JPS6224838A - Production of casting having excellent casting surface - Google Patents

Abstract

PURPOSE:To prevent casting defects and to obtain a casting having an excellent casting surface by intensifying the adhesion between a ceramic slurry and backup mold and preventing the intrusion of the gas generated from the casting mold into a molten metal during pouring. CONSTITUTION:Foamed polystyrene A is stuck to a pattern B to form the pattern larger than the pattern B. The pattern is set together with a molding flask and the backup mold is formed of org. self-curing sand together with cavities D, a discharge pipe E and slurry pouring ports C. The pattern is then removed and hot wind is blown through the discharge pipe E to expend the foamed polystyrene in the cavities D. The slurry compounded with ceramics and gelation accelerating agent is poured through the pouring port C and at the same time air is discharged from the pipe E to suck the slurry toward the org. self-curing sand. The pattern B is removed at the point of the time when the slurry gels; thereafter the combustible material of the ceramic layer is burned and the ceramic layer is calcined. The cope and drag are then set and the molten metal is poured into the mold. The generated gas is sucked from the pipe E simultaneously with the pouring.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a method for manufacturing a casting with an excellent casting surface, and more specifically, in the process of forming a composite mold, the adhesion strength between a ceramic slurry and a backup casting is improved. Furthermore, the present invention relates to a mold manufacturing method that prevents gas generated from the mold from penetrating into the molten metal alloy during full pouring of A-grade metal, and makes it possible to manufacture castings with excellent casting surfaces.

<Prior Art> There are broadly two methods for making ceramic molds, which are used depending on the size, shape, etc. of the casting to be manufactured.

(1) Ceramic mold This is a method used to manufacture single-type relatively small castings, in which a model and a mold that can obtain an appropriate thickness of the mold are set on a surface plate.

After setting, a slurry is made with the required amount of refractory (ceramic), binder, and gel accelerator, and this is poured into the formwork.

Once the gelation of the slurry is complete, the mold is removed and the model is cut out. After cutting the mold, the flammable material in the mold is ignited and then fired.

In this case, even small castings with complex shapes and large irregularities may suffer from uneven gelation and uneven temperature distribution within the ceramic layer during firing.
Cracks occur in the ceramic layer, and the cracks become cracks on the surface of the casting, so that it may not be possible to obtain a casting with a smooth surface.

One way to prevent this ceramic layer from cracking is to
There is a composite molding method that makes the thickness of the ceramic layer uniform.

(2) Composite molding method This method is used when manufacturing relatively large castings, and aims to reduce costs and strengthen mold strength by reducing the amount of ceramic material used.

The manufacturing process is shown below.

■Set a model larger than the product model and a casting flask on the surface plate.

■Mold the backup material using C02 sand, hard molder, etc.

■Cut out a large model.

■Set the product model on the surface plate.

Cover the product model with a small backup mold and pour the slurry between them.

■Cut out the product model.

■After igniting and burning the flammable substances contained in the ceramic layer, it is fired.

In the above method, the slurry is simply poured into the gap between the backup mold and the product model, and the adhesion between the backup material and the slurry is insufficient, and when the product model is cut out, the gelled ceramic of the backup material and slurry There is a problem that the layers may separate or cracks may occur in the ceramic layer.

Furthermore, when using Co2 sand, organic hard sand, etc. as a back-up material, it may be impossible to fire the ceramic layer due to the characteristics of the sand. Then, the surface stability of the mold is lost, and sufficient mold strength cannot be obtained. Like this,
If the ceramic layer is not sufficiently fired and the A-miai molten metal is poured into the mold, moisture and gas generated from the ceramic layer and backup mold will enter the Al1 alloy and cause the mold to break. There's a problem.

Problems to be Solved> The present invention was made in view of the problems of the conventional composite molding method as explained above. The present invention provides a mold manufacturing method that does not cause mold separation or cracking of the ceramic layer, and has excellent surface quality and internal quality regardless of the type of back-up material.

Measures to Solve the Problems The above problem can be solved by forming a gap between the product model and the backup mold, covering the product model with the backup mold, and filling the gap with a slurry containing a mixture of ceramic and binder. In a casting manufacturing method, the slurry is poured and gelled to form a ceramic layer, the product model is cut out, the ceramic layer is fired, and then an upper mold and a lower mold are set and hot water is supplied; A cavity or a well-ventilated part (hereinafter referred to as the "cavity part") is provided inside the backup mold at a required distance from the product model, and a pack is provided between the cavity or the well-ventilated part. The present invention is solved by a method for producing a casting having an excellent casting surface, which is characterized by communicating the outside of the apple lower mold and reducing the pressure in the hollow body before or at the same time as pouring the slurry.

The present invention will be explained in more detail below.

To form a gap between the product model and the backup mold, cover the product model with the backup mold, provide a cavity, and communicate the cavity with the outside of the punch-up mold, for example, the following steps can be taken: Just do it like this.

First, styrofoam, vinyl, sheet wax, etc. are pasted onto the product model to make it larger than the product model.

A model larger than this product model and a casting flask are set on a surface plate, and a backup mold is formed using CO2 sand, organic self-hardening sand, etc. When molding this backup mold #I, a material that can form a cavity and an exhaust pipe are placed in the backup mold. Materials that can form cavities include styrofoam and wax, which disappear when heated, and materials with good air permeability include:
Ceramic foam etc.

These materials only need to be depressurized by a vacuum pump or vacuum cleaner through an exhaust pipe, and should be made of materials with more air permeability than the back-up material, or by heating or other means after molding the pump mold. The material is not limited to the above-mentioned materials as long as it can be eliminated by the following methods.

The distance between the cavity and the product model is preferably 10 to 100 mm; if it is shorter than 10+sm, the organic self-hardening sand part may break due to the pressure of the molten metal during the supply of water after forming the cavity. Moreover, if the distance is 100 mm or more, the suction effect will decrease.

In this way, a backup mold provided with a cavity or a well-ventilated portion is manufactured. After that, the Styrofoam, vinyl, wax, etc. pasted on the product model are removed and the product model is set on a surface plate, and the product model is covered with the backup mold that has already been formed.

Below, the function of the cavity provided in the backup mold will be explained in detail.

Action〉 After placing the backup mold on the product model, separately
Refractories (ceramics), binders.

A slurry containing a gelling accelerator is made and poured into the pouring port. Before or at the same time as pouring the slurry, a pressure reducing device such as a vacuum pump is operated to reduce the pressure in the cavity. Due to this reduced pressure, a force is applied to suck the slurry toward the backup #4 mold through the backup mold, and the slurry infiltrates into the sand grains of the backup mold, thereby strengthening the adhesion between the henk-up mold and the slurry. .

When gelation of the slurry is completed, the product model is cut out. At the time of mold removal, the adhesiveness between the backup mold and the gelled ceramic layer of the slurry is strong, so that peeling or cracking of the ceramic layer at the interface can be prevented.

Furthermore, for products whose shapes are complex and the product model and the ceramic layer cannot be separated easily, smoother mold cutting can be achieved by blowing air through the cavity.

After cutting out the product model, the combustible material contained in the ceramic layer is ignited and then fired.

After firing, the hot water supply work is performed.The materials manufactured using the composite mold are A pattern, A pattern alloy, Zn*
It is applicable to all casting materials such as Zn alloy and Fe alloy. Among these materials, A is considered to have a particularly negative effect on product quality, such as gas generated from the mold after hot water is supplied.
When manufacturing an n-An alloy, gas, moisture, etc. generated from the mold can be sucked out by reducing the pressure in the mold using a vacuum pump or the like through the cavity.

By suctioning these generated gases, moisture, etc., AM
- It is possible to prevent infiltration into the A1 alloy, eliminate casting defects on the surface and inside, and produce castings with excellent casting surfaces.

<Example> An embodiment of the present invention is shown in FIGS. 1 to 5.

Fig. 1 shows a state in which Styrofoam A is attached to a product model to make it larger than Product Model B. In this case, the thickness of Styrofoam A is preferably 2 to 4hm, 2rs.
If it is thinner than ts, when the slurry is poured, there will be insufficient flow and some parts will not be filled with the slurry. Also, 4
If the thickness is 0 mm or more, the amount of slurry will increase, which will increase the cost, and the ceramic layer will also be more likely to break.

Figure 2 shows the model and casting flask in Figure 1 set on a surface plate.
A state in which a cavity D, an exhaust pipe E, and a slurry inlet C are molded using organic self-hardening sand is shown. In this case, foamed polystyrene with a thickness of lhm was used for the cavity, and the distance from the product model B was set to 20 to 40III11.

FIG. 3 shows a state in which an upper mold is formed from organic self-hardening sand together with the presser F and sprue G.

Thereafter, the model with Styrofoam A pasted on the product model B is cut out. Hot air is blown through the exhaust pipe E of the cut mold to burn out the Styrofoam that was placed as a cavity filler. In this case, the mold can be placed in a firing furnace and the Styrofoam can be burned out.

The mold with the cavity formed in this way is set on a surface plate as shown in Fig. 4, and a slurry prepared by separately mixing and kneading ceramic, ri, and a gelling promoter is injected from the pouring port C. do. In this case, if the product is large, several inlets may be provided, and if the product is small, only one inlet is required.A vacuum pump connected to the exhaust pipe E is operated at the same time as or immediately before pouring the slurry. This exhaust action draws the slurry towards the organic self-hardening sand and strengthens the adhesion of the slurry with the organic self-hardening sand backup mold.

When the gelation of the slurry is completed, the vacuum pump is stopped, and then the product model B is removed from the mold.

After cutting, the combustible material contained in the ceramic layer is ignited and then fired. After firing, as shown in FIG. 5, the upper mold is set on the lower mold, and A1 alloy is supplied with hot water.

Operate the vacuum pump at the same time or before hot water supply. This exhaust action sucks gas generated from the mold due to the heat of the A exchange molten metal, thereby preventing gas from penetrating into the An molten metal.

The A1 alloy castings cast by the above-mentioned process had excellent casting surfaces of 6 to +23, had no casting defects, and were sound.

<Effects of the Invention> As described above, the present invention has an excellent casting surface of 6 to 12S, no cracking due to cracks in the ceramic layer, no casting defects due to debris generated from the mold, and the casting surface can be improved without modification. Can be used as a product.

In other words, castings that were conventionally used as products by hand finishing or machining the casting surface can now be used with the casting surface, significantly reducing costs and shortening the construction period. This is the result.

[Brief explanation of the drawing]

1 to 5 are cross-sectional views for explaining one embodiment of the present invention. A... Styrofoam, B... Product model, C... Slurry inlet, D... Cavity, E... Exhaust pipe, F
・・Press i, ・G・・Gate, H・・Slurry, ■・・・Ceramic layer. Figure 1 Δ Figure 2 Figure 3

Claims (1)

[Claims] 1. A gap is formed between the product model and the backup mold, the backup mold is placed over the product model, and a slurry containing a mixture of ceramic and a binder is poured into the gap, and the slurry is gelled. In a casting manufacturing method in which after forming a ceramic layer, the product model is cut out, the ceramic layer is fired, and then an upper mold and a lower mold are set and hot water is supplied; , providing a cavity or a well-ventilated part at a position a required distance from the product model, and communicating the cavity or well-ventilated part with the outside of the backup mold;
A method for producing a casting having an excellent casting surface, characterized in that the hollow body is depressurized before or simultaneously with pouring the slurry. 2 Claim 1, which reduces the pressure of the hollow body during hot water supply
A method for manufacturing a casting with excellent casting surface as described in Section 1.