JPH0422566A - Pressure diecasting process - Google Patents

Abstract

PURPOSE:To make the structure of a casting fine by supplying pressurized gas into the inside of a sand core to pressurize the molten metal and circulating the pressurized gas inside and outside the sand core to cool the sand core. CONSTITUTION:A casting mold 10 in which the sand core 18 is set is charged with the molten metal and this molten metal is pressurized by the compressed air supplied into a pressurizing cover 12 for pressure diecasting. The pressurized gas is supplied through a pressurized gas supply source 21, a supply passage 20 into the inside of the sand core 18. Then, the molten metal in the casting mold 10 is pressurized from the surface side of the sand core 18. Simultaneously, the pressurized gas supplied into the inside of the sand core 18 is circulated inside and outside the sand core 18 to cool the sand core 18. In this way, the molten metal is pressurized without deteriorating cooling properties in time of solidification of the molten metal.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an improvement in a pressure casting method in which molten metal filled in a mold is cast while being pressurized with pressurized gas.

(Prior art) When the pressure casting method described above is adopted, the pressurizing force of the pressurized gas acts effectively on the molten metal, so it is possible to produce castings with complex shapes, such as aluminum cylinder heads and cylinder blocks in engines. etc. can be cast without causing casting defects, and since there is no need to increase the pressing force too much, the burden on the mold is reduced, and there are advantages such as the ability to use a sand mold as the mold.

As the mechanism of strengthening casting materials and reducing casting defects due to pressurization of molten metal has become clearer, it has become possible to obtain cast products of excellent quality with less pressurizing force than before.

For this reason, as shown in Japanese Patent Publication No. 63-137564, after a vanishing model is buried inside a mold made of dry sand, molten metal is poured into the vanishing model, and after the filling of the molten metal is completed. , a method of pressurizing the molten metal in the mold by supplying pressurized gas to the mold, or published patent publication 1983
As shown in No. 501857, a mold made of dry sand is housed inside a pressurized container, the mold is filled with molten metal, and then pressurized gas is supplied to the inside of the pressurized container to fill the mold. Various pressure casting methods have been proposed, such as a method of pressurizing molten metal.

(Problems to be Solved by the Invention) However, each of these casting methods uses a sand core because the molten metal is pressurized with pressurized gas through the voids of dry sand, that is, the molten metal is pressurized from the outside. This is effective when there is no sand core, but when casting is performed by supplying molten metal into a mold in which a sand core is set, the pressure applied to the molten metal is not sufficient.

Therefore, the present inventor considered a method of supplying pressurized gas to the inside of the sand core to pressurize the molten metal from the surface side of the sand core, that is, from the inside of the molten metal.

However, when pressurized gas is supplied to the inside of the sand core, it becomes difficult for the heat of the molten metal, which conventionally escaped to the outside through the voids of the sand core, to be released to the outside.

As a result, cooling performance during solidification of the molten metal deteriorates, resulting in a new problem in that the internal structure of the resulting cast product becomes coarse and its quality deteriorates.

In view of the above, an object of the present invention is to make it possible to pressurize a molten metal from the inside without causing deterioration in cooling performance during solidification of the molten metal.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides a method for distributing pressurized gas inside the sand core by circulating pressurized gas inside and outside the sand core. The pressurized gas is used as a cooling medium.

Specifically, the solution taken by the present invention targets a pressure casting method in which a mold in which a sand core is set is filled with molten metal, and the filled molten metal is pressurized and cast. Pressurized gas is supplied to the inside of the mold to pressurize the molten metal in the mold from the surface side of the sand core, and the pressurized gas supplied to the inside of the sand core is circulated inside and outside of the sand core to melt the metal. The structure is such that the sand core is cooled.

(Function) With the above configuration, pressurized gas is supplied to the inside of the sand core to pressurize the molten metal filled in the mold from the surface side of the sand core, so the molten metal can be cast while being pressurized. .

Further, since the pressurized gas supplied to the inside of the sand core flows inside and outside the sand core, the heat of the sand core is released to the outside of the sand core by the pressurized air.

(Example) Embodiments of the present invention will be described below based on the drawings.

FIG. 1 shows the overall configuration of a pressure casting apparatus A used in an embodiment of the present invention for casting a bottomed cylindrical aluminum casting product having a flange.

In FIG. 1, reference numeral 10 denotes a fixed sand mold made of self-hardening sand made by mixing molding sand, for example, No. 6 silica sand with a resin hardening agent, and the fixed sand mold 10 has a shape corresponding to that of the cast product. A cavity 10a with a maximum diameter of about 120 mm and a mold coating agent applied to the inner surface, and a fixed sand mold 10 for pouring the molten metal.
A sprue 10b with a diameter of about 20 mm extends in the vertical direction to guide the mold into the inside, and a mold coating agent is applied to the inner surface of the sprue. A runner 10d with a diameter of about 10 mm extends downward and the inner surface is coated with a molding agent, and a runner 1
A diameter of 8 m that communicates 0d with the lower end of the cavity 10a.
It is equipped with a gate 10e of about m.

Above the sprue 10b of the fixed sand mold 10, a pressurizing lid 12 that can be raised and lowered is provided at the lower end of a pressurizing unit (not shown) supported by a robot.
is equipped with a pressurized gas introduction path (not shown) for guiding pressurized gas such as compressed air into the inside of the pressurizing lid 12.

Above the cavity 10a of the fixed sand mold 10, a movable sand mold 14 constituting the ceiling of the cavity 10a is disposed so as to be detachable from the fixed sand mold 10.
4 is provided with an appropriate number of eject pin insertion holes 14g.

A metal cylindrical joint member 16 is fitted into the center of the movable sand mold 10 and passes through the fixed sand mold 10 in the vertical direction, and the joint member 16 holds a sand core 18 at its lower end. As a result, the sand core 18 can be attached to and removed from the fixed sand mold 10 together with the movable sand mold 14. The lower end of the joint member 16 is tapered to facilitate removal of the sand core 18 during demolding after casting.

At the center of the joint member 16, there is a pressurized gas supply path 20 for guiding pressurized gas such as compressed air into the inside of the sand core 18.
is arranged to pass through the joint member 16, and the upstream end of the pressurized gas supply path 20 is connected to the pressurized gas supply source 2.
Connected to 1.

On the other hand, the downstream side of the pressurized gas supply path 20 extends to the lower end of the sand core 18 , and the pressurized gas guided by the pressurized gas supply path 20 is supplied to the inside of the sand core 18 at the downstream end. A nozzle 22 is attached that emits water to the air. Further, a pressure regulating valve 24 is interposed in the pressurized gas supply path 20, and the sand core 1
The pressure of the pressurized gas supplied into the chamber 8 can be kept constant. Furthermore, below the nozzle 22 inside the sand core 18, there is a temperature sensor 26 that detects the temperature of the pressurized gas that is discharged from the nozzle 22 into the sand core 18, absorbs heat from the sand core 18, and becomes high temperature. It is arranged.

Pressurized gas supply path 2 in the center of the joint member 16
A pressurized gas discharge passage 28 for discharging the pressurized gas released inside the sand core 18 to the outside of the sand core 18 is disposed coaxially with the pressurized gas supply passage 20 on the outside of the sand core 18. has been established,
The upstream end of the pressurized gas discharge path 28 is open at an opening 16a provided at the lower end of the joint member 16. Also,
The pressurized gas discharge path 28 includes a flow rate adjustment valve 30 that adjusts the flow rate of the pressurized gas flowing through the discharge path 28, and
A pressure sensor 32 detects the pressure of pressurized gas flowing through 8.
are provided respectively.

In addition, in FIG. 1, 36 is a CPU, and the CPU
36 inputs the temperature signal from the temperature sensor 26 and controls the flow rate regulating valve 30 of the pressurized gas discharge path 28 based on the temperature signal, and also inputs the pressure signal from the pressure sensor 32 manually to convert the pressure signal into the pressure signal. Based on this, the pressure regulating valve 24 of the pressurized gas supply path 20 is controlled.

Hereinafter, a pressure casting method performed using pressure casting method 8 having the above configuration will be explained.

First, with the pressure lid 12 raised, molten metal is injected from the sprue 1b of the fixed sand mold 10 to fill the cavity 10a.

Next, the cavity 10a is filled with molten metal, and then,
When the molten metal accumulates in the pool portion 10c, the pressurizing lid 12 is lowered to seal the sprue 10b.

Thereafter, compressed air of, for example, 2.5 atmospheres is introduced into the pressurizing lid 12 from the pressurized gas introduction path to pressurize the scene. In this way, in the initial stage of solidification of the molten metal, pressure is applied almost uniformly to the entire molten metal due to Pascal's principle, so the molten metal is pressed against the joint member 16, so that there is a gap between the joint member 16 and the sand core 18. Sealed.

In this way, the sand core 18 is sealed while being heated by the molten metal, so that the pressure inside the sand core 18 is increased to about 3 atmospheres.

Pressurizing the molten metal in this way requires a smaller device compared to the method of pressurizing the molten metal by supplying pressurized gas to the inside of the pressurized container.・Difficulty in timing with pressurization is resolved.

Next, compressed air is supplied from the pressurized gas supply path 20 to the inside of the sand core 18 to pressurize the molten metal from the surface of the sand core 18, while the compressed air inside the sand core 18 is discharged as a pressurized gas. Road 28
The inside of the sand core 18 is cooled by discharging it to the outside. In this case, the opening degree of the flow rate regulating valve 30 is adjusted based on the temperature signal from the temperature sensor 26 to maintain the internal temperature of the sand core 18 at approximately 100°C, and based on the pressure signal from the pressure sensor 32 Preferably, the pressure inside the sand core 18 is maintained at about 4.5 atmospheres by adjusting the opening degree of the pressure regulating valve 30.

In the above embodiments, the fixed sand mold 10 was used as the mold, or even if a metal mold was used instead, the pressure casting method of the present invention can be applied.

(Effects of the Invention) As explained above, according to the pressure casting method according to the present invention, pressurized gas is supplied to the inside of the sand core to pressurize the molten metal, while the gas is supplied to the inside of the sand core. Since the pressurized gas is circulated inside and outside the sand core, the heat of the sand core is released to the outside of the sand core by the pressurized air, so the molten metal can be cooled without deteriorating the cooling performance when the molten metal solidifies. Can be pressurized.

Therefore, according to the present invention, the structure of the obtained cast product can be refined even though a sand core is used.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a pressure casting apparatus used in an embodiment of the present invention. A... Pressure casting device 10... Fixed sand mold (mold) 18... Sand core 20... Pressurized gas supply path 24... Pressure adjustment valve 26... Temperature sensor 28... Pressurized gas discharge path 30...Flow rate adjustment valve and 1 other person

Claims (1)

[Claims] (1) A pressure casting method in which a mold in which a sand core is set is filled with molten metal, and the filled molten metal is pressurized and cast. The method is characterized in that the molten metal in the mold is pressurized from the surface side of the sand core, and the pressurized gas supplied to the inside of the sand core is circulated inside and outside of the sand core to cool the sand core. Pressure casting method.