JP4675474B2 - Mold for casting - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a casting mold used for casting various parts.
[0002]
[Prior art]
In the case of a casting mold used for casting a vehicle wheel, the cavity portion close to the gate is thicker than the other portions, so it is necessary to efficiently cool the molten metal filled in the cavity.
[0003]
Therefore, conventionally, as shown in FIG. 6, an annular cooling groove 11 is provided in a portion of the lower mold 2 surrounding the gate entrance 1 and the annular opening 11a of the cooling groove 11 opened on the opposite side of the cavity 5a. Was hermetically welded by a flat plate-shaped sealing lid 12 c and cooled by flowing cooling air through the cooling groove 11.
[0004]
[Problems to be solved by the invention]
However, in the conventional configuration, stress is applied to the welded portion of the sealing lid 12c due to cold heat during casting, and cracks may occur at an early stage particularly in the welded portion A. In that case, the cooling air flowing through the cooling groove 11 leaks from the cracked portion, and the leaked cooling air passes through the fitting gap between the gate insert 1 and the lower mold 2 and enters the molten metal filled in the cavity 5a. There was a problem that a burrow or the like was generated after the molten metal was solidified.
[0005]
An object of the present invention is to provide a casting mold that does not generate burrows or the like after solidification of a molten metal by improving the sealing lid and eliminating the occurrence of early cracks in the welded portion of the sealing lid. It is in.
[0006]
[Means for Solving the Problems]
The present invention uses the following means in order to achieve the above object.
[0007]
That is, a casting mold having a cavity constituted by each mold, provided in a mold for cooling the molten metal filled in the cavity, and having an opening on the opposite surface of the cavity In having a groove and a sealing lid hermetically welded to the opening of the cooling groove,
The sealing lid is formed so as to protrude in a curved shape toward the inner side or the outer side of the cooling groove.
[0008]
According to the above means, the sealing lid that is airtightly welded to the cooling groove is formed so as to protrude in a curved shape inward or outward of the cooling groove. Even when stress is applied to the welded portion, the bending portion absorbs the stress and the stress applied to the welded portion is reduced, so that the occurrence of cracks in the welded portion of the sealing lid can be suppressed.
[0009]
Furthermore, the post-heating of the weld to remove the welding residual stress, which was necessary in the sealing lid welding process, becomes unnecessary because the welding residual stress is reduced by the stress absorption action of the curved portion of the sealing lid. Can be omitted.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1 to 5.
[0011]
In FIG. 1, reference numeral 1 is a spigot insert that forms a spout into which molten aluminum alloy is poured. A lower mold 2 is fitted and arranged on the outer periphery of the upper spigot 1, and an outer periphery above the lower mold 2. The horizontal mold 3 is fitted and disposed on the part, and the upper mold 4 is fitted on the top of the horizontal mold 3, and the mold part of the upper mold 4 is disposed on the inner side of the horizontal mold 3. The lower mold 2, the horizontal mold 3, and the upper mold 4 constitute a cavity 5a that forms a disk portion of a vehicle wheel and a cavity 5b that forms a rim portion.
[0012]
An annular cooling groove 11 is formed in the lower mold 2 at a position close to the outer periphery of the gate entrance 1 so as to surround the gate, and cooling air is caused to flow through the cooling groove 11 through a path described later. It is like that. The tip of the cooling groove 11 is arranged as close as possible to the cavity 5a side in order to increase the cooling effect. However, due to the strength problem against the thermal stress of the mold, the lower mold 2 in contact with the cavity 5a At least 10 mm away from the surface.
[0013]
As shown in FIG. 2, the annular cooling groove 11 provided in the lower mold 2 opens on the lower surface of the lower mold 2 in the direction opposite to the cavity 5a, and the opened annular opening 11a includes: An annular sealing lid 12a having a cross-sectional shape protruding inward from the cooling groove 11 and formed in a curved shape is hermetically welded. In the figure, B represents a weld (first embodiment).
[0014]
Reference numeral 13 denotes a cooling air inlet of the cooling groove 11, and 15 denotes a blower that sends the cooling air to the intake 13.
[0015]
In addition, as shown in FIG. 3, the opening 11 a of the cooling groove 11 has an annular sealing lid 12 b that has a cross-sectional shape that protrudes outward from the cooling groove 11 and is curved, contrary to the above. It may be air-tightly welded (second embodiment).
[0016]
In addition, the material of the lower mold | type 2 consists of alloy tool steel (SKD61) used normally, and the groove | channel width of 18 mm is used as the cooling groove 11 provided in the lower mold | type 2. As shown in FIG. The sealing lid for sealing the opening 11a of the cooling groove 11 is made of stainless steel (SUS304L) having a thickness of 4 mm, both of the conventional sealing lid 12c and the sealing lids 12a and 12b of the present invention. The curved part depth of 12b is 5 mm.
[0017]
By the way, as shown in FIG. 4, the cooling air flowing through the cooling groove 11 is introduced from the cooling air intake port 13 and discharged from the respective discharge ports 14 to the outside while flowing through the cooling groove 11 as indicated by arrows. It has become so. 6 in the figure is a bolt hole to which a vehicle wheel is attached.
[0018]
Next, the present invention product and the conventional product were compared in terms of the endurance life of the sealed lid welded part due to cold heat during casting.
[0019]
However, as shown in FIG. 5 (b), the cold heat at the time of casting is the temperature of the P part of the lower mold 2 near the upper part of the gate entrance 1 shown in FIG. Was performed on a casting mold varying from 480 ° C to 550 ° C.
[0020]
As a result, in the case of the conventional sealing lid 12c, cracks started to occur in the welded portion A (see FIG. 6) from about 55,000 cycles with respect to the target life of 20,000 cycles. In the case of No. 12b and No. 12b, it was found that cracks in the weld B did not occur until about 30,000 cycles, and the target life (depreciation life of the mold) was sufficiently satisfied.
[0021]
As described above, the durable life of the welded portion of the sealing lids 12a and 12b of the present invention is greatly improved because the sealing lids 12a and 12b are formed in a curved shape, so that the sealing lid 12a is cooled by the cold heat during casting. Alternatively, the stress applied to the welded portion 12b is absorbed by the curved portion and becomes small.
[0022]
By the way, in the case of the conventional sealing lid 12c, the welding to the cooling groove 11 requires four steps of preheating, argon welding, post-heating, and slow cooling, but in the case of the sealing lids 12a and 12b of the present invention, the cooling groove The welding of No. 11 may be performed in three steps of preheating, argon welding, and slow cooling, and an accompanying effect was obtained in that heating was not necessary after 1 hour at 400 ° C.
[0023]
The reason for this is that, in the case of the sealing lids 12a and 12b, the residual stress applied to the welded portion by argon welding is significantly smaller than that in the case of the conventional sealing lid 12c due to the stress absorbing action of the curved portion. It is believed that the post-heat needed to remove the welding residual stress is no longer needed.
[0024]
Next, in the present embodiment, the vehicle wheel was taken up as a cast part and the annular cooling groove was provided in the lower mold, but it was provided in the mold for cooling the molten metal filled in the cavity. If it is a casting mold having a cooling groove, it can be applied regardless of the type of casting part, the type of mold and the shape of the cooling groove.
[0025]
In the present embodiment, cooling air is used as a cooling medium flowing in the cooling groove. However, cooling water may be used instead of the cooling air if necessary, and in this case, a water pump is used instead of the blower. .
[0026]
【The invention's effect】
Since the casting mold of the present invention is configured as described above, the occurrence of cracks during the casting of the welded portion of the hermetic lid can be suppressed, and accordingly, casting defects such as burrows after solidification of the molten metal. Is prevented, and further, the post-heating of the welded portion of the sealing lid becomes unnecessary, so that the welding cost is reduced.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view showing an embodiment of a casting mold according to the present invention, and is a sectional view taken along line XX of FIG.
FIG. 2 is an enlarged view of a main part of the first embodiment.
FIG. 3 is an enlarged view of a main part of a second embodiment.
4 is a bottom view of the cooling groove in FIG. 1. FIG.
FIGS. 5A and 5B show changes in mold temperature during casting, where FIG. 5A is a view showing a temperature measuring portion of the mold, and FIG. 5B is a pattern diagram showing changes in mold temperature in one cycle of casting.
FIG. 6 is an enlarged view of a main part of a conventional casting mold.
[Explanation of symbols]
2 Lower mold 3 Horizontal mold 4 Upper mold 5a Cavity (disk part)
5b Cavity (rim part)
11 Cooling groove 11a Opening part 12a, 12b Sealing lid A, B Welding part

Claims (1)

A casting mold having a cavity constituted by each mold, provided in a mold for cooling the molten metal filled in the cavity, and a cooling groove having an opening on the opposite surface of the cavity; In what has a hermetic lid hermetically welded to the opening of the cooling groove,
A casting mold, wherein the sealing lid is formed so as to protrude in a curved shape toward the inner side or the outer side of the cooling groove.

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