JPH05228606A - Casting method - Google Patents

Abstract

PURPOSE:To surely cast molten metal at the time of manufacturing a small size casting by pouring the molten metal into a mold. CONSTITUTION:After the metal 7 in a crucible 3 is melted by making inert gas atmosphere in a melting chamber 1 having the crucible 3 providing an opening part 3b at the center part of a bottom wall 3a and inner side of a casting chamber 2 having the mold 14 is air-tightly communicated with the lower part, the casting chamber 2 is evacuated. The molten metal 7a is dropped into a casting hole 14a of the mold 14 in a lump from an opening part 3b by forcibly pouring the inert gas, successibly, the molten metal is cast into the mold 14.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a casting method for pouring a molten metal into a mold for producing a small casting for dental or industrial use.

[0002]

2. Description of the Related Art Conventionally, a crucible has been used in a molten metal injection device for carrying out this type of casting method. As the crucible, one shown in FIG. 3 or FIG. 4 is known.
That is, in the crucible 21 shown in FIG. 3, when the metal melted in the crucible 21 is poured into the mold, the crucible 21 is tilted and the crucible 21 is inclined.
In the case of the crucible 23 shown in FIG. 4, the molten metal is flowed out from the upper outlet 24. Although not shown in the figure, there is also a dish-shaped crucible with a shallow depth, but both are outflow guide grooves 22 or outflow ports 2.
4 is provided, and the molten metal is made to flow out from that part.

In general, alloys used for precision casting of this kind often have a small amount of about several grams to several tens of grams. Therefore, when such a small amount of metal is melted using the crucible as described above and injected into the mold, the molten metal is cooled and solidified while passing through the outflow guide groove 22 or the outlet 24 having a relatively low temperature. Begins,
This is not only a problem in the casting operation, but also an inability to maintain an appropriate casting temperature, and in the case of a precious metal, there is a loss due to adhesion. It is conceivable to heat the molten metal to an appropriate temperature or higher in order to prevent early solidification as described above, but in that case, there are problems such as roughened casting surface, generation of porosity, and deterioration of metal structure. Occurs.

The present applicant has previously proposed the following apparatus as a molten metal injection apparatus suitable for a casting method for solving the above problems and producing a small casting. That is, as shown in FIG. 5, the crucible 25 is formed in a tapered cylindrical container shape, and has a flange-shaped portion 27 outside the upper opening 26.
A cylindrical side wall 28 is formed so as to extend below the bottom wall 29, and the whole is vertically divided into two parts at the center to form parts 25a and 25b.
Has become. Reference numeral 30 denotes a mating surface of the portions 25a and 25b, and a notch portion 31 is formed at the upper end position from above. Further, supported portions 32a and 32b projecting downward are provided at the symmetrical positions below the flange portion 27 in each of the two divided portions 25a and 25b.

The crucible 25 thus formed is shown in FIG.
As shown in (a), the crucible raising / lowering support body 34 is provided above the high-frequency coil 33 of the precision casting machine and is coupled to a driving means such as an air cylinder or a manual lever (not shown) so as to move up and down by a predetermined dimension. The supported portions 32a and 32b are supported by the edges of the hole 34a, and the lower portion of the tubular side wall 28 is inserted into the tapered hole 36 of a crucible restraining body 35 that is separately fixed. In this state, the bottom wall 29 is located near the center of the high frequency coil 33, and the mating surface 30 is closed.

The metal melted to the pouring temperature in the crucible 25 of the pouring device having such a structure is cast into a mold (not shown) arranged under the restraining body 35 from the opening gate above the mold. Be done. In this casting operation, when the raising / lowering support body 34 is raised by the air cylinder or the manual lever from the state of FIG. 6 (a), the crucible 25 is also raised, and its cylindrical side wall 2
The lower part of 8 is pulled out from the inserted tapered hole 36. Then, in the crucible 25, the portions 25a and 25b are respectively the supported portions 3
Since it is supported only by 2a and 32b, the lower parts naturally open on both sides as shown in FIG. 6 (b) due to the respective centers of gravity, whereby the molten metal inside falls into the mold. Of.

[0007]

However, in the casting method using the molten metal injecting apparatus described above, the molten metal in the crucible reaches the casting temperature and then the lifting support is raised from the state of FIG. 6 (a). The crucible rises, and Fig. 6 (b)
When the molten metal has a large wettability, the molten metal adheres to the cut end of the bottom wall of the crucible. Therefore, there is a problem that not all of the molten metal is injected into the mold. In addition, in order to solve this problem, when injecting an inert gas such as argon gas under pressure when injecting the molten metal into the mold, the molten metal adhering to the outside of the center of the bottom wall cutout becomes outside the mold. There was a problem of scattering.

[0008]

The present invention has been obtained as a result of studies for solving the above-mentioned problems in the conventional method of casting a molten metal in a mold, and has a container shape with an upward opening. A metal melting furnace having a melting chamber having an opening at the center of the bottom wall and having a crucible containing the metal to be melted therein, and a casting chamber having a mold connected below the melting chamber. In, the step of filling the casting chamber and the melting chamber with the inert gas by injecting an inert gas from the casting chamber upper part after exhausting the melting chamber and the casting chamber from the melting chamber upper part, Melting chamber: a step of melting the metal in the crucible, a step of vacuuming the casting chamber after melting the metal, a step of dropping the molten metal from the opening of the crucible to the casting port of the mold in the casting chamber, and casting immediately after dropping. Injecting inert gas under pressure into the room It is an object to provide a process, a casting method characterized in that it consists.

[0009]

The method of the present invention is a casting method using a metal melting furnace consisting of a melting chamber and a casting chamber which is hermetically connected to the melting chamber. The crucible is provided in the melting chamber and is formed in the shape of a container opening upward. Has an opening in the center of its bottom wall, melts the metal in the crucible under an inert gas atmosphere in the melting chamber and the casting chamber, and then vacuums the casting chamber to melt the molten metal into the mold in the casting chamber. It is dropped into the casting mouth as a lump, and then the molten metal that has fallen by pressurizing and injecting an inert gas into the casting chamber is surely cast into the mold, and the crucible is tilted like the conventional casting method, It is possible to reliably perform casting by suction and gravity by exhaust of the casting chamber without rotating.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings. For convenience, the casting apparatus used in the method of the present invention will be described first. As shown in FIG. 1, this apparatus comprises a melting chamber 1 and a casting chamber 2. The lower central part of the melting chamber 1 is open, the upper part is opened in the opening, and the crucible 3 has an opening 3b at the center of the bottom wall 3a.
c, the ceramic side wall 4 of the melting chamber 1 and the silicon O
It is supported along the side member 5 at the upper part of the U-shaped side member 5 made of metal and sealed by the ring 6. The metal 7 to be melted is accommodated in the crucible 3.

Around the U-shaped member 5, a high frequency induction winding 8 is provided as a heating source for melting the metal 7 in the crucible 3. Reference numeral 9 is a heat-resistant glass observation window provided in the upper portion of the melting chamber 1 for observing the melting state of the metal 7 in the crucible 3, and 10 is an exhaust connected to a vacuum pump (not shown). It is a mouth.

Reference numeral 11 denotes a casting chamber furnace body made of metal and formed in a container shape, and its side wall is sealed with a bottom wall of the U-shaped side member 5 made of metal of the melting chamber 1 and an O-ring 12 made of silicon. Thus, a casting chamber 2 that is airtightly connected to the melting chamber 1 is formed below the melting chamber 1. A mold 14 having a casting port 14a is fitted into the casting chamber 2 via a heat insulating material 13 at a position directly below the opening 3b of the crucible 3 on the upper surface. 1
5 is an inert gas inlet provided in the upper part of the casting chamber 2,
A low pressure gas introduction pipe 16 and a high pressure gas introduction pipe 1 are provided at the introduction port 15.
7 is connected. Reference numeral 18 is an exhaust port connected to a vacuum pump (not shown) provided to make the casting chamber 2 a vacuum.

The casting method of the present invention is carried out as follows using the casting apparatus having the above structure. Now, Figure 1
As shown in FIG. 3, the melting metal 7 is housed in the crucible 3 and the melting chamber 1 and the casting chamber 2 are sealed. And the side wall 4 of the melting chamber 1
The inside of the melting chamber 1 and the casting chamber 2 is evacuated from the exhaust port 10 provided in the inside by a vacuum pump (not shown) or the like, and a vacuum state is obtained. Then, an inert gas such as argon gas is introduced into the casting chamber 2 from the low-pressure gas introduction pipe 16 to introduce the casting chamber 2 and the melting chamber 1 into an inert gas atmosphere. In this inert gas atmosphere, high-frequency power is applied to the high-frequency induction winding 8 arranged around the side member 5 of the melting chamber 1 to heat and melt the metal 7 in the crucible 3 of the melting chamber 1. The gas generated from the metal, the heat insulating material, the crucible and the like during the heating and melting is discharged from the exhaust port 10 by the inert gas.

Thus, the metal 7 in the crucible 3 melts from the state of FIG. 3 (a) to 7a of FIG. 3 (b). The metal 7a thus melted in the state of FIG. 3 (b) is rotating due to its surface tension and high-frequency eddy current, and the supplied inert gas flows from the opening 3b of the crucible 3 into the crucible 3. There is no possibility of falling from the opening 3b because it is flowing into. When the metal is completely melted, the power supply to the high-frequency induction winding 8 is stopped, the supply of the inert gas is stopped, and at the same time, the exhaust port 18 provided in the upper part of the casting chamber 2 exhausts with a vacuum pump. Due to this exhaust, the pressure in the casting chamber 2 becomes lower than that in the melting chamber 1, so that the molten metal 7a in FIG.
It will be pulled downward from b. Due to this suction and gravity, the molten metal 7a begins to drop from the opening 3b as shown by 7b in FIG. 3 (c), and then to the casting port 14a of the mold 14 in a lump. At this time, the inert gas inlet 15
By injecting an inert gas under pressure from above, the molten metal that has fallen into the casting port 14a can be completely cast into the mold 14. In this example, the opening 3b of the crucible 3 was set to 3 mmφ and 40 kg of molten metal was used to obtain 4 kg / cm.
^When tested under the pressure condition of ² , casting could be surely performed in the mold. Further, in this embodiment, the crucible 3
High frequency induction winding 8 as a heating source for melting metal 7 in
Although the example of arranging the outside of the melting chamber 1 is shown, it may be provided inside the melting chamber 1. Argon gas was used as the inert gas, but any gas can be used as long as it does not chemically react with the molten metal.

[0015]

As described above, according to the casting method of the present invention, a crucible that is supported in the melting chamber and that contains the metal to be melted and has an opening at the center of the bottom wall is used, and the crucible was melted in the crucible. When the metal is dropped from the opening into the casting port of the mold in the casting chamber that is connected to the lower part of the melting chamber, the molten metal is dropped as a lump by suction and gravity by applying a vacuum to the casting chamber to lower the pressure than the melting chamber. Can
Furthermore, it has the effect that it can be reliably cast into the mold by injecting a pressure of an inert gas, there is no need to incline or rotate the crucible as in the conventional method, and due to the temperature drop of the molten metal It is possible to obtain a good casting without any roughening of the casting surface or generation of porosity.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view of a casting apparatus used in the casting method of the present invention.

2 (a) to (c) are partial cross-sectional views showing a state of molten metal in a crucible according to the casting method of the present invention.

FIG. 3A is a plan view of a conventional crucible, and FIG. 3B is a side view.

FIG. 4A is a plan view showing another conventional crucible, and FIG.
FIG. 7A is a sectional view taken along line AA of FIG.

FIG. 5A is a plan view showing still another conventional crucible,
(B) is a side view.

6 (a) and 6 (b) are vertical cross-sectional views showing a usage state of a conventional molten metal injection apparatus using the crucible of FIG.

[Explanation of symbols]

 1 Melting Chamber 2 Casting Chamber 3 Crucible 3a Crucible Bottom Wall 3b Opening 7 Metal 7a Molten Metal 7b Molten Metal 8 High Frequency Induction Winding 14 Mold 14a Casting Port

Claims (1)

[Claims] 1. A melting chamber which is formed in the shape of a container that opens upward, has an opening in the center of the bottom wall, and has a crucible in which the metal to be melted is housed, and is connected below the melting chamber. In a metal melting furnace having a casting chamber having a mold, after exhausting the melting chamber and the casting chamber from the melting chamber upper part, an inert gas is injected from the casting chamber upper part to cast the casting chamber and the melting chamber with the inert gas. A step of filling, a step of melting the metal in the melting chamber crucible when filled with an inert gas, a vacuum is applied to the casting chamber after melting the metal, and the molten metal is cast into a mold in the casting chamber through the opening of the crucible. A casting method comprising a step of dropping into the mouth and a step of injecting an inert gas under pressure into the casting chamber immediately after dropping.