Metal melting method

Abstract

To provide a metal melting method capable of efficiently melting reduced iron in a short time in an electric furnace using an electromagnetic stirring device.SOLUTION: A metal melting method according to the present invention is a metal melting method in an electric furnace having at least one upper electrode, a raw material charging pipe provided on a side surface or an upper surface of a furnace body, and an electromagnetic stirring device provided on a lower surface of a furnace bottom. The method includes a charging step of charging a raw material to be melted from the raw material charging pipe onto a bath surface, a melting step of melting the raw material to be melted using an arc as a heat source while supplying the raw material to be melted into the furnace, and a flow forming step of forming a flow of molten iron from a position where the charged raw material to be melted reaches the bath surface of the molten iron toward a high-temperature region in the furnace by an electromagnetic stirring force applied by the electromagnetic stirring device.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for melting metal.

Background Art

[0002] Iron sources produced by the blast furnace method are produced by reducing iron ore with coke, so the amount of CO2 generated is large. As a means of reducing the amount of CO2 generated, there is a method of producing molten iron by melting reduced iron in an electric furnace and producing molten steel using an existing steelmaking process centered around a converter. To improve the productivity of producing molten steel in an electric furnace, it is important to increase the melting rate of reduced iron. The melting of reduced iron is carried out by an arc generated from an upper electrode provided at the center of the electric furnace to the surface of the molten iron. Therefore, the temperature of the molten iron is the highest near the furnace center, and in order to increase the melting rate of reduced iron, it is preferable to introduce reduced iron into the high-temperature spot near the furnace center.

[0003] However, since there is an upper electrode near the furnace center, it is not always easy to install a raw material input pipe for introducing reduced iron at the furnace center. Therefore, in many cases, the raw material input pipe has to be installed at a position away from the furnace center. In such a case, it is preferable that the reduced iron is transported to the high-temperature spot by the flow of the molten iron after being introduced. The advantages of flowing the molten iron include, in addition to transporting the reduced iron, equalizing the temperature of the molten iron and promoting heat supply to the reduced iron. Patent Document 1 discloses a technique in which an electromagnetic stirring device is arranged under the bottom of an electric arc furnace, and the molten metal in the electric arc furnace is stirred so that the molten metal is mixed with the remaining molten steel.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the melting of reduced iron using an electric furnace as in the past, there has been a problem that even when an electromagnetic stirring device is used, the productivity of molten iron has not been sufficiently improved. In Patent Document 1, it is unclear how the stirring flow by the electromagnetic stirring device affects the transportation and temperature rise of the reduced iron floating on the interface of the molten iron. Also, the direction and strength of the application of the electromagnetic force by the electromagnetic stirring device for further improving the melting efficiency of the reduced iron are unclear. That is, in the operation of the electric furnace for melting reduced iron, there are many unclear points regarding the appropriate conditions related to the electromagnetic stirring conditions.

[0006] Therefore, an object of the present invention is to provide a metal melting method capable of more efficiently melting reduced iron in a short time in an electric furnace using an electromagnetic stirring device.

Means for Solving the Problems

[0007] [1] A metal melting method in an electric furnace including at least one upper electrode, a raw material input pipe provided on a side surface or an upper surface of a furnace body, and an electromagnetic stirring device provided on a lower surface of a furnace bottom, the method including: an input step of inputting a melting raw material onto a molten metal surface from the raw material input pipe; a melting step of melting the melting raw material using an arc as a heat source while supplying the melting raw material into the furnace; and a flow forming step of forming a flow of the molten iron such that the input melting raw material moves from a position where it reaches the molten metal surface of the molten iron toward a high-temperature region in the furnace by the electromagnetic stirring force applied by the electromagnetic stirring device. [2] When the direction of the horizontal component of the electromagnetic force acting on the molten iron by the electromagnetic stirring device is a first direction, when the bath depth of the molten iron is H (m), the frequency of the electromagnetic stirring device is f (Hz), the magnetic permeability of the molten iron is μ (H / m), and the conductivity of the molten iron is σ (×10 6 S / m), when the following formula (i) is satisfied, the position where the melting raw material reaches the molten metal surface of the molten iron is located upstream of the flow of the molten iron in the first direction from the furnace center of the electric furnace, and when formula (i) is not satisfied, the position where the melting raw material reaches the molten metal surface of the molten iron is located upstream of the flow of the molten iron in a second direction opposite to the first direction from the furnace center of the electric furnace. The metal melting method according to [1]. [Number] [3] In the above melting step, at the timing when the bath depth H (m) of the molten iron in the furnace no longer satisfies formula (i), reverse the direction of the horizontal component of the electromagnetic force acting on the molten iron by the electromagnetic stirring device. The method for melting metal according to [2]. [4] In the above charging step, at the timing when the bath depth H (m) of the molten iron in the furnace no longer satisfies formula (i), change the position where the melting raw material reaches the surface of the molten iron from the upstream side of the flow of the molten iron in the first direction closer to the furnace center to the upstream side of the flow of the molten iron in the second direction. The method for melting metal according to [2]. [Advantages of the Invention]

[0008] According to the above configuration, in an electric furnace using an electromagnetic stirring device, the reduced iron charged into the furnace is more likely to reach a higher temperature region. Therefore, the reduced iron can be melted more efficiently in a shorter time. [Brief Description of the Drawings]

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

[0010] With reference to the accompanying drawings, preferred embodiments of the present invention will be described in detail below. In this specification and the drawings, components having substantially the same functional configuration are denoted by the same reference numerals, and redundant descriptions are omitted.

[0011] (Structure of the electric furnace according to this embodiment) FIG. 1 is a cross-sectional view of an electric furnace 1 according to an embodiment of the present invention. In the figure and the following description, three mutually orthogonal directions are defined as the +x direction, +y direction, and +z direction. Although not shown, the direction opposite to the +x direction is the -x direction, the direction opposite to the +y direction is the -y direction, and the direction opposite to the +z direction is the -z direction.

[0012] As shown in the figure, the electric furnace 1 includes a ceiling 2, a furnace wall copper panel 3, a furnace wall refractory 4, and a furnace bottom refractory 5. At least one upper electrode 6 is provided on the ceiling 2. In this embodiment, three upper electrodes 6 are provided. The raw material input pipe 7 is provided on the side surface or the upper surface of the furnace body. The furnace wall refractory 4 is provided with a tapping hole 8 for discharging the molten iron 21 and a slag hole 9 for discharging the electric furnace slag 22. An electromagnetic stirring device (EMS: Electro Magnetic Stirrer) 10 is provided on the lower surface of the furnace bottom. Pr in the figure indicates the input position where the molten raw material introduced from the raw material input pipe 7 reaches the surface of the molten iron 21. Also, R in the figure indicates the distance between the furnace center C and the input position Pr as viewed from above. Further, H in the figure indicates the bath depth.

[0013] As the electric furnace 1, either a tilting type in which the furnace body tilts or a stationary type in which the furnace body does not tilt can be used. Also, as the electric furnace 1, a direct current electric furnace or an alternating current electric furnace can be used, but it is more preferable to use an alternating current electric furnace. From the raw material input pipe 7, as the melting raw material, one or two of iron-containing scrap and reduced iron are input onto the molten iron 21 surface. As the reduced iron, DRI (Direct Reduced Iron) or HBI (Hot Briquetted Iron) can be used. Iron-containing dust may be input into the furnace as an iron source. As the iron-containing dust, granulated converter dust can be used.

[0014] An arc 20 is emitted from the upper electrode 6. In the electric furnace 1, while supplying the melting raw material into the furnace, the melting raw material is melted using the arc 20 as a heat source to produce molten iron 21. By applying an electromagnetic stirring force to the molten iron 21 by the electromagnetic stirring device 10 and causing a circulating flow in the molten iron 21 and the electric furnace slag 22, it is possible to promote heat transfer and melting of the molten iron 21 surface and the electric furnace slag 22.

[0015] As will be described later, the electromagnetic stirring forces FL1, FL2, FL3 applied by the electromagnetic stirring device 10 form a flow of the molten iron 21 that goes from the position where the charged melting raw material reaches the molten iron 21 surface toward the high-temperature region Rh in the furnace.

[0016] FIG. 2 is a cross-sectional view taken along line II-II of the electric furnace 1 shown in FIG. 1. The cross-section of the electric furnace 1 may be circular, or may be an eccentric furnace body tapping method in which the furnace body shape has a tapping hole protruding. In the electric furnace 1 according to the present embodiment, as shown in the figure, the cross-section is circular. D in the figure indicates the inner diameter of the electric furnace 1, and Rh indicates the high-temperature region. The high-temperature region Rh is a region where the temperature of the molten iron 21 is higher than other regions of the molten metal surface. As shown in the figure, here, the high-temperature region Rh is a circle with a diameter d centered on the furnace center C and in contact with the three upper electrodes 6 on the furnace wall side. Also, the region A is in contact with the high-temperature region Rh and is a quadrilateral with side lengths of d and D / 2. Later, the results of examining the relationship between the flow velocity of the molten iron 21 on the molten metal surface and the attenuation coefficient α of the electromagnetic force acting on the molten iron 21 using the high-temperature region Rh and the region A will be described.

[0017] (Examination of the flow of molten iron) As shown in FIG. 1, when the electromagnetic stirring device 10 applies electromagnetic stirring forces FL1, FL2, and FL3, a horizontal component of the electromagnetic force acts on the molten iron 21 near the furnace bottom in the +x direction, which is the first direction. As a result, a flow is formed in the molten iron 21 near the furnace bottom in the +x direction (F1 in the figure). The molten iron 21 in which this flow is formed reverses the flow near the molten metal surface of the furnace wall and flows in the -x direction (the second direction) on the molten metal surface (F2 in the figure). Hereinafter, the +x direction (the first direction) will also be referred to as the "stirring direction", and the second direction will also be referred to as the "direction opposite to the stirring direction".

[0018] The electromagnetic stirring forces FL1, FL2, and FL3 applied by the electromagnetic stirring device 10 attenuate as they move away from the furnace bottom. That is, the electromagnetic stirring forces FL1, FL2, and FL3 decrease in the order of FL3, FL2, and FL1 as shown in the figure. Therefore, when the bath depth H is shallow, a sufficient electromagnetic stirring force FL1 also acts on the molten iron 21 near the molten metal surface, and the molten iron 21 on the molten metal surface flows in the stirring direction (F3 in the figure). Therefore, it can be said that depending on the depth of the bath depth H, the flow of the molten iron 21 on the molten metal surface is antagonistic, and the flow state of the molten metal surface changes.

[0019] FIG. 3 is a diagram for explaining the difference in the flow of molten iron 21 on the molten metal surface depending on the bath depth H. In FIG. 3, (a) shows the flow of molten iron 21 when the bath depth H is deep, and (b) shows the flow of molten iron 21 when the bath depth H is shallow. As shown in (a), when the bath depth H of the molten iron 21 is deep, sufficient electromagnetic stirring force FL1 does not act on the molten iron 21 near the molten metal surface by the electromagnetic stirring device 10, and the flow in the stirring direction of the molten iron 21 (F3 in the figure) weakens. Therefore, the flow in the direction opposite to the stirring direction of the molten iron 21 (F2 in the figure) becomes dominant.

[0020] On the other hand, as shown in (b), when the bath depth H of the molten iron 21 is shallow, sufficient electromagnetic stirring force FL1 acts on the molten iron 21 near the molten metal surface by the electromagnetic stirring device 10, and the flow in the stirring direction of the molten iron 21 (F3 in the figure) is formed. Hereinafter, the flow pattern in which the flow of the molten iron 21 in the stirring direction is dominant as in (b) is referred to as the "EMS-dominated flow pattern".

[0021] (Bath depth conditions for the EMS-dominated flow pattern) In the EMS-dominated flow pattern, as described above, the electromagnetic force applied by the electromagnetic stirring device 10 attenuates as it moves away from the furnace bottom. Therefore, assuming that the distance in the depth direction (+y direction) from the electromagnetic stirring device 10 at the furnace bottom is z (m), the attenuation coefficients α' of the magnetic field B(z) and the eddy current J(z) in the molten iron 21 are represented by the following equations (1) and (2). Note that the attenuation coefficient α' is a quantity representing, for example, B(z) / B(z = 0), δ is the penetration depth (m), f is the frequency (Hz) of the electromagnetic stirring device 10, μ is the magnetic permeability (H / m) of the molten iron 21, and σ is the conductivity (×10 6 S / m) of the molten iron 21.

[0022]

Equation

[0023] In addition, since the electromagnetic force applied to the molten iron 21 is represented by the product of the magnetic flux density and the current, the attenuation coefficient α of the electromagnetic force is represented by the following equation (3). α = exp(-2z / δ) ···(3)

[0024] Figure 4 is a graph showing an example of the distribution of electromagnetic force with respect to the depth direction distance z from the electromagnetic stirring device 10 obtained as a result of numerical analysis. In the graph, the results of the simulation are plotted, and the calculation results using Equation (3) are shown as a solid line. The simulation was based on electromagnetic field analysis carried out according to the method described in Nobuhiro OKADA, Masayuki KAWAMOTO and Shintaro OHGA: "Materials Science and Engineering" 424 (2018) 012031. The attenuation coefficient α of the electromagnetic force was calculated based on the magnitude of the stirring direction component of the electromagnetic force.

[0025] When the attenuation coefficient α of the electromagnetic force is large, the electromagnetic stirring forces FL1, FL2, FL3 become large. As shown in the figure, it can be seen that the electromagnetic force distribution attenuates as it moves away from the electromagnetic stirring device 10. Also, it can be seen that the attenuation coefficient α based on the simulation results of the electromagnetic force distribution and the calculation results of the attenuation coefficient α using Equation (3) generally agree.

[0026] Here, using the high temperature region Rh and region A, the relationship between the flow velocity of the molten iron 21 on the molten metal surface and the attenuation coefficient α of the electromagnetic force acting on the molten iron 21 will be described. In region A shown in Figure 2, the average value of the flow velocity of the molten iron 21 on the molten metal surface was calculated, and the relationship between the bath depth H and the attenuation coefficient α was calculated. Here, the current frequency of the electromagnetic stirring device 10 was 0.8 Hz, and the physical property values of the molten iron 21 were permeability μ = 1.0 H / m and conductivity σ = 0.7×10 6 S / m.

[0027] The following calculation results are obtained by numerical simulation that can reproduce the behavior of melting solid particles by introducing a large number of them from above the molten iron pool surface in the electric furnace vessel. The numerical simulation was carried out by inputting the electromagnetic force obtained as the simulation result of the above electromagnetic field analysis as the external force term in the heat fluid flow analysis. The numerical simulation combines the method described in K. Kihara and N. Okada: "Chemical Engineering Science", 270 (2023), 118507 (solid-gas-liquid three-phase flow numerical analysis model) that can simulate the behavior of a large number of solid particle groups, and the method described in J. Ni and C. Beckermann: "Metallurgical Transactions B", 22 (1991), 349 (phase change model) that is widely applied to multiphase flow models.

[0028] More specifically, the "solid-gas-liquid three-phase flow numerical analysis model" was used as the method for calculating the fluid flow of the gas-liquid two-phase flow and the movement of the solid phase, and the "phase change model" was used for calculating the transport diffusion of the temperature field and the component concentration field and the phase change between the solid and the liquid, that is, solidification and melting. A program was created to numerically solve the governing equations described in these by discretizing them using the finite volume method, which is one of the calculation methods for multiphase flow analysis, and the above numerical simulation was realized.

[0029] Note that the simulation model used in this numerical simulation can also simulate the behavior of solids floating on the interface as described above, and can predict how the introduced solid particle groups float and move on the interface and where they melt. In the simulation, with the state of molten iron contained in the electric furnace vessel at the actual machine scale as the initial condition, the intensity of the applied electromagnetic stirring force and the bath depth of the molten iron pool were varied in various ways to analyze the flow pattern of the molten iron pool. Furthermore, the solid input positions were varied in various ways to analyze the behavior of the introduced reduced iron particle groups floating, transporting, and melting.

[0030] Figure 5 is a graph showing the relationship between the stirring direction component of the average flow velocity of the molten iron 21, the attenuation coefficient α, and the bath depth H. In Figure 5, (a) shows the relationship between the stirring direction component of the average flow velocity of the molten iron 21 and the attenuation coefficient α, and (b) shows the relationship between the stirring direction component of the average flow velocity of the molten iron 21 and the bath depth H. In the graph, when the surface flow velocity of the molten metal is positive, it indicates that the flow of the molten iron 21 is in the EMS-dominated pattern.

[0031] From the graph of (a), it can be seen that when the attenuation coefficient α is 0.03 or more, a flow in the stirring direction is formed in the molten iron 21 at the surface of the molten metal, resulting in an EMS-dominated flow pattern. Also, from the graph of (b), it can be seen that when the bath depth H is about 1.3 m or less, a flow in the stirring direction is formed in the molten iron 21 at the surface of the molten metal, resulting in an EMS-dominated flow pattern.

[0032] Therefore, in equations (2) and (3), by applying the value of the distance z from the electromagnetic stirring device 10 when the attenuation coefficient α of the electromagnetic force is 0.03, the conditions for the molten iron 21 to be in the EMS-dominated flow pattern at the surface of the molten metal are obtained. This condition is represented by the following equation (4).

[0033]

Number

[0034] Figure 6 is a diagram showing the result of numerical analysis of the flow velocity distribution of the molten iron 21 at the surface of the molten metal. In Figure 6, (a) shows the flow velocity distribution of the molten iron 21 when the bath depth H is 0.9 m, and (b) shows the flow velocity distribution of the molten iron 21 when the bath depth H is 1.8 m. Here, the current frequency of the electromagnetic stirring device 10 is 0.8 Hz, and the physical property values of the molten iron 21 are magnetic permeability μ = 1.0 H / m and conductivity σ = 0.7×10 6 S / m.

[0035] As shown in the figure, when the bath depth H is shallow as in (a), it can be seen that a flow in the stirring direction is formed in the molten iron 21 at the surface of the molten metal, resulting in an EMS-dominated flow pattern. Also, when the bath depth H is deep as in (b), it can be seen that a flow in the direction opposite to the stirring direction is formed in the molten iron 21 at the surface of the molten metal, and it is not in the EMS-dominated flow pattern.

[0036] In addition, when the current of the electromagnetic stirring device 10 is increased, the electromagnetic stirring force applied to the molten iron 21 becomes stronger overall. However, at the surface of the molten metal, Equation (4), which is the condition for the flow of the molten iron 21 to become the EMS-dominated flow pattern, does not depend on the current value. That is, the range of the bath depth at which the flow of the molten iron 21 becomes the EMS-dominated flow pattern does not depend on the current value of the electromagnetic stirring device 10. This is because even if the current of the electromagnetic stirring device 10 changes and the electromagnetic force applied to the molten iron 21 changes overall, only the flow velocity in the stirring direction and the flow velocity in the direction opposite to the stirring direction of the molten iron 21 change together, and the balance of their strengths does not change. As a result, the flow pattern itself does not change.

[0037] (Effect on the dissolution efficiency of reduced iron when the input position of reduced iron is changed) Fig. 7 is a graph showing the relationship between the input position Pr of reduced iron and the dissolution time of reduced iron. The dissolution time of reduced iron is the average dissolution time per piece of reduced iron. The distance R between the furnace center C and the input position Pr of reduced iron is set with the upstream side of the flow of the molten iron 21 as positive, and the radius of the high-temperature region Rh is 1.5 m. Also, the bath depth H is 1.8 m, the total mass of the molten iron 21 is 500 ton, and the input rate of reduced iron is 8 ton / min. The equivalent spherical diameter of the reduced iron to be input is 50 mm, and the density is 5000 kg / m 3 and when the input rate is converted to the number, it is about 24446 pieces / min.

[0038] In addition, the electromagnetic stirring force per unit volume (hereinafter referred to as the effective electromagnetic stirring force FL) is the value obtained by dividing the volume integral value of the electromagnetic stirring forces FL1, FL2, and FL3 in the molten iron in the furnace by the total volume of the molten iron 21. Further, the dotted line in the figure is an approximate curve of the quadratic function obtained by the least squares method for the data under the conditions of each effective electromagnetic stirring force FL.

[0039] In order to improve the dissolution efficiency of reduced iron, it is preferable that the reduced iron flows from the charging position Pr to the high-temperature region Rh. That is, the charging position Pr of the reduced iron is preferably on the upstream side of the flow of the molten iron 21 on the molten metal surface as viewed from the furnace center C. As shown in the figure, it can be seen that regardless of the value of the effective electromagnetic stirring force FL, the dissolution time of the reduced iron is shorter when the charging position Pr is near the furnace center C and longer when it is far from the furnace center C. Also, the charging position Pr where the dissolution time is the shortest is on the upstream side of the flow of the molten iron 21 on the molten metal surface regardless of the value of the effective electromagnetic stirring force FL. The charging position Pr becomes farther from the furnace center C as the effective electromagnetic stirring force FL increases.

[0040] Furthermore, in the graph, on the left side of R = 0 m, the dissolution time of the reduced iron has little dependence on the magnitude of the effective electromagnetic stirring force FL, but on the right side of R = 0 m, the larger the effective electromagnetic stirring force FL, the shorter the dissolution time of the reduced iron. From this, it can be said that when the effective electromagnetic stirring force FL is large, if the reduced iron is charged on the upstream side of the flow of the molten iron 21 toward the furnace center C, the dissolution efficiency of the reduced iron will be further improved.

[0041] As shown in the figure, when the effective electromagnetic stirring force FL is applied so that the flow of the molten iron 21 on the molten metal surface moves the reduced iron in the direction of the high-temperature region Rh with respect to the charging position Pr of the reduced iron, it is effective in improving the dissolution rate of the reduced iron. On the other hand, it can be seen that when the effective electromagnetic stirring force FL is applied in the direction opposite to the direction in which the flow of the molten iron 21 moves the reduced iron to the high-temperature region Rh, a sufficient effect in improving the dissolution rate of the reduced iron cannot be obtained.

[0042] (Effect) As described above, the method for melting metal in the electric furnace 1 according to the present embodiment includes a charging step of charging the melting raw material onto the molten metal surface from the raw material charging pipe 7, and a melting step of melting the melting raw material using the arc 20 as a heat source while supplying the melting raw material into the furnace. Further, it includes a flow forming step of forming a flow of the molten iron 21 such that the charged melting raw material moves from the position where it reaches the molten metal surface of the molten iron 21 toward the high-temperature region Rh in the furnace by the electromagnetic stirring forces FL1, FL2, and FL3 applied by the electromagnetic stirring device 10. According to such a method for melting metal, in the electric furnace 1, the reduced iron charged into the furnace can more easily reach the higher-temperature region Rh, and the reduced iron can be melted more efficiently in a shorter time.

[0043] From the above, the direction of the flow of the molten iron 21 on the molten metal surface greatly affects the movement and melting rate of the reduced iron. The flow of the molten iron 21 on the molten metal surface is preferably determined by Equation (4). That is, the flow of the molten iron 21 on the molten metal surface is preferably determined to be formed in the stirring direction when the bath depth H of the molten iron 21 satisfies Equation (4), and to be formed in the direction opposite to the stirring direction when the bath depth H of the molten iron 21 does not satisfy Equation (4). By charging the reduced iron at a suitable position with respect to the flow of the molten iron 21 thus determined, the melting efficiency of the reduced iron is improved.

[0044] Further, at the timing when the molten iron 21 having a bath depth H satisfying Equation (4) increases to a bath depth H not satisfying Equation (4), by reversing the direction of the horizontal component of the electromagnetic force acting on the molten iron 21 by the electromagnetic stirring device 10, the direction of the flow of the molten iron 21 on the molten metal surface can be kept constant before and after that timing. Thereby, it is possible to realize an operation with high melting efficiency of the reduced iron while keeping the charging position Pr of the reduced iron fixed.

[0045] Further, at the timing when the molten iron 21 having a bath depth H satisfying Equation (4) increases to a bath depth H not satisfying Equation (4), by changing the charging position Pr of the reduced iron to the side opposite to the furnace center C, the reduced iron can be continuously charged at a suitable position. Thereby, it is possible to realize an operation with high melting efficiency of the reduced iron while keeping the direction of the horizontal component of the electromagnetic force acting on the molten iron 21 by the electromagnetic stirring device 10 fixed.

[0046] The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to these examples. It is obvious that those skilled in the technical field to which the present invention pertains can conceive of various modification examples or correction examples within the scope of the technical idea described in the claims, and these are naturally understood to belong to the technical scope of the present invention.

Explanation of Reference Signs

[0047] 1... Electric furnace, 2... Ceiling, 3... Furnace wall copper panel, 4... Furnace wall refractory, 5... Furnace bottom refractory, 6... Upper electrode, 7... Raw material input pipe, 10... Electromagnetic stirring device, 20... Arc, 21... Molten iron, 22... Electric furnace slag, H... Bath depth, Pr... Input position, Rh... High temperature region.

Claims

1. A method for melting metal in an electric furnace comprising at least one upper electrode, a raw material input pipe provided on a side surface or an upper surface of a furnace body, and an electromagnetic stirring device provided on a lower surface of a furnace bottom, the method comprising: An input step of inputting a melting raw material onto a molten metal surface from the raw material input pipe; A melting step of melting the melting raw material using an arc as a heat source while supplying the melting raw material into the furnace; A flow forming step of forming a flow of the molten iron such that the melting raw material reaches a high temperature region in the furnace from a position where the input melting raw material reaches the molten metal surface by an electromagnetic stirring force applied by the electromagnetic stirring device; A metal melting method including the above steps.

2. When the direction of the horizontal component of the electromagnetic force acting on the molten iron by the electromagnetic stirring device is defined as a first direction, When the bath depth of the molten iron is H (m), the frequency of the electromagnetic stirring device is f (Hz), the magnetic permeability of the molten iron is μ (H / m), and the conductivity of the molten iron is σ (×10 ６ S / m), when the following formula (i) is satisfied, the position where the melting raw material reaches the molten iron surface is located upstream of the molten iron flow in the first direction from the furnace center of the electric furnace, and when formula (i) is not satisfied, the position where the melting raw material reaches the molten iron surface is located upstream of the molten iron flow in the second direction, which is opposite to the first direction, from the furnace center of the electric furnace. The method for melting metal according to claim 1. 【Number 1】

3. In the melting step, The method for melting metal according to claim 2, wherein the direction of the horizontal component of the electromagnetic force acting on the molten iron by the electromagnetic stirring device is reversed at a timing when the bath depth H (m) of the molten iron in the furnace no longer satisfies formula (i).

4. In the input step, The method for melting metal according to claim 2, wherein the position where the melting raw material reaches the molten metal surface is changed from the upstream side of the flow of the molten iron in the first direction closer to the furnace center to the upstream side of the flow of the molten iron in the second direction at a timing when the bath depth H (m) of the molten iron in the furnace no longer satisfies formula (i).

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