JPS58145329A - Molding method of casting mold - Google Patents

Abstract

PURPOSE:To dry and harden a casting mold quickly and firmly by permeating gaseous CO2 and high temp. air through the casting mold which is molded of molding sand with calcium hydroxide and an org. resin as binders. CONSTITUTION:An aq. soln. of 2wt% calcium hydroxide and 50wt% water soluble phenolic resin is added as a binder to molding sand at 4wt% thereof, and after the mixture is mulled, the mixture is pressurized and molded, thereby molding a green casting mold 16. The mold 16 which is held placed on a bottom mold is put into a cover member 17, and gaseous CO2 of 1.0kg/cm<2> pressure is supplied for 10sec at 20l/min rate through a supply pipe 20 for gaseous CO2 to harden the mold to about 7kg/cm<2> compressive strength. In succession, the compressed air heated to 120 deg.C is supplied for 30sec at 350l/min rate through a supply pipe 19 to permeate the air through the mold, whereby the firm casting mold having 35kg/cm<2> compressive strength is molded in a short time.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a mold making method, and more specifically, a method for rapidly and firmly molding a mold using foundry sand containing mainly calcium hydroxide and an organic resin as a binder. The present invention relates to a method for making a mold by drying and hardening.

Conventionally, carbon dioxide gas is blown into a mold made by mixing silica sand with calcium hydroxide, an organic resin, and water as necessary, and after the mold is hardened and removed, the mold is molded for one day. The method of increasing the strength of the mold by leaving it for a while is known as lime molding. Generally, as this organic resin, water-soluble cellulose derivatives such as methyl cellulose and carboxymethyl cellulose, copolymers of acrylic ester and ammonium acrylate, and resol type water-soluble phenol resins are used. Recently, polyvinyl alcohols having different degrees of polymerization, α-olefin maleic anhydride polymers, alkaline aqueous solutions of hydrophobic phenolic resins, and the like have been used.

This type of lime mold is produced using a CO2 process (a mold made using molding sand mixed with sodium silicate).
The mold disintegrates better after pouring compared to a mold made by a method of hardening and molding the mold by blowing in O2 gas (also, compared to the shell molding method or cold box method, there are no harmful gases or It has the advantage of not emitting foul-smelling gas, but in order to increase the strength of the mold to a predetermined hardness, as mentioned above, the mold must be left for about a day after being demolded, or it is necessary to use a technique that has recently been published. As shown, 1
Either the product must be placed in an oven-type drying oven for about 2 hours, and in either case, the productivity was poor (it was not practical).

The present invention has been made in view of these problems, and is made by blowing carbon dioxide gas and hot air into a mold made of foundry sand containing calcium hydroxide and an organic resin as binders. The object of the present invention is to provide a mold making method that rapidly and firmly dries and hardens a mold.

The configuration of the present invention will be explained below based on examples. (1
) are placed on the top surface of the bed (2) with columns (3) at predetermined intervals.
) is erected, and the upper end of the column (3) is connected to the upper frame (
The bed (
2) A clamp cylinder (5) is mounted upward in the center of the upper surface, and an elevating table (6) is fixedly connected to the tip of the piston rod (5a). The exhaust stand (1) has a hollow part (7) inside, has a through hole (8) in the upper surface communicating with the hollow part (7), and has an exhaust hole (9) in one end side.
0) is installed.

The upper surface of the exhaust stand (10) has a through hole (11) in the center.
A gasket (12) with a hole is placed so that the through hole (11) substantially coincides with the through hole (8) of the exhaust stand (10),
Further, the upper surface has a recess (13) on the lower surface, and a large number of ventilation holes (14) on the upper surface communicating with the recess (13).
The lower die (15) with which the recess (13) is drilled connects the through hole (8) to the recess (13).
(11), and an uncured mold (16) is supported and placed on the upper surface of the model. The uncured mold (1
6) is made of foundry sand that is a mixture of silica sand, mainly calcium hydroxide, an organic resin, and water as necessary. (17) is fixed to the F side of the upper frame (4) of the frame (1) via a support member (18), and has an open bottom surface.
1, the hollow cover member (17)
A heated compressed air supply pipe (19) and a carbon dioxide gas supply pipe (20) are connected to the internal hollow part on the side tilted wall surface, and the supply pipe (19) is connected to an on-off valve ( 21) to a heated compressed air storage tank (not shown), and the other supply pipe (20) is connected to a carbon dioxide gas storage tank (not shown) via an on-off valve (22). has been done. In addition, (23) is a guide rod whose tip is fixedly connected to the lifting table (6), and is slidably inserted into the guide tube (24) attached to the bed (2), and is connected to the lifting table (6).
This is to prevent rotation in the horizontal plane.

In this structure, a mold box consisting of a lower mold (15) and an upper mold (not shown) contains a mixture of silica sand, mainly calcium hydroxide, an organic resin, and water as necessary. After filling molding sand with conventional means such as blowing or hand filling, the upper mold (not shown) is removed and the unhardened mold (16) remaining in the lower mold (15) is filled with molding sand. ) on top of the exhaust stand (10).
12) through the recess (13) through the through hole (8) (11)
At the same time, place the clamp cylinder (5
), the lifting table (6) is raised and the upper surface of the exhaust platform (10) is brought into contact with the lower end surface of the cover member (17) via the packing (12) to support the uncured mold (16). After covering the lower mold (15) airtightly with the cover member (17), the on-off valve (22) for carbon dioxide gas is opened to release carbon dioxide gas into the airtightly closed cover member (17). When this carbon dioxide gas is supplied, the uncured mold (16)
vents (14), recesses (13) and through holes (11) (8) through the exposed surface of the mold (16).
It is discharged through the exhaust hole (9).

At this time, the carbon dioxide gas reacts with calcium hydroxide in the mold (16) to harden the mold (16). Next, after closing the on-off valve (22) for carbon dioxide gas, the on-off valve (21) for heated compressed air is opened to supply heated compressed air into the cover member (17). Similarly, it passes through the mold (16) and is discharged from the exhaust hole (9). Here, the uncured mold (16) is rapidly heated and the water in the mold (16) is rapidly evaporated, resulting in polymerization or condensation of the organic resin as a binder and The dehydration of the mold (16) proceeds almost simultaneously, and the unhardened mold (16) on the upper surface of the lower mold (15), combined with the reaction between the calcium hydroxide and carbon dioxide gas, becomes solidly hardened in an extremely short period of time. It is something that will be done.

In the above embodiment, heated compressed air was vented after carbon dioxide gas was vented into the uncured mold (16), but carbon dioxide gas and heated compressed air were mixed and vented at the same time. Next, examples performed using the above method are shown below.

(Example 1) Foundry sand prepared by adding and mixing silica sand, 2% by weight of calcium hydroxide, and 4% by weight of a 50% by weight aqueous solution of water-soluble phenolic resin was placed in an upper mold and a plurality of ventilation holes. (14)
After filling the cavity of a cylindrical composite model consisting of a lower mold (15) with
5) Apply a pressure of 1.0'j to the surface of the unhardened mold left on the top surface.
When carbon dioxide gas was applied at a rate of 20% for 10 seconds, the resistive pressure of the mold became 7. Next, heated compressed air heated to 120 DEG C. and a pressure of 1.degree. OK was applied to this mold at a rate of 350 DEG C. for 30 seconds, and the mold's resistive pressure became 35.

(Example 2) After filling the cavity of the model with molding sand having the same composition as in Example 1, the upper mold was removed and a plurality of ventilation holes (14
) left on the upper surface of the lower mold (15) with the uncured mold (1
6) Carbon dioxide gas at a pressure of 1.0 vA was applied to the surface at a rate of 10 μm, and the pressure was heated to 120°C.

Next, if the shape of the model is complex and there is a risk of breaking the unhardened mold when removing the upper mold, it is recommended to pre-cure the mold by aerating carbon dioxide gas before removing the upper mold. convenient.

That is, as in the above embodiment, the cavity of the mold box consisting of the upper mold and the lower mold (15) was filled with molding sand having the same composition as in the above embodiment, and carbon dioxide gas was blown into the cavity. After pre-hardening the foundry sand so that it can be removed from molds with complex shapes, the upper mold (not shown) is removed and the pre-hardened mold (16) remaining in the lower mold (15) is
By the operation of the clamp cylinder (5), the lifting table (
6) and lift the cover part (15) together with the F type (15).
After covering the cover member (17) in an airtight manner, open the on-off valve (21) for the heated compressed air and cover the heated compressed air with the cover member (17).
When supplied into the mold, heated compressed air enters through the exposed surface of the open pre-cured mold (16) and passes through the mold (16) through the vents (14), recesses (13) and through holes (11).
) (8) and is discharged from the exhaust hole (9).

Here, the pre-cured mold (16) is rapidly heated and the water in the mold (16) is rapidly evaporated, resulting in polymerization or condensation of the organic resin as a binder. Dehydration of the mold (16) proceeds almost simultaneously, and the pre-hardened mold (16) on the upper surface of the lower mold (15) is strongly hardened in an extremely short time due to the reaction between calcium hydroxide and carbon dioxide gas. It is something. In addition, at this time,
When carbon dioxide gas is supplied into the cover member (17) together with heated compressed air, the reaction with calcium hydroxide becomes more reliable.

Next, an example will be shown below in which the method of curing the pre-cured mold by passing heated compressed air after pre-curing as described above is used.

(Example 3) Foundry sand prepared by adding and mixing 2% by weight of calcium hydroxide and 4% by weight of a 50% by weight aqueous solution of water-soluble phenolic resin to silica sand was mixed with an upper mold and a plurality of ventilation holes ( 14)
After filling the cavity of a relatively complicated composite model consisting of a lower mold (15) with a lower mold (15), a pressure of 1.0
``When Q4 carbon dioxide gas was applied at a rate of 20% for 10 seconds, the molding sand in the chamber became a pre-hardened mold with a resistance pressure of 5.

Next, the upper mold was removed, and the surface of the pre-cured mold remaining on the upper surface of the lower mold (15) was heated to 120°C under pressure 1.
．． When heated compressed air of 0 to 350 was applied for 30 seconds, the mold had a resistive pressure of 35.

(Example 4) After filling the cavity of the composite model with molding sand having the same composition as in Example 3, a pressure of 1.0'q,
After pre-hardening the molding sand in the cavity to a resistance pressure of 5 to 1 by applying carbon dioxide gas of 4 at a rate of 2024 □ for 10 seconds, the upper mold was removed and the upper surface of the lower mold (15) was pre-hardened. Pressure 1.0' on the surface of the pre-cured mold! l! p(
7) Carbonic power
'Q, t r: When heated compressed air heated to 120''C at a pressure of 1.0 and 7 was simultaneously applied at a ratio of 350- for 30 seconds, the resistive pressure of the mold became 39 k7.

A reference example in which heated compressed air is not applied to the mold as in the prior art is shown below.

(Reference Example 1) 'After filling the cavity of the composite model with molding sand having the same composition as in the above example, carbon dioxide gas at a pressure of 1.0 kV was applied to the cavity at a rate of 20-20 for 10 seconds. The molding sand in the cavity became the mold in a pre-hardened state to a counter pressure of 5.

After cutting out this pre-cured mold, it was left indoors at room temperature to naturally harden, and the resistance pressure after 24 hours was 22, and after 48 hours it was 34.

In the above embodiment, the lower mold (15) supporting the uncured or pre-cured mold (16) is placed on the lifting table (6).
) The lifting table (6) has an exhaust hole that communicates with the outside from the top surface, and uncured or pre-cured The F-type (15) supporting the mold (16) may be placed directly on the exhaust hole with the four parts (13) positioned therein. Further, in the above embodiment, the lower mold (15
) is provided with a ventilation hole (14), but it is also possible to provide a ventilation hole in the upper mold and, after filling with molding sand, turn the upper mold to the F direction and remove the overlying material.

Furthermore, in the above embodiment, the horizontally split model was blown and filled with molding sand, but the vertically split model was blown and filled with molding sand, and then the rigged model was turned over. You can also remove the upper model that is on top.

As is clear from the above description, the present invention applies carbonate to an uncured or pre-cured mold molded using foundry sand made by adding and mixing calcium hydroxide, an organic resin, and water as necessary to silica sand. Since heated compressed air is vented together with the gas, strong molds can be quickly obtained, which greatly contributes to improved productivity, which has excellent effects and is an effect that will contribute to this type of industry. is extremely significant.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway front view showing an embodiment of the present invention. (14): Ventilation hole (15): Lower mold (16)
: Unhardened or pre-hardened mold (17) : Cover part

Claims (1)

[Scope of Claims] 1. Silica sand, mainly calcium hydroxide, an organic resin, and water as needed, are placed in a combined model box with a small amount of ventilation holes (both sides of which are provided with ventilation holes that communicate the inner and outer surfaces of the box). a step of filling an uncured mold with foundry sand formed by adding and mixing;
removing the other model of the combined model box and placing and supporting the molded uncured mold on the inner surface of the one model; covering the uncured mold supported on the inner surface; a step of introducing carbon dioxide gas and heated compressed air into the cover member alternately or simultaneously; placing the carbon dioxide gas and/or heated compressed air on the inner surface of the supported base; A method for making a mold, comprising: penetrating the inside of the mold from an exposed surface of the hardened mold and discharging the cover member to the outside of the cover member through the holes and pores to harden the unhardened mold. 2. In a combined model box in which at least one of the models is equipped with a ventilation hole that communicates its inner and outer surfaces, molding sand made by mixing silica sand with mainly calcium hydroxide, an organic resin, and water as necessary is added. a step of filling the molding sand in the combined model box and pre-hardening the molding sand by passing carbon dioxide gas into the molding sand to form a pre-hardened mold; removing the other model in the combined model box and molding the molding sand; placing and supporting the pre-cured mold on the inner surface of the one model; placing a cover member over the pre-curing mold supported on the inner surface; Carbon dioxide gas and heated compressed air are introduced alternately or simultaneously into the mold, and the carbon dioxide gas and/or heated compressed air is passed through the mold from the exposed surface of the pre-cured mold supported on the inner surface of the mold. A mold making method comprising: discharging the cover member to the outside through a ventilation hole to firmly harden the pre-cured mold.