JPH0999355A - Die casting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high quality die casting product having little gas content. SOLUTION: In a first process, an initial stage filling ratio for pouring molten metal into a sleeve is made to 40-60% and the velocity of an injection plunger 7 is made to a No.1 velocity, by which the molten metal surface is not waved, and the injection of the molten metal is started to make the filling ratio in the sleeve (8) 75-85%. In a second process, the velocity of the injection plunger 7 is made to a No.2 velocity at higher than the No.1 velocity and the injection of the molten metal is executed and the wave is developed on the molten metal surface and also, the velocity of the injection plunger 7 is followed to the wave velocity to discharge the air in the sleeve 8 through a gate 12. Successively, in a third process, the velocity of the injection plunger 7 is made to a No.3 velocity at lower than the No.2 velocity. Finally, in a fourth process, just after the tip part of the molten metal passes through the gate 12, the velocity of the injection plunger is made to an No.4 velocity at the same as or higher than the No.3 velocity to inject and fill up the molten metal into the cavity 14 in the die.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a die casting method.

[0002]

2. Description of the Related Art FIG. 4 is a graph showing injection conditions of a conventional die-casting equipment, in which the horizontal axis represents the injection stroke (specifically, the plunger tip stroke) and the vertical axis represents the injection speed (specifically the plunger tip Speed), and 1.0
Injection is performed at two speeds, a low speed of ~ 1.5 m / s and a high speed of 1.8 to 2.0 m / s. The low speed region is the period during which the molten metal remains in the sleeve, and the high speed region is the period from when the tip of the molten metal reaches the cavity to when the filling is completed.

[0003]

FIGS. 5 (a) and 5 (b) are schematic diagrams for explaining the flow of molten metal in a conventional die-casting equipment. FIG. 5 (a) shows a low injection speed region, that is, molten metal in a sleeve. A certain state, and (b) shows a state where the injection speed is in a high speed region, that is, a state from the initial stage when the molten metal is filled into the cavity from the sleeve to the completion of the filling. In (a), the die casting equipment 100 includes an injection plunger 102 (sleeve 103, plunger tip 104) for injecting the molten metal 101, a gate 105, and a cavity 106 (see (b)) having the same shape as the die casting product. .

In (a), the injection speed is 1.0
In the case of up to 1.5 m / s, the upper surface of the molten metal 101 in the sleeve 103 is sharply undulated, and air in the vicinity is melted.
Fill the cavity 106 while being rolled in 1,
Casting defects such as pinholes may occur.
In (b), the molten metal 101 passes through the gate 103 from the sleeve 103 at an injection speed of 1.8 to 2.0 m / s.
At this time, the molten metal is scattered into the cavity 106, and the velocity of the molten metal 101 at the gate 105 is generally 30 to 50 m.
/ S is reached. After this, the molten metal 101 becomes the cavity 106.
When it is injected into the inside, it becomes a jet flow, so air in the cavity 106 may be entrained, and gas remains in the product,
Casting defects such as pinholes may occur and the quality may be significantly impaired. Therefore, the air in the sleeve 103, the air in the cavity 106, and the gas generated by the release agent in the cavity 106 cannot be exhausted from the mold to the outside, so that they remain in the product and the quality of the product cannot be improved. Further, if heat treatment is performed on such a product to improve the strength, the residual gas causes bulges called blister on the surface of the product, so that the heat treatment cannot be performed and the strength cannot be improved.

Therefore, an object of the present invention is to provide a die casting method for reducing the gas content of a cast product and improving the quality.

[0006]

In order to achieve the above object, the first aspect of the present invention is to set the initial filling rate in the sleeve to 40 to 60% for pouring the molten metal and setting the speed of the injection plunger to the molten metal. Start the injection as the first speed with no wavy surface, and the first step to make the filling rate in the sleeve 75-85%, and the injection plunger speed to the second speed higher than the first speed. The second step of discharging the air in the sleeve through the gate by causing the wave to be generated on the surface of the molten metal and causing the speed of the injection plunger to follow the speed of the wave, and then the injection plan. A third step in which the speed of the jar is a third speed lower than the second speed;
Then, immediately after the tip of the molten metal has passed through the gate, the fourth speed for injecting the molten metal into the mold cavity is filled with the fourth speed which is equal to or higher than the third speed of the injection plunger. And the process.

Thus, in the first step, the initial filling rate is 40% in combination with the first speed of the injection plunger.
If it is less than the above range, heat is taken by the sleeve, the temperature of the molten metal is lowered, and the flowability of the molten metal deteriorates. Also, the initial filling rate is 60%
If it exceeds, the filling rate in the sleeve exceeds 100% before the pouring port is closed, and the molten metal overflows from the pouring port. Furthermore, the filling rate cannot be set to 75 to 85% due to the next step.

In the second step, the injection plunger second
When the initial filling rate (the latter filling rate of the first step) is less than 75% in combination with the speed of, the wave on the surface of the molten metal does not reach the inner surface of the upper sleeve, and the air in the sleeve is discharged. I can't. In combination with the second speed of the injection plunger, when the initial filling rate is over 85%, the wave on the surface of the molten metal reaches the inner surface of the upper sleeve immediately, and the discharge of air cannot follow the progress of the wave. , It is impossible to bleed air more effectively and to bleed it effectively. Therefore, if the filling rate is 75 to 85%, a cast product with less gas entrainment can be obtained. Further, since the heat treatment can be performed without worrying about the occurrence of blisters, the quality and strength can be improved.

In the third step, unless the speed of the injection plunger is set to the third speed lower than the second speed, the molten metal becomes a jet flow when passing through the gate from the sleeve and entrains air. In the fourth step, when the speed of the injection plunger is set to the fourth speed lower than the third speed, the molten metal temperature is lowered in the cavity, which causes defective molten metal running. Therefore, by performing the above-described first to fourth steps, it is possible to obtain a high-quality die cast product with a small gas content. Here, the filling rate = (volume of molten metal / apparent volume of sleeve) × 100 (%). However, ・ The apparent volume of the sleeve changes depending on the stroke of the injection plunger.・ The amount of molten metal is constant as a premise. Therefore, the filling rate changes depending on the stroke of the injection plunger.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the accompanying drawings. The drawings should be viewed in the direction of reference numerals. FIG. 1 is an explanatory view of a die casting equipment according to the present invention. The die casting equipment 1 includes a fixed mold 2, a movable mold 3, and a fixed plate 4 for clamping the molds 2, 3.
The guide rods 5 and 5, the movable platen 6, the injection plunger 7 (sleeve 8, plunger tip 9) for injecting the molten metal, and the drive control unit 11 of the injection plunger 7. A gate 12, a runner 13, and a cavity 14 having the same shape as the die-cast product are formed between the molds 2 and 3. Reference numeral 15 is a mold matching surface, and 16 is a pouring port.

The drive control unit 11 outputs a speed signal V to the drive unit 18 based on the stroke detection unit 17 for detecting the stroke of the injection plunger 7, the drive unit 18, and the stroke amount signal S from the stroke detection unit 17. It is composed of a control unit 19 which controls the feeding. The control unit 19 is provided with a map of the relationship between the stroke and the speed of the injection plunger 7, receives the stroke amount signal S from the stroke detection unit 17, sends a speed signal V corresponding to this stroke amount to the drive unit 18, and drives the drive unit 18. Controls the speed of the injection plunger 7 connected to the section 18.

The operation of the die casting method described above will be described below. 2 (a) to 2 (e) are schematic diagrams for explaining the state of the molten metal during movement of the injection plunger according to the present invention, where (a) and (b) are the first step, and (c) is the second step. Process, (d) shows the third process, and (e) shows the fourth process.
The fixed plate for clamping the mold, the guide rod, and the movable plate are omitted.

In (a), first, the molten metal 21 is poured into the sleeve 8 through the pouring port 16 so that the initial filling rate of the molten metal 21 is 40 to 60%. The height of the molten metal at this time is A. From this state, the injection plunger 7 is moved at a first speed of 0.05 to 0.1 m / s.

If the first speed is less than 0.05 m / s, the shot cycle becomes long and the temperature of the molten metal 21 drops. If the first speed is higher than 0.1 m / s, the molten metal may wave, and air or oxides on the surface of the molten metal may be involved in the molten metal. In (b), the height of the molten metal 21 becomes B due to the movement of the injection plunger 7, and the filling rate of the molten metal 21 reaches 75 to 85%.

In (c), when the filling rate is 75 to 85%, the injection plunger 7 is set to a second speed of 0.1.
Move at ~ 0.25 m / s. The molten metal 21 in contact with the plunger tip 9 becomes a wave reaching the inner surface of the upper sleeve 8 and advances while pushing the air above the molten metal 21 toward the gate 12. The height C of the molten metal 21 on the side of the gate 12 immediately after the injection plunger 7 is swung at the second speed is:
There is an intermediate state between the height B in the first step and the height D in the third step described later, that is, the filling rate is in the intermediate state of 75 to 85% and 95 to 98%.

If the second speed is less than 0.1 m / s, it is not possible to generate a wave on the surface of the molten metal 21 reaching the inner surface of the upper sleeve 8, and further, the second speed is 0.25 m / s.
If it exceeds s, a high wave can be generated, but since the wave advances ahead of the plunger tip 9, the air inside the sleeve 8 cannot be evacuated.

In (d), the filling rate of the molten metal 21 is 98.
% Or more (the height of the molten metal is D), that is, immediately before or immediately after the molten metal 21 fills the sleeve 8, the speed of the injection plunger 7 is set to a third speed lower than the second speed. Which is 0.05 to 0.1 m / s. By reducing the speed of the injection plunger 7, the gate 1
The flow of the molten metal 21 in 2 is stabilized, and when the molten metal 21 is injected from the gate 12 into the cavity 14, it is not made into a jet flow, and air entrainment is suppressed.

When the third speed is less than 0.05 m / s,
Since the injection speed sharply decreases, the temperature of the molten metal lowers, the flowability of the molten metal deteriorates, and the molten metal 21 scatters into the cavity 14 to generate a molten metal ball. Then, this hot water ball is caught in the molten metal 21 and its quality is deteriorated. Third speed is 0.1m / s
If it is over, melt 2 from the gate 12 into the cavity 14
When 1 is ejected, it becomes a jet and entrains air.

In (e), immediately after the molten metal 21 has passed through the gate 12 and is injected into the cavity, the speed of the injection plunger 7 is equal to or higher than the third speed, ie, 0.05 to 0.05. 0.15 m / s. The fourth speed is 0.
If it is less than 05 m / s, the temperature of the molten metal in the cavity 14 will be lowered, and the molten metal will be poorly rotated, and the appearance quality will be deteriorated. If the fourth speed is higher than 0.15 m / s, the cavity 14
Turbulent flow occurs when the molten metal 21 is filled therein, air is entrained in the molten metal, gas defects occur, and the quality deteriorates.

[0020]

EXAMPLE The gas content, strength and hardness of the cast product obtained in Example 1 of the present invention and the results of Comparative Example 1 and Comparative Example 2 will be described based on Table 1. Example 1: Using a 500 ton die casting machine, AC
After melting and refining the ingot for 2B (Al-Cu-Si based aluminum alloy casting), it is transferred to a hand furnace of a die casting machine and cast. Heat treatment is T6 (500 ℃
× 4Hour + 220 ° C. × 4Hour). The casting conditions are as follows. Molten metal temperature 700 to 720 ° C Casting pressure 800 to 900 kg / cm ² Casting weight 1.2 kg Product Automotive master cylinder Injection conditions According to Fig. 3

FIG. 3 is a graph showing the relationship between the injection stroke and the injection speed of the injection plunger according to the first embodiment of the present invention. The horizontal axis shows the injection stroke and the vertical axis shows the injection speed. The upper part of the graph shows the position of the tip of the molten metal 21. The molten metal 21 first stays in the sleeve 8 and is pushed out by the plunger tip 9 to reach the gate 12 and the cavity 14.

In the first embodiment, the first speed (first speed) is 0.05 to 0.1 m while the tip of the molten metal 21 is in the sleeve 8.
When the injection stroke reaches S1, the second speed (second speed) is 0.1 to 0.25 m / s.
And When the injection stroke is S2 and the tip of the molten metal 21 reaches the gate 12, the third speed (third speed) is set to 0.05 to 0.1 m / s. Injection stroke is S3
When the tip of the molten metal 21 reaches the cavity 14, the fourth speed (4th speed) is set to 0.05 to 0.1 m / s, and the injection is completed with the entire stroke ST. Here, the 2nd speed range and the 4th speed range each have an acceleration section up to the aforementioned predetermined speed in the initial stage and a deceleration section from the aforementioned predetermined speed in the latter period. The injection pattern is not limited to this, and may be changed depending on the weight of the casting, the temperature of the molten metal, the casting material, and the like.

Comparative Example 1 A conventional die casting method (DC), AC2B (Al-Cu-Si based aluminum alloy casting) was used as the material, and no heat treatment was carried out. Comparative Example 2; Gravity die casting method (GDC), made of material A
C2B (Al-Cu-Si based aluminum alloy casting) is used, and the heat treatment is T6 (500 ° C. × 6 Hour + 200).
℃ × 6Hour).

[0024]

[Table 1]

Example 1: Casting gas amount is aluminum 1
It was 2 cc or less per 00 g, which was very small, and the tensile strength and hardness were also good.

Comparative Example 1: Casting product gas amount is aluminum 1
As a result of the tensile test, the tensile strength was about 2/3, and the proof stress and the elongation were about 1/2.

Comparative Example 2: Casting product gas amount is aluminum 1
It was 2 cc or less per 00 g, which was very small. As a result of the tensile test, the tensile strength, the proof stress, and the hardness were the same as in Example 1.

From the above results, Example 1 has a smaller amount of gas than the conventional die cast product (Comparative Example 1),
It has the same level as that of the GDC product, and also has high values of strength and hardness, and is equivalent to the GDC product.

[0029]

The present invention has the following effects due to the above configuration. In the die casting method according to claim 1, the initial filling rate in the sleeve is set to 40 to 60% for pouring the molten metal, and the speed of the injection plunger is set to a first speed at which the surface of the molten metal does not undulate and the injection of the molten metal is started. The sleeve filling rate is 75
~ 85% in the first step and the speed of the injection plunger is set to a second speed higher than the first speed to inject the molten metal to generate waves on the surface of the molten metal and to make an injection plan at the wave speed. A second step of discharging the air in the sleeve through the gate by following the speed of the jar, and then a third step of setting the speed of the injection plunger to a third speed lower than the second speed. Then, immediately after the tip of the molten metal passed through the gate, the speed of the injection plunger was adjusted to the third speed.
Since it comprises a fourth step of injecting and filling the molten metal into the mold cavity at a speed equal to or higher than the speed of, the temperature of the molten metal does not decrease in the first step, and the flowability of the molten metal deteriorates. The molten metal does not fill the inside of the sleeve before the pouring port is closed, and the molten metal does not overflow from the pouring port.

In the second step, the waves on the surface of the molten metal reach the inner surface of the upper sleeve, and the air in the sleeve can be discharged. The waves on the surface of the molten metal do not reach the inner surface of the upper sleeve immediately, and the air is discharged. The air can be deflated effectively by following the progress of the waves. Further, the heat treatment can be performed without worrying about the occurrence of blisters, and the strength can be improved. In the third step, the molten metal does not become a jet flow when passing through the gate from the sleeve, and does not involve air. In the fourth step, the temperature of the molten metal does not drop in the cavity, and there is no possibility of defective molten metal rotation.

Therefore, by carrying out the above-mentioned first to fourth steps, it is possible to obtain a high quality die cast product having a small gas content.

[Brief description of drawings]

FIG. 1 is an explanatory view of a die casting facility according to the present invention.

FIG. 2 is a schematic diagram illustrating a state of molten metal when the injection plunger according to the present invention is moved.

FIG. 3 is a graph showing the relationship between the injection stroke and the injection speed of the injection plunger according to the first embodiment of the present invention.

FIG. 4 is a graph showing injection conditions of conventional die casting equipment.

FIG. 5 is a schematic diagram illustrating the flow of molten metal in conventional die casting equipment.

[Explanation of symbols]

1 ... Die casting equipment, 2 ... Fixed mold (mold), 3 ... Movable mold (mold), 7 ... Injection plunger, 8 ... Sleeve,
12 ... Gate, 14 ... Cavity, 16 ... Pouring spout, 21
… Molten metal.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Osamu Ito 1-10 Shinshinayama, Sayama-shi, Saitama Prefecture Honda Engineering Co., Ltd. (72) Yudo Ataka 1-10-1 Shinsayama, Sayama, Saitama Within Honda Engineering Co., Ltd.

Claims (1)

[Claims] 1. In a die casting method for injecting the molten metal in a sleeve into a mold by an injection plunger to obtain a casting material, the initial filling rate in the sleeve is set to 40 to 60% for pouring the molten metal, and an injection plan A first step in which the speed of the jar is set to a first speed at which the surface of the molten metal is not rippling, the injection of the molten metal is started, and the filling rate in the sleeve is set to 75 to 85%;
The speed of the injection plunger is set to a second speed higher than the first speed to inject the molten metal to generate a wave on the surface of the molten metal, and the speed of the injection plunger is made to follow the speed of the wave. The second step of discharging the air in the sleeve through the gate, and then the third step of setting the speed of the injection plunger lower than the second speed.
And then immediately after the tip of the melt has passed through the gate, the speed of the injection plunger is set to a fourth speed equal to or higher than the third speed, Fourth injection and filling into the mold cavity
And a die casting method.