JPH0443192B2 - - Google Patents

Description

[Detailed description of the invention] [Technical field to which the invention pertains] Various gases such as oxygen gas, hydrogen gas, and nitrogen gas are contained in the molten metal in which the metal is melted. This may cause defects in the casting. In a vacuum induction furnace, the gas in the molten metal is discharged into a vacuum for degassing treatment.

The present invention relates to a crucible-type vacuum induction furnace that can improve heat retention efficiency without inhibiting the degassing effect of molten metal within the furnace body.

[Prior art and its problems]

In a crucible-type vacuum induction furnace, an induction heating coil is wrapped around the outer periphery of a furnace body made of refractory material and equipped with a sealed furnace lid on top, with a heat-resistant insulator interposed therebetween. It is designed to be heated to high temperature and melted by electromagnetic induction. The metal is first put into the furnace in the form of an ingot, then after the inside of the furnace is evacuated and an alternating current voltage is applied to the coil, the metal is heated and melted by the heat generated by the eddy current generated by the action of the magnetomotive force of the coil. This molten metal is stored or tapped while being kept warm. The gas in the molten metal is released into a vacuum from the surface of the molten metal by electromagnetic stirring during melting and heat retention, and is degassed.

This structure has the disadvantage that it is uneconomical because almost the same amount of power is used during heat retention as during melting.

[Purpose of the invention]

In order to eliminate the above-mentioned drawbacks, the present invention aims to provide a crucible-type vacuum induction furnace that can improve heat retention efficiency without inhibiting the degassing effect of molten metal in the furnace body. .

[Key points of the invention]

In order to achieve the above-mentioned object, the present invention has an induction heating coil wrapped around the outer periphery of a crucible-shaped furnace body divided into upper and lower halves, so that the power supply to the lower coil can be easily cut off when the molten metal in the furnace body is kept warm. It was designed to do so.

[Embodiments of the invention]

FIG. 1 shows an embodiment of the invention.
This figure shows the state during heat retention. The induction heating coils 3 and 4 are divided into upper and lower halves on the outer periphery of a crucible-shaped furnace body 2 made of refractory material and equipped with a closed furnace lid 1 on the top.
A coil 3,
The molten metal 5 heated to high temperature and melted by the electromagnetic induction action of 4 is stored while being kept warm. Said coil 3
and 4 are connected in parallel to a common power source 6, and the lower coil 4 is provided with a shearing device 7 for cutting off the power source 6 when the molten metal 5 is kept warm. In the induction furnace, both the upper coil 3 and the lower coil 4 are energized when melting metal, and the upper coil 3 is energized when the molten metal 5 is kept warm.
Only energization is applied.

According to the embodiment described above, the power source 6 of the lower coil 4 is cut off when keeping the molten metal 5 warm, so that the input power can be reduced and the heat can be kept efficiently.On the other hand, the upper coil 3 is energized, so its electromagnetic The gas in the molten metal 5 can be released into a vacuum by the stirring action by force, and degassing treatment can be performed.

In FIG. 2 showing another embodiment, the coil 3
and 4 are power supplies 16 and 1 with different frequencies, respectively.
7, and the power source 17 for the lower coil 4 has a higher frequency than the power source 16 for the upper coil 3.
When using this frequency of 50Hz or 60Hz, a commercial power supply is used, and when using other frequencies, the commercial frequency is generally converted by an inverter. Since the magnetic permeability and resistivity of the metal ingot and the molten metal 5 charged into the furnace body 2 are different, the penetration depth of the eddy current generated in the ingot and the molten metal 5 is also different, and since the ingot has a shallower penetration depth, the absorbed power is also different. few. Therefore, it takes a long time to melt the ingot, and in order to shorten the time required for melting, it is necessary to apply a voltage with a high frequency.

According to this embodiment, when melting metal ingots, a voltage with a higher frequency than the upper coil 3 is applied to the lower coil 4 to increase the input power, so that the ingots in the lower part of the furnace body 2 are efficiently and rapidly melted, and the molten metal is melted. 5 becomes more than half of the inside of the furnace body 2, the upper coil 3 effectively performs melting, stirring, and degassing operations. Therefore, the overall time required for dissolution can be shortened and dissolution efficiency can be improved.

In the above embodiment, the case where the coils 3 and 4 are divided into two upper and lower parts has been described, but the present invention can also be applied to a structure in which the coils are divided into three or more parts.

〔Effect of the invention〕

According to this invention, in a crucible-type vacuum induction furnace, the induction heating coil wrapped around the outer periphery of the furnace body is divided into upper and lower parts, and the power to the lower coil is cut off when the molten metal in the furnace body is kept warm. As a result, it is possible to reduce the power input during heat retention and improve the heat retention efficiency without inhibiting the degassing effect of the molten metal.

[Brief explanation of drawings]

Figure 1 is a schematic configuration diagram of an embodiment of this invention;
The figure is a schematic diagram of another embodiment of the present invention. 2... Furnace body, 3, 4... Coil, 5... Molten metal,
6, 16, 17...Power supply, 7...Shrinking device.

Claims (1)

[Claims] 1. In an induction furnace in which metal in the furnace body is heated and melted in a vacuum by the electromagnetic induction action of an induction heating coil wound around the outer periphery of a crucible-shaped furnace body, the coil is divided into upper and lower halves. , a crucible-shaped vacuum induction furnace characterized in that a lower coil is provided with a cut-off device for cutting off the power when the molten metal in the furnace body is kept warm. 2. The crucible-type vacuum induction furnace according to claim 1, wherein the lower coil is connected to a power source with a higher frequency than the upper coil.