JPS63252661A - Sand core for pressure molding - Google Patents

Abstract

PURPOSE:To improve durability against a casting pressure and to improve product quality by forming an impregnated layer or coated film of powder having a mold releasing property on the front layer or the surface of a sand core for pressure casting. CONSTITUTION:The powder of titanium oxide, lime, calcium carbonate and gypsum powder, etc., coated with a water soluble org. binder such as phenolic resin is formed as the surface layer on the surface of the molded sand core body 2. If necessary, a thermally sprayed metallic film is further formed thereon. The product quality is improved and the working efficiency is improved by the member constituted in such a manner.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a sand core for pressure casting, and is particularly suitable for forming undercut shapes or hollow shapes during pressure casting of aluminum alloys such as die casting. The present invention relates to a sand core for pressure casting suitable for use.

[Prior Art] Generally, when manufacturing various products by a casting method, a die-casting method is widely used as a pressure casting method due to its advantages in terms of improved productivity and the like. By the way, when manufacturing castings with complex cavities or undercuts in part of the product shape using the die casting method, a drawn core cannot be used as the core, and a collapsible core is used instead. A sand core of good quality is used.

As a collapsible sand core that forms an undercut or a cavity in a casting, a sand core made by hardening foundry sand with a phenol resin or the like has conventionally been used.

[Problems to be solved by the invention] By the way, in order to cast a product with a clean casting surface and good dimensional accuracy using the die casting method using a sand core, ■ It must have sufficient strength to prevent damage to the child.

■ Molten metal should not be inserted between the sand particles of the sand core.

■ Good disintegration properties of the sand core after die casting.

etc., but a core that satisfactorily satisfies these characteristics has not been provided.

[Means for Solving the Problems] The sand core for pressure casting of the present invention is characterized in that an impregnated layer or coating film of powder having mold releasability is formed on the surface layer or surface.

[Function] By forming a coating layer of powder with mold releasability on the surface of the sand core, the core is reliably protected during casting due to the protective effect and mold release effect of the coating layer, and after casting. In this case, core sand can be easily removed. For this reason, (1) the core becomes a high-strength core that can withstand high casting pressure;

■ The surface roughness and dimensional accuracy of the resulting product are extremely good.

■ The occurrence of defects such as cracks due to the penetration of molten metal into the contact surface between the cast metal and the sand core is prevented.

■ Good disintegration properties of the sand core after die casting.

■ It is possible to reduce the cost of cores.

The following effects are achieved.

[Example] Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view showing an embodiment of the sand core for pressure casting of the present invention.

As shown in the figure, in the sand core 1 for pressure casting of this embodiment, an impregnated layer or coating film 3 of powder having mold releasability is formed on the surface layer or surface of the sand core body 2. A metal sprayed film 4 is further formed on the surface.

In order to manufacture the sand core 1 for pressure casting of the present invention, first, the sand core body 2 is molded using an organic binder or press molding according to a conventional method.

As the aggregate of the sand core body 2, silica sand, zircon sand,
Chromite sand, high alumina sand, Cerabeads, or the like can be used. Further, as the organic binder, a shell mold binder such as a thermosetting phenol resin or an unsaturated polyester resin, or a cold box binder such as a chemical reaction hardening phenol resin can be used.

The surface of the molded sand core body 1 is coated with a group consisting of titanium oxide, lime, calcium carbonate, and gypsum, which are thermally and chemically stable substances that have lubricity and have no affinity with the molten metal to be cast. A powder consisting of at least one selected from
For example, by applying and drying a slurry dispersed in a water-soluble organic binder containing phenol resin, methyl cellulose, polyethylene oxide, etc., and repeating this process several times as necessary, the sand core body 2 is formed. An impregnated layer or coating film 3 of powder having mold releasability is formed on the surface layer or surface.

An impregnated layer or coating film of a substance with such mold release properties is
It is preferable to provide it on at least the surface of the sand core that is likely to come into contact with the molten metal, but it may also be provided only on the undercut or cavity forming parts of the core where mold releasability and strength are particularly problematic. Alternatively, it may be formed on the entire surface of the core.

In addition, the thickness of the impregnated layer or coating film should be adjusted so that the core has sufficient strength and mold releasability, and the size and shape of the core are within the range that does not adversely affect costs or casting operations. It will be determined as appropriate.

In this way, an impregnated layer or coating of powder having mold releasability [3
After forming, a metal sprayed film 4 is formed as necessary. The metal sprayed film 4 reinforces the strength of the core, and
It is possible to more reliably prevent molten metal from entering between the core sand particles.

In this case, plasma spraying or gas spraying is used as the thermal spraying method, and various materials such as aluminum or various aluminum alloys can be used as the thermal spraying material, but the most desirable method is to use the sand core. It is an alloy with the same composition as the casting material used during casting.

An experimental example will be explained below.

Experimental Example 1 Titanium oxide powder was dispersed in a binder solution on the surface of a sand core body obtained by molding using aggregate (JIS No. 7 silica sand) and an organic binder (thermosetting phenol resin) using a conventional method. The resulting slurry was applied and dried, and this process was repeated five times to form a titanium oxide coating.

The obtained sand core 10 was set in a mold as shown in Fig. 2, and JIS ADCI 2 aluminum alloy was poured at a temperature of 750°C and a casting pressure of 200 to 400 kg /
Die casting was carried out under the conditions of ``crn''.

In addition, in FIG. 2, 11 is a movable mold, 12 is a fixed mold, 1
3 is a cavity, 14 is a molten metal, and 15 is a sprue.

After casting, when the sprue 15 was cut and the sand was removed from the sand core by sandblasting, a plug layer formed by the aluminum mixed in between the sand particles and the sand particles was formed, and a layer due to the high casting pressure was generated. There was no damage to the core, the disintegration was good, and the sand core could be easily and completely removed.

Experimental Example 2 On the surface of the core produced in Experimental Example 1, JISADC12 aluminum alloy was thermally sprayed to form a thermally sprayed layer with a thickness of 1 mm.

When casting was carried out in the same manner as in Experimental Example 1 using the obtained sand core, there was no insertion of molten metal or damage to the core, and the sand core had good disintegrability and could be easily removed. was completed.

In addition, when the sprue was cut, sand-baked in a furnace for a predetermined period of time, and then sandblasted, the resin in the sand core was thermally decomposed, making sandblasting even easier to remove the sand core. As a result, we were able to obtain die castings that were extremely smooth and had good dimensional accuracy.

[Effects of the Invention] As detailed above, the sand core for pressure casting of the present invention has an impregnated layer or a coating film of a powder having mold releasability on the surface layer or surface, and is suitable for use in sand cores. Since the core is given sufficient strength and mold releasability, ■ it can withstand high casting pressure, and the core will not be damaged.

■ The resulting product has a beautiful casting surface and good dimensional accuracy.

■ No defects such as molten metal penetration or cracks occur.

■ Good disintegration properties after casting, and the core can be easily removed.

Effects such as these are produced.

Therefore, according to the sand core of the present invention, even castings with complex cavities or undercuts can be manufactured efficiently and at low cost by high-pressure casting methods such as die casting methods. And you can get high quality products.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an embodiment of the sand core for pressure casting of the present invention, and FIG. 2 is a sectional view showing the casting method in Experimental Example 1. DESCRIPTION OF SYMBOLS 1...Sand core, 2...Sand core body, 3...Powder impregnated layer or coating film having mold releasability, 4...Metal sprayed film.

Claims (3)

[Claims] (1) A sand core for pressure casting, characterized in that an impregnated layer or coating film of a powder having mold releasability is formed on the surface layer or surface. (2) The powder having mold releasability is one or two selected from the group consisting of titanium oxide, lime, calcium carbonate, and gypsum.
The sand core for pressure casting according to claim 1, characterized in that the sand core is of different types or more. (3) The sand core for pressure casting according to claim 1 or 2, wherein the impregnated layer or coating film is coated with a metal sprayed film.