JPS6137028B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a method and apparatus for precision casting of metal accessories, crafts, dentures, industrial accessories, etc., and accurately casts parts of thin and wide shapes and thin and long shapes. The purpose is to be able to cast beautifully and 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; exceeding this range will cause overheating, resulting in oxidation, nitridation, rough skin, bubbles, etc., and conversely, if it is below that range, the water will not flow well due to insufficient heating. , it does not flow sufficiently into parts of 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 will begin 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 by visual inspection whether the material had been heated to the appropriate temperature range for casting after it was melted, which often led to errors even by experts. Moreover, at the beginning of the casting of the molten material, a portion of the molten material may be interrupted or the casting speed 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 present invention solves the above-mentioned problems and makes it possible to precisely and beautifully cast every corner of a part of any shape. Then, the heating of the material is automatically stopped, and the molten material heated to an appropriate temperature range is poured into the mold.

Embodiments of the precision casting apparatus of the present invention will be described below with reference to the drawings.

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 thereof 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 this 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.
A molten material passage hole 19 is formed at the bottom of the container 18, and a flat material receiving surface 20 is formed at the bottom of the chamber 18 to surround the molten material passage hole 19.

The mold 14 is for a denture, and a shape member 21 made of gypsum and sand is formed in an iron cylindrical frame 14a, and a sprue 22 and a modeling cavity 23 are formed within this shape member 21. The sprue 22 of the mold 14 is the casting hole 1 of the seat plate 11.
2 communicates 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 molding cavity 23, and the shape. Gas vent path formed between particles of material 18 and pedestal 16
It is interlocked sequentially through a gutting groove 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 provided at the bottom of one side of the melting chamber 1, and this vacuum port 2
8 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 is connected to an atmosphere discharge port 34 via a throttle adjustment valve 32 and a switching valve 33.
and the vacuum pump 30 in a switchable manner.

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 19 is substantially closed by the bottom 35a of this material 35. In the melting chamber 1, the material 35
A tungsten arc discharge electrode 36 is placed oppositely at an appropriate distance above the arc discharge electrode 3.
A DC voltage or an AC voltage is applied from a power source 37 to the melting case 3 and the material 35 through the voltage regulator 38, the booster 39, the melting case 3, and the crucible 13. The arc discharge electrode 36 is fixed to the melting case 3 so that its height can be adjusted using a height adjustment screw 40. The height of the arc discharge electrode 36 and the arc discharge voltage adjusted by the voltage regulator 38 are 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 control valve 26 is opened and argon gas is injected into the dissolution chamber 1 from the argon container 27.
Then, argon gas flows from the melting chamber 1 to the material 35.
The gap between the crucible 13 and the material receiving surface 20, the gap between the crucible 13 and the seat plate 11, the casting hole 12, and the sprue 2.
2. It flows into the casting chamber 2 through the molding cavity 23, the gas vent path consisting of the particle gaps of the shape material 21, and the gas vent groove 24, and the melting chamber 1, the inside of the mold 14, and the casting chamber 2 are filled with an inert atmosphere of argon gas. is maintained.

In the atmospheric pressure forming process, the melting chamber 1 and 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.
The inside and casting chamber 2 are pressurized. 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 atm (gauge pressure, the same applies hereinafter), the casting chamber 2 to 3 atm, 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 14 and into 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 via 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 voltage of a predetermined value 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 fourth A to D. 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 by the crucible 13, the bottom 35a of the material remains melted until the end, and the bottom 35a of the material 35a has a molten material passage hole. 19 continues to be blocked. 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 low 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 molding 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 molding cavity 23 at a speed appropriate for the atmospheric pressure and self-weight, and the molding cavity 2
The liquid continues to be injected from the inlet while being solidified sequentially from the inner part of the tube toward the inlet. As a result, the casting formed in the molding cavity 23 is replenished with molten material as it shrinks due to solidification and cooling, so that it can be formed into the correct shape without sink marks or deformation.

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

(A) The crucible 13 is made of silver, silver alloy, gold, gold alloy, aluminum, and aluminum alloy. Or, it is made from two or more of these metal materials plus copper and copper alloy.

(B) The crucible 13 is made of carbon whose melting point is higher than the temperature at which the arc discharge 41 occurs.
Even if you stay in Crucible 13 for a relatively long time,
To prevent the crucible 13 from being damaged by melting.

(C) In the above-mentioned main embodiment (A) or (B), as shown in FIG. Alternatively, the crucible 13 is forcibly cooled via the seat plate 11 using a refrigerant 44 such as oil.

(D) In (C) above, as shown in FIG. 6, the cooling chamber 42 is relocated inside the crucible 13, and
The refrigerant inlet/outlet 45 is communicated with an external refrigerant supply source and a refrigerant 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), as shown in FIG. By forming a material heat absorption wall surface 48 between the lower peripheral edge of the container chamber 18, bringing the peripheral surface of the bottom portion 35a of the material 35 into contact with this wall surface 48, and selecting the height h of the wall surface 48 as appropriate, the material The rate of heat absorption from the bottom 35a to the crucible 13 can be set as desired so that the material 35 can be melted automatically into the correct temperature range for the type of casting.

(F) In the above main embodiments ・(A), (B), (C), (D), or (E), as shown in FIG. 8 or 9, the material placement surface of the crucible 13 20 (and the material heat-absorbing wall surface 48), the inner surface of the chamber 18 is made of heat-resistant material.
A protective layer 49 having both heat insulation and insulation properties is formed. This prevents overcooling of the molten material 35b, prevents the material forming the crucible 13 from being absorbed into the molten material 35b and altering the quality of the molten material 35b, and also prevents the arc discharge 41 from flowing into the crucible 13. It also prevents melting and damage.

(G) Main embodiments of the above - (A), (B), (C), (D), (E) or (F)
)
In this step, as shown in FIG. 10 A, B, C, or D, the material 35 is shaped into a conical shape, a truncated conical shape, or a shape similar to this. In this case, it is preferable that the conical taper θ of the material be the maximum taper or a taper close to this that can gradually expand as the arc discharge 41 becomes longer. As a result, the amount of melting, that is, the amount of casting, can be increased by the amount that the material 35 is expanded into a tapered shape, and the melting can be performed evenly, efficiently, and quickly.

As explained above, in the first invention, the material is gradually melted from the top to the bottom by arc discharge, and when the material is completely melted and reaches the temperature range suitable for casting, the arc discharge is stopped. Since the discharge limit value is reached and the discharge is interrupted and automatically stopped, the material is automatically and accurately melted and heated within the appropriate temperature range for casting, and the molten material that has reached this appropriate temperature range is placed directly into the mold at the right time. The material can be cast in a large amount of water, and if insufficient heating does not cause poor water flow, overheating will not cause the material to boil and cause bubbles or rough skin.

In addition, a hole for passing the molten material is made at the bottom of the crucible.
A material placed on the bottom of the crucible covers the molten material passage hole, and when the material is completely melted and heated to an appropriate temperature, the molten material passage hole opens due to the melting of the bottom of the material. If an embodiment is adopted in which the molten material in the crucible is automatically cast in a mass through the molten material passage hole and into the mold in a timely manner, It is never too late or too late.

Therefore, since the molten material at an appropriate temperature is cast into the mold at the right time, the molten material has good circulation and does not generate bubbles or rough skin due to overheating. This makes it possible to precisely cast every inch of thin, wide or thin and long parts that are often found in personal accessories, crafts, dentures, etc. into beautiful, smooth skin.

In addition, after pressing the start button to generate arc discharge, the process from melting to completion of heating is performed automatically and continuously, allowing visual judgment of whether the material has been heated to the appropriate temperature after melting, stopping the arc discharge, etc. All the operations associated with these can be omitted.

Furthermore, in the case of the embodiment described above, the casting start operation can also be omitted.

This makes it possible to extremely easily heat the molten material to within the appropriate temperature range with just one push of a button to start the precision casting process. It is possible to significantly increase the production amount of products.

Moreover, from the start of melting to the completion of melting and heating,
In addition to this, in the case of the embodiment described above, the transitions from each stage until the completion of casting are all carried out automatically and in succession in a well-timed manner, so even those who are not familiar with precision casting technology are unlikely to make mistakes. Therefore, the loss rate of the cast product can be almost eliminated.

Furthermore, since there is no operating time or loss time associated with the transition between each stage of casting, precision casting can be completed in a shorter time and production efficiency can be increased.

The second invention improves the first invention and protects the material in an inert gas atmosphere continuously from before the start of melting to after the completion of casting, thereby preventing the material from being nitrided or oxidized by air. It can be eliminated.

In addition, since the material is continuously pressurized with atmospheric gas from before the start of melting to after the completion of casting, the boiling point of the molten material is raised and the appropriate temperature range for casting the molten material is expanded to the high temperature side. Materials can be easily melted and heated within this expanded appropriate temperature range, and when melting and heating materials in the newly expanded high-temperature side of the appropriate temperature range, overheating problems can occur. It is possible to increase the fluidity of the molten material and improve the flow of the molten material during casting without causing any problems.This allows even extremely dense shapes to be cast accurately and beautifully.

In addition, if the material melted in the crucible is blown into the mold under the high pressure of the atmosphere in the melting chamber, the force of the pouring will be too strong, causing the casting surface to become rough and burrs to appear. The casting speed was also too fast and the cast material gradually solidified from the periphery towards the center.
The solidification and shrinkage causes sink marks and deformation.

To deal with this, the third invention further improves the second invention by applying pressure to the casting chamber and using this as back pressure to slow down the momentum and casting speed of the material, It can be adjusted to the appropriate momentum and speed. This makes it possible to sufficiently eliminate casting surface roughness, casting burrs, sink marks, deformation, etc.

Therefore, even materials with high melting points such as nickel, nickel alloys, chromium, chromium alloys, titanium, and titanium alloys can be cast correctly into precise shapes, such as industrial accessories, personal accessories, crafts, and dentures. The present invention has made it possible for the first time to do so.

[Brief explanation of the drawing]

The drawings show an embodiment of the precision casting apparatus of the present invention,
Figure 1 is a perspective view, Figure 2 is a longitudinal front view, Figure 3 is a partially exploded perspective view of essential parts, Figures 4 A to D are process diagrams from the start of melting to the start of casting, and Figure 5. 9 to 9 are longitudinal sectional front views of essential parts showing improved examples of the main embodiment, and FIGS. 10 A to 10 D are front views of modified examples of materials. 1... Melting chamber, 2... Casting chamber, 13... Crucible, 14... Mold, 19... Molten material passage hole, 2
2... Sprue, 23... Modeling cavity, 26... Valve, 2
7...Inert gas source, 32... Throttle passage, 35...
...Material, 35a...bottom, 35b...molten material,
36... Arc discharge electrode, 41... Arc discharge,
A... Arc discharge limit value.

Claims (1)

[Claims] 1. A material 35 is placed in a crucible 13, an arc discharge electrode 36 is placed above the material 35 at an appropriate distance, and a voltage is applied across the arc discharge electrode 36 and the material 35 to create an arc. A discharge 41 is caused, and the heat of this arc discharge 41 melts the material 35 from the top and is received by the crucible 13 that flows down.
The distance A between the arc discharge electrode 36 and the material 35 when the material 35 melts and flows down from the top to the bottom is set as the arc discharge limit value, and at this point the arc discharge 41 is interrupted and automatically stopped. A precision casting method characterized in that, as a result, the material 35 is completely melted, the temperature of the molten material 35b automatically enters a temperature range suitable for casting, and the molten material 35b is cast into the mold 14. . 2. In the precision casting method described in claim 1, a mold 14 is arranged below the crucible 13, a molten material passage hole 19 is formed in the bottom of the crucible 13, and a sprue of the mold 14 is formed in the molten material passage 19. 22 in communication, place a material 35 on the bottom of the crucible, and close the molten material passage hole 19 with the bottom 35a of the material 35.
In this state, the material 35 is melted by the arc discharge 41, and the material 35 is completely melted, the temperature of the molten material 35b automatically enters the temperature range suitable for casting, and the solid bottom 35a of the material 35 is melted. The molten material passage hole 19 is unblocked, and the entire molten material 35b passes through the molten material passage hole 19 and is cast as one into the mold 14 from the sprue 22.
Precision casting method. 3 Place the mold 14 under the melting chamber 1 which is formed in a hermetically sealed manner, place the crucible 13 in the melting chamber 1, make a molten material passage hole 19 at the bottom of the crucible 13, and insert the mold 14 into the molten material passage 19. The melting chamber 1 and the space outside the mold 14 are connected to the crucible 1 by communicating the sprue 22.
3. Molten material passage hole 19, mold 14 sprue 22.
The molding cavity 23 and the degassing passage are connected in series, the melting chamber 1 is connected to the inert gas source 27 via the valve 26, and the material 35 is placed on the bottom of the crucible.
The bottom 35a of the material 35 closes the molten material passage hole 19, an arc discharge electrode 36 is placed above the material 35 at an appropriate distance, and an inert gas is supplied from an inert gas source 27 to the melting chamber 1, crucible 13, and melting chamber 1. Material passing hole 1
9, the mold sprue 22, the mold molding cavity 23, the mold gas vent passage, and the casting chamber 2 in order, and flow out from the throttle passage 32 to the outside, thereby causing each of the above gas flow path portions 1, 13, 19, 22 , 23 and 2 in an inert gas atmosphere, the melting chamber 1 is kept in a pressurized state, and under this condition, a voltage is applied across the arc discharge electrode 36 and the material 35 to cause arc discharge 41. The heat of this arc discharge 41 melts the material 35 in order from the top and is received by the falling crucible 13, until the material bottom 35a is finally melted, the molten material passage hole 19 is closed with the material bottom 35a. The distance between the arc discharge electrode 36 and the material 35 when the boiling of the melted material 35b is suppressed by the pressure inside the melting chamber 1, and the material 35 melts sufficiently from the top to the bottom and flows down. A is set to the arc discharge limit value, and the arc discharge 41 is interrupted and automatically stopped, thereby melting even the bottom portion 35a of the material 35 that remains unmelted, and ensuring that the temperature of the molten material 35b is at an appropriate level. automatically enters the temperature range,
At this time, the molten material passing hole 19 is unblocked by the solid bottom 35a of the material 35, and the molten material 35b
A precision casting method in which molten material passes through a molten material passage hole 19 and is cast into a molding cavity 23 from a sprue 22. 4 A hermetically formed casting chamber 2 is arranged below the hermetically formed melting chamber 1, and a pouring chamber 13 is placed in the melting chamber 1.
The molds 14 are respectively arranged in the casting chamber 2, a molten material passage hole 19 is formed in the bottom of the crucible 13, and the sprue 22 of the mold 14 is communicated with the molten material passage 19, thereby connecting the melting chamber 1 and the casting chamber 2. The crucible 13, the molten material passage hole 19, the sprue 22 of the mold 14, the molding cavity 23, and the degassing passage are connected in series, and the melting chamber 1 is connected to the inert gas source 27 via the valve 26, and the casting chamber is communicated with the outside via a throttle passage 32, a material 35 is placed on the bottom of the crucible, and a molten material passage hole 19 is opened at the bottom 35a of the material 35.
The arc discharge electrode 36 is placed above the material 35 at an appropriate distance, and inert gas is supplied from the source 27 to the melting chamber 1, the crucible 13, the molten material passage hole 19, the mold sprue 22, and the mold. The gas flows into the molding cavity 23, the mold gas vent passage, and the casting chamber 2 in order, and then flows out from the throttle passage 32, thereby causing each of the above gas flow path portions 1, 13, 19, 22, 2
3 and 2 in an inert gas atmosphere, the melting chamber 1 and the casting chamber 2 are kept in a pressurized state, and the melting chamber 1 is kept at a higher pressure than the casting chamber 2. Under this condition, the arc discharge electrode 36 and applying a voltage across the material 35 to cause arc discharge 41;
The heat of this arc discharge 41 melts the material 35 sequentially from the top and is received by the falling crucible 13, and the molten material passage hole 19 continues to be closed by the material bottom 35a until the material bottom 35a is melted last. At the same time, boiling of the melted material 35b is suppressed by the pressure in the melting chamber 1, and the distance A between the arc discharge electrode 36 and the material 35 when the material 35 melts sufficiently from the top to the bottom and flows down. is set to the arc discharge limit value, and the arc discharge 41 is interrupted and automatically stopped, thereby melting even the bottom part 35a of the material 35 that remains unmelted, and bringing the temperature of the molten material 35b to an appropriate temperature. At this time, the molten material passage hole 19 is unblocked by the solid bottom 35a of the material 35, and the molten material 35b passes through the molten material passage hole 19 and enters the molding cavity 23 from the sprue 22. At the same time as being cast, the molten material 35b enters the molding cavity 23.
The speed at which the molten material 35b flows into the molding cavity 2 is slowed down by the back pressure of the casting chamber 2, so that the molten material 35b flows into the molding cavity 2.
The molding cavity 2 is solidified sequentially from the deep part of the cavity 3 toward the entrance part, and continues to be injected from the entrance part.
3. Precision casting method that prevents sink marks from forming in the casting.