JPH08164464A - Die casting formed product - Google Patents

Abstract

PURPOSE: To obtain a comparatively smooth casting surface of a collapsible placed core without coating agent and to reduce the developing ratio of the defective of pressure leakage, etc., by cutting off the part to be cut with a projection material in a complex layer composed of the core material formed on the casting surface contacting with the collapsible placed core and a casting metal. CONSTITUTION: For example, the collapsible placed core is molded with a shell core molding method by using silica sand having about 250μm particle diameter and 7.0 Moh's hardness and set to a prescribed position as it is without coating the coating agent on this surface and a die casting is executed by using an aluminum alloy to form the product. After removing the collapsible placed core from the formed die casting product, the casting surface at the position after removing this core is observed and also, a part of the complex layer composed of the core material on the casting surface and the casting metal, i.e., the part to be cut is cut off by projecting a steel grid having 100-500μm grain diameter and about 56-68 HRC hardness and forming polygonal shape.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a die cast molded product formed by die casting using a collapsible core.

[0002]

2. Description of the Related Art Conventionally, in the case of die casting using a collapsible core, the casting surface of the portion in contact with the collapsible core is as smooth as possible and a molded product of high commercial value is cast. Therefore, a disintegrating core having a smooth coating layer formed by coating a coating agent on the surface of a core body made of a core material such as silica sand has been used.

However, when die-casting is performed using such a collapsible core, the surface of the collapsible core, that is, the portion to which the mold coating agent is applied (mold layer) has heat insulating properties. , The metal structure of the part that was in contact with the collapsible core was coarsened, and a chill crystal structure could not be formed on the surface of the casting surface, resulting in the problem that the die-cast molded product was apt to suffer from pressure leakage and shrinkage cracking. there were.

On the other hand, if die casting is performed without applying a mold coating agent on the surface, the surface roughness of the surface of the casting that has been in contact with the collapsible insert core becomes high and the commercial value is low. In addition to the storage, a composite layer that is hard and has excellent wear resistance composed of a core material and a cast metal is formed on the casting surface of the portion that was in contact with the collapsible storage core, so that the composite layer portion When the cutting process is applied to the, the workability is extremely deteriorated.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and the surface of the disintegrating insert core has a relatively smooth casting surface without a coating agent applied. In addition, it is possible to reduce the incidence of pressure leakage defects and shrink cracking defects, and at the same time, the core material and the cast metal formed on the surface of the casting surface where the collapsible core is in contact. It is intended to provide a die-cast molding product capable of imparting the same cutting workability as that of the other part to the composite layer part composed of and having a smooth surface (cast surface).

[0006]

The die-cast molding method according to claim 1 of the present invention which achieves the above object is a disintegrating step in which a core material having a small particle size is used for molding, and no surface coating agent is applied thereto. Of the composite layer composed of the core material and cast metal formed on the casting surface that was die cast using a core and was in contact with the collapsible placement core, the part to be machined to be processed later Is characterized by being scraped off with a shot material. Further, the die casting method according to the second aspect of the present invention is characterized in that the composite layer is formed smoothly by projecting a projection material onto the composite layer. And
The core material is made of silica sand having a particle size of 250 μm or less or a mixture of one or more selected from cera beads and zircon sand, and the particle size of the shot material is 100 μm.
It is characterized by using steel grit of ~ 500 μm.

[0007]

EXAMPLES Examples of the present invention will be described in detail below.
The invention is not limited to the embodiments described.

The die-cast molded product according to the present invention is molded by die-casting using a disintegrating core, such as an undercut product or a hollow product, and is formed on the surface of the casting surface in contact with the disintegrating core. A composite layer excellent in hard wear resistance made of a core material and cast metal is formed, and among the composite layers, only a portion to be processed to be post-processed is scraped off by a shot material, Alternatively, when a smooth surface is required, it is smoothed with a shot material.

The collapsible insert core used in the present invention is appropriately molded into a desired shape with a core material having a small particle size. Specifically, one or a mixture of two or more selected from silica sand, cera beads, and zircon sand having a particle size of 250 μm or less (particle size of AFS 80 or more) is used as the core material.

The particle size (particle size) of the core material used has a large effect on the surface roughness of the casting surface of the portion of the molded die-cast molded product that was in contact with the disintegrating core, so A small diameter is preferable. At this time, although the particle size is small, there is no problem, but if the particle size is 250 μm or more, the adhesion to the die-cast molded product, that is, the adhesion to the cast metal (for example, aluminum alloy) deteriorates, and so-called sand drop occurs, The thickness of the composite layer composed of the material and the cast metal is likely to be non-uniform, and the casting surface of the portion in contact with the collapsible insert core has a desired surface roughness (Ra).
= 20 μm or less, Rmax = 145 μm or less).

In the case of molding a collapsible placement core using the above core material, a conventionally known sand core molding method, for example, a shell core molding method, a cold box core molding method, or C
An O ₂ core molding method or the like can be applied.

Further, as the shot material used in the present invention,
It is preferable to use a steel grit having a hardness higher than that of the cast metal forming the die-cast molded product and having a toughness and a size (particle diameter) corresponding to the gap between the core materials in the composite layer. Specifically, the hardness is H _RC 42 to 68
A steel grit having a particle size of 100 μm to 500 μm is used. At this time, the grain size of the steel grit is 100
If the thickness is less than or equal to μm or greater than or equal to 500 μm, the core material forming the composite layer cannot be efficiently scraped off.

Then, the disintegrating core is set at a predetermined position of the mold as it is without applying a coating agent on its surface, and die casting is carried out to form a product. Then, the molten cast metal (for example, aluminum alloy) penetrates into the surface of the collapsible insert core and is composite-integrated with the core material,
After the disintegrating core was removed from the molded die-cast molded product, the core material and the cast metal were spread over the casting surface where the disintegrating core was in contact over a nearly constant thickness (depth). A die cast molded product having an integrated composite layer having a thickness of 400 μm to 500 μm is obtained.

Thereafter, of the composite layer portion of the die-cast molded product, the projection material is projected onto the composite layer portion only of the portion to be cut (the portion that needs to be cut later) to be post-processed. The composite layer of the part is shaved off, and the part to be cut, which is shaved off of the composite layer, is cut into a required shape by a normal cutting device to finish as a product.

Alternatively, if the surface of the composite layer is required to be smooth in the composite layer portion of the die-cast molded product, a projection material is projected onto the surface of the composite layer to smooth and smooth the product. Finish as.

Next, specific examples of the present invention will be described. Example 1. With a particle size of about 250 μm (particle size AFS80),
A disintegrating core is molded by a shell core molding method using silica sand having a Mohs' hardness of 7.0, and the disintegrating core is directly coated on the surface without applying a mold coating agent. Set in place on the mold, aluminum alloy (ADC12)
The product was molded by die casting using. After removing the collapsible insert core from the molded die-cast molding, observe the surface of the casting surface of the trace and also a part of the composite layer consisting of the core material of the casting surface and the casting metal (the part to be cut) ),
The particle size is about 180 μm-500 μm and the hardness is H _RC 56-
A 68-shaped polygonal steel grid was projected and scraped off. In addition, the projection condition at this time is pressure 0.5MP.
a, the projection time was 30 seconds.

Example 2. Particle size about 150 μm (particle size is AF
In S100), a collapsible core was molded by a shell core molding method using Cera beads having a Mohs hardness of 7.5, and a die cast molded product was obtained in the same manner as in Example 1.

Example 3. Particle size about 150 μm (particle size is AF
In S100), a zircon sand having a Mohs hardness of 7.0 was used to mold a collapsible insert core by a shell core molding method, and a die cast molded product was obtained in the same manner as in Example 1.

Example 4. Particle size is about 250 μm (particle size AF
In S80), a collapsible insert core was molded by a shell core molding method using silica sand having a Mohs hardness of 7.0, and the product was molded by die casting in the same manner as in Example 1. After removing the collapsible core from the molded die-cast molded product, the composite layer composed of the core material and the cast metal on the surface of the casting surface has a particle size of about 130 μm to 300 μm and a hardness of H _RC.
A round shaped steel grid of 42-50 was projected to smooth the surface of the composite layer. The projection conditions at this time were a pressure of 0.5 MPa and a projection time of 30 seconds.

Table 1 below summarizes the results of measuring the surface roughness of the casting surface, the sand removal test, and the thickness of the composite layer, etc., for the die-cast molded products molded in Examples 1 to 4 above. Show. In addition, the sand removal test assumes that the die cast product is actually used and observes that the core material falls out by heating, vibrating or adding liquid flow or corroding the surface of the casting surface. Is.

[0021]

[Table 1]

As can be understood from the results shown in Table 1 above, the die-cast molded articles of the respective examples are related to the surface roughness of the casting surface, the surface roughness (Ra) of the product cast by the gravity die casting method.
= 12 μm, Rmax = 121 μm) or slightly rough, and can withstand practical use, and the core material does not fall off from the die-cast molded product, and is composed of the core material and cast metal. A solid composite layer is formed.

[0023]

According to the die-cast molding method of the present invention, the following effects are exhibited. Since the mold disintegrating agent is not applied to the disintegrating core, the cost can be reduced accordingly. Since the mold disintegrating agent is not applied to the disintegrating core, a chill crystal structure is generated on the surface of the casting surface that is in contact with the disintegrating core, resulting in poor pressure leakage or shrinkage of the die-cast molded product. The incidence of cracking defects can be reduced. Since a material having a small particle size (250 μm or less) was used as the core material forming the collapsible core, the surface roughness of the casting surface in contact with the collapsible core was larger than that of other parts. It is possible to provide a die cast molded product having a smooth cast surface without being significantly deteriorated. Particularly, according to the die-cast molded product according to claim 1, in the composite layer in which the core material formed on the surface of the casting surface after the disintegrating insert core is removed and the cast metal are integrated, the portion to be cut is processed. Since it is shaved off with a shot material, it becomes possible to easily perform cutting work while providing the same cutting workability as other parts. Particularly, according to the die-cast molded product according to claim 2, a composite layer having a relatively rough surface roughness in which the core material formed on the surface of the casting surface after the disintegrating insert core is removed and the cast metal are integrated. Since it is formed smoothly, it is possible to provide a die-cast molded product having high commercial value.

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Claims (4)

[Claims] 1. A casting surface which has been in contact with the disintegrating core by die casting using a disintegrating core which is molded with a core material having a small particle size and whose surface is not coated with a coating agent. Of the composite layer consisting of the core material and cast metal formed in,
A die-cast molded product characterized in that the part to be cut that is post-processed has been scraped off with a shot material. 2. A casting surface which has been in contact with the disintegrating core by die casting using a disintegrating core which is molded with a core material having a small particle size and whose surface is not coated with a coating agent. A die-cast molded article, characterized in that the composite layer made of the core material and the cast metal formed in (1) is formed smoothly by projecting a shot material onto the composite layer. 3. The die-cast molded product according to claim 1, wherein the core material is composed of one kind or a mixture of two or more kinds selected from silica sand having a particle size of 250 μm or less, cera beads, and zircon sand. 4. The projection material has a particle size of 100 μm to 50 μm.
The die cast molded product according to claim 1 or 2, which is a steel grit having a diameter of 0 µm.