JPS61180642A - Vacuum casting method - Google Patents

Abstract

PURPOSE:To manufacture castings excellent in transferring properties by closing an ingate hole by the ingate-hole cover of a chamber incorporating a porous mold therein and evacuating its inside before pouring a molten metal into a forming recessed-part of mold through the ingate hole while melting the cover. CONSTITUTION:A mold 17 having air permeability is set in a chamber 1, and the inside of chamber 1 is evacuated to a prescribed pressure after closing an ingate hole 11 of chamber 1 by an ingate-hole cover 15. Next, a molten metal is poured into a forming recessed part of mold 17 while melting the cover 15 by the heat of molten metal. Further, the inside of chamber 1 is filled with an inert gas after finishing the pouring. In this way, castings excellent in transferring properties can be manufactured.

Description

DETAILED DESCRIPTION OF THE INVENTION Object of the Invention (Field of Industrial Application) The present invention relates to a vacuum casting method for casting synthetic resin molds and the like.

(Prior Art) Conventionally, there has been a method of casting using an air-permeable mold, such as a porous gypsum mold, for the purpose of improving the transferability of uneven patterns etc. from the mold to the casting. In this method, as shown in FIG. 2, a flat pressure box 41 is brought into close contact with the lower surface of the mold 40 in advance, and the air in the molding recess 42 of the mold 40 is sucked to reduce the pressure. The molten metal such as cast iron was being poured out.

(Problems to be Solved by the Invention) However, with the above depressurization method, it is difficult to obtain a sufficient depressurization effect because the air suction area is only a part, and for this reason, there is a problem that it is difficult to obtain castings with good transferability. There was a problem that the castings were easily oxidized.

Structure of the Invention (Means for Solving the Problems) In order to solve the above problems, in the present invention, a mold 17 with ventilation is installed in the chamber 1, and a sprue hole provided in the chamber 1 is installed in the chamber 1. 11 is closed with a sprue cap 15 made of a material that can be melted by the heat of the molten metal, the inside of the chamber 1 is reduced to a predetermined pressure, and then the sprue cap 15 is melted by the heat of the molten metal to close the sprue hole 11. A method of injecting molten metal into the mold 17 was adopted.

In the second invention, in addition to the above-mentioned means, after pouring the molten metal into the mold, a reduced pressure chamber is filled with an inert gas, and the molten metal is solidified in a non-oxidizing atmosphere.

(Function) In the present invention, a mold with air permeability is provided in a chamber, the sprue hole of the chamber is closed with a sprue cover, and the air in the chamber is sucked by a pump to reduce the pressure. Since the molten metal is injected into the forming recess of the mold through the sprue hole of the chamber while melting the sprue cap provided on the sprue hole, the molten metal such as cast iron flows into the forming recess due to the pressure difference with atmospheric pressure. When this happens, air entrainment is prevented. Furthermore, since the chamber is maintained at a reduced pressure state, the molten metal is uniformly drawn into the molding recesses of the mold and spreads to every corner.

Therefore, a casting can be formed with good transferability of shapes such as irregularities from the mold to the casting, and oxidation can be prevented during the casting manufacturing process.

In the second invention, in addition to the effect of the first invention, the chamber is filled with inert gas after pouring is completed, so that the molten metal solidifies in the non-oxidizing atmosphere of the diffused inert gas.

Therefore, oxidation of the surface of the molten metal at high temperatures can be prevented, and the oxidation-preventing effect during production becomes even more remarkable.

(Example) Hereinafter, a first example in which the present invention is embodied in a method for casting a synthetic resin mold will be described with reference to FIG.

First, the configuration of the casting apparatus used in the first embodiment of the present invention will be described.

Flanges 3 and 4 are provided at the upper and lower ends of the cylindrical chamber body 2, respectively. Annular grooves 5 and 6 are provided on the end faces of the flanges 3 and 4, respectively.
6 are fitted with O-rings 7°8, respectively. An upper lid 9 and a bottom plate 10 are fastened to the upper and lower end surfaces of the chamber main body 2 by fasteners (not shown) so as to press the O-rings 7.8, respectively. and a bottom plate 10 constitute a chamber 1,
The airtightness inside the chamber 1 is maintained.

The upper lid 9 is provided with a circular sprue hole 11.

An annular groove 12 is provided around the sprue hole 11, and an O-ring 13 is fitted therein. Further, a hopper 14 having a cone shape is provided on the outer peripheral side of the groove 12.

The sprue hole 11 is covered with a sprue cover 15 so as to come into contact with the O-ring 13 to maintain airtightness within the chamber 1.

The hot water spout 15 is formed into a plate shape of a low melting point metal that is melted by the molten metal such as molten iron, has an affinity for the molten metal, and contains a component that produces a deoxidizing effect. Further, the thickness of the sprue cover 15 is adjusted according to the amount of pouring. In other words, when cast iron is used as the molten metal, the sprue cover 15 is made of aluminum containing silicon, manganese, etc. that produces a deoxidizing effect, and the thickness of the plate matches the amount of poured metal.
form.

The lower part of the sprue hole 11 is connected to a mold 17 having air permeability through a pouring port 16.

The mold 17 is provided with a large number of fine ventilation holes to provide ventilation, and is made of gypsum, ceramics, etc.
It consists of a molding recess A and a sump B for a riser.

Further, a pressure reduction hole 19 for reducing the pressure inside the chamber 1 is provided at the lower part of the chamber main body 2, and the pressure reduction hole 19 is connected to a pressure reduction pump 21 via a vacuum hose 20.
It is connected to the.

An inert gas injection hole 22 is provided above the decompression hole 19 to create a non-oxidizing atmosphere in the chamber 1, and an inert gas cylinder 2 such as argon is injected via a hose 23.
Connected to 4.

Further, by providing the decompression hole 19 and the injection hole 22 at the lower part of the chamber main body 2, deformation of the hose 20, 23 due to the influence of heat from the mold 17 is prevented.

The vacuum casting apparatus as described above is assembled as follows.

First, the upper and lower flanges 3 of the chamber body 2,
4, fit the O-ring 7°8 coated with heat-resistant grease, and place the end faces on the bottom plate 10 with a fastener (not shown).
Combine with .

Next, place the mold stand 18 on the top surface of the bottom plate 10 and
The position and height of the sprue are adjusted in advance so that it fits in the sprue hole 11, and the mold 17 and the spout 16 are set above it.

The upper cover 9 is placed over the chamber main body 2 so that the sprue hole 11 is aligned with the casting opening 16, and is fixed to the upper flange 3 with fasteners or the like.

Then, the O-ring 13 with heat-resistant grease applied to the groove 12
and properly close the sprue hole 11 with the sprue cover 15. At this time, the material and plate thickness of the sprue cover 15 are selected depending on the type of molten metal.

Finally, the hose 20 of the vacuum pump 21 and the hose 22 of the inert gas cylinder 23 are connected to the vacuum hole 19 and the inert gas injection hole 22, respectively, and the assembly of the chamber 1 is completed.

Additionally, as mentioned above, this device is easy to assemble and disassemble, and is also easy to move.

Next, the manufacturing method of the first invention using the above-mentioned apparatus will be described.

The pressure reduction pump 21 is operated to reduce the pressure inside the chamber 1 to 2
After reducing the pressure to 60-160 mm/Hg, a molten metal such as iron that has been melted in advance is poured into the hopper 14.

The molten metal stored in the hopper 14 melts the sprue cap 15 by the heat of the molten metal, and the molten metal is poured into the sprue hole 15 by atmospheric pressure.
, a mold 17 with reduced air permeability through the pouring port 16
It flows into the molding recess A and the sump B.

In the molding recess A, the pressure is reduced by a large number of ventilation holes, so that the molten metal spreads throughout the molding recess A so that it is in close contact with every corner of the molding recess A.

Moreover, at this time, silicon and manganese contained in the sprue cap 15 dissolve into the molten metal and deoxidize the oxygen in the molten metal.

As described above, the mold 1 with air permeability inside the chamber 1
At the same time, the sprue hole 11 is closed with the sprue cover 15 which is melted by the heat of the molten metal, and the pressure inside the chang t<-1 is reduced to perform casting. It is possible to prevent air from flowing into the mold 17 under reduced pressure. In addition, the molten metal is sucked and poured into the molding recess A of the mold 17 under reduced pressure due to atmospheric pressure 1, and since the entire inside of the recess A is uniformly depressurized by the ventilation holes, the molten metal adheres to every corner of the mold. The uneven pattern of the mold is extremely well transferred to the casting.

Therefore, castings with excellent transferability can be produced.

Furthermore, since the sprue cap 15 contains a component that causes a deoxidizing effect, the oxygen in the molten metal is deoxidized, resulting in a casting that is resistant to oxidation.

In the second invention, in addition to the steps of the first invention, a step of injecting argon gas, which is an inert gas, into the chamber 1 after pouring is completed, and solidifying the molten metal in a non-oxidizing atmosphere is added. did.

Therefore, in the second embodiment, which is an embodiment of the second invention, in addition to the first embodiment described above, an inert gas provided in the lower part of the chamber body 2, which was not used in the first embodiment, after the completion of pouring. This adds a step of filling the injection hole 22 with argon gas, which is an inert gas. In this example, argon gas is used to create a non-oxidizing atmosphere.

Note that the present invention and the second invention are not limited to the above-mentioned embodiments, but may be embodied as follows.

(1) The sprue cover 15 may be formed of metal such as copper, plastic, or the like in addition to aluminum, as long as it is melted by the heat of the molten metal and contains a compound that deoxidizes the molten metal.

(2) In the process of solidifying the molten metal, the solidification time of the molten metal can be adjusted, and a heat insulating material of arbitrary material and thickness can be provided on the inner wall of the chamber 1 so that the solidification time suitable for the casting can be obtained.

Effects of the Invention As described in detail above, in the present invention, the pressure inside the molding recess of the mold can be uniformly reduced, and the molten metal can be sucked and poured due to the difference in pressure from the atmospheric pressure. is adhered to every part of the mold, making it possible to produce castings with extremely good transferability. In addition, since the sprue hole is closed with a sprue cap and the air in the molding recess of the mold is sucked by a pump to reduce the pressure during casting, there is less air entrainment during casting, and oxidation of the cast product can be prevented.

In addition to the effects of the first invention, the second invention solidifies the casting in a non-oxidizing atmosphere by filling with an inert gas, so oxidation of the surface of the molten metal can be prevented, and oxidation prevention effect during manufacturing. becomes even more prominent.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing an apparatus used in the first and second inventions, and FIG. 2 is a cross-sectional view of essential parts showing a conventional casting method. Chamber 11 Hot water hole 111 Hot water hole lid 15, mold 17° Patent applicant: Toyoda Gosei Co., Ltd. agent, patent attorney Hironobu Onda.

Claims (1)

[Claims] 1. Mold (17) with ventilation inside the chamber (1)
and the sprue hole (1) provided in the same chamber (1).
1) with a sprue cap (15) made of a material that can be melted by the heat of the molten metal, the inside of the chamber (1) is reduced to a predetermined pressure, and then the sprue cap (15) is closed by the heat of the molten metal. The mold (1) is removed from the sprue hole (11) by melting the
7) A vacuum casting method characterized by injecting molten metal into the mold. 2. The vacuum casting method according to claim 1, wherein the sprue cap (15) is made of a material that has an affinity for the molten metal and contains a component that deoxidizes the molten metal. 3. Mold (17) with ventilation inside the chamber (1)
and the sprue hole (1) provided in the same chamber (1).
1) is closed with a sprue cap (15) made of a material that can be melted by the heat of the molten metal, the inside of the chamber (1) is reduced to a predetermined pressure, and then the sprue cap (15) is melted by the heat of the molten metal. from the sprue hole (11) to the mold (17).
After pouring the molten metal into the chamber (1),
) is a vacuum casting method characterized by filling the inside with inert gas. 4. The vacuum casting method according to claim 3, wherein the sprue cover (15) is made of a material that has an affinity for the molten metal and contains a component that deoxidizes the molten metal.