JP3029781B2 - Vacuum 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 used for aluminum or an aluminum alloy, and more particularly to a reduced pressure die casting method using a powder release agent.

[0002]

2. Description of the Related Art As a release agent used in die casting, a water-soluble release agent obtained by emulsifying mineral oil, fat, wax, synthetic oil or the like in water using a surfactant has been used. However, in recent years, boron nitride, mica, metal oxides,
A technique using a powder release agent comprising an inorganic solid lubricant such as silicon nitride and an organic compound such as metal soap or a polymer compound has been developed. For example, Japanese Patent Publication No. 6-9730 discloses various types of powder release agents for die casting, and Japanese Die Casting Conference JD92-03p.
In p23-26, the weight percentage of the polymer compound is 5, 10 to 10.
20 and 50% powder release agents are disclosed. Regarding the die surface temperature in die casting using a powder release agent, the above-mentioned JD92-05pp37-4.
No. 1 discloses that it is preferable not to exceed 200 ° C. Furthermore, the above-mentioned collection of articles JD94-33pp283-29
For 2, a powder release agent was used and the injection pressure was 17.5 MPa.
Is disclosed.

[0003]

However, in the above-mentioned prior art, the content of the polymer compound in the powder release agent, the mold temperature on the cavity surface, or the injection pressure of the molten metal are individually determined. It only teaches casting conditions, and there is no way to think about optimization as to how to set these conditions as a whole. Therefore, an object of the present invention is to provide a casting method capable of obtaining a good casting in a reduced-pressure die casting method used for aluminum or an aluminum alloy.

[0004]

SUMMARY OF THE INVENTION The present invention has been made to achieve the above object. That is, a cavity is formed by a fixed mold and a movable mold, and the pressure in the cavity is reduced. Supplying a powder release agent comprising an inorganic solid lubricant and an organic compound to the mold surface of the depressurized cavity and applying it to the mold surface, and further injecting a molten aluminum or aluminum alloy into the cavity. In the reduced pressure die casting method for solidifying, the content of the organic compound of the powder release agent is 0.1% or more and 50% or less, the mold temperature on the surface of the cavity is 270 ° C or less, and A reduced pressure die casting method, wherein the injection pressure of the molten metal is 20 MPa or less.

[0005]

The reasons for limiting the manufacturing conditions of the present invention are as follows. Powder release agents include inorganic solid lubricants such as boron nitride, mica, metal oxides, silicon nitride, and metal soaps (sodium, calcium, barium, lithium, potassium, magnesium, or zinc in the carboxylic acid skeleton), polymers Compounded with an organic compound comprising a compound (polyethylene, polypropylene, epoxy resin, alkyd resin, or polystyrene). In this mixing ratio, the content ratio of the organic compound is set to 50% or less. This is because after the powder release agent is applied to the mold surface, the organic compound reacts with the heat of the molten metal when it comes into contact with the molten metal such as aluminum, burns out and gasifies, and mixes into the molten metal. This is because it becomes a blowhole. Further, when an organic compound is not contained in the powder release agent, the inorganic solid lubricant cannot be adhered to the mold surface. Therefore, it is necessary to contain 0.1% or more. The inorganic solid lubricant other than the above-mentioned organic compound does not react even when it comes into contact with the molten metal, exists on the surface of the mold, reduces the thermal conductivity between the molten metal and the mold, and acts as a heat insulating agent. Prevents a drop in hot water temperature. Therefore, since the temperature of the molten metal in the cavity is maintained at a high temperature, the molten metal can spread to a thinner portion than in the conventional case, so that a thinner product can be obtained as compared with the conventional die casting method.

[0006] Further, the fact that the decrease in the temperature of the hot water is small means that
Since injection can be performed at a lower temperature than in the past, the mold material to be used can be a low-grade material, and when a conventional high-grade material is used for the mold, the usable time is extended. Further, the mold surface temperature is set to 270 ° C. or lower because the organic compound in the powder release agent is dissolved. Also, by reducing the pressure in the cavity, the molten metal can be easily filled, and the flow of the molten metal can be improved by using the powder release agent as described above. Therefore, the injection pressure may be 20 MPa or less. However, the casting machine itself can be reduced in size, and the casting machine itself can be downsized.

[0007]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. FIG. 1 shows an example of a casting apparatus to which the method of the present invention is applied. This casting apparatus has a fixed mold 1 and a movable mold 2,
2 forms a cavity 3. A sleeve 4 is connected to the fixed mold 1, and a plunger tip 5 that is slid by a pressing device (not shown) is provided inside the sleeve 4. An electromagnetic pump 6 for supplying molten aluminum alloy is connected to the lower surface of the sleeve 4, and an electrostatic nozzle 7 is attached to the upper surface of the sleeve 4. The tank 8 is filled with a powder release agent 9, and the powder release agent 9 in the tank 8 is fluidized by flowing air 10. As the powder release agent 9, talc,
It is composed of 80 to 90% of boron nitride, mica and graphite inorganic solid lubricant and 10 to 20% of a high molecular compound.

A constant flow rate discharger 11 is connected to the tank 8, and discharge air 12 is discharged to the constant flow rate discharger 11 so that the powder release agent 9 is transferred from the electrostatic nozzle 7 through the sleeve 4 to the cabinet 8. It is configured to discharge to the tee 3. The electrostatic nozzle 7 is connected to the negative electrode of the high voltage generator 13, and the positive electrode of the high voltage generator 13 is connected to the fixed mold 1, and thus the powder release agent discharged from the electrostatic nozzle 7 9 is applied to the surface of the cavity 3 by an electrostatic coating method. The cavity 3 is a vacuum shut-off valve 1
4 is connected to a vacuum tank 15, which is depressurized by a vacuum pump 16.

Next, a die casting method using the above-described casting apparatus will be described. First, the movable mold 2 is advanced, and the movable mold 2 is brought into close contact with the fixed mold 1 to form a cavity 3. By slightly moving forward, the hot water supply port from the electromagnetic pump 6 is closed as shown in FIG. 1, the vacuum shut-off valve 14 is opened, and the inside of the cavity 3 is evacuated by the vacuum tank 15. After the degree of vacuum in the cavity 3 has increased to a certain degree, the vacuum shutoff valve 14 is closed and the constant flow rate discharger 1
By operating 1, the powder release agent 9 is discharged into the cavity 3 by the discharge gas 12 through the sleeve 4. Thus, the powder release agent is applied to the inner surface of the sleeve 4 and the mold surface of the cavity 3. Next, the plunger tip 5 is retracted, a molten aluminum alloy is poured into the sleeve 4 by the electromagnetic pump 6, and the plunger tip 5 is advanced to inject the molten metal in the sleeve 4 into the cavity 3.
At this time, the molds 1 and 2 are locally cooled as necessary so that the surface temperature of the molds becomes 270 ° C. or less. The injection pressure is set to 20 MPa or less. After the melt of the aluminum alloy poured into the cavity 3 is solidified, the movable mold 2 is retracted to take out a casting, and one casting cycle is completed.

As described above, in this embodiment, since the powder release agent having a content of the high molecular compound of 50% or less is used,
More than 50% of the inorganic solid lubricant adheres to the surface of the cavity 3 without burning, and acts as a heat insulating material to prevent the temperature of the hot water from lowering. Therefore, since a lower-temperature molten metal can be poured, a high-temperature resistant material is not required, and the number of shots in the same molds 1 and 2 can be increased. Further, since the mold temperature on the surface of the cavity is 270 ° C. or less, the life of the mold is extended, and the defects of the metal structure are reduced. Further, since the injection pressure of the molten metal is 20 MPa or less, the size of the casting apparatus can be reduced.

[0011]

As described above, according to the method of the present invention, the depressurizing die-casting method uses a powder release agent having an organic compound content of 50% or less and reduces the mold temperature on the cavity surface to 2%.
70 ° C or less, and injection pressure of the molten metal mold is 20 MPa
From the following, it is possible to cast a high-quality die-cast product using a small and inexpensive casting apparatus.

[Brief description of the drawings]

FIG. 1 is a system diagram showing an example of a casting apparatus to which the method of the present invention is applied.

[Explanation of symbols]

1 ... fixed mold 2 ... movable mold 3
… Cavity 4… Sleeve 5… Plunger tip 6
... Electromagnetic pump 7 ... Electrostatic nozzle 8 ... Tank 9
... powder release agent 10 ... flowing air 11 ... constant flow rate discharger 1
2 ... Discharge air 13 ... High voltage generator 14 ... Vacuum shut-off valve 1
5 ... Vacuum tank 16 ... Vacuum pump

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-3-243242 (JP, A) JP-A-6-322493 (JP, A) JP-A-63-220962 (JP, A) JP-A-49-49 1427 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) B22D 17/14 B22D 17/20 B22D 17/22 B22D 17/32

Claims (1)

(57) [Claims] 1. A forming a cavity by a fixed mold and a movable mold and vacuum the cavity, an inorganic solid lubricant and an organic compound on the mold surface of the vacuum was <br/> cavity A powder release agent is supplied and applied to the mold surface,
In addition, aluminum or aluminum alloy is placed in the cavity.
In a vacuum die casting method for injecting and solidifying a molten metal, the content of the organic compound in the powder release agent is 0.1% or more.
Or less 0%, the mold temperature at the surface of the cavity is at 270 ° C. or less, and vacuum die casting method, wherein the injection pressure of the molten metal is not more than 20 MPa.