JPS623859A - Sealing method between stalk and metallic mold - Google Patents

Abstract

PURPOSE:To attain the prevention of the blowhole defect of a product, etc. by providing a flange having concentrical groove to the top end of a stalk, disposing a projecting part fitting into said groove to the bottom surface of a metallic mold and sealing the metallic mold via a packing and a melt of a low m.p. alloy. CONSTITUTION:A flange 11 is formed to the top end of the stalk 10 and the concentrical projecting part 12 is provided atop the same. The annular projecting part 13 concentrical with the axial center of the stalk 10 is provided to the bottom surface of a drag 1. The low m.p. alloy 15 is charged in the groove 12. The stalk 10 is raised by a cylinder 16, then the alloy 15 is melted by the temp. of the flange part 11 and is stored in the groove 12. The projecting part 13 of the drag 1 is immersed into the melt 15 to seal the atm. and the inside surface 10b of the stalk together with the packing 30 when the stalk 10 raises further. The molten metal 19 is raised in the stalk 10 and is packed into the cavity 4 by the above-mentioned method, by which the blowhole defect of the product is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a sealing method between a stalk and a mold for completely sealing the space between the stalk and the mold in a vacuum casting method.

[Prior art]

In the low-pressure casting method, even if air enters between the stalk and the mold, there is no problem that the quality of the product deteriorates. In the method of casting by connecting the mold cavity and molten metal with a stalk, reducing the pressure in the cavity, and sucking up the molten metal through the stalk, air intrusion from between the stalk and the mold affects quality. Therefore, it must be avoided. Therefore, in the vacuum casting method, various sealing methods between the stalk and the mold have been proposed, but these are not necessarily sufficient.

A widely used method is mold sealing, but it has the problem of being prone to defects due to gas generation.

[Problem that the invention seeks to solve]

As mentioned above, the present invention solves the sealing problem between the stalk and the mold, which was a problem in the conventional vacuum casting method, and makes the seal between the stalk and the mold perfect without causing gas defects. The object of the present invention is to provide a sealing method between a stalk and a mold, which makes it easy to attach and detach the stalk.

[Specific measures to solve the problem]

As a result of intensive research into specific means for solving the above-mentioned problems, the present inventors have discovered that a low melting point alloy is used in the flange formed at the upper end of the stalk as a sealing method between the stalk and the mold in the vacuum casting method. At the same time as loading, a refractory packing is provided between the flange portion and the mold on a concentric circle with the axis of the stalk, and a convex portion that fits into the groove of the flange is provided on the lower surface of the mold, and the refractory packing is placed between the flange portion and the mold. The present invention was completed based on the finding that the above problem was solved by sealing between the stalk and the mold using a melt of a low melting point alloy, and that the space between the stalk and the mold was completely sealed.

[Effect]

According to the sealing method between the stalk and the mold of the present invention, the low melting point alloy is turned into a molten liquid by the stalk heated by the molten metal, and the flange of the stalk and the mold come into contact with each other through the refractory packing, and the inside of the stalk is heated. The molten liquid of the low melting point alloy blocks the space between the surrounding surface and the atmosphere, and the refractory packing is compressed, reducing air permeability.This creates a complete seal between the stalk and the mold, preventing air from entering. Good quality cast products can be obtained. Further, since the book is sealed when the stalk is pushed up, the effect that the stalk can be attached and detached easily and easily can be obtained.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a vertical cross-sectional view of a vacuum casting machine that implements the sealing method according to the present invention, and FIGS. 2 to 4 are enlarged vertical cross-sectional views showing the sealing action between the stalk and the mold.

The lower mold 1 is placed on the upper surface of the leg 2, and the upper mold 3 is placed on the upper surface of the lower mold 1, and the upper mold 3 and the lower mold 1 form a cavity portion 4. The lower mold 1 may be a metal mold, and the upper mold 3 may be a metal mold or a sand mold. Further, the upper mold 3 is housed in a decompression chamber 5. The decompression chamber 5 is covered with a decompression chamber cover 6 to maintain airtightness, and is equipped with a vacuum pump 8.
The pressure is reduced by

The stalk 10 is made of cast iron or the like, and a ring-shaped concave groove 12 is formed on the upper surface of a flange portion 11 formed at the upper end thereof, which is concentric with the axis.

A ring-shaped convex portion 13 that is concentric with the axis of the stalk 10 formed on the lower surface of the lower die 1 faces the concave groove 12.
Furthermore, a low melting point alloy 15 is loaded.

A pair of hydraulic cylinders 16, which are an example of actuators for raising and lowering the stalk 10, are installed in a molten metal holding furnace 18, and the molten metal holding furnace 18 is filled with a light alloy molten metal 19. A rod 20 that slides in the vertical direction is housed in the hydraulic cylinder 16. A stalk holding plate 21 is fixed to the upper end of the rod 20, and a spherical washer 22 is fixed to the upper surface of the stalk holding plate 21. ing. A spherical convex portion 25 formed on the lower surface of the flange portion 11 of the stalk 10 with its center on the stalk axis is fitted into the spherical washer 23 formed on the upper surface of the spherical washer 22. The shaft portion 10a of the stalk 10 is loosely fitted into holes 22a and 21a formed at the center of the stalk holding plate 21.

On the upper surface of the flange portion 11 of the stalk 10, Kao wool paper (thickness 3 to 5 mm) 30, which is a type of refractory material packing in the shape of a hollow disc, is placed. The outer diameter is set to be smaller than the inner diameter of the recess 12 of the stalk 10 and larger than the diameter of the inner circumferential surface 10b of the stalk 10.

The melting point and boiling point of the low melting point alloy 15 are set lower than the melting point of the light alloy of the light alloy molten metal 19, and for example, a solder alloy or a bismuth alloy can be used as the low melting point alloy.

Next, the operation of the embodiment of the present invention will be explained.

What is shown in FIG. 2 is a state immediately before the stalk 10 is raised, with pressure oil being sent to the return side of the hydraulic cylinder 16 and the stalk 10 being brought to the bottom dead center. In this case, the temperature of the flange portion 11 of the stalk 10 increases considerably because the lower end of the stalk 10 is immersed in the molten light alloy 19. Therefore, the low melting point alloy 1 loaded in the recess 12
5 becomes a melt and is stored in the recess 12. A paper wool paper 30 is placed on the upper surface of the flange portion 11 so as to be concentric with the stalk axis.

Next, when pressure oil is sent to the push side of the hydraulic cylinder 16, the rod 20 projects upward and the stalk holding plate 21 rises, and the stalk 10 is moved as shown in FIGS. 1 and 3.
Kao wool vapor 30 is pressed against the lower surface of lower die 1 in a compressed state.

At this time, the convex part 13 of the lower mold 1 is immersed in the melt 15 of the low melting point alloy, and the atmosphere 32 and the stalk inner peripheral surface 10b are completely blocked off by the melt 15 and the convex part 13. In this case, the amount of melt 15 required for the above-mentioned shutoff is at least as small as not reaching the Kaowool paver 30, as shown in FIG.

In this state, a small gap (1 to 21i+) 33 is set between the upper surface of the flange portion 11 of the stalk 10 and the lower surface of the lower mold 1 facing the upper surface, and a decompression chamber 5
is in a state immediately before being depressurized by the vacuum pump 8.

What is shown in FIG. 4 is a state in which casting is being performed, and the pressure in the decompression chamber 5 is reduced by the operation of the vacuum pump 8. As a result, both the cavity portion 4 and the stalk inner circumferential surface 10b are depressurized. Then, the atmosphere 33 and the stalk inner peripheral surface 10
Due to the pressure difference between the melt 15 and the paper 30
As a result, the liquid level 15a on the outside of the protrusion 13 of the lower mold 1 is lowered than the initial state shown in FIG.

Furthermore, the melt 15 is drawn toward the Kaowool paver 30, but since the Kaowool paver 30 is under pressure,
Due to the resistance of the ceramic fiber, the stalk inner peripheral surface 10b
It doesn't flow into. Therefore, the atmosphere 32 and the stalk inner circumferential surface 10b are completely cut off. Thus, the light alloy molten metal 19 rises along the inner peripheral surface 10b of the stalk 10b and fills the cavity 4 with no pressure leakage between the stalk 10 and the lower mold 1.

Nao, the stalk 10 does not need to be replaced until it reaches the end of its service life due to erosion, etc., and therefore the Kao Wool Barber 3° does not need to be removed during that time either. The life of the stalk 10 is made of iron and is approximately 1,400 pieces cast. If the stalk 10 deteriorates as the number of pieces cast increases, the stalk 10 is lowered by 1° using the hydraulic cylinder 16 and the molten metal holding furnace 18 is moved. Simply pull out the stalk 10 and replace it. In addition, some low melting point alloy melt 1 passes through the Kao Wool Baba 30.
5 may enter the light alloy molten metal 19, which is the melt of the cast metal, since the low melting point alloy 15 is generally a relatively important alloy, it will not fall downward and mix into the cavity portion 4. . Furthermore, the actuator is a hydraulic cylinder 16
Please be limited to.

(An air cylinder may also be used.)

〔effect〕

According to the sealing method between the stalk and the mold of the present invention, the molten liquid of the low melting point alloy stored in the flange of the stalk and the refractory packing placed on the flange create a gap between the stalk and the atmosphere. Since gas is completely blocked, airtightness between the stalk and the mold can be easily maintained, and stable and good products without gas defects can be obtained. Furthermore, since the stalk can be easily replaced by operating the actuator, the number of man-hours required for the stalk replacement work can be significantly reduced.

[Brief explanation of drawings]

FIG. 1 is a vertical cross-sectional view of a vacuum casting machine that implements the sealing method according to the present invention, and FIGS. 2 to 4 are enlarged vertical cross-sectional views showing the sealing action between the stalk and the mold. 1.3...Lower mold and upper mold that constitute the mold, 4...
Cavity part, 10... Stoke, 11... 7 lange part, 15... Low melting point alloy, 18... Molten metal holding furnace,
19... Molten metal, 30... Kao Wool Beba.

Claims (2)

[Claims] (1) A vacuum casting method in which the cavity part of a mold provided above the molten metal holding furnace and the molten metal are connected by a stalk, the pressure in the cavity part is reduced, and the molten metal is sucked up through the stalk and cast. In the sealing method between the stalk and the mold, a flange having a groove concentric with the stalk axis is provided at the upper end of the stalk, the groove of the flange is filled with a low melting point alloy, and the flange portion and the A refractory packing is disposed between the molds, and a convex portion is provided on the lower surface of the mold to fit into the groove of the flange, and the molten material of the low melting point alloy extruded by the convex portion and the packing are used to connect the stalk and the metal. A sealing method between a stalk and a mold, which is characterized by sealing between the molds. (2) The refractory packing is a ceramic fiber formed into a hollow disc shape that is smaller than the groove of the flange and larger than the inner diameter of the stalk and is concentric with the stalk shaft. Sealing method between stalk and mold.