JPH0657346A - Method for melting metal and device therefor - Google Patents

Abstract

PURPOSE:To efficiently melt metal in a short period of time and to uniformalize the temp. of the molten metal substantially independent of a stirrer. CONSTITUTION:Iron cores 6a, 6b consisting of magnetic materials are arranged in and out of a molten metal chamber 2. Magnetic fluxes having the iron cores 6a, 6b in and out of the molten metal chamber 2 as their magnetic paths are passed in the molten metal chamber 2 by energizing a winding 7 provided on the iron core 6a existing on the outside of the chamber. As a result, short circuit current flows to the metal 1 in the molten metal chamber 2 and the metal 1 is melted and heated by the Joule heat generated at this time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for melting and maintaining a metal by electromagnetic induction.

[0002]

2. Description of the Related Art Applications of melting and using metals include soldering, brazing, and plating. A large amount of these metals are stored in a bath, which is a metal melting tank, and are heated and melted by a heater arranged in the bath and maintained in a liquid state. FIG. 5 shows a schematic configuration of the melting device. The metal 1 is stored in a solid state in a bath 2 which is a metal melting tank, and is heated by a heater 3 to be melted. The molten metal 1 is stirred by the stirrer 5 in order to maintain a uniform molten state. Reference numeral 4 is an AC power source for supplying electric power to the heater 3.

[0003]

However, the melting of the metal by the heater 3 described above has the following problems.

The heating by the heater 3 is performed only on the metal 1 close to the heater 3, and the metal 1 away from the heater 3 largely depends on heat transfer.
This means that it takes a long time to melt, and it becomes difficult to melt in a short time. In addition, molten metal 1 is heater 3
As the temperature decreases when it is separated from, solidification easily occurs,
Therefore, the temperature of the molten metal depends on the homogenization by the stirring of the stirrer 5. This agitation makes it difficult to maintain the quality of the metal, including oxidization, etc., because it entrains the atmosphere in the molten metal and causes waviness.

The present invention has been made in view of the above circumstances, and a method of melting a metal, which can efficiently melt a metal in a short time, and uniformize the temperature of the molten metal almost without depending on a stirrer. The purpose is to provide the device.

[0006]

In order to achieve the above object, the metal melting method according to the present invention is such that an iron core made of a magnetic material is arranged inside and outside the metal melting tank, and the iron core is located outside the metal melting tank. Characterized in that the metal provided in the metal melting tank is melted and heated by flowing a magnetic flux with the iron core inside and outside of the metal melting tank as a magnetic path to cause a short-circuit current to flow through the metal in the metal melting tank. To do.

The metal melting apparatus according to the present invention includes a metal melting tank, an iron core made of a magnetic material and arranged inside and outside the metal melting tank to form a magnetic path, and outside the metal melting tank. It is characterized by comprising a winding wound around a part of an iron core and an AC power source connected to this winding.
In this case, at least a portion of the iron core arranged in the metal melting tank which is in contact with the metal can be covered with a heat resistant insulator such as quartz.

Further, in the case of a metal melting tank made of a conductive material, a slit along the yoke direction of the iron core is provided at a portion of the floor surface or side surface facing the iron core arranged in the metal melting tank,
The slit may be filled with a heat resistant insulator.

[0009]

When the winding is energized, a magnetic flux flows through the iron core inside and outside the metal melting tank as a magnetic path. Since the metal in the metal melting tank exists around the iron core and constitutes one turn circuit, a large short-circuit current flows through the metal. The temperature of the metal rises due to the Joule heat generated by this current, and when the temperature exceeds the melting point, the metal melts. Since the metal has conductivity even when melted, the short-circuit current continues to flow, and the molten state is maintained stably.

In this case, at least a portion of the iron core in the metal melting tank which is in contact with the metal is covered with a heat resistant insulator such as quartz to thermally and physically cut off the iron core and the metal.
In the iron core arranged in the metal melting tank, the molten metal does not invade the iron core to be thermally damaged, or the molten metal and a part of the iron core do not partially cause a short circuit.

In the case of a metal melting tank made of a conductive material, a slit along the yoke direction of the iron core is provided in a portion of the floor surface or side surface facing the iron core arranged in the metal melting tank. No short circuit is formed on the floor or side of the tank, and the circuit that shorts the iron core is only metal,
The heating efficiency of the metal is improved. Therefore, the metal is melted in a short time, and the temperature can be made uniform without relying on stirring.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention shown in the drawings will be described below. FIG. 1 is a perspective view showing an embodiment of the present invention.
A metal 1 to be melted is stored in a bath 2 which is a metal melting tank. Two U-shaped iron cores 6a each wound with a winding 7 are arranged outside the bottom surface of the bus 2, and the end portions of the iron cores 6a are closely attached to the bottom surface of the bus 2. A U-shaped iron core 6b is also arranged in the bus 2, and the end of each iron core 6b is in close contact with the inner bottom surface of the bus 2. These iron cores 6a and 6b form a closed magnetic circuit via the bottom surface of the bus 2.

In this state, when a current is passed through the winding 7 from the AC power source 4, magnetic flux is induced in the iron cores 6a and 6b. Winding 4
The AC power source 4 to be connected to may be a high frequency power source, but rather, it is better to draw it directly from the power distribution system (50, 60 Hz). The reason is that a dedicated power source is not required, so that the device can be downsized, and if the frequency is high, an unexpected abnormal heating may occur due to the leakage magnetic flux.

The thickness of the floor of the bus 2 such that the magnetic flux passes through the floor of the bus 2 to enter the iron core 6b in the bus 2 and returns to the iron core 6a having the winding 7 through the floor of the bus 2. It flows in a magnetic path having a gap 8 of a length. This magnetic flux causes electromagnetic induction in the metal 1 in the bus 2 and forms a current circuit around the iron core 6b. Since this current circuit is equivalent to a coil short-circuited in one turn, when a magnetic flux acts, a large short-circuit current flows. The magnitude of the short-circuit current I ₂ is the number of turns N times of the windings 7 and the current flowing through the winding 7 When I ₁ and I ₂ = N × I _1.

Joule heat is generated in the metal 1 due to the loss accompanying the flow of the short-circuit current, and the temperature of the metal 1 is increased by the Joule heat. For example, N 1000 times, I
_{When 10 A is applied} as ₁ , the short-circuit current I ₂ is 10,000 A, and the loss is proportional to the square of the current, so that the temperature can be efficiently raised in a short time. When the temperature exceeds the melting point of metal 1, metal 1 begins to melt. Since the resistivity of the metal 1 increases as the temperature rises, the short-circuit current selectively flows in a place where the resistance is small. That is, since it concentrates on the unmelted portion, heat generation in that portion becomes large and the temperature is rapidly raised. As a result, the metal 1 is uniformly heated and melted.

Further, since the metal 1 has conductivity even when melted, a short circuit current continues to flow. Moreover, when the metal 1 is melted, the short-circuit current flows concentratedly in the partially cooled and solidified portion, so that the temperature of the metal 1 is kept uniform as a result of melting and rising again.

FIG. 2 shows another embodiment of the present invention in which the structure of the iron core is changed, and the operation is the same as the embodiment of FIG. In this embodiment, the iron cores 16 and 16 are arranged in the bus 2 only in the vertical direction so as to sandwich one floor surface of the bus 2 therebetween. By arranging the iron cores 16 and 16 in the bus 2 only in the vertical direction,
The internal magnetic flux only needs to pass through the floor of the bus 2 once, and the electrical coupling between the winding 7 and the metal 1 can be improved.

FIG. 3 shows an embodiment according to claim 3.
A heat-resistant insulating layer 8 made of quartz or the like is provided on the outermost layer by coating or the like only on the entire iron core 6b arranged in the bus 2 or only on the portion of the iron core 16 in contact with the metal. In the embodiment, the case of the iron core 6b is shown. If the molten metal 1 is, for example, a laminated body of a silicon steel sheet having an iron core, the interlayer insulation is thermally deteriorated, or a short circuit is locally formed with a part of the laminated body to cause a short circuit current to flow into the iron core. As a result, the reliability of the device may be reduced, or the heating efficiency may be deteriorated. Therefore, as described above, the heat-resistant insulating layer 8 is provided as the outermost layer only on the portion of the iron core 6b or the iron core 16 that is in contact with the metal.
The above problems can be solved by thermally or physically cutting off b or 16 and the metal 1.

FIG. 4 shows an embodiment according to claim 4.
When the bus 2 is made of a conductive material such as stainless steel,
A slit 9 is formed on the floor surface of the bus 2 facing the iron core 6b along the longitudinal direction of the yoke portion of the iron core 6b. The slit 9 has a wide width at a portion where the end of the iron core 6b contacts the floor surface, and has a narrow width at a portion along the yoke portion. The slit 9 is filled with a heat-resistant insulating material 10 to prevent molten metal from leaking.

With this configuration, it is possible to prevent the short circuit due to the magnetic flux from being formed on the floor surface by the slit 9, and it is possible to suppress the consumption of the short circuit current at that portion. As a result, a short circuit can be formed with only the metal 1 and the heating efficiency can be improved.

[0021]

As described above, according to the metal melting method and apparatus of the present invention, efficient heating can be performed and the metal can be melted in a short time. Further, the temperature of the molten metal can be made uniform and maintained without relying on an agitator, and the quality maintenance of the molten metal can be performed relatively easily. In particular, by covering the iron core in the metal melting tank with a heat-resistant insulating layer, the iron core and the metal can be thermally cut off, and the reliability of the apparatus can be improved. Further, by providing slits on the floor surface or the side surface facing the iron core in the metal melting tank along the yoke direction, it is possible to suppress the consumption of the short-circuit current at that portion and improve the heating efficiency.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of the present invention.

FIG. 2 is a perspective view showing another embodiment of the present invention.

FIG. 3 is a perspective view of an essential part showing another embodiment of the present invention corresponding to claim 3;

FIG. 4 is a perspective view of an essential part showing another embodiment of the present invention corresponding to claim 4;

FIG. 5 is a schematic configuration diagram showing a conventional example.

[Explanation of symbols]

1 is a molten metal, 2 is a bath (metal melting tank), 6a,
6b and 16 are iron cores, 4 is an AC power supply, 7 is a winding wire, 8 and 10
Indicates a heat resistant insulator, and 9 indicates a slit.

Claims (4)

[Claims] 1. An iron core made of a magnetic material is arranged inside and outside a metal melting tank, and a winding provided on an iron core located outside the metal melting tank is energized to use the iron core inside and outside the metal melting tank as a magnetic path. A method for melting a metal, wherein the metal is melted and heated by flowing a magnetic flux to cause a short-circuit current to flow through the metal in the metal melting tank. 2. A metal melting tank, an iron core made of a magnetic material and arranged inside and outside the metal melting tank to form a magnetic path, and a part of an iron core arranged outside the metal melting tank. A metal melting device consisting of a winding and an AC power source connected to the winding. 3. The metal melting apparatus according to claim 2, wherein at least a portion of the iron core arranged in the metal melting tank, which is in contact with the metal, is covered with a heat resistant insulator such as quartz. 4. A slit along the yoke direction of the iron core is provided in a portion of the floor or side surface of the metal melting bath made of a conductive material, the portion facing the iron core arranged in the metal melting bath. The metal melting apparatus according to claim 2, wherein the apparatus is filled with an insulating material.