JPS6251702B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a mold casting method, and particularly to a casting method in which molten metal is injected from below a mold.

BACKGROUND ART Conventionally, as a casting method in which molten metal is injected into a cavity from below a mold, a low-pressure casting method in which molten metal is pumped by air pressure, a casting method in which molten metal is pumped by an electromagnetic pump, etc. are known.

In these casting methods. During pouring, the air in the pouring passage leading from the pouring device to the mold cavity is discharged through the mold dividing surface and the passage formed by the ejector pin insertion hole and the ejector pin. The gap is set to less than 0.1 mm to prevent the injected molten metal from entering, and it is difficult to exhaust a large amount of air at once, and the pouring must be done at a low speed to prevent air entrainment. This causes various casting defects.

In other words, when molten metal is rapidly injected from a pouring device, the air in the cavity is not sufficiently discharged in response to the pouring, and the air and molten metal are not completely replaced, causing air to be drawn into the molten metal. This results in the formation of cavities within the product, or problems with hot water flow due to interference from residual air, making it impossible to cast into a predetermined shape.

Therefore, in order to prevent the above-mentioned casting defects from occurring, in the past, it was necessary to slow down the pouring speed and pour the metal while sufficiently exhausting the air in the pouring passage and cavity. The hot water time is getting longer and the processing efficiency is decreasing. In addition, there are methods to overcome these drawbacks, such as a vacuum casting method in which the inside of the cavity and the pouring passage are evacuated, and a casting method in which reactive gas is injected into the cavity and the pouring passage. In order to improve the properties, the casting equipment becomes complicated and expensive, and requires a large amount of reactive gas.

In view of the above, the present invention provides a device in which air in a cavity and gas generated from molten metal are discharged in response to pouring of metal through a ventilation path formed by an ejector pin insertion hole and an ejector pin, the ventilation path being provided. To provide a mold casting method in which the opening area of the molten metal is increased at the beginning of pouring to increase the amount of discharge.

EMBODIMENT OF THE INVENTION Hereinafter, an embodiment of a casting machine used in the method of the present invention will be described in detail based on the drawings.

Figure 1 shows a vertical mold casting machine 1 that opens and closes vertically.
2 is a movable upper mold consisting of an upper base 2a, an upper formwork 2b and an upper mold 2c, and 3 is a fixed lower mold consisting of a lower base 3a, a lower formwork 3b and a lower mold 3c. Both molds 2 and 3 form a cavity 4 into which molten metal is press-fitted. The movable upper mold 2 is connected and fixed to an upper base plate 5, and as the upper base plate 5 is reciprocated by a moving means (not shown), the movable upper mold 2 is moved up and down. On the other hand, the fixed lower mold 3 is connected and fixed to the lower base plate 6.

Reference numeral 7 denotes an ejector pin inserted into an ejector pin insertion hole 8 formed in the movable upper mold 2, and the upper end of the ejector pin 7 is connected to the ejector plate 9.
is slightly movably supported. The ejector pin insertion hole 8 has a lower end opening into the cavity 4, and is formed by a small diameter portion 8a provided near this opening and a large diameter portion 8b provided following the small diameter portion 8a, and the ejector pin insertion hole 8 is A ventilation path A is formed by the hole 8 and the ejector pin 7. The small diameter portion 8a is provided so that the clearance with the outer diameter of the ejector pin 7 is less than 0.1 mm, and the large diameter portion 8b has a clearance with the outer diameter of the ejector pin 7 of about 0.5 mm. It is set up like this. Furthermore, the small diameter portion 8a
As shown in FIG. 2, a guide 10 is provided at the connecting portion between the large diameter portion 8b and the large diameter portion 8b.

The guide 10 has a guide portion 1 as shown in FIG.
0a and a groove portion 10b, and the inner surface of the guide portion 10a is formed by an arcuate surface having the same diameter that is continuous with the small diameter portion 8a, and holds the tip of the raised ejector pin 7 concentrically with the small diameter portion 8a. It is something to do. In other words, the small diameter portion 8a and the large diameter portion 8b of the ejector pin insertion hole 8 are connected to the guide portion 10.
A groove 10 formed between the guides 10 except for a
They are communicated via b. Although only one ejector pin 7 is shown in FIG. 1, a large number of ejector pins 7 may be provided depending on the shape of the cavity 4. The guide 10 may be formed directly on the upper mold 2c, or may be formed by embedding a separate piece.

Further, 11 is a return pin connected to the ejector plate 9, which is connected to the ejector plate 9.
A hydraulic ram 12 is connected to the ejector pin 7.
operation is performed.

Next, 13 is a sleeve that communicates with the cavity 4 and opens at the bottom of the fixed lower mold 3. A pouring device (not shown) is connected to this sleeve 13 from below, and the molten metal is poured into the sleeve 13. It is introduced into the cavity 4 through the.

A molten metal detection means 14 is located in the middle of the sleeve 13.
A detector 14a is installed. The detector 14
A is composed of an electrode, which short-circuits and detects the molten metal when it comes into contact with the molten metal, and is placed at a predetermined position so as to activate the detection immediately before or when the molten metal enters the cavity 4 partially. has been done. Further, the molten metal detection means 14 is linked to a hydraulic ram 12 that operates the ejector pin 7,
It controls its operation. In addition, 15 is a sleeve cooling water channel, and 16 is a spot cooling water pipe.

Although not shown, a conventionally known pouring device is used. For example, a crucible containing molten metal is sealed, a pouring pipe inserted into the crucible is connected to the sleeve 13, and the above-mentioned pouring device is used. A pouring device that pressurizes the molten metal area in the crucible with compressed air and supplies the molten metal into the cavity 4 through a pouring pipe and sleeve 13, or a pouring device plunger that pumps the poured metal using an electromagnetic pump. A pouring device or the like that pumps the pouring metal by moving the molten metal is used as appropriate.

The cavity 4 in the above embodiment has an air pocket 4a recessed in the inner bottom surface of the upper mold 2c of the movable upper mold 2, and residual air is sealed in the air pocket 4a by pouring molten metal into the cavity 4. is configured to be

Next, to explain the casting method using the mold casting machine 1, the movable upper mold 2 is lowered and the mold is closed, and the molten metal is poured into the cavity 4 from below the molds 2 and 3 by the pouring device. inject. At this time, until the molten metal contacts the detector 14a of the molten metal detection means 14, the ejector pin 7 is raised and the tip of the ejector pin 7 is moved from the small diameter section 8a of the ejector pin insertion hole 8 to the large diameter section 8b to guide it. 10
The passage area of the ventilation path A is increased to vent the gas inside the cavity 4 and the sleeve 13 in a short time.

Subsequently, when the molten metal rises to a predetermined position and contacts the detector 14a, that is, just before the molten metal enters the cavity 4 or when it enters a part of the cavity 4, the ejector pin 7 is inserted so that its tip is inserted into the ejector pin insertion hole. 8 to match the cavity opening at the lower end of the small diameter portion 8a,
After reducing the opening area of ventilation passage A, cavity 4
Fill the entire interior with molten metal to complete pouring.

At that time, after the ejector pin 7 descends,
Air in the cavity 4 (including gas generated from the molten metal) is exhausted from the narrowed ventilation path A, the mold dividing surface, and the like. In addition, if the residual air is difficult to be completely exhausted due to the shape of the cavity 4, a gas reservoir 4a disposed near the ejector pin 7 is used.
This traps the air that is not exhausted outside the mold. This gas reservoir 4a not only has the function of trapping residual air, but also has a boiler function due to the pressure of the air sealed in this gas reservoir 4a.

After the molten metal injected into the cavity 4 solidifies, the movable upper mold 2 is raised to open the mold, and the ejector pin 7 is operated to protrude to release the product.

In the above embodiment, the movement of the ejector pin 7 in response to pouring of metal is linked by the detection operation of the molten metal detection means 14, but the movement of the ejector pin 7 is adjusted in relation to the operating time of the pouring device. They may be linked by a time control method, or any other appropriate linking means that is compatible with the method of the pouring device can be adopted.

Therefore, according to the present invention as described above, when pouring metal into the cavity in the mold, in the initial stage of pouring, the ejector pin is moved upward to enlarge the passage area of the ventilation passage, and the pouring device Since a large amount of air in the space from the mold to the cavity can be completely discharged in a short period of time, it is possible to improve the entrainment of air into the molten metal and poor molten metal circulation, and to increase the pouring speed. It is possible to shorten pouring time and improve overall processing capacity.

Furthermore, when the ejector pin is moved upward and then lowered in response to the injection of molten metal, the tip of the ejector pin that has been raised is held concentrically with the small diameter section by the guide, so that abnormalities may occur in the ejector pin and the small diameter section. No wear occurs, the clearance between the two is maintained as set without expanding, and when pouring, molten metal is prevented from entering the gap, preventing seizure and maintaining the ejector pin's operation well. Ru.

[Brief explanation of the drawing]

1 to 3 illustrate an embodiment of a mold casting machine used in the method of the present invention, in which FIG. 1 is a sectional front view of the main part, FIG. 2 is a detailed view of the part of FIG. 1, and FIG. 2 is a sectional view taken along the - line in FIG. 2. 1... Mold casting machine, 2... Upper mold, 3... Lower mold, 4... Cavity, 4a... Air pocket, 7...
...Ejector pin, 8...Ejector pin insertion hole, 8a...Small diameter section, 8b...Large diameter section, 9...Ejector plate, 10...Guide, 13...Sleeve, 14...Molten metal detection means, 14a... detector.

Claims (1)

[Scope of Claims] 1. A cavity formed by both molds is provided on the dividing surface of the upper mold and the lower mold, and an ejector pin insertion hole through which the ejector pin is inserted in the upper mold, and a ventilation path formed by the ejector pin. is opened in the cavity, and the ejector pin insertion hole is formed by a small diameter part provided near the cavity opening and a large diameter part provided following the small diameter part, and the ejector pin insertion hole is formed by a small diameter part provided next to the small diameter part, and the ejector pin insertion hole is formed by a small diameter part provided in the vicinity of the cavity opening and a large diameter part provided following the small diameter part. When pouring molten metal from below the fixed mold using a pouring device, the molten metal is poured into the cavity of the casting mold, which is equipped with a guide that holds the tip of the ejector pin that has moved upward in the connecting part concentrically with the small diameter part. Before entering the cavity, the ejector pin is moved upward, and just before the molten metal enters the cavity or when it has entered a part of the cavity, the ejector pin is moved downward so that its tip matches the cavity opening to complete pouring. A mold casting method characterized by the following. 2. The mold casting method according to claim 1, wherein the cavity has an air pocket, and residual air is trapped in the air pocket during pouring.