JPS62259637A - Molding method for casting mold - Google Patents

Abstract

PURPOSE:To reduce the cost of a mold and also to simplify the adjustment of slurry by using the slurry composed of a binder containing no water in a coating at the first and second times and using the slurry composing of the binder containing much quantity of water at least one time after the third time at the time of molding for a shell mold. CONSTITUTION:As the slurry used to the coating at the initial stage, the slurry, which is conventionally used to the urea-series dissipating model and consists of the binder containing no water and a little of gas, is used just as it is. As the slurry, used after that and composing of the binder containing much quantity of water, the slurry, which is used to the coating on the nonaqueous dissipating model, such as wax, etc., is used just as it is, and especially the slurry, composing of the binder containing the water base silica sol having 20-50 wt.% SiO2 and 5-50 mmu grain size is used. Further, zircon, fused alumina, etc., is used as the powder added it, and fused silica, mullite, high alumina sand, etc., is used as the stucco material.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a mold making method, and more particularly to a shell mold making method using a water-soluble disappearing model.

(Prior Art) In recent years, the ceramic shell molding method has been increasingly adopted as a method for making shell molds. The reasons for this are: 1. Slurry can be saved, 2. Large-sized castings can be made, and 2. Heat dissipation after casting is uniform and rapid (this makes the material of the product homogeneous).

Ceramic 7 Elmold method is well known.

The vanishing model is dipped into the slurry, pulled out, sprinkled with stucco and left to dry. The so-called three-step FJR process of coating, sanding, and drying is repeated several times to form a ceramic shell layer with the required thickness, and then the internal disappearing model is exposed to heat or other means. for example.

``Foundry Handbook'' edited by Memoto Foundry Association, revised 3rd edition (Showa 5 & 1α)
30. Maru! It is described on page 1520.

There are wax-based, naphthalene-based, plastic-based, and urea-based materials as materials for the disappearing model, but urea-based materials are especially water-soluble and have high strength and dimensional stability. , and because it is inexpensive, it has been used more and more recently.

(Problems to be Solved by the Invention) However, when using a water-soluble material such as a urea-based material for the vanishing model, there are the following problems.

That is, when coating with a slurry, if a slurry made of a binder containing a large amount of water is used, there is a problem that the vanishing model suffers from bath loss and a satisfactory mold skin cannot be obtained. Therefore, in the past, all shell layers were formed using a binder in the slurry that contained no or very little water, or only the first layer contained no or very little water. A method has been used in which a binder containing no water is used, and a binder containing a little water (for example, an ethyl silicate hydrolyzate) is used in the second and subsequent layers. However, these binders are expensive, and because they are subject to hydrolysis due to moisture in the air, they harden quickly, resulting in a problem of shortening the life of the slurry (the period during which it remains in the slurry state).

The present invention has been made to solve the above problems, and its purpose is to provide an inexpensive shell mold that does not roughen the mold surface even when using a disappearing model made of a water-soluble material such as urea. It is an object of the present invention to provide a molding method, and for that purpose, to provide a method that can use a slurry made of a binder that is inexpensive and has a long life.

(Another Means to Solve the Problems) The mold making method according to the present invention which aims to achieve the above-mentioned object is to In the first two coatings, a slurry consisting of a binder containing no or very little water is used, and at least once in the fifth and subsequent coatings, a slurry consisting of a binder containing a large amount of water is used. It is characterized by doing.

The present invention involves repeatedly coating a disappearing model made of a water-soluble material (in this case, a slurry consisting of a binder that contains almost no water is used for the initial coating, and a slurry consisting of a binder that contains almost no water is used for the initial coating, and It has been discovered that the above object can be achieved by using a slurry made of a binder containing a large amount of preferable.

As the slurry used for the initial coating, a slurry consisting of a binder containing no or very little water, which has been conventionally used for one urea-based vanishing model, can be used as is.

Further, as the slurry consisting of a binder containing a large amount of water that is used thereafter, the slurry that has been used for coating a water-insoluble vanishing model such as wax can be used as it is, but it can be used as is. A slurry containing an aqueous silica sol as a binder is preferable, and its Sin! It is preferable that the particle size is 5 to 50 mμ.

In order to make a suitable slurry, regardless of the type of binder, commonly used powders such as zircon, fused silica, and fused alumina can be used as they are.7 Also, as stucco materials, fused silica and mullite can be used. , high alumina sand, etc. can be used.

(Function) The configuration described above provides the following effects.

That is, the initial multiple coatings with a slurry of binder containing no or very little water form a waterproof coating on the surface of the vanishing model. The coating prevents a subsequently coated slurry containing a large amount of water from penetrating the water-soluble disappearing model and dissolving the model.

(Example) An example of the present invention will be listed below and will be specifically explained.
The present invention is not limited thereby.

1 and 2 are a plan view and a front view, respectively, of the vanishing model used in this embodiment f. The model 5 was made by injection molding using a urea-based material, and in Figure 1, 1 is a sprue part, and 2&'i runner part.

3 is a seed part, and 4 is a product part.

In addition, the following two types of binders were used to adjust the slurry.

Binder A: 8i0, 201 violet ethyl silicate hydrolyzed H, (contains very little water) Binder B: 8i0, 30% by weight colloidal silica (
(contains a large amount of water).

First, the above-mentioned vanishing model was coated by immersing it in a slurry obtained by mixing 1,000 parts by weight of binder A with 5,000 parts by weight of Zircon flour #350, and after sanding with Zircon sand $80+, it was dried.
A layer was formed. Furthermore, a second coating was applied by immersing it in a slurry obtained by mixing 4,800 parts by weight of zircon flour #200 with 000 parts by weight of binder Al.
Next is high alumina sand α3~α7f! aR′fJ:
Sanding and drying (this formed a second layer. After that, in the same manner as slurry, 4 parts of zircon flour #200 was added to 81,000 parts by weight of binder.
800 parts by weight of the mixture was also used as Meta 1 material)・
5th to 6th using earlumina sand α3 to α7ffll
The layers were stacked one after the other. Finally, the model was melted and removed by heating, and the urea-based material was further heated to completely disappear, and the shell layer was fired to form a shell mold.

As a comparative example, a shell mold was molded in the same manner as in the example except that the binder At-binder B for forming the second layer of the example was changed.

The appearance and mold skin of 20 molds molded in each of the above Examples and Comparative Examples were investigated.

As a result, the mold according to the example had an appearance of 1. In contrast, in the case of the comparative example, the mold skin was rough because the vanishing model gave out the bath, and moreover, the urea compound in the vanishing model that was bathed followed the mold and went outside. Due to the precipitation, feather-like crystals were generated. The mold strength was very low and it was so brittle that it would collapse even if it was touched by hand.

(Effects of the Invention) The mold making method of the present invention provides the following effects.

First, binders containing a large amount of water, which could not be used because the water-soluble disappearing model is exposed to water, can now be used, expanding the range of binder materials that can be selected. Therefore, it is possible to use an inexpensive and long-life binder such as colloidal silica, which makes it possible to reduce costs and reduce the effort required to prepare the slurry.

In addition, it is possible to use a binder with high bonding strength (e.g. colloidal silica) while preventing erosion of the water-soluble disappearing model, which causes deterioration of the mold surface and mold strength.
This allows the strength of the mold to be increased, making it possible to make the mold thinner and lighter.

That is, according to the method of the present invention, a high quality shell mold can be manufactured in a very convenient manner.

[Brief explanation of drawings]

1 and 2 are a plan view and a front view, respectively, of a vanishing model used in an embodiment of the method of the present invention. In the figure. 1... Sprue part 2... Runway part 5... Weir 5 4... Product part 5... Disappearance model

Claims (10)

[Claims] (1) When molding a mold using the ceramic shell mold method using a disappearing model made of water-soluble material, the first two
For the first coating, use a slurry made of a binder containing no or very little water, and for the third and subsequent coatings, use a slurry made of a binder containing a large amount of water at least once. Characteristic mold making method. (2) The method according to claim 1, wherein the third and subsequent coatings are all performed using a slurry made of a binder containing a large amount of water. (3) The method according to claim 1, wherein the binder containing a large amount of water is an aqueous silica sol. (4) SiO_2 content of aqueous silica sol is 20-50
4. A method according to claim 3, characterized in that the amount is % by weight. (5) The particle size of SiO_2 in the aqueous silica sol is 5 to 50 m
The method according to claim 3, characterized in that μ. (6) The aqueous silica sol is SiO_ with a particle size of 5 to 50 mμ.
3. The method according to claim 3, wherein the method contains 20 to 50% by weight of 2. (7) The method according to claim 2, wherein the binder containing a large amount of water is an aqueous silica sol. (8) SiO_2 content of aqueous silica sol is 20-50
8. A method according to claim 7, characterized in that it is % by weight. (9) The particle size of SiO_2 in the aqueous silica sol is 5 to 50 m.
The method according to claim 7, characterized in that μ. (10) Aqueous silica sol has a particle size of 5 to 50 mμ SiO_
8. The method according to claim 7, which contains 20 to 50% by weight of 2.