JPH01262040A - Method and mold material for precision casting - Google Patents

Abstract

PURPOSE:To precisely cast a casting having good surface finishing for short time by pouring molten metal into a mold obtd. by cut-machining a material composed of base material of MgO and auxiliary materials of glass fiber, etc. CONSTITUTION:The mold material containing MgO as the base material and dispersing the auxiliary material containing fibrous material of the glass fiber, etc., at about 50-70:50-30 weight ratio to the base material is obtd. The MgO uses one having 45-60% porous ratio. Further, besides the fibrous material, bentonite and gypsum powders in the above auxiliary material can be mixed at about 30:40:30 ratio. The above mold material is machined into the desired shape by cutting, etc., to form the mold. The molten metal is poured into this mold to cast the casting. Then, after forming thermal-sprayed layer for low m.p. metal of Al, etc., on the machined surface of the mold, the molten metal having the same or the similar property as the above thermal-sprayed metal, is cast and the casting integrating the thermal-sprayed metal on the surface thereof can be obtd. By this method, by using the mold having good balance to machinability, shrinkage and gas permeability, the casting having good sur face finishing is precisely cast by cooling for short time.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a precision casting method and a mold material for precision casting, and more particularly, to an aluminum alloy used in the production of plastic molded products such as styrene. The present invention relates to precision casting methods and mold materials for precision casting for manufacturing molds made of aluminum alloys and zinc alloys.

[Conventional technology]

Although various methods have been proposed for casting molds of aluminum alloys, zinc alloys, etc., the ceramic mold method is often adopted today. However, this method has the problem that it requires a lot of labor and time because it requires intermediate steps such as a plaster model manufacturing process and a transfer mold manufacturing process. When such a mold is provided, there are problems such as it is difficult to pour the molten metal into the mold and it is necessary to process the casting such as the mold.

Therefore, in order to solve the above-mentioned problems, the following new precision casting methods have been proposed in recent years. In other words, ``a precision casting method (unexamined patent application) in which a mold material based on calcium silicate is processed by cutting or other means to form a mold, molten metal is poured into the mold, and a casting such as a mold is cast. (Refer to Publication No. 62-45447)" and "A mold material obtained by using gypsum as a base material and kneading and dispersing inorganic fibers in the base material is processed by cutting or other means to form a mold. A precision casting method (see Japanese Patent Application Laid-Open No. 45447/1983) has been proposed in which a molten metal is poured into a mold and a casting such as a mold is cast.

This precision casting method has the advantage that the manufacturing process can be shortened.

[Problem that the invention seeks to solve]

However, in the case of the precision casting method described above, the present inventor has various methods.
After conducting tests and prototyping, we found that the workability was sufficient, but the following problems were found. That is, (1) In the case of a structure using calcium silicate as a base material, if a certain degree of air permeability is imparted, the heat retention property will be too good, and the solidification time of the molten metal will become long.

■ If the base material is gypsum and inorganic fibers are dispersed therein, the air permeability (gas permeability) is not good, so there is a problem with the surface finish of the casting obtained by casting.

As mentioned above, it can be pointed out that in the case of the conventional precision casting method, there are drawbacks to the mold material itself. In other words, as previously proposed by the present inventor, the mold material must solidify the powder to satisfy the three elements of gas permeability, shrinkage and disintegration properties, and workability. This is thought to be due to the fact that mold materials produced by conventional casting methods do not satisfy these requirements.

The present invention has been devised to address the above-mentioned problems, and its purpose is to provide a precision casting method and a precision casting method that can shorten the manufacturing time of castings and provide a good surface finish for the castings. The purpose of the present invention is to provide mold materials for casting.

[Means for solving problems]

The precision casting method of the present invention as a means for achieving the above object involves processing a mold material, which uses magnesium oxide as a base material and contains fibrous materials such as glass fibers as an auxiliary material, into a desired shape by cutting or the like. A casting mold is formed, and a molten metal is poured into the mold to cast a casting.

Here, as an auxiliary material, in addition to fibrous materials such as glass fiber, it is configured to contain hendonite and gypsum powder, and if necessary, a low melting point metal such as aluminum or aluminum alloy is used on the processing surface such as cutting of the mold. A structure in which a metal sprayed layer is formed by thermal spraying, and then a molten metal having the same or similar properties as the sprayed metal is poured into the mold to produce a casting in which the metal sprayed layer is integrated on the surface. Good too.

Further, the precision casting mold material of the present invention as a means for achieving the above object uses magnesium oxide as a base material,
It consists of a structure in which an auxiliary material containing fibrous material such as glass fiber is dispersed in the base material. Here, as magnesium oxide,
Magnesium oxide with a porosity of 45-60% is used.

[Effect]

The precision casting method of the present invention based on the above structure solves the problem of conventional mold materials by solidifying the powder and granular material to improve gas permeability.
In other words, the emphasis is placed on processability and shrinkage disintegration property, and the weight of gas permeability 1 is low, and this balance is disrupted. By using magnesium oxide with a porosity of preferably 45 to 60% as the base material, dispersing fibers as an auxiliary material, and linking the magnesium oxide, the above balance can be imparted. This reduces the manufacturing time of castings and provides a good surface finish for the castings.

In addition, since metal spraying can be performed on the processed surface of the mold and the sprayed metal can be integrally formed on the surface during casting molding,
Its surface is made smooth through a series of processes.

〔Example〕

Hereinafter, embodiments embodying the present invention will be described with reference to the drawings.

Here, FIG. 1 is a process diagram for explaining the manufacturing process of an embodiment of the present invention, and FIG. 2 is a manufacturing process diagram of another embodiment of the invention.

The precision casting method of this example is a method for manufacturing a casting mold manufactured by the steps shown in FIGS. 1 and 2, and briefly,
It consists of four steps: ■Block body forming process, ■Block body cutting process, ■Casting process of molten metal for casting, and ■Casting separation process. Next, each process will be explained.

- Block body forming process - This process involves forming a casting block body used to obtain a mold,
In other words, it is a process of forming mold material. In other words, the casting block body is a block body having a structure capable of retaining the molten metal and producing a casting when molten metal for casting is poured into it, and in the process of manufacturing the block body. A block body (mold material) is usually made of magnesium oxide as a base material, and after dispersing and kneading auxiliary materials such as glass fiber, gypsum powder, and hendonite into the base material, the block is formed into a block shape. It is formed by firing at a temperature of about ℃ to dissipate the moisture inside.

Here, the weight ratio of the base material and the auxiliary material constituting the block body is 50-70:50-30. Further, the ratio of glass fiber, gypsum powder, and hendite constituting the auxiliary material is about 30:40:30. Here, the ratio of magnesium oxide as a base material to the holding material is 50 to 70, which is 50% by weight.
In the following cases, the strength is not sufficient and there are problems in shrinkage and disintegration, and in the case of 70% by weight or more,
This is done in consideration of the fact that there may be difficulties in processability. Moreover, the reason why the proportion of the auxiliary material was set as mentioned above was based on the test results. However, some degree of curing is also observed with other formulations. In addition, the porosity of magnesium oxide is 45 to 60%.
It is said that This is because gas permeability is ensured thereby. However, other porosities may be used.

As the magnesium oxide, magnesium oxide manufactured by Ube Chemical Industries was used. In addition, specifically, ・Magnesium oxide (MgO) 94.0 to 96.0 ・Calcium oxide (Cab) 0.80 to 1.50 ・Silicic acid (
SiO□) 0.65~1.65・Diiron trioxide (FzO:+) 0.30~0.75・
Alumina (^IzOi) 0.30~0.75
・Boron oxide (B2O2) 0.55-1.2
0, the porosity of magnesium oxide is 55 to 60%, and the bulk density is 1.5 to 1.7
(g/cm3) is used. Further, if necessary, about 10 weight of calcium silicate may be kneaded. Furthermore, other materials may be added as auxiliary materials.

-Block body cutting process- This process is a process of processing (shaping) the block body obtained in the block body forming process by cutting or other means to form a casting member. The processing is performed using an NC machine tool.

In other words, when cutting the block body, first,
Similar to the conventional casting method using a sand mold, the design of a sheet molded product made of a foamed plastic molded product obtained from a casting mold is converted into computer data using a CAD and CAM system, and a block body is created using this data program. This is a process that involves cutting.

The cutting process of this block body is done using CAD, CAM.
using a system and an NC machine tool operated by the system (usually using a simultaneous 5-axis head two NC machine),
We use three-dimensional machining to shape the block body.

In addition, the block body is the mold to be obtained (casting mold member)
Considering the size, etc., multiple blocks are processed and then combined and connected. By cutting in this manner, casting mold members (male and female molds) corresponding to conventional sand molds and the like can be obtained.

- Molten metal casting (pouring) process - This process is
Engaging the male and female casting mold members obtained in the previous step,
Molten metal for casting is poured into the space, and mold (casting) is formed.
This is the process of obtaining That is, it is a step of pouring a molten metal for casting a mold, and a step of manufacturing a mold made of a casting having a predetermined shape, size, etc. by cooling the molten metal.

Here, as the molten metal, molten pig iron can be used as a casting material, but usually a low melting point metal such as aluminum or an aluminum alloy is used. this is,
Although it depends on the material of the block body mentioned above, it varies depending on the molten metal holding power of the block body.

Additionally, if necessary, a metal material such as aluminum or aluminum alloy may be sprayed onto at least one mold surface of the mold (male and female molds) obtained in the previous step to form a sprayed layer on the mold surface. . This is achieved by pouring molten metal for casting, and when the molten metal cools and solidifies, the sprayed layer is integrated onto the surface, creating a smooth surface and providing good thermal conductivity when molding plastics, etc. The purpose of this design is to allow the plastic molding material to be placed in a preferable manner inside the mold. Here, the thermal sprayed layer is integrated because the metal sprayed layer is fired and attached to the mold surface as fine metal particles, but at the same time as it attaches, it is exposed to air and becomes oxidized, microscopically. As the sprayed metal is oxidized, the molten metal poured onto the surface of the sprayed metal (here, the molten metal must be a metal with the same or similar properties as the sprayed metal) .

), the molten metal flows over the surface without involving the oxidized sprayed metal.

The molten metal solidifies by cooling, but when it solidifies, the molten metal contracts, the male mold (mold) collapses due to its shrinkage, and the gas generated from the molten metal is released to the outside. A mold is formed in the mold by evacuation.

Here, the one having the above-mentioned thermal sprayed layer has the advantage that its surface is formed more smoothly.

- Casting separation step - This step is a step in which the molten metal for casting poured into a mold made of a block body in the previous step is cooled and taken out as a casting from the block body.

That is, this is a step of collapsing the male mold and taking out the mold formed in the space between the male and female molds. Then, the removed mold (casting) can be used as a mold for manufacturing various molded products.

In order to confirm the effectiveness of the casting method consisting of the above-mentioned steps, we investigated the conventional casting method (conventional example) using "a mold material that uses calcium silicate as a profit-making material" and the "conventional method using gypsum as a base material". "Mold material obtained by kneading and dispersing inorganic fibers"
The casting method using (conventional example ■) and the same conditions (same shape,
Each mold was cast under the following conditions: As a result, as for Conventional Example (2), compared to the present example, extra time was required for cooling the molten metal, and irregularities were observed on the surface. In addition, regarding conventional example (2), pin poles and the like were observed on the surface of the casting. In contrast, no pinholes or the like were observed in the castings obtained in this example. This is thought to be due to the fact that a difference was observed due to the use of magnesium oxide as a base material and the use of a mold material obtained by dispersing and kneading fibrous material into an auxiliary material.

By the way, since the mold requires male and female molds, the respective molds are obtained through the same process. However, it is also possible to use one in which only one mold is obtained by the method according to this embodiment and the other mold is formed by droplet spraying. In addition, in the above-mentioned embodiment, the method of casting the mold was explained, but
It is clear that ordinary castings can also be made.

Note that the present invention is not limited to the embodiments described above, and includes modifications that can be made without changing the gist of the present invention.

〔Effect of the invention〕

As is clear from the above description, according to the method for casting molds, etc. of the present invention, magnesium oxide is used as the base material,
Using a mold material (block body) in which fibrous material is dispersed as an auxiliary material and the magnesium oxide is linked,
"Workability" r Shrinkage collapse property It has the effect of providing a good surface finish.

[Brief explanation of the drawing]

FIG. 1 is a process diagram for explaining the manufacturing process of an embodiment of the present invention, and FIG. 2 is a manufacturing process diagram of another embodiment of the invention. Patent Applicant Mars Manufacturing Co., Ltd. Representative Patent Attorney Hirofumi Yoshimura

Claims (5)

[Claims] (1) A mold material made of magnesium oxide as a base material and containing fibrous materials such as glass fiber as an auxiliary material is processed into a desired shape by cutting etc. to form a mold, molten metal is poured into the mold, and the casting is made. A precision casting method characterized by casting. (2) The precision casting method according to claim 1, which contains bendonite and gypsum powder in addition to fibers such as glass fibers as auxiliary materials. (3) After spraying a low melting point metal such as aluminum or aluminum alloy onto the machined surface of a mold to form a sprayed metal layer, a molten metal having the same or similar properties as the sprayed metal is poured into the mold. 2. The precision casting method according to claim 1, wherein the metal sprayed layer is integrally formed on the surface of the casting. (4) A mold material for precision casting, characterized in that the base material is magnesium oxide, and an auxiliary material containing fibers such as glass fiber is dispersed in the base material. (5) The mold material for precision casting according to claim 4, wherein the porosity of the magnesium oxide is 45 to 60%.