JPS63248554A - Sand core for pressure casting - Google Patents

Abstract

PURPOSE:To offer a sand core, withstanding casting pressure and to provide the sand core without any breakage by coating surface of the sand core by metal and making thickness of the coating near inlet of molten metal to thicker than the other part. CONSTITUTION:The sand core body 1 uses silica sand, etc., and is formed by using phenol resin, etc., as organic binder. The coating 2 of aluminum alloy, etc., is formed on the sand core body 1 by thermal spraying. Next, by forming coating film 3 of a second layer through dipping, the film thickness is made to about 2 mm. The coating film 5 of the core body 1 near the inlet 4 of the molten metal repeatedly executes the thermal spraying and dipping, to make to about 5 mm film thickness. This sand core 6 is set in a movable die 7 and together with a fixed die 8, in the case of executing die casting, the sand core tolerates the cast pressure by existence of the metal coating, and the breakage of the sand core can be prevented.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a sand core used when forming an undercut shape or a hollow shape during pressure casting of aluminum alloy such as die casting. .

[Prior Art] Generally, when manufacturing various products by casting, die casting is widely used as a pressure casting method due to its advantages in terms of improved productivity and the like.

However, when manufacturing a casting in which a part of the product shape has a complicated cavity or undercut by die casting, a drawn core cannot be used as the core. Therefore, the use of a sand core with good collapsibility has been considered as an alternative, but this has completely contradictory functions: it can withstand the high casting pressure of the die-casting method, and has good disintegration after casting. It must have the following at the same time. Therefore, a method was devised in which the sand core was coated with metal to prevent the sand from collapsing during casting, and the metal coating was then poured into the product after casting.

[Problems to be Solved by the Invention] However, if the thickness of the coating is thin, the coating is likely to be eroded at the molten metal inlet, which may cause the molten metal to penetrate into the core sand and cause partial damage to the core. be.

[Means and effects for solving the problem] If the thickness of the metal covering the sand core is thick, the coating will not be completely melted while the molten metal penetrates into the core and collides with the core. Therefore, there is no possibility that molten metal will be poured into the core sand. However, since it is difficult to thickly coat the entire core in terms of productivity, cost, etc., it was concluded that only the area around the molten metal inlet should be thickly coated.

That is, after applying aluminum or an aluminum alloy to the surface of a sand core formed by organic binder or press molding, or by thermal spraying, etc., the entire core is uniformly coated, and then the area around the molten metal inlet is coated again with the same method as required. Cover until thick. The coated metal has sufficient strength and can withstand high casting pressures such as die casting, and the coating is thick near the molten metal inlet where the molten metal directly shines, so it has sufficient resistance to melting damage. In addition, if a slurry-like liquid containing powder with mold releasability such as mica or frogstone is applied or impregnated on the surface layer or surface of the sand core before coating with metal, it is possible to remove the core from the product after casting. When taken out, the metal coating and core sand easily separate.

[Example] One embodiment of the present invention will be described below.

The aggregate for the sand core 1 is silica sand, zircon sand, chromite sand, high alumina sand, Cerabeads, etc., and the organic binder is a shell mold binder such as thermosetting phenol resin or unsaturated polyester resin, or a chemical. A core is molded using a cold box binder such as a reaction-curable phenolic resin.

Powder of mica or frogstone, which is a thermally and chemically stable substance that has lubricating properties and has no affinity with the coated metal, is used as a water-soluble powder containing phenolic resin methyl cellulose or polyethylene oxide. It is coated with a slurry dispersed in an organic binder and dried.

A coating 2 of aluminum or aluminum alloy is formed on the entire surface of the sand core body 1 thus formed by thermal spraying. Next, when a second layer of coating 3 is formed by dipping, the thickness is approximately 2 mm, but the coating 5 on the sand core body 1 near the molten metal inlet 4 is repeatedly sprayed and dipped to a thickness of approximately 5 mm. do.

The sand core 6 thus obtained is set in the movable mold 7, combined with the fixed mold 8, and a JIS ADC is placed in the cavity 9.
12 aluminum alloy at a pouring temperature of 750°C and a casting pressure of 20
Die casting was performed under the conditions of 0 to 400 Kg/cm'. After casting, the sprue was cut and sand blasted to remove sand from the sand core. As a result, a plug layer formed by the sand particles and the casting material mixed between the sand particles occurred, and a layer of sand was formed due to the high casting pressure. There was no damage to the core, the collapsibility was good, and the core sand could be completely removed. Furthermore, when sand baking was performed in a furnace for a predetermined time after cutting the sprue, the resin in the sand core was thermally decomposed, making removal of the core sand by sandblasting even easier. Furthermore, when the product was cut and the cross section of the core portion was observed, it was found that the metal coating of the core was completely bonded to the product body.

In FIG. 1, 10 is an injection sleeve, 11 is an injection plunger, and 12 is a molten metal.

[Effects of the Invention] As is clear from the above explanation, when pressure casting such as die casting is performed using the pressure casting method according to the present invention, the metal coating film can withstand the casting pressure and prevent the sand core from being damaged. At the same time, the core sand can be easily removed after casting. Furthermore, since the metal coating is cast inside the product, it is easy to make the inner surface of the cavity or undercut of the product of a different material depending on requirements.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view showing a state in which the core of the present invention is set in a mold. 1...Sand core body, 2,3.5...Coating, 4
... Molten metal inlet, 6... Sand core, 7... Movable mold, 8... Fixed mold, 9... Cavity.

Claims (1)

[Claims] 1. A sand core for pressure casting, characterized in that the surface of the sand core is coated with metal, and the thickness of the coating is thicker in the vicinity of the molten metal inlet than in other parts.