JP2003130547A - AC electric furnace - Google Patents

Abstract

(57) [Summary] [PROBLEMS] In an AC electric furnace for producing molten metal,
Product productivity is improved by stirring the molten metal. SOLUTION: A linear (or circular) molten metal stirring device 4 is provided on the bottom side of an AC electric furnace tank 1 having a three-phase AC electrode for generating a molten metal in a vicinity from the outside. Then, the multi-phase electrode array of the electromagnetic stirrer 4 is driven by periodically switching alternately between a normal rotation state and a reverse rotation state by a power supply means. Further, the time ratio between the normal rotation state and the reverse rotation state and the cycle thereof are determined by a timing determining means by a program or the like, and the power supply means is periodically switched.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an AC electric furnace for producing molten metal, and more particularly to an electric furnace effective for stirring molten metal which improves the productivity of the product.

[0002]

2. Description of the Related Art Conventionally, an AC type electric furnace tank has three vertical 3 points along the center line of a cylindrical tank having a circular bottom surface and at the periphery thereof, at the apex of a virtual equilateral triangle Δ on a horizontal plane facing the bottom surface. Two electrode cylinders are provided in parallel, and a Δ-shaped electrode is formed by these three AC electrode cylinders. In an AC electric furnace, a metal material to be melted is put in a tank, and a multiphase AC voltage is applied to the three electrodes formed in a triangle shape by the above three AC electrode columns. A three-phase AC voltage is applied between the electrode columns, and an AC current corresponding to the three-phase AC voltage flows. The metallic material melts due to resistive heat generation when an alternating current flows. In such an AC electric furnace,
Since the electric current flows in the tank through the part with low electrical resistance,
In the electric furnace tank, the current flow is poor at the bottom circumference. In the AC electric furnace, since the Δ-shaped electrode is formed by the three electrode cylinders, the electric current flows in a wider area in the tank than in the DC electric furnace. However, since the electric current does not flow well in the circumferential portion at the bottom of the electric furnace tank, there is a temperature difference between the molten metal and the inside of the tank.

On the other hand, in order to improve the flow of molten metal in the circumferential portion at the bottom of the electric furnace tank, an electromagnetic stirrer is mounted from the outside on the bottom surface of the electric furnace tank. It is known that this electromagnetic stirrer has a linear shape forming a linear motor or a circular shape forming an induction motor. However, since a uniform magnetic field flow is formed in a certain direction, the molten metal flow is not sufficient. Therefore, there is still a difference in temperature of the molten metal between the inside of the tank and the inside.

[0004]

In the above AC electric furnace, since the temperature difference of the molten metal between the inside of the tank and the inside of the tank occurs at the circumferential portion of the tank bottom, the temperature of the molten metal in the tank is Poor uniformity and reduced productivity. It is an object of the present invention to provide an AC electric furnace capable of solving the above problems by sufficiently stirring molten metal and exhibiting high productivity.

[0005]

An AC electric furnace according to the present invention includes an AC electric furnace tank having a multi-phase AC electrode for producing molten metal therein, and a lower part of the AC electric furnace tank from the outside. An alternating current electric furnace configured with a molten metal stirring device arranged in a straight line or a circular shape in proximity to each other is provided with a power supply means for alternately driving the molten metal stirring device between a normal rotation state and a reverse rotation state. It is characterized by that.

Further, according to the present invention, in the AC electric furnace, the holding time ratio between the normal rotation state and the reverse rotation state and the switching cycle between the respective states are determined, and the power supply means is periodically switched. It is provided with a timing determining means.

[0007]

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described in detail below with reference to the drawings. FIG. 1 is a block diagram of an embodiment of the present invention showing a molten metal agitator arranged in a straight line (or circular shape) operating in a normal rotation state together with an AC electric furnace tank. In the figure, 1 is an AC electric furnace tank, 2 is a triangle
3 three-phase alternating current electrodes arranged in a shape, 3 is a molten metal material, and 4 is a molten metal stirring device arranged linearly (or circularly). The molten metal agitator 4 is composed of multi-phase electrodes arranged in a linear shape (or a circular shape).

A molten metal agitating device 4 formed of a linear (or circular) multiphase electrode array is provided below the outside of the AC electric furnace 1. When a three-phase AC voltage is applied to the molten metal stirrer 4 mounted immediately below the outside of the AC electric furnace 1, the generated magnetic field proceeds in a direction determined according to the phase of the AC voltage. Therefore, the molten metal material is pulled in synchronization with the progress of the magnetic field and proceeds in the traveling direction of the magnetic field. This gives a stirring force to the molten metal. Due to the stirring force applied to the molten metal by the flow of the molten metal in the traveling direction of the magnetic field, the molten metal staying at the bottom of the tank flows, but it cannot be said that sufficient stirring force is applied. FIG. 2 is a development view showing a multiphase electrode obtained by cutting the structure of the molten metal agitator 4 of FIG. 1 at AA ′. In FIG. 2, 7 is a switching means for switching between a normal rotation state and a reverse rotation state, and 8 is an inverter. These elements are included in the power supply means 10 of FIG. In the normal rotation state, a three-phase AC voltage is applied to the three-phase electrodes in the order of UVW. Therefore, the molten metal is driven to the right in the forward rotation state. Next, when a three-phase AC voltage is applied in the reverse direction, the molten metal is driven leftward. In the reverse rotation state, the V phase and the W phase are connected in reverse in FIG. 1, and the AC voltage is applied in the order of UWV. In the present invention, as shown in FIG. 3A, a three-phase AC voltage is alternately applied to the electrodes of the molten metal agitator in the forward rotation state and the reverse rotation state.

The normal rotation state and the reverse rotation state are switched at an equal time period determined by a program or the like, or at a forward rotation / reverse rotation time ratio period previously determined by a program or the like. For example, the switching time constant is 10 to 100 seconds, and can be set arbitrarily for forward rotation and reverse rotation. The program and the like are used in a computer and the like, and the program and the like, the computer and the like, the control device and the like constitute the timing determining means 9. The switching is performed by a power supply means 10 having a built-in switching means 7 such as a mechanical power switch or a semiconductor power switch. FIG. 3B is a system diagram showing the timing determining means 9 for performing the above control together with the power supply means 10. By repeating the normal rotation state and the reverse rotation state in this way, the molten metal is alternately driven in the right direction and the left direction, and when the normal rotation state and the reverse rotation state are switched, a disturbance occurs in the molten metal transiently. Stirring proceeds. Each holding time and cycle of the normal rotation state and the reverse rotation state can be selectively determined by using the timing determining means 9 depending on the state of the metal material put in each electric furnace.

[0010]

INDUSTRIAL APPLICABILITY According to the present invention, the molten metal contained in the AC electric furnace tank is stirred. Therefore, the molten metal stirrer in the shape of a straight line or a circle is formed near the bottom of the circular electric furnace tank and is located on the lower outside. Is provided and the multi-phase AC voltage applied to the molten metal agitator is periodically switched between the forward rotation state and the reverse rotation state to drive the molten metal, so that sufficient stirring force is applied to the molten metal. There is an effect that the production efficiency can be prevented from being lowered and the productivity can be improved.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention showing a linear (or circular) molten metal stirring device operating in a normal rotation state together with an AC electric furnace.

FIG. 2 shows a structure of the molten metal stirring device shown in FIG.
It is a development view showing a pattern cut along with and developed on a plane together with a power supply means.

FIG. 3 is an explanatory diagram showing a switching timing of a multi-phase AC voltage that alternately realizes a normal rotation state and a reverse rotation state, and a timing determination system.

[Explanation of symbols]

1 ... Electric furnace tank 2 ... Electrode 3 ... Molten metal 4 ... Molten metal stirring device 7 ... Switching means 8 ... Inverter 9: Timing determination means 10 ... Power supply means

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 3K059 AB16 AC66 AD03 CD07 CD13                       CD65                 3K084 AA15                 4K045 AA03 BA01 GB02 RB02                 4K063 AA12 BA02 BA03 CA01 CA03

Claims (2)

[Claims] 1. An AC electric furnace tank having a multi-phase AC electrode for producing molten metal therein, and a linear or circular shape arranged in the lower part of the AC electric furnace tank close to the outside from the outside. An alternating current electric furnace provided with a molten metal stirring device, comprising an electric power supply means for alternately driving the molten metal stirring device in a forward rotation state and a reverse rotation state. . 2. The AC electric furnace according to claim 1, wherein a holding time ratio between the normal rotation state and the reverse rotation state and a switching cycle between the respective states are determined, and the power supply means is cycled. AC electric furnace, characterized in that it is provided with a timing determining means for performing electrical switching.