JPH04367363A - Metal casting method and casting equipment - Google Patents

Abstract

PURPOSE:To obtain a casting having excellent internal quality and shape accuracy without developing gas defect and misrun. CONSTITUTION:Metal base material 31 in a water-cooled copper crucible 4 air-tightly sealing the inner part, is melted with induction heating and successively, into a casting space 25 in a mold 24 communicating a runner 23 with the molten metal, the molten metal is pressed up through the runner 23 with gas pressurizing to the molten metal, and cast in the casting space 25.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for casting metals, which are used to obtain cast products of, for example, high-melting point metals and active metals.

0002

[Prior Art] High melting point metals or active metals consisting of Ti, W, Mo, Zr, Li, etc. alone or in alloys,
Because it has a high melting point and is active, it tends to form an oxide film on the surface of the molten metal, and if the molten metal is disturbed during casting, it tends to entrain gas.

In order to prevent such disturbances in the molten metal, it is necessary to regulate the molten metal and inject it into the casting space of the mold.

The present inventors have developed a method of suctioning the inside of the mold in order to inject molten metal into the mold in a rectified state, and have achieved significant improvements (for example, in Japanese Patent Application No.
No. 12104, Japanese Patent Application No. 146743, Japanese Patent Application No. 2-
124383 etc.).

[0005]

[Problems to be Solved by the Invention] However, in the above-mentioned casting method in which the inside of the mold is suctioned, there is a risk that the inert gas in the melting chamber will be drawn in, and therefore, it is not possible to maintain a large gas pressure differential. Therefore, there is a problem that it cannot be said that there is no possibility of occurrence of poor hot water supply, and it has been a challenge to solve this problem.

[0006]

[Object of the Invention] The present invention has been made in view of the above-mentioned conventional problems, and does not involve the inert gas in the melting chamber in the crucible during casting, thereby preventing the occurrence of gas defects and poor running of hot water. The object of the present invention is to provide a metal casting method and a casting apparatus that enable high-quality castings to be obtained.

[0007]

[Means for Solving the Problems] A metal casting method according to the present invention involves melting a metal base material in a water-cooled copper crucible whose interior is hermetically sealed by induction heating, and then connecting a runner to the molten metal. It is characterized by having a structure in which the molten metal is pushed up through the runner into the casting space of the mold by pressurizing the molten metal to perform casting in the casting space. It is characterized by having a structure in which the atmosphere is vacuumed, and also in a structure in which an inert gas is introduced into the water-cooled copper crucible at the time of casting, and the molten metal is pushed up by a pressure difference to cast within the casting space.

[0008] Furthermore, the metal casting apparatus according to the present invention includes:
A water-cooled copper crucible whose interior can be airtightly sealed, an induction heating means for melting the metal base material in the water-cooled copper crucible, a mold having a runner and a casting space, and the runner communicating with the molten metal. A means for lifting and lowering a mold and/or a water-cooled copper crucible, and gas pressure that pressurizes the molten metal with gas in a state where the runner is in communication with the molten metal, thereby pushing the molten metal up into the casting space through the runner. It is characterized by having a structure equipped with a supply means, and in embodiments, the mold is made of breathable ceramics, the mold is made of breathable metal, and the runner is made of breathable metal. The present invention is characterized by a structure made of ceramics that do not have air permeability, and the structure of the invention related to the above-described metal casting method and casting apparatus is a means for solving the above-mentioned conventional problems.

[0009]

Effects of the Invention The metal casting method and casting apparatus according to the present invention have the above-described configuration, so that the molten metal melted in the water-cooled copper crucible passes through the runner by pressurizing the molten metal with gas. The melt is pushed up into the casting space of the mold in a rectified state through the melting chamber, and there is no risk of the inert gas in the melting chamber being drawn in. This prevents gas defects and allows for a large gas differential pressure. As a result, there is no problem with the flow of the hot water, resulting in a cast product with excellent internal quality and shape accuracy.

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIGS. 1 to 3 show an embodiment of the present invention.

As shown in FIGS. 1 and 2, a metal casting apparatus 1 according to an embodiment of the present invention has a seal pipe 2 on the lower side thereof, and a heat insulating material 3 on the bottom side of the seal pipe 2. A water-cooled copper crucible 4 is installed above the heat insulating material 3 and inside and at the upper end of the seal pipe 2.

As shown in FIG. 2, this water-cooled copper crucible 4 includes a plurality of water-cooled copper segments 4a arranged in a ring shape and insulated from each other by insulators 5a, . . . , 5h.
,...,4h, each segment 4a,...,
Water cooling is possible by providing water cooling pipes 6a, .
It has the following structure.

[0013] Also, on the bottom side of this water-cooled copper crucible 4,
A conductive refractory material (graphite) 8 that generates heat during induction heating and a non-magnetic refractory material (BN) 9 are provided, and the inside of the melting chamber 10 is hermetically sealed and isolated from the outside. ing.

Furthermore, an induction heating coil 11 serving as induction heating means is installed on the outer peripheral side of the seal pipe 2.

On the other hand, a casting chamber casing 12 is installed on the upper side of the magnetic shielding section 7, and is provided with a glass window 13 for observation, and an annular flange 14 on the outer peripheral side of the upper end. An upper plate 16 is provided on the annular flange 14 via a seal ring 15, and an elevating rod 18 is provided on the upper plate 16 via a seal ring 17 so as to be movable up and down.

This elevating rod 18 has a large diameter portion 18a inside the casting chamber casing 12, and also has a large diameter portion 18a.
It has a ventilation hole 18b on the lower side of a, and also has a lifting rod 1
8 has an opening 18c connected to a pressure reducing means 19 on the upper side thereof.

Further, a casting chamber chamber 21 is fixed to the large diameter portion 18a of the lifting rod 18, and a mold 24 having a runner 23 formed of a graphite pipe 22 is installed inside the casting chamber chamber 21. It has been done.

The mold 24 is composed of an air-permeable inner refractory 24a forming a casting space 25, an air-permeable heat-resistant fiber 24b, and a lower refractory 24c, and has a tapered hole formed in the casting chamber 21. 21a.

Furthermore, a gas pressure supply pipe 28 connected to a gas pressure supply means 27 is provided on the wall of the casting chamber casing 12 .

When manufacturing a hot wheel for a turbocharger using such a metal casting apparatus 1, a Ti--Al alloy was used as the molten base material 31.

After charging 400 g of the melted base material 31 into the melting chamber 10, the inside of the casting space 25 and the inside of the melting chamber 10 are made vacuum (10 Torr or less) by the pressure reducing means 19, and the induction heating coil 11 is heated. By applying electricity, the melting base material 31 was induction melted under vacuum.

At this time, for melting, so-called cold crucible levitation melting using a water-cooled copper crucible 4 in which water-cooled copper segments 4a, . . . , 4h are divided by insulators 5a, . Therefore, an eddy current is formed in the inner part of the water-cooled copper crucible 4 by high-frequency induction heating by the induction heating coil 11, and this eddy current induces a skin eddy current in the molten base metal 31 and melts it, thereby melting the molten metal 32. (see Figure 3).

[0023] Then, due to the repulsive force of the currents having opposite phases on the surfaces of the water-cooled copper crucible 4 and the molten metal 32, the molten metal 32 is moved a little away from the inner surface of the water-cooled copper crucible 4, forming a gap. .

[0024] Therefore, the heat transfer from the molten metal 32 to the water-cooled copper crucible 4 is suppressed by the formation of the gap, so the molten metal 32 has a high temperature and good flowability.

After melting the melting base material 31 shown in FIG.
As shown in FIG. 3, the lifting rod 18 is lowered and the graphite pipe 22 is immersed in the molten metal 32, thereby communicating the runner 23 with the molten metal 32.

Next, Ar gas, which is an inert gas, is supplied from the gas pressure supply means 27 through the gas pressure supply pipe 28.
By applying gas pressure to the surface of the molten metal 32, the molten metal 32 was pushed up within the runner 23 by a pressure difference, and this molten metal 32 was forced into the casting space 25 of the mold 24. Note that the differential pressure at this time was adjusted to 500 Torr.

After that, the mold 24 was taken out, the mold was disassembled, the cast product was taken out, and the occurrence of gas defects and poor hot water circulation was investigated. The quality of the cast products was excellent, increasing to over 90%.

[0028]

[Effects of the Invention] According to the metal casting method and casting apparatus according to the present invention, since they have the above-described configuration,
The molten metal melted in the water-cooled copper crucible is pushed up into the casting space of the mold through the runner in a rectified state by gas pressure applied to the molten metal, and the inert gas in the melting chamber is forced into the molten metal. Since it is not caught in the gas, gas defects are less likely to occur, and since it is possible to create a large differential pressure, there is no possibility of poor water flow, resulting in castings with excellent internal quality and shape accuracy. This brings about a remarkable effect in that it is possible to manufacture products.

[Brief explanation of drawings]

FIG. 1 is an explanatory longitudinal cross-sectional view showing an embodiment of a metal casting apparatus according to the present invention during melting of a metal base material.

FIG. 2 is an explanatory horizontal cross-sectional view of the water-cooled copper crucible in FIG. 1;

FIG. 3 is an explanatory longitudinal cross-sectional view of the metal casting apparatus shown in FIG. 1 during casting of molten metal.

[Explanation of symbols]

1 Metal casting device 4 Water-cooled copper crucible 10 Melting chamber 11 Induction heating coil (induction heating means) 18 Elevating rod (elevating means) 19 Pressure reducing means 23 Runway 24 Mold 25 Casting space 27 Gas pressure supply means 31 Metal base material 32 Melting metal

Claims (7)

[Claims] 1. A metal base material in a water-cooled copper crucible whose interior is airtightly sealed is melted by induction heating, and then gas is added to the molten metal in a casting space of a mold with a runner communicating with the molten metal. A method for casting metal, characterized in that the molten metal is cast in the casting space by pushing up the molten metal through the runner using pressure. [Claim 2]Claim 1: The atmosphere during melting is a vacuum.
The metal casting method described in . 3. The metal casting method according to claim 1, wherein an inert gas is introduced into the water-cooled copper crucible during casting, and the molten metal is pushed up by a pressure difference to cast the metal in the casting space. 4. A water-cooled copper crucible whose interior can be airtightly sealed, an induction heating means for melting a metal base material in the water-cooled copper crucible, a mold having a runner and a casting space, and a mold for melting the runner. A means for lifting and lowering a mold and/or a water-cooled copper crucible that communicates with the inside of the metal, and pressurizing the molten metal with a gas with the runner communicating with the inside of the molten metal, thereby transferring the molten metal through the runner into the casting space. A metal casting device characterized by being equipped with a gas pressure supply means for pushing up the metal. 5. The metal casting apparatus according to claim 4, wherein the mold is made of air-permeable ceramic. 6. The metal casting apparatus according to claim 4, wherein the mold is made of a metal having air permeability. 7. The metal casting apparatus according to claim 4, wherein the runner is made of ceramic having no air permeability.