KR20160142641A - Continuous Low Pressure Die Casting Method for Magnesium Alloy - Google Patents

Abstract

The present invention relates to a melting furnace for dissolving a magnesium ingot to make a magnesium molten metal; A warming furnace accommodating the magnesium molten metal and supplying the molten magnesium to the mold; And a metal pump for transferring the molten metal from the melting furnace to a heating furnace, comprising the steps of: a first step of casting a unit road wheel by pressurizing a molten metal of a heating furnace with a metal mold; A second step of detecting a change (? L) in the level of the molten metal in the warming furnace; A third step of supplying the molten metal of the melting furnace to the heating furnace by using the metal pump; And a fourth step of introducing and dissolving the magnesium ingot into the melting furnace, wherein the first to fourth steps are sequentially repeated, and the pressurized state is continuously maintained in the first to fourth steps A low-pressure continuous casting method of a magnesium alloy is provided.
The low-pressure casting technology for a magnesium alloy according to the present invention improves the productivity by continuously carrying out the magnesium alloy casting process, and maintains a constant pressure state without completely releasing the internal pressure of the hot- So that the water level of the magnesium melt in the inside of the stock is prevented from being lowered, and the oxidation caused by the contact with the air on the inner surface of the stock can be prevented.

Description

{Continuous Low Pressure Die Casting Method for Magnesium Alloy}

The present invention relates to a method of low-pressure continuous casting with a magnesium alloy material.

Specifically, in the process of casting the product by injecting the magnesium melt into the inside of the stock in the low-pressure casting machine, the pressurized state is maintained at a certain level even after the product is solidified, thereby maintaining the level of the molten metal in the stock, The present invention also relates to a technique capable of continuously casting a casting continuously and continuously casting the molten magnesium so that the molten magnesium can always be maintained in a heating furnace accommodating the molten magnesium. An example of a product cast in this way is a car road wheel.

The low-pressure casting is performed by injecting inert gas such as dry air or nitrogen gas into the melting furnace installed in the lower part of the casting machine and injecting molten metal (molten metal) through a molten metal injection pipe (stalk) This is a casting method injected into a mold.

Such low pressure casting method is widely used as a casting method of various products and is widely applied to casting of a road wheel of an automobile. In recent years, many studies have been made to manufacture automobile road wheels with magnesium in order to improve fuel efficiency through light weight of automobiles, and magnesium rod wheels are being produced in some parts. In particular, the development of lightweight parts using the low-pressure casting technique as the lightest magnesium alloy among structural materials has been actively promoted both domestically and abroad.

The difficulty in casting of such a magnesium alloy is that the magnesium alloy molten metal is extremely oxidative, and when it comes into contact with air in the atmosphere, there is always a risk of ignition due to oxidation, fire, etc. In order to prevent such oxidation, A protective gas for preventing oxidation such as sulfur fluoride (SF6) gas is injected and cast. Particularly, in consideration of the fact that the magnesium molten salt reacts with oxygen in the atmosphere to form magnesium oxide (MgO), and when the magnesium oxide continues to accumulate, there is a danger of reacting with moisture or oxygen in the air to ignite or explode. In the case where the magnesium molten metal exists in a region in contact with air, it has been necessary to prevent this phenomenon by using a protective gas.

Patent No. 10-1460572 discloses a conventional patent for a low-pressure casting technique. In the case of a molten metal filled in a stalk, it is difficult to prevent the surface of the molten metal from being oxidized, In order to overcome the difficulty of casting due to this clogging, a protective gas injector is installed in the intermediate stoke to prevent the generation of oxides in the molten magnesium alloy in the stoke and the clogging of the stoke.

Briefly, the patent of the applicant includes a melting furnace (1) for dissolving a magnesium alloy in the lower part; A warming furnace (2) installed in the melting furnace (1) and being a container for melting the magnesium alloy (3); A main stalk 5 for firstly injecting the molten magnesium alloy melt 3 into the warming furnace 2 and an intermediate stalk 10 for connecting the main stalk 5 and the two mold injection openings 2 are provided . A heat insulating material 16 of ceramic material for keeping the intermediate stalk 10 warm can be further coupled and a protective gas injection pipe 18 penetrates the center of the intermediate stalk body 11. The injection of the protective gas is automatically stopped when the magnesium alloy melt 3 starts to rise at the initial stage of the air and nitrogen pressurization in the melting furnace 1 and the magnesium alloy melt 3 is completely filled in the mold and the intermediate stalk 10 The molten magnesium alloy melt 3 is prevented from being oxidized and clogging of the inside of the stoke due to the oxide is controlled by controlling the injection of the protective gas again when the remaining molten metal in the molten magnesium alloy falls.

These conventional techniques have the following two problems.

First, a predetermined amount of magnesium melt is injected into the melting furnace 1, and a certain number of rod wheels (usually about 30) are cast using the molten magnesium melt. Thereafter, a new magnesium melt should be injected into the melting furnace. However, the magnesium molten metal has problems such as oxidation when it comes into contact with the atmosphere, and the sludge is left inside the pipe where the molten metal is present or flowing. That is, the sludge and the like are thoroughly cleaned, the magnesium melt is injected into the melting furnace 1 again, and a certain number of the rod wheels are cast again.

As a result of this process, the process becomes complicated and the casting process becomes intermittent, resulting in a decrease in the productivity of the product.

Secondly, even in such a conventional technique, it is difficult to fundamentally prevent the oxidation caused by the contact of the magnesium alloy melt existing in the stoke with the air. That is, during the casting, the product is produced by pressurizing the internal pressure of the warming furnace, and then the pressure inside the warming-up furnace is released. As the melt moves downward in the stoke, the magnesium melt is deposited on the inner wall of the stock, The magnesium oxide forms a magnesium oxide by reacting with oxygen in the magnesium oxide. When the magnesium oxide is continuously accumulated, the magnesium oxide reacts with moisture or oxygen in the air to cause ignition and explosion.

As a result, it is necessary to reduce the space in which the magnesium melt contacts the air as much as possible, so that the rod wheel low pressure casting process needs to be continued.

It is an object of the present invention to provide a magnesium alloy casting machine capable of continuously casting a casting from a magnesium alloy in a low-pressure casting machine, thereby enhancing productivity and maximally preventing the possibility that the magnesium molten metal reacts with air to oxidize or ignite. Low-pressure casting technology.

The present invention relates to a melting furnace for dissolving a magnesium ingot to make a magnesium molten metal; A warming furnace accommodating the magnesium molten metal and supplying the molten magnesium to the mold; And a metal pump for transferring the molten metal from the melting furnace to a warming furnace, the method comprising: a first step of casting a unit road wheel by pressing a molten metal in a warming furnace with a metal mold; A second step of detecting a change (? L) in the level of the molten metal in the warming furnace; A third step of supplying the molten metal of the melting furnace to the heating furnace by using the metal pump; And a fourth step of introducing and dissolving the magnesium ingot into the melting furnace, wherein the first to fourth steps are sequentially repeated, and the pressurized state is continuously maintained in the first to fourth steps A low-pressure continuous casting method of a magnesium alloy is provided.

The unit casting is cast 3 to 5 times in the first step and the change in the level of the molten metal is detected in the second step.

The pressurized state is maintained between the unit casting of the first stage and the casting of the unit casting so that the level of the molten metal is also maintained in the inside of the stocking.

A main stocker (62) installed in the thermal insulating furnace and into which molten magnesium is injected; A substock (64) connecting the injection port of the main stalk and the mold; And a pressurizing device (40) for pressurizing the molten magnesium contained in the inside of the insulated furnace so as to be supplied to the mold,

A first step of pressurizing the magnesium melt while gradually raising the pressure inside the heat retaining furnace from the initial start pressure P0 to the maximum pressure P4 with the pressurizing device and injecting the molten magnesium into the mold; And a second step of coagulating the magnesium melt in the mold while maintaining the pressure inside the heat insulating furnace at the maximum pressure P4 with the pressurizing device; And a third step of reducing the pressure inside the heat insulating furnace to an intermediate pressure (DELTA P) after completion of solidification to maintain the water level of the molten metal in the substock at a constant level, wherein the intermediate pressure (DELTA P Becomes a pressure between the start pressure P0 and the maximum pressure P4.

In the step 1-3, the level of the molten metal is maintained at the level of the molten metal up to the upper end of the sub-stoke.

The low-pressure casting technology for a magnesium alloy according to the present invention improves the productivity of a magnesium alloy casting product by continuously carrying out a magnesium alloy casting process,

Even if the solidification of the rod wheel casting product is completed, it is possible to keep the constant pressure state continuously without completely releasing the internal pressure of the warming furnace, thereby preventing the lowering of the level of the magnesium melt in the inside of the stoking chamber, An effect that can be prevented is generated.

1 is a schematic view of the configuration of a low-pressure casting machine and a melting furnace according to the present invention,
2 shows a state in which the water level in the heating furnace is lowered due to the casting,
3 shows a state in which a molten metal is generated as a magnesium ingot is introduced into a melting furnace,
FIG. 4 is a cross-sectional view of a magnesium casting low-pressure casting machine according to the present invention,
5A and 5B are graphs showing a comparison of changes in the internal pressure state of a low temperature casting machine for magnesium casting according to the present invention,
FIGS. 6A and 6B show advantageous effects of the method of maintaining the pressurized state of the low temperature casting machine for magnesium casting according to the present invention.

The characteristics of the present invention are as follows: 1) the magnesium alloy casting process is continuously performed; and 2) even when solidification of the rod wheel casting product is completed, the internal pressure is not completely released, The most important feature is to prevent the level of the molten metal from going down.

The continuous casting method described in the description of the present invention can be applied to a low pressure casting method of various products utilizing magnesium. In the following description, the manufacture of a vehicle road wheel is described with reference to the drawings. However, this is only an example, and the low-pressure continuous casting method of the present invention can be applied to all magnesium parts that can be produced by low-pressure casting to be.

First, the above feature 1) will be described and then the feature 2) will be described.

1, a low pressure casting machine according to the present invention includes a low pressure casting machine 100 having a warming furnace 20 and a mold 10 on the upper side thereof and a magnesium ingot I And a melting furnace 200 for containing the magnesium molten metal.

The constitution of the low-pressure casting machine 100 shown in Fig. 1 is only a part of the constitution necessary for the explanation.

The protective gas injector 50 for injecting the protective gas into the thermal insulation furnace is provided in the thermal insulation cover 30 of the low-pressure casting machine 100. The protective gas injected into the thermal insulation furnace is composed of sulfur hexafluoride (SF6) However, it may be a mixed gas in which carbon dioxide (CO2) to nitrogen (N2) are mixed. The protective gas acts to prevent the magnesium melt from igniting.

The low pressure casting machine 100 is provided with a plurality of stalk 60 for supplying molten magnesium in the thermal insulating furnace 20 to the metal mold 10 and a level sensor L for sensing the level of the molten metal, And a temperature sensor for sensing the temperature of the molten metal.

The melting furnace 200 has a case in which the magnesium ingot I is dissolved and a lid 210 on the upper side. In the lid, a charging port into which a magnesium ingot can be charged is formed, and an ingot An injector 250 is provided. The melting furnace is a place where a magnesium ingot is dissolved to make a molten metal, and a temperature sensor is preferably provided. The internal temperature is preferably maintained at about 650 to 700 ° C, and may be varied depending on the kind of the magnesium alloy.

The present invention further includes a metal pump (300) for transferring the molten metal of the melting furnace to the warming furnace (20). The metal pump 300 communicates with the molten metal in the melting furnace 200 through the first transfer pipe 320 and the molten metal in the thermal insulating furnace 20 through the second transfer pipe 340. The first conveying pipe to the second conveying pipe may be provided with a heater at an appropriate place so that the molten metal does not coagulate while being conveyed.

The specification of the metal pump 300 of the present invention is that the magnesium melt should be transferred to the warming furnace with an injection rate of 6 kg / s. However, the injection speed of the metal pump may be variable considering the casting speed and the heating furnace capacity.

Although not shown in the drawing, the apparatus further includes a preheater (not shown) for preheating the magnesium ingot I before being introduced into the melting furnace 200. The preheater removes the moisture contained in the magnesium ingot and eliminates the risk of explosion. It is a device that preheats the magnesium ingot to about 200 ~ 300 ℃. The preheater is equipped with a conveyor belt that rotates with a motor and is preheated by a heater while automatically transferring the magnesium ingot.

FIG. 1 shows a state in which the molten metal in the heat insulating furnace 20 is filled in an initial state before the casting process is started. The second transfer pipe 340 connected to the metal pump 300 and the heat insulating furnace 20 are completely shut off so that there is no reverse flow of the magnesium melt in the heat insulating furnace even if the inside of the heat insulating furnace is pressurized for casting.

Fig. 2 is a view showing a state in which the casting product W is manufactured by pressing the inside of the heat insulating furnace 20 in the state of Fig. 1 to perform casting. The inside of the heating furnace is pressurized and the molten metal rises through the stalk 60 to be injected into the mold 10, and the molten metal solidifies and the product is cast. When several rod wheels are cast, a change (? L) in the level of the molten metal in the warming furnace 20 occurs. As a result of the casting of three to five rod wheels in the apparatus of the applicant of the present invention, the change in the liquid level of the molten metal in the warming furnace 20 is about 3 to 5 cm, It comes. Then, the level sensor (L) provided in the warming furnace senses the falling of the molten metal level and activates the metal pump (300) so that the magnesium molten metal is pushed into the heating furnace. At this time, the pressurized state inside the heat insulating furnace is maintained. That is, the magnesium molten metal is supplied into the heating furnace while maintaining the pressurized state, and this is the greatest feature of the present invention.

When the magnesium molten metal is continuously injected into the heating furnace through the metal pump while the continuous casting is being performed, the magnesium molten metal in the heating furnace is changed only by about 3 to 5 cm. That is, the inside surface of the heating furnace (or crucible) is lowered as a whole to lower the level of the molten metal, thereby preventing the inside wall surface of the heating furnace (crucible) from being exposed and becoming sludge. Therefore, the present invention can maintain the degree of cleanliness of the molten metal by keeping the level of the molten metal almost constant.

FIG. 3 shows a state in which the dissolution occurs while the magnesium ingot is automatically injected into the melting furnace 200.

In the present invention, since the pressure is maintained at the constant pressure without completely releasing the pressing force even in the intermediate step of casting the one rod wheel and then casting the next load wheel, the inside of the stock 60 is also continuously present, Sludge can be prevented from being generated and the inner wall surface of the stock can be prevented from being oxidized. In the intermediate stage, the change in the stokes level (SL) is controlled to a small value at the upper portion of the stoke to prevent the formation of stoke and oxidation of the inside of the stoke.

The principle of preventing sludge and oxidation of the inner wall of the stoke will be described in more detail in the description 2) description below.

Feature 2) explains the advantage of continuing to maintain a certain level of pressure without completely releasing the pressure inside the warming furnace even if the solidification of the rod wheel casting product is completed.

First, the magnesium casting low-pressure casting machine according to the present invention is schematically shown at 100 in FIG. 1, but will be described in detail with reference to FIG. 4, only the low-pressure casting machine 100 is shown except for the melting furnace 200 and the metal pump 300. The specific configuration may be slightly different from that shown in FIG. 1, Will be.

4, the low pressure casting machine includes a mold 10 in which a magnesium casting is cast; A warming furnace 20 in which the magnesium melt M is accommodated; An insulating path cover 30 coupled to the upper portion of the thermal insulation furnace 20; A pressurizing device 40 for pressurizing the molten magnesium M contained in the inside of the insulated furnace 20 to be supplied to the mold 10; A first protective gas injection device 50 for injecting a protective gas into the inside of the heat insulating furnace 20; A plurality of stalk (60) for supplying molten magnesium (M) in the warming furnace (20) to the mold (10); And a plurality of molten metal injection ports (70) for injecting the molten magnesium (M) supplied from the plurality of the stokes (60) into the mold (10). According to the present invention, the magnesium molten metal (M) is rapidly injected into the mold (10) including a plurality of the stokes (60) and a plurality of molten metal injection ports (70) Is injected efficiently. Further, the first protective gas injector 50 prevents the magnesium melt (M) from being oxidized and ignited in the warming chamber (20).

In the present invention, magnesium is collectively referred to as magnesium and magnesium alloy, and "magnesium melt" includes a melt of magnesium (Mg) and a melt of magnesium alloy. And includes the upper mold 11, the lower mold 12, and the left and right molds 13 and 14, which are cast (molded) from the magnesium casting. A cavity (C) is formed in the mold (10). The cavity C may have various shapes depending on the desired cast product (product). In the drawing, the shape of the cavity C corresponding to a road wheel of an automobile is illustrated.

At this time, at least one of the upper mold 11, the lower mold 12, and the left and right molds 13 and 14 may be movable in a vertical direction or a horizontal direction. Referring to FIG. 4, for example, the upper mold 11 can be moved in the vertical direction by the vertical moving means 16. The left and right molds 13 and 14 can be moved in the horizontal direction by the horizontal moving means 17 and 18, respectively.

The vertical movement means 16 and the horizontal movement means 17 and 18 may comprise actuators which operate by means of electric, hydraulic or pneumatic actuation. Figure 4 shows the vertical movement means 16 and horizontal movement means 17 ) 18, which illustrates a cylinder structure operated by hydraulic pressure or air pressure. The mold 10 can be supported by the vertical support member F1 and the horizontal support member F2. In addition, the mold 10 is provided with a molten metal inlet 70 into which a molten magnesium M is injected. The molten metal injection port 70 provides a flow path through which the molten magnesium M can be injected into the cavity C of the mold 10. In the present invention, Respectively. A stoke (60) is connected to the molten metal inlet (70) to inject molten metal. A housing 25 may be provided on the outside of the heat insulating furnace 20. The housing 25 may protect the warming furnace 20 or provide warmth. The housing 25 may have a function of a warming furnace to prevent the molten magnesium M contained in the warming furnace 20 from solidifying. A heat insulating path cover 30 is coupled to the upper part of the heat insulating furnace 20.

The pressurizing device 40 pressurizes the molten magnesium M contained in the insulated furnace 20 to be supplied to the mold 10. In the present invention, the pressurizing device 40 may be any one capable of providing a pressure for supplying the molten magnesium (M) in the warming furnace 20 to the mold (10). The pressurizing device 40 includes a pressurized gas storage tank 41 and a pressurized gas injection pipe 42 for injecting the pressurized gas stored in the pressurized gas storage tank 41 into the inside of the heat insulating furnace 20, . ≪ / RTI > The pressure device 40 is an optional component and includes a pressure regulator 43 for regulating the pressure of gas injected into the insulated furnace 20 and a control section 44 for controlling the pressure regulator .

The first protective gas injector 50 injects a protective gas into the inside of the heat insulating furnace 20. In the present invention, the protective gas is not particularly limited as long as it can prevent oxidation of the magnesium molten metal (M). For example, the protective gas is selected from sulfur hexafluoride (SF6), argon (Ar) . The first protective gas injector 50 may be configured to inject a protective gas into the inside of the warming furnace 20. The first protective gas injection device 50 includes a protective gas storage tank 52 and a first protective gas injection pipe (not shown) for injecting the protective gas stored in the protective gas storage tank 52 into the inside of the thermal insulating furnace 20 54). The molten magnesium melt M contained in the warming furnace 20 flows into the interior of the stock 60 by the urging force of the pressurizing device 40 and then rises along the stock 60 and flows through the molten metal inlet 70 10). At this time, as shown in FIG. 4, when the mold 10 is installed on the upper part of the heat insulating furnace 20, the stalk 60 may be installed through the heat insulating furnace cover 30. That is, as shown in FIG. 4, the stalk 60 passes through the heat insulating cover 30, one side thereof is charged into the warming furnace 20, and the other side thereof is connected to the molten metal inlet 70.

When the pressure is applied to the pressurizing device 40, the molten magnesium M is injected into the mold 10 at a high speed along the plurality of the stokes 60 and the plurality of the molten metal injection ports 70. Accordingly, before the magnesium melt M solidifies, the magnesium melt M is quickly injected and filled in the entire region of the mold 10, so that the upper and the lower portions of the mold 10 can be made of high quality Of magnesium castings are cast.

According to a preferred embodiment of the present invention, the stoke 60 includes a main stalk 62 charged in the heat insulating furnace 20, and a main stoke 62 connected to the main stoke 62 and the melt inlet 70 And a sub-stalk (64). At this time, the main stalk 62 and the sub-stalk 64 can be fastened by the insulating path cover 30. As shown in FIG. 4, the sub-stokes 64 may be exposed to the outside. The first protective gas injection device 50 may further include a control valve V for controlling the injection of the protective gas. This control valve V may be installed in each injection pipe 54. [

As described above, the mold 10 of the low-pressure casting machine according to the present invention includes the upper mold 11, the lower mold 12, and the left and right molds 13, ) ≪ / RTI >

5a and 5b are graphs showing changes in the internal pressure state of the low temperature casting machine for casting magnesium according to the present invention. And that it has a beneficial effect of maintaining the state.

A brief description will be given of a process of casting a magnesium molten metal into a mold. In the initial state in which the pressure inside the warming chamber 20 is not pressurized by the pressurizing unit 40, (P0 in Fig. 5A). Here, when the casting process is started, the pressure device 40 gradually increases the pressure inside the heating furnace (P0-> P1-> P2-> P3- > P4), and the magnesium melt So as to be supplied to the mold 10 while being moved upward through the inside of the main stocker and the sub-stack. The supplied magnesium magnesium melt is rapidly injected into the entire region of the mold 10 while maintaining the maximum pressure P4, and is then solidified in the mold 10, followed by casting of high-quality magnesium castings.

At this time, the pressurization is continuously maintained until solidification proceeds. Then, when the solidification is completed, the pressurization is released to release the pressurized state so that the pressure inside the first warming-up furnace becomes the initial start pressure (P0), thereby forming a single casting cycle. (Fig. 5A).

However, when one casting cycle is completed and the heating furnace is released from the pressurized state to return to the initial pressure P0, the level of the molten metal in the inside of the stock falls to the initial level. Then, when the molten metal moves up and down the inside of the stoke, the magnesium molten metal is deposited on the inner wall of the stoke, and the magnesium molten metal reacts with oxygen in the atmosphere to form magnesium oxide and reacts with moisture or oxygen in the air to cause ignition or explosion (Fig. 6A shows the molten metal remaining in the stock in a state where the molten metal level is lowered by releasing the pressurized state).

In order to solve this problem, in order to solve this problem, after completing one casting cycle, the pressurized state inside the warming furnace is not completely released but the intermediate pressure? P of the intermediate stage is maintained, It is characterized by the fact that the magnesium molten metal is prevented from contacting the air inside the stoke. That is, when the pressurization is released, it is not released completely but released to the intermediate pressure DELTA P, which is the pressure between the start pressure P0 and the maximum pressure P4, so that the water level of the magnesium melt is held to the upper end of the sub- At this time, it is preferable that the intermediate pressure ([Delta] P) be a pressure between 5 bar and 9 bar. However, the intermediate pressure at this time can be set through trial and error process considering various environments used for casting such as thermal insulation capacity, size of stoke. FIG. 6B shows a state in which the level of the magnesium melt is maintained in the sub-stoke by applying a certain level of pressure without completely releasing the pressurized state even after the product is solidified while forming one casting cycle.

In order to keep the magnesium melt level at the required level continuously as the casting process continues, there is a case where the pressure of the molten metal in the crucible needs to be corrected while the casting process is performed. Therefore, A pressure application program is also provided.

A coil heater (not shown) is wound around the sub-stoke 64 and the outer portion of the sub-stoke is insulated by the refractory. Thus, during the process of injecting the magnesium melt (or during the intermediate pressure process in which the magnesium melt is maintained) ) The heat loss of the molten metal is prevented and the temperature of the molten metal is maintained at about 600 ° C to prevent the molten metal in the sub-stoke from solidifying.

The present invention relates to a method for manufacturing a mold, comprising: a first step of pressurizing a magnesium melt while gradually raising a pressure inside the heat retaining furnace from an initial start pressure (P0) to a maximum pressure (P4) using a pressurizing device; A second step of coagulating the magnesium molten metal in the mold while maintaining the pressure inside the heat retaining furnace at the maximum pressure P4 with the pressurizing device; And a third step of reducing the pressure inside the heating furnace to an intermediate pressure (DELTA P) to maintain the water level of the molten metal in the substock at a constant level after completion of solidification, and completing one casting cycle, DELTA P is maintained at a pressure between the start pressure P0 and the maximum pressure P4 so that the level of the molten metal in the third step is maintained at the level of the molten metal up to the top of the substoke. And a correction step of correcting the value of the intermediate pressure [Delta] P in order to correct a change in the level of the molten metal in the sub-stoke as the casting cycle is repeated, and the intermediate pressure [Delta] Between 5 and 9 bar.

The low-pressure casting technology for a magnesium alloy according to the present invention is characterized in that even if the solidification of the product is completed during the magnesium alloy casting process, the pressure in the heat retaining furnace is not completely released but a certain level of pressure is maintained so that the level of the magnesium- So that oxidation that occurs due to contact with air on the inner surface of the stock can be prevented.

Claims (6)

A melting furnace for dissolving a magnesium ingot to make a magnesium melt; A warming furnace accommodating the magnesium molten metal and supplying the molten magnesium to the mold; And a metal pump for transferring the molten metal from the melting furnace to a warming furnace,
A first step of casting a unit casting product by pressurizing the molten metal of the warming furnace with a metal mold;
A second step of detecting a change (? L) in the level of the molten metal in the warming furnace;
A third step of supplying the molten metal of the melting furnace to the heating furnace by using the metal pump;
And a fourth step of charging and dissolving the magnesium ingot into a melting furnace,
Wherein the first to fourth steps are sequentially repeated, and the pressurized state is continuously maintained in the first to fourth steps. The method according to claim 1,
Wherein the step of casting the unit castings three to five times in the first step is followed by the step of sensing the change in the level of the molten metal in the second step. The method according to claim 1,
Wherein the pressurized state is maintained between the unit casting of the first stage and the casting of the unit casting so that the level of the molten metal is maintained in the inside of the stock. The method according to claim 1,
A main stocker (62) installed in the thermal insulating furnace and into which molten magnesium is injected; A substock (64) connecting the injection port of the main stalk and the mold; And a pressurizing device (40) for pressurizing the molten magnesium contained in the inside of the insulated furnace so as to be supplied to the mold,
In the first step,
A first step of pressurizing the magnesium melt while gradually raising the pressure inside the heat retaining furnace from the initial start pressure P0 to the maximum pressure P4 with the pressurizing device and injecting the molten magnesium into the mold;
And a second step of coagulating the magnesium melt in the mold while maintaining the pressure inside the heat insulating furnace at the maximum pressure P4 with the pressurizing device; And
And a third step of maintaining the water level of the molten metal in the sub-stoke tank at a predetermined level by reducing the pressure inside the heating furnace to an intermediate pressure (DELTA P) after completion of solidification,
Wherein the intermediate pressure? P is a pressure between the start pressure P0 and the maximum pressure P4. The method according to claim 1,
Wherein the level of the molten metal in the step 1-3 is maintained at a level of the molten metal up to the upper end of the sub-stoker. 6. The method according to any one of claims 1 to 5,
Wherein the casting is a road wheel for a vehicle.

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