CN112775407A

CN112775407A - Vacuum die casting method and die for vacuum die casting

Info

Publication number: CN112775407A
Application number: CN202010141593.9A
Authority: CN
Inventors: 郑秉准; 李知容; 李喆雄; 金亿寿; 朴镇营; 尹必焕
Original assignee: Hyundai Motor Co; Kia Motors Corp
Current assignee: Hyundai Motor Co; Kia Corp
Priority date: 2019-11-05
Filing date: 2020-03-03
Publication date: 2021-05-11
Also published as: DE102020104234B4; US20210129213A1; KR20210054328A; DE102020104234A1

Abstract

The present invention relates to a vacuum die casting method. The vacuum die casting method may include the steps of: coupling the fixed mold and the movable mold to each other; closing a molten metal pouring hole formed on a sleeve formed on a lower side of a fixed mold or a movable mold by an injection plunger operating in the sleeve; vacuum-decompressing a cavity formed between a fixed mold and a movable mold by a vacuum decompression device connected to a chilled exhaust block provided at upper portions of the fixed mold and the movable mold; supplying oxygen to the cavity through an oxygen supply device connected to the quench exhaust block after the step of performing vacuum decompression is completed; and supplying molten metal to the cavity through the molten metal pouring hole.

Description

Vacuum die casting method and die for vacuum die casting

Technical Field

The present disclosure relates to a die casting method and a die, and more particularly, to a die casting method and a die by generating a vacuum in a cavity of the die.

Background

Generally, high-pressure casting (die casting) can be performed in the following manner: molten metal of light non-ferrous metal alloy of molten aluminum, magnesium, zinc, etc. is injected through a pouring hole of a pouring sleeve, and the molten metal is filled into a cavity of a mold at high speed and high pressure by an injection plunger to be injection-molded.

In this process, gases such as air and water vapor filled in the cavity may be mixed together and remain in the molten metal filled and compressed in the cavity at high speed. In particular, in the case of a product having a complicated shape, it may be more difficult to discharge air, water vapor, and residual gas in the cavity. Air, water vapor and gas remaining in the cavity mixed in the molten metal may cause casting defects (blowholes, shrinkage porosity defects, etc.) in the mold during cooling and solidification of the molten metal, which deteriorates the strength of the product.

High vacuum die casting is a technique for significantly reducing bubbles of a product manufactured by such a die casting method. According to this technique, a mold is sealed, and air in a mold cavity is reduced to 50mbar or less using a vacuum pump to make the mold cavity in a vacuum state, and then, a molten metal is injected into the cavity to manufacture a product. Therefore, there is no air hole in the product, and thus the strength of the product can be improved upon heat treatment.

That is, in the case of a general die cast part, heat treatment cannot be performed due to internal casting defects. However, high vacuum die cast products have no internal casting defects and therefore mechanical properties can be improved by about 40% by heat treatment.

However, the high vacuum apparatus is very expensive and the manufacturing cost increases.

The foregoing is intended only to aid in understanding the background of the disclosure and is not intended to represent that the disclosure falls within the scope of the prior art as known to those of ordinary skill in the art.

Disclosure of Invention

The present disclosure is directed to provide a vacuum die casting method and a mold for vacuum die casting, which can manufacture a high-quality and high-strength part by removing air in a mold cavity without using expensive equipment.

According to an aspect of the present disclosure, a vacuum die casting method may include the steps of: coupling the fixed mold and the movable mold to each other; closing a molten metal pouring hole formed on a sleeve formed on a lower side of a fixed mold or a movable mold by an injection plunger operating in the sleeve; vacuum-decompressing a cavity formed between a fixed mold and a movable mold by a vacuum decompression device connected to a chilled exhaust block provided at upper portions of the fixed mold and the movable mold; supplying oxygen to the cavity through an oxygen supply device connected to the quench exhaust block after the step of performing vacuum decompression is completed; and supplying molten metal to the cavity through the molten metal pouring hole.

In addition, the vacuum decompression device may be connected to the quenched exhaust block through a vacuum decompression pipe. The oxygen supply device may be connected to the chilled exhaust block by a vacuum relief line and an oxygen supply line.

In addition, in the step of performing vacuum pressure reduction, a vacuum pressure reducing valve provided in the vacuum pressure reducing pipe may be controlled to be opened according to a signal indicating that the molten metal pouring hole is closed.

In the step of performing vacuum decompression, vacuum decompression may be performed until the pressure in the cavity reaches 200mmHg or less.

Further, the step of supplying oxygen to the cavity may include: one oxygen supply was carried out until the pressure in the mould cavity reached over 1200 mbar. The step of supplying the molten metal to the cavity may be performed after the primary oxygen supply is completed. The step of supplying oxygen to the cavity may further include: after the step of supplying the molten metal to the cavity is started, a secondary oxygen supply is performed in which less oxygen is supplied than the primary oxygen supply.

The molten metal may be molten aluminum.

In addition, the vacuum die casting method may further include the steps of: after the step of supplying the molten metal to the cavity, the injection step is performed by operating an injection plunger. The secondary oxygen supply may be completed at a point of time when the injection plunger passes through the molten metal pouring hole in the injection step.

According to another aspect of the present disclosure, a mold for vacuum die casting may include: a fixed mold and a movable mold; an injection plunger operating in a sleeve formed at a lower side of the fixed mold or the movable mold; a vacuum decompression device connected to a chilled exhaust block provided at upper portions of the fixed mold and the movable mold and performing vacuum decompression of a cavity formed between the fixed mold and the movable mold; and an oxygen supply device connected to the quench exhaust block and supplying oxygen to the cavity.

In addition, the mold for vacuum die casting may further include: a vacuum pressure reducing pipe connected from the vacuum pressure reducing device to the quench exhaust block; the vacuum pressure reducing valve is arranged on the vacuum pressure reducing pipeline; an oxygen supply pipe connected from an oxygen supply device to the chilled exhaust block; and an oxygen supply valve provided on the oxygen supply pipe.

The vacuum relief valve may be controlled in response to a signal from a vacuum sensor disposed in the mold cavity. The oxygen supply valve may be controlled in accordance with a signal of an oxygen sensor provided in the cavity.

The quenched exhaust blocks may be formed in pairs in the fixed mold and the movable mold, respectively. The quench exhaust block may have a molten metal inlet communicating with an upper end of the cavity to introduce molten metal when the fixed mold and the movable mold are coupled to each other. The quench vent block may have a molten metal solidification flow path extending from the molten metal inlet and a vent hole in communication with the vacuum relief conduit.

In addition, the gap of the molten metal solidification flow path may be 1.0 to 1.2 mm.

In addition, the convex and concave portions in the molten metal solidification flow path are repeated and bent a plurality of times so that the cross section may have a triangular concave-convex structure.

Further, an inner angle of each of the convex and concave portions may have an angle of 40 degrees or less.

The chilled exhaust block may have equiangular cooling channels for efficient coolant flow.

According to embodiments of the present disclosure, the device may be simple by using relatively low cost active oxygen and vacuum assist. Also, the casting cost of the apparatus may be about 10% to 20% of the cost of the high vacuum equipment, and thus the cost may be significantly reduced.

This simple device allows the removal of air from the mould cavity and allows the manufacture of high quality and high strength parts.

The strength of the device can be improved by about 30% or more compared to other general die-casting devices.

Therefore, the apparatus in the present disclosure can suppress casting defects caused by residual gas, thereby further expanding the application field of die casting with excellent productivity. In particular, the apparatus can make die casting used for manufacturing high performance parts with the trend toward motorization and environmental conservation of vehicles.

Drawings

The above and other objects, features and advantages of the present disclosure will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a flow chart illustrating a vacuum die casting method according to the present disclosure;

fig. 2A to 2G sequentially illustrate a vacuum die casting method according to the present disclosure;

fig. 3A and 3B illustrate a chilled exhaust block as part of a mold for vacuum die casting according to the present disclosure;

FIG. 4 shows a portion of FIG. 3A; and

fig. 5A and 5B comparatively show the side shapes of the molten metal solidification flow paths of the quenched exhaust block of fig. 3A and 3B.

Detailed Description

For a fuller understanding of the present disclosure, the operating advantages thereof, and the objects attained by the embodiments of the present disclosure, reference should be made to the accompanying drawings that illustrate embodiments of the present disclosure and to the contents described in the accompanying drawings.

In describing the embodiments of the present disclosure, detailed and repetitive description of known technologies related to the present disclosure has been shortened or omitted, otherwise the gist of the present disclosure may be obscured.

Fig. 1 is a flow chart illustrating a vacuum die casting method according to the present disclosure. Fig. 2A to 2G sequentially illustrate a vacuum die casting method according to the present disclosure.

Hereinafter, a vacuum die casting method and a mold for vacuum die casting according to an embodiment of the present disclosure are described with reference to a flowchart of fig. 1 and sequential processes of fig. 2A to 2G.

The present disclosure relates to a method of manufacturing a part of a vehicle or the like by die casting and a mold for implementing the method. According to the technology of the present disclosure, a vacuum can be formed without a separate expensive vacuum pump for forming a vacuum in a mold cavity, so that a cast product does not generate a bubble defect, and thus a heat treatment can be performed. Therefore, a cast component having excellent strength can be manufactured with a relatively simple configuration and at low cost.

The mold for vacuum die casting may include a fixed mold 110 and a movable mold 120. First, as shown in fig. 2A, a release agent spray 130 may be sprayed to the surface of the mold cavity, and then the mold may be closed (S11). In this way, the casting operation can be prepared.

The quench exhaust blocks 160 and 160-1 may be disposed at upper portions of the fixed mold 110 and the movable mold 120 corresponding to upper portions of the cavities, respectively. Thus, gas in the mold may be discharged through the quench blocks 160 and 160-1 in a short time, and molten metal leakage may be prevented.

Further, a sleeve 140, which is a path of the molten metal, may be formed at a lower side of the fixed mold 110. Thereby, an injection path of the molten metal is formed from the sleeve 140 to the cavity.

A molten metal pouring hole 141 into which molten metal is poured may be formed on the sleeve 140 and coupled to an injection plunger operating in a longitudinal direction of the sleeve 140.

As shown in fig. 2B, when the fixed mold 110 and the movable mold 120 are coupled to each other through S11, the injection plunger head 150 may move forward to close the molten metal pouring hole 141 (S12).

The vacuum relief device 210 and the oxygen supply device 310 may be disposed outside the mold to form a vacuum in the cavity. The vacuum decompression pipe 220 and the oxygen supply pipe 320, which are connected from the vacuum decompression device 210 and the oxygen supply device 310, respectively, may be connected to the quenched exhaust blocks 160 and 160-1.

As shown, the oxygen supply line 320 may be connected to the chilled exhaust blocks 160 and 160-1 by being connected to the vacuum relief line 220.

According to the signal indicating that the molten metal pouring hole 141 is closed (S12), the vacuum relief valve 230 provided in the vacuum relief pipe 220 may be controlled to be opened (S21) so that the cavity may be vacuum-relieved (S22).

Vacuum decompression may be performed until preset decompression conditions and time are satisfied (S23). Thereafter, as shown in fig. 2C, the vacuum pressure reducing valve may be controlled to be closed (S24). For example, the reduced pressure condition in S23 may be set to 200mmHg or less.

A vacuum sensor may be provided in the cavity to check the conditions in S23. S24 may be controlled by the signal of the vacuum sensor.

When the vacuum relief valve is closed (S24), the oxygen supply valve 330 disposed in the oxygen supply pipe 320 may be controlled to be opened (S25) so that oxygen may be supplied to the cavity through the quench exhaust blocks 160 and 160-1.

The oxygen supply may be performed until preset compression conditions and time are satisfied (S26). Thereafter, as shown in fig. 2D, the injection plunger head 150 may be moved backward (S13) to open the molten metal pouring hole 141. The molten metal m may be quantitatively supplied to the cavity through the opened molten metal pouring hole 141 (S14). When the supply of the molten metal is completed, as shown in fig. 2E, injection may be performed (S15).

An oxygen sensor may be provided in the cavity to check the conditions in S26. S13 may be controlled by the signal of the oxygen sensor.

The filling or supply of oxygen may be performed to have a maximum filling capacity in a short time. The filling of oxygen, i.e. the oxygen supply, can be performed within e.g. 3 seconds and at a set pressure set, e.g. above 1200 mbar.

Even after the supply of the molten metal is started, the supply of the oxygen may not be stopped immediately, but may be continued (S27). However, the oxygen supply amount may be reduced from the time point when the molten metal pouring hole 141 is opened, as compared with the oxygen supply amount in S25.

In the present disclosure, air in the cavity and sleeve may be replaced with reactive oxygen through the primary oxygen supply in S25. Chemical reaction between the reactive oxygen gas and the molten metal may occur by the molten metal being supplied after the maximum primary oxygen supply and injection.

For example, the molten metal may be molten aluminum. When a chemical reaction occurs between the molten metal and the reactive oxygen gas, fine oxides (Al) may be formed₂O₃) To create a partial instantaneous vacuum in the mold cavity. Residual oxygen and reaction products that fail to react with the molten metal can be removed by injection.

Therefore, in order to form a partial instantaneous vacuum in the cavity, as shown in fig. 2D, it is also necessary to perform oxygen supply in the molten metal supply S14 before injection. The secondary oxygen supply in S27 may be 15% to 40% of the primary oxygen supply in S25.

In addition, when filling the mold cavity with oxygen, i.e., supplying oxygen to the mold cavity, even if the oxygen supply is controlled to have a set supply time and an adjusted supply amount, it may not be guaranteed that a full amount of oxygen is supplied every shot (shot) according to the sealing condition of various parting lines (parting lines) of the cavity. To solve this problem, the present disclosure uses a digital pressure gauge as an oxygen sensor to check whether the cavity is stably filled with oxygen.

Next, as shown in fig. 2E, when injection is started in S15 and the injection plunger head 150 closes the molten metal pouring hole 141(S16), the oxygen supply valve 330 may be controlled to be closed according to a signal indicating the pouring hole closing. Accordingly, the oxygen supply may be blocked (S28).

In addition, when the injection plunger head 150 is switched at a high speed (S17), the vacuum relief valve 230 may be opened to discharge residual gas in the mold cavity (S29).

Thereafter, the molten metal is solidified and cooled. Then, as shown in fig. 2G, the mold may be opened to take out the cast product P (S18).

In the present disclosure, assuming a case where oxygen is supplied through the sleeve 140 to form a vacuum, the flow path portion may be filled with oxygen passing through the sleeve. The cavity may then be filled with oxygen through a gate having a narrow cross-sectional area. Therefore, the mold cavity portion actually required to be filled with oxygen is eventually filled after the oxygen passes through the gate having a narrow cross-sectional area. Thus, the mold cavity may not be completely filled with oxygen.

Thus, the present disclosure uses oxygen filling in the opposite direction, i.e., through the chilled exhaust block on the upper end portion of the mold. Therefore, it is possible to first supply oxygen to fill the mold cavity, which is the core part of controlling the functional quality, and then to fill the gates, runners, and sleeves. In this way, the required oxygen filling in the mould cavity can be effectively maximised, which is advantageous in terms of the formation of an instantaneous vacuum in the cavity.

In the present disclosure, the oxygen supply may be through the quench exhaust blocks 160 and 160-1 as described above. In addition, by the size and structure of the quench exhaust blocks 160 and 160-1, it is possible to effectively reduce the time for oxygen supply, maximize the amount of oxygen supply, and prevent molten metal leakage.

Fig. 3A and 3B illustrate a chilled exhaust block as part of a mold for vacuum die casting according to the present disclosure. Fig. 4 shows a portion of fig. 3A.

The quenched exhaust blocks may be formed in pairs at the fixed mold 110 and the movable mold 120, respectively, to correspond to each other. Fig. 3A shows a quench exhaust block 160 formed on the stationary mold, and fig. 3B shows a quench exhaust block 160-1 formed on the movable mold. The chilled exhaust blocks may be coupled to one another to form a chilled exhaust flow path. The chilled exhaust blocks 160 and 160-1 may correspond to each other in a concave-convex relationship. The relief relationship may be the inverse of that depicted and described in the disclosed embodiments.

For example, the chilled exhaust block 160 of the fixed mold 110 side may have: a molten metal inlet 161 communicating with an upper end of the cavity to introduce molten metal; a molten metal solidification flow path 162 extending from the molten metal inlet 161 in the width direction; and an exhaust hole 163 formed above the molten metal solidification flow path 162 and the exhaust hole 163 communicates with the vacuum decompression pipe 220.

The quench vent block 160-1 on the movable mold 120 side may also have a molten metal solidification flow path 162-1 corresponding to the molten metal solidification flow path 162 of the quench vent block 160 on the fixed mold 110 side. Both molten metal solidification flow paths 162 and 162-1 may be coupled to each other to form a flow path between the molten metal solidification flow paths 162 and 162-1.

In addition, a vent hole 163-1 may be formed above the molten metal solidification flow path 162-1. As shown, the discharge holes 163-1 of the quench discharge block 160-1 of the movable mold 120 side may be closely inserted into the corresponding discharge holes 163 of the quench discharge block 160 on the fixed mold 110. The insert structure may also be oppositely disposed or formed and vice versa.

In typical die casting of the prior art, the quench block is designed to have a maximum clearance of 0.3 to 0.5mm to prevent leakage of molten metal injected at high speed and high pressure. However, in the present disclosure, the molten metal inlet 161 and the molten metal solidification flow path formed by the two molten metal solidification flow paths 162 and 162-1 may have different gaps from each other for effective vacuum decompression and oxygen supply.

In other words, the molten metal inlet 161 may have a gap g0 of 3 to 4 mm. The molten metal solidification flow path may be designed to have a gap g1 or g2 of 1.0 to 1.2mm, the gap g1 or g2 being 3 to 4 times that of the conventional gap. The same gap from g1 to g2 can be maintained. In this way, the active oxygen gas can be smoothly supplied and the supply time can also be minimized.

Further, the gap (labeled g1) from the gap of the molten metal inlet 161 to the point where the molten metal solidification flow path starts may gradually decrease.

To this end, the quench exhaust blocks 160 and 160-1 may have a different shape than a common or conventional quench exhaust block. In other words, in order to prevent the leakage of the molten metal while smooth vacuum decompression and oxygen supply when injection is performed at high speed and high pressure, the quench exhaust blocks 160 and 160-1 may be characteristically designed to have a washboard-like shape to maximize the cross-sectional area of the molten metal solidification flow path and have equiangular cooling channels for the efficient flow of the cooling liquid. Equiangular cooling channels with a curved form are more efficient.

In other words, as shown in the drawing, the cross section of the molten metal solidification flow path may have a triangular, i.e., serrated, concavo-convex structure. In this manner, the alternating convex portions 162-3 and concave portions 162-4 repeat and bend a plurality of times in each of the molten metal solidification flow paths 162 and 162-1. In an example, the protrusion 162-3 may be formed at least six times and at most fifteen times.

The convex and concave portions formed in a continuous curve or zigzag shape may be more advantageous in preventing the molten metal from leaking when having more stages. On the other hand, having the projections and recesses of fewer steps can reduce the loss such as the recovery rate and the mold size. Therefore, in order to prevent the molten metal from leaking and being lost, the convex and concave portions need to have the above-described number of stages.

In addition, the inner angle of each of the convex portion 162-3 and the concave portion 162-4 may have an angle of 40 degrees or less as in the example of fig. 5B, instead of an angle of about 90 degrees as shown in fig. 5A.

When the internal angle is about 90 degrees as shown in fig. 5A, the molten metal can be easily discharged. However, when the interior angle is 40 degrees or less as shown in fig. 5B, the cross-sectional area of the molten metal solidification flow path can be advantageously maximized. Therefore, during passing through the protrusions 162-3 each having a narrow cross-sectional area, the molten metal may be more easily solidified and thus the molten metal may be prevented from leaking.

As described above, in the present disclosure, defects generated in die casting can be minimized without any high vacuum die casting apparatus, and thus physical properties of a cast product can be improved. The following table shows the above comparison.

Although the present disclosure has been described with reference to the accompanying drawings, it should be apparent to those of ordinary skill in the art that the present disclosure is not limited to the above-described embodiments. Various modifications and changes may be made to the disclosed embodiments without departing from the spirit and scope of the disclosure. Accordingly, such modifications and changes are considered to fall within the claims of the present disclosure, and the scope of the present disclosure is to be interpreted based on the following claims.

Claims

1. A vacuum die casting method comprising the steps of:

coupling the fixed mold and the movable mold to each other;

closing a molten metal pouring hole formed on a sleeve formed on a lower side of the fixed mold or the movable mold by an injection plunger operating in the sleeve;

vacuum-decompressing a cavity formed between the fixed mold and the movable mold by a vacuum decompression device connected to a chilled air discharging block provided at upper portions of the fixed mold and the movable mold;

supplying oxygen to the cavity through an oxygen supply device connected to the chilled exhaust block after the step of performing the vacuum decompression is completed; and

supplying molten metal to the cavity through the molten metal pouring hole.

2. The vacuum die casting method according to claim 1,

the vacuum decompression device is connected to the chilled exhaust block by a vacuum decompression pipe, and

the oxygen supply device is connected to the chilled exhaust block through the vacuum relief pipe and an oxygen supply pipe.

3. The vacuum die casting method according to claim 1,

and in the step of performing vacuum pressure reduction, controlling a vacuum pressure reducing valve provided in a vacuum pressure reducing pipe to be opened according to a signal indicating that the molten metal pouring hole is closed.

4. The vacuum die casting method according to claim 3,

the vacuum decompression is performed until the pressure in the cavity reaches 200mmHg or less.

5. The vacuum die casting method according to claim 1,

the step of supplying oxygen to the cavity comprises: a supply of oxygen is carried out until a pressure in the mould cavity of above 1200mbar is reached,

the step of supplying the molten metal to the cavity is performed after the primary oxygen supply is completed, and

the step of supplying oxygen to the cavity further comprises: after the start of supplying the molten metal to the cavity, a secondary oxygen supply is performed in which less oxygen is supplied than the primary oxygen supply.

6. The vacuum die casting method according to claim 5,

the molten metal is molten aluminum.

7. The vacuum die casting method according to claim 5, further comprising the steps of:

performing injection by operating the injection plunger after supplying the molten metal to the cavity; and

completing the secondary oxygen supply at a point in time during the injection when the injection plunger passes through the molten metal pouring orifice.

8. A mold for vacuum die casting, the mold comprising:

a fixed mold and a movable mold;

an injection plunger operating in a sleeve formed at a lower side of the fixed mold or the movable mold;

a vacuum decompression device connected to a chilled exhaust block provided at upper portions of the fixed mold and the movable mold, and performing vacuum decompression of a cavity formed between the fixed mold and the movable mold; and

an oxygen supply connected to the chilled exhaust block and supplying oxygen to the cavity.

9. The mold of claim 8, further comprising:

a vacuum pressure reducing pipe connected from the vacuum pressure reducing device to the quenched exhaust block;

the vacuum pressure reducing valve is arranged on the vacuum pressure reducing pipeline;

an oxygen supply conduit connected from the oxygen supply to the chilled exhaust block; and

an oxygen supply valve disposed on the oxygen supply conduit.

10. The mold of claim 9,

the vacuum relief valve is controlled according to a signal of a vacuum sensor provided in the cavity, and

controlling the oxygen supply valve according to a signal of an oxygen sensor provided in the cavity.

11. The mold of claim 8,

the quenched exhaust blocks are formed in pairs in the fixed mold and the movable mold, respectively, and

the quench exhaust block has a molten metal inlet communicating with an upper end of the cavity to introduce the molten metal when the fixed mold and the movable mold are coupled to each other, and has a molten metal solidification flow path expanding from the molten metal inlet and an exhaust hole communicating with the vacuum decompression pipe.

12. The mold of claim 11,

the gap of the molten metal solidification flow path is 1.0 to 1.2 mm.

13. The mold of claim 11,

the convex and concave portions in the molten metal solidification flow path are repeated and bent a plurality of times so that the cross section has a triangular concave-convex structure.

14. The mold of claim 13,

an inner angle of each of the convex portion and the concave portion is 40 degrees or less.

15. The mold of claim 8,

the chilled exhaust block has equiangular cooling channels for efficient coolant flow.