JP3197109B2 - Manufacturing method of alloy products - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an alloy product utilizing the property of the thixotropic state of a low melting point alloy such as a zinc alloy, an aluminum alloy, a copper alloy, a lead alloy, and a magnesium alloy. The alloy material is supplied to the cylinder where the screw is driven to rotate, and the screw is driven and transported while maintaining the alloy material at a temperature above the solidus temperature and below the liquidus temperature, and applies a shearing action to apply semi-solidification. The present invention relates to a method for producing an alloy product in which a thixotropic alloy is produced and injected into a mold to obtain an alloy product.

[0002]

2. Description of the Related Art When an alloy material is vigorously stirred in a solid-liquid coexistence state, formation of resinous crystals, that is, dendrites, is suppressed, and fine granular solids of broken degenerated resinous crystals coexist with a liquid. A thixotropic substance is obtained. When a thixotropic substance in such a solid-liquid coexisting state is formed and solidified in a short time, the shrinkage due to solidification is smaller than that of an alloy product obtained by a conventional die casting method which is completely dissolved at a high temperature, and a shrinkage cavity is formed. Thus, a molded product having a small number of crystal grains and having very fine crystal grains can be obtained. A specific method for producing an alloy product utilizing the properties of such a thixotropic substance has been proposed, for example, in Japanese Patent Publication Nos. 1-354341 and 2-15620. These publications show a production method using an injection molding machine or an extruder, which is composed of a temperature-controllable screw and a cylinder. In addition, an inert gas such as an argon gas can be sealed in the cylinder. Therefore, the screw can be rotated in the inert gas to sequentially feed the alloy material to the tip of the cylinder. At this time, the temperature of the alloy material rises due to shearing action due to frictional contact with the inner surface of the cylinder and the outer surface of the screw, or frictional contact between the alloy materials, heat applied from the outside of the cylinder, etc. In this state, the alloy product can be obtained by injecting into the mold from the tip of the cylinder.

[0003]

According to the conventional manufacturing method described above, the cylinder is in an airtight state and is filled with an inert gas, so that an advantage that oxidation of the alloy material does not occur is recognized. However, according to the above-mentioned conventional manufacturing method, the properties of the product may be reduced in some cases. That is, since the operation is performed in an argon gas atmosphere, the alloy material is semi-solidified in the argon gas, and rarely a trace amount of the argon gas may be mixed. Also, when injecting into the cavity of the mold, the air filling the cavity may become turbulent and get caught in the alloy material. When argon gas or air is mixed into the alloy material in this way, even if it is a minute amount, fine bubbles are included in the alloy molded product, and the mechanical properties such as elongation and tensile strength of the alloy product are reduced. Sometimes. Further, since expensive argon gas is used, there is a disadvantage that the production cost of the alloy product is increased. Therefore, an object of the present invention is to provide a method of manufacturing an alloy product that can obtain an alloy product with high mechanical quality at low cost. Specifically, the oxidation of the alloy material is prevented, and there is no bubble. It is an object of the present invention to provide a method for manufacturing an alloy product that can be manufactured at a low cost.

[0004]

In order to achieve the above object, the present invention is to supply a powdery or pelletized alloy material to a cylinder from a hopper, and to supply the alloy material at a temperature higher than the solidus temperature and lower than the liquidus temperature of the alloy material. The screw is driven in the rotating direction while holding the alloy to produce a semi-solid thixotropic alloy by applying a shearing action while transferring the alloy material, and then driven in the axial direction to inject into the forming mold to obtain an alloy product At this time, at least the inside of the hopper, the inside of the cylinder, and the cavity of the forming die are formed by the same vacuum source while maintaining the same vacuum pressure.

[0005]

The alloy material in the present invention includes, for example, low melting point alloys such as zinc alloy, aluminum alloy, copper alloy, lead alloy, and magnesium alloy. The size or particle size of these low melting point alloys is not particularly limited as long as they are capable of producing a semi-solid thixotropic alloy by applying a shearing action while driving and transferring the screw. Therefore, in the present invention, these low melting point alloys are prepared as powders or pellets.

[0006] The low melting point alloy thus prepared is supplied to a cylinder, and the screw is driven to transfer the alloy material in a state where the alloy material is maintained at a temperature higher than the solidus temperature and lower than the liquidus temperature. While applying a shearing action to make a semi-solid thixotropic alloy, then inject it into a mold to obtain an alloy product,
At this time, the inside of the hopper, the inside of the cylinder, the cavity of the mold, and the like are kept at the same vacuum pressure by the same vacuum source. By maintaining the vacuum pressure, oxidation of the alloy material is prevented, and harmful gas is prevented from being entrained in the alloy material. In order to maintain the inside of the cylinder and the cavity of the mold at a vacuum pressure, it is desirable to use a rotary vacuum pump, for example, a rotary vacuum pump. This is because the rotary vacuum pump has a large exhaust capacity and little vibration during operation. The ultimate vacuum of the rotary vacuum pump is 10 ^-3
It is about Torr. Therefore, when a rotary vacuum pump or the like is applied, the present invention is implemented at a vacuum pressure of 10 ⁻³ Torr or more. The lower the degree of vacuum when practicing the present invention, the more an alloy product excellent in chemical and mechanical properties can be obtained. However, as shown in the examples, good results are obtained at 50 Torr, and when the pressure is 10 ² Torr or less, chemical and mechanical properties are also reduced as compared with alloy products obtained by the conventional manufacturing method. Even better alloy products can be obtained.

According to the present invention, an alloy product can be obtained by using the above-mentioned alloy materials. Hereinafter, an example of obtaining a molded product of a magnesium alloy on behalf of these alloy materials will be described.

As shown in FIG. 1, the alloy manufacturing apparatus used in the embodiment of the present invention is generally composed of an injection molding machine 1, an alloy material supply device 20, and a mold 30. The injection molding machine 1 includes a single-axis or two-axis screw 2 as is well known. The screw 2 is rotationally driven by a driving device 3 including a reduction gear, an injection ram, and the like, and is also driven in the axial direction. The cylinder 4 in which the screw 2 is provided has a predetermined length, and at a position closer to the driving device 3 side from the center thereof,
A supply opening 8 to which the alloy material is supplied is provided.
An alloy material supply pipe 27 described later is connected to the supply opening 8.

On the outer periphery of the cylinder 4, temperature control devices 5, 5,... Composed of a resistance heater or an induction heater are provided over substantially the entire length thereof.
5 , the temperature inside the cylinder 4 can be controlled. A nozzle 6 connected to an injection hole 7 is provided at one end of the cylinder 4, and a stop valve 9 is interposed in the injection hole 7. The stop valve 9 prevents air from entering the cylinder 4 from the injection hole when sucking back. The mold 30 includes a fixed mold 31 and a movable mold 32 as is well known.
Are formed. And this sprue 33
Is connected to the cavity 34.

An alloy material supply device 20 includes a primary hopper 21 for adding an alloy material while maintaining a vacuum, and a secondary hopper 21 for controlling a supply amount of the alloy material, for example, a rotor
A secondary hopper 24, a screw conveyor 25 for transferring the material supplied from the secondary hopper 24, one end of the screw conveyor 25 and the other end of the cylinder
And a supply pipe 27 connected to the supply opening 8. The primary hopper 21 is a cover 2 that can be closed.
1 'is provided, and an open / close valve 22 is interposed in a supply pipe 29 provided below the supply pipe 1'. The lower end of the supply pipe 29 penetrates a ceiling wall of a vacuum box 40 described later and passes through the secondary hopper 24.
Facing upwards. The screw conveyor 25 is driven by a motor 26, the number of revolutions of which is controlled, and the supply amount of the alloy material is controlled.

In the illustrated embodiment, the secondary hopper 24, the screw conveyor 25 and a part of the injection molding machine 1 are housed in a vacuum box 40. The vacuum box 40 has an exhaust pipe 4
1 is connected, and a vacuum pump 42 is interposed in the exhaust pipe 41. Therefore, when driving the vacuum pump 42, the inside of the vacuum box body 40 ¹⁰ -3 ~10 2 Torr
Of vacuum. In order to evacuate the inside of the cylinder 4, the cylinder 4 is provided with an intake pipe 11 opened inside the vacuum box 40. The intake pipe 11
The groove of the screw 2 at the portion corresponding to the cylinder 4 provided with is slightly deeper than the groove at the other portion. The cavity 34 of the mold 30 and the vacuum box 40 are connected by a conduit 36, and a controllable check valve 35 is interposed in the conduit 36. The primary hopper 21 and the vacuum box 40 also
It is connected by a pipe 28, and an on-off valve 23 is interposed in the pipe 28.

As described above, the secondary hopper 24, the screw conveyor 25, the intake pipe 11 of the cylinder 4, and the like are housed in one common vacuum box 40, and the cavity 34 and the vacuum box 40 are connected to the pipe 36. Therefore, the inside of the secondary hopper 24, the inside of the cylinder 4, and the like can be set to the same vacuum pressure by evacuating the inside of one vacuum box 40. In addition, since it is housed in one vacuum box 40, only one vacuum pump is required, and a manufacturing apparatus can be obtained at low cost. Further, since the same pressure acts, the alloy material does not flow out or flow backward due to the pressure difference.

Next, an example of manufacturing a molded article from a magnesium alloy by the above manufacturing apparatus will be described. First, primary hopper 2
The first on-off valves 22, 23 are closed. The check valve 35 is also closed. Activate the vacuum pump 42 and set the vacuum box 40
Keeping the inside of the ¹⁰ -3 ^{to 10} 2 Torr of vacuum. 1
Since the next hopper 21 is pneumatically disconnected from the vacuum box 40, the lid 21 'is removed and the pellet-shaped magnesium alloy material is supplied. Next, the primary hopper 21 is closed with the lid 21 ', and the on-off valve 23 is opened. Then, the interior of the primary hopper 21 is also evacuated. The on / off valve 22 provided in the supply pipe 29 is opened to transfer the material in the primary hopper 21 to the secondary hopper 24. After transferring a predetermined amount, the primary hopper 21
The on-off valves 22 and 23 are closed to prepare for insertion of the next material.

Next, a screw conveyor 25 provided in the secondary hopper 24 is driven by a motor 26. Then, the amount of magnesium pellets appropriately controlled by the screw conveyor 25 is supplied to the supply pipe 27 and the cylinder opening 8.
Through the cylinder 4. Temperature control device 5,
5, the cylinder 4 is heated to a solidus temperature of 490 ° C. or higher in the case of a magnesium alloy AZ91, for example.
After heating, the solidus temperature of the magnesium alloy is 490 ° C or higher,
The liquidus temperature is controlled to be 605 ° C. or lower. The screw 2 is driven to rotate while the screw 2 is pushed out to the tip of the cylinder 4.

The magnesium alloy is maintained in a solid-liquid mixed state while being maintained at a temperature not lower than the solidus temperature and not higher than the liquidus temperature while being transferred to the distal end portion in the cylinder 4, and a gap between the screw 2 and the cylinder 4 is formed. Since it is filled and transported, it is vigorously mixed and stirred by frictional contact. As a result, the generation of dendrites in the magnesium alloy is prevented, and the magnesium alloy is transferred to the distal end in the cylinder 4 while maintaining the thixotropic state. Since the injection hole 7 is closed by the stop valve 9, the transferred thixotropic magnesium alloy is stored in the tip space 10 of the cylinder 4, and is gradually increased by the continuously fed magnesium alloy. The screw 2 retreats according to the increase amount.

Next, the nozzle 6 of the injection molding machine 1 is brought into close contact with the opening of the sprue 43 of the closed molds 31 and 32 so that the injection hole 7 and the sprue 43 are in communication. When the storage amount of the magnesium alloy reaches the required amount for forming the product, the check valve 35 is opened and the cavity 34 is evacuated. Next, the stop valve 9 is opened, and the driving device 3 is operated to push the screw 2 toward the distal end. As a result, the magnesium alloy passes through the injection hole 7, the stop valve 9 and the sprue 33 from the tip space 10 to the cavity 34 between the fixed mold 31 and the movable mold 32.
Injected into. The magnesium alloy injected into the mold 30 fills the cavities 34 and is cooled and solidified into the shape of the cavities 34 in a thixotropic state to form an alloy product. The movable mold 32 is opened to take out the alloy product. Hereinafter, the same operation is repeated to obtain an alloy product.

Example 1 [Alloy material] A commercially available magnesium alloy was used. The composition of the components is as shown in Table 1. Pellets having a melting point of 605 ° C. and an average particle size of 2.5 mm were used. [Thixotropic and Injection Molding] The magnesium alloy was injected into a mold using an injection molding machine as shown in FIG. 1 to obtain a rod-shaped product. .. At this time, the temperature of the cylinder 4 is set to 590 ° C.
The temperature was controlled so as to be within ± 5 ° C., and the vacuum box 40 was controlled at 50 Torr. The injection speed was a cylinder ram speed of 1 m / s. The tensile strength and elongation of the product obtained under the above conditions are indicated by a in FIG. For comparison, the tensile strength and elongation of the product obtained in the same manner by filling the vacuum box 40 with nitrogen gas are indicated by b in FIG.

As is evident from FIG. 2, the injection molding in a vacuum atmosphere improves the tensile strength and the mechanical properties of elongation. It is considered that the reason for the improvement was that the magnesium alloy was not oxidized by injection molding in a vacuum atmosphere, and that no gas was mixed into the semi-solid magnesium alloy. In particular, since the inside of the cavity 34 was also evacuated and the injection was performed, the injection speed was high, but the turbulence of the gas did not occur in the cavity 34, and therefore, it is considered that the gas was not involved in the injection.

[0019]

As described above, according to the present invention, a powdery or pelletized alloy material is supplied to a cylinder from a hopper, and a screw is held in a state where the alloy material is maintained at a temperature not lower than the solidus temperature and not higher than the liquidus temperature. When driven in the rotational direction to transfer the alloy material and apply a shearing action to produce a semi-solid thixotropic alloy, and then driven in the axial direction to inject into the mold, to obtain an alloy product at least with the inside of the hopper. , The inside of the cylinder and the cavity of the mold are formed by using the same vacuum source and maintaining the same vacuum pressure, so that oxidation is prevented from the stage of storing the powder or pellet-like alloy material in the hopper. Because the inside of the cavity is also evacuated, harmful gases due to turbulence may be entrained in the alloy material even when the injection speed is high, even when the injection speed is high. There, the hopper interior, since the cylinder internal like is kept in the same vacuum pressure, the alloy material due to the pressure difference
There are many effects unique to the present invention, such as no outflow or backflow . Further, according to the present invention, since at least the inside of the hopper, the inside of the cylinder and the cavity of the molding die are formed by maintaining the same vacuum pressure by the same vacuum source at the same vacuum pressure, in addition to the above effects, the present manufacturing method is provided. The manufacturing apparatus to be implemented is inexpensive, so that an effect that the alloy product can be manufactured at low cost is also obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically showing one example of an apparatus for manufacturing an alloy product provided for carrying out the present invention.

FIG. 2 is a diagram showing mechanical properties of an alloy product obtained by the present example and an alloy product obtained by a conventional manufacturing method.

[Explanation of symbols]

 2 Screw 4 Cylinder 5 Temperature Control Device 20 Alloy Material Supply Device 24 Secondary Hopper 30 Mold 34 Cavity

Continuation of the front page (56) References JP-A-4-99830 (JP, A) JP-A-1-313164 (JP, A) JP-A-4-187359 (JP, A) , A) French Patent Application Publication 2658745 (FR, A1) (58) Fields investigated (Int. Cl. ⁷ , DB name) C22C 1/02 B22D 18/06 B22D 27/00-27/20

Claims (1)

(57) [Claims] An alloy material in the form of powder or pellets is supplied from a hopper (24) to a cylinder (4), and the screw (2) is held in a state where the alloy material is maintained at a temperature higher than the solidus temperature and lower than the liquidus temperature. When the alloy material is transferred in the rotational direction to apply a shearing action while transferring the alloy material to produce a semi-solid thixotropic alloy, and then driven in the axial direction to inject into the molding die (30) to obtain an alloy product, at least The inside of the hopper (24), the inside of the cylinder (4), and the cavity (3
And 4) maintaining the same vacuum pressure by the same vacuum source to form the alloy product.