JPS6137027B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a method and apparatus for precisely casting metal accessories, crafts, dentures, industrial accessories, etc., and can even cast thin and wide parts as well as thin and long parts. The purpose is to be able to cast accurately and beautifully, and to automatically perform precision casting using simple equipment and operations.

In precision casting, particularly severe requirements are placed on the casting temperature and casting timing of the molten material. In other words, the appropriate temperature range for casting molten material is narrow, and if it exceeds this range, it will overheat, causing oxidation, nitrogen, rough skin, bubbles, etc. Conversely, if it is below that range, the water will not flow properly due to insufficient heating. , it does not flow sufficiently into thin and wide shapes or thin and long shapes.

Furthermore, if the flow of the molten material into the mold is interrupted or the flow rate is slow, the molten material begins to solidify during the flow and cannot be cast into the correct shape. On the other hand, if the flow rate is too high, the inside of the casting will solidify at the end, causing deformation and sink marks due to shrinkage of that part.

In the past, it was determined visually whether or not the material had been melted and then heated to the appropriate temperature range for casting, which resulted in many mistakes even when practiced by experts. Moreover, since the molten material is poured from the crucible into the mold by inverting or revolving the crucible, at the beginning of pouring, some of the molten material may run ahead and be interrupted, or the flow rate may be slow. Therefore, the above-mentioned problems could not be solved, and thin and wide parts or thin and long parts could not be accurately and beautifully cast.

The purpose of the present invention is to solve the above-mentioned problems and to make it possible to accurately and beautifully precision cast every corner of a part of any shape, and for this purpose,
When the material is completely melted and heated to the appropriate temperature for casting, the entire molten material is automatically poured from the crucible into the mold all at once, and the material is already in the mold before melting begins. The purpose is to continue to protect from oxidation and nitridation in an inert gas atmosphere from beginning to end until after completion, and to continue to suppress boiling of the dissolved material by the gas pressure of the inert gas atmosphere.

EMBODIMENT OF THE INVENTION Hereinafter, an example of the precision casting apparatus used for carrying out the precision casting method of this invention is demonstrated based on drawing.

In the figure, reference numeral 1 denotes a hermetically formed melting chamber, and a hermetically formed casting chamber 2 is disposed below the melting chamber. The melting chamber 1 is formed in a closed melting case 3, and an operation port 4 opened on the side surface of the melting chamber 1 is hermetically closed with a lid 5. The casting chamber 2 is formed in a casting case 6 with an open top, and is connected to a connecting bolt 7.
The casting case 6 is pressed against the melting case 3 by the height adjusting nut 8 and the swing type locking arm 9, and the casting chamber 2 is kept hermetically sealed by the seal ring 10. When the locking arm 9 is rotated horizontally and removed from the nut 8, the casting case 6 can be removed from the melting case 3 and the upper surface of the casting chamber 2 can be opened. A seat plate 11 is integrally formed in the center of the bottom wall of the melting case 3,
A casting hole 12 is made in the center of the seat plate 11.

A crucible 13 is placed on a seat plate 11 in the melting chamber 1, and a mold 14 is placed under the seat plate 11 in the casting chamber 2 and is hermetically sealed with an annular seal 15. Mold 1
4 is supported by the cast case 6 via a pedestal 16 and a height adjustment bolt 17. The crucible 13 is made of copper or copper alloy and is formed into a disc shape, with a chamber 18 in the center thereof.
It is formed into a bowl shape, and has a molten material passing hole 19 at its bottom, and a flat material receiving surface 20 is formed on the upper surface of the peripheral wall of the molten material passing hole 19.

The mold 14 is for a denture, and a shape 21 made of gypsum and sand is formed in an iron cylindrical frame 20, and a sprue 22 and a modeling cavity 23 are formed in the shape 21. The sprue 22 of the mold 14 is the casting hole 1 of the seat plate 11.
2 to communicate with the molten material passage hole 19 of the crucible 13, whereby the melting chamber 1 and the casting chamber 2 are connected to the crucible chamber 18, the molten material passage hole 19, the casting hole 12, the sprue 22, the shaping cavity 23, Gas vent path formed between particles of material 18 and pedestal 16
They are communicated in order through gas vent grooves 16a carved on the upper surface of the .

A pressurized inert gas inlet 25 is provided at one side of the upper surface of the melting chamber 1, and this inert gas inlet 25 is connected to a container 27 for argon gas, which is a type of inert gas, via a flow rate control valve 26. A vacuum port 28 is opened at the bottom of one side of the melting chamber 1.
is connected to a vacuum pump 30 via a check valve 29. An inert gas discharge port 31 is provided on one side of the upper surface of the casting chamber 14, and this discharge port 31 can be switched to an atmosphere discharge port 34 and a vacuum pump 30 by a switching valve 33 via a throttle adjustment valve 32. Connected.

A single cylindrical material 35 is placed upright on the material receiving surface 20 formed at the bottom of the chamber 18 of the crucible 13, and the molten material passage hole 1 is placed at the bottom 35a of the material 35.
9 is almost covered. In the melting chamber 1, a tungsten arc discharge electrode 36 is placed above the material 35 at an appropriate distance, and a DC voltage or an AC voltage is supplied from a power source 37 between the arc discharge electrode 36 and the material 35 using a voltage regulator. 38, a booster 39, a melting case 3, and a crucible 13. The arc discharge electrode 36 is connected to the height adjustment screw 4
It is fixed to the melting case 3 so that the height can be adjusted at 0. The height of the arc discharge electrode 36 and the voltage regulator 3
The arc discharge voltage adjusted in step 8 is set as follows. That is, as shown in FIG. 4C, the distance A between the arc discharge electrode 36 and the material 35 at the time when the material 35 is sufficiently melted and heated by the arc discharge 41 and melts down is defined as the arc discharge limit. The value is set so that the arc discharge 41 is interrupted and stopped at this arc discharge limit value A.
51 is a peephole.

Next, an example of the procedure for carrying out the precision casting method of the present invention will be explained using the precision casting apparatus having the above configuration.

This precision casting method consists of an inert atmosphere formation step,
The process consists of an atmospheric pressure forming process, a material melting process, and a casting process.

In the inert atmosphere forming step, in order to prevent oxidation and nitridation of the material 35, the melting chamber 1 and the casting chamber 2 are made into an inert atmosphere. That is, when the switching valve 33 is switched to the vacuum pump side and the vacuum pump 30 is operated, the melting chamber 1 is evacuated through the check valve 29, and the casting chamber 2 and the melting chamber 1 are evacuated through the switching valve 33 and the throttle control valve 32. The inside of the mold 14 is evacuated. When a sufficient vacuum is created, close the switching valve 33,
Stop the vacuum pump 30.

Next, the flow rate control valve 26 is opened and argon gas is injected into the dissolution chamber 1 from the argon gas container 27. Then, argon gas flows from the melting chamber 1 into the gap between the material 35 and the material receiving surface 20 of the crucible 13, the gap between the crucible 13 and the seat plate 11, the casting hole 12, the sprue 22, the shaping cavity 23, and the particles in the profile 21. The gas flows into the casting chamber through the gas venting passage formed by the gap and the gas venting groove 24, and the melting chamber 1, the inside of the mold 14, and the casting chamber 2 are kept in an inert atmosphere with argon gas.

In the atmospheric pressure forming process, the melting chamber 1 and the mold 14 are heated in order to expand the temperature range suitable for casting the molten material and to optimize the casting speed of the molten material.
Pressurize the inside and casting chamber 2. That is, argon gas is continued to be injected into the melting chamber 1, and the switching valve 33 is
to the atmosphere discharge port 34 side, and adjusted the flow rate control valve 26 and throttle control valve 32 to set the melting chamber 1 to 5 atmospheres (gauge pressure, the same applies hereinafter), the casting chamber 2 to 3 atmospheres, and the differential pressure between them to 2. Maintain atmospheric pressure. In this state, argon gas continues to be injected into the melting chamber 1, flows into the mold 22 and the casting chamber 2 in the same manner as described above, and continues to be discharged into the atmosphere from the atmosphere discharge port 34 through the throttle control valve 32 and the switching valve 33. . This pressurized state continues until the casting is completed.

Next, the material melting process begins. That is, when a predetermined voltage is applied between the arc discharge electrode 36 and the material 35 to cause an arc discharge 41, the material 35 is heated by the heat of the arc discharge 41 as shown in FIGS. The melt gradually flows down from the upper end toward the bottom, and is collected in the chamber 18 of the crucible 13. At this time, since the material 35 is melted in order from the top and the amount of heat in the bottom 35a of the material 35 is absorbed and absorbed by the crucible 13, the bottom 35a of the material remains melted until the end, and the bottom 35a of the material 35 remains melted until the end.
The molten material passage hole 19 continues to be closed at point a. The boiling point of the melted material 35b is raised by the pressurizing force inside the melting chamber 1, and boiling is continued to be suppressed.

When the material 35 is completely melted from the top to the bottom and flows down into the crucible 13 as shown in FIG. 4C, the arc discharge 41 reaches the discharge limit value A and is interrupted and automatically stopped. This automatically brings the fully molten material 35b within the proper temperature range for casting. At this time, the solid bottom 35a of the material 35
The molten material passage hole 19 is unblocked, and the process automatically shifts to the casting process.

The material has a high melting point (approximately 1400-
1900°C), the crucible 13 is made of copper or copper alloy and has a bottom melting point (approximately 1100°C), but it has high thermal conductivity and quickly diffuses heat and is kept at a low temperature. 35b, the crucible 13 will not be damaged by melting.

In the casting process, the molten material 35 in the crucible 13
b is maintained within the proper temperature range, all of it passes through the molten material passage hole 19 and is cast into the modeling cavity 23 through the sprue 22.
At this time, the molten material 35b continues to be pressurized by the pressure of the melting chamber 1, and its boiling continues to be suppressed. Furthermore, while the molten material 35b tends to be cast at an abnormally high speed under the pressure of 5 atmospheres in the melting chamber 1, the casting speed is slowed down under the pressure of 3 atmospheres in the casting chamber 2, and the difference is 2 It is poured into the modeling cavity 23 at an appropriate speed using atmospheric pressure and its own weight, and the molding cavity 23
The liquid continues to be injected from the inlet while being solidified sequentially from the inner part toward the inlet. This results in
The casting formed in the modeling cavity 23 solidifies and
Since the molten material is replenished as the material shrinks due to cooling, it can be formed into the correct shape without sink marks or deformation.

As another embodiment of the precision casting method of the present invention, it is possible to modify a part of the main embodiment described above as described in the following items.

(A) The means for dissolving the material 35 is as shown in FIG. That is, the outer periphery of the material 35 is covered with a heat generating cover 50 on the crucible 13, and the heat generating cover 50 is made of a high melting point material such as carbon or tungsten, and is heated to high temperature by the arc discharge 41 generated between it and the arc discharge electrode 36. heated, radiating heat,
This radiant heat melts the material 35.

(B) The device for melting the material 35 is changed from an arc discharge heating device to a gas burner or a high frequency heating device.

(C) In the above main embodiment (A) or (B), as shown in FIG. The crucible 13 is forcibly cooled through the seat plate 11 with a refrigerant 44 such as the like.

(D) In (C) above, as shown in FIG. 7, the cooling chamber 42 is relocated inside the crucible 13, and
The inlet/outlet port 45 of No. 2 is communicated with an external refrigerant supply section and recovery section via a self-sealing joint 46 and a through hole 47 formed in the bottom wall of the melting case 3.

(E) In the above main embodiment (A), (B), (C) or (D),
The crucible 13 is manufactured from one or more materials selected from copper, copper alloy, silver, silver alloy, gold, gold alloy, aluminum, and aluminum alloy.

(F) In the above main embodiment (A), (B), (C), (D), or (E), as shown in FIG. A material heat absorption wall surface 48 is provided between the peripheral edge of the placing surface 20 and the lower peripheral edge of the container chamber 18.
is formed in the shape of a cylindrical hole, and the heat of the material bottom 35a is absorbed into the crucible 13 from this wall surface 48.

(G) Main embodiment above・(A), (B), (C), (D), (E) or (F)
As shown in FIG. 9, the chamber 18 of the crucible 13 is formed into a double-curved concave shape.

The present invention is designed to interconnect the material melting equipment, material, crucible, etc. so that the molten material passage hole at the bottom of the material is unblocked when the material is completely melted and heated to the appropriate temperature for casting. By making settings in advance in connection with , the molten material automatically passes through the passage hole in a timely manner and is cast into the mold all at once, and the material is protected from oxidation and nitridation in an inert gas atmosphere from beginning to end, from before the start of melting to after the end of casting. In addition to continuing to protect the material, the gas pressure of the inert gas atmosphere continues to suppress boiling of the dissolved material.

As a result, the entire molten material at an appropriate temperature is poured from the crucible into the mold at the right time, so the molten material does not suffer from deterioration in hot water flow due to insufficient temperature, and does not suffer from bubbles or rough skin due to overheating. There is no occurrence of molding, and even thin, wide or thin and long parts often found in personal accessories, crafts, dentures, etc., can be precisely cast into beautiful, smooth skin down to every inch.

Furthermore, since the material is maintained in an inert gas atmosphere from before melting to after completion of casting, oxidation and nitridation of the casting can be reliably prevented.

At the same time, the molten material is constantly pressurized from the melting chamber side and the casting chamber side, from before melting to after solidification after casting, which increases its boiling point and makes it difficult to pour the molten material. The appropriate temperature range has expanded to the high temperature side, and the material can be easily melted and heated within this expanded appropriate temperature range.・When heating, it is possible to increase the fluidity of the molten material without causing overheating problems, and improve the flow of the molten material during casting.This allows even very dense shapes to be cast accurately and beautifully. I can do it.

In addition, the transition from melting the material to casting is performed automatically and in a well-timed sequence by opening the molten material passage hole when the melting of the material is completed, so even people who are not familiar with precision casting technology can make mistakes. There is almost nothing to do, and the loss rate of cast products can be significantly reduced.

Furthermore, the transition from the completion of melting to the start of casting does not require any human judgment or operation.
It does not take much time to operate, and it is possible to increase the number of machines operated per worker and increase the production volume of precision castings.There is also no loss time during operation, which makes it possible to Cycles can be shortened and production speed can be increased.

Furthermore, in the present invention, pressure is applied to the casting chamber, and this becomes a back pressure, which slows down the casting speed at which the molten material flows into the modeling cavity, and prevents the casting speed from becoming too fast due to the high pressure in the melting chamber. .

In other words, if the casting speed is too fast, the force of the casting will be too strong, which will cause the casting surface to become rough and burrs to appear.In addition, the surroundings of the molten material that has been cast will begin to solidify first, and the inside will be the last to solidify. As it solidifies, sink marks and deformation occur due to solidification and shrinkage.

Therefore, in the present invention, pressure is also applied to the casting chamber, and this can be used as back pressure to adjust the force and speed of casting of the material. This makes it possible to sufficiently eliminate casting surface roughness, casting burrs, sink marks, deformation, etc.

Therefore, materials with high melting points such as nickel, nickel alloys, chromium, chromium alloys, cobalt, cobalt alloys, titanium, or titanium alloys can be used not only for industrial accessories but also for personal accessories, crafts, and dentures. The present invention has made it possible for the first time to accurately cast into a precise shape.

[Brief explanation of the drawing]

The drawings show an embodiment of the precision casting apparatus of the present invention,
Fig. 1 is a perspective view, Fig. 2 is a longitudinal front view, Fig. 3 is an exploded perspective view of main parts, Fig. 4 A to D are views from the start of melting of the material to the start of casting, and Figs. 5 to 9. 3A and 3B are longitudinal sectional front views of main parts of different embodiments, respectively. 1... Melting chamber, 2... Casting chamber, 13... Crucible, 14... Mold, 19... Molten material passage hole, 2
2... sprue, 23... throttle passage, 35... material,
35a...bottom, 35b...molten material, 36...
Melting equipment.

Claims (1)

[Claims] 1 A hermetically formed casting chamber 2 is arranged below the hermetically formed melting chamber 1, a material melting device 36 and a crucible 13 are arranged in the melting chamber 1, a mold 14 is arranged in the casting chamber 2, and the crucible 13 is A molten material passage hole 19 is formed at the bottom, and a mold 14 is inserted into the molten material passage hole 19.
The melting chamber 1 and the casting chamber are communicated with each other through the crucible 13, the molten material passage hole 19, the sprue 22 of the mold 14, the modeling cavity 23, and the gas vent passage in this order, so that the melting chamber 1 is free from pressure. The active gas source 27 is communicated via the valve 26, and the casting chamber 2 is communicated with the outside via the throttle passage 32.
The material 35 is placed on the bottom of the crucible 13, the melting material passing hole 19 is closed with the bottom 35a of the material 35, and the inert gas is injected from the pressure inert gas source 27 into the melting chamber 1, and from there the melting Material passing hole 19・
The gas flows through the sprue 22 of the mold, the molding cavity 23, the gas vent path, and the casting chamber 2 in this order, and then flows out from the throttle passage 32 to the outside. , 32 in an inert gas atmosphere, melting chamber 1 and casting chamber 2.
In addition, the melting chamber 1 is maintained at a higher pressure than the casting chamber 2, and under this condition, the melting device 36 melts the material 35, and the boiling of the melted material 35b is caused by the pressure in the melting chamber 1. When the material 35 is completely dissolved, the bottom part 35a of the material is
When the molten material passage hole 19 is unblocked by the melting chamber 1, the molten material 35b continues to suppress boiling due to the pressure in the melting chamber 1, and with that pressure passes through the material passage hole 19 and is cast from the sprue 22 into the modeling cavity 23. The molten material 35b at this time enters the modeling cavity 23.
The casting speed flowing into the molding cavity 23 is slowed down by the pressure of the casting chamber 2, and as a result, the molten material 35b is solidified in order from the deep part of the modeling cavity 23 toward the entrance, and continues to be poured from the entrance, thereby forming the molding cavity. A precision casting method that prevents sink marks from occurring in the casting formed in the cavity 23.