JPH03230846A - Method for forming mold - Google Patents

Abstract

PURPOSE:To accelerate hardening of molding sand from neighborhood of position as the important point in order by inserting a permeable cylindrical body into an opened hole in a sand mold and introducing pressurized high temp. gas at end part of this permeable cylindrical body to harden the sand mold. CONSTITUTION:A pattern 2 for casting product is laid at center part on a base plate 1 and flask 3 is set at the outside thereof and the molding sand 4 is packed in inner part of the flask 3 to form the sand mold 5. Then, beforehand, a pipe-like holding member 7 is inserted at one end of the permeable cylindrical body 6 and this permeable cylindrical body 6 is expanded at the prescribed length. Successively, an insert bar 8 is inserted in the holding member 7 and pushed into the sand mold 5, which the greater is part is completed or the whole is completed, together with the holding member 7 and the permeable cylindrical body 6. After that, this permeable cylindrical body 6 and the holding member 7 are caused to remain in the sand mold 5 and only the insert bar 8 is pulled out. Then, the heated and pressurized gas is supplied into the inner part in the molding sand 4 through the permeable cylindrical body 6, and the sand mold 5 can be quickly hardened.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an improvement in a method of mixing a resin into foundry sand to form a mold and promoting hardening by heating the mold.

[Conventional technology]

In recent years, instead of so-called inorganic binders such as water glass-based and cement-based binders, furan resin and a catalyst that hardens this resin are used to form a sand mold, and the sand mold is left to stand at room temperature to harden. The furan process was developed and the use of organic binders such as furan resins to solidify sand molds has become increasingly popular.

This plan process was developed in response to the pollution problems that occur when old sand is disposed of, and the need to conserve resources due to the rising cost of silica sand for foundry sand.
This sand mold molding method is a closed system, which means that the molding sand can be reused, and it also reduces the total cost by improving productivity, shortening the finishing process, and increasing yield. This is extremely effective in improving the quality of castings.

However, in methods of curing foundry sand using organic binders such as the furan process, the curing speed is greatly affected by the temperature of the sand mold. Particularly in winter, when the temperature of the outside air is low, the temperature of the sand mold (mold) is also quite low, and in order to increase the curing rate, it is necessary to increase the temperature of the sand mold.

As a general means of adjusting the temperature of sand, in addition to the method of directly heating the sand before filling, methods of heating it from outside the casting flask are being considered. Since this is a conduction method, fully satisfactory results have not been obtained.

Therefore, especially in winter, the temperature required for curing cannot be maintained due to the heat dissipation after filling the molding flask with molding sand, resulting in a problem that the curing speed decreases significantly and curing does not progress sufficiently. .

In view of the above-mentioned problem that hardening does not proceed sufficiently due to the low temperature of molding sand, the present inventors have attempted to accelerate the hardening of the sand mold after filling the casting flask, especially in winter. For this purpose, we previously proposed an invention in Japanese Patent Application No. 63-211600 concerning a method for accelerating the hardening of foundry sand molds by forcibly injecting pressurized high-temperature gas into the sand mold.

In the invention, the inner wall of the casting flask for making the sand mold (the wall in contact with the molding sand) is formed of a perforated plate with a large number of small holes or a slit plate with a plurality of slits, and the mold is placed outside of this inner wall. Pressurized, high-temperature air is supplied to the space between the sand mold and the outer frame, and is injected into the sand mold through these numerous holes or slits.

[Problem to be solved by the invention]

However, in the conventional mold, ie, the external heating method of the sand mold, heat conduction is poor and it is not possible to heat the mold sufficiently to the inside. In particular, it takes a considerable amount of time to heat the sand from the side walls of the flask to the center of the sand mold, and this tendency becomes more pronounced when the sand mold is large.

In addition, the method previously proposed by the present inventors significantly shortens the time it takes for the sand mold to harden compared to the conventional external heating method, but it also requires pressurized high-temperature gas to be injected from the wall of the mold. Therefore, a small sand mold can fully exhibit its effect. However, when the sand layer becomes thick, gas cannot be sufficiently injected to the center of the sand mold, resulting in a problem that the time required for curing becomes longer.

[Means to solve the problem]

The present invention was obtained in order to solve the problems of the conventional technology, and is a method for hardening a foundry sand mold using a mixture of foundry sand and an organic binder, the method comprising: A method for molding a mold, in which a breathable cylindrical body is inserted into a hole opened in the sand mold, and pressurized high temperature gas is introduced into the end of the breathable cylindrical body to solidify the sand mold. be.

The method of pushing the breathable cylindrical body into the sand mold in the present invention is as follows:
There are two methods: (a) pushing a flexible breathable cylinder into the sand mold via a holding member, and (b) pushing a rigid breathable cylinder directly connected to the holding member. The end of the holding member is connected to a pressurized high temperature gas supply pipe. Then, pressurized high-temperature gas, particularly high-temperature air, is supplied from the gas supply pipe, and the gas is ejected into the sand mold from the air-permeable cylinder.

The optimal position for inserting the flexible, air-permeable cylinder into the sand mold is the open side, but it can also be inserted from the open side of the mold.

As the visible breathable cylinder, for example, a cylindrical string obtained by braiding synthetic fibers such as Saran, a cylindrical flexible string obtained by braiding glass fibers, etc. are most suitable.

Furthermore, a tube made of sintered metal can be used as the rigid breathable cylinder. Thereby, pressurized high temperature gas can be supplied into the breathable cylinder.

Heated air is the most suitable high-temperature gas to be supplied into the sand mold, and its temperature means the temperature at which the resin mixed in the molding sand can quickly harden. The size, number, insertion location, gas flow rate, etc. of the cylinders are determined in relation to the size of the casting.

[For production]

An air permeable cylinder is embedded in the surface of the sand mold that is open from the mold, or a hole opened in the side of the sand mold, at an appropriate place in the sand mold, and the end of the air permeable cylinder is pressurized and heated. Since the gas supply section is connected and the gas is supplied during crushing of the mold, the sand mold can be quickly hardened.

〔Example〕

Hereinafter, a method for molding a mold according to the present invention will be explained with reference to the drawings.

First, as shown in FIG. 1, a casting model 2 is placed in the center of a surface plate 1, and a casting flask 3 is placed outside of the model 2. Then, the inside of this flask (core/sheath) 3 is filled with molding sand 4. As the foundry sand, silica sand mixed with an organic binder such as furan resin and a hardening agent is used to form the sand mold 5.

After this sand mold 5 is completed, or at the stage of filling molding sand into the casting flask 3, an appropriate number of air permeable cylinders 6 are inserted into this sand mold 5 as shown in FIG. The sand mold 5 is pushed in so that the end thereof protrudes from the surface of the sand mold 5.

When inserting the flexible air-permeable cylinder 6 into the sand mold 5, (A) a tubular holding member 7 is attached to one end of the air-permeable cylinder 6 in advance.
is inserted to expand this breathable cylindrical body 6 to a predetermined length. Then, insert the insertion rod 8 into the holding member 7 into the sand mold 5, which is mostly completed or completed.
and push in together with the breathable cylindrical body 6. In this case, a portion of the holding member 7 protrudes from the surface of the sand mold 5. Thereafter, either the breathable cylinder 6 and the holding member 7 are left in the sand mold 5 and only the insertion rod 8 is removed, or (B) the breathable cylinder 6 is inserted into the holding member 7 and then further inserted into it. After inserting the rod 8 into the crusher, the insertion rod 8 is pulled out.

There is also a method (C) in which the rigid breathable cylinder 6 is directly connected to the holding member 7 and is pushed into a predetermined position. In any case, it is necessary to arrange a flexible, air-permeable cylinder 6 at a location within the sand mold 5 to which pressurized, high-temperature gas, especially air, is supplied.

Thereafter, as shown in FIG.
The gas supply pipe 8 is connected to a not-illustrated high-temperature/high-pressure heated gas, particularly a heated air supply device, to accelerate hardening by heating during crushing.

FIG. 4 shows a holding member 7 attached to the upper end of the flexible breathable cylinder 6.
Insert the insertion rod 8 into the air-permeable cylinder 6, push the air-permeable cylinder 6 into a predetermined position in an expanded state during crushing, and insert the upper end of the holding member 7 into the sand mold 5. It is shown protruding from the surface. FIG. 5 shows that after a part of the breathable cylinder 6 is inserted into the holding member 7, the insertion rod 8 is used to push the breathable cylinder 6 in an expanded state while crushing it, and a part of the holding member 7 is inserted. The figure shows a state in which the sand mold 5 protrudes from the surface of the sand mold 5.

The air-permeable cylinder 6 is a cylinder made by braiding synthetic resin fibers (bristle) such as Saran, cut into a predetermined length, and the distal end 6a of which is tied and sealed. The insertion rod 8 is used to push the breathable cylinder 6 into the sand, and normally it is pushed into the sand together with the breathable cylinder 6.
If the length of the air permeable cylinder 6 is quite long, insert a light guide rod with a smaller diameter than the insertion rod 8 to make a hole in the sand, and use the hole to insert the light guide rod into the air permeable cylinder 6. is pushed in with the insertion rod 8, and the holding member 7 is placed at the tip of the breathable cylinder 6.

In FIG. 6, a rigid air-permeable cylinder 6b, for example, a sintered metal cylinder, is connected to the tip of a tube 7a corresponding to the holding member 7, and this air-permeable cylinder 6b applies high-temperature and high-pressure heating into the sand mold. It is designed to introduce gas. In this embodiment, the flexible breathable cylinder 6 is not used, so the cost increases accordingly, but it is easy to insert the cylinder into the sand mold, and even a thin cylinder can be placed deeply. can be included.

Once the breathable cylinder 6 (6b) has been pushed into the sand mold 5 as described above, the insertion rod 8 is removed, the gas supply pipe 9 is connected to the holding member 7 as shown in FIG. From this, high-temperature, high-pressure heated gas is supplied to rapidly heat the vicinity of the cavity 2a.

〔Effect of the invention〕

The present invention is a method for curing a foundry sand mold using a mixture of foundry sand and an organic binder, in which a permeable cylinder is inserted into a hole opened in the sand mold. This method of molding a sand mold is characterized by solidifying the sand mold by introducing pressurized high-temperature gas into the end of the sand mold.

0- That is, a hole is formed at a predetermined position in the sand mold, a breathable cylinder is inserted into the hole, and heated and pressurized gas, especially air, is supplied to the inside of the molding sand through this cylinder. As a result, the hardening of the molding sand can be promoted sequentially starting from the vicinity of the important point, so even when the outside air is cold in winter,
Sand molds can be cured efficiently.

[Brief explanation of drawings]

Figures 1 to 3 are explanatory diagrams of the sand mold forming method, in which Figure 1 is a process diagram of filling the molding flask with foundry sand, and Figure 2 is a diagram of the process of filling the molding flask with molding sand, and Figure 2 is a diagram showing the process of filling the molding flask with molding sand, and Figure 2 is a diagram showing the process of filling the molding flask with molding sand. FIG. 3 is a diagram showing the connection between the air permeable cylinder and a pressurized high temperature gas supply source. Figures 4 and 5 are cross-sectional views showing the state in which the breathable cylinder is pushed into a sand mold, and Figure 6 is an explanatory diagram of a gas supply pipe using the breathable cylinder made of porous material. . 1...Surface plate 2...Model 3...Casting (
core/sheath) 5...sand mold 6.6b...breathable cylinder 7
, 7a... Holding member 8... Insertion rod 9...
・Gas supply pipe.

Claims (1)

[Claims] A method for curing a foundry sand mold using a mixture of foundry sand and an organic binder, comprising: inserting a permeable cylinder into a hole opened in the sand mold; 1. A method for molding a mold, which comprises hardening the sand mold by introducing pressurized high-temperature gas into the end of the sand cylinder.