JP2003340559A - Die casting method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a die casting method without entrapping air at die casting. <P>SOLUTION: The die casting method comprises a molten metal supply process for supplying molten metal inside a sleeve and an injection process for extruding the molten metal inside the sleeve by a plunger tip slidably fitted inside the sleeve and injecting the same inside a mold cavity. In the method, the molten metal supply speed is high in the first half of the molten metal supply process, and the speed is low in the latter half thereof. More specifically, in the first half of the molten metal supply process, 40-70% of the total supply quantity of the molten metal is preferably supplied at an average molten metal supply speed of the first half equal to 110-200% of an average molten metal supply speed of all the molten metal and in the latter half of the molten metal supply process, 60-30% of the total quantity of the molten metal is preferably supplied at a latter half average molten metal supply speed of 90-50% of the average molten metal supply speed of all the molten metal. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a die casting method. More specifically, the present invention relates to a die casting method for controlling the molten metal supply rate in order to prevent air from being entrained in the molten metal.

[0002]

2. Description of the Related Art The die-casting method is a method suitable for mass production because it produces high-quality and precise products for automobile members and parts. However, since air is entrained when the molten metal is injected into the cavity, defects such as blowholes and blowholes may occur, which greatly affects the weldability and heat treatment of die-cast products thereafter. There is.

Since the die casting method is a manufacturing method suitable for mass production of parts and members, improvement of productivity, especially shortening of cycle time is always an important technical subject.

In the one-shot cycle of the die casting method, the molten metal is supplied to the sleeve. The chip is moved to inject the molten metal into the cavity. Open the mold and return the chip that takes out the die cast product to its original position. Close the mold. It can be considered that one cycle consists of 5 steps.
Therefore, the cycle time can be shortened by shortening the hot water supply time and the molten metal injection time. here,
In order to shorten the hot water supply time, the hot water supply speed must be increased. If the rate of hot water supply is increased with the amount of hot water supplied being constant, the flow of the molten metal in the sleeve will naturally become violent, and the amount of air entrained in the molten metal will also increase. In addition, in order to shorten the molten metal injection time, it is sufficient to increase the moving speed of the plunger tip, but this has an optimum pattern for quality and cannot be increased unnecessarily, so the cycle time is shortened. The issue is how to shorten the hot water supply time so as not to deteriorate the quality of die cast products.

[0005]

In the die casting method, the behavior of the molten metal when the molten metal is fed to the sleeve in the hot water feeding step will be described with reference to a), b) and c) of FIG.

FIG. 1A is an explanatory view showing a state in which the molten metal 3 is being supplied to the sleeve 4. The molten metal 3 is supplied from the ladle 5 through the hot water supply port 2 into the sleeve 4. The hot water supply speed at this time is constant. In such a conventional method, the molten metal 3 flows with a vigorous force in the direction of the arrow X along with the hot water supply, so that the molten metal 3 is biased toward the cavity 10 side (not shown), and the rise of the molten metal 3 until the completion of the hot water supply is stepped. Will be maintained.

FIG. 3B shows a state in which the tip 6 starts pressing the molten metal at the same time when the hot water supply is completed. Since the tip presses the molten metal 3 in the direction of the arrow Y almost at the end of the hot water supply, the step wave 11 generated in a) is not eliminated as shown in b) but rather emphasized. When the tip 6 further presses the molten metal 3 in this state, the air 12 is trapped between the inner wall of the sleeve 4 and the molten metal 3 as shown in c), and the air 12 is finally entrained in the molten metal to form a cavity. 10
Are filled in the product and become blowholes (gas defects) in the product. An object of the present invention is to provide a die casting method that does not generate this blow hole.

[0008]

A die casting method according to the present invention comprises a step of supplying molten metal into a sleeve and a die in which a molten metal in the sleeve is extruded by a plunger tip slidably fitted in the sleeve. The injection method of injecting into the cavity is characterized in that the hot water supply speed is fast in the first half of the hot water supply process and slow in the second half of the hot water supply process.

More specifically, in the first half of the hot water supply process, 40 to 70% of the total amount of hot water is supplied so that the value of the first half average hot water supply rate is 110 to 200% of the total average hot water supply rate. In the latter half of the hot water supply process, 60 to 30% of the total hot water supply amount is 90 to 30% of the total average hot water supply speed.
It is desirable to supply hot water so that it becomes 50%.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 2 schematically shows a die casting apparatus to which the die casting method of the present invention can be applied. The die casting device includes a cavity 10 formed by a fixed mold 8 and a movable mold 9, and a sleeve 4 communicating with the cavity 10.
A plunger tip 6 slidably fitted in the sleeve 4 and an injection device 7 for driving the plunger tip 6.
And a ladle 5 for supplying the molten metal 3 into the sleeve 4. In the vicinity of the end of the sleeve 4 on the side opposite to the side communicating with the cavity 10, a hot water supply port 2 through which the molten metal 3 can be supplied into the sleeve 4 by a ladle 5 is opened.

A die casting method according to the present invention in such a die casting apparatus will be described with reference to a), b) and c) of FIG.

FIG. 3A is an explanatory view showing the first half of the hot water supply process. In the first half of the hot water supply step, since the ladle 5 is tilted to supply the hot water at a speed higher than the total average hot water supply speed, the molten metal 3 violently flows in the direction of the arrow X. As a result, the molten metal 3 is biased toward the cavity 10 side and rises up.

However, in the latter half of the hot water supply step as in b), the hot water supply speed is made slower than the total average hot water supply speed, so the momentum of the molten metal 3 in the direction of the cavity as indicated by arrow Y weakens, and the molten metal on the cavity 10 side is weakened. The unevenness of 3 is gradually released, the local rise of the molten metal disappears, and the step wave is eliminated.

Therefore, since the molten metal 3 is not disturbed in the sleeve 4, as the plunger tip 6 moves as shown in c), air is sequentially pushed by the molten metal 3 and the cavity 10 is moved.
Since the molten metal 3 is discharged from the side and then the molten metal 3 is injected into the cavity 10, no air is entrained in the product. As a result, it is possible to suppress the occurrence of quality defects called blow holes in die-cast products. This also means that the cycle time can be shortened without degrading the quality of the die cast product.

An embodiment of the die casting method of the present invention is as follows.

That is, in the first half of the hot water supply process, the total amount of hot water supplied is 4
The value of the first half average hot water supply rate of the molten metal of 0 to 70% is 110 to 200% with respect to the total average hot water supply speed, and 60 to 30% of the total hot water supply amount is against the total average hot water supply speed in the latter half of the hot water supply process. It is preferable to supply hot water so that the value of the latter half average hot water supply speed is 90 to 50%. When the average hot water supply speed in the latter half is 90% or more of the total average hot water supply speed, the effect of lowering the hot water supply speed is hardly obtained. Also, if it is slower than 50%,
The momentum of the molten metal flow in the cavity direction due to the hot water supply becomes too weak, and the unevenness of the molten metal on the cavity side is released all at once and a step wave is generated. This is not suitable because it causes air entrapment (gas defects or blowholes) in the die cast product.

The hot water supply method is not particularly limited as long as it can control the hot water supply speed, but the method of controlling the tilting speed of the ladle is desirable. It is also preferable to use a ladle having a shape in which the hot water supply speed changes even if the tilting speed is constant. Further, a method of controlling the flow rate of the molten metal above and below the rod by a stopper ladle method is also suitable.

The die casting method of the present invention can be applied to the horizontal sleeve die casting apparatus shown in FIG.
Here, the average hot water supply rate is 1.5 to 3.0 kg / sec.
Is preferred. Average hot water supply rate is 3.0 kg / s
If it exceeds ec, the hot water supply speed in the first half becomes too high, and if the average hot water supply speed is less than 1.5 kg / sec, the step wave is not originally generated even if hot water is supplied at a constant speed from beginning to end, so it is not necessary to apply the method of the present invention. .

[0019]

EXAMPLES The present invention will be described in more detail by way of examples. The present invention is not limited to these examples. (Production of Apparatus and Test Piece) The die casting apparatus used in this example is the die casting apparatus shown in FIG. 2, and the mold clamping force is 800 t. 4 kg of 690 ℃ molten aluminum
Was heated by the ladle 5 from the hot water supply port 2 to the injection sleeve 4 preheated to 250 ° C. Here, the tilting speed of the ladle 5 was controlled so that the hot water supply speed of the hot water supply pattern set in advance was set.

Injection is started at the same time when the hot water supply is completed. 0.2m until the stroke of tip 6 reaches 400mm
/ Sec to press the melt, and then accelerate to 2.5 m / sec up to the position of 550 mm, and fill the cavity 10 composed of the fixed mold 8 and the movable mold 9 where the melt 3 is preheated to 250 ° C. A test piece 1 was obtained. The casting pressure at this time is 4
It was 0 MPa. The test piece 1 has a thickness of 2.5 m.
It was a plate-like test piece of 450 mm × 500 mm in m.

In the hot water supply pattern, the total hot water supply time is set to 2 seconds, the second half hot water supply speed is changed in the range of 0.5 to 2.0 kg / sec, and the corresponding first half hot water supply speed is obtained to obtain 10 levels of hot water supply pattern. A test piece 1 was produced.

An example of a hot water supply pattern is shown in FIG. The horizontal axis of FIG. 3 is the hot water supply time T (seconds), and the vertical axis is the hot water supply speed R (kg /
sec). Since the present embodiment is a cycle in which 4 kg of molten metal is supplied in 2 seconds, the total average hot water supply rate is the broken line C.
2 kg / sec. The pattern A shown by the solid line is
This is the case where the hot water supply rate in the latter half of 1.5 seconds is 0.5 kg / sec. Therefore, in the first half of this case, 3.25 kg (81% of the total hot water supply amount) of molten metal must be supplied in 0.5 seconds, so the average hot water supply rate in the first half is 6.5 kg / s.
ec, which is 32 of the total average hot water supply rate (2 kg / sec)
Since it is 5%, it is a comparative example outside the scope of the present invention. Further, the pattern B shown by the dotted line has a hot water supply speed of 1.
The case is 0 kg / sec. Since the second half is hot water supply for 1.25 seconds, the first half is 2.75 kg in 0.75 seconds
(69% of total hot water supply) will be supplied. That is, the average hot water supply rate in the first half is 3.7 kg / sec, which is 185% of the total average hot water supply rate (2.0 kg / sec). It is a preferable test example of the present invention. (Evaluation Results) A transmission X-ray test was performed on the test pieces obtained in each hot water supply pattern to observe internal defects. Air entrainment was evaluated by the sum of the area of defects found.
The results are shown in Fig. 4. In FIG. 4, the horizontal axis represents the average hot water supply rate Ra in the latter half of the hot water supply process in kg / sec, and the vertical axis represents 45.
The total area A of defects within 0 mm × 500 mm is shown in mm ² . Here, data having the same average hot water supply speed but different defect areas represents repetition. For example, the three points with the latter half average hot water supply rate of 2.0 kg / sec are the respective results obtained by producing three test pieces in the same pattern. That is, it can be seen that, until the latter half average hot water supply rate is 1.0 kg / sec, the defect area decreases with a decrease in the average hot water supply rate, and the quality is improved. However, the average hot water supply speed in the latter half was 1.
It was found that when the pressure was further reduced below 0 kg / sec, the momentum of the flow of the molten metal toward the cavity became too weak, and the unevenness of the molten metal was released all at once, resulting in step waves and rather deterioration of the quality. That is, for the average hot water supply rate of 2.0 kg / sec, the average hot water supply rate of the latter half is 50 kg.
If it is less than%, the quality of the die cast product deteriorates.

[0023]

According to the die casting method of the present invention, it is possible to prevent the entrainment of air in the sleeve at the time of injecting the molten metal, so that the quality deterioration of the die cast product due to the entrainment of air can be reduced. Further, the cycle time of die casting can be shortened and the productivity can be improved without deteriorating the quality of the die cast product.

[Brief description of drawings]

FIG. 1 is an explanatory view showing a hot water supply process of the present invention. a) is the first half of the hot water supply process, in which hot water is supplied at a speed faster than the total average hot water supply speed. The flow of molten metal due to hot water supply is intense, and the molten metal is biased toward the cavity side. In b), the latter half of the hot water supply process, hot water is supplied at a speed slower than the total average hot water supply speed.
The flow of the molten metal due to the hot water supply is gentle, and the bias of the molten metal toward the cavity is eliminated. c) shows the injection state of the molten metal. Since the molten metal is not disturbed, step waves are not generated and the injected molten metal does not entrain air.

FIG. 2 is a schematic diagram showing an outline of a die casting device.

FIG. 3 is a diagram showing an example of a hot water supply pattern of the present invention.

FIG. 4 is a diagram showing the relationship between the latter half average hot water supply rate and the defect area of a test piece of the present invention.

FIG. 5 is an explanatory view showing a conventional hot water supply process. The hot water supply rate is constant. In a), hot water is being supplied, and the molten metal is biased toward the cavity side. b) shows the state immediately after the start of the molten metal injection, and a step wave is recognized. c) shows how the molten metal is filled into the cavity. The molten metal in the injection sleeve traps air and is injected into the cavity.

[Explanation of symbols]

1: Test piece 2: Hot water inlet 3: Molten metal 4: Sleeve
5: Ladle 6: Chip 8: Fixed mold 9: Movable mold 10: Cavity 1
1: Step wave 12: Trapped air

Claims (3)

[Claims] 1. A hot water supply step of supplying molten metal into a sleeve,
A die-casting method comprising: an injection step of extruding the molten metal in the sleeve by a plunger tip slidably fitted in the sleeve and injecting the molten metal into the cavity of a mold. In the first half of the hot water supply process,
A die-casting method characterized in that it is delayed in the latter half of the hot water supply step. 2. In the first half of the hot water supply step, the total hot water supply amount is 40 to
The value of the first half average hot water supply rate of the molten metal of 70% is 110 to 200% with respect to the total average hot water supply speed, and in the latter half of the hot water supply step, 60 to 30% of the total hot water supply amount is the latter half of the total average hot water supply speed. The average hot water supply speed value is 9
The die-casting method according to claim 1, which is 0 to 50%. 3. The die casting method according to claim 2, wherein the hot water supply speed is controlled by a tilting speed of a ladle.