JPS635863A - High frequency precision casting apparatus - Google Patents

Abstract

PURPOSE:To efficiently produce a casting having excellent quality with non- metal or metal by forming a crucible charging casting material by graphite or carbon in the titled apparatus for precision casting of metallic dental prosthesis. CONSTITUTION:A casting part 1 constitutes a mold part 5 composing of a cylindrical heating room 2, the crucible 3 and a mold 4, and a mold table 15, which lays the mold 4 and moves vertically to contact as pushing with the crucible 3 by a mechanism 13. The heating room 2 winds a high frequency induction heating coil 8 at the outer circumference of refractory cylindrical body 6 and arranges reducing pressure or Ar gas blowing guide pipe 10 and Ar gas or air pressurized guide pipe 11. In this high frequency precision casting apparatus, the crucible is formed by the graphite or the carbon and heated by induction heating to melt the casting material 25 in the crucible 3. Further, in case of being afraid of eroding the crucible 3 by gas generated from molten material, such as glass, etc., refractory coating 26, such as alumina, etc., is formed as supplying on the inner wall of crucible 3.

Description

[Detailed Description of the Invention] (]) Industrial Application Field This invention is a method for heating non-metallic materials such as galanus, ceramics, and plastics, which cannot be melted or cast, by using a high-frequency induction heating method because no eddy current is induced. A high-frequency precision casting device that melts in an ambient atmosphere or atmosphere, pressurizes an inert gas, etc., and casts it into a mold to produce small precision cast products for dental, craft, or decorative purposes. Regarding.

(2) Prior Art Dental prostheses conventionally used in dental treatment are made from the following three virtue materials. One of them is precious metals such as gold or silver alloys and nickel-chromium alloys.

- Metal materials such as non-noble metals such as chromium alloys and titanium alloys; secondly, ceramics used in porcelain and the like; and thirdly, plastics used in denture bases. The metal materials mentioned above have traditionally been precision cast and there is no problem, but the second ceramic cannot be cast. It is made into a shape, layered layer by layer to form the shape of the tooth crown, and then fired.
There are many complicated techniques involved in this technical operation, and the production of ceramic prostheses requires much more IJ and
It has the disadvantage of having a high f value and having to rely on the experience and intuition of an excellent technician. Furthermore, metal-cast porcelain crowns use metal as a reinforcing material to compensate for the brittleness of ceramics.
Metal is placed on the dentin. Therefore, a different ceramic called opaque porcelain had to be used to hide the metallic color, and at the same time, an ivory color had to be created artificially, making the process even more difficult.

For example, it is extremely difficult to reproduce the naturally transparent color tone of natural teeth in the thin layer near the top of the tooth. To solve this problem, many years of research has been conducted to create dental crowns by casting only ceramics without using any metal, and recently this material was developed in the United States as a material for restoring dental crowns.

It is a mica crystal ceramic called "Dicore". This material is formed into glass by casting and then subjected to a controllable heat treatment to form mica crystals in the material, converting it into crystallized glass, or in other words, becoming a "glass ceramic." Dental crowns made using this material have a number of excellent properties such as translucency similar to that of natural teeth, are easy to cut, and have strength and hardness close to those of natural teeth, and are attracting attention in the field of dental prosthetics as a new prosthetic material. is bathed in However, the current casting machine that precision casts this "glass ceramics" uses an electrothermal melting centrifugal casting method that uses a platinum rhodium heating element, or because the heating element is a precious metal, it is expensive. It's an attack just because it is.

It is susceptible to reducing atmosphere, metallic gas, steam, and carbon at high temperatures, and the maximum allowable temperature of the heating element is approximately 14 degrees.
00°C - Materials with a higher melting point than the above-mentioned "glass/ceramic flux" cannot be cast. Furthermore, since the glass material is poured into the mold by centrifugal force, the casting pressure is limited to at most 1 kq/d, and there is also the problem that it is difficult to cast very dense castings.

(3) Purpose This invention was made in view of the above-mentioned current situation,
For mica crystal ceramics, which have excellent properties as dental prosthetic materials, as well as other non-metallic materials such as glass, ceramics, and plastics, we create an atmosphere suitable for each material and melt each material within it. However, by applying the desired casting pressure with inert gas or air and casting into a mold, no matter how dense or complex the shape of the cast product, it is free from defects and of excellent quality. Good car.

Furthermore, the object is to provide an inexpensive device that is easy to operate and perform casting.

(4) Structure The Takaoka Nami rice compact casting device according to the present invention approximates the basic structure M of the conventional high frequency melting and pressure casting device that has been widely used for precision casting of dental prostheses made of metal materials. There is. The main point of this invention is that since the material to be cast cannot be heated by induction, graphite is a conductor that generates heat by inducing eddy currents in the crucible containing the material by high-frequency radiation. Or made of carbon.

The structure is such that the material to be cast is melted through heat generated by induction heating in the crucible. The structure of pouring the molten metal into the mold by applying active pressure or air pressure during melting is the same as that of the conventional apparatus.

The mold placed at the bottom of the crucible is molded with a phosphate-based investment material with a mold cavity formed inside, and the runner of the crucible is positioned on the vertical line of the mold sprue, with a slight distance. However, it may be placed separately.

Usually, the crucible and the mold are integrally connected in a convex shape. A fireproof coating may also be formed on the wall surface, particularly the inner wall, of the crucible.

(5) Examples The present invention will be explained in detail below with reference to the drawings. The figure is a longitudinal partial cross-sectional view of the casting section of the high-frequency precision casting apparatus according to the present invention. The structure of the entire device has already been described in detail in the official gazette of Japanese Patent Publication No. 60-54825 ``High Frequency Melting and Pressure Casting Machine'', which was invented by the authors, so illustrations and explanations of the structure will be omitted, and the present invention will not be described here. The directly related mold section and casting section will be explained in detail. In the figure, the casting part (1) includes a cylindrical heating chamber (2), a mold part (5) consisting of a crucible (3) and a mold (4), and a mold stand C on which the mold part (5) is placed.
151 and a mold lifting/lowering pressure welding mechanism that lifts and lowers the mold. The heating chamber (2) is arranged around the outer periphery of the refractory cylindrical body (6).
A high-frequency induction heating coil (8) covered with a cooling water circulation jacket (7) is wound, and a peephole (9) made of a fire-resistant translucent material is provided at the upper end to seal it. A vacuum or argon gas discharge conduit αG and an argon gas or air pressurization conduit α11 are provided on the side.

However, the illustration of the piping connector of αωQll is omitted. The mold elevating and lowering pressure welding mechanism is constituted by, for example, a pneumatic cylinder (not shown), and lifts and lowers the mold base opening 9 via a universal joint α at the tip of its piston 03. There is a ventilation hole αa in the mold table 05).
The mold part (5) is placed through a gasket α81 which also has a ventilation hole α'71.

The mold (4) of the mold part (5) is formed by molding a mold cavity part (2) using, for example, a phosphate-based investment material αα using the internal melting lost wax method. Note that a mold ring surface may be used to reinforce the mold (4). The mold (4) is mounted on a heating chamber pedestal made of a trowel made of asbestos molded material, which is physically engaged with the heating chamber cylindrical body (6) through the ring-shaped gas keft by the rising pressure welding force of the mold elevating/lowering pressure welding mechanism. The lower opening of the heating chamber (2) is sealed by hermetically pressing the lower surface of the heating chamber (2).

The heating chamber (2) is turned off to outside air. At the same time, the crucible (3) provided on the upper part of the mold part (5) moves into the heating chamber (2).
). Then, a vacuum suction system connected to the decompression conduit αα is operated to reduce the pressure inside the heating chamber (2) to about several Torr to 10 −2 Torr depending on each casting material. Further, if necessary, a trace amount of argon gas may be discharged into this reduced pressure atmosphere to create an argon gas atmosphere. The configuration and operation up to this point are the same as the conventional device, but the main point of this invention that is particularly different in the device according to the present invention is that the crucible (3) containing the cast material 4 is housed in the heating chamber (2). be. In other words, the crucible in conventional equipment is usually formed in a convex shape using the same investment material as the mold, whereas in high-melting point metal casting, etc., the crucible is made of a non-conductive refractory material that has better fire resistance than the mold investment material. ,
Similarly, a convex mold was used, but the mold part (5) in this device is also formed in a convex shape as in the conventional method, but the crucible (
3) is characterized by being molded from conductive graphite or carbon. The graphite or carbon crucible (3) has a wall thickness (L) as thick as possible, for example, about 3n. This is because the heat capacity of the crucible (3), which is generated by induction heating, is increased while the material to be cast is not heated by induction. In addition, if there is a risk that the gas generated from the melted material such as glass may corrode the crucible (3), the inner wall of the crucible should be
The membrane (1) is shaped by applying, for example, an alumina-based coating agent. This coating agent may be used for joining directly at the boundary between the mold (4) and the crucible (3). In the forming mold section (5), all non-metals that require precision casting, including the crucible runner mix, are subjected to a high casting pressure of, for example, 3 kq/dG, using an inert gas or air pressure, regardless of their melting point. In addition, it can be cast.

Furthermore, this graphite or carbon crucible (3) has higher thermal conductivity and thermal shock resistance in induction heating of metal materials than the refractory material crucible #Y of the conventional device, and has less tendency to oxidize the cast material. -It is also well known that it is an excellent melting pot with properties such as high chemical resistance.

Therefore, although the apparatus of the present invention is intended for casting non-metallic materials, it is also capable of casting metal materials with casting performance equal to or better than that of conventional apparatuses.

Although the embodiments of the present invention have been described above, it goes without saying that the present invention is not limited to the illustrations and descriptions. For example, the hot water path ■ of the crucible (3).

The crucible (3) and the mold (4) may be arranged with a slight distance between them by simply aligning the sprue (■) of the mold (4) with the vertical line, or the crucible and the mold may be integrally molded with graphite or carbon. Sometimes I do. Also, although not shown, the mold (4
) may be constructed such that a lower chamber is provided to interrupt the outside air, and the lower chamber is depressurized or replaced with argon gas to improve and stabilize the quality of the cast body.

(6) Effects Since this invention is constructed as described above, the recently developed dental i! ! This eliminates the drawbacks and problems of glass/ceramic casting machines for 'fill materials and conventional high-frequency precision casting equipment. In other words, the crucible in the mold part of conventional high-frequency precision casting equipment is a graphite or carbon crucible,
By generating heat by induction heating and melting the non-metallic material in the crucible, by the same operation as casting metal materials in conventional high-frequency precision casting equipment, by using a reduced pressure atmosphere or an inert gaseous atmosphere. Since the crucible can be heated and melted and poured under high casting pressure, it is not only possible to produce high-quality cast products not only for glass and ceramic materials used in dental prosthetics, but also for all non-metals that require casting. It also exhibits excellent properties in melting metal materials, and therefore provides an inexpensive device that is easy to operate and can efficiently produce cast products, regardless of whether they are non-metals or metals.

[Brief explanation of drawings]

The figure is a vertical partial cross-sectional view of the casting part of the high-frequency precision casting apparatus according to the present invention. (1)...Casting section (2)...Heating chamber (3)
... Crucible (4) ... Mold (5) ... Mold part (6) ... Fireproof cylindrical body (8) ... High frequency induction heating coil αα ... Decompression hole αl) ...・Pressure hole
αJ...-Vinuton α9 of the casting lifting/lowering pressure welding mechanism...Mold table ■...Mold cavity G...Cast material■・
・・Fire-resistant coating

Claims (1)

[Claims] 1. A heating chamber having a high-frequency induction coil wound around its outer periphery, and provided with means for reducing the pressure in the internal space and pressurizing it with inert gas, etc., and having an open bottom, and a lower portion of the heating chamber. A heating chamber opening is supported by a crucible that is accommodated in a crucible, a mold section that is disposed below the crucible, and a mold that has a hollow inside, and a mold stand on which the mold section is placed, and that the opening of the heating chamber is opened by the placed mold. Equipped with a mold elevating and lowering pressure welding mechanism that seals and pressurizes the heating chamber to make it airtight from the outside air, the mold is poured into the mold cavity by pressurizing the upper surface of the melted casting material in the crucible with inert gas or air during casting. A high-frequency precision casting apparatus characterized in that the crucible is made of graphite or carbon, and the crucible is heated by induction heating to melt the material to be cast in the crucible. 2. The high frequency precision casting apparatus according to claim 1, wherein the crucible of the mold portion and the mold are integrally formed. 3. The high-frequency precision casting apparatus according to claim 1 or 2, wherein a refractory coating is formed on the wall surface of the crucible.