JP3285063B2 - Die casting method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a die casting method for molding a product by die casting using a collapsible core.

[0002]

2. Description of the Related Art In the case of die-casting using a collapsible core, conventionally, a mold wash has been applied to the surface of a core body in order to obtain a cast product having a smooth casting surface.

However, since the surface of such a collapsible core, that is, the portion (coating layer) to which the coating agent is applied has heat insulation properties, the portion of the core that is in contact with the collapsible core is insulated. The metal structure was coarsened and a chill crystal structure was not formed on the casting surface, and as a result, there was a problem that the casting product was liable to have poor pressure leakage and poor cracking.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and has been made to produce a chilled crystal structure on a casting surface in contact with a collapsible placing core, thereby producing a cast product. Casting products that can be cut easily by giving the part that was in contact with the collapsible core with the same machinability as other parts, while reducing pressure leakage failure and shrinkage failure. It is an object of the present invention to provide a die casting method capable of forming.

[0005]

Means for Solving the Problems A die-casting method of the present invention for achieving the above object is a die-casting method for forming a product by die-casting using a collapsible core, which comprises a collapsible core. Is molded using a core material having a Mohs' hardness of 6 or less, and the collapsible core is set at a predetermined position of a mold without applying a coating agent on its surface and cast. It is a characteristic.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A collapsible core according to the present invention is formed using a core material having a Mohs hardness of 6 or less. Specifically, it is formed into a required shape using chromite sand having a Mohs hardness of 5.5.

In the case of forming a collapsible core using the above core material, a conventionally known sand core forming method, for example, a shell core forming method, a cold box core forming method, a CO ₂ core forming method, or the like. Can be applied.

[0008] The particle size (particle size) of the core material used affects the surface roughness of the casting surface of the cast product in contact with the disintegrating core, but the adhesion to the cast product is poor. Is 1μ
m is preferably in the range of 400 μm,
At this time, there is no problem with the small particle size, but if it is 400 μm or more, the adhesion to the cast product is poor, and it becomes impossible to integrate the core material and the cast metal of a certain thickness.

The disintegratable core is set in a predetermined position of a die without applying a coating agent on the surface thereof, and is subjected to die casting to form a product.
Then, the molten metal penetrates into the surface of the collapsible core, and is integrated with the core material in a composite manner. A cast product in which the core material and the cast metal are integrated over (depth) can be obtained.

Next, a specific embodiment of the present invention will be described. Embodiment 1 FIG. The particle size is AFS52 (particle size about 400 μm),
Using a chromite sand having a Mohs hardness of 5.5, a collapsible core is formed by a shell core molding method, and the collapsible core is directly molded into a mold without applying a coating agent on its surface. And die-cast using an aluminum alloy (ADC12) to form a product. After removing the collapsible core from the molded casting product, the surface of the casting surface was observed. When the surface roughness of the casting surface was measured,
Ra = 23 μm and Rmax = 184 μm. This value is the surface roughness (R) of the product cast by gravity mold casting.
a = 12 μm, Rmax = 121 μm), which is sufficient for practical use. In addition, when a sand removal test was performed on the cast product by applying vibration or corroding the casting surface, no core material came off. Further, when the metal structure of the casting surface was examined, as shown in the micrograph of FIG. 1, the chill crystal structure covered the core material (chromite sand), and the core material and the cast metal were integrated. Was. In this micrograph,
The portions that appear black are the fine particles of the core material, and the portions that appear white are aluminum (ADC12). Further, when the cutting workability of the casting surface in contact with the collapsible placing core was tested, the flank wear width of the tool when the cutting workability was 200 min at a peripheral speed of 150 m / min was 0.08 mm,
Although it is slightly inferior to the case where ADC12, which is a normal aluminum alloy, is cut (the flank wear width of the tool becomes 0.005 mm when the cutability is 200 min at a peripheral speed of 150 m / min), good cutability is obtained. Indicated.

Embodiment 2 FIG. Particle size is AFS71 (particle size about 30
A collapsible core was formed by a shell core forming method using chromite sand having a Mohs hardness of 5.5 and a Mohs hardness of 5.5, and a product was cast in the same manner as in Example 1. When the surface roughness of the casting surface was measured, Ra = 10 μm, Rma
x = 100 μm, which was almost equivalent to a product cast by gravity mold casting. Also, the core material does not fall off from the cast product, and the metal structure on the casting surface is
As shown in the photomicrograph of FIG. 2, it was almost the same as that of the first embodiment. And, regarding the machinability of the casting surface in contact with the collapsible core, the peripheral speed was 150 m / mi
The flank wear width of the flank wear of the tool when the cutting workability was 200 min at n was 0.075 mm, which was almost the same as that of the first embodiment.

[0012]

According to the die casting method of the present invention, the following effects can be obtained. Since the mold wash is not applied to the disintegrating core, the cost can be reduced accordingly. Since the disintegrating core is not coated with a mold wash, a chilled crystal structure is formed on the surface of the casting surface in contact with the disintegrating core, resulting in poor pressure leakage and cracking of the cast product. Defects can be reduced. After removing the collapsible core from the cast product, a composite layer is obtained in which the core material and the cast metal are integrated over a certain thickness (depth) on the casting surface. Since a material having a hardness of 6 or less is used, cutting can be easily performed while maintaining the same machinability as other portions.

[Brief description of the drawings]

FIG. 1 is a micrograph showing a metal structure (× 100) of a casting surface of a product cast by a die casting method (Example 1) of the present invention.

FIG. 2 is a micrograph showing a metal structure (× 100) of a casting surface of a product cast by the die casting method (Example 2) of the present invention.

Claims (1)

(57) [Claims] 1. A die-casting method for forming a product by die-casting using a collapsible core, wherein the collapsible core is molded using a core material having a Mohs hardness of 6 or less.
A die-casting method characterized in that the disintegratable core is set at a predetermined position in a mold and cast without applying a mold-coating agent to its surface.