JP2003251436A - Method for manufacturing mold and mold composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a mold by which the manufacturing cost of the mold and the quality of a casting can be improved, and the use of artificial sand can remarkably be expanded, and to provide a method of reproducing sand. <P>SOLUTION: In the method of manufacturing the mold, as refractory materials, facing sand and backing sand having different fineness are used to compose the mold. In the method of reproducing sand, reproduced sand which is reproduced by the conventional method and in which facing sand and backing sand coexist is separated by a sieve, and are individually reutilized. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001] The present invention relates to the production of a mold for recovering and reusing used sand in organic and inorganic self-hardening methods and gas hardening methods. The present invention relates to a method for manufacturing a mold and a method for recovering and reusing foundry sand, which reduces the manufacturing cost of the mold and also improves the quality of the casting.

[Prior art]

In the conventional organic and inorganic self-hardening methods,
Most of the regulations for waste control adopt the recycling law to collect and reuse the used sand.

In the recycling method, kneaded sand obtained by blending a single kind of sand aggregate with a binder is used as a mold.
All the molds have been manufactured with the same kneading sand except for special sand (spot sand for seizure prevention).

[0004] In order to maintain the quality of the casting, it is necessary to have fine refractory, fine-grained and high-quality sand aggregate for skin sand that directly contacts the molten metal, but back sand is not so necessary. However, since there is only one kind of sand aggregate, it is unavoidable that the kneading sand using high quality sand aggregate is used as a whole.
Although it depends on the shape of the casting, the required weight of skin sand is generally about 30% of the total amount of sand used.

High-quality sand aggregate is naturally expensive and requires a large amount of binder to be added because it is fine granules, so the cost of the mold material is high.

In order to improve gas defects of casting defects,
Although it is necessary to reduce the amount of binder added, there is a limit to maintaining the strength of skin sand, and a gas needle is often inserted in the back sand to provide a gas vent hole to take countermeasures. Therefore, work cost is required.

In cast steel, the casting temperature is high and casting defects such as seizure are likely to occur. Therefore, zircon sand or chromite sand, which has high fire resistance, is often used together as a pocket sand. Since the specific gravity of the pocket sand is heavier than that of silica sand, the pocket sand may be accumulated in the reclaimed sand to complicate the reclaimed sand management and affect the casting quality.

On the other hand, recently, as a measure for waste regulation,
There is no choice but to raise the recovery rate of sand to 98% or more, and mullite artificial sand or refractory made by sintering alumina-based powder refractory is melted and crushed or slag is crushed. Artificial sand has been developed and its use is spreading.

In the production of this artificial sand, since it is produced by spraying or pulverizing a liquid one, it is impossible to obtain a uniform particle size. Only a small amount can be made, and most of them generate coarse particles, so there is a wasteful cost of re-melting unless it is used, and the price of artificial sand is also high. It is sold at about 5 times the price.

[Means for solving the problem]

The present problems have been described above. A high-quality refractory material is used as the skin sand, a general low-cost refractory material is used for the back sand, and after recovering and reusing together after use, both By separating the mold, the degree of freedom in selecting the back sand can be increased and the cost of the mold material can be reduced.

Therefore, even if a high-grade refractory having a required fine grain size is applied to the skin sand and a refractory substance having a grain size coarser than that of the skin sand is used for the back sand, even if it is collectively cast and recovered after collecting, By separating with a vibrating screener that passes only the skin sand after regeneration, it becomes possible to use the skin sand and the back sand independently and repeatedly.

In order to separate the reclaimed sand, it is not necessary to significantly modify the existing equipment, and a predetermined vibrating sieve is provided before the inlet of the conventional sand cooler or before the inlet of the storage tank to separate and store them individually. If the storage tank on the mixer is modified and divided so that the separated skin sand and back sand can be stored separately, kneading the skin sand and back sand with the same mixer by using a slide gate, etc. You can easily get sand.

Skin sand is easily regenerated because its binder is well decomposed by the heat of casting, the properties of recovered skin sand are further improved as compared with the conventional method, and the air permeability is increased by further coarsening the grain size of the back sand. Gas needle work can be omitted because removal is easy.

【Example】

150 kg of commercially available artificial sand with a fine forsterite particle size of 0.11 to 0.45 mm is used as skin sand.
For the back sand, 350 kg of coarse artificial sand having a particle size of 0.85 to 2.10 mm was used to produce an alkali phenol mold, and 160 kg of cast iron was cast.

As skin sand, 1.50 parts by weight of an alkali phenol resin and 0.25 parts by weight of an ester curing agent were added to 100 parts by weight of fine sand and kneaded. As the back sand, 100 parts by weight of coarse sand was mixed with alkali phenol resin 0.1.
8 parts by weight 0.15 parts by weight of an ester curing agent were added and kneaded.

A rectangular model was set on a surface plate, the model surface was covered with kneaded fine-grained sand, and the back was filled with kneaded coarse-grained sand and allowed to cure.

After the mold was cured, the model was released, alcohol coated and dried, and then cast iron at 1420 ° C. was cast.

The cooled sandy sand was regenerated using a 1 t / H tester and passed through a 28-mesh screen to separate skin sand and back sand for examination. The results are shown in Table 1.

As a comparative example, a mold was produced using only the fine-grained sand of the example, and cast iron was cast at 1420 ° C. in the same manner, followed by the same regeneration. The results are shown in Table 1.

[0020]

[Table 1]

[0021]

As described above, the following effects can be obtained by using the mold manufacturing method and the used sand reclamation method of the present invention. (1) Because skin sand and back sand can be used separately,
As a result of using a small amount of expensive and high-quality skin sand and covering the rest with inexpensive and even lower-strength back sand, the cost of the mold material can be significantly reduced. (2) By being able to use skin sand and back sand separately,
As for sand selection, inexpensive sand can be freely selected according to the purpose. (3) By being able to use skin sand and back sand separately,
The properties of the reclaimed skin sand are improved as compared with the conventional method, and the cost and casting quality can be further improved. (4) With the sand reclaiming method according to the present invention, skin sand and back sand can be easily separated and collected for use by slightly changing the conventional equipment. (5) According to the present invention, it is possible to apply to the mold, artificial sand having a coarse grain size, which cannot be used conventionally.

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Claims (7)

[Claims] 1. In a recycling method in which the sand used as a mold is collected, reclaimed, and reused repeatedly, fine sand that passes through a sieve with a mesh finer than 20 mesh (850 μm) is used as surface sand (casting sand). Used as sand that contacts the surface,
A method of manufacturing a mold in which coarse sand that does not pass through the same mesh screen is used as back sand (sand that backs up behind the skin sand). 2. An aggregate of forsterite obtained by melting and refining mullite-type spherical artificial sand, olivine or serpentine obtained by melting and refining alumina refractory as aggregate. The method for producing a mold according to claim 1, wherein the spherical artificial sand of No. 1 and the forsterite type spherical artificial sand obtained by crushing a slag generated during nickel smelting are used. 3. The mold manufacturing method according to claim 1, wherein as the aggregate, spherical artificial sand of mullite type or forsterite type obtained by granulating and sintering powdery refractory is used. 4. The mold manufacturing method according to claim 1, wherein silica sand, zircon sand, chromite sand, and olivine sand obtained by processing a naturally occurring refractory material is used as the aggregate. 5. An acid-curing furan resin, an acid-curing phenol resin, a water-soluble alkali phenol resin, a phenol urethane resin or water glass is used as a binder.
The method for producing a mold described in. 6. A template composition obtained by the method according to any one of claims 1 to 5. 7. A method for recovering and reusing foundry sand having a device and a function capable of sieving fine sand and coarse back sand from reclaimed sand and storing them in individual tanks, and kneading the respective sands individually. Method and foundry sand recovery and regeneration equipment.