KR20100039464A

KR20100039464A - Cold crucible for induction melting

Info

Publication number: KR20100039464A
Application number: KR1020080098432A
Authority: KR
Inventors: 유효열
Original assignee: 주식회사 다원시스
Priority date: 2008-10-08
Filing date: 2008-10-08
Publication date: 2010-04-16

Abstract

The present invention relates to a cooling crucible (Cold Crucible) used in an induction furnace, and more particularly to a crucible for minimizing the loss in the cooling crucible by the induction current by installing an insulator.

According to the present invention, in an induction heating cooling crucible including a plurality of metal segments having a cooling water passage formed therein, the outer circumferential surface of the segment and an inner circumferential surface of the cooling water passage are induced to extend from the cooling water passage to the outer circumferential surface of the segment. There is provided a cooling crucible for induction heating further comprising an installed segmented insulating member. By changing the path of the surface current induced by the segment insulating member, the induced electromotive force is reduced, and the resistance value is increased, thereby reducing the power consumed in the crucible.

The cooling crucible for induction heating according to the present invention has an effect of increasing efficiency by reducing the power consumed in the crucible and increasing the amount of power consumed in the heated object.

Description

Cooling crucible for induction heating {COLD CRUCIBLE FOR INDUCTION MELTING}

Induction dissolving is a method of dissolving alternating current through a coil using Joule's heat caused by the eddy current generated by the electromagnetic induction effect on the metal placed inside the coil. The general induction melting method has been used for the production of metal materials of iron, nickel, copper and aluminum by using refractory materials such as oxide or graphite such as alumina (Al ₂ O ₃ ) and magnesia (MgO) as crucible materials. This dissolution method has a strong stirring effect of the molten metal due to electromagnetic force, and since the atmosphere can be widely used from pressurization to vacuum, the alloy component can be easily adjusted and the vacuum refining effect can be expected. However, in the conventional dissolution method using a refractory crucible, the induction melting method itself has many advantages because the components contained in the crucible react with the molten material to contaminate the molten metal when the active high melting point metal such as the heated object is dissolved. Couldn't be.

The cold crucible melting method is characterized in that it is possible to avoid the problem of melting of the crucible by melting the heated material by converting the crucible into a cooling copper crucible in the conventional induction melting. In the induction melting, the electromagnetic force acts on the molten metal toward the center, so there is little opportunity for the molten metal to come into direct contact with the cooling crucible, and even though the molten metal comes into contact with the copper crucible, the crucible is cooled, so it solidifies immediately. This is because copper crucibles cannot be used. The solidified metal that has adhered to the crucible is dissolved again, and during the melting, the solidification and dissolution are repeated around the crucible.

This melting method is a problem because it consumes a lot of power because it generates the most heat in the vicinity of the cooling crucible, and consumes about 2 to 10 kWH / kg (0.5 to 1.5 kWH / kg in an induction melting method using a common refractory crucible) as a power source unit. It is reported.

In order to solve the above problems of the present invention, the present invention provides a cooling crucible for induction heating which can reduce the loss caused by the current induced in the crucible by providing an insulator on the outer wall of the crucible.

It is preferable that the material of the said segment is copper, and it is preferable that the said cooling means is cooling water which flows inside the side wall. Since the coolant can flow directly into the inner space of the sidewall formed by the metal and the insulator, there is no need to install a separate coolant pipe. In addition, the segment insulating member is preferably epoxy resin or asbestos.

Further, according to the present invention, in the induction heating cooling crucible including a plurality of metal segments having a cooling water passage therein, the length of the circumference of the closed curve formed by the induction current flowing through the segments is greater than the length of the outer periphery of the segments. It is long and the area of the closed curve is provided with a cooling crucible for induction heating, characterized in that smaller than the cross-sectional area of the segment. Since the length of the circumference of the closed curve formed by the induced current is increased, the resistance is increased, and the area of the closed curve is reduced, thereby reducing the size of the induced electromotive force, thereby reducing power consumption.

Hereinafter, with reference to the accompanying drawings will be described a preferred embodiment of the present invention. 1 is a perspective view of one embodiment of a cooling crucible for induction heating according to the present invention. Referring to FIG. 1, the induction heating cooling crucible of the present embodiment includes a sidewall 100 and a bottom surface 200 coupled to the bottom of the sidewall 100, and the sidewall 100 is segmented insulated from the copper plate 124. It consists of sixteen segments 120 consisting of the member 126 and a slit insulating member 140 installed between the segments 120.

The side wall 100 is spaced at regular intervals from the sixteen segments 120 including a copper plate 124 having a thickness of 3 mm and a segment insulating member 126 installed on the open surface. It is configured to include a slit insulating member 140 is provided between the segment 120 is disposed. Splitting crucible sidewall 100 into multiple segments 120 limits the temperature rise due to induction in the crucible wall and facilitates direct induction heating of the material contained within the crucible. In the present embodiment, the segment 120 is described as being arranged to have a rectangular shape, but it is obvious that the segment 120 may be arranged to form a circle. In the present exemplary embodiment, although several independent segments 120 are described as being an assembled cold crucible used to be assembled in accordance with the cross-sectional shape of the ingot, only a part of the longitudinal direction of the cold crucible is divided into several segments 120 by the longitudinal slits. It is also possible to use an integral type that is divided into a) and the remaining part is integrated in the circumferential direction. First, in the case of the assembled cold crucible, it is convenient in the R & D stage before the cross-sectional shape and size of the ingot to be heated is determined. There is a downside to falling.

The thickness of the copper plate 124 should be at least two times the skin depth value, and the penetration depth is determined by the frequency of the current flowing in the coil installed to surround the outside of the crucible. The penetration depth according to the frequency of copper is shown in Table 1.

Frequency (Hz) 50 600 1K 2K 3K 4K 10K 20K 50 K 100 K Penetration depth (mm) 9.47 2.73 2.11 1.49 1.22 1.06 0.67 0.47 0.29 0.21

The segment insulation member 126 serves to reduce power consumed in the crucible by blocking a path of current flowing in the segment 120 by a high frequency current flowing through a coil (not shown) surrounding the outside of the crucible. The reason for the reduced power consumption will be described later in detail. The segment insulating member 126 is not particularly limited as long as the bent copper plate 124 is insulator that can be in close contact even if the bent copper plate 124 shrinks and expands according to temperature change, but epoxy, asbestos or mica is preferably used.

Cooling water flows through the cooling water passage 150 inside the segment 120 formed by the bent copper plate 124 and the segment insulating member 126. The cooling water cools the segment 120 heated by the electromagnetic induction phenomenon so that the heated object inside the crucible melts and solidifies before reacting with the side wall 100, thereby preventing the molten metal from spoiling the copper crucible. In the present embodiment, the coolant passage 150 is composed of one channel, and when the coolant flows from the upper portion of the segment 120, the coolant passage 150 moves along the coolant passage 150 to flow out of the lower portion of the segment 120 and is cooled by heat exchange. After being cooled, it is cooled while being circulated in the manner of being introduced into the upper part of the segment again. In this embodiment, the coolant passage 150 is composed of one channel, but may be composed of two or more channels. In this case, the coolant can be circulated in such a manner that the coolant flows in from the bottom, moves upward through one channel, and then moves downward through the other channel.

The slit insulating member 140 electrically insulates between the segment 120 and the segment 120 and serves to seal the molten metal so that it does not flow outside the crucible. The slit insulating member 140 is not particularly limited, but mica is used in this embodiment.

The bottom surface 200 may include a central outlet (not shown) closed by an openable door. Like the segment 120, the coolant is designed to be circulated.

Hereinafter, a reason for reducing power consumption will be described with reference to the accompanying drawings. It can be seen experimentally that when a current flows in a coil wound outside the crucible, a magnetic field is generated around it. The relationship between the direction of the current and the direction of the magnetic force line can be known by the law of the first screw, and the magnetic force line or magnetic flux of the magnetic field generated by the current must be closed loop and link with the current. Magnetic flux refers to a bundle of lines of magnetic force through a cross section, usually expressed as φ. Assuming that the lines of magnetic force are uniformly distributed, the larger the area S through which the lines of magnetic force pass, the larger the magnetic flux value.

According to Faraday's Law, if the magnetic flux chain professor changes, the electromotive force equal to the rate of change of time is induced. The induced electromotive force can be obtained by [Equation 1]. n means the number of turns of the coil.

Figure 2 is a cross-sectional view of a conventional induction heating cooling crucible, Figure 3 is a cross-sectional view of one embodiment of the induction heating cooling crucible according to the present invention shown in FIG. In one embodiment of the conventional crucible and the cooling crucible for induction heating according to the present invention, the same reference numerals are assigned to members having the same function and structure.

Referring to FIGS. 2 and 3, the object to be heated and the respective segments 110 may be formed by the magnetic field generated by the high frequency current I1 flowing counterclockwise to the coil 300 surrounding the outside of the sidewall of the cooling crucible. Induction currents I2 and I3 flowing in a clockwise direction are generated at 120.

In the conventional induction heating cooling crucible, since an induction current flows along the outer circumference of the segment 110, an area through which a magnetic force line that bridges the induction current passes is equal to the cross-sectional area of the segment. However, in this embodiment, the segmented insulating member 126 is provided in the path through which the induced current flows, so that the path through which the induced current flows is changed as shown in FIG. 3, and thus the area through which the magnetic field lines that bridge the induced current passes. The area occupied by copper in the silver segment 120 is reduced.

Therefore, the magnetic flux value in the segment 120 of the induction heating cooling crucible according to the present embodiment is smaller than the magnetic flux value in the segment 110 of the conventional induction heating cooling crucible. Since the frequency of the current flowing through the coil and the number of turns of the coil are the same, the electromotive force induced in the segment 110 of the conventional induction heating cooling crucible is induced in the segment 120 of the induction heating cooling crucible shown in FIG. 3. Greater than

The current flowing through the crucible can be obtained by [Equation 2]. R represents the resistance value. In the present invention, since the current flowing through the crucible has a high frequency, a skin effect occurs. The skin effect means a phenomenon in which a current flows only near the surface of a conductor when a high frequency current flows through the conductor. This is because induced electromotive force is generated inside the conductor because the direction of the current flowing through the conductor changes rapidly, making it difficult to flow the current in the center of the conductor. The depth through which the current can flow is called the skin depth and is usually expressed as δ. It can be obtained by [Equation 3]. Where f is frequency, sigma is electrical conductivity, and μ is permeability.

The current flowing through the crucible by the skin effect flows along the edges of the segments 110 and 120 as shown in FIGS. 2 and 3. Resistance is inversely proportional to the cross-sectional area through which current flows and is proportional to length. Since the current flows only on the surface by the skin effect, there is no difference in the cross-sectional area in which the current flows in the conventional crucible and the crucible according to the embodiment of the present invention. The cross-sectional area can be seen as the product of the penetration depth and the longitudinal length of the crucible, the penetration depth is determined by the frequency of the current flowing in the coil, because the size of the crucible is the same. As a result, the resistance value changes in proportion to the length L of the current flow path. The resistance value is larger because the length of the path in the embodiment shown in FIG. 3 is longer than the conventional invention shown in FIG. Since the electromotive force induced as described above is smaller in the induction heating cooling crucible segment 120 shown in FIG. 3, the current value is smaller than the value flowing in the segment 110 of the conventional crucible.

The power can be obtained by [Equation 4]. As discussed earlier, both current and electromotive force decrease in value, which reduces the power consumed in the crucible. In addition, the power can also be obtained by Equation 5. As previously discussed V is the area of magnetic force lines to pass through (S) that is proportional to the area of the part made in the crucible of copper and, R is proportional to the length (L) of a path through which current flows, power consumption in the S ² / L Will be proportional.

,

Looking at the embodiment of the cooling crucible for induction heating according to the present invention shown in Figure 3 S value is reduced and L value is increased, the power consumption is reduced.

For example, when the length of the long side of one segment 110, 120 is 30 mm, the length of the short side is 15 mm, and the thickness of the copper plate 124 is 3 mm, the S value in the conventional induction heating cooling crucible. Is 15 x 30 = 450 mm 2, and the L value is (15 x 2 + 30 x 2) = 90 mm. In the embodiment of the cooling crucible for induction heating according to the present invention, the S value is {3 × 30 × 2 + 3 × (15-3 × 2) × 2} = 234 mm 2, and the L value is (15 × 2 + 30). × 2) + {(30-6) × 2 + (15-6) × 2} = 156 mm. Therefore the ratio of power consumption in the embodiment of the induction annealing furnace according to the power consumption in the present invention in a conventional induction heating cooling crucible for the (450 ^2/90) (234 ^2/156) = 2250: 351, resulting in only about 15.6% of the power being consumed.

4 to 10 are cross-sectional views of other embodiments of a segment of a cooling crucible for induction heating according to the present invention. In FIG. 4, the cooling water passage is composed of two channels, and in each channel, a segment insulation member 1126 is provided toward the outer circumferential surface of the segment. In FIG. 5 and FIG. 6, segment insulation is provided on one side or both sides of the side surface. The members 2126 and 3126 were provided. In FIG. 7, the cooling water passage is composed of two channels, and a segment insulation member 4126 is provided on the side of each channel. 8 and 9 are the same as FIGS. 7 and 4 except that the cooling water passage is composed of two cylindrical channels. In FIG. 10, a segmented insulating member 7226 is provided between two cylindrical channels.

That is, if the cross-sectional area of the closed curve due to the induced current decreases and the length of the closed curve becomes long, any type of segment may be used.

An embodiment of the present invention described above and illustrated in the drawings should not be construed as limiting the technical spirit of the present invention. The protection scope of the present invention is limited only by the matters described in the claims, and those skilled in the art can change and change the technical idea of the present invention in various forms. Therefore, such improvements and modifications will fall within the protection scope of the present invention, as will be apparent to those skilled in the art.

1 is a perspective view of one embodiment of a cooling crucible for induction heating according to the present invention.

2 is a cross-sectional view of a conventional cooling crucible for induction heating.

3 is a cross-sectional view of one embodiment of a cooling crucible for induction heating according to the present invention shown in FIG.

4 to 10 are cross-sectional views of other embodiments of a segment of a cooling crucible for induction heating according to the present invention.

100 .... side walls 120 .... segments

124 .... copper plate

140..Slit insulation member 150 .... Coolant passage

200 ... bottom 300 ... coil

Claims

In the cooling crucible for induction heating comprising a plurality of metal segments having a cooling water passage therein,

And a segment insulation member installed to extend from the cooling water passage to the outer peripheral surface of the segment so that an induced current is induced on the outer peripheral surface of the segment and the inner peripheral surface of the cooling water passage.

The method of claim 1,

The material of the said segment is copper, The crucible for induction heating characterized by the above-mentioned.

The method of claim 1,

The cooling means is a cooling crucible for induction heating, characterized in that the cooling water flowing inside the side wall.

The method of claim 1,

The segment insulation member is an induction heating cooling crucible, characterized in that the epoxy resin, asbestos or mica.

The length of the circumference of the closed curve formed by the induced current flowing in the segment is longer than the length of the outer periphery of the segment, the area of the closed curve is smaller than the cross-sectional area of the segment.