JP3272020B2 - Method and apparatus for levitation heating of metal lump - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for levitation and heating of a metal lump in the air, and more particularly to a method and apparatus suitable for precision casting of titanium or titanium alloy having extremely high temperature activity. Things.

[0002]

2. Description of the Related Art In heating (melting) a metal lump, particularly a metal lump such as titanium having a high temperature activity, to a high temperature, high-frequency induction is carried out in a floating state in the air so that a reaction does not occur due to contact with other members. Heating is most ideal. Therefore, the present applicant has previously proposed the levitation heating device 1 shown in FIGS. 9 and 10.

When heating a metal lump using the present apparatus 1, a metal lump 2 to be heated is divided into a plurality of metal cylinders 4 having a plurality of slits 3 of equal width formed at equal intervals. A high-frequency current is supplied from a high-frequency power supply 6 to a helical high-frequency induction heating coil 5 that is arranged in the hollow portion and surrounds the outer periphery of the cylindrical body 4, so that the electromagnetic force upwardly acting on the metal lump 2. To perform high-frequency induction heating under a levitating condition.
When performing precision casting, the metal lump 2 is heated and melted and cast into a mold.

Here, the mechanism of heating and melting the metal lump 2 will be described as follows. That is, when a high-frequency current (Jo) flows through the high-frequency induction heating coil 5, a magnetic flux (Φ) generated by the high-frequency current (Jo) acts on the metal lump 2 through the slit 3 of the cylindrical body 4, An induced current (Je) flows (see FIGS. 9 and 11). Thereby, the metal lump 2 is heated by Joule heating. At this time, the metal lump 2
The electromagnetic force (F) is generated in the metal lump 2 by the interaction between the induced current (Je) flowing on the surface of the metal body and the magnetic flux (Φ), and the direction of the electromagnetic force (F) is determined by Fleming's left-hand rule.
Is more upward (obliquely upward) than the direction toward the axis. That is, the induced current (Je) is a direction along the circumferential direction of the cylindrical body 4, and the direction of the magnetic flux (Φ) at the upper end side position of the cylindrical body 4 where the metal lump 2 is placed is indicated by an arrow H in FIG. This is because it can be bent like this. Therefore, the upward component force (Fu) acts on the metal block 2 as a levitation force,
As a result, the metal lump 2 is held in a state of being levitated in the air in the vicinity of the upper end portion in the cylindrical body 4 and is subjected to high-frequency induction heating. The magnitude of the electromagnetic force (F) depends on the induced current (J
This value is proportional to the product of e) and the magnetic flux density (B).

[0005]

In the levitation heating apparatus 1 having such a configuration, the magnetic flux generated from the high-frequency induction heating coil 5 is not uniform in the winding direction (circumferential direction), and the magnetic flux of each part is not uniform. Densities are different. In particular,
Since the currents flowing through the leads 5a and 5b of the coil 5 are in opposite directions, the magnetic flux density near these leads 5a and 5b is relatively small, and the magnetic flux near the coil body portion 5c facing the leads 5a and 5b. Density is relatively large.
Also, since the coil 5 is spirally wound, its uppermost winding portion is inclined with respect to the horizontal plane. Therefore, the induced current (eddy current) flowing in the surface portion of the metal block 2 adjacent to the uppermost side of the winding portion and the magnetic flux density acting on the surface portion are changed by the surface opposite to the surface portion (the winding portion). (The surface portion of the metal block 2 corresponding to the lowermost portion of the metal lump 2), and the electromagnetic force generated on the surface portion becomes larger than that on the opposite surface portion.

As described above, since the electromagnetic force acting on each surface of the metal lump 2 from the high-frequency induction heating coil 5 is different, the metal lump 2 rotates at a high speed around the horizontal axis in a certain direction. While being (rotated), high-frequency induction heating is performed uniformly.

However, when the metal lump 2 is rotated, when the metal lump 2 is heated and melted, the molten metal may be scattered around by the centrifugal force caused by the rotation. If such a situation occurs, not only will the material (the metal lump 2) be lost, but also a great danger will be involved in the melting operation.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to impart uniform heating by rotating a metal lump until the metal lump reaches a melting temperature. An object of the present invention is to provide a levitation heating method and a device capable of stopping the rotation of a metal block immediately before reaching.

[0009]

In order to achieve the above-mentioned object, in the air levitation heating method of the present invention, the outer periphery of a metal cylinder having a plurality of slits extending radially in a radial direction is formed. While surrounding the cylindrical body and the axis of the high-frequency induction heating coil in a vertical direction while supplying a high-frequency current to the high-frequency induction heating coil, the inside of the hollow portion of the cylindrical body is surrounded by the high-frequency induction heating coil coaxially. In the method of applying an electromagnetic force directed upward to the metal lump in the high-frequency induction heating while levitating the metal lump in the air, using a metal cylindrical body having a different occupation ratio of the slit in the circumferential direction, By adjusting the relative rotation position of the cylindrical body with respect to the high-frequency induction heating coil, a state of levitation heating while rotating the metal mass. Rolling is stopped so that switch selectively to the state of airborne heat.

In the levitation heating apparatus of the present invention,
(A) a metal cylindrical body having a plurality of slits extending radially in a radial direction, wherein the occupation ratio of the slit portion in the circumferential direction is varied along the circumferential direction; A high-frequency induction heating coil disposed coaxially around the outer periphery of the cylindrical body and having an axis disposed along a vertical direction, and (c) a high-frequency induction coil for supplying a high-frequency current to the high-frequency induction heating coil A power supply; and (d) a rotation driving unit that drives the cylindrical body to rotate with respect to the high-frequency induction heating coil about an axis. By adjusting, the metal lump in the hollow portion of the cylindrical body is selectively rotated or stopped to heat the air in the air.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 shows a levitation heating apparatus 10 for carrying out the levitation heating method according to the present invention. The apparatus 10 includes a copper cylindrical body 11 that accommodates a metal lump 9 to be heated in an internal space (hollow portion), and a spiral high-frequency induction heating coil 12 that is disposed so as to surround the outer periphery of the cylindrical body 11. And a high-frequency power supply 13 for supplying a high-frequency current (electric power) to the coil 12.

As shown in FIG. 2, the cylindrical body 11 is
It has a plurality of slits 16 extending radially in the radial direction, and the slits 16 in the circumferential direction of the cylindrical body 11 are provided.
The occupation ratio (arrangement ratio) of the portion is made different along the circumferential direction. That is, in the present example, the plurality of slits 16 are formed at equal angular intervals, and the width L _{1 of the} slit 16a formed in one half portion 11a of the cylindrical body 11 and the other of the cylindrical body 11 Half part 11b
And the width L ₂ of the slit 16b are made different from each other to be formed in (L _1> L _2).

Each segment 1 between the slits 16
7 are connected to each other at the lower end of the cylindrical body 11. Further, the cooling water passage 1 is provided inside each segment 17.
The cooling water passage 18 has one end connected to a water guide pipe 19 and the other end connected to a drain pipe 20.

On the other hand, the high-frequency induction heating coil 12 is formed by spirally winding a copper pipe. Cooling water is supplied to the hollow portion, and the lead portions 12a, 12b are provided.
A high-frequency current is supplied from the high-frequency power supply 13 via the. And this coil 12 is a cylindrical body 11
Are arranged so as to coaxially surround the outer periphery of the coil 12, and the axes of the coil 12 and the cylindrical body 11 are aligned in the vertical direction.

Although not shown, the cylindrical body 11
Is rotated about its axis, whereby the slits 16a, 16a,
A rotation drive mechanism for adjusting the relative position of 16b is provided.

One specific example of the present apparatus 10 is as follows. (1) Material of ingot: steel (S-45C) (2) Shape: spherical, diameter 43mmφ weight, 300g (5) Distance from top of coil to top of cylindrical body: 15m
m (6) High frequency heating condition (a) Preheating condition (non-floating state) (a) Frequency: 10 KHz (b) Output: 10 kW (c) Heating time: 8 seconds (b) Levitation heating condition (a) Frequency: 10 KHz (B) Output: 28 kW

Next, the operation and action when the metal lump 9 is levitated and heated using the present apparatus 10 will be described.

First, the metal lump 9 to be heated is placed on a mounting table (not shown), and the metal lump 9 is placed under the cylindrical body 11 from below the cylindrical body 11.
1 and is placed at a levitation heating start position corresponding to the uppermost end of the high frequency induction heating coil 12. Thereafter, a high-frequency current is supplied from the high-frequency power supply 13 to the coil 12, and the metal block 9 is levitated by the vertical component force of the electromagnetic force generated thereby. On the other hand, by simultaneously operating a transfer mechanism (not shown), the mounting table for the metal block 9 is moved below the cylindrical body 11 and moved to a position outside the position immediately below the cylindrical body 11.

Then, by adjusting the high-frequency current supplied to the high-frequency induction heating coil 12, the horizontal axis of the metal lump 9 is disposed above the upper end surface 11c of the cylinder 11, and a part of the metal lump 9 is The metal lump 9 is levitated in the air at a position where the metal lump 9 is arranged in the hollow portion 11 and high-frequency induction heating is performed at this position.

At this time, as shown in FIG. 1, the half portion 11b of the cylindrical body 11 provided with the narrow slit 16b is opposed to the lead portions 12a and 12b of the high-frequency induction heating coil 12, and the wide slit 16a is formed. The cylindrical body 1 is provided such that the half portion 11a of the cylindrical body 11 provided with the coil body faces the coil body portion 12c corresponding to the lead portions 12a and 12b.
1 is arranged. With this configuration, a relatively large electromagnetic force acts obliquely upward on the surface of the metal block 9 that faces the coil body portion 12c more than the surface that faces the lead portions 12a and 12b. Is heated at a high speed in the direction of arrow A in FIG.

When the arrangement of the cylindrical body 11 with respect to the high-frequency induction heating coil 12 is set to a state completely opposite to the state shown in FIGS. 1 and 2, that is, a state changed by 180 ° as shown in FIGS. Has slits 16a and 16
According to the selection condition of the width b, the rotating direction of the metal block 9 is the direction of the arrow B opposite to the direction of the arrow A as shown in FIG.

In this state, immediately before the metal lump 9 is heated evenly in a rotating state and the metal lump 9 reaches the melting temperature, a rotation drive mechanism (not shown) is operated to move the cylindrical body 11 about the axis thereof, for example. Approximately 90 ° (this rotation angle is determined by slits 16a,
16b, the arrangement interval, the inclination angle of the high-frequency induction heating coil 12 with respect to the cylindrical body 11, and the lead portions 12a, 1b.
It changes depending on conditions such as the arrangement of 2b. ) Only rotate.
Thereby, as shown in FIG. 5, the wide slit 16a of the cylindrical body 11 is arranged corresponding to the portion 12d between the lead portion 12a and the coil body portion 12c, and the narrow slit 16b of the cylindrical body is formed in the portion 12d. Is arranged corresponding to the facing portion 12e. With such an arrangement relationship, the magnitude of the electromagnetic force acting on the surface of the metal lump 9 becomes equal, and the force acting in the rotation direction is canceled, so that the rotation of the metal lump 9 is stopped.

Under this condition, the high-frequency induction heating is continued to heat the metal lump 9 to a temperature higher than the melting temperature to bring it into a molten metal state. Along with this, the molten metal 9 'becomes completely spherical due to its surface tension (see FIG. 6).

Next, the supply of the high-frequency current to the high-frequency induction heating coil 12 is cut off. With this, the electromagnetic force (levitation force) acting on the molten metal 9 'disappears, so that the molten metal 9' falls naturally and is cast into a mold (not shown). Then, the molten metal 9 'cast into the mold is naturally cooled, and a precision cast product having a predetermined shape is obtained.

According to the above-described apparatus 10, since the metal lump 9 is heated in a solid state and is subjected to high-frequency induction heating until just before it reaches the melting temperature, the metal lump 9 can be uniformly heated as a whole. Immediately before melting, the rotation of the metal block 9 is stopped by adjusting the relative rotation position of the cylindrical body 11 with respect to the high-frequency induction heating coil 12, so that the molten metal 9 'scatters around. Occurrence can be prevented. The rotation speed of the metal block 9 during heating can be arbitrarily adjusted by adjusting the rotation position of the cylindrical body 11.

The embodiment of the present invention has been described above.
The present invention is not limited to the embodiments described above, and various modifications and changes can be made based on the technical idea of the present invention.

For example, a plurality of slits 16 of the cylindrical body 11
Can be variously changed. That is, as shown in FIG. 7, the width of each slit 16 is all the same, the intervals of the slits 16 in the circumferential direction of the cylindrical body 11 are made different, and the arrangement ratio of the slits (to the entire circumference of the cylindrical body 11 The ratio occupied by the slit 16 may be changed along the circumferential direction. Further, as shown in FIG. 8, slits 16 whose width changes gradually may be arranged at equal angular intervals.

[0029]

As described above, the method and the apparatus according to the present invention are arranged such that the metal cylinders having different occupying ratios of the slits in the circumferential direction are rotated and arranged at predetermined positions.
Since the high-frequency induction heating is performed by selectively switching the metal mass floating in the air to the rotation or rotation stop state, uniform heating can be performed under the rotation state, and immediately before melting. By stopping the rotation, the scattering of the molten metal can be prevented. Therefore, according to the present invention, it is possible to heat (melt) a metal lump to a uniform temperature in a simple device without contact with other members while ensuring the safety of operation, and to obtain a high quality cast product. Etc. can be obtained.

[Brief description of the drawings]

FIG. 1 is a plan view of a levitation heating device according to the present invention.

FIG. 2 is a sectional view of the device shown in FIG.

FIG. 3 is a plan view of the levitation heating device showing a state where the cylindrical body is arranged at a position rotated by 180 ° from the position shown in FIG. 1;

FIG. 4 is a sectional view of the apparatus shown in FIG. 3;

FIG. 5 is a plan view of the levitation heating device showing a state where the cylindrical body is arranged at a position rotated by approximately 90 ° from the position shown in FIG. 1;

6 is a sectional view of the device shown in FIG.

FIG. 7 is a plan view showing a modification of a slit provided in a cylindrical body.

FIG. 8 is a plan view showing another modification of the slit provided in the cylindrical body.

FIG. 9 is a cross-sectional view of a levitation heating device including a cylindrical body in which slits having the same width are provided at equal intervals.

FIG. 10 is a plan view of the device shown in FIG. 9;

FIG. 11 is a cross-sectional view showing a part of the above-mentioned cylindrical body, which is cut away.

[Explanation of symbols]

9 metal block 10 slits L ₁ levitation heating device 11 the cylindrical body 12 of the wide high-frequency induction heating coil 16 slits 16a slit 16b narrow, L ₂ slit width

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) C22B 9 / 16,9 / 22 F27B 14/06-14/14 F27D 11/00-11/06

Claims (5)

(57) [Claims] 1. A high-frequency induction heating coil coaxially surrounds the outer periphery of a metal cylinder having a plurality of slits extending radially in a radial direction, and the axis of the cylinder and the high-frequency induction heating coil. Are arranged along the vertical direction, and a high-frequency current is supplied to the high-frequency induction heating coil to cause an upward electromagnetic force to act on the metal lump in the hollow portion of the cylindrical body. In the method in which induction heating is performed, by using a metal cylinder having different occupation ratios of the slits in the circumferential direction, by adjusting a relative rotation position of the cylinder with respect to the high-frequency induction heating coil, the metal is formed. Selective switching between the state of levitation heating while rotating the mass and the state of levitation heating with rotation stopped Levitating heating method for metal lump. 2. Until immediately before the melting temperature of the metal lump, the metal lump is levitated and heated in the air under a rotating state, and immediately before the melting temperature is reached, the metal lump is brought into a rotation stop state. The method of claim 1, wherein the melting is performed by levitation heating under the condition. 3. A metal cylinder having a plurality of slits extending radially in a radial direction, wherein the occupation ratio of the slit portion in the circumferential direction is varied along the circumferential direction. (B) a high-frequency induction heating coil disposed coaxially around the outer periphery of the cylindrical body and having an axis arranged along a vertical direction; and (c) a high-frequency induction heating coil. A high-frequency power supply for supplying an electric current; and (d) a rotary drive unit for rotating the cylindrical body with respect to the high-frequency induction heating coil about an axis. By adjusting the relative rotation position, the metal lump in the hollow portion of the cylindrical body is selectively rotated or stopped to be heated in the air by heating in the air. Levitation heating device. 4. The metal lump according to claim 3, wherein the widths of the plurality of slits are all the same, and the arrangement intervals of the plurality of slits in the circumferential direction are partially different. Levitation heating method. 5. The aerial of a metal block according to claim 3, wherein the plurality of slits are arranged at equal intervals in a circumferential direction, and the widths of the plurality of slits are partially varied. Levitation heating method.