JP3141615B2 - Differential pressure casting equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a differential pressure casting apparatus for performing casting using a ceramic shell mold manufactured by a lost wax method.

[0002]

2. Description of the Related Art Relatively small castings, such as teeth and arts and crafts made of precious metals, titanium and other materials, are generally thin and have delicate patterns, and are liable to cause run-out defects during casting. Therefore, in order to improve this, the temperature of the molten metal during casting is suppressed by increasing the mold temperature or the casting temperature. However, when titanium or a titanium alloy is used as the material, it is very difficult to increase the casting temperature by heating the molten metal in actual work. In addition, due to the reactivity specific to titanium, there is a problem that as the mold temperature increases, the reaction between titanium and the mold becomes more intense, and the contamination of the cast product becomes deeper.

[0003] As another method for suppressing poor running of the molten metal,
Centrifugal casting method, reverse casting method, reverse pressure casting method, which improves the flow of molten metal by centrifugal force, suction casting method, in which the cavity of the mold is poured while depressurizing the mold cavity, and a casting machine in which the mold chamber and melting chamber are separated. There is a method using mechanical auxiliary means such as a differential pressure casting method (suction / pressure casting method) in which the melting chamber is pressurized with argon gas while the chamber is suctioned and depressurized, and cast.

[0004] These methods have both advantages and disadvantages, and are properly used depending on the material, shape, size and the like of the cast product.

[0005] The differential pressure casting method is performed, for example, by a differential pressure casting apparatus as shown in FIG.

(1) First, a block-shaped porous mold 25 manufactured by the burial method is placed on a ring stand 26, and the crucible stand 4 and the mold 25 are connected via a packing 27 to a jack 1.
2, and mechanically tightened to seal between the crucible base 4 and the mold 25.

(2) The mold chamber 3 and the melting chamber 2 are sucked and evacuated to exhaust the air in the chambers 3 and 2.

(3) Then, while sucking the mold chamber 3, an argon gas (Ar gas) is introduced into the melting chamber 2 to provide a differential pressure (for example, a pressure difference of 10 to 20 cmHg). Thereby, the inside of the porous mold 25 is sucked.

(4) Then, an arc is generated between the ingot 6 in the crucible 7 and the electrode 8 to melt the ingot 6.

(5) When the ingot 6 is melted, the crucible 7
Is naturally dropped by its own weight from the hole at the bottom of the mold and poured into the mold 25, and its upper surface is pressurized with argon gas.

As described above, since the material of the mold 25 is poured while the inside of the porous mold 25 is sucked, there is a feature that the run of the cast product and gas defects can be improved.

[0012]

By the way, in the above differential pressure casting, it is most important that sufficient airtightness can be maintained at the contact surface between the mold and the crucible base. No strength is needed.

Therefore, the mold is usually limited to a block-shaped porous mold having a relatively high mechanical strength and manufactured by an immersion method or a ceramic molding method. In this way, the mold is limited to a block-shaped mold, for example, a ceramic ceramic manufactured by the lost wax method.
Compared to shell molds, the same casting generally has about 6-7
It requires twice as much mold material, and the thickness of the mold is also increased, which also affects air permeability during casting. In addition, a thick mold has poor thermal conductivity and thus is susceptible to thermal shock, and has a problem that the mold is easily cracked during heat treatment or casting.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a differential pressure casting apparatus capable of manufacturing a casting without using a block-shaped mold.

[0015]

According to the present invention, in order to achieve the above object, a melting chamber containing a crucible and a mold are contained.
The mold chamber is volume forming a Chuyuana the specification <br/> switching Rutotomoni crucible stand in a crucible stand the crucible is placed, down aspirated mold chamber
While pressure mold the melt in the crucible dissolution chamber pressurized
To the counter pressure casting apparatus which performs counter pressure casting by pouring, the <br/> flange on the outer peripheral edge portion of the sprue ceramic shell mold formed into a thin wall is provided, the lower portion of the flange portion with pedestal template
It is supported in a suspended state, and the mold receiving table is oriented toward the crucible table.
Selfish pressed, but the flange of the ceramic shell mold was Closing good airtight crucible stand around the Chuyuana.

[0016]

[Function] Ceramic shell mold is not used for differential pressure casting because it is relatively weak against bending stress and breaks easily. However, a flange is provided on the ceramic shell mold and this flange is attached to the mold. by attaching good airtightness crucible base by a mechanism, not applied mostly bending stress or the like in the mold itself, does not mold is split. Also,
Since the mounting of the mold is performed only by attaching the flange to the crucible base by the mold attaching mechanism, the mold can be easily attached. Therefore, it is possible to manufacture a casting by differential pressure casting using a thin ceramic shell mold without using a block-shaped mold.

[0017]

An embodiment of the present invention will be described below with reference to the accompanying drawings.

In FIG. 1, reference numeral 1 denotes a main body of a differential pressure casting apparatus, and a crucible table 4 for vertically dividing the inside into a melting chamber 2 and a mold chamber 3 is provided in the center of the main body 1. .

A pouring hole 5 is provided at the center of the crucible base 4, and an ingot 6 made of a material to be melted (a precious metal such as gold or platinum) is placed on the crucible base 4 right above the pouring hole 5. The crucible 7 is placed so as to be positioned at. Above the crucible 7, an electrode 8 made of tungsten or the like for generating an arc for melting the ingot 6 on the crucible 7 by applying a voltage.
Is provided. The melting chamber 2 is provided with a viewing window 9 for monitoring the state of the melting chamber 2 such as an arc and an ingot, and a gas port 10 for introducing and exhausting an inert gas such as Ar gas. Have been.

The mold chamber 3 has an exhaust port 11 for exhausting the inside of the chamber 3.
Is provided. Below the pouring hole 5 in the mold chamber 3,
Ring stand 1 that moves up and down in chamber 3 by jack 12
The mold receiving table 14 is placed on the ring table 13. The mold receiving base 14 is provided with a porous ceramic shell mold 15 having a flange 17 which is turned outward by about 90 ° in the radial direction at the upper end of the sprue cup 16 of the mold 15. For example, as shown in FIG. 4, it is formed in a cylindrical shape made of a metal or a refractory material divided into two in the diameter direction as shown in FIG. The mold receiving base 14 is placed on the ring base 13 such that the sprue cup 16 of the supported mold 15 is located directly below the pouring hole 5.
3 is raised by the jack 12 so that the ceramic
The flange 17 of the shell mold 15 is pressed against the lower surface of the crucible base 4 via a packing 18 made of a refractory material,
The flange 17 is mechanically fastened to the crucible base 4 so that the space therebetween is sealed. The mold receiving mechanism 19 is constituted by the mold receiving base 14, the jack 12, the ring base 13, and the like, and the flange 17 of the ceramic shell mold 15 is mounted on the crucible base 4 in an airtight manner by the mold mounting mechanism 19.

The ceramic shell mold 15 is manufactured by, for example, a lost wax method.

First, as shown in FIG. 2, a desired flanged model is made of wax or a material that can be removed and removed.
More specifically, the pouring hole 5 is formed through a runner forming section 21 for forming a runner in a product section 20 similar to a target product.
The sprue cup forming part 22 is provided so that the sprue cup 16 having substantially the same diameter as that of the sprue cup 16 is formed.
Next, a predetermined coating is applied thereto by a lost wax method, which is then dewaxed and fired to produce a thin ceramic shell mold 15 having a flange 17 as shown in FIG.

In this case, the flange 17 of the mold is manufactured separately by, for example, separately using a refractory material or the like, and the ceramic shell mold without the flange 17 is joined, or the fire-resistant flange is formed into a wax type. Built-in ceramic
Shell molds can also be made. However, such a method causes cracks due to the difference in the coefficient of thermal expansion between the flange and the ceramic shell mold, and is considerably expensive, so that the flange is manufactured simultaneously with the ceramic shell mold and made of the same material. It is best to have the same thickness.

Next, as shown in FIG. 4, a ceramic shell mold 15 at a predetermined temperature is
The mold 15 is supported so as to be suspended at the seven portions. At this time, the diameter of the flange 17 can be reduced by dividing the mold receiving base 14 into two parts.
Even a hot ceramic shell mold 15 can be set quickly.

Then, the ceramic shell mold 15 placed on the mold receiving stand 14 is inserted into the mold chamber 3 of the differential pressure casting apparatus as shown in FIG. With the mold 15 suspended, the flange 17
And the crucible base 4 are mechanically fastened with the jack 12 via the fire-resistant packing 18.

[0026] As a result, the ceramic shell mold 15 was produced in the most widespread lost wax process as a precision casting mold, seal good, yet of corruption late
It can be easily fastened to a differential pressure casting device.

That is, the ceramic shell mold 15
Is relatively weak against bending stress and easily cracks, and easily cracks even if the entire mold 15 is tightened.
For example, if the ceramic shell mold 15 is placed on the ring base 13 and fastened with the jack 12 without using the mold receiving base 14, the ceramic shell mold 15 is easily broken. However, the ceramic shell mold 15 has the property of considerably resisting local compressive stress,
Provided a flange 17 to take advantage of this to the upper end of the sprue cup 16 is pressed against only the flange 17 on the crucible base 4 via the gasket 18. Thus, since only the local mold 15 in contact with the packing 18 of the flange 17 is under compressive stress, it is hardly flanges 17 and ceramic shell mold 15 is split by a fastening, the fastening portion airtightly The property is practically sufficient.

The ceramic shell mold 15 is supported by the mold receiving base 14 in a suspended state, and the molten metal is poured in this state. rarely it is corrupted by pouring if the ceramic shell mold 15 having an intensity. If the ceramic shell mold can withstand ordinary pouring, there is no particular problem when the ceramic shell mold that can be used in such an apparatus is cast while suspended because the size of the ceramic shell mold can be relatively small.

Next, a case where a cast product is specifically manufactured using the above differential pressure casting apparatus will be described.

[Specific Example 1] First, a wax mold (12 g) as shown in FIG. 2 was manufactured by the lost wax method, and 12 wax molds were assembled into one tree. This was coated with a titanium casting by the method for manufacturing a precision casting mold disclosed in Japanese Patent Application Laid-Open No. 64-11049, dewaxed, and the tree was decomposed into 12 molds. After firing for a time, a ceramic shell mold as shown in FIG. 3 was produced.

The produced ceramic shell mold is heated at 800 ° C.
Preheating for 1 hour, and this is supported by the mold receiving base 14,
This was placed on the ring base 13 and the crucible base 4 and the mold (flange) were mechanically tightened with the jack 12 via the packing 18.

Next, the mold chamber 3 and the melting chamber 2 are suctioned and depressurized by a vacuum pump to discharge the air in each of the chambers 3 and 2.
Argon gas having an original pressure of 1 kg / cm ² was introduced into the melting chamber 2 through a gas port 10.
Introduced from. At this time, the pressure in the mold chamber 3 is -10 to -20.
In cmHg, whereas the pressure in the melting chamber 2 was 0.6 ~0.8Kg / cm ^2. That is, the pressure difference (differential pressure) between the mold chamber 3 and the melting chamber 2
It was confirmed that the airtightness of the contact portion between the flange of the ceramic shell mold and the packing 18 was sufficiently maintained.

Subsequently, the electrode 8 of the melting chamber 2 and 70 g of Ti-6Al
An arc was blown between the -4V ingots 6 to melt the ingots 6 and cast. In this case, the pressure difference between the mold chamber 3 and the melting chamber 2 hardly changed through melting and pouring of the ingot 6.

No cracks or other damages were found in the ceramic shell mold and flange after casting. When the ceramic shell mold was destroyed and the casting was visually inspected, the run of the thin-walled portion was perfect, there were no pinholes or other gas defects on the surface of the casting, and burrs caused by cracks in the ceramic shell mold. Good products without defects were obtained.

[Specific Example 2] Casting was performed in the same manner as in Specific Example 1 except that the other ceramic shell mold produced in Specific Example 1 was preheated at 100 ° C for 1 hour.

No crack or other damage was found in the ceramic shell mold and flange after casting. When the ceramic shell mold was broken and the casting was visually inspected, the run of the thin wall was perfect, there were no pinholes or other gas defects on the surface of the casting, and burrs caused by cracks in the ceramic shell mold. Good products without defects were obtained.

In general, the hot strength of the ceramic shell mold is weak at 800 ° C. and 100 ° C.
It has been confirmed that a ceramic shell mold at a temperature of ℃ can be sufficiently used. This has the advantage that the lower the mold temperature, the shallower the contamination on the surface of the casting, especially in titanium and titanium alloy castings.

[Specific Example 3] A ceramic shell mold was manufactured by the method for manufacturing a precision casting mold disclosed in Japanese Patent Application No. 4-82407.
Casting was carried out in the same manner as in Example 1 except for preheating for a time.

No crack or other damage was found in the cast ceramic shell mold and flange. When the ceramic shell mold was broken and the casting was visually inspected, the run of the thin wall was perfect, there were no pinholes or other gas defects on the surface of the casting, and burrs caused by cracks in the ceramic shell mold. Good products without defects were obtained.

Comparative Example 1 The other ceramic shell mold produced in Example 1 was preheated at 200 ° C. for 1 hour, and was placed directly on the ring table 13 shown in FIG. 1 without using the mold receiving table. The chamber 3 and the dissolution chamber 2 were suctioned and depressurized to discharge air.
Then, argon gas was introduced in the original pressure 1Kg / cm ² in the melting chamber 2. In this case, there was no pressure difference because the mold chamber 3 and the dissolution chamber 2 were in communication, and the pressure in the chamber was 0.1 to 0.2 kg / cm ² .
In this state, 70 g of an ingot of Ti-6Al-4V was melted and cast.

No crack or other damage was observed in the ceramic shell mold after casting, and there was no particular problem.
When the casting was destroyed and the casting was visually inspected, poor running was found in the thin portion and gas defects such as pinholes were present, and a satisfactory casting was not obtained.

Therefore, by performing casting using the differential pressure casting apparatus according to the present invention, a non-defective casting having no pinholes or other gas defects on its surface and having no defects such as burrs can be obtained. In particular, the differential pressure casting apparatus according to the present invention can obtain a thin cast product having almost no gas defects even when precision casting a metal having a poor melt flow such as titanium or a titanium alloy. It is suitable for precision casting of titanium alloys and other castings that are prone to run-off defects and pinholes and other castings that are prone to gas defects.

[0043]

As apparent from the above description, according to the present invention, an excellent effect that a cast product can be produced using a thin ceramic shell mold without using a block mold is exhibited.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an example of a differential pressure casting apparatus according to the present invention.

FIG. 2 is a cross-sectional view showing an example of a wax mold for producing the ceramic shell mold of the present invention.

FIG. 3 is a sectional view showing an example of the ceramic shell mold of the present invention.

FIG. 4 is a view showing a state in which the ceramic shell mold of the present invention is supported on a mold receiving stand, (a) is a sectional view,
(B) is a top view.

FIG. 5 is a sectional view showing an example of a conventional differential pressure casting apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Apparatus main body 2 Melting chamber 3 Mold chamber 4 Crucible table 5 Pouring hole 6 Ingot 15 Ceramic shell mold 17 Flange 19 Mold attachment mechanism

──────────────────────────────────────────────────の Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B22D 18/04 B22C 9/04 B22D 18/06

Claims (1)

(57) [Claims] 1. A melting chamber containing a crucible and a mold
Partition in a crucible stand the mold chamber the crucible is mounted to be
At the same time , a pouring hole is formed in the crucible base , the mold chamber is suctioned and depressurized , and the melting chamber is pressurized to melt the molten metal in the crucible into the mold.
In counter pressure casting apparatus which performs counter pressure casting by pouring, the full <br/> flange provided at the bottom of the flange portion with pedestal mold the outer peripheral end portion of the sprue ceramic shell mold formed into a thin wall Hanging
The mold receiving table toward the crucible table.
And press the flange of the ceramic shell mold
Counter pressure casting apparatus characterized by the Closing good airtight crucible stand around Chuyuana.