JPS6323867B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a casting chill used for casting products of complex shapes and large differences in wall thickness, such as compressor wheels for turbochargers.

Conventionally, for products with large walls such as compressor wheels for turbochargers, where the blade part is thin and the hub part is thick, the flow of water to the blade part c of the product cavity b in mold a is improved as shown in Figure 1. In general, mold a is preheated for the purpose of mold a, and vacuum casting is performed using a chiller e to prevent shrinkage cavities and coarsening of crystal grains in the hub portion d.
A very delicate thermal design is required; if the heat capacity is small, the effectiveness of the chiller e will be reduced, and if the heat capacity is large, the molten metal in contact with the chiller will solidify rapidly, resulting in poor flowability. As a result, poor hot water circulation or poor water quality occurs in the blade portion c near the chiller e.

The object of the present invention is to provide a chiller that eliminates such inconveniences, and includes a recess with a depth of 0.1 to 0.2 mm on the surface of the chiller body that comes into contact with the molten metal.
It is characterized by being formed to occupy 50% of the contact surface.

Next, the present invention will be explained with reference to the embodiments shown in FIGS. 2 and 3.

In Fig. 2, reference numeral 1 indicates a plaster mold for a compressor wheel formed by a plaster molding method, a rubber molding method, etc., and the mold 1 has blades corresponding to the shape of the compressor wheel connected to a sprue 2 at the top of the mold. A product cavity 3 having a portion 3a and a hub portion 3b is provided, and a chiller main body 4 is assembled to the bottom surface of the hub portion 3b of the cavity 3. The chiller body 4 was formed with fine recesses 5 as shown in FIG. 3 on the surface that comes into contact with the molten metal.

According to this, in the initial stage of pouring from the sprue 2, the molten metal contacts only the contact surface where the recess 5 is not formed, as shown in FIG. Since the heat conduction of the molten metal is suppressed to a low level, deterioration of flowability due to cooling of the molten metal is prevented as much as possible, and the flow of the molten metal to the blade portion 3a is improved.

When the recess is filled with molten metal, the contact area with the molten metal increases in the recess due to the pressure of the molten metal, and the cooling effect by heat conduction to the main body 4 is fully exerted.

Figure 4 shows a conventional cooling metal whose contact surface with the molten metal is a smooth surface, and the occupancy of the contact surface of the recess 5 is 50%, and the depth of the unevenness 5 is 0.1 mm and 0.2 mm according to the present invention. Using a chilled metal, make the mold as shown in Figure 5.
The results of a comparative experiment in which 710°C molten aluminum was poured and the temperature change over time at point A of the chiller body 4 was measured are shown. It can be seen that both the temperature rise at the initial stage of pouring and the temperature drop after the temperature rise are more gradual than in the above. Note that if the depth of the recess 5 is further increased beyond 0.2 mm, there will be little difference from the conventional one.

In the chiller of the present invention, the reason why the temperature rise is gradual is that the amount of heat transferred to the chiller at the initial stage of pouring is small, and the reason why the temperature drop is gradual is that the amount of heat transferred to the chiller is small as described above. This is thought to be due to the increase in the amount of heat radiated by the molten metal into the recess, which balances the amount of heat dissipated from the chiller to the outside.

In addition, in conventional smooth cooling metals, the amount of heat transferred to the cooling metal at the initial stage of pouring is large, and the molten metal rapidly solidifies, the surface tension of the molten metal becomes strong, and so-called scratches occur on the surface. It is thought that heat conduction from the molten metal to the chilled metal deteriorates, and the amount of heat released from the chilled metal to the outside exceeds the amount of heat transferred from the molten metal, resulting in a relatively rapid temperature drop after the temperature rise.

Next, a casting test according to the present invention will be explained.

The chilled metal has a concave portion 5 with a depth of ±0.2 mm formed at a occupancy rate of approximately 50% by texturing etc. on the molten metal contact surface of the main body 4, and this is assembled into the mold 1 as shown in the second figure. Preheat to approximately 300℃ with the battery attached, then
When an aluminum alloy equivalent to AC4C was vacuum-cast at approximately 730°C, no poor hot water flow or water leakage was observed at the tip of the blade portion 3a adjacent to the chiller body 4, and no hot water was observed inside the hub portion 3b. A good product with a sound structure was obtained.

As described above, according to the present invention, the recess 5 with a depth of 0.1 to 0.2 mm is provided on the surface of the chiller body 4 that comes into contact with the molten metal.
occupies 50% of the contact surface, the molten metal at the initial stage of pouring contacts approximately half of the contact surface of the chiller body 4 and reduces the amount of heat transferred to the chiller body 4. The cooling metal body 4 is made smaller to prevent deterioration in flowability due to cooling of the molten metal, and then increases the amount of heat transferred to the cooling metal body 4 by infiltration of the molten metal into the recess 5.
The amount of external heat dissipation and the temperature drop of the molten metal are balanced, so that even products with complex shapes can be cast without causing poor molten metal flow and with a sound internal structure.

[Brief explanation of drawings]

Fig. 1 is a cut-away side view of a conventional example, Fig. 2 is a cut-away side view of one example of the chiller of the present invention in use, Fig. 3 is an enlarged cut-away side view of its main parts, and Fig. 4 is a cut-away side view of an example of the cooling metal of the present invention. A diagram showing the results of a comparative test for gold, and FIG. 5 is a cutaway side view of the apparatus used in this test. 4...Cold metal body, 5...Irregularities.

Claims (1)

[Claims] 1. On the contact surface of the cooling metal body with the molten metal, a depth of 0.1~
A cold mold for casting, characterized in that a recess of 0.2 mm is formed with an occupation rate of 50% on the contact surface.