KR101367200B1 - Process for duplex casting and process for duplex casting apparatus thereof - Google Patents

Abstract

The present invention relates to a double casting device and a double casting method. The double casting device comprises: a casting chamber having an internal space part; an injection pipe mounted on the bottom of the casting chamber to inject molten metal; a mold connected to the injection pipe to be detached and attached and having a cavity; a charging medium charged between the inner surface of the casting chamber and the mold; a pressure control unit positioned in the upper part of the casting chamber and decompressing the internal space of the casting chamber; and a riser communicating with the upper part of the cavity of the mold to receive the molten metal and to discharge the molten metal by the gravity.

Description

PROCESS FOR DUPLEX CASTING AND PROCESS FOR DUPLEX CASTING APPARATUS THEREOF

The present invention relates to a double casting method and apparatus. More specifically, the present invention may be applied to the mold with reduced pressure casting and gravity casting, to remove the pores and bubbles in the product to prevent casting defects and to solve the unformed problem can easily produce high heat-resistant cast steel products A casting method and apparatus.

The commonly used metal mold casting method is one of the most fundamental techniques of metal forming, and is used to manufacture large quantities of the same type of product. The casting method is prepared by putting scrap, pig iron, ferroalloy, or nonferrous metal raw material into a furnace, heating and melting, pouring into a mold of sand or metal, cooling and solidifying. It is a principle that the molten metal is molded into a mold made of a desired model and then molded, and then the molten metal hardens to be the same metal object as the model. Casting can produce products in large quantities once the mold design is complete, but casting defects frequently involve undesired non-metallic components (inclusions) as part of the product in the final product. . In addition, molten metal injected and dissolved in the atmosphere dissolves and absorbs a large amount of gases such as hydrogen, oxygen, and nitrogen. As the solubility decreases during coagulation, bubbles are generated, and some unresolved gases remain to prevent surface defects. It is also generated.

In order to prevent such defects, a method of casting using a vacuum technique is called a vacuum (decompression) casting method. Such vacuum casting may be used in a manner in which melting is carried out in the air and then cast under vacuum conditions, or when the molten melt is received in a ladle in a ladle, and then vacuumed or cast in air.

When the vacuum casting method is used, harmful gas components can be easily removed, and the mechanical properties of the product are excellent, and thus the casting method is used to manufacture products such as stainless steel, heat resistant steel, tool steel, bearing steel, and magnetic materials.

Countergravity vacuum assisted casting, one of the vacuum casting methods, was developed in the 1970s and 1980s by Hitchiner, Inc. in the United States, which infiltrates a ceramic tube into a molten metal and vacuums it. (Vacuum System) quickly inhales the molten metal into the mold. Patents relating to representative anti-gravity vacuum castings and vacuum casting apparatuses are US Pat. Nos. 0477948 and 0080518. However, Hitchiner's casting method described in the registered patent is limited to the production of precision casting products by ceramic mold, and in particular, the production of sand mold casting methods does not withstand the death of molds due to rapid suction of molten metal. It has serious problems such as a large amount of casting defects such as mixing. In addition, this technique uses a vacuum pressure to inject molten metal into the mold to make the product. In addition to the small porosity inside the product due to the rapid flow of the melt, in some cases, insects Worm holes such as holes are created and some product surfaces have large amounts of non-fill casting defects.

Due to these problems, Hitchiner's anti-gravity vacuum casting technology has not been commercialized in the sand casting products, and other companies around the world have succeeded in the development of anti-gravity vacuum casting technology using suction pipes applied to the sand casting products. There is no mass production example.

Accordingly, the present inventors have repeatedly studied casting methods to overcome the above-mentioned problems and remove the sand molds and vacuum pressures instead of the ceramic precision casting molds, and double casting for recharging molten metal which has not been solidified by gravity by gravity. The present invention was completed by producing high temperature heat resistant stainless steel products by applying technology.

It is an object of the present invention to provide a duplex casting method which can prevent shrinkage defects, bubble defects and other casting defects during product casting.

Another object of the present invention to provide a duplex casting method that can easily remove the inclusions contained in the molten metal.

Still another object of the present invention is to provide a duplex casting method capable of producing a product having a high precision and a complicated shape.

Still another object of the present invention is to provide a duplex casting method which can have cost reduction and productivity increase effects.

Yet another object of the present invention is to provide a duplex casting apparatus.

One aspect of the invention relates to a duplex casting apparatus. The duplex casting device includes a casting chamber having a space portion therein; An injection tube mounted below the casting chamber and into which molten metal is injected; A mold that is detachably connected to the injection tube and has a cavity; A filling medium filled in the casting chamber and between the mold; Pressure adjusting means positioned above the casting chamber to reduce the pressure inside the casting chamber; And a riser configured to receive the molten metal through the upper portion of the cavity inside the mold and to discharge it into the cavity by gravity.

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In one embodiment, the melting furnace to form a melt by melting the raw material; characterized in that it further comprises.

In one embodiment the inner diameter of the injection tube is characterized in that larger than the inner diameter of the inlet of the cavity.

In one embodiment the pressure regulating means is characterized in that it comprises a suction screen, a vacuum pump and a suction pipe.

Another aspect of the invention relates to a duplex casting method using the duplex casting apparatus. The double casting method includes depressurizing a casting chamber filled with a filling medium by pressure adjusting means to inject molten metal into a cavity inside a mold along an injection tube by a pressure difference from the outside; And releasing the depressurization of the casting chamber before the first molten molten metal is solidified in the cavity, and secondly injected by gravity, wherein the riser is formed through the upper portion of the cavity inside the mold during the first injection. Also, the molten metal injected into the riser is discharged by gravity when the decompression of the casting chamber is released, and the second injection into the cavity is performed.

In one embodiment, the method is characterized in that the mold is put into the injection chamber inside the injection tube is mounted and coupled to the injection tube, the injection chamber is filled with a filling medium, and the primary injection by decompression.

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In an embodiment, the injection speed of the molten metal injected into the mold is controlled by adjusting the speed of depressurizing the casting chamber.

In one embodiment, the injection tube, the pressure regulating means and the filling medium is characterized in that it is reused.

When applying the dual casting method and apparatus of the present invention, it is possible to prevent shrinkage defects and bubble defects of the product, to easily remove the inclusions in the molten metal to prevent casting defects, excellent precision, complex shape It is possible to manufacture the product, and it is possible to reuse the inlet, the pressure regulating device and the filling medium, thereby reducing the cost and increasing the productivity.

1 shows a cross section of a duplex casting apparatus according to one embodiment of the invention.
Figure 2 (a) is a cross section of the injection tube according to an embodiment of the present invention, Figure 2 (b) shows a cross section of the injection tube according to another embodiment of the present invention.
3 shows a duplex casting apparatus according to another embodiment of the invention.

One aspect of the invention relates to a duplex casting apparatus.

1 shows a cross section of a duplex casting apparatus according to one embodiment of the invention. Referring to FIG. 1, the duplex casting apparatus 100 includes a casting chamber 10 having a space formed therein; An injection tube 20 fixed to a lower portion of the casting chamber 10 and into which molten metal is injected; A mold 30 which is detachably connected to the injection tube 20 and has a cavity 35; A filling medium 40 filling between the casting chamber 10 and the mold 30; And pressure adjusting means (60) positioned on the casting chamber (10) and depressurizing the inside of the casting chamber (10).

The casting chamber 10 is filled with the filling medium 40 is formed in the space so as to fix the mold 30, the pressure control means 60 by the pressure control means 60 to reduce the mold ( 30) can be provided a reduced pressure atmosphere.

The injection tube 20 is inserted into the casting chamber 10 to be mounted and fixed at a lower portion thereof, and a part thereof may protrude to be immersed in the molten metal to inject the molten metal into the mold 30. Although only one injection tube 20 is shown in the drawing, in another embodiment, a plurality of casting chambers 10 may be installed.

The injection tube 20 may be made of a conventional material. For example, a fire resistant material such as ceramic may be used, which may prevent a reaction upon contact with the molten metal, but is not limited thereto.

Referring to FIG. 1, an inner diameter d1 of the injection tube 20 may be larger than an inner diameter d2 of the cavity 35 in the present invention. In this case, the residence time of the molten metal can be increased even when the pressure is released. In one embodiment, the inner diameter d2 of the cavity 35 and the inner diameter d1 of the injection tube 20 (d2: d1) may be 1: 1.1 to 1: 3. Preferably 1: 1.5 to 1: 2.5 may be. More preferably 1: 2. The residence time of the molten metal may be increased even when the pressurization of the casting chamber 10 is released in the above range.

 The inlet shape of the injection tube 20 can be designed to be fitted to the mold. Figure 2 (a) is a cross section of the injection tube 20 according to one embodiment of the present invention, Figure 2 (b) shows a cross section of the injection tube 21 according to another embodiment of the present invention. As shown in Figure 2 (a) and 2 (b), the portion in contact with the bottom of the casting chamber may have a shape that is wider and narrower toward the top.

The mold 30 is detachably connected to the injection tube 20 and may have a cavity 35 in the form of a desired product.

The mold 30 may be made of a conventional material. For example, fireproof particles such as kneaded sand or sand may be prepared and used, including but not limited to, water-soluble phenol resins and ester-based curing agents.

The filling medium 40 may be filled in the casting chamber 10 and around the mold 30 to support the mold 30. The filling medium 40 may be used conventional. For example, refractory particles such as mixed sand or sand may be used, but are not limited thereto.

In one embodiment, while filling the filling medium 40 while applying vibration to the casting chamber 10 for a predetermined time it can be filled uniformly while increasing the filling density.

In one embodiment, the duplex casting apparatus 100 may further include a riser 50 for receiving the molten metal through the upper portion of the cavity 35 inside the mold 30 and discharging it into the cavity. The riser 50 may be included for the purpose of preventing casting defects such as bubbles or inclusions in the product during solidification of the mold 30.

In one embodiment, the riser 50 may be formed in the size of 50 to 80% by volume of the mold 30. Inclusions included in the molten metal in the above range can be easily removed, and bubbles and air remaining in the mold 30 can be easily removed.

The pressure adjusting means 60 may be positioned above the casting chamber 10 to reduce the pressure by adjusting the pressure inside the casting chamber 10. In one embodiment the pressure adjusting means 60 may include a suction screen 64, a vacuum pump (not shown) and the suction pipe (62).

The suction screen 64 may serve to pass only gas through the suction pipe 62 and prevent the suction of the filling medium 40 when the vacuum pump included in the pressure regulating means 60 operates.

The vacuum pump (not shown) may adjust the pressure of the casting chamber 10 to control the gas removal and the molten metal injection rate inside the mold 30. As the vacuum pump, a conventional one can be used. For example, an ion pump and a diffusion pump may be used, but the present invention is not limited thereto.

The suction pipe 62 may reduce the pressure in the casting chamber 10 by discharging the gas inside the casting chamber 10 to the outside during the operation of the vacuum pump. At this time, it is possible to control the injection speed of the molten metal by adjusting the speed of reducing the pressure inside the casting chamber 10.

3 shows a duplex casting apparatus 100 according to another embodiment of the invention. Referring to FIG. 3, the duplex casting apparatus 100 may further include a melting furnace 70 for dissolving raw materials to form a molten metal.

In one embodiment, the melting furnace 70 may be a conventional one. For example, a molten metal may be formed by heating a received raw material by using an electric furnace including a coil type heating element such as tungsten and kanthal.

Another aspect of the present invention relates to a duplex casting method using the duplex casting apparatus 100. In one embodiment, the dual casting method may include a step of firstly injecting the casting chamber into the cavity by depressurizing the pressure, and releasing the second pressure to inject the second chamber.

More specifically, the casting chamber 10 filled with the filling medium 40 is depressurized by the pressure regulating means 60 so that the molten metal is injected along the injection pipe 20 by the pressure difference from the outside to the inside of the mold 30. First injection into the cavity 35; Before the molten metal first injected into the cavity 35 is solidified, the casting chamber 10 may be decompressed, secondly injected by gravity, and the mold chamber may be disassembled to separate the mold. .

In one embodiment, the double casting method is to put the mold 30 in the casting chamber 10, the injection tube 20 is mounted to combine with the injection tube 20, the inside of the casting chamber 10, the filling medium ( After filling with 40) it can be injected first by decompression through the pressure adjusting means.

Hereinafter, the duplex casting method will be described in detail step by step.

(a) molten metal forming step

The step is to dissolve the raw material contained in the melting furnace 70 to form a molten metal. An electric furnace may be used as the melting furnace 70, and the raw material may be dissolved by heating using a heating element coil included in the electric furnace, but is not limited thereto.

(b) first injection step

The step is filling the filling medium 40 between the casting chamber 10 and the mold 30, and then reducing the internal pressure of the casting chamber 10 through the pressure adjusting means (60). .

The injection tube 20 of the reduced pressure casting chamber 10 is immersed in the manufactured molten metal, and the molten metal is poured along the injection tube 20 by the pressure difference between the casting chamber 10 and the outside. ) Is first injected into the cavity 35 inside.

In one embodiment, the injection tube 20 is immersed to a depth of 3 ~ 10cm in the molten metal formed in the melting furnace 70 may be injected molten metal. Under the above conditions, the injection speed of the molten metal can be easily adjusted while preventing the casting defect by preventing the external air from flowing into the molten metal as much as possible.

In one embodiment, the injection speed of the molten metal injected into the mold 30 may be adjusted by adjusting the decompression speed of the casting chamber 10 during the decompression. Specifically, the injection of the molten metal by adjusting the depressurization rate applied through the pressure adjusting means 60 to minimize turbulence according to the shape of the desired product through the data obtained through the manufacture of repeated products You can adjust the speed. As described above, bubbles are generated by turbulence of the molten metal when the injection rate is adjusted, thereby preventing casting defects such as unmolding by hindering the filling of the molten metal in the mold 30.

In another embodiment, the injection speed of the molten metal injected into the riser 50 formed through the upper part of the cavity 35 may be adjusted by adjusting the decompression speed of the casting chamber 10 during the decompression.

(c) second injection step

In this step, before the molten metal first injected into the cavity 35 is solidified, the decompression of the casting chamber 10 is released, and the second injection is performed by gravity. The primary injection is where the melt moves from bottom to top, while the secondary injection moves from top to bottom.

In one embodiment, the molten metal first injected into the cavity 35 starts directional solidification from the outside of the cavity 35. Therefore, the relatively low density inclusions (or impurities) may be easily solidified on the surface of the cavity 35. In addition, pores and bubbles formed in the cavity 35 may be easily removed while the second injection.

In another embodiment, when the riser 50 communicating with the upper portion of the cavity 35 of the mold 30 is formed, the molten metal injected into the riser 50 is discharged by gravity when the pressure is released from the casting chamber 10. Secondary injection into the cavity 35 can be made. As the molten metal injected up to the riser 50 is secondly injected into the mold 30 by gravity, pores and bubbles formed in the cavity 35 may be easily removed.

(d) dismantling stage

The step is to disassemble the second injection chamber 10 to obtain a product formed inside the mold (30).

3 shows a duplex casting apparatus 100 according to another embodiment of the invention. Referring to FIG. 3, after the manufacture of a desired product is completed using the double casting method, the casting chamber 10a is separated and dismantled, and the injection tube 20, the pressure regulator 60, and the filling medium are separated. 40 may be mounted on another casting chamber 10b and may be reused to have a cost reduction effect.

Hereinafter, the configuration and operation of the present invention through the preferred embodiment of the present invention will be described in more detail. It is to be understood, however, that the same is by way of illustration and example only and is not to be construed in a limiting sense.

Details that are not described herein will be omitted since those skilled in the art can sufficiently infer technically.

Example  One

At the lower end of the cylindrical injection chamber 10 having a diameter of 600 mm and a height of 800 mm, an injection tube 20 made of a ceramic material having a shape as shown in FIG.

Thereafter, a mold 30 having a cavity 35 including a kneading yarn, a water-soluble phenolic resin, and an ester curing agent was placed inside the injection chamber 10 by covering the inlet of the injection tube 20. At this time, the injection pipe inner diameter (d1) is Φ50mm, the cavity inlet diameter (d2) was used to form a size of Φ25mm. The mold 30 was equipped with a riser 50 communicating with the upper portion of the cavity 35.

In this case, the formed mold 30 as shown in FIG. 1 was overlaid on the injection tube 20 so as not to generate a gap. The filling chamber 40 was charged while vibrating between the injection chamber 10 and the mold 30 with a filling medium 40.

After preparing a melting furnace (electric furnace) 70 including a tungsten coil-type heating element, a raw material is added and heated to prepare a molten metal, and then a suction screen 60, a suction pipe 62, and an upper portion of the injection chamber 10. After mounting the pressure adjusting means 60 including a vacuum pump (not shown), a vacuum pump (not shown) was operated to maintain the inside of the injection chamber 10 in a vacuum state of 10 ⁻³ torr. Then, the ceramic injection tube 20 is immersed in the molten metal produced in the electric furnace to a depth of 50 mm to first inject the molten metal into the injection tube 20 to form the mold 30 and the riser 50. The molten metal was injected until. After 90 seconds, the vacuum pump was turned off to allow the molten metal injected to the riser 50 by gravity to be injected into the cavity 35 by gravity before the first molten molten metal solidified. After 120 seconds, the injection chamber 10 was moved and placed on a disassembly conveyor to obtain a product formed in the cavity 35 in the mold 30. At this time, the obtained product did not cause casting defects such as bubbles, wormholes and unmolded.

10a, 10b: casting chamber 20, 21: injection tube
30: mold 35: cavity
40: Filling medium 50: Riser
60: pressure control means 62: suction pipe
64: suction screen 70: melting furnace
100: duplex casting device

Claims (10)

A casting chamber having a space formed therein;
An injection tube mounted below the casting chamber and into which molten metal is injected;
A mold that is detachably connected to the injection tube and has a cavity;
A filling medium filled in the casting chamber and between the mold;
Pressure adjusting means positioned above the casting chamber to reduce the pressure inside the casting chamber; And
And a riser configured to receive the molten metal through the upper portion of the cavity inside the mold and discharge it to the cavity by gravity.
delete The duplex casting apparatus according to claim 1, further comprising a melting furnace for dissolving raw materials to form a molten metal.
The duplex casting apparatus according to claim 1, wherein an inner diameter of the injection tube is larger than an inner diameter of the inlet of the cavity.
The duplex casting apparatus according to claim 1, wherein the pressure adjusting means includes a suction screen, a vacuum pump and a suction pipe.
Depressurizing the casting chamber filled with the filling medium by the pressure adjusting means to inject molten metal into the cavity inside the mold along the injection tube by the pressure difference with the outside; And
And depressurizing the casting chamber before the molten metal first injected into the cavity is solidified, and secondly injected by gravity.
During the first injection, it is also injected into the riser formed through the upper cavity inside the mold,
When the decompression of the casting chamber is released, the molten metal injected into the riser is discharged by gravity and injected into the cavity secondly.
delete The method of claim 6, wherein the method comprises inserting a mold into a casting chamber in which an injection tube is mounted, integrating with the injection tube, and filling the casting chamber with a filling medium, followed by primary injection by decompression.
The duplex casting method according to claim 6, wherein an injection speed of the molten metal injected into the mold is controlled by adjusting a speed of depressurizing the casting chamber.
The duplex casting method according to claim 6, wherein the injection tube, the pressure regulating means and the filling medium are reused.

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