JPH06182525A - Method and device for melting and pouring active metal - Google Patents

Abstract

PURPOSE:To correctly pour the molten active metal into the center of the sprue of a die by vertically falling the molten active metal which is small in amount, completely free from pollution, and high in temperature without bringing into contact with other bodies at the position. CONSTITUTION:A relatively small amount of active metal is loaded on a dish- shaped metallic crucible 4 which is placed in a melting chamber 1, and the skull melting is executed by the plasma arc in the atmosphere of the inert gas or in the vacuum. The molten metal 6 of flat spherical shape which is held in the center of the metallic crucible 4 only by cooling the bottom is vertically fallen and poured into the center of the sprue 22 of the die 21 by rapidly rotating the metallic crucible 4 by a rotating means using the torsional coil spring 8. The dish-shaped metallic crucible 4 is provided with an upper surface consisting of a circular horizontal surface where the active metal is loaded and the molten metal is kept, and an inclined surface surrounding this horizontal surface, and provided with a cooling water passage 40 inside.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to precision casting of active metals such as titanium and zirconium, and particularly in the production of small precision castings such as dental, orthopedic or industrial precision parts, with a small amount of contamination. The present invention relates to an active metal melting and pouring method and apparatus for pouring a high-temperature active metal melt, which has no temperature, from a crucible to a vertical drop without touching other objects while directly dropping it into the center of a mold sprue.

[0002]

2. Description of the Related Art Titanium and titanium alloys have excellent heat resistance and corrosion resistance, high specific strength, and extremely excellent biocompatibility. Therefore, titanium and titanium alloys have recently attracted particular attention as artificial bones for orthopedics and dental prostheses. Came to be. However, on the other hand, titanium has a very large chemical affinity for oxygen, nitrogen, carbon, etc., and especially at high temperatures, it reacts with almost all refractories containing these elements immediately and decomposes it.
It has a strong tendency to bind with these elements strongly and become contaminated, resulting in deterioration of mechanical properties. Moreover, since the melting points of reaction products with these elements, such as titanium oxide, titanium nitride and titanium carbide, are much higher than the melting points of titanium itself, these reaction products are once produced. Therefore, the fluidity was significantly impaired, and casting was often difficult when the contamination was severe.

Therefore, it is difficult to dissolve an active metal such as titanium by a refractory crucible used for dissolving a low active metal such as iron and copper, and the reactivity with the active metal is extremely low. Even if it is induction-melted in a fire-resistant crucible such as calcia (CaO) or yttria (Y ₂ O ₃ ), each time it is repeated, unless the contact between the residual molten metal and air is completely cut off Contamination will progress. When melting is performed on these refractory crucibles using an arc, the CaO decomposed by the high temperature arc is used.
Alternatively, oxygen in Y ₂ O ₃ has a strong tendency to contaminate the active metal. Therefore, it can be said that it has been practically impossible to stably obtain a clean molten metal of active metal free from contamination by melting the refractory crucible.

As shown in FIG. 14, the conventional method most widely used industrially as a method for obtaining a clean active metal melt while avoiding contamination by the reaction with a crucible in the dissolution of an active metal such as titanium. It is a skull melting method using a water-cooled copper crucible 34. In this case, the melting is performed in vacuum or in an inert gas atmosphere such as argon, and the metal consumable electrode 33 is
The active metal melt 36 melted by the direct current arc 35 generated between the water-cooled copper crucible 34 and the molten material in the water-cooled copper crucible 34 is cooled by the water-cooled copper crucible 34 to form a solidified shell or skull 36S on its inner surface and melted. The body 36 is stored in a skull 36S having exactly the same composition as that of the body 36, and when the melt 36 reaches a desired temperature and amount, it is injected into the mold by rotating the horizontal rotary shaft 37.

Recently, Japanese Patent Publication No. 3-44133 discloses a method in which the above-described skull melting is further advanced, and a cylindrical crucible is constituted by a plurality of vertically divided water-cooled metal crucibles, and the active metal is induced and melted. It is disclosed. Further, as a structure in which a bottom wall portion of a cylindrical crucible composed of a plurality of vertically cooled water-cooled metal crucibles is separated, induction melting is performed, and the bottom wall portion is separated from a cylindrical side wall portion by a drive mechanism. Therefore, a method of dropping the molten metal vertically downward and injecting the molten metal into a mold is proposed in Japanese Patent Laid-Open No. 4-138865.

[0006] Next, in precision casting such as dental casting which has conventionally been performed with a relatively small amount of melting, a tungsten arc or TIG arc in an inert gas atmosphere such as argon is used as a means for melting an active metal such as a titanium alloy. Water-cooled crucibles have been used most often. A typical example is a method in which a molten material (ingot) is placed on a crucible having a circular opening in the center, and the active metal melted by a TIG arc is allowed to spontaneously drop through the opening and injected into a mold. (See Japanese Examined Patent Publication No. 58-5749), or a crucible divided into two and opened so that injection can be optionally performed, or a device for injecting by rotating a horizontal axis of a box-shaped crucible (JP-A-1). No. 199353), or a device that tilts around a horizontal axis that is eccentric to one of the crucibles (see Japanese Patent Application Laid-Open No. 3-193260).

[0007]

However, the skull melting method using a direct current arc which is widely used in the industrial furnace as shown in FIG. 14 and the above-mentioned Japanese Patent Publication No. 3-44133.
The skull melting method by induction heating disclosed in Japanese Patent Laid-Open Publication No. Hei 4-138865 and Japanese Patent Laid-Open Publication No. 4-138865 are common in that skull melting of an active metal is performed in a water-cooled metal crucible having a side wall. Since it is cooled not only from the bottom surface but also from the side surface, there is a large heat loss, and it is said that it is quite difficult to overheat the melt even in an industrial furnace with a considerably large capacity. Therefore, for small precision casting such as dental casting of active metal that requires overheating of at least about 100 ° C. to fill a very thin tip with a small amount of melting, induction heating by the water-cooled metal crucible as described above. The skull dissolution method was never applied.

Further, among the methods for pouring a small amount of active metal used in the above-mentioned dental casting and the like, the self-falling method that goes through the opening of a non-water-cooled metal crucible pours the melt into the center of the mold sprue. Although there is an advantage that it is easy to do, when the melt of the active metal passes through the opening of the low temperature metal crucible, a considerable amount of heat is lost due to heat conduction, and it is difficult to obtain the high temperature melt. Also, if the diameter of the metal crucible is too small, it becomes difficult for the melt to pass, and if heating is forced, melting crucible accident of the crucible is likely to occur, on the contrary, if the diameter is large, the melt can easily pass, but the unmelted part However, there is a problem in that the temperature of the melt drops due to the dropping of the melt, and the sufficient effect of the hot water is not obtained, resulting in poor hot running.

Next, the conventional method of rotating or tilting the metal crucible has the advantage that injection can be carried out at will, but in the case of a small amount of melt of the active metal, the temperature due to the contact with the crucible during tilting. Since it is easy to cause the descent, and it is difficult to accurately inject the melt into the center of the mold sprue, the melt that has fallen off the center of the sprue is unevenly distributed, and a sufficient riser effect cannot be obtained.
For this reason, it is often difficult to obtain a sound casting.

Further, in the dental casting in which a small amount of active metal is melted and injected, the overheating of the melt, which is particularly indispensable, is limited by the non-water-cooled metal crucible. Melting accidents tended to occur, and it was difficult to reach a sufficient superheated temperature. There was no difference between this oral administration method and the infusion method.

Further, in the dental casting of active metals such as titanium, TIG arc, which has been most often used as a heat source for melting, has a small energy density, a flat arc shape and low heat transfer efficiency. It was difficult to overheat to temperature. This has hindered the adoption of the skull melting method using a water-cooled metal crucible most suitable for melting this kind of active metal, and many of them have been forced to melt in a non-water-cooled metal crucible.

Therefore, an object of the present invention is to solve the above-mentioned problems in a precision casting method using a relatively small amount of active metal, and to precisely inject a clean and high-temperature melt without any contamination into the center of the mold sprue. A method and an apparatus therefor are provided.

[0013]

In order to achieve the above object, the present invention uses a shallow plate-shaped metal crucible as a melting method, aiming at skull melting only by bottom cooling without side cooling. As a result of a trial experiment, it was found that it is possible to melt a flat spherical melt and a skull that leaves a disk-shaped skull at the bottom. Next, regarding the method of injecting the melt, the velocity of the free-falling object is 0 at the start of falling,
Paying attention to the fact that the melt increases with time thereafter, the melt is melted from that position to another position by rotating the dish-shaped metal crucible downward about 90 ° about one end of the melt in advance of the melt falling vertically. It makes it possible to drop vertically without touching an object and directly inject it into the center of the mold sprue.

The apparatus for achieving the method of melting and pouring the active metal comprises a melting means and a rotating means of the crucible, and the melting means comprises an arc generator and a metal crucible, and the metal crucible has a circular horizontal surface and In the form of a shallow dish having an upper surface composed of an inclined surface surrounding a circular horizontal surface, the rotating means of the metal crucible rapidly rotates the crucible downward about one end thereof as an axis to precede the vertical drop of the melt. It has a function of evacuating the melt out of the trajectory of the melt.

The upper surface of the metal crucible is in the form of a shallow dish consisting of a circular horizontal surface for holding the molten material (ingot) in the center and achieving skull melting only by cooling the bottom surface, and an inclined surface surrounding the circular horizontal surface. The inclined surface must prevent the melt from moving in the lateral direction and should not touch the side surface of the melt. For this purpose, assuming that the angle of the inclined surface with respect to the circular horizontal plane is α, the contact angle of the metal melt on the skull is β, and the weight of the active metal to be dissolved is Wgr, the values of D and α are 0.45W. ^By setting the range of ^1/2 ≤ D ≤ 0.6 W ^1/2 10 ° ≤ α <180 ° -β, it is possible to obtain a flat spherical melt retained on a disc-shaped skull. I could find out.

By using the above-mentioned method for melting and pouring active metal and its apparatus, a clean flat spherical metal melt without contamination is directly poured into the center of the mold spout without any contact with other objects. It has become possible. However, as described above, the TIG arc has a low energy density, and the non-water-cooled metal crucible has its own limit in heat capacity. Therefore, if the heating is forced, a melting and melting accident of the crucible is likely to occur. Was not always enough. Therefore, in order to melt / inject a small amount of active metal and completely fill the thin tip portion, at least 100 °
In the case of dental casting that requires superheating close to C, overheating of the metal melt is important, and it can be said that a higher temperature heat source for melting is desirable.

Therefore, it was decided to first apply a melting heat source having a higher energy density than the TIG arc.
The energy density of TIG arc is only 10 ⁴ W / cm ² , but the energy density is larger than this by 2 digits or more 1
A plasma arc, which belongs to a so-called high energy density melting heat source having a value of 0 ⁶ W / cm ² or more,
There are electron beams, laser beams, etc. Among these, in consideration of economical efficiency, workability, energy concentration characteristics, etc., it was decided to adopt the plasma arc most suitable for the purpose of melting a small amount of active metal. Moreover, TIG arc melting usually requires an inert gas pressure above atmospheric pressure,
In arc melting, it is possible to melt not only at atmospheric pressure or higher but also in an inert gas atmosphere of low torr. This was confirmed by a melting experiment from atmospheric pressure to several torrs, in which it is possible to obtain a clean, high-temperature metal melt that is completely free of contamination and is sufficiently heated as compared with the TIG arc.

By adopting the plasma arc described above, it becomes possible to carry out regular skull melting with a water-cooled metal crucible instead of the conventional non-water-cooled metal crucible. In this invention, as a result of a trial experiment using a water-cooled metal crucible provided with a cooling water passage inside the shallow dish-shaped metal crucible, a high temperature flat spherical metal melt at the top and a thin disk-shaped at the bottom. It has been found that complete skull dissolution leaving a skull is achieved. As a result, it is possible to completely dissolve the skull even in a small amount of active metal of about 50 gr or less, and to obtain a sufficiently heated melt of the active metal without any contamination.

Next, in this metal melting / injecting apparatus, the rotating means for rotating the dish-shaped metal crucible penetrates the melting chamber wall from both sides of the melting chamber and has a pair of cooling water passages inside. A rotary shaft of a metal crucible, which also has a cooling water passage inside, is fixed to the horizontal rotary shaft, and the horizontal rotary shaft is rotated by a driving device provided outside the melting chamber, thereby making the metal crucible substantially 90 °. It is designed to rotate downward.

In contrast to the above-mentioned rotating means of the metal crucible by the driving device outside the melting chamber, the present invention further conducted various studies aiming at confining the rotating part only to the inside of the melting chamber, and as a result, as a rotating means of the metal crucible. , Found a method of utilizing the driving force of a torsion coil spring. To describe this concretely, the rotating means for rotating the dish-shaped metal crucible is equipped with a pair of horizontal metal pipes which penetrate and are fixed to the melting chamber wall body from both outer sides of the melting chamber and through which cooling water is circulated. A bearing portion is provided, and a rotating shaft of a metal crucible for circulating cooling water is rotatably attached to the bearing portion, and the metal crucible is substantially fixed by a symmetrical coil coil spring locked to the rotating shaft. ° It is designed to rotate downward.

[0021]

FIG. 5 shows a plasma arc 5 according to the present invention.
It is explanatory drawing which shows the principle of skull melting of the active metal by the water-cooled metal crucible 4. It has been known so far that when a large drop of mercury is placed on a horizontal glass plate, it becomes a flat sphere with a certain thickness. Then, similarly, as shown in FIG. 5, it was confirmed by a preliminary experiment that an oblate spherical melt having a constant thickness h was obtained. However, in the case of mercury, it is on the glass plate, but in this case it is different in that it is dissolved on the skull 6S of the same metal. Therefore, if the weight of the melting material is increased, the molten body will spread in only the lateral direction while remaining in a flat spherical shape.
A suitable diameter D of the circular horizontal plane 42 of can be determined experimentally. Next, the upper surface of the metal crucible 4 is composed of a circular horizontal surface 42 on which the molten material is placed and the molten material 6 is held, and an inclined surface 43 surrounding the circular horizontal surface 42. Now, assuming that the diameter of the circular horizontal plane 42 is Dcm, the angle of the inclined surface 43 of the crucible with respect to the circular horizontal plane 42 is α, the contact angle of the melt 6 on the skull 6S is β, and the weight of the metal material to be dissolved is Wgr. It was found that the range of 45W ^1/2 ≦ D ≦ 0.6W ^1/2 10 ° ≦ α <180 ° −β is appropriate. The lower limit of the inclination angle α of the inclined surface 43 with respect to the circular horizontal surface 42 is set to 10 ° in order to prevent the active metal melt 6 from fluctuating in the lateral direction due to arc blow. By forming the upper surface of the water-cooled metal crucible 4 into the above-mentioned shape, the melt 6 is prevented from moving in the lateral direction and held in the center of the metal crucible 4, and the side surface of the melt 6 does not touch the metal crucible 4. , Skull melting is achieved only by bottom cooling.

For the injection, the metal crucible 4 is rapidly rotated downward around the rotary shaft 41 at one end thereof, and the melt 6 is dropped vertically.
By moving the melt 6 out of the falling trajectory prior to the above, the melt 6 is dropped vertically from the position directly to the center of the mold spout without touching any other object. 10 and 11 are schematic diagrams in which the relative positions of the free-falling melt 6 and the metal crucible 4 after the start of injection are analyzed over time. The diameter of the metal crucible 4 is 40 mm, and the metal crucible 4 rotates from the center. The distance to the center O of the shaft 41 is 30 mm, and the metal crucible 4 is arranged around the center O of the rotary shaft 41 as shown in FIG.
0 indicates a rotation speed of 20 rad / s, and FIG. 11 shows a phenomenon when rotating at a constant angular speed of 16 rad / s. In this case, about 90
It was found that the time required for the rotation of 0 ° was 0.08 s for the former and 0.09 s for the latter, and the objective could be achieved by rotating about 90 ° within approximately 0.09 s.

FIGS. 12 and 13 compare the arc characteristics of a TIG arc and a plasma arc at an arc current of 200 A. As is clear from both figures, TI
On the contrary, the G arc has a low energy density, a flat arc shape, and a low temperature. On the contrary, the plasma arc has a much higher energy density, and has the advantage that the high temperature arc expands well and the heat transfer efficiency is high. It can be said that the adoption of the plasma arc has enabled full-scale skull melting with a water-cooled metal crucible for melting a small amount of active metal.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a metal melting / injecting method and apparatus according to the present invention will be described with reference to the drawings. FIG. 1 is a schematic side sectional view showing an embodiment of a melting / injecting apparatus for achieving the method for melting / injecting an active metal according to the present invention, FIG.
FIG. 2 is a partial sectional view taken along the line AA in FIG. 1. In FIG. 1, an inside of the melting chamber 1 is made an inert gas atmosphere or a vacuum to melt active metals such as titanium and zirconium on a metal crucible 4, and a melt 6 thereof is provided below the melting chamber 1. It is to be poured into the sprue 22 of the mold 21 placed in the No. 2 mold. In this example, pure titanium was used as the molten metal and a water-cooled copper crucible was used as the metal crucible.

In the melting / injection apparatus shown in FIG. 1, a plasma torch 3 slidably hung from the top of a melting chamber 1 and a molten metal are placed and a melt 6 thereof is held and only the bottom surface is cooled. Therefore, the upper surface of the crucible 4 is a shallow dish-shaped metal crucible 4 having a circular horizontal surface and an inclined surface surrounding the circular horizontal surface and having a cooling water passage 40 therein. Rotate to melt 6
The rotating means is provided for retracting the melt 6 out of the orbit of the melt 6 prior to the vertical drop. The plasma torch 3 is connected to the (−) side of the DC power source, and the water-cooled metal crucible 4 is connected to the (+) side.

Next, the rotating means for rotating the metal crucible 4 penetrates into the melting chamber 1 and the fixture 13 as shown in FIG.
A pair of horizontal metal pipes 7 fixed to the wall 11 of the melting chamber 1 and having a cooling water passage 70 therein, the horizontal metal pipes 7
The rotating shaft 41 of the water-cooled metal crucible 4 rotatably attached to the bearing portion 71 at the tip of the shaft, and the left and right symmetrical crucibles that are locked to the rotating shaft 41 to rotate and brake the metal crucible 4 substantially 90 ° downward. It is composed of a torsion coil spring 8 and a stopper 9 which holds the metal crucible 4 horizontally and can be engaged and disengaged. Therefore, the metal crucible 4 is arranged in a cantilevered manner with respect to the horizontal metal tube 7 about the rotation shaft 41.

The torsion coil spring 8 for rotating the metal crucible 4 has a long arm 81 and a short arm 82 as shown in FIG.
As shown in FIG. 4, the coil portion is attached to the rotating shaft 41 of the metal crucible 4, and the long arm 81 is fixed to the lower surface of the metal crucible 4 by the fastener 4.
The pair of short arms 82 on the other end side are fixed to the wall body 11 of the melting chamber 1 by the fasteners 12. Further, the stopper 9 is operated by a solenoid, and is engaged so as to hold the metal crucible 4 in a horizontal position and disengaged so as to rotate the metal crucible. Further, in the casting chamber 2, a mold 21 is placed on a mold lifting device 23.

Next, the steps of melting and injecting an active metal such as pure titanium using the method and apparatus for dissolving and injecting metal according to the present invention will be described with reference to FIGS. First, as shown in FIG. 6A, the metal crucible 4
From the unloaded drooping state to a horizontal position,
The arm angle of the torsion coil spring 8 mounted on the above is urged from 90 ° to 180 °, the metal crucible 4 is supported horizontally by the stopper 9, and the pure titanium ingot 6M is placed on the horizontal plane. Next, vacuum suction means 20 provided in the casting chamber 2 shown in FIG.
After the air in the melting chamber 1 and the casting chamber 2 is completely replaced with the high-purity argon gas by the gas supply means 10, the pressure is reduced to about 100 torr or less by vacuum suction.

Next, plasma torch 3 and ingot 6M
Plasma arc 5 is generated between and, and the melting of pure titanium ingot 6M is started. Dissolution is the ingot 6M
From the top to the bottom, but melting progresses and melt 6
In the stage in which is sufficiently overheated, as shown in FIG. 6B, a flat spherical melt 6 and a thin disk-shaped skull 6S are formed on the bottom surface. At this stage, when the solenoid is urged to release the stopper 9, the center of gravity of the melt 6 is rotated while the metal crucible 4 is rotated downward by about 90 ° due to the restoration of the torsion coil spring 8, as shown in FIG. 6 (c). Shifts from G ₀ to G ₁ , the melt 6 falls vertically without touching any other object, and as shown in FIG. 1, the melt of the mold 21 placed on the lifting device 23 of the casting chamber 2 is lowered. It is poured into the center of the sprue 22.

In the above embodiment, as the rotating means for rapidly rotating the metal crucible 4, the integral type symmetrical coil spring 8 mounted on the back surface of the metal crucible 4 is used. The same effect can be obtained by using two torsion coil springs in a divided form.

Further, in the above embodiment, the torsion coil spring 8 is used as the rotating means for rapidly rotating the metal crucible 4, but the metal crucible 4 can be rotated by the driving device provided outside the melting chamber 1. Is. Another embodiment of the rotating means will be described with reference to FIGS. 7 and 8. Figure 7
Is a partial side sectional view showing another embodiment of the rotating means in the present invention, and FIG. 8 is a partial plan view of the rotating means of FIG.

Rotating means for rotating and braking the metal crucible 4 penetrates the wall 11 of the melting chamber 1 and has a horizontal rotary shaft 17 having a cooling water passage 70 therein, and is screwed to the horizontal rotary shaft 17. Metal crucible 4 having a cooling water passage 40 inside
And a rotary actuator 18 having a swing angle of 90 ° which is provided outside the melting chamber 1 and drives the metal crucible 4 to rotate downward by 90 °. The rotating means is not limited to the above rotating means, and is provided with a function of rotating the metal crucible 4 downward by about 90 ° prior to the vertical drop of the molten material so that the molten material 6 is retracted out of the orbit. If so, it is naturally possible to use other drive devices.

Although the metal crucible 4 is described as an integral type in each of the above embodiments, it is also possible to adopt an assembly method in which the metal crucible is divided into a main body 4 and a liner 4L as shown in FIG. In this case, the inclination angle α formed by the circular horizontal surface 42 forming the upper surface of the metal crucible 4 and the inclined surface 43 surrounding it is constant, and the diameter D of the circular horizontal surface depends on the amount of the dissolved material.
It can be selected stepwise according to the diameter of the molten material (ingot).

Although it was expected that the melt 6 receives a lateral component force when the metal crucible 4 rotates due to the adhesive force between the melt 6 and the skull 6S, it may be prevented from falling vertically. In this invention, the fluidity of the high-purity active metal melt was extremely good, and such an undesirable situation did not occur.

[0035]

According to the present invention, when the plasma arc and the water-cooled metal crucible are used, the energy density of the arc can be kept extremely high, and more than a normal pressure, of course, a few t.
It is possible to melt over a wide range up to the vacuum region of orr, and it is possible to stably obtain a sufficiently overheated molten metal of the active metal which is free from contamination even in a small amount. The disk-shaped skull generated in the lower part of the melt is rapidly cooled by a water-cooled metal crucible, so it is recovered without any contamination, so it retains its metallic luster and can be reused as it is as a melting material, reducing material costs. be able to.

When melting is carried out in a non-water-cooled metal crucible, it is difficult to keep the melting condition continuously and constant due to the temperature rise of the metal crucible, which is one factor that hinders the automation of the operation. However, when a plasma arc and a water-cooled metal crucible are used in the present invention, the metal crucible can maintain a constant temperature by cooling water, so if the melting power is kept constant, a constant amount of heat input by plasma arc heating, Due to the difference from the constant loss of heat carried away by the cooling water, the amount of heat accumulates over time and the temperature of the melt rises. Therefore,
There is a certain relationship between the weight of dissolved material and the dissolution time,
This can be quantified experimentally to contribute to the complete automation of the operation.

Furthermore, according to the present invention, since the skull is formed only on the bottom surface of the melt and not on the side surface at all, the ratio of the melt portion can be kept high and the active metal melt can be kept from its position. Since it is dropped vertically without touching other objects on the way, there is no heat loss due to contact, and a clean and high-temperature active metal melt can be directly injected into the center of the mold sprue. As a result, the effect of hot water around the tip of the product and the effect of pushing the hot water are remarkably improved, and the product quality and yield can be improved.

In the injection means according to the present invention,
When a torsion coil spring is used to rotate the water-cooled metal crucible, the rotating part is limited to the water-cooled metal crucible only, and the torsion coil spring has both rotary drive and braking functions. Further, compared with the case of using the braking means, a special drive source and a transmission device are not required, the structure is simple and the weight is reduced, and the facility cost and the operating cost can be reduced. Since all parts including the coil portion of the torsion coil spring are cooled and shielded by the water-cooled metal crucible, no special heat-resistant spring is required and a normal torsion coil spring can be used.

[Brief description of drawings]

FIG. 1 is a schematic side sectional view showing an embodiment of a melting / injecting apparatus for achieving a method for melting / injecting an active metal according to the present invention.

FIG. 2 is a partial cross-sectional view taken along the line AA in FIG.

FIG. 3 is a perspective view showing an embodiment of a torsion coil spring used in the rotating means of the metal crucible in the present invention.

4 is a rear view showing a state where the torsion coil spring of FIG. 3 is attached to a metal crucible.

FIG. 5 is an explanatory view showing the principle of skull melting of an active metal on a metal crucible according to the present invention.

6A to 6C are process diagrams of an embodiment for melting and injecting an active metal according to the present invention.

FIG. 7 is a partial side sectional view showing another embodiment of the rotating means of the metal crucible according to the present invention.

8 is a partial plan view of the rotating means of FIG. 7. FIG.

FIG. 9 is a side sectional view showing another embodiment in which the metal crucible is of a split type in the present invention.

FIG. 10 is an explanatory diagram for analyzing the relative positions of the free-falling melt and the metal crucible at the time of pouring in this active metal melting / pouring method.

FIG. 11 is another explanatory diagram when the rotation speed of the metal crucible in FIG. 10 is changed.

FIG. 12 is an explanatory diagram showing arc characteristics of a TIG arc.

FIG. 13 is an explanatory diagram showing arc characteristics of a plasma arc.

FIG. 14 is an explanatory diagram showing an example of a conventional active metal skull melting apparatus.

[Explanation of Codes] 1: Melting chamber 2: Casting chamber 3: Plasma torch 4: Metal crucible 41: Rotating shaft 5: Plasma arc 6M: Ingot 6: Melt material 6S: Skull 7: Horizontal metal tube 8: Torsion coil Spring 21: Mold

Claims (6)

[Claims] 1. A method for melting and injecting an active metal, wherein a skull of an active metal is melted using a metal crucible in an inert gas or a vacuum, and a molten metal is poured into a mold. Skull melting only by bottom cooling,
Melt a flattened spherical melt on a disc-shaped skull formed on a metal crucible, then rapidly rotate the crucible downward to precede the vertical drop of the melt outside the drop trajectory of the melt. A method for melting and pouring an active metal, characterized in that by evacuating, the melt is dropped vertically from that position without touching other objects, and is poured into the center of the mold sprue. 2. An arc in an active metal melting / injecting apparatus for injecting a molten metal into a casting spout located below by performing skull melting of the active metal by applying an inert gas atmosphere or vacuum to the inside of the melting chamber. Melting means comprising a generator, a circular horizontal surface and a dish-shaped metal crucible having an upper surface composed of an inclined surface surrounding the circular horizontal surface, and a rapid rotation of the crucible downward to melt prior to the vertical drop of the melt. An apparatus for melting and injecting active metal, comprising: rotating means for retracting the body out of a falling trajectory. 3. The diameter of a circular horizontal surface forming the upper surface of the metal crucible is Dcm, the angle of the inclined surface with respect to the circular horizontal surface is α, the contact angle of the metal melt on the skull is β, and the weight of the molten metal material is Wgr. Then, D and α are in the range of 0.45W ^1/2 ≦ D ≦ 0.6W ^1/2 10 ° ≦ α <180 ° −β. Dissolution / injection device. 4. The melting means for an active metal according to claim 2, wherein the melting means uses a plasma arc generator as an arc generator and a metal crucible having a cooling water passage therein. -Injection device. 5. The rotating means includes a horizontal rotary shaft that penetrates the melting chamber wall body, is fixed to one end of the metal crucible, and circulates cooling water inside the metal crucible, and the horizontal rotating shaft is provided outside the melting chamber. The driving device for rotating the metal crucible downward by substantially 90 ° by rotating the metal crucible.
Injection device. 6. The rotating means comprises a horizontal metal tube that penetrates and is fixed to the wall of the melting chamber to circulate cooling water inside the metal crucible, a rotary shaft of the metal crucible rotatably attached to the horizontal metal tube, Lock the metal crucible to the rotary shaft
The apparatus for melting and injecting active metal according to claim 2, characterized in that the apparatus comprises an symmetric torsion coil spring that rotates downward and a stopper that can be engaged with and disengaged from a metal crucible.