid flow process is selected to express the flow relationship by pressure difference, and the similarity relationship between the electromagnetic stirring force of the prototype and the stirring force of the water model is calculated to ensure the similarity of the two; Step three, according to the similarity relationship of the stirring force, the parameters and type of the magnetic stirrer are determined; Step four, according to the determined type of the magnetic stirrer, the magnetic stirring device including the magnetic stirrer and the stirrer is installed on the water model; The installation method includes two kinds of bottom or top installation: 1) bottom installation, after the water model is filled with liquid, the stirrer is placed in the bottom of the water model, the magnetic stirrer is placed on the bottom outside the water model, the stirrer is located directly above the center of the magnetic stirrer, and the magnetic stirrer is energized to drive the stirrer to rotate; 2) top installation, the stirrer is placed on the top of the water model liquid, a tray is placed on the stirrer, the magnetic stirrer is placed on the tray and located directly above the stirrer, and the magnetic stirrer is energized to drive the stirrer to rotate; Step five, according to the parameters of the magnetic stirrer, the magnetic stirrer is energized, the magnetic stirrer works to drive the stirrer to rotate at a constant speed, and the rotational flow of the water solution is formed to simulate the movement state of the steel liquid in the electric furnace under the electromagnetic effect.

2. The method for water modeling of the motion of the liquid in the electric furnace steel under the electromagnetic effect according to claim 1, characterized in that, In step one, the electromagnetic stirring force calculation formula of the steel liquid prototype is: F p ==I p B p L p sinα In the formula, F p represents the electromagnetic stirring force received by the liquid steel prototype; I p represents the current; B p represents the magnetic field strength generated by the current; L p represents the distance of the current to the steel melt; a is the angle between the direction of the current and the B p direction. The subscript p represents the prototype; The stirring force calculation formula of the magnetic stirrer in the water model is: F m = kB m I m Nd where F m represents the stirring force received by the liquid in the water model; k represents the proportional coefficient; B m represents the magnetic field strength generated by the magnetic stirrer; I m represents the magnetization of the magnetic stirrer; N represents the rotation speed of the magnetic stirrer; d represents the diameter of the magnetic stirrer; the subscript m represents the water model.

3. The method for water modeling of the motion of the liquid in the electric furnace steel under the electromagnetic effect according to claim 1, characterized in that, In step two, the calculation formula of the similarity criterion is: F p / S p *g / (ρ p *v p 2 )=F m / S m *g / (ρ m *v m 2 ) S p S represents the area of the prototype subjected to pressure; S m S represents the area of the water model subjected to pressure; g represents the acceleration of gravity, p p S represents the density of the prototype of the liquid steel, p m S represents the density of the prototype of the liquid steel, p p S represents the fluid velocity of the prototype of the liquid steel, v m S represents the fluid velocity of the prototype of the liquid steel, v 4. The method for water modeling of the motion of the liquid in the electric furnace steel under the electromagnetic effect according to claim 1, characterized in that, In step three, the parameters include the geometric size of the stirrer, the current, the speed, the shape and the stirring direction; further, the type of the magnetic stirrer is determined by the parameters.

5. The method for water modeling of the motion of the liquid in the electric furnace steel under the electromagnetic effect according to claim 1, characterized in that, In step four, the number of magnetic stirring devices is indefinite, the number of energized currents of the direct current or alternating current furnace determines the number of stirrers, and one stirrer is placed at each energized current; when the magnetic stirring device works, the rotation direction of the steel liquid caused by the direct current or alternating current furnace is determined by the electromagnetism rule of the left hand rule, and the rotation direction of the stirrer is consistent with it.

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