JPH05261470A - Full mold casting method - Google Patents

Abstract

PURPOSE:To execute further smooth and quick gas venting at the time of pouring molten metal, to uniformize pressure in a mold and to prevent failure, such as collapse of molding sand, so as to prevent defect, such as casting blow hole, surface roughening, caused by defective ventilation, etc., in the cast product. CONSTITUTION:In a lost foam pattern 1 used for a full mold casting, plural venting vertical holes 3a-3c or horizontal holes are bored on the surface of the pattern and also venting passage 4 mutually communicating with the gas venting vertical holes 3a-3c or horizontal holes is formed on the surface of the same pattern. Then this lost foam pattern 1 is embedded into the sand mold 2 so that the vertical holes 3a-3c, horizontal holes and venting passage 4 connect to a exhaust hole 6 to execute the full mold casting, particularly, a reduced pressure casting.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a full mold casting process which is generally advantageous and utilized in the production of large castings.

[0002]

2. Description of the Related Art In general, a full mold casting method is produced by burying a vanishing prototype made of polystyrene foam or the like in a sand mold and injecting molten metal to vaporize and eliminate the vanishing prototype by its high heat. It is a casting method in which a molten metal is filled in the voids to form a cast product, and has been widely used in the field of casting technology, particularly in the production of large cast products.

While this casting technique has many advantages, it also has drawbacks, of which the major one is casting defects due to defective degassing. Gas is generated by vaporization of the disappearing prototype when pouring the molten metal, but if the removal of the gas is insufficient, the gas penetrates into the molten metal, and as a result, casting cavities, surface roughening, wrinkles in the molten metal, etc. Defects appear.

Therefore, as a method of solving this,
Conventionally, a method has been proposed in which a sand mold filled with dry sand that does not contain a breathable substance, especially a binder is used, and after burying the prototype, the molten metal is injected while depressurizing the sand mold to reduce the pressure in the sand mold. Have been used (see Japanese Patent Publication No. 43-7526).

However, according to this method, when the molten metal is poured, the internal pressure of the sand mold becomes uneven depending on the location due to the degree of decompression, and the mold sand in contact with the disappearing prototype collapses, which causes sand to bite and scoop the casting. However, there is a drawback that defects such as rough skin occur.

[0006] Conventionally, as another method for eliminating the degassing failure, a synthetic resin pipe is filled with a disappearing prototype,
Method to remove internal gas through the pipe
(See No. 49-22504), and a method to facilitate degassing by forming a ventilation path (hole) from the exhaust port of the sand mold to the inside of the disappearing prototype (Japanese Patent Publication No. 51-16016). Has been done.

[0007]

However, even with the above-mentioned various methods, casting defects may still occur due to defective degassing, and further improvement has been required for degassing. In particular, recently, the quality requirements for castings have become higher and higher, and the demand for improvement has increased. In particular, to prevent the mold sand from collapsing, the gas generated in the sand mold during pouring is further promoted to be dispersed and expelled.
There has been a demand for more uniform gas pressure in the mold.

The present invention has been made in view of the above circumstances, and an object thereof is to enable smoother and faster degassing without causing problems such as collapse of mold sand during pouring. Therefore, it is an object of the present invention to provide a disappearing master mold capable of producing a full-mold cast product free from defects such as casting cavities and surface roughness.

Another object of the present invention is to provide a full-mold casting method which makes it possible to produce a cast product by utilizing such a disappearing master without the above defects.

[0010]

DISCLOSURE OF THE INVENTION The present invention relates to a vanishing master used in a full mold casting method, in which a plurality of ventilation vertical holes or horizontal holes are formed on the surface of the vanishing master, and It is characterized in that air passages that connect the lateral holes to each other are formed on the surface of the prototype.

A plurality of ventilation vertical holes or horizontal holes are bored on the surface of the vanishing master formed in the same shape as the product to be cast, at appropriate intervals and positions. Since the molten metal is filled from below, if it is a vertical hole, a plurality of holes are used together for degassing. Therefore, the ventilation vertical hole is more preferable. This vertical hole is more preferably provided at a location where gas damage is likely to occur.

The ventilation vertical holes are formed by extending vertically.
It does not necessarily have to be a vertical hole, but may have an oblique hole shape depending on the shape of the disappearing prototype. On the other hand, in the case of the ventilation lateral hole, it is more preferable that the hole is formed obliquely instead of the horizontal hole because the gas flow becomes smoother.

Further, the ventilation vertical hole or the horizontal hole may be a through hole, or may be a hole which is not penetrated and is drilled up to a proper position inside the master. Further, the ventilation vertical hole or horizontal hole may be a round hole or a square hole, and may be a small hole or a large hole. The shape or size of the vertical hole or horizontal hole is arbitrary, but the number of vertical holes or horizontal holes is not limited. In addition, it should be determined in consideration of the amount of gas generation predicted from the size of the disappeared prototype, the foaming rate, and the like.

Ventilation passages are formed in the surface of the vanishing master so as to connect these ventilation holes or transverse holes to each other, and are preferably also formed so as to communicate with the exhaust port of the sand mold. The form and manufacturing method of the ventilation passage are not particularly limited, but for example, a groove is formed on the surface of the disappearing prototype at a position through which a ventilation vertical hole passes, and a film such as tape or paper is formed on the groove by appropriate work. The air passage can be easily formed by attaching the material to cover the groove. Moreover,
This method is advantageous because it does not cause any inconvenience in the subsequent application of the mold wash material.

The vent passage and the exhaust port are connected to each other by, for example, a vent plug made of a fusible substance similar to that of the prototype so as to be connected to each other.

As in the conventional case, the disappearing prototype itself is, for example, a polystyrene (PS) foam, a polymethylmethacrylate (PMMA) foam, a polyethylene (PE) foam, or the like which is made of a fusible substance. Can be applied to. In the case of PS foam, a foaming rate of about 30 to 40 times is used in ordinary casting, but a larger foaming rate (about 50 times) is used when casting a large size product. To be done. Although PMMA foam is a more preferable prototype material in terms of the amount of soot generated during vaporization, it is disadvantageous in that it is expensive.

The disappearing prototype of the present invention described above is
The full mold casting method can be generally used. That is, such disappeared prototype is embedded in a sand mold after surface coating of a coating material, and then a molten metal is injected into the sand mold, and the high temperature causes the disappeared prototype to vaporize and disappear, and to form the voids. By filling with molten metal, it is possible to make a cast product having the same shape as the disappearing prototype. Preparation of disappearance prototype (excluding the above),
For embedding in the sand mold, injecting the molten metal, and the like, conventionally used procedures and techniques can be used. There are no particular restrictions on the composition of the sand mold used, and the type and composition of the molten metal used.

In particular, the use of the disappearing mold of the present invention in the vacuum casting method is advantageous because degassing can be carried out more smoothly and quickly through the ventilation vertical holes and the like.

Therefore, according to the present invention, a plurality of ventilation vertical holes or horizontal holes are formed on the upper surface of the vanishing master made, and a ventilation passage is formed to connect the vertical holes or horizontal holes to each other, and the vanishing holes are eliminated. It is characterized in that a prototype is embedded in a sand mold so that a ventilation vertical hole or a horizontal hole or a ventilation path communicates with an exhaust port, and a casting is made by pouring a molten metal while depressurizing the mold if necessary. It is also related to the full mold casting method.

[0020]

In the present invention, by forming a plurality of ventilation vertical holes or horizontal holes and the ventilation passages connecting them in the disappearing prototype,
When full mold casting is performed using the vanishing master, the gas in the sand mold can flow through a plurality of ventilation vertical holes or horizontal holes and then through a ventilation path toward the exhaust port when pouring the molten metal. ..

Therefore, according to the present invention, the gas is smoothed,
Since it can be dispersed throughout the sand mold, guided to the exhaust port, and discharged to the outside of the mold, the gas pressure inside the mold becomes uniform throughout the mold, and the gas pressure value drops quickly to a low level. .. Therefore, full mold casting can be performed without causing gas venting failure and without causing collapse of the molding sand even in the vacuum casting method.

Moreover, the present invention allows the use of vanishing prototypes having a reduced weight by their volume due to the formation of a plurality of vent holes or transverse holes and vent passages, and thus the use of a lighter prototype. Therefore, the amount of gas generated can be reduced.

[0023]

EXAMPLES The present invention will be described in detail below with reference to examples.

As shown in FIG. 1, first, a vanishing master 1 having the same shape and size of a large product to be manufactured was made of polystyrene (PS) foam (foaming ratio about 50 times).

The prototype 1 is a block body having a stepped upper surface, and three ventilation vertical holes 3a, 3b, 3c, which are substantially vertical through holes, are formed on the upper surface of each step, and these ventilation vertical holes 3a are formed. Similarly, a ventilation path 4 for communicating 3c with each other is formed on the upper surface of the prototype.

As shown in FIG. 2, the ventilation passage 4 has a groove 9 formed in a P-shape.
It is formed by forming it on the surface of the prototype 1 of the S foam at a position where the ventilation vertical hole 3 passes, and by sticking an adhesive paper tape 10 on the groove 9 to cover the groove 9.

Next, a description will be given of the vacuum casting using the vanishing master 1 described above. First, a sand mold 2 (mainly composed of dry sand without using a binder) is prepared. This mold 2 has deaeration ports 11 ... around its side and is for vacuum casting.

After the mold coating material 12 is applied to the outer surface of the disappearing master mold 1, it is embedded in the sand mold 2 and, along with this, a runner 13 facing the master mold 1 is also provided. Further, an exhaust pipe 7 is provided as an exhaust port 6 immediately above the ventilation vertical hole 3a, and a ventilation plug 8 is fitted into each of the pipe 7 and the vertical hole 3a to connect the exhaust port 6 and the ventilation path 4 to each other. .. A synthetic resin pipe such as polyethylene, polyvinyl chloride, or polyamide was used for the ventilation pipe 7, and a pipe made of polystyrene (PS) foam similar to the prototype 1 was used for the ventilation plug 8.

That is, the gas is easily dispersed throughout the mold through the vertical holes 3a, 3b, 3c and the ventilation passage 4, and is discharged to the outside through the ventilation plug 8 and the exhaust port 6.

Thereafter, the port 11 is opened by depressurizing means not shown.
.. While degassing through depressurizing the inside of the sand mold 2,
The molten metal is injected from the pouring port 5 through the runner 13 into the disappearing master 1 surrounded by the mold sand, and the high heat causes the master 1 to vaporize and disappear, while filling the resulting voids with the molten metal.
We were able to make a large casting with the same shape as the vanishing prototype.

In the examples, castings could be produced without the appearance of defects such as casting cavities and surface roughening, which are caused by poor degassing and collapse of mold sand.

[0032]

As described above, according to the disappearing master of the present invention, in full mold casting including reduced pressure casting,
During pouring, smooth and quick degassing is possible through multiple ventilation vertical holes, horizontal holes, and ventilation passages, and there are no problems such as collapse of mold sand, and moreover, a lighter prototype By using it, an effect that the amount of gas generation can be reduced can be obtained.

Therefore, according to the full mold casting method of the present invention, the gas pressure in the sand mold becomes uniform over the entire mold, the gas is discharged quickly, and the gas generation amount is further reduced. There is an effect that satisfactory full mold casting can be carried out without causing collapse and the like, and thus a full mold cast product without defects such as casting cavity and surface roughness can be produced.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a sand mold before pouring in full mold casting using a vanishing mold according to an embodiment of the present invention.

FIG. 2 is a diagram showing a method for forming a ventilation path in the production of the disappearing prototype of FIG.

[Explanation of symbols]

 1 Disappearance prototype 2 Sand mold 3a, 3b, 3c Ventilation vertical hole 4 Ventilation path 5 Pouring port 6 Exhaust port 7 Exhaust pipe 8 Vent plug 9 Groove 10 Adhesive paper tape 11 Degassing hole 12 Coating material 13 Hot water passage

Claims (2)

[Claims] 1. A vanishing master used in a full-mold casting method, wherein a plurality of ventilation vertical holes or lateral holes are formed on the surface of the vanishing master, and the venting vertical holes or lateral holes communicate with each other. Disappearing master for full mold casting characterized in that the passage is formed on the surface of the same master. 2. A full mold casting method in which a molten metal is poured into a vanishing master in a sand mold to produce a casting, and a plurality of ventilation vertical holes or horizontal holes are formed on the upper surface of the vanishing master made and Forming a ventilation path connecting the vertical holes or the horizontal holes to each other, burying the disappearing prototype in a sand mold so that the ventilation vertical holes, the horizontal holes or the ventilation paths communicate with the exhaust port, and casting by pouring molten metal. A full-mold casting method characterized by making products.