JP3425527B2 - Manufacturing method of frozen mold and its storage method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a frozen mold and a method for storing the frozen mold, and more particularly to a frozen mold frozen with cooling air by a refrigerator.

[0002]

2. Description of the Related Art A casting refractory alone or a refractory containing additives is mixed with a predetermined amount of water and frozen to produce a casting mold.
No. -30107, etc. Conventionally, in order to obtain a high-strength mold for this purpose, it is considered that it is necessary to use frozen ice in a supercooled state, rather than normal ice gradually frozen at 0 ° C. A liquefied gas such as nitrogen or a refrigerant such as dry ice is used.

As a method for cooling the mold more rapidly to obtain a high-strength mold, a method using initial freezing and finish freezing (Japanese Patent Publication No. 63-19253) and a method of pre-cooling the molding sand in advance (Japanese Patent Publication No. 59-2575).
There is a method of sufficiently cooling a casting frame, model, model plate, etc. (Japanese Patent Publication No. 63-1145). As a method of circulating the refrigerant into the mold by suction or blowing,
Blowing the refrigerant through a pipe or the like (Japanese Patent Laid-Open No. 56-15
4248), and circulate in the mold by suction (JP-A-57-28653 and JP-A-57-106444.
JP-A-57-149045) and the like. The most commonly used method for producing a frozen mold is to immerse the mold in a liquid nitrogen solution, and any of the above methods allows a liquefied gas to flow through the mold. However, all of these methods discharge the refrigerant without reusing it.

When the frozen mold comes into contact with the atmosphere, supersaturated water vapor rapidly adheres to the mold, and it is known that a frost phenomenon that causes a casting defect. Method for coating the product shape part of
-4218).

[0005]

By the way, when liquid nitrogen or the like is used as a coolant for cooling a frozen mold, the mold may be -100 ° C. or less, and all of the casting equipment causes frostbite. It is dangerous to the human body because it becomes so cold. The present invention relieves the worker from such dangerous work and makes it possible to produce a strong mold at a low temperature of a refrigerator. In order to make a strong mold using a refrigerator, it is necessary to make the temperature of the air flowing into the heat exchanger as low as possible. It is also necessary to study what the cooling rate of the mold should be. If the differential pressure due to suction or the like is increased too much to increase the cooling rate, the movement of water in the mold will occur, which eventually forms a water condensation layer and impairs the air permeability of the mold and prevents freezing. Become.

When the frost phenomenon occurs on the side of the product shape portion in the mold, it appears as a phenomenon such as rough skin, pinholes, and blowback of hot water when pouring. This frosting phenomenon occurs instantly when the outside air with high humidity comes into contact with the mold. It is known that such a frosting phenomenon occurs in various processes such as die-cutting work, coating work, core work, mold matching work, mold preservation, and pouring work. It is no exaggeration to say that the frost phenomenon is the main reason why the freeze mold casting method is not popular. Further, according to the method of Japanese Patent Publication No. 59-4218, not only is the coating time-consuming, but it is difficult to completely seal it. Further, there is no idea about the method of storing the template after the freezing, since the main purpose is to freeze the template at -70 ° C or lower.

Storage of frozen molds and manual work in a cooling atmosphere have not been possible with the conventional method using liquid nitrogen or the like. This is because storage is too expensive and the cooling temperature is too low to allow people to work. For this reason, in the past, it was necessary to pour molten metal immediately after freezing and to completely automate the molding process.

[0008]

In order to solve the above-mentioned problems, the present invention is a freezing mold manufacturing method for manufacturing a mold by freezing water containing foundry sand, which comprises 1 to 12% by weight of water.
Suitable for use in a closed system that circulates low-temperature air of -3 ° C or less , which is formed of foundry sand containing water and cooled by a refrigerator.
The cold air was collected after once is circulated into a mold which is arranged at, and cooled through a heat exchanger of the refrigerator times
The yield cold air is circulated again into said mold, it was decided to freeze the mold by cold air circulating in the closed system. It is preferable that the low-temperature air be circulated in the mold under a pressure difference such that the water contained in the mold does not move in the mold.

In order to further reduce the temperature, it is advisable to insert a heat pipe into the mold. If this heat pipe is inserted in a place where low temperature air does not flow much due to the model, the freezing of the mold can be further promoted.

The frozen mold was worked in a refrigerator dehumidified by a refrigerator at a dew point of 10 ° C. or lower.

Any one of liquefied gases of nitrogen, carbon dioxide, and helium, or a refrigerant in which they are used in combination, may be mixed and circulated in the low temperature air. It is also preferable to spray this refrigerant directly on the surface of the foundry sand or on the fin portion of the heat pipe in terms of accelerating freezing.

When sufficient hardening cannot be obtained only by freezing the water, or when temporary fixing is required in the initial stage, a suitable amount of additives for hardening may be included in the foundry sand. However, the amount is within the range that does not hinder the reuse of the foundry sand.

When storing the frozen mold,
It was decided to store the mold in a freezer that was cooled to 0 ° C or less by a refrigerator.

[0014]

Since no refrigerant such as liquefied nitrogen is used, problems such as frostbite are eliminated, and a person can work in a cooling atmosphere. By using the air cooled by the refrigerator and recirculating it,
The mold can be manufactured more efficiently and at lower cost than when liquid nitrogen or the like is used. The moisture condensation layer due to the movement of moisture in the mold is not formed, and the mold is frozen uniformly. Since the refrigerator generally has a dehumidifying effect, the freezer is automatically dehumidified. For example, the amount of water contained in air at 25 ° C is about 23.8 g / m3, but 0 ° C
Since the amount was only about 4.8 g / m3, the frost phenomenon of the mold disappeared, casting defects did not occur, and the mold could be stored for a long time. If there is a problem in the working environment at 10 ° C. or lower, the working environment can be secured by quickly working in a closed chamber in which cooled air is heated with a heater.

[0015]

EXAMPLE An example of a method for producing a frozen mold according to the present invention will be described.

Example 1 A freezer was used to freeze a system shown in FIG. Reference numeral 2 in FIG. 1 is a model made of a tree shape, and has several holes 6 formed in the vertical direction. The model 2 is attached to the upper surface of the surface plate 4 and communicates with the ventilation portion 8 and the hole 6 formed inside the surface plate 4. The periphery of the surface plate 4 is covered with a molding frame 10, and the molding sand 3 is put into the molding frame 10 and tamped.

The casting sand 3 is made of No. 5.5 silica sand, and the silica sand 1 is used.
4 wt% of water was added to 100 parts by weight and kneaded. The amount of water added is preferably 1% by weight to 12% by weight . If the amount of water added is 1% by weight or less, sufficient strength cannot be obtained during freezing, and a mold can not be formed . On the other hand, the amount of water added is 12 fold
If it exceeds the amount %, an explosive reaction will occur when the molten metal comes into contact with water, and blowback will occur during pouring, making it impossible to pour, and the product will also have pinholes, rough skin and other casting defects caused by moisture. Occurs.

The upper portion of the casting frame 10 is covered, and the air guide tube 12 is connected to the center thereof. The air guide tube 12 is connected to the ventilation section 8 via a fan 14 and serves as a circulation path. The freezer 1 is provided in the middle of the air guide tube 12,
The air passing through the air guide tube 12 is cooled by the cooling unit 16. The fan 14 sucks the sucked gas at a suction pressure such that the water layer in the molding sand 3 does not move, and sends the sucked gas to the cooling unit 16 of the refrigerator 1 to cool and recirculate the gas into the mold.

As described above, as a result of the system in which the air once cooled by the refrigerator 1 circulates in the system isolated from the outside, the energy efficiency of the cooling air becomes 80% or more, and the inside of the mold rapidly. It is possible to cool. That is, instead of ice having a low strength gradually cooled at 0 ° C., water having a high strength obtained by supercooling water can be obtained, and a frozen template having a high strength can be obtained. It is considered that the lower temperature air circulates in the system, which causes a synergistic effect.

By the way, when the cooling air is exhausted from the air guide tube 12 to the outside of the system, room temperature air outside the system is taken in, so that the energy efficiency is extremely lowered and the mold strength is remarkably reduced. descend. Spraying liquid nitrogen from the pipe 20 to a part of the air circulation path further increases the cooling rate of the mold, and is effective as an auxiliary cooling means.

The mold thus frozen is subjected to die cutting work, core work, mold matching work, etc. in a freezer.
With a cover 22 made of extinguishable polystyrene foam as shown in FIG. 3, cover the part where the product part inside the mold communicates with the outside world.
It was left in the freezer for a day and then poured. As a result, a cast product having a beautiful cast surface without defects was obtained. When a wooden lid, which was not extinguishable, was used, the lid was removed immediately before pouring, but defects such as rough skin occurred due to the phenomenon of frost. There is no problem of frosting if die cutting work, core work, mold matching work, etc. are performed in a dry chamber, but it is preferable that ice does not melt at 0 ° C.
The following is desirable. In order to improve the working environment, the inventors of the present invention re-heat the air once cooled to 0 ° C. or less in the refrigerator.
I tried to work quickly in a closed cabinet that was warmed to 4 ° C to 10 ° C with a tool etc., but no problem occurred.

According to experiments conducted by the inventors, when the amount of water contained in 1 m3 of air exceeds about 10 g, frost in the mold causes blowback at the time of pouring, pinholes of the product, rough skin, etc. Casting defects due to moisture begin to appear. That is, this is the amount of water contained in the air having a dew point of 10 ° C. If the amount of water is less than this, even if the air is at a temperature of 10 ° C. or more, the problem of casting due to frost does not occur. Therefore, if there is a problem in the working environment at 10 ° C. or lower, the cooled air is heated by the heater and then allowed to flow into the closed chamber, and the work is quickly carried out therein.

FIG. 2 shows another embodiment.

In this embodiment, a chamber 30 is provided in the path through which the frozen air circulates, and the casting frame 10 is placed in the chamber 30. Although only one flask 10 is shown in FIG. 2, a plurality of flasks can be installed, and each of the flasks 10 is individually provided with a suction fan 15. Flask 10
The model 5 arranged inside is a vanishing model, no suction hole is provided, and a suction hole 13 is provided in the entire surface plate 4.
The fan 15 is connected to the ventilation part 8 formed in the surface plate 4, and the cooling air flows through the molding sand 3 by the suction of the fan 15 and is discharged from the fan 15. The discharged air is
It is sucked by the circulation fan 14 and sent to the refrigerator 1, cooled, and sent again to the flask 10.

Reference numeral 40 is a heat pipe, which is inserted into the mold substantially at the center thereof. As shown in FIG. 5, the heat pipe 40 is provided with a plurality of fins 41 on the upper portion thereof, and the fins 41 radiate the heat absorbed by the lower heat absorbing portion.

Also in this embodiment, the cooled air is circulated in one limited system. In that case, the position of the fan 14 for air circulation may be arranged on the upstream side of the refrigerator 1 as shown in FIG. 1 or on the downstream side of the refrigerator 1 as shown in FIG. Even if they were placed, there was no big difference in the freezing situation. Further, reference numeral 20 denotes a liquid nitrogen introducing pipe, which is adapted to spray nitrogen on a part of the air circulation path of the refrigerator 1.

The same mold making and casting were carried out using such a disappearing model without extraction, but a product without any problems could be obtained.

COMPARATIVE EXAMPLE 5.5 A casting sand 3 prepared by adding 4% by weight of water to 100 parts by weight of silica sand and kneading was used as a wooden mold having a casting frame 10 and a suction hole 6 as shown in FIG. The model 7 and the fan 14 set so as to be sucked are put into a portion surrounded by the surface plate 4 and tamped. Next, the cooling medium 38 (liquid nitrogen, dry ice, etc.) was sprayed on the upper part of the mold, and at the same time, suction was performed by the fan 14. At this time, a phenomenon was observed in which the air 33 at room temperature was sucked into the mold. When the suction pressure of the fan 14 is too high, the movement of water occurs and the ice layer 39 is formed. If the suction pressure of the fan 14 is too low, suction is not sufficient due to the resistance of the molding sand 3, and freeze strength cannot be obtained. The suction pressure at which the movement of water occurs is related to the grain size composition of the foundry sand 31, and cannot be generally determined.

When the energy efficiency of the refrigerant 38 is calculated, the air 33 at room temperature is sucked, and most of the energy is consumed to cool the air 33. Therefore, the cooled air is discharged. Therefore, the energy efficiency is only 3-5%.

Next, the surface plate 4 and the model 7 were tried to be removed, but when liquid nitrogen was used as the refrigerant, the surface plate 4 was cooled so that even thick gloves could not be touched, and in a dangerous state. there were. On the other hand, the foundry sand 3 was not cooled as much as the platen 4 etc. because the sand itself is a heat insulating material. Model 7
At the same time as removing the frost on the surface of the molding sand 3,
I could not remove it after that. Vinyl seal
I tried to cover the shape side of the molding sand 3 with
This work was not possible due to the instant frosting. Somehow, a mold was formed and pouring was performed, but defects such as blowback during pouring, pinholes, and rough skin occurred on the product.

FIG. 5 shows the difference in cooling rate depending on the cooling method.

FIG. 5 is a cooling curve showing a portion where air is aerated by the differential pressure according to the first embodiment.
4 is a cooling curve when the heat pipe 40 shown in FIG. 4 is attached, and is a cooling curve obtained by cooling only by heat transfer because it is difficult to ventilate the mold in the freezing system of FIG. At first glance, it can be seen that the aeration cooling by the differential pressure is the fastest, but there is a considerable effect even when the heat pipe 40 is used, and especially in the initial stage of 0 ° C to -10 ° C which is considered to be important in terms of the strength of the mold. You can see that it is effective when frozen. Further, when the heat pipe 40 is used, the cooling efficiency is further improved by directly cooling with the coolant such as burying the fin 41 of the heat pipe 40 in the coolant as shown in FIG.

[0033]

EFFECTS OF THE INVENTION According to the method for producing a frozen mold of the present invention, it is possible to efficiently produce a frozen mold free from dangerous work such as frostbite. Further, one refrigerator can be used for many operations such as freezing work, frost prevention work, and mold storage, and casting defects can be eliminated. It is a freezing method that uses air, and because it reuses cooled air many times, it is a freezing mold manufacturing method that is also environmentally friendly.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing one embodiment of a freezing mold manufacturing method according to the present invention.

FIG. 2 is a cross-sectional view showing another embodiment of the freezing mold manufacturing method according to the present invention.

FIG. 3 is a cross-sectional view showing an embodiment of the frost prevention method according to the present invention.

FIG. 4 is a front view of a heat pipe used for cooling of the present invention.

FIG. 5 is a graph showing a difference in mold cooling rate.

FIG. 6 is a cross-sectional view showing an example of a conventional freezing mold manufacturing method.

[Explanation of symbols]

1 refrigerator 2, 5, 7 model 3 Foundry sand 4 surface plate 6 holes 8 ventilation section 10 flasks 12 wind guide 14 fans 16 Cooling unit 22 Lid 38 Refrigerant 39 Ice layer 40 heat pipe 41 fins

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-61-14045 (JP, A) JP-A-3-181766 (JP, A) JP-A-6-50643 (JP, A) JP-A-2- 82075 (JP, A) JP 56-154249 (JP, A) JP 60-15042 (JP, A) JP 57-28653 (JP, A) JP 57-149045 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) B22C 9/02 F25D 3 / 10,13 / 00

Claims (7)

(57) [Claims] 1. A freezing mold manufacturing method for manufacturing a mold by freezing water containing foundry sand, which comprises 1 to 12% by weight.
In a closed system that circulates low temperature air of -3 ° C or below , which is formed by sand containing foundry and cooled by a refrigerator
It was recovered after said low-temperature air is once circulated into a mold that is in place, and cooled through a heat exchanger of the refrigerator
The recovered low-temperature air is circulated again into said mold, so as to freeze the mold by cold air circulating in the closed system
A method for producing a frozen mold, comprising: Wherein said cold air, according to claim 1, the moisture contained in the said mold, characterized that you distribute the template in type in differential pressure state so as not to move in the said template Freezing mold manufacturing method. 3. The method for producing a frozen mold according to claim 1, wherein a heat pipe is inserted into the mold so as to promote freezing of the mold. 4. The manufacturing operations of the frozen template row in the refrigerator by 10 ° C. below the dew point in the dehumidified storage room
4. The method according to claim 1, wherein
The method for producing a frozen mold according to the item. 5. A nitrogen, carbon dioxide, one of the liquefied gas Heryuumu or claim 2 refrigerant used in combination thereof, characterized in Rukoto are mixed circulation path of the cold air, The frozen mold manufacturing method according to any one of 3 above. Wherein said refrigerant is, according to any one of claims 1, 2, 3 to the sand surface or wherein Rukoto directly or indirectly sprayed to the fin portion of the punching plate Freezing mold manufacturing method. 7. A freezing mold manufacturing method according to any one of claims 1-5, characterized in that it comprises containing the molding sand is additive.