JP2005153002A - Rotary tapping type casting apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To miniaturize a rotary tapping type casting apparatus in which a crucible is inversely rotated to tap molten metal subjected to vacuum melting into a mold. <P>SOLUTION: The casting apparatus comprises: a levitation melting furnace 4 in which the outside of a water-cooled metal crucible 1 is provided with a coil 2, and tapping is performed from an opening 3 at the upper face by inversion rotation; a mold 6 connected to the upper face of the crucible 1 so that a sprue 5 faces the opening 3; and a vacuum exhaust system vacuum-exhausting the crucible 1 and the mold 6, wherein a sealing vessel 13 is arranged between the crucible 1 and the coil 2 so as to seal the crucible 1, and the crucible 1 is airtightly connected to the mold 6 sealed by a sealing vessel 16. Not the whole bodies of the levitation melting furnace 4 and the mold 6 are stored into the sealing vessels, but, only the crucible 1 is sealed by the sealing vessel 13 in the levitation melting furnace 4, and the crucible 1 is airtightly connected to the mold to attain the sealing of the crucible 1 and the mold 6, thus the volumes of the sealing vessels 13 and 16 are minimized, and the apparatus can be miniaturized. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

    The present invention relates to a casting apparatus used for melting and casting a metallic biosubstitute material for dentistry that requires precision casting and a high melting point active metal alloy in the decoration and industrial fields.

  For casting materials for dentistry, expensive metal materials typified by gold alloys (12% gold-palladium-silver alloy) have been used because of high safety, biocompatibility, and long-term reliability requirements. Has been. Since these casting materials have a relatively low melting point of 1300 ° C. or less and a small specific gravity, the conventional resistance heating melting method can sufficiently cope with melting. Further, even in the case of a single metal that is not required to be alloyed, a high melting point metal for decoration and industry can be handled by the arc heating melting method. This type of dental medical casting apparatus is described in Patent Document 1, for example.

On the other hand, as a dental medical material, instead of expensive gold alloys, the application of titanium-based alloys that are safe for the human body and high in biocompatibility while being reasonable in price has attracted attention. However, this new titanium alloy has a high melting point of around 3000 ° C, such as Ta and Nb, and a density difference of around 20 g / cm ³ compared to 4.5 g / cm ^{3 of} Ti in order to have biocompatibility. Therefore, it is necessary to use an extremely large high melting point active metal as an alloy element, which cannot be dissolved by conventional resistance heating or arc heating, and cannot be uniformly alloyed.

  In that case, the so-called levitation melting method is suitable for alloying the high melting point active metal. In the levitation melting method, a metal is put into a water-cooled metal crucible wrapped with a coil, and a high-frequency current is passed through the coil. An alternating magnetic field generated in the crucible generates an eddy current in the opposite direction to the coil current in the metal. The metal melts due to Joule heat, and the metal levitates due to the electromagnetic repulsion between the two currents. The levitation melting method can dissolve active metal elements having a very high melting point of around 3000 ° C., and a molten alloy with a large density difference is homogenized because it is stirred by a strong electromagnetic force. Further, since the metal is dissolved in a non-contact state with the crucible, there is little contamination with impurities from the crucible. A melting furnace (floating melting furnace) using this levitation melting method is described in Patent Document 2, for example.

  FIG. 3 is a schematic longitudinal sectional view showing a conventional configuration of a rotary tapping casting apparatus using the above-described levitation melting method. In FIG. 3, the casting apparatus includes a coil 2 on the outside of a water-cooled metal crucible (hereinafter simply referred to as “crucible”) 1 having an open upper surface, a levitating melting furnace 4 that is discharged from the opening 3 by an inverted rotation, and an opening 3. The mold 6 is connected to the upper surface of the crucible 1 so that the gate 5 is opposed to the crucible 1, and the evacuation system 7 evacuates the crucible 1 and the mold 6. The mortar-shaped crucible 1 is composed of a large number of copper segments divided by slits (not shown), and is cooled by cooling water flowing through a cooling pipe (not shown). The mold 6 is made of a breathable mold material (an investment material), and a casting space 8 is formed by a lost wax method. The crucible 1 and the mold 6 are entirely incorporated in a sealed container 9 and evacuated from the bottom of the crucible by an evacuation system 7.

In the casting apparatus of FIG. 3, when the molten metal 10 is loaded into the crucible 1, a vacuum pump (not shown) of the evacuation system 7 is operated to evacuate the crucible 1 and the mold 6. Next, the coil 2 is energized from the high-frequency power source 11 to float and melt the metal 10. As already known, when a high-frequency current is passed through the coil 2, eddy currents are induced in the crucible 1 and the metal 10, and an electromagnetic repulsive force is generated between these currents. At this time, if the electromagnetic repulsion force is larger than the weight of the metal 10, the metal 10 floats away from the crucible 1. At the same time, the metal 10 is melted by Joule heat caused by eddy current. When the metal 10 is melted, the entire casting apparatus including the airtight container 9 is rotated 180 degrees about the horizontal shaft 12 centering on the power introduction terminal 21 to invert the levitation melting furnace 4 and the mold 6. Thereby, the molten metal 10 in the crucible is poured out into the mold 6 and cast into the casting space 8 from the gate 5. FIG. 4 shows a casting apparatus that is turned upside down.
JP 2000-176629 A Japanese Patent Laid-Open No. 10-38468

However, the conventional rotary hot water casting apparatus as shown in FIG. 3 has the following problems.
(1) The levitation melting furnace and the entire mold are assembled in a sealed container and evacuated, but the evacuation response is poor due to the large volume of the sealed container. By the way, the crucible communicates with the sealed container through the slit between the copper segments, and the mold communicates with the sealed container through the breathable mold material. Will be done.
(2) Since a large-capacity sealed container is rotated, rotation operability is poor and a large installation space is required.
(3) Since the coil is housed in a sealed container in a vacuum atmosphere, there is a possibility that a vacuum discharge will occur during energization, and the coil voltage must be limited to a level that does not pose a risk of vacuum discharge.
(4) Since there is only one evacuation system, the mold cannot be evacuated alone during casting, and the molten metal cannot be pushed into the casting space due to the pressure difference from the crucible side.
(5) Since a power introduction terminal that can ensure airtightness in the sealed container is required, the structure of the apparatus becomes complicated and expensive.

  SUMMARY OF THE INVENTION The present invention addresses the above problems, and is intended to simplify, reduce the size and cost of the apparatus, eliminate the risk of coil vacuum discharge, and improve casting quality.

  In order to solve the above-mentioned problems, the present invention is provided with a coil on the outside of a water-cooled metal crucible whose upper surface is open, and a water-cooling furnace that discharges hot water from the opening by an inverted rotation, and the water-cooling so that the gate faces the opening. A mold connected to the upper surface of a metal crucible, and a vacuum exhaust system for evacuating the water-cooled metal crucible and the mold, energizing the coil to levitate and dissolve the metal in the water-cooled metal crucible, and then the levitating and melting In a rotary tapping type casting apparatus that inverts the furnace and casts molten metal into the mold, a sealed container is disposed between the water-cooled metal crucible and the coil to seal the water-cooled metal crucible, and the water-cooled metal crucible is sealed. The mold sealed by the container is connected in an airtight manner (claim 1).

  The invention of claim 1 does not house the entire flotation melting furnace and mold in a sealed container, but the flotation melting furnace seals only a crucible with a sealed container, and the mold sealed with the sealed container is hermetically connected to the crucible. Then seal the crucible and mold. This reduces the size of the sealed container and minimizes the volume, increases the responsiveness of the atmosphere control (evacuation and pressurization control) in the crucible and the mold, facilitates the rotating operation, and reduces the installation space. The In addition, since the coil goes outside the sealed container, it is under atmospheric pressure, and there is no danger of vacuum discharge even when the crucible and the mold are evacuated, and the power inlet terminal part to the sealed container needs to be airtight. As a result, the structure of the apparatus is simplified.

  In the invention of claim 1, it is preferable to perform the inverted rotation of the flotation melting furnace and the mold while the coil is energized (invention 2). Thereby, the fall of the molten metal temperature at the time of an inverted rotation can be prevented.

  In the first aspect of the present invention, there are provided first and second evacuation systems for individually evacuating the interior of the water-cooled metal crucible and the air-permeable mold, and when the molten metal is cast into the mold. The evacuation of the first evacuation system may be stopped and the evacuation of the second evacuation system may be performed (Claim 3). By making the crucible and the mold evacuation system independent of each other, at the time of casting, the evacuation of the first evacuation system on the crucible side is stopped, and the evacuation of the second evacuation system on the mold side is performed. During this time, a differential pressure is generated, and the molten metal is pushed into the casting space with this differential pressure to perform precise casting.

  In the invention of claim 3, the water-cooled metal crucible evacuated and a pressurization system for replacing the inside of the mold with an inert gas are provided, and the water-cooled metal is used when the molten metal is cast into the mold by the pressurization system. The inside of the crucible may be pressurized (Claim 4). By replacing the evacuated crucible and mold with an inert gas, the metal can be dissolved in a more reliable oxygen-blocking atmosphere, and at the time of casting, the crucible side is pressurized with an inert gas pressurization system, The casting pressure can be further enhanced by increasing the differential pressure between the mold and the mold.

  In the invention of claim 1, centrifugal casting may be performed by rotating the mold in which the molten metal is cast integrally with the flotation melting furnace (invention 5). Thereby, a more precise casting becomes possible.

  According to the present invention, in a rotary hot water casting apparatus that melts metal in an oxygen-blocking atmosphere and discharges the molten metal to the mold by the inverted rotation of the crucible and the mold, the sealed container for evacuation and inert gas replacement is reduced in size. To improve the responsiveness of evacuation and pressurization, improve the operability of rotation, and save installation space. Also, the coil can be placed under atmospheric pressure to eliminate the danger of vacuum discharge and simplify the apparatus. Furthermore, the pressure difference between the crucible side and the mold side during casting can be increased, and the casting quality can be improved by improving the temperature of the hot water.

  FIG. 1 is a schematic longitudinal sectional view of a rotary hot water casting apparatus showing an embodiment of the present invention, and FIG. 2 is a diagram showing an inverted rotation state thereof. In addition, the same code | symbol shall be used for the part corresponding to a prior art example. In FIG. 1, a cylindrical crucible 1 is hermetically sealed by a sealed container 13 disposed between the coil 2 and the crucible 1. The sealed container 13 is a bottomed cylindrical shape made of a non-metallic material such as FRP (fiber reinforced plastic), and is fitted into the columnar crucible 1 from below. In addition, the crucible 1 has an intermediate portion that is escaped while leaving the upper and lower ends of the outer peripheral surface of the cylinder, and only the upper and lower ends are in close contact with the sealed container 13 to enhance the sealing performance. Connected to the bottom of the crucible 1 are a first evacuation system 14 that evacuates the crucible through a sealed container 13 and a first pressurization system 15 that replaces the crucible with an inert gas such as argon. .

  The cylindrical mold 6 is hermetically sealed with a sealed container 16. The sealed container 16 has a cap shape with a lower flange, and receives a radiant heat from the molten metal through the mold 6. For example, the sealed container 16 is made of a nonmagnetic metal material such as a stainless steel plate, and a packing (not shown) is attached to the crucible 1 through the lower flange with screws. It is connected in an airtight manner. Ventilation spaces 17 and 18 are opened between the upper and outer peripheral surfaces of the air-permeable mold 6 and the sealed container 16, and a second vacuum exhaust system 19 for evacuating the interior of the mold so as to communicate with the upper ventilation space 17 and A second pressurization system 20 for replacing the inside of the mold with an inert gas is connected. A plurality of protrusions 6 a are provided on the outer edge of the upper surface of the mold 6, and the mold 6 is pressed and fixed to the upper surface of the crucible 1 through the protrusion 6 a by the sealed container 16.

  When the molten metal 10 is loaded into the crucible 1, the crucible 1 and the mold 6 are evacuated by the first and second evacuation systems 14 and 19. When the inert gas atmosphere is used, the inert gas is sealed by the first and second pressurization systems, and the crucible 1 and the mold 6 are placed in a predetermined level of oxygen-blocking atmosphere (vacuum atmosphere or inert gas atmosphere). ). Next, a high frequency current is supplied from the high frequency power source 11 to the coil 2, and the metal 10 in the crucible 1 is melted in a floating state to form a molten metal. When the metal 10 is dissolved, the crucible 1 is horizontally integrated with the mold 6 immediately in the case of a vacuum atmosphere, or in the case of an inert gas atmosphere, after the inert gas is exhausted by the first and second vacuum exhaust systems 14 and 19. Rotate 180 degrees around axis 12 and invert as shown in FIG. In that case, the coil 2 is kept energized to prevent a temperature drop of the molten metal.

  In the case of the inverted rotation, when the molten metal reaches the gate 5 or immediately before the molten metal is melted in a vacuum atmosphere (vacuum melting), the second vacuum exhaust system 19 starts evacuating the mold 6. As a result, a differential pressure is generated between the crucible 1 and the mold 6, and the molten metal is pushed into the casting space 8 by this differential pressure, and the hot water is improved. Moreover, it is good to pressurize the crucible 1 which sends in inert gas from the 1st pressurization system | strain 15 simultaneously with the start of evacuation of the casting_mold | template 6 mentioned above. Thereby, the above-described differential pressure is increased, and the hot water is improved. After completion of casting, energization of coil 2, evacuation, pressurization with an inert gas, etc. are stopped to cool the cast metal.

  In the illustrated embodiment, the sealed container 13 of the crucible 1 is disposed inside the coil 2, and the mold 6 sealed by the sealed container 13 is airtightly connected to the crucible 1. Therefore, the volume of the sealed containers 13 and 16 is reduced, and the vacuum / pressurization space in the illustrated embodiment is substantially limited to the inner space of the crucible 1 and the mold 6. As a result, the responsiveness of evacuation and pressurization becomes faster, and the time required for casting is shortened. Further, since the coil 2 is placed outside the vacuum atmosphere and there is no danger of vacuum discharge, the melting time can be shortened by increasing the coil voltage, and the power supply terminal portion for the coil 2 does not need to be airtight. Therefore, the structure of the sealed container 13 is simplified. Further, since the sealed containers 13 and 16 are reduced in size, the installation space is reduced and the rotation inversion operation is facilitated.

  On the other hand, the crucible 1 and the mold 6 are provided with first and second evacuation systems 14 and 19, respectively. Therefore, the vacuum evacuation on the crucible side is stopped at the time of casting, and a differential pressure is generated between the crucible 1 and the mold 6 by evacuating the mold side, and the molten metal is pushed into the casting space by this differential pressure. Dense casting can be performed. Moreover, in that case, the said differential pressure | voltage can be increased and casting quality can be improved more by sending inactive gas from the 1st pressurization system | strain 15 to the crucible 1, and pressurizing.

  Note that the vacuum evacuation may continue during melting, and only the vacuum evacuation of the crucible 1 may be stopped during the inverted rotation after melting, and the vacuum evacuation of the mold 6 may be continued. Moreover, the casting mold 6 into which the molten metal is cast can be rotated around the vertical axis integrally with the levitation melting furnace 4 to perform centrifugal casting, thereby enabling more precise casting.

It is a longitudinal cross-sectional view of the rotary tap type casting apparatus which shows embodiment of this invention. It is a figure of the state which rotated the rotary hot water type casting apparatus of FIG. 1 upside down. It is a longitudinal cross-sectional view which shows the conventional rotary tapping type casting apparatus. It is a figure of the state which rotated the rotary hot water type casting apparatus of FIG. 3 upside down.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Water-cooled metal crucible 2 Coil 3 Opening 4 Levitation melting furnace 5 Pouring gate 6 Mold 8 Casting space 13 Sealed container 14 1st vacuum exhaust system 15 1st pressurization system 19 2nd vacuum exhaust system 20 2nd pressurization system

Claims (5)

A coil is provided outside the water-cooled metal crucible whose upper surface is opened, and a floating melting furnace for discharging hot water from the opening by inverted rotation, a mold connected to the upper surface of the water-cooled metal crucible so that the gate faces the opening, It consists of a water-cooled metal crucible and an evacuation system that evacuates the inside of the mold, energizes the coil to float and melt the metal in the water-cooled metal crucible, and then inverts and rotates the float-melting furnace to melt the molten metal into the mold In the rotary tapping type casting machine that is cast into
Rotating hot water characterized in that a sealed container is disposed between the water-cooled metal crucible and the coil to seal the water-cooled metal crucible, and a mold sealed with the sealed container is hermetically connected to the water-cooled metal crucible. Type casting equipment.   2. The rotary hot water casting apparatus according to claim 1, wherein the levitating melting furnace and the mold are rotated upside down while the coil is energized.   First and second evacuation systems are provided for individually evacuating the interior of the water-cooled metal crucible and the gas-permeable mold, and the first vacuum evacuation is performed when the molten metal is cast into the mold. The rotary hot water casting apparatus according to claim 1, wherein the vacuum exhaust of the system is stopped and the vacuum exhaust of the second vacuum exhaust system is performed.   A pressure system for replacing the water-cooled metal crucible and mold evacuated with an inert gas is provided, and the pressure system pressurizes the interior of the water-cooled metal crucible when casting the molten metal into the mold. The rotary tapping type casting apparatus according to claim 3. 2. The rotary hot water casting apparatus according to claim 1, wherein the casting in which the molten metal is cast is rotated integrally with the floatation melting furnace to perform centrifugal casting.