JPH05261516A - Gas pressure casting method of active metal - Google Patents

Abstract

PURPOSE:To improve the run of the molten metal by rapidly increasing the pressure of the inert gas atmosphere immediately after the molten active metal dissolved in a water-cooled copper crucible is cast in a ceramics mold, and also improve the run by heating the ceramics mold to the specified temperature in addition to the gas pressurization. CONSTITUTION:A water-cooled crucible 3 where the active metal 2 for casting is placed in a pressure-proof vessel 1 and a ceramics mold 4 are set in place. When the temperature of the metal 2 for casting reaches the specified value, the metal falls from an inlet port 3b and in the ceramics mold 4. Immediately after the casting is completed, the pressure in the pressure-proof vessel 1 is rapidly increased, improving the run.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a casting method when an active metal is melted without contact with a water-cooled copper crucible.

[0002]

2. Description of the Related Art To melt an alloy of an active metal such as titanium or niobium or an intermetallic compound, a water-cooled copper crucible is used to avoid a reaction with the crucible, and a strong magnetic force is applied to the crucible to melt the molten metal. Methods have been developed for melting without contacting the crucible. As a casting method at this time, since the molten metal is rapidly cooled by coming into contact with a water-cooled copper crucible in a usual tilting method, gravity is dropped from the bottom of the crucible or vacuum suction is performed upward from the molten metal surface. However, in this melting method, since the supply power is limited in order to maintain the stability of the shape (molten column) of the molten metal, the degree of superheat of the molten metal cannot be increased so much. Therefore, the above-mentioned casting method has a problem that sufficient molten metal cannot be obtained in the thin portion of the cast product.

On the other hand, silica (SiO ₂ ) type and zirconia (ZrO ₂ ) type are generally used as the material of the ceramic mold, but these cannot react with the above-mentioned active metals, so that the reactivity of them is high. There is no choice but to use a low yttria (Y ₂ O ₃ ) system. However, the yttria-based mold has a problem that the molten metal is cooled quickly because of its high thermal conductivity, and the molten metal distribution is significantly reduced.

[0004]

SUMMARY OF THE INVENTION The problem to be solved by the present invention is to solve the above shortage of hot water supply as follows. That is, immediately after casting the molten metal of the active metal melted in the water-cooled copper crucible into the ceramic mold, the pressure of the inert gas atmosphere is rapidly increased to push the molten metal from the sprue part to the product part, improving the bathing area. It is what makes them. If the bath is still insufficient, set the ceramic mold at the specified temperature (eg 1000 ° C).
By further using the above gas pressurization while heating to C), the bathing is further promoted.

Further, by installing a sensor on the surface or inside of the ceramic mold, it is possible to detect that a predetermined amount of molten metal has been injected and automatically and accurately perform the timing of gas pressurization immediately after that. , Very effective in actual operation.

[0006]

The main constitution of the present invention and the operation thereof will be described below with reference to FIG. Pressure container 1
A water-cooled copper crucible 3 containing a casting active metal 2 and a ceramic mold 4 are placed therein. A water-cooled copper coil 5 is wound around the water-cooled copper crucible 3, and a high-power current is supplied from the high-frequency power source 5a. When the casting metal 2 melts in a non-contact state with the water-cooled copper crucible 3 and reaches a predetermined temperature, the high-frequency power switch 5b is turned off, and the molten metal 2 is dropped from the pouring port 3b at the center of the bottom plate 3a, and then is poured onto the ceramic mold 4. Cast in. Immediately after the pouring is completed, the solenoid valve 7a from the inert gas tank 7 is opened, the pressure vessel 1 rapidly rises to a high pressure (for example, 3 atm), and the molten metal is pressurized from the sprue side to the product side. Improve the bathing area.

Depending on the shape of the cast product 4a, there may be a case where the hot water flow is still insufficient. At that time, the ceramic mold 4 is further heated to about 1000 ° C. by the heating furnace 6 built in the pressure vessel 1. While pressurizing the gas as described above. As a result, the cooling of the molten metal can be delayed, and the swirling can be further promoted.

Further, a sensor 4b for detecting that a predetermined amount of molten metal has been injected is installed on the surface or inside of the mold 4 and is electrically connected to the solenoid valve 7a, whereby the opening timing of the solenoid valve 7 is determined. That is, the timing of gas pressurization can be automated.

The inert gas tank 7 is connected to an inert gas cylinder 8 through a solenoid valve 8a, and the solenoid valve 8a receives a signal from the pressure gauge 7b to keep the pressure of the inert gas tank 7 in a constant range. Control.

[0010]

EXAMPLE Using the apparatus having the configuration shown in FIG. 1, 150 g of titanium-aluminum (TiAl) intermetallic compound, which is one of the active metals, was melted without contact with a water-cooled copper crucible, and the temperature was 1550 ° C. 2 diameter 53mm, height 27mm, minimum blade thickness 1mm
It was cast into a ceramic mold 4 for a turbocharger / hot wheel. At this time, the argon (A
r) The results of investigating the effects of pressurization and heating of the ceramic mold immediately after casting of the gas on the molten metal of the cast product are as follows.

When the mold was cast at room temperature without pressurizing the Ar gas, almost no hot water flowed to the thin blade portion. 1000 molds without pressurizing Ar gas
When casting was performed by heating to ℃, hot water turned to about 1/3 of the blade part. When the Ar gas was raised to 3 atm and the mold was cast at room temperature, the molten metal turned to about 2/3 of the blade part.
When Ar gas was raised to 3 atm and the mold was heated to 1000 ° C. for casting, the entire blade was molten.

[0012]

As can be seen from the results of the examples, by rapidly raising the pressure of the inert gas atmosphere immediately after casting the active metal melted in the non-contact state with the water-cooled copper crucible into the ceramic mold. , It is possible to greatly improve the bathing area of this cast product. In addition, if the mold is also heated as needed, the effect of further improving the bathing can be obtained.

It is possible to automate the timing of pressurizing the inert gas atmosphere by providing a sensor for detecting the injection of a predetermined amount of molten metal on the surface or inside of the mold.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing the main components of the present invention.

[Explanation of symbols]

 1 Pressure-resistant container (inert gas atmosphere) 1a Lid 1b Observation window 1c Exhaust valve 2 Molten metal 3 Water-cooled copper crucible 3a Bottom plate 3b Injection port 4 Ceramic mold 4a Cast product 4b Sensor 5 Water-cooled copper coil 5a High-frequency power supply 5b Switch 6 Heating furnace 6a Power source for heating furnace 7 Inert gas tank 7a Solenoid valve 7b Gas pressure gauge 8 Inert gas cylinder 8a Solenoid valve 9 Water tank G Inert gas W Water V Power source

Claims (3)

[Claims] 1. A casting method characterized in that an active metal is melted in a water-cooled copper crucible in a non-contact state, and the pressure of an inert gas atmosphere is rapidly increased immediately after casting in a ceramic mold. 2. The casting method according to claim 1, wherein the ceramic mold is heated to a predetermined temperature. 3. The casting method according to claim 1, wherein a sensor for detecting that a predetermined amount of molten metal has been injected is provided on the surface or inside of the ceramic mold.