JP2013100981A - Tapping electromagnetic nozzle device of cold crucible melting furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tapping electromagnetic nozzle device which can stably tap the hot metal of molten metal, in a cold crucible melting furnace.SOLUTION: The tapping electromagnetic nozzle device 18 composed of a tapping nozzle 20 and a nozzle coil 22 at the outside of the nozzle is arranged at a pot bottom 16 of the cold crucible melting furnace 10. The tapping electromagnetic nozzle device 18 is arranged outside the tapping nozzle 20 in advance in a positional relationship in which the lower end of the nozzle coil 22 is located at an upper position not lower than the lower end of the tapping nozzle 20 by D with the D set as a tapping port diameter of the tapping nozzle 20, and the density of magnetic flux at the lower end of the tapping nozzle 20 generated by high-frequency induction heating by the nozzle coil 22 at the tapping of the hot metal is set not higher than 50 mT in advance.

Description

  The present invention relates to an electromagnetic nozzle device for hot water of a cold crucible melting furnace in which a raw metal is melted in a semi-floating state by high-frequency induction heating using a melting coil in a water-cooled crucible.

Conventionally, a cold crucible melting furnace has been used as a melting furnace for metals having a high melting point such as titanium.
Here, a cold crucible melting furnace conventionally used is a cylindrical water-cooled crucible (copper crucible) obtained by connecting arc-shaped water-cooled copper segments divided into a plurality of portions in the circumferential direction to each other in the circumferential direction through an insulating material. In this configuration, a melting coil is arranged on the outer side, and the raw metal charged in the crucible is melted by high-frequency induction heating using the melting coil.

At this time, the metal melted in the crucible is separated from the peripheral wall of the crucible by the action of electromagnetic force by the melting coil, that is, magnetic repulsive force (Lorentz repulsive force), and the dome-shaped semi-floating with the center rising upward (Thus, this cold crucible melting furnace is also called a levitation melting furnace).
This melting technique using a cold crucible melting furnace is still a developing technique, and at present, a method is generally used in which a metal melted in a crucible is tilted together with a copper crucible and a melting coil and discharged.

However, this hot water method has various problems in addition to the hot water yield.
Therefore, various methods have been studied in which a hot water discharge nozzle 200 is provided at the bottom of the crucible as shown in FIG. 7 and the molten metal in the crucible is discharged from the bottom of the crucible to the outside downward through the hot water nozzle 200.

However, this hot water method also has a difficult problem.
In melting using a cold crucible melting furnace, the portion of the molten metal inside the crucible that contacts the bottom of the crucible becomes solidified metal (skull) due to cooling by the bottom of the crucible, and the nozzle for hot water is blocked by the solidified skull during melting of the metal. It is in the state.

  In order to discharge the molten metal inside the crucible from the hot water nozzle 200 from this state, in the conventional hot water nozzle device (electromagnetic nozzle device), the hot water nozzle 200 is connected to the upper funnel portion 200-1 having an inverted truncated cone shape. The funnel part 200-1 is followed by a lower straight part 200-2 that hangs downward, and a solidified skull that is solidified by the funnel part 200-1 and closes the hot water discharge nozzle 200, Melting is performed by high-frequency induction heating by a nozzle coil 202 disposed outside the hot water nozzle 200, the hot water nozzle 200 is opened, and the molten metal inside the crucible is discharged downward through the hot water nozzle 200.

  However, in the conventional electromagnetic nozzle device for hot water, the hot water nozzle 200 itself is also composed of water-cooled copper having a divided structure, and therefore, the molten metal is cooled by touching the hot water nozzle 200 during the hot water, The solidified skull k adheres to and grows at the position where the nozzle 200 exits, that is, below the lower end of the hot water nozzle 200, and this causes disturbance in the hot water flow from the hot water nozzle 200, thereby obtaining a stable hot water. There was a problem that it was not possible.

  Thus, when such a tapping flow turbulence occurs, the molten metal flowing out from the tapping nozzle 200 is scattered, and in some cases, it does not enter the inside of the mold installed below. Also, the solidified skull k generated at the lower end of the hot water discharge nozzle 200 may eventually grow, causing the hot water discharge nozzle 200 to be blocked.

If such a problem occurs in the hot water, the hot water cannot be continued, the hot water flow is disturbed as described above, and the hot water must be stopped.
Because of these problems, the current situation is that melting using a large-capacity cold crucible melting furnace has not yet been put to practical use.
Although several electromagnetic nozzle devices for hot water have been proposed for the purpose of solving the problem of adhesion of the solidified skull to the hot water nozzle 200 (for example, Patent Document 1 and Patent Document 2 below), they are still sufficient. The above problem has not been solved.
As another prior art, there is one described in Patent Document 3 below.

JP 2001-183067 A JP 2006-153362 A JP 2005-140491 A

  The present invention has been made for the purpose of providing an electromagnetic nozzle device for hot water discharge that can stably discharge molten metal melt in a cold crucible melting furnace.

  Thus, in the electromagnetic nozzle device for hot water of claim 1, the raw material metal charged in the inside of the water-cooled crucible is induction-melted at a high frequency by a melting coil provided outside the crucible, and the raw metal is contained in the crucible. In addition to providing a hot water discharge nozzle at the bottom of the crucible of the cold crucible melting furnace that melts in a semi-floating state, a nozzle coil is provided outside the hot water discharge nozzle, and solidified at the bottom of the crucible by the nozzle coil. In the electromagnetic nozzle device for hot water of a cold crucible melting furnace in which the solidified metal is melted by induction induction to discharge the molten metal in the crucible, the diameter of the hot water nozzle is D, and the nozzle coil is used for the hot water. The nozzle coil is disposed outside the hot water nozzle so that the lower end of the nozzle coil is higher than the lower end of the hot water nozzle by D or more. The magnetic flux density at the lower end mouth of the hot water nozzle generated by high frequency induction heating by the nozzle coil when the molten metal is discharged is 50 mT or less, and the molten metal discharged from the lower end mouth of the hot water nozzle On the other hand, the outward tensile force due to the magnetic field formed by the nozzle coil is suppressed.

Effects and effects of the invention

As described above, according to the first aspect of the present invention, the nozzle coil is arranged outside the hot water nozzle in such a positional relationship that the lower end of the nozzle coil is located above the lower end of the hot water nozzle by an amount equal to or larger than the hot water outlet diameter D.
The present inventors have found that the phenomenon that the solidified skull adheres and grows at the lower end of the hot water nozzle, and the flow of the molten metal is throttled there when the molten metal in the crucible passes through the hot water nozzle. It was thought that when the pressure was released and the pressure was released, the molten metal flow spread and a part of the molten metal solidified and adhered to the lower end of the nozzle for molten metal and grew.

However, during various tests, there is a method of adhering the solidified skull to the lower end of the nozzle depending on whether the hot water is discharged while the nozzle coil is energized or when the hot water is discharged while the energization is stopped. I found something clearly different.
Specifically, when the hot water was discharged while the nozzle coil was de-energized, the solidified skull k-1 was generated in a icicle-like manner from the lower end of the hot water nozzle as shown in FIG. When the hot water was discharged while the nozzle coil was energized, the molten metal from the lower end of the hot water nozzle spread violently outward and solidified in the form of outward spreading at the lower end of the hot water nozzle. I found the fact that Skull k-2 was generated.

  From this, the present inventors have found that the solidified skull that grows by adhering to the lower end of the hot water nozzle is heated by the magnetic field generated by the nozzle coil when the nozzle coil heats the hot water flow by electromagnetic induction. It was thought that the main cause was pulling in the direction.

The present invention has been made based on such findings.
That is, the present inventors can position the lower end position of the nozzle coil above the conventional position if the molten metal coming out from the lower end of the hot water discharge nozzle is pulled outward by the magnetic field created by the nozzle coil. As a result of investigating the appropriate vertical direction and arrangement position there, obtaining a good result by arranging the nozzle coil so that the lower end of the nozzle coil is D or more above the lower end of the tap nozzle. Turned out to be.

  The present invention is capable of effectively suppressing the turbulence of the tapping flow when tapping the molten metal in the crucible, enabling stable tapping, and a large-capacity cold-crucible melting It has the significance of making significant progress toward practical application of melting technology using a furnace.

  In this claim 1, the hot water discharge nozzle has an inverted frustoconical upper funnel portion and a lower straight portion that hangs downward following the funnel portion, and the upper end of the straight portion is located at the upper limit position. As described above, the nozzle coil can be arranged so that the lower end of the nozzle coil is positioned between the position not less than D and the upper limit position.

The funnel at the top of the hot water nozzle is the part that is closed by the solidified skull at the bottom when the metal is levitation melted inside the crucible, and the solidified skull is melted by heating at the start of the hot water. In order to maintain the opening, the nozzle coil needs to be heated. On the other hand, the lower straight part that follows this is a part where heating by the nozzle coil can be omitted in some cases.
Therefore, in the present invention, in an extreme case, it is possible to dispose the nozzle coil only outside the funnel portion and leave the nozzle coil outside the straight portion.

  In the present invention, the apparatus can be configured so that the magnetic flux density at the lower end of the pouring nozzle is 50 mT or less, preferably 20 mT or less during the pouring of the molten metal. It is possible to suppress or prevent the phenomenon that the solidified skull adheres to the lower end portion of the hot water nozzle due to the pulling force.

It is the figure which showed the electromagnetic nozzle apparatus for hot water of one Embodiment of this invention with the cold crucible melting furnace. It is a principal part enlarged view of FIG. It is the figure which showed the principal part of the reference example. It is the figure which showed the principal part of the other reference example. It is the figure which showed the principal part of other embodiment of this invention. It is the figure which showed the measurement position of magnetic flux density. It is explanatory drawing of the malfunction of the conventional electromagnetic nozzle apparatus for hot water. It is explanatory drawing which showed the solution subject of this invention concretely.

Next, embodiments of the present invention will be described in detail with reference to the drawings.
In FIG. 1, 10 is a cold crucible melting furnace, which has a water-cooled copper crucible 12 and a melting coil 14 arranged on the outside thereof.
The crucible 12 is configured by joining arc-shaped water-cooled copper segments divided into a plurality of parts in the circumferential direction into a cylindrical shape via an insulating material.
Reference numeral 16 denotes a crucible bottom portion having a flat plate shape and made of water-cooled copper.

18 is an electromagnetic nozzle device for hot water, and has a hot water nozzle 20 and a nozzle coil 22 arranged outside the hot water nozzle 20.
The hot water nozzle 20 has an upper funnel portion 20-1 having an inverted truncated cone shape, and a lower straight portion 20-2 that hangs downward following the funnel portion 20-1.
The hot water discharge nozzle 20 is also made of water-cooled copper having a divided structure in the circumferential direction, and each segment is connected in the circumferential direction via an insulating material.
Reference numeral 24 denotes a mold installed below the cold crucible melting furnace 10, and M denotes a solidified skull obtained by solidifying the molten metal melted in the crucible 12 by contact with the crucible 12. ing.

In the cold crucible melting furnace 10, a raw material metal is charged into the crucible 12, and the raw material metal inside the crucible 12 energizing the melting coil 14 is melted by high frequency induction heating.
The molten metal M is separated from the wall of the crucible 12 by the Lorentz repulsive force based on electromagnetic induction by the melting coil 14, and becomes semi-floating in a dome shape with the center rising upward in the crucible 12.
And the bottom part cooled in contact with the crucible bottom part 16 is solidified to form a solidified skull K.
At this time, the solidified skull K is in a state of closing the opening of the funnel portion 20-1 at the top of the hot water nozzle 20.

After melting for a certain time by the melting coil 14, the molten metal M in the crucible 12 is poured out into the lower mold 24 by the electromagnetic nozzle device 18 for hot water.
Specifically, the nozzle coil 22 is energized to melt the solidified skull K that closes the opening of the funnel portion 20-1 of the hot water nozzle 20 by high frequency induction heating, and the funnel portion is in a closed state. Open 20-1.
As a result, the molten metal M in the crucible 12 passes through the hot water nozzle 20 and is discharged into the lower mold 24.

In this embodiment, as shown in FIG. 2 (I), the outlet diameter of the outlet nozzle 20, specifically, the diameter of the lower end of the straight portion 20-2 is D (the straight portion 20-2 is the other portion). The inner diameter D), the nozzle coil 22 is arranged outside the hot water nozzle 20 in such a positional relationship that the lower end thereof is positioned L ₁ (L ₁ ≧ Dmm) higher than the lower end of the hot water nozzle 20.

  As a result of the above, according to the present embodiment, when the molten metal M in the crucible 12 is discharged, the molten metal discharged from the lower end of the hot water discharge nozzle 20 is exposed by the magnetic field formed by the nozzle coil 22. The pulling force in the direction is suppressed, and as shown in FIG. 2 (II), it is possible to perform stable pouring without causing disturbance in the pouring flow from the pouring nozzle 20.

In the present embodiment, the upper end of the straight portion 20-2 is set as the upper limit position, and the lower end of the nozzle coil 22 is positioned between the upper limit position and the position above the lower end of the hot water discharge nozzle 20 by D. The coil 22 can be arranged.
That is, in some cases, the nozzle coil 22 may be disposed only in the funnel portion 20-1.

Next, FIG. 3 shows a reference example. In this example, the nozzle coil 22 can be slid up and down, and the nozzle coil 22 is moved to the position shown in FIGS. 3B and 3I (FIG. 3B ( I) Middle L ₁ ≧ D) is set as the upper position, and the upper position and the lower end of the nozzle coil 22 protrude below the lower end of the hot water nozzle 20 by L ₂ (L ₂ ≧ (1/2) Dmm). It is the example which became movable up and down between the lower positions of Drawing 3 (B) (II).

In this example, when the molten metal M is discharged, the nozzle coil 22 is positioned at the upper position shown in FIGS. 3B and 3I, and high frequency induction heating is performed by the nozzle coil 22 in this state.
On the other hand, when the hot water is finished, the nozzle coil 22 is slid down to the lower position shown in FIGS. 3 (B) and (II), and high frequency induction heating is performed by the nozzle coil 22 after the hot water.

In this case, even when the last molten metal M flows down the hot water nozzle 20 when the hot water is stopped, the solidified skull K hangs from the hot water nozzle 20 even if the solidified skull K hangs from the hot water nozzle 20. This can be melted by heating with 22 and removed from the hot water nozzle 20.
Therefore, the next charge melting operation can be performed smoothly and smoothly.

FIG. 4 shows another reference example.
In this example, the nozzle coil 22 is vertically divided into an upper coil 22-1 and a lower coil 22-2, and the upper coil 22-1 is moved to the upper position shown in FIG. This is an example in which the coil 22-2 is arranged side by side on the upper coil 22-1 so that the lower end of the coil 22-2 protrudes downward from the lower end of the hot water nozzle 20 by L ₂ (L ₂ ≧ (1/2) Dmm).
In the example shown in FIG. 4, during the discharge of the molten metal M, the output of the lower coil 22-2 is reduced or made zero with respect to the upper coil 22-1.
On the other hand, the output of the lower coil 22-2 is increased after the hot water, and the solidified skull attached to the lower end of the hot water nozzle 20 is dissolved and removed by the lower coil 22-2.

  According to the example of FIG. 4, in addition to being able to achieve substantially the same effect as that of the example shown in FIG. 3, in addition to the heating at the time of tapping as in the example shown in FIG. There is no need to bother sliding the nozzle coil 22 and simply switching or controlling the energization between the upper coil 22-1 and the lower coil 22-2. There is an advantage that there is no trouble in operation and process. Note that one power source may be connected to the upper coil 22-1 and the lower coil 22-2, and the coil to be energized at the time of and after the hot water may be switched.

Next, FIG. 5 shows still another embodiment of the present invention. In this example, the nozzle coil 22 is disposed at the upper position shown in FIGS. In this example, magnetic field shielding conductive rings 30 and 32 for shielding the action of the magnetic field are interposed between the lower end of the nozzle coil 22 and the mouth of the hot water discharge nozzle 20.
5A is an example in which the magnetic field shielding conductive ring 30 is disposed on the outer peripheral side of the hot water nozzle 20 and below the nozzle coil 22, and the example of FIG. 5B is a taper. This is an example in which the magnetic field shielding conductive ring 32 having a shape is provided so as to protrude downward from the lower end surface of the hot water nozzle 20.

According to this embodiment, due to the magnetic field shielding effect of the magnetic field shielding conductive rings 30 and 32, the magnetic field from the nozzle coil 22 effectively pulls the molten metal flowing out from the lower end of the hot water nozzle 20 outward. It can be suppressed or prevented.
Therefore, also according to this embodiment, it is possible to effectively suppress the phenomenon that the solidified skull adheres to and grows at the lower end of the hot water nozzle 20 during the hot water.

In the present invention, the magnetic flux density at the lower end of the hot water nozzle 20, specifically the lower end position of the hot water nozzle 20, at a position P ₃ away from the inner surface by a distance L ₃ (= 10 mm), is preferably 50 mT or less. The tapping electromagnetic nozzle device can be configured to be 20 mT or less.
By doing in this way, the phenomenon that a solidified skull adheres to the lower end portion of the hot water nozzle 20 due to the outward tensile force of the magnetic field during the hot water can be effectively suppressed or prevented.

[Experimental example]
<Experimental example 1>
Pure titanium sponge titanium and scrap (total 500 kg) are placed in a crucible 12 installed in a chamber capable of controlling the atmosphere, and the chamber is sealed and evacuated to 50 Pa. Enclosed until
Then, the melting coil 14 was energized at an output of 2400 kW and a frequency of 600 Hz to melt the entire amount of the raw metal charged in the crucible 12 and held for homogenization for 30 minutes.

Then, the nozzle coil 22 was energized at an output of 350 kW and a frequency of 10 kHz, and the hot water was started 30 seconds later, and the entire amount of the molten metal was discharged in 60 seconds in a mold having an inner diameter of 500 mmφ × height 750 mm arranged below the hot water nozzle 20. did.
Thereafter, the ingot was cooled to 500 ° C. or lower in an Ar gas atmosphere, and then taken out.

Table 1 shows the results when the hot water discharge nozzle conditions are changed by variously changing the configuration of the electromagnetic nozzle device for hot water, and the result when the hot water is discharged (in Table 1, the difference between the amount of hot water and the charge amount to the crucible of 500 kg is shown. , The amount remaining in the crucible as a solidified skull).
Here No.1 in Table 1 from the lower end of FIG. 2 (I) a medium distance L ₁ -20 mm (i.e. nozzle coil 22 lower end tapping nozzle 20 in the electromagnetic nozzle device for hot water shown in FIGS. 1 and 2 No. 2 when L ₁ is 20 mm, No. 3 when L ₁ is 40 mm, No. 4 when L ₁ is 55 mm, No. 2 _No. 5 is a case where L ₁ is 55 mm and the magnetic field shielding conductive ring 30 shown in FIG. 5A is used, and No. 6 is a case where L ₁ is 55 mm and the magnetic field shielding conductive ring 32 shown in FIG. Each case is shown.

No. 5 uses a water-cooled copper made of water-cooled copper, having an inner diameter d ₁ = φ90 mm, an outer diameter d ₂ = φ230 mm, and a plate thickness t = 6 mm as the magnetic field shielding conductive ring 30 in FIG. distance L ₃ between the lower end of the tapping nozzle 20 is disposed so that the 20 mm.
No. 6 is made of copper as the magnetic field shielding conductive ring 32 in FIG. 5B, and is made of copper and has an inner diameter d ₃ = φ102 mm, an outer diameter d ₄ = φ114 mm, an inner diameter d ₅ = φ70 mm, and an outer diameter d ₆ = φ82 mm. , Height H = 45 mm was used.

Further, the magnetic flux density at the nozzle opening in Table 1 represents the measurement result of the magnetic flux density at the position P in FIG.
In this embodiment, the diameter D of the hot water discharge nozzle 20 is 35 mm (the length of the straight portion 20-2: 225 mm, the number of turns of the nozzle coil 22: 9.5 turns).

  From the results of Table 1, the lower end of the nozzle coil 22 is positioned 40 mm or more above the lower end of the hot water nozzle 20 in accordance with the present invention, and the magnetic field shielding conductive rings 30 and 32 shown in FIG. 5 are used. It can be seen that the outlet flow can be stabilized and good results can be obtained.

<Experimental example 2>
Next, downward slide down the nozzle coil 22 shown after pouring 2, and subjected to heating after tapping by the nozzle coil 22 by changing the L ₂ shown in FIG. 3 (B) (II).
The results are shown in Table 2.

However, No. 7 in Table 2 indicates that the lower end of the nozzle coil 22 is positioned at the same position as the lower end of the hot water nozzle 20 and heating is performed after the hot water is discharged. No. 9 is located below the lower end of 20 and the distance between them (L _{2 in} FIGS. 3 (B) and (II)) is −15 mm, and heating after hot water is performed, L ₂ = − The case where the heating after tapping is performed as 20 mm is shown.

  From the results in Table 2, after pouring, the lower end of the nozzle coil 22 is located below the lower end of the hot water discharge nozzle 20 and the lower end protrudes 20 mm more than (1/2) D from the lower end of the hot water discharge nozzle 20. Thus, it is understood that the solidified skull attached to the hot water nozzle 20 can be well melted and removed by arranging the nozzle coil 22 and heating after the hot water.

  Although the embodiments of the present invention have been described in detail with reference examples, these are merely examples, and the present invention can be implemented in various forms without departing from the spirit of the present invention.

10 Cold Crucible Melting Furnace 12 Crucible 14 Melting Coil 16 Crucible Bottom 18 Hot Spring Electromagnetic Nozzle Device 20 Hot Water Discharge Nozzle 20-1 Funnel 20-2 Straight Portion 22 Nozzle Coil 22-1 Upper Coil 22-2 Lower Coil 30, 32 Conductive ring for magnetic field shielding

Claims (1)

The crucible bottom of a cold crucible melting furnace in which the raw material metal charged in the inside of the water-cooled crucible is induction-melted at a high frequency by a melting coil provided outside the crucible, and the raw metal is melted in a semi-floating state in the crucible And a nozzle coil outside the hot water nozzle. The solidified metal solidified at the bottom of the crucible by the nozzle coil is induction-melted at a high frequency to melt the molten metal in the crucible. In the electromagnetic nozzle device for hot water discharge of a cold crucible melting furnace designed to discharge hot water, the discharge coil diameter of the discharge hot water nozzle is set to D, and the lower end of the nozzle coil is the lower end of the hot water discharge nozzle with respect to the nozzle coil. It is arranged outside the hot water nozzle in a positional relationship that is an upper position above D,
The magnetic flux density at the lower end of the nozzle for hot water generated by high frequency induction heating by the nozzle coil at the time of discharging the molten metal is 50 mT or less,
For the hot water of a cold crucible melting furnace, wherein an outward tensile force due to the magnetic field formed by the nozzle coil is suppressed with respect to the molten metal coming out of the lower end of the hot water nozzle. Electromagnetic nozzle device.

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