JPS62203661A - Casting device for metal - Google Patents

Abstract

PURPOSE:To quickly substitute the air in a casting mold with a molten metal and to finish a casting to the good quality even in the fine parts thereof by pouring the heated molten metal in a pressure variable vessel into the casting mold which is gently applied with fine oscillation under the reduced pressure and pressurizing the inside of the vessel after pouring. CONSTITUTION:The metal in a crucible 15 of a melting device 14 in the pressure vessel 11 in which the reduced pressure is maintained is heated and melted by a high-frequency coil 16. The crucible 15 is tilted to pour the molten metal into the casting mold 19 which exists on a U-shaped metallic plate 1 and is oscillated at about 0.1-1.0mm amplitude and about 30-120Hz oscillation frequency by an electromagnetic coil 2. The molten metal is quickly and thoroughly substd. with the air in the cavity 20 of the casting mold 10 by such oscillation. The amt. pressure in the pressure vessel 11 is thereafter pressurized to about 1-4kg/cm<2> to solidify the molten metal. The molten metal is filled even to the fine parts of the cavity 20 in the casting mold 19 and the quality of the casting product is improved by the subsequent solidification under the pressurization.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a casting device, and more specifically, a method for pouring metal into a mold under reduced pressure and applying vibration to the mold to reduce defects around wA. The invention relates to metal casting equipment.

[Conventional technology] Generally, in the lost wax casting method, molten metal is cast by gravity into stacked thin-walled molds (ceramic, shell mold), but small castings with complex shapes and thin walls have a high incidence of "poor flow". Because of the high pressure, artificial pressure is often applied to the molten metal using block molding.

Still, such small castings (e.g. 0.3am thick)
, Width 51101% Length 15In @) "Defect around S"
Due to the high incidence of defects, it has become a problem to improve the yield and the quality by preventing internal and external defects.

Regarding casting ability to improve yield, items such as assembly plan, alloy composition, mold temperature, casting temperature, pressure rise angle, maximum pressure value, mold air permeability, etc. are centrally managed. There is.

Among these, the air permeability of the mold is known to be important because it contributes to the influence of casting ability.

Air permeability means that the air and gas in the mold cavity are discharged through the permeable mold wall, but they are also discharged from the spool (runway), which is an artificial vent or passage for the molten metal. However, if air and gas are not sufficiently exhausted, they will be compressed and may enter the molten metal or create back pressure, which will significantly affect the molten metal injection speed. As a result, this causes external defects (poor water circulation) and internal defects (internal defects).

Therefore, the assembly plan, mold defect distribution, type of binder, liquid mixture ratio, directionality of mold temperature, pressure, gas, etc. are controlled, but in conjunction with other conditions, they can be understood numerically during actual work. This has become an extremely difficult problem.

It is said that pouring should be done quietly and quickly, but this is because when pouring molten metal too vigorously, the laminar flow turns into turbulent flow, which can cause engulfment and collapse. Casting is commonly performed.

However, for the reasons mentioned above, artificial pressure is indispensable for small castings, and many attempts have been made to find out how to "quietly" pour the metal. The pressure method will be explained.

One of these methods, the centrifugal casting method, has been used for a long time.To explain its structure, a melting device and a mold face each other, and a balance weight is installed at one end of a bar and a balance weight at the other end. When driven in rotation, the molten metal flies out of the crucible of the melting device due to inertial motion, collides with the sprue of the mold, and is injected into the mold, filling the mold cavity with continuous centrifugal force. It is extremely simple and easy to apply pressure.

The feature of this method is that the flying molten metal bounces at the sprue of the mold, and the air in the cavity is not affected by centrifugal force, so it can be discharged from the mold wall or passed backwards through the runner to the sprue. is discharged to the outside.

Therefore, it is extremely unaffected by the air permeability of the mold, and there have been reports that it is possible to cast at a high pour rate even in molds without air permeability.

Therefore, the incidence of problems such as poor circulation is extremely low, and it is possible to cast any medium or high-grade alloy, but on the other hand, the assembly method is determined by the direction of centrifugal force, making pressure control difficult to manage. The disadvantage is that the occurrence of defects due to turbulence is high.

In order to correct these shortcomings, there is a pressure casting method. An example thereof will be explained using FIG. 2 (ω, (b)).

This pressure casting device 10 includes a melting device 14 that includes a melting crucible 15 and a high-frequency heating coil 16 in a pressure vessel 11 provided with a viewing window 12 and a pressurizing port 13 as shown in FIG. 2 (J). A mold 19 is vertically disposed on a stand 18 on a screw shaft 17 so that its installation position can be varied.

First, a small or medium alloy is placed in the melting crucible 15 and a high frequency current is passed through a high frequency coil to heat the heating source 16 to melt the alloy in the crucible. Next, the preheated mold 19 is placed on the table 18. After the air is exposed to air, the lid of the pressure vessel 11 is opened, and the air inside is sucked out from the pressurization port 13 to remove the pressure vessel 11.
After reducing the pressure inside the mold and reducing the back pressure resistance inside the mold,
), after the melting crucible 15 is overturned and the molten metal is gently poured into the mold from the sprue of the mold 19 by gravity, heated air is blown into the pressure vessel 11 from the pressurizing port 13 to increase the internal pressure of the vessel. Raise it and perform casting.

The advantages of this method are that there is little turbulence in the molten metal and there is no directionality in the pressure, so there is a degree of freedom in the assembly method, and the pressure rise angle and pressure peak value can be controlled arbitrarily, so it is the most popular method for casting middle-layer alloys. It is.

[Problem to be solved by the invention] However, although this method has very few internal defects, it is difficult for air to escape through the runner side when the sprue is filled in the cavity, so the air permeability of the mold is affected. Starting with control, mold temperature,
It is necessary to control the casting temperature.

Furthermore, many problems have been pointed out in this pressurizing method today, such as a high incidence of external defects in high melting point alloys, alloys with a narrow solidification temperature range, and platinum and titanium alloys with high viscosity coefficients.

[Purpose of the Invention] The purpose of the present invention is to solve the above-mentioned drawbacks associated with the pressure casting method, and to make the most of the characteristics of the pressure casting method and to suppress the occurrence of defective products to produce high-quality castings. The present invention provides an apparatus for obtaining the results.

[Summary of the Invention] In order to achieve the above object, the casting apparatus of the present invention melts a material metal in a pressure-reduced pressure vessel, and then melts the molten metal while applying slight vibrations to a preheated mold in the vessel. The purpose of this method is to pour metal into the mold, and after completing the pouring, pressurize the inside of the pressure vessel and continue the vibration applied to the mold until the molten metal in the mold solidifies. The mold equipment of the invention includes a variable pressure container capable of adjusting internal pressure, a metal melting crucible housed in the container and heated by a heat source, and a preheated mold placed in the container that is subjected to slight vibrations. It consists of a low-frequency vibration adding device.

[Embodiments of the Invention] In order to carry out the metal casting apparatus of this invention, FIG. 1 (ω,
As shown in +b), the lower plate at one end of the magnetic and elastic metal plate 1 bent into a U-shape and the core 3 around which the coil 2 is wound are stacked on the inner bottom of the pressure vessel 11 and fixed with bolts 4. Then, a vibration adding device 8 is attached to the upper plate of the metal plate 1, in which a mold mounting table 6 is fixed with bolts 7, and a mold mounting base 6 is formed with a mounting flange 5 that protrudes in accordance with the mold so that the mold 19 can be fitted on one side of the upper plate of the metal plate 1. This is carried out using a high-melting point metal casting apparatus in which an alternating current or pulsating current is applied to the coil through a conductive wire 9.

[Operation of the Invention] The high melting point metal casting apparatus of the present invention is constructed as described above, and the casting method of the present invention will be described below using this apparatus.

First, before starting the method of this invention, it is important to note that in the pressurized method, the cavity is sealed when the melt 1a is poured into the sprue, so the air in the mold-like cavity is extremely unlikely to be discharged to the runner side, as in the centrifugal method. In casting low and high melting point alloys, the mold temperature is high < (
900-1600℃) As a result, the surface layer inside the cavity is sintered by the binder, reducing air permeability and preventing high-temperature molten metal (
Due to the sudden expansion of air caused by 1,650 to 1,900°C), the discharge from the mold wall was significantly impaired, resulting in a large back pressure resistance, which was the cause of a decrease in the casting rate of high melting point alloys.

In addition to the conventional pressurizing method, this invention applies vibration energy to the mold 19 via the vibration adding device 8 before casting to vibrate the mold 19, thereby removing air in the cavity 20 of the mold 19 from the sprue. It is characterized by quickly displacing the molten WAa that penetrates into the cavity 20, thereby reducing the back pressure resistance within the cavity 20, increasing the casting ability, and obtaining a fine cast product with a beautiful finish. In other words, the gist of the present invention is that the cavity 2
The air in the 0 will be actively and quickly removed from the sprue.

Next, a casting method having such characteristics will be explained step by step.

During casting, compressed air is injected into the pressure vessel 11 from the pressurizing port 13 to a depth of 97 cm, and the metal (high melting point metal) placed in the melting crucible 15 in the pressure vessel 11 is heated by a high frequency heating coil. The heating source 16 is heated and preheated by applying an electric current, etc., and the inside of the pressure vessel 11 is heated by 40 to 65 tlQ1 to the mold 19, which is placed on the mold mounting table 6 of the vibration adding device 8.
The molten metal obtained by melting it under reduced pressure to 0++ is applied to the mold 19 with an amplitude of 0.
The metal is poured while applying vibrations of 1 to 1.0 m and a frequency of 30 to 120 Hz, and after pouring, the inside of the pressure vessel 11 is heated to 9/a from 1 to 4.
The vibration and the pressure inside the container are maintained until the molten metal poured into the mold 19 solidifies, and when the solidification is finished, the pressure inside the container is returned to atmospheric pressure, the vibration applying device 8 is stopped, and the mold is removed. Take out No. 19 from the container.

As the vibration applying device 8, in addition to the electromagnetic type in the above embodiment, a motor drive cam or a crank type mechanical vibration applying means can of course be used in the present invention.

[Effects of the Invention] As described above, the present invention provides a variable pressure container capable of adjusting internal pressure, a heating source such as a high frequency coil housed in the container, and a metal melting crucible heated by the heating source. , and a low-frequency vibration adding device that applies minute vibrations to the preheated mold placed in the container, so that when the molten metal is poured into the sprue, the air inside the cavity is blown away by the vibration of the inner surface of the cavity. Since it is quickly removed from the sprue to the outside through the side and quickly replaced with molten metal, the back pressure caused by the air inside the cavity does not interfere with the inflow of molten metal as a counter pressure, and even high-melting point metals can be cast quickly and finely. The inflow speed is proportional to the pressing force and the degree of vibration, so casting with beautiful detailed finish is easily performed, and the structure is simple.

[Brief explanation of drawings]

Figures 1(a) and 1(b) are block diagrams of the main parts of a high-melting point metal casting apparatus, which is an embodiment of the present invention, respectively, and Figure 2(ω) and Figure 2(b) are It is a diagram showing the configuration and casting process of a conventional pressure casting apparatus for carrying out the invention. 8... Vibration adding device, 11... Variable pressure container, 14
... Melting device, 15... Metal melting crucible, 16...
・Heating source such as high frequency coil, 19...Mold. Figure 1 (mu) i71igI salary) Figure 2 (of) gIJ2 figure (()

Claims (1)

[Claims] A variable pressure container that can adjust the internal pressure, a heating source such as a high frequency coil housed in the container, a metal melting crucible heated by the heating source, and a preheated mold placed in the container. 1. A metal casting device comprising: a low-frequency vibration adding device that adds minute vibrations.