JPH05280874A - Floating melting device using ceramic-made crucible - Google Patents

Abstract

PURPOSE:To enhance the efficiency of electric power by consisting a crucible which houses a metallic material to be melted with a ceramic material, adopting an induction heating coil which is made of a copper-made hollow pipe whose thermal conductivity is high and connecting the pipe with a supply port and a discharge port of a cooling medium pipeline so as to serve as the function of a cooling device. CONSTITUTION:A ceramic-made crucible 1 is an artificial rotary oval body which comprises a virtually cylinder-shaped peripheral wall 1a and a hollow- shaped bottom wall connected to the wall 1b. A hollow-shaped copper pipe is wound around virtually the whole outer periphery so as to produce an induction heating coil 2. The coil 2 is a copper-made hollow cylinder continuously wound spirally. The lower end is connected to an inlet 4a of cooling water while the upper end is connected to an outlet 4b of cooling water, thereby allowing the cooling water to flow inside the pipe to cool the crucible. This construction makes it possible to prevent an excessive rise in the temperature induced by the heat transmission or the radiation from the material to be melted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention is difficult to form a high-purity metal or alloy because it easily chemically reacts with refractory metals, oxygen (O), nitrogen (N) and the like. The present invention relates to a floating melting apparatus having a structure suitable for melting Ti, W, Mo, Be, Zr, V, Sr, etc., which are generally called reactive metals.

[0002]

2. Description of the Related Art A conventional floating cold wall melting furnace has a shape as shown in FIGS. FIG. 4 is a side sectional view of the crucible, and FIG. 5 is a perspective view showing a part of the crucible with the coil removed. In FIGS. 4 and 5, in the upper part of the copper columnar body 21, a half-body-shaped space is formed by cutting the spheroid parallel to its minor axis, the inner periphery of which is similar to a wine cup. The holes 24 are opened to form a melting chamber. A peripheral wall 21 ′ that defines the hole 24
Are adjacent to each other by a plurality of slits 22 which extend from the upper end to the lower end of the top, extend further below the wine cup-shaped holes, and are opened at predetermined intervals in the circumferential direction. It is configured as a plurality of columnar segments 31 separated from other portions. Further, there is a small-diameter columnar small hole 28 which is continuous with the wine cup-shaped hole 24 and further downward and has a larger diameter than the small hole 28 which is continuous with the small hole 28 and further downward. Sub hole 27
And the slit 22 exists up to the sub-hole 27 as shown in the figure. By the way, the cylindrical body 21 made of copper
Inside each segment 31 of the peripheral wall 21 'of the
A slender inner hole 31a reaching from the bottom portion 23 of the No. 1 to a position slightly lower than the upper end of the segment 31 is opened, and a pipe 31b having an outer diameter smaller than that of the slender inner hole 31a is inserted into the inner hole 31a and the pipe 31b. A double pipe is formed by and, and the inflow and outflow of the cooling water is enabled, and the peripheral wall 21 'of the cylindrical body 21 is cooled. Wine cup-shaped hole 2 mentioned above
4. The existence and shape of the small holes 28 and the sub-holes 27 are largely related to suspending the molten metal melted in the melting chamber formed by the wine cup-shaped holes 24, as described below. ..

As shown in FIG. 6, a coil 34 is wound so as to surround the outer periphery of the columnar body 21, and the coil 34 is connected to a power source (not shown) to allow an alternating current to flow therethrough.
The alternating magnetic flux φ generated by is the copper columnar body 21 in FIG.
Over the upper ends of the peripheral walls 21 'on both the left and right sides, enter the holes 24 as melting chambers, and approach each other inward in the radial direction parallel to the curved surface of the inner periphery of the peripheral wall 21' toward the bottom 23. When the auxiliary holes 27 having a diameter larger than that of the small holes 28 are directed downward in the small holes 28, the alternating magnetic fluxes φ on the left side and the right side of the small holes 28 are directed outward in the radial direction with respect to each other in the auxiliary holes 27. It flows over the lower end of the coil 34, goes up the outer circumference of the coil 34, and circulates. Thus, as shown in FIG. 6, the magnetic path inside the cylindrical body 21 has a concave curved surface shape that approaches horizontal as it approaches the bottom surface of the wine cup-shaped hole 24. The alternating magnetic flux generated by the coil 34 causes the direction of the induced current induced in the metal M to be melted in the opposite direction to the increase / decrease of the current flowing through the coil 34 according to Lorentz's law. The repulsive force is generated by the torque, the bottom of the fixed crucible closes, the inner diameter increases and opens upward, and the upper part of the melting chamber is released and unrestrained. It comes to float away from. Thus, in the floating melting apparatus shown in FIGS. 4 and 5, the coil 3
Even if 4 is not arranged in parallel to the inner peripheral surface of the quadric surface of the hole 24, the alternating magnetic flux φ enters the hole 24 serving as the melting chamber, and the metal to be melted charged in the melting chamber. After the induction current is generated in M and induction heating is performed, the current flows out of the cylindrical body 21 to form a closed magnetic path passing through the outer periphery of the coil 34 and recirculate. The temperature of the induction-heated metal M to be melted gradually rises, and finally it is melted into a molten metal. Since the conventional crucible described above is made of copper, the alternating magnetic flux generated by the coil 34 also passes through the crucible itself and is inductively heated. Therefore, unless the crucible is cooled, the crucible receives induction heating and heat from the metal to be melted. Since a high temperature is reached by transmission and / or radiation, double pipe type cooling water passages 31a and 31b are formed in each segment for cooling as described above.

[0004]

In the conventional floating type cold wall melting furnace, since the crucible body is made of copper, the crucible itself is induction-heated and the temperature thereof needs to be cooled, so that a part of the power supply is required. However, it was vacant for induction heating of the crucible itself and for cooling the temperature rise caused by it, and there was a demand for higher power efficiency due to low power efficiency.

[0005]

In place of the copper crucible, a ceramic crucible such as aluminum nitride (AlN) having low conductivity and good thermal conductivity is adopted, and the conventional copper crucible itself is used. While reducing the loss due to induction heating to improve power efficiency, a metal pipe such as copper with good thermal conductivity is used as a coil for induction heating, and cooling water is circulated inside to cool the cooling pipe. Solved the problem by also serving as the role of.

[0006]

[Function] Since the crucible made of ceramics such as aluminum nitride (AlN) has low conductivity and good thermal conductivity, the induction heating coil does not cause induction heating of the crucible itself, and the thermal conductivity is high. It is good to enclose the outer circumference of the crucible with a metal pipe such as copper, and circulate cooling water in the pipe to prevent excessive temperature rise due to heat conduction or radiation from the melted object stored inside. it can.

[0007]

FIG. 1 is a side sectional view of an induction heating floating melting apparatus which is an embodiment of the present invention. Reference numeral 1 in the drawing indicates an electric conductivity such as aluminum nitride (AlN). A crucible made of ceramics, which is a substance having a low thermal conductivity and a relatively high thermal conductivity. As shown in the drawing, the crucible 1 is a pseudo spheroid composed of a substantially cylindrical peripheral wall 1a and a hollow spherical bottom wall 1b continuous to the lower portion of the peripheral wall 1a. The crucible 1 has a peripheral wall 1a and a bottom wall 1b. A cylindrical peripheral wall 1a and a hollow spherical bottom wall 1 continuous to the lower part of the peripheral wall 1a on almost the entire outer circumference including
A copper pipe is wound around b to form the induction heating coil 2. The crucible 1 and the induction heating coil 2 are housed in the frame 5. The coil 2 is formed by continuously spirally winding a copper hollow cylinder as shown in FIG.
Is connected to the cooling water inlet 4a and the upper end is connected to the cooling water outlet 4b, and cooling water is passed through the inside to cool the crucible. In addition, in order to improve heat conduction between the copper pipe 2 as a coil and the crucible 1, the entire circumference of the crucible or a portion where the copper pipe 2 contacts the crucible 1 as shown in FIG. An intermediate medium 6 having a good thermal conductivity (such as a roller type or a paste type) is sandwiched between the gaps so that they can be sufficiently cooled. Further, it is conceivable to improve the bonding with copper by metallizing the surface of the AlN crucible as one of the bonding methods without using the bonding method as described above.

Next, a melting operation using the floating melting apparatus of the present invention will be described. The coil 2 is connected to the power source P to pass an alternating current. As described in the section of the configuration, since an alternating current is supplied to the coil 2 from the alternating current power source, the alternating magnetic flux φ from the coil 2 passes through the crucible and returns to the coil as shown in FIG. The inner circumference of the bottom wall is a hemispherical surface having an open top, and the coil 2 is also wound along the inner circumference of the bottom wall into a semispherical shape having an open top.
Is given an upward electromagnetic force from the coil 2, that is, a floating direction. When the metal M to be melted is charged in the crucible 1, an induction current is generated in the metal to be melted, and the metal is heated by induction while being given an electromagnetic force in a floating direction. It becomes a molten metal called. Even if the metal to be melted is in a solid state in the initial stage of heating, it may be in a floating state, but in the molten state, the magnetic flux lines are as shown in Fig. 3, and the molten metal is pushed up and becomes a floating state in the crucible. ..
The magnetic flux lines in this floating state are the same as in the case of the copper crucible described as the prior art. In order to achieve this purpose, it is necessary for the coil to be wound in such a form as to generate a magnetic flux sufficient to realize a floating state and to generate an upward force sufficient to push up the molten metal.

Next, this crucible coil has not only the original function of flowing an alternating current, but also the function of a cooling device for cooling the peripheral wall of the crucible by using water as a cooling medium.
When the molten metal is in a completely floating state in the crucible, the molten metal and the inner wall of the crucible do not contact, but it needs to be cooled because it is heated by the radiation from the high temperature molten metal, while the floating state in the crucible of the molten metal is not good. When complete, the molten metal comes into contact with the inner wall of the crucible and is heated by heat transfer from the molten metal, and in this case also, the coil as a cooling device functions effectively. As described above, in order for the coil to function effectively, in order to improve heat transfer between the coil and the outer surface of the AlN crucible, the outer surface of the crucible is metalized and bonded,
Alternatively, since a substance having a high thermal conductivity is placed in the form of a roll, a paste or the like, heat transfer is improved and the surface of the crucible is sufficiently cooled.

[0010]

As compared with the conventional crucible, since the crucible body is made of a material having a low electric conductivity such as ceramic, the crucible itself is not induction-heated, and thus the crucible does not have the conventional copper crucible. In addition, the peripheral wall and the bottom wall are divided by a large number of slits to form a plurality of segments, and holes are provided inside each segment to serve as cooling water passages.
Further, problems in the work such as provision of cooling water supply and drain pipes are alleviated. Further, since melting of the metal to be melted accompanied by floating can be achieved with less electric power, it greatly contributes to the production of the induction melting furnace of this kind and the operation of floating melting.

[Brief description of drawings]

FIG. 1 is a schematic side sectional view showing an example of a suspension melting apparatus according to the present invention.

FIG. 2A is a cross-sectional view of a copper pipe forming a coil, and FIG. 2B is a schematic view showing the joining of the copper pipe forming the coil and the crucible body.

FIG. 3 is a schematic explanatory view showing a relationship between a coil, a magnetic flux generated by the coil, a crucible body and a molten metal inside the coil in an example of the present invention.

FIG. 4 is a side sectional view of a floating melting apparatus according to the prior art.

5 is a perspective view with the coil of the prior art floating melting device shown in FIG. 4 removed.

6 is a schematic explanatory view showing the relationship between the coil of the floating melting apparatus according to the conventional technique shown in FIG. 5, the magnetic flux generated by the coil, the crucible body and the molten metal therein.

[Explanation of symbols]

 1 Crucible of Floating Dissolver 1a Circumferential wall of crucible 1b Bottom wall of crucible 2 Coil 4 Connection cable between coil and power source Cable or bus bar 4a Cooling water supply port 4b Cooling water discharge port 6 Intermediate medium with high thermal conductivity M Molten metal P AC power supply

Claims (5)

[Claims] 1. A hollow-cylindrical peripheral wall which is substantially vertically erected, and a bottom wall which is formed as a part of a hollow sphere or a hollow spheroid continuously to the lower part of the peripheral wall, and whose inside is formed. Is a crucible main body that serves as a melting chamber for accommodating and melting the metal to be melted, and is arranged so as to surround the outer circumference of the crucible main body, connected to an AC power source to generate an alternating magnetic flux, and accommodated inside the crucible main body. Induction heating coil that heats the metal to be melted and causes an upward force to act on the metal to be melted by the interaction of the magnetic field and current, and the crucible body is cooled with water as a cooling medium to raise the temperature of the crucible body. In a floating melting apparatus for a molten metal comprising a cooling device for preventing: a crucible for containing the molten metal is made of ceramics, and the induction heating coil is a hollow tube of copper or the like having a high thermal conductivity. Ah Together, the cooling medium is connected to the supply port of the conduit and the outlet, the cooling that is to serve as also a function suspension smelting apparatus using a ceramic crucible, wherein the device. 2. A floating melting apparatus using a ceramic crucible according to claim 1, wherein the ceramic has a low electrical conductivity and a high thermal conductivity to the extent that it can be substantially regarded as an insulator. 3. A floating melting apparatus using a ceramic crucible according to claim 1, wherein the ceramic is aluminum nitride. 4. The floating using the ceramic crucible according to claim 1, wherein the induction heating coil is joined to the outer periphery of the metallized AlN ceramic crucible. Dissolution equipment. 5. A substance having a high thermal conductivity is sandwiched between the induction heating coil and the outer periphery of the AlN ceramic crucible as an intermediate medium having a roll or a paste shape. A floating melting apparatus using the ceramic crucible according to any one of claims 1 to 3.