JP2008055487A - Die-casting mold and casting method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a die-casting mold, which can effectively prevent gas and oxide film in a plunger sleeve from being entrained into a product and enable a high-quality product to be obtained, and a casting method. <P>SOLUTION: The die-casting mold is used such that molten metal is poured into the plunger sleeve and the molten metal is injected into the mold by a plunger. At least the lower edge of the pouring gate at the sleeve side of a runner communicating with a mold cavity is positioned below the level of the molten metal poured into the plunger sleeve and a gas vent is positioned above the level of the poured molten metal so as to form a section for discharging the gas from the plunger sleeve. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a mold method and a casting method that are effective in improving product quality in cold chamber die casting using a melt of a light alloy such as an aluminum alloy or a magnesium alloy.

A general casting method of cold chamber die casting will be described with reference to the schematic diagram shown in FIG.
In the die casting mold, the movable mold 10a is disposed so as to face the fixed mold 10b, and the mold can be clamped and opened with a tie bar or the like.
When the movable mold 10a moves forward with respect to the fixed mold 10b to be in a mold-clamping state, a cavity 10e that matches the product shape is formed.
A plunger sleeve 3 is provided on the fixed mold 10b side, and the plunger sleeve 3 and the cavity 10e communicate with each other by a runner 10c. In this specification, the cavity side of the runner 10c is called a runner gate. The side is referred to as a gate (sleeve side gate).
The molten metal is pumped up with a ladle 1 from a melting and holding furnace or the like in which an aluminum alloy, a magnesium alloy or the like is melted, and poured into the plunger sleeve 3 from a pouring port 3a.
The poured molten metal 2 flows into the plunger sleeve 3 to form a molten metal surface 2a, but a space 5 is formed above the molten metal surface 2a.

FIG. 5 shows an example of a conventional mold method in such a cold chamber die casting.
The cavity 110 and the plunger sleeve 3 are communicated with each other by a runner 109, and an overflow part 112 is generally formed at the tip of the cavity 110 in order to reduce gas entrainment and hot water wrinkles. is there.
A method using an air vent such as a chill vent block or a so-called vacuum die casting method for sucking and reducing the inside of the cavity together with or instead of the overflow portion 112 is also known.

However, in such a conventional mold method, when the plunger 4 moves forward and the plunger tip attached to the tip of the plunger closes the pouring port 3a, air is introduced into the inner space 5 of the plunger sleeve 3. As a result, the molten metal surface 2a undulates.
In this state, when the plunger injects the molten metal, a gas nest in which gas (air) is entrained in the product is likely to be generated, and light alloys such as aluminum alloys are likely to form an oxide film on the surface portion. If mixed into the product, it may cause water wrinkles and internal defects.

  In die casting, as shown in FIG. 6, the molten metal is filled in the cavity 10e, the product part is sufficiently pressurized immediately before solidification, and the feeder part 20 is formed in order to prevent sink marks. After that, the movable mold 10a is opened, and the mold is released together with the product by a projection such as a push pin.

  Therefore, in the conventional method, even if the inside of the cavity is sucked and depressurized by a vacuum device or the like, there is a limit in setting the thickness of the feeder, so that air or oxide in the plunger sleeve is caught in the product. It was difficult to prevent this.

Japanese Patent Laid-Open No. 2006-116598 is known as a method for preventing air entrainment in the plunger sleeve.
However, the technique disclosed in the publication is to pour pressure into the plunger sleeve from the bottom, and a dedicated pressure pouring device is required, which is not only inferior in versatility but also difficult to adjust the pressure.

JP 2006-116598 A

  An object of the present invention is to provide a die casting mold and a casting method that can effectively prevent a gas or an oxide film in a plunger sleeve from being caught in a product and obtain a high quality product.

A mold according to the present invention is a die-casting mold in which molten metal is poured into a plunger sleep and a molten metal is injected into the mold with a plunger, and the runner's sleeve side gate is connected to the mold cavity. It is arranged so that at least the lower end is positioned below the surface of the molten metal poured into the plunger sleeve, and the gas vent is located above the molten metal surface of the poured molten metal. A degassing portion is formed.
The lower end of the runner's sleeve side spout is placed below the surface of the molten metal that is poured into the plunger sleeve, which prevents the entrance of the oxide film on the surface of the melt unlike the conventional sprue above the surface. .
Therefore, ideally, the upper end of the runner's sleeve side spout communicating with the mold cavity should be positioned below the surface of the molten metal poured into the plunger sleeve.
In addition, because the gas vent of the vent is located above the surface of the molten metal in the plunger sleeve, the gas (air) in the plunger sleeve is discharged to the outside during injection, so the gas is entrained in the product. However, since a part of the molten metal flows into the gas vent, the movable mold opens, and it is desirable that the gas vent is disposed at the position where the hot water portion is to be released.

In addition, when forming the degassing part from a cavity part, it is also possible to connect with the degassing part from the inside of a plunger sleeve.
As the gas venting portion from the plunger sleeve, the gas venting device described in Japanese Patent No. 3508014 and Japanese Patent No. 370838 can be used, and an air vent such as a chill vent block may be used.
Further, the quality can be further improved by reducing the pressure by a suction pressure reducing device using a suction valve or the like connected to a vacuum device.
In this case, the suction valve is preferably arranged not only in the gas vent from the plunger sleeve but also in the gas vent from the cavity.
In that case, suction vacuum from both may be shared by a single vacuum device.

  In addition, the movable mold may be an integral type in which a cavity portion and a portion that forms a feeder part are integrally provided. However, if a split mold is used, the feeder part can be shared and the maintenance of the mold groove is facilitated.

As a casting method using the mold according to the present invention, using the mold according to claim 5, a process of pouring from the pouring port into the plunger sleeve, and when injecting the molten metal with the plunger There is a process of starting at low speed and switching to high speed, the plunger starts at low speed, and the plunger tip provided at the tip of the plunger passes through the pouring port and sucks inside the plunger sleeve until it switches to high speed It has the process of decompressing, It is characterized by the above-mentioned.
The timing for sucking and depressurizing air in the plunger sleeve that has become hermetically sealed between low speed and high speed switching depends on the size of the machine, casting conditions, etc., but is 0.3 to 0.6 seconds before high speed switching. preferable.

In the die casting mold according to the present invention, at least the lower end of the runner on the sleeve side of the runner communicating with the mold cavity is disposed below the level of the molten metal to be poured into the plunger sleeve. It effectively prevents the generated oxide film from being caught in the product.
In addition, by providing a gas vent from the plunger sleeve, it is possible to effectively prevent the generation of a gas nest due to the contribution of the gas in the plunger sleeve.

The die-casting mold is composed of a fixed mold 10b and a movable mold 10a. Examples of mold plans for the movable mold 10a are shown in FIGS.
FIG. 1 shows an example in which an overflow portion 12 is formed at the tip of a cavity 10e with respect to injection casting, and a gas vent groove 8a and a gas vent device 14 are provided in a portion that becomes a feeder portion 20, and FIG. The example which has arrange | positioned the degassing apparatus 14a previously is shown.
The gas vent groove 8a becomes a gas vent hole when the mold is clamped to the fixed mold.

1 and 2, the molten metal surface when the plunger sleeve 3 is poured is indicated by a two-dot chain line 2b. FIG. 1 shows that the lower end 6a of the sleeve side gate 6 of the runner 9a is lower than the height of the molten metal surface. In this case, the upper end 7 is on the surface of the molten metal. In this case, the dimension a is preferably within 15 mm in the cross-sectional view along the line AA.
When the dimension “a” exceeds 15 mm, the oxide film is easily involved.
FIG. 2 shows a case where the upper end 7 of the gate 6 is above the molten metal surface 2b as shown in the sectional view taken along the line B-B. In this case, the dimension b is preferably within 15 mm.
When the dimension b exceeds 15 mm, the supply resistance to the runner increases.
By adopting such a method, it is possible to prevent the oxide film formed on the molten metal surface from being caught in the product when the molten metal is injected into the cavity 10e via the runner 9a.

1 and 2 show an example in which the gas venting devices 14 and 14a are provided. However, if a suction pressure reducing device connected to a vacuum device or the like by providing a suction port 15 and a suction valve or the like is provided, generation of a gas nest can be further prevented. .
The movable die 10a may be an integrated type in which the cavity 10e portion and the feeder 20 portion are integrated, or a divided type divided by a dividing line d, for example.
When the split type is used, the gas vent portion in the plunger sleeve can be shared, and the gas vent portion can be easily maintained.

The example of the method shown in FIG. 3 is an example in which a gas venting device 13 described in Japanese Patent No. 370838 is provided at the tip of the cavity 10e and connected to a vacuum device and connected by gas venting grooves 11a and 11b communicating with the cavity. .
In this case, the gas vent groove 8a from the plunger sleeve may be communicated with the gas vent groove of the cavity 10e.
Also in this case, a division type using a division line d may be used.
In the present invention, various known gas venting devices can be used.

The example of the movable method which concerns on this invention is shown. An example of a method in which a gas venting device is provided also on the cavity side is shown. An example of a vacuum die casting method is shown. A schematic diagram of a cold chamber die casting is shown. An example of a conventional mold method is shown. The structural example of a feeder part is shown.

Explanation of symbols

3 Plunger sleeve 3a Pouring port 4 Plunger 4a Plunger tip 6 Pouring port 8a Degassing groove 9a Runner 10a Movable mold 10b Fixed mold 10e Cavity 14 Degassing device 15 Suction port 20 Hot water supply part

Claims (7)

A die casting mold that pours water into the plunger sleep and injects molten metal into the mold with the plunger,
It is arranged so that at least the lower end of the runner's sleeve side sprue communicating with the mold cavity is positioned below the molten metal surface poured into the plunger sleeve,
A mold characterized in that a gas vent is located above the surface of the poured molten metal, and a gas vent from the plunger sleeve is formed.   2. The mold according to claim 1, wherein the upper end of the runner's sleeve-side gate that communicates with the mold cavity is located below the level of the molten metal poured into the plunger sleeve. .   3. The gold according to claim 1, wherein the degassing port is located above a molten metal surface of the poured molten metal, and is disposed at a position that becomes a feeder part when the molten metal is injected into the cavity. Type.   The metal mold according to any one of claims 1 to 3, wherein a gas vent from the plunger sleeve and a gas vent from the cavity are communicated with each other.   The metal mold according to any one of claims 1 to 4, wherein a suction pressure reducing device is provided in a gas vent part from the plunger sleeve and / or a gas vent part from the cavity.   The mold according to any one of claims 1 to 5, wherein the cavity portion and the portion forming the feeder portion are divided. Using the mold according to claim 5,
Pouring from the pouring port into the plunger sleeve;
When injecting molten metal with a plunger, it has a process of starting at low speed and switching to high speed, the plunger starts at low speed, and the plunger tip provided at the tip of the plunger passes through the pouring port and switches at high speed A die-casting method, comprising: a step of sucking and reducing the pressure inside the plunger sleeve.

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