JP2002178129A - Mold for casting - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the crack at early stage in a welded part of a mold for casting having a cooling groove for cooling molten metal filled in a cavity in the metallic mold and fixing a sealing cover for hermetically closing the opening part of this cooling groove to the metallic mold by welding. SOLUTION: The mold for casting having the cavities 5a constituted of each metallic mold, for cooling the molten metal filled in the cavities is provided with the cooling grooves 11 having the opening parts 11a on the surfaces at the opposite side of the cavities and the closing covers 12a air-tightly welded with the opening parts 11a of the cooling grooves 11. The sealing covers 12a are formed in a curved state by protruding inwardly or outwardly out of the cooling grooves 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a casting mold used for casting various parts.

[0002]

2. Description of the Related Art In a casting mold used for casting a vehicle wheel, a portion of a cavity near a gate is thicker than other portions, so that the molten metal filled in the cavity is efficiently cooled. There is a need.

For this reason, conventionally, as shown in FIG. 6, an annular cooling groove 11 is provided in a portion of a lower mold 2 surrounding a gate insert 1, and the annular cooling groove 11 opened on the opposite side of the cavity 5a. The opening 11a was air-tightly welded with a flat lid 12c, and cooled by flowing cooling air through the cooling groove 11.

[0004]

However, in the above-mentioned conventional structure, the closed lid 12c is not heated by the cold heat during casting.
The stress may be applied to the welded portion, and a crack may occur early especially at the welded portion A. In this case, the cooling air flowing through the cooling groove 11 leaks from the crack, and the leaked cooling air flows into the molten metal filled in the cavity 5a through the fitting gap between the gate insert 1 and the lower mold 2. There is a problem that burrows and the like occur after solidification of the molten metal.

[0005] An object of the present invention is to improve a sealing lid so that cracks do not occur early in the welded portion of the sealing lid. To provide.

[0006]

The present invention uses the following means to achieve the above object.

More specifically, a casting mold having a cavity formed by each mold is provided in a mold for cooling the molten metal filled in the cavity, and an opening is formed in a surface opposite to the cavity. And a sealing lid hermetically welded to the opening of the cooling groove, wherein the sealing lid is formed in a curved shape by projecting inward or outward of the cooling groove. And

[0008] According to the above means, the hermetic lid, which is hermetically welded to the cooling groove, is formed in a curved shape so as to protrude inward or outward of the cooling groove. Even if stress is applied to the welded portion, the curved 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 hermetic lid can be suppressed.

Further, the after-heating of the welded portion for removing the welding residual stress required in the sealing lid welding process is unnecessary because the welding residual stress is reduced by the stress absorbing action of the curved portion of the sealing lid. Post-heating can be omitted.

[0010]

FIG. 1 is a block diagram showing an embodiment of the present invention.
A description will be given based on FIGS.

In FIG. 1, reference numeral 1 denotes a gate insert for forming a gate into which a molten metal of an aluminum alloy is poured, and a lower mold 2 is fitted and arranged on an outer peripheral portion above the gate insert 1. The horizontal die 3 is fitted and arranged on the upper outer peripheral portion, and the upper die 4 is fitted on the upper part of the horizontal die 3, and the die portion of the upper die 4 is disposed inside the horizontal die 3. These lower mold 2, horizontal mold 3 and upper mold 4
Thus, a cavity 5a forming the disk portion of the vehicle wheel and a cavity 5b forming the rim portion are configured.

Lower die 2 located near the outer periphery of gate insert 1
An annular cooling groove 11 is formed so as to surround the gate, and cooling air is caused to flow through the cooling groove 11 through a path described later. The tip of the cooling groove 11 is arranged as close as possible to the cavity 5a in order to enhance the cooling effect. It is at least 10 mm away from the surface.

The annular cooling groove 11 provided in the lower mold 2 is
As shown in FIG. 2, an opening is formed in the lower surface of the lower mold 2 in a direction opposite to the cavity 5a.
An annular hermetic lid 12a having a transverse cross section protruding inward of the cooling groove 11 and having a curved shape is hermetically welded to 1a. In the figure, B indicates a welded portion (first embodiment).

Reference numeral 13 denotes a cooling air intake of the cooling groove 11, and 15 denotes a blower for sending cooling air to the intake 13.

As shown in FIG. 3, the opening 11a of the cooling groove 11 has a cross section of the cooling groove 1 opposite to the above.
An annular hermetic lid 12b protruding outward and curved in a curved shape may be hermetically welded (second embodiment).

The material of the lower die 2 is made of a commonly used alloy tool steel (SKD61), and the cooling groove 11 provided in the lower die 2 has a groove width of 18 mm. The sealing lid for sealing the opening 11a of the cooling groove 11 is a conventional sealing lid 12c and a sealing lid 12a of the present invention.
12b is 4mm thick stainless steel (SUS304)
L), and the closed lids 12a and 12b of the present invention have a curved portion having a depth of 5 mm.

Meanwhile, as shown in FIG. 4, the cooling air flowing through the cooling grooves 11 is introduced from the cooling air intake 13 and flows through the cooling grooves 11 as indicated by arrows, and from the respective discharge ports 14 to the outside. To be discharged to 6 in the figure is a bolt hole to which a vehicle wheel is attached.

Next, a comparison was made between the product of the present invention and the conventional product regarding the durable life of the hermetically sealed lid welded portion due to cold heat during casting.

However, as shown in FIG. 5 (b), the cooling heat during casting is such that in one cycle of casting for 6 minutes,
This was performed on a casting mold in which the temperature of the portion P of the lower mold 2 near the upper part of the gate insert 1 shown in FIG.

As a result, in the case of the conventional closed lid 12c,
Cracking began to occur in welded portion A (see FIG. 6) at about 50,000 cycles with respect to the target life of 20,000 cycles. No cracks occurred in the part B, and it was found that the target life (depreciation life of the mold) was sufficiently satisfied.

As described above, the durable life of the welded portions of the sealing lids 12a and 12b according to the present invention is greatly improved because the sealing lids 12a and 12b are formed in a curved shape, and thus, the cold heat during casting. This is because the stress applied to the welded portion of the sealing lid 12a or 12b is absorbed by the curved portion and becomes smaller.

In the case of the conventional sealing lid 12c, welding to the cooling groove 11 requires four steps of preheating, argon welding, post-heating and slow cooling.
In the case of 2b, welding of the cooling groove 11 is performed by preheating, argon welding,
Three steps of slow cooling are sufficient, and an additional effect that heat is not required after performing at 400 ° C. for 1 hour was obtained.

The reason is that the closed lids 12a and 12b
In the case of, due to the stress absorbing action of the curved portion, the residual stress added to the welded portion by argon welding is significantly smaller than that of the conventional closed lid 12c, and thus it is necessary to remove the weld residual stress. It is probable that the heat was no longer needed after that.

Next, in this embodiment, a vehicle wheel is taken up as a casting part and an annular cooling groove is provided in the lower mold. However, a mold for cooling the molten metal filled in the cavity is used. If it is a casting mold having a cooling groove provided, the present invention can be applied regardless of the type of the cast component, the type of the mold, and the shape of the cooling groove.

In this embodiment, the cooling air is used as the cooling medium flowing through the cooling groove. However, if necessary, cooling water may be used instead of the cooling air. In this case, a water pump is used instead of the blower. Is used.

[0026]

Since the casting mold of the present invention is constructed as described above, the occurrence of cracks at the time of casting of the welded portion of the hermetic lid can be suppressed. Since the occurrence of casting defects such as holes is prevented, and the post-heating of the welded portion of the hermetic lid is not required, the welding cost is reduced.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing an embodiment of a casting mold of 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.

FIG. 4 is a bottom view of a cooling groove in FIG. 1;

FIG. 5 is a graph showing a change in mold temperature during casting;
Is a diagram showing a temperature measuring part of the mold, and (b) is a pattern diagram of a mold temperature change 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 12a, 12b Sealing lid A, B Welded part

Claims (1)

[Claims] 1. A casting mold having a cavity formed by each mold, wherein the casting mold is provided in a mold for cooling a molten metal filled in the cavity, and an opening is formed in a surface opposite to the cavity. And a sealing lid hermetically welded to an opening of the cooling groove, wherein the sealing lid is formed in a curved shape so as to protrude inward or outward of the cooling groove. And casting mold.