JPS58100953A - Controller for electromagnetic stirrer - Google Patents

Abstract

PURPOSE:To correct the velocity of stirring flow at the solidification interface automatically to prescribed values with min. electric current by detecting the flow rate of mold cooling water, the water temp. on the inlet side, the water temp. on the outlet side and the drawing speed of ingots, and controlling the current and frequency of an electromagnetic stirrer in accordance with the prescribed velocity of stirring flow. CONSTITUTION:Electric power is supplied from an electric power source 5 to an electromagnetic stirrer 4 installed in a mold 3 to generate rotating or moving magnetic fields, by which the molten steel 1 in the mold 3 is stirred. The flow rate Vw of the cooling water in a flow passage 6 is detected with a flowmeter 7 and the water temps. theta1, theta2 on the inlet and outlet sides are detected with temp. detectors 8, 9. On the other hand, the drawing speed V of ingots is detected with a detector 10 for the drawing speed of ingots and the prescribed velocity Vs of stirring flow at the interface where a solidified shell 2 contacts the molten steel 1 is set as desired with a setter 12 for the velocity of stirring flow. The water flow rate Vw, the water temps. theta1, theta2, and the set velocity Vs of flow are inputted to an arithmetic device 11 which sets the current and frequency so as to minimize the output current to the power source 5 for the stirrer 4.

Description

[Detailed Description of the Invention] Technical Field of the Invention The present invention relates to an electromagnetic stirring control device, and in particular, to optimally adjust the stirring force of an electromagnetic stirring device installed in a mold of continuous casting equipment in response to changes in casting conditions. 0 Regarding an electromagnetic stirring control device suitable for As is well known, the magnetic stirrer used in the 011M is a multi-phase 9: When the magnetic flux generated by the moving magnetic field or rotating magnetic field created by a current flows across the molten part of the slab in the mold, an induced pressure is generated. This device utilizes the principle that fluid motion is generated in molten steel by the magnetic pressure generated by the interaction between the flowing current and the magnetic flux. The effectiveness of improving slab quality using an electromagnetic stirring device depends on the stirring energy applied to the molten steel at the solidification interface of the slab. ffl Stirring energy is the product of the stirring flow rate generated in the molten steel and the time during which the stirring force is applied, and under certain casting conditions, as will be described later, the output frequency of the multiphase AC power supply that supplies power to the magnetic stirrer is and output current is determined.

Figure 1 is a schematic configuration diagram of a conventional electromagnetic stirring control device based on this principle. 4 is an electromagnetic stirrer for generating molten steel IK fluid motion in the mold 3 by electromagnetic force; 5 is a power source that provides a multiphase source to the electromagnetic stirrer 4; 6 13 is a current setting device for setting the current value of the power source 5; and 14 is a frequency & constant device for setting the frequency of the power source 5.

In such a configuration, in order to appropriately set the stirring energy of the molten steel l in the mold 3, the frequency f that can be set with the frequency setting device 14 of the power source 5 that provides a multiphase AC α source to the electric/magnetic stirring device 4 is set. Current setting device 13 sets the output current while keeping it constant.
I was adjusting it.

Problems with the Background Art However, this configuration has the disadvantage that when the @ mold conditions change and the thickness of the solidified shell in the mold 3 changes, the stirring energy at the solidified interface changes.
There is a problem that optimization and stability of the borrowing effect cannot be expected.

The reason for this will be explained below. Now, the magnetic flux density due to the moving magnetic field or rotating magnetic field passing through the molten steel at a distance X

The electromagnetic pressure generated by the synergistic effect of X degrees B and current density IX is P, the velocity of the fluid generated by the electromagnetic pressure PK, that is, the flow velocity fvX, and the magnetic flux density on the surface of the electromagnetic stirring device 4 is B. shall be. In this case, the flow rate ■
From Bernoulli's theorem, ■ cc-・・・・・・(
1) x x. Here, the electromagnetic pressure Px is P = i ・B (2) according to the teachings of magnetism.
x
When the frequency of the power source 5 of the electric magnetic stirring device 4 is f, the speed of the moving magnetic field or the rotating magnetic field is proportional to the frequency f, so 1cx-B=f-.--(3) x x . Therefore, from equation (1), equation (3), the flow velocity ■ becomes v OCB -ρ-... (4)X.

Here, the distance from the surface of the electromagnetic stirring device 40 to the surface of the mold 3 is dl, the specific resistance of the material of the mold 3 is ρ1°, the relative magnetic permeability is μm, the specific resistance of the molten steel 1 in the mold is ρ2°, and the relative magnetic permeability is /l 2 , the magnetic flux density Bx attenuates according to the relational expression due to the skin effect. Here, δ3. It is well known that δ is called the penetration thickness and there is a relationship between the two. Also, since the relative magnetic permeability μm and μ2 are usually 1i'', equations (5) and (6) are obtained.By the way, the surface magnetic flux density B is 1M, and the magnetic stirring device [
It is proportional to the magnetomotive force of 4. Since the magnetomotive force is proportional to the output power of power source 1, BC, cKI...
・l) It becomes J'1. Therefore, equation (4), equation (5), (
From equations 7) and 8, the flow velocity vx of molten steel is as follows. The average thickness of the solidified shell 2 of the molten steel l in the mold 3 is d,
Then, X = d, +(1;, that is, the flow velocity of molten steel 1 at the solidification interface is obtained from equation (9). In other words, the flow velocity of molten steel 1 is determined by not only the output current I and frequency 'f of the power supply but also the solidification Na2 Therefore, if the thickness of the solidified shell 2 changes due to a change in casting conditions, such as a change in slab drawing or a change in mold cooling conditions, the power frequency of the electromagnetic stirrer, '@1 flow, remains constant. The stirring flow rate at the 41# solid surface changes, which is not desirable.

Purpose of the Invention Accordingly, the purpose of the present invention, in view of the above-mentioned drawbacks of the prior art, is to make it possible to automatically adjust the stirring speed of 1M at the solidification interface to a predetermined value even if the solidification thickness changes due to changes in casting conditions. In addition to adjusting the power supply frequency and power supply current t for such purposes,
An object of the present invention is to provide an electromagnetic stirring control device for continuous casting equipment that makes it possible to minimize the power supply current f when adjusting X.

Structure of the Invention In order to achieve the above object, the present invention includes an electromagnetic stirring control device installed in a mold of continuous casting equipment, an electromagnetic stirring device that stirs the molten part of the cast slab, and a cooling device that cools the mold. A flow rate detection device that detects the flow rate vw of cooling water, a temperature detection installation that detects the temperature θ of the cooling water on the mold entry side, a temperature detection installation that detects the temperature θ2 of the cooling water on the mold exit side, and a slab a drawing speed detection device for detecting a drawing speed iv of the molten part of the slab;
Cooling water flow 1) vw, water temperature θ1. θ2. an arithmetic device that calculates and outputs at least one of the power supply frequency fi and the electric current based on the drawing speed V and the stirring flow rate v6; and a power source device that controls the current and frequency of the electromagnetic stirring device based on the calculation results of the ladle device. It consists of:

Examples of the invention Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 is a schematic configuration diagram of an electromagnetic stirring control device according to an embodiment of the present invention, in which the same parts as in FIG. 8 is an inlet temperature detection device that detects the cooling water temperature on the input side of the cooling water flow path 60; 9 is the cooling water flow path 6; 10 is a slab withdrawal speed detection device that detects the speed at which the slab is pulled out from the mold 3; 12 is a stirring flow rate setting device that sets the stirring flow rate v8; 11 calculates the outputs of the cooling water flow meter 7, the inlet temperature detection device 8, the outlet temperature detection device #9, the slab withdrawal speed detection device @ 10, and the stirring flow rate setting device 12, and calculates the output of 1 source 5. Frequency f and current f of a certain polyphase AC power supply: This is a calculation device that sets.

In such a configuration, its operation 'f: Before explaining.

Explain the theoretical basis underlying the operation.

(Since the average thickness d2 of the solidified shell 2 in Equation 9 is proportional to the amount of heat removed from the mold 3 that the molten steel 1 receives, the flow rate of the cooling water in the mold 3 is V, the cooling water inlet temperature is θ1, and the cooling water If the outlet temperature is 02, and the slab withdrawal speed is V, then the α(ri formula and αυ formula) are obtained.Here, A is the physical property of the mold material and the electric and magnetic Stirring device 14
B is a constant determined by the amount of installation, and B is a constant determined by the physical properties of the slab and cooling conditions. , from the 0-ka type, Kiryuko becomes. Here, C is a constant that determines the fluid characteristics of the molten steel 1. The right side of equation 031 has a factor that decreases and a factor that increases as the source frequency f increases, so the frequency f
It is clear that it has a minimum value for . Therefore, the frequency f which minimizes this current flow is more clearly given by or. At this time, the minimum value of the electric current worker is 0■
Equation: (15+Equation). However, D=2.720.

That is, the mold cooling water is 1"■, and the inlet water temperature is θ1.

The outlet water temperature θ and the slab drawing speed vf are detected, and the constant A,
If B and D are given and a magnetomotive force is applied to the electromagnetic stirrer #4 at the frequency and current given by equations 06) and 07), it is possible to provide a predetermined stirring flow rate at the solidification interface with the minimum power supply current. .

Based on this operating principle, the operation of the electromagnetic stirring control device of this embodiment having the configuration shown in FIG. 2 will be explained next.

An electromagnetic stirring device 4 installed in the mold 3 generates a rotating or moving magnetic field by being supplied with power from a power source 5, and stirs 1'ft of molten steel in the mold 3. The heat of the molten steel 1 is removed from the mold 3, so that a solidified shell 2 is formed in the portion in contact with the mold 3. The mold 3 is cooled by cooling water, but the flow rate is 1! Cooling water flow tv in flow path 6 at +7.

However, the inlet temperature detection device 8 detects the cooling water outlet temperature θ.

The cooling water outlet temperature θ is detected by the outlet temperature detection device [9]. On the other hand, the slab drawing speed V is detected by a slab drawing speed detection device 10. The predetermined stirring flow rate v6 at the surface of the solidified shell 2 in contact with the molten steel 1, that is, at the solidification interface, is arbitrarily set by the stirring flow rate setting device]2.

Cooling water flow detected by cooling water flow meter 7 iv.

Cooling water inlet temperature θ1 used laterally by the inlet temperature detection device 8
, the cooling water outlet temperature θ2 detected by the outlet temperature detection device 9
, @N loaf drawing speed V detected by the single drawing speed detection device 10
In addition, the setting value 8 of the stirring flow rate set in the stirring flow rate setting device 12 is inputted to the calculation device 11, where the equations 06) and Q7) described earlier are performed, and the electric, magnetic, The output set value and frequency f to the power supply 5 for the stirring device 4 are obtained. That is, the frequency f and electric current of the ta stirring device 4 are automatically corrected so as to satisfy the 0Φ equation 07).

In this way, the mold cooling water flow rate, inlet temperature, outlet temperature, and slab drawing speed are detected, and together with the set value of the stirring flow rate (
16) By setting the 'N1 current and frequency of the electromagnetic stirrer so as to satisfy the relationship shown in the following equation, the magnetomotive force can be adjusted, and the mold can be maintained with the minimum current even when the casting conditions change. The stirring flow rate at the inner solidification interface can be automatically adjusted to a predetermined value.

Effects of the Invention As described above, according to the present invention, when performing electromagnetic stirring of slabs, even if the casting conditions change, the stirring flow rate at the solidification interface can be automatically controlled to a predetermined value with the minimum current. This makes it possible to obtain a new electromagnetic stirring device that makes it possible to do this.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram of the conventional electromagnetic stirring device 1,
The figure is a schematic configuration diagram of an electromagnetic stirring control device according to an embodiment of the present invention. l... Molten steel, 2... Solidified shell, 3... Mold, 4...
・Electromagnetic stirring device, 5...Power source, 6...Cooling water flow path, 7...Cooling water flow f needle (flow rate detection device), 8...In (LU11 temperature detection device, 9... Outlet temperature detection device,
10. Slab drawing speed detection device'+1.1...Arithmetic device,
12...Agitation flow rate setting device C Applicant's representative Kiyoshi Ikuta (15) Figure 1

Claims (1)

[Claims] 1. An electromagnetic stirring device that is installed in a mold of continuous casting equipment and stirs the molten part of a mold-like slab, and a flow rate detection device that determines the scene vW of cooling water that cools the mold. , a temperature detection device that detects the temperature θ1 of the cooling water on the mold entry side, a temperature detection device that detects the temperature θ2 of the cooling water of m molds, and a drawing speed detection device that detects the drawing speed V of the slab. , an agitation flow rate setting device for setting the agitation flow rate (8) of the molten part of the slab, a cooling water flow rate VW, a water temperature θ3. θ3, drawing speed ■, stirring flow rate v8
It is characterized by comprising a calculation device that calculates and outputs at least one of the power supply frequency f and the current frequency based on the calculation result, and a power supply device that controls the current and frequency of the electromagnetic stirring device based on the calculation results of the calculation device. Lightning, magnetic stirring control device. Claim 1 characterized in that the calculation is performed by setting the power supply frequency f to a predetermined setting value and further setting constants A, B, and C using two calculation units at °.
The electromagnetic stirring control device described in . 3. In the arithmetic device, after setting constants A, B, and D, the following calculation is performed: 1 = DV8 (A + B) (θ2 - θ, )) The electromagnetic stirring control device described in .