JPH10244345A - Molding sand and manufacture of mold using this - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain molding sand unnecessitating coating agent by crushing a shell and adding and mixing slaking lime to an aggregate obtd. by screening. SOLUTION: The shell (e) is heated at about 60 deg.C with a rotary kiln 1 and the organic material of an adductor muscle, etc., stuck to the shell (e) is burnt up and removed. The burning up treated shell (e) is pulverized with a crusher 2. The size of crushed grain diameter is adjusted so that the aggregate having the same grain diameter as the ordinary molding sand in the screening process can pick up much quantity. The crushed material (e') crushed with a crusher 2 and screened so as to become the grain size of the molding sand by using a screen 3. The aggregate (f) obtd. by screening is changed in a kneading vessel 4 together with the slaking lime (g) and stirred with a stirring machine 5 to obtain the molding sand (h). A method manufacturing a mold by using the obtd. molding sand, is executed by adding and kneading binder composed of water and methyl cellulose to the molding sand (h) to make the molding material, and filling up into a mold.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to molding sand and a method for producing a mold using the molding sand, and more particularly to a molding sand suitable for a core.

[0002]

2. Description of the Related Art Conventionally, river sand and mountain sand containing silicic acid (SiO2) as a main component have been used as this type of foundry sand. Among the foundry sands, those containing almost no viscosity, such as silica sand, river sand or beach sand, are used as synthetic sand artificially mixed with binders such as Kibushi clay and other substances. Mountain sand and the like that are contained to some extent are used as natural sand as they are.

[0003] Casting sand for cores (hereinafter referred to as "core sand") used for manufacturing cores can withstand the pressure of molten metal, and has poor shrinkability, fire resistance and air permeability. Because it is required to be superior, it has been examined more than casting sand for molds. A core is usually manufactured using the examined core sand by a shell mold method, a cold box method, or the like.

[0004] In recent years, there has been a problem that core sand has been difficult to remove from cast products due to thinning of cast products. For example, when the core is a shell core, the amount of heat received by the core during casting is small due to thinning of the casting,
There is a problem that the core contains a large proportion of the unburned synthetic resin in the binder, so that the core hardly collapses and the core sand is difficult to remove from the cast product.

[0005] In addition, shellfish are generated in large quantities as waste from fishery processing plants that use shellfish as a raw material. Some of these wastes are used as biological carriers for water treatment, but most of them are disposed of as landfills without being effectively used.

By the way, the main component of the shell is calcium carbonate (CaCO3), and it has been desired to develop a new application utilizing these properties.

Therefore, the applicant has previously filed Japanese Patent Application No. 8-35.
No. 0080, in order to provide a core that can be easily removed and to make effective use of the shell, a molding sand made by using an aggregate obtained by crushing and sieving the shell is proposed.

[0008] The foundry sand using the shell according to this proposal as an aggregate can be coated with a known binder to produce a mold (mother) or a core. In particular, a core having a predetermined strength or the like can be manufactured by a well-known shell mold method, cold box method, or the like.

In addition, since the casting sand according to this proposal is mainly composed of calcium carbonate, when the casting is immersed in an acid solution, the casting sand adhering to the casting is dissolved and removed from the casting. Even if it adheres to the inner space of a casting product like a core, there is a feature that it can be easily removed by an acid solution.

[0010]

However, even in the case of molding sand using shells as aggregates according to the above proposal, when core sand is used, expensive phenol resin or the like is used in the same manner as conventional molding sand. Requires a coating agent.

Accordingly, an object of the present invention is to provide a molding sand that does not require a conventional coating agent, and an object of the present invention is to provide a method of manufacturing a mold using the molding sand.

[0012]

The foundry sand according to the present invention comprises:
In order to achieve the above object, it is characterized in that it is obtained by adding slaked lime to an aggregate obtained by pulverizing and sieving a shell and mixing it.

In order to achieve the above object, the method for producing a mold according to the present invention is characterized in that water is added to the foundry sand according to claim 1 and then kneaded, and then the mixture is filled in a mold for molding. It is characterized in that a mold is manufactured by passing gas through. The mold is a core mold.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a process chart for manufacturing a molding sand according to one embodiment. Hereinafter, description will be made in the order of steps.

(A) Incineration process Shells A are shells such as oysters and scallops discharged as industrial waste from fishery processing plants, or pearl oysters discharged as industrial waste from a pearl manufacturing plant. Lee
It is mainly composed of CaCO3.

[0016] This shell A is 60 pieces in the rotary kiln 1.
Heated to about 0 ° C., the organic matter such as the scallop attached to the shell b is incinerated and removed. Although the incinerator in this incineration process is performed by the rotary kiln 1, other types of incinerators may be used.

(B) Pulverizing Step The incinerated shell A is pulverized by the crusher 2. The size of the particle size to be pulverized is adjusted so that a large amount of aggregate having a particle size of ordinary molding sand can be obtained in the sieving step described later.
That is, the powder is adjusted so that the degree of pulverization is not excessive and the amount of powder does not increase, and the degree of pulverization is too small and does not remain on the sieve.

Although the crusher 2 is of a mortar type, various types such as a ball mill type, a fret type or a crushing roll type can be adopted.

(C) Sieving process The crushed material A 'crushed by the crusher 2 is separated by using the sieve 3 so as to have a known particle size of foundry sand.

In FIG. 1, it is shown that one sieve 3 separates the aggregate B to be foundry sand, but in actuality, two types of sieves are used to separate the aggregate. First, it is passed through a sieve with a larger particle size distribution, which is acceptable as foundry sand,
The passed-through material is sieved with a sieve having an opening having the smaller particle size distribution, and the separated material remaining on the sieve is used as aggregate B.

(D) Mixing and Stirring Step As described above, the aggregate (b) obtained by sieving is put into the mixing tank 4 together with slaked lime, and the mixture is stirred by the stirrer 5 to obtain casting sand.

The mixing ratio of the aggregate B and the slaked lime is not particularly limited, but may be about 8: 2 to 6: 4 by weight. If the mixing ratio of the slaked lime is increased, the casting sand is used as a raw material. And the strength of the core and core can be increased.

Although not shown in the process diagram of FIG. 1, in order to manufacture a mold using the obtained casting sand, a binder made of water and methylcellulose is added to the casting sand, and the mixture is kneaded. This is done by filling a mold. The ratio of the water to be added is about 15% by weight based on the mixture of the aggregate B and the slaked lime. In other words, the water content is adjusted so that the raw sand mainly containing normal silica sand is wet.

The binder is not an essential additive, but when the binder is added by about 1% by weight to a mixture (molding material) of bone, slaked lime and water, the molding material becomes a mold. It has the feature that it is easy to form a mother die and a core when put in

As the binder, besides the above-mentioned methyl cellulose, those capable of imparting viscosity to substances such as polybeer alcohol can be used.

In order to produce a mold using the mold material obtained as described above, the equipment of the conventional carbon dioxide type method can be used as it is.

That is, in the conventional carbon dioxide gas type method, silica sand mixed with water glass is put into a mold, and then carbon dioxide gas is passed through the mold to cure the mold. The material can also be cured using carbon dioxide.

Therefore, the mold material such as a core can be manufactured by filling the mold material into a mold for manufacturing a core and then curing the mold by passing carbon dioxide gas through the mold.

In the mold thus produced, slaked lime (Ca (OH) ₂ ) mixed with the bone mineral B is also changed to calcium carbonate (CaCO 3) as shown in the following formula. Note that the generated water (H ₂ O) is removed by heating and drying.

Ca (OH) ₂ + CO ₂ = CaCO ₃ + H ₂ O

As described above, since the main component of the mold is made of calcium carbonate, the mold is dissolved when immersed in nitric acid (HNO3). Can be removed.

Further, the waste liquid nitrate (Ca (NO ₃ ) ₂ ) obtained when the template is dissolved can be effectively used as a valuable nitrogen fertilizer.

[0033]

The foundry sand according to the present invention crushes shells,
Since it is obtained by adding slaked lime to the aggregate obtained by sieving and mixing, a mold such as a core can be manufactured without requiring a conventional coating agent, and the main component is calcium. , It can be easily removed with a nitric acid solution.

In the method for producing a mold according to the present invention, water is added to the foundry sand, kneaded and then charged into a mold, and carbon dioxide gas is passed through the mold to produce a mold.
The equipment of the conventional carbon dioxide method can be used as it is.

When the mold is used for a core, the core sand can be easily removed from the casting.

[Brief description of the drawings]

FIG. 1 is a process chart when manufacturing foundry sand according to one embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Rotary kiln 2 Crusher 3 Sieve 4 Mixing tank 5 Stirrer A Shell I 'Crushed material B Aggregate C Slaked lime D Foundry sand

Claims (3)

[Claims] 1. A foundry sand obtained by adding slaked lime to an aggregate obtained by crushing and sieving shells and mixing them. 2. The mold according to claim 1, wherein water is added to the molding sand according to claim 1, and the mixture is kneaded and then filled into a mold, and carbon dioxide gas is passed through the mold to produce a mold. Production method. 3. The method for producing a mold according to claim 2, wherein the produced mold is for a core.