CN1276276A - Metal mold device, die casting method and die cast product - Google Patents

Abstract

The present invention provides a metal mold device and a magnesium alloy die-casting method using the metal mold device. The metal mold device is a metal mold device suitable for magnesium alloy die-casting or metal injection molding. Set up direct runners from the sprue to each gate, and set the non-gate distance between adjacent gates to be less than 10mm, except in cases where the product design does not allow it. The die-casting method of the metal mold device of the present invention is effective for thin-wall casting, especially for thin-wall casting below 1.5mm or alloy casting containing silicon, rare earth elements, and calcium, especially for thin-wall casting below 1.5mm or silicon-containing casting. , rare earth elements, and calcium alloy casting can effectively and stably obtain high-quality die-casting products without casting wrinkles, surface cracks, poor filling, and sand sticking to metal molds.

Description

Metal mold device, die casting method and die cast product

The present invention relates to a metal mold device suitable for metal injection molding such as die-casting or thixomouldirg (thixomouldirg) manufacturing methods of magnesium alloys, a die-casting method and a die-cast product using the metal mold scheme, and more specifically relates to A metal mold device that can be used in the manufacture of thin-walled cast parts required for the manufacture of housings for home appliances, various container parts for automobiles, etc. By using the die-casting method using the metal mold device, for example, the minimum wall thickness can be realized below 1.5mm Die-casting method and die-casting products of magnesium alloy.

Also, the present invention relates to a die-casting method and die-cast product of a magnesium alloy excellent in room temperature strength and high-temperature strength, and more specifically, relates to a high temperature of about 523K required for weight reduction of automotive engine parts and the like. A die-casting method and a die-cast product of a magnesium alloy also having sufficient strength.

In recent years, the demand for lightweight materials has increased, and resin materials or light metal materials have gradually been used. However, resin materials are generally difficult to reuse and have problems in environmental protection. In response to this problem, metal materials are generally easier to reuse, so they are used as manufacturing materials for housings of home appliances and various container parts for automobiles. Change from resin materials to light metals such as magnesium-based materials or aluminum-based materials. Especially in the trend of lightness, thinness and shortness, lightweight magnesium-based materials that not only have the rigidity of metals, but also have the lowest density among practical light metals are attracting attention. A trend that is attracting attention as a material for automobiles and portable home appliances. In particular, in the casings of portable products such as notebook personal computers, digital cameras, MD players (portable stereo players), and video cameras, products with a wall thickness of 1.5mm or less, especially 1.2mm or less, are required.

In addition, in the automobile industry, due to the increasing awareness of global environmental protection, there is a growing need to increase the fuel consumption of automobiles, so the development of lightweight materials for automobiles is strongly demanded. Magnesium alloys have the lowest density among metal materials currently in use, and are strongly expected to be used as lightweight materials for future automobiles, and demand is expanding. In particular, silicon-added alloys, such as AS41 alloy (Mg-4Al-1Si-0.2Mn), which are suitable for applications such as engine parts that require heat resistance and creep resistance up to about 473K, have been developed since then, and rare earth elements have been added. Alloys, such as AE42 alloy (Mg-4Al-2RE-0.2Mn), and then recently developed, proposed to add calcium alloys (Japanese Patent Laid-Open No. 6-25790 communique), add calcium and rare earth alloys (Japanese Patent Laid-Open Flat 6 -200348 bulletin, JP-P 7-11347 bulletin), it is believed that the use will be expanded.

However, in the die-casting or metal injection molding of magnesium alloys, there are unique problems such as sand sticking, poor filling, hot cracks or shrinkage cracks, casting wrinkles, and shrinkage cavities. In particular, there is a tendency to increase these problems in thin castings expected in recent years, or in the use of alloys containing silicon, rare earth elements, or calcium. The mold device is only a trial method of repeating previous experience and extension, and there is no systematic design guideline for metal mold devices.

The present invention is made in view of the problems of the prior art. The present invention aims to provide a magnesium alloy die-casting and metal injection molding that does not cause sand sticking, poor filling, thermal cracking or shrinkage cracking, casting wrinkles, shrinkage cavities, etc. A metal mold device, a die-casting method and a die-cast product using the metal mold device, and especially a metal mold device for thin-walled casting or using an alloy containing silicon, rare earth elements or calcium, using the metal mold The die-casting method of the device and the die-cast product are the subjects.

The inventors of the present invention have conducted various studies in order to achieve the above-mentioned problems, and as a result, have found that there are several rules regarding the optimization of die devices used in die-casting and metal injection molding of magnesium alloys. In other words, the important points in the die casting and metal injection molding of magnesium alloys are: (1) to make the metal flow smoothly without disturbance, (2) not to reduce the flow rate, and (3) to wait as long as possible in the cavity. (4) do not disturb the flow of each other, (5) should quickly fill the mold cavity, and the metal mold device that realizes these conditions is used, and the injection conditions and/or metal mold conditions are appropriate, and it can be completely It can effectively inhibit sand sticking, poor filling, thermal cracking or shrinkage cracking, casting wrinkles, shrinkage cavities, etc.

That is, the metal mold device of the present invention is a metal mold device suitable for die casting or metal injection molding of a magnesium alloy, and is characterized in that

Set up several gates and set up direct runners from the sprue to each gate, and

The distance of the non-gate portion between adjacent gates is set to 10 mm or less, except for cases where the product design does not allow it.

And the metal mold device of the present invention is a metal mold device suitable for die-casting or metal injection molding of magnesium alloys, and is characterized in that:

Set up several gates and set up direct runners from the sprue to each gate, and

The distance of the non-gate part between adjacent gates is set to be less than 10mm as a necessary requirement except for the case where the product design does not allow it;

Furthermore, the volume of each runner from the sprue to each gate is set to be the same,

The cross-sectional area of each gate is set to be proportional to the volume of the product to be filled from the gate,

maintaining the same or continuously reducing the total cross-sectional area of each runner from the sprue to each gate in the flow direction of the molten metal, and

It is necessary to set the shape of the flow path to R5 or more as much as possible so that the molten metal flow becomes at least one of smooth flow.

The magnesium alloy die-casting method of the present invention is a die-casting method for casting a die-casting product without casting wrinkles, surface cracks, poor filling, and sand sticking to a metal mold from a magnesium alloy, and is characterized in that,

Using the above-mentioned metal mold device,

Keep the melt temperature of the magnesium alloy at 580 to 750°C,

Set the fill rate to the cavity from 1/100 to 10/100 of a second, and

When using a cold-chamber die-casting machine, set the boost pressure after filling to 200 kgf/cm ² or more.

The magnesium alloy die-casting method of the present invention is a die-casting method for casting a die-casting product without casting wrinkles, surface cracks, poor filling, and metal mold sticking sand from a magnesium alloy, and is characterized in that,

Using the above-mentioned metal mold device,

Keep the metal mold temperature at 150 to 350°C,

The surface temperature of the metal mold in the mold cavity where shrinkage cracks are prone to occur on the die-casting casting is lowered by more than 10K compared with the peripheral part,

The air pressure in the metal mold during die casting is set to 100mmHg or less, and

At least one selected from the group consisting of graphite, BN, water glass, mica, silica gel, magnesium hydroxide, and magnesium oxide is used as an additive to the release agent coated on the inner surface of the mold.

Ideally, the magnesium alloy die-casting method of the present invention is a die-casting method for casting a die-casting product from a magnesium alloy without casting wrinkles, surface cracks, poor filling, and sand sticking to the metal mold, and is characterized in that,

Using the above-mentioned metal mold device,

Keep the melt temperature of the magnesium alloy at 580 to 750°C,

Set the filling speed to the cavity from 1/100 to 10/100 of a second,

When using a cold chamber die-casting machine, set the pressurization after filling to 200kgf/cm2 or ^more ,

Keep the metal mold temperature at 150 to 350°C,

The surface temperature of the metal mold in the mold cavity where shrinkage cracks are prone to occur on the die-casting casting is lowered by more than 10K compared with the peripheral part,

The air pressure in the metal mold during die casting is set to 100mmHg or less, and

At least one selected from the group consisting of graphite, BN, water glass, mica, silica gel, magnesium hydroxide, and magnesium oxide is used as an additive to the release agent coated on the inner surface of the mold.

Furthermore, when obtaining a die-cast product of a magnesium alloy excellent in room temperature strength and high-temperature strength, the die-casting method of the magnesium alloy of the present invention uses a magnesium alloy containing

i) 1 to 10% by weight of aluminum,

ii) at least one selected from the group consisting of 0.2 to 5% by weight of rare earth elements, 0.02 to 5% by weight of calcium, and 0.2 to 10% by weight of silicon, and

iii) Magnesium alloys consisting of 1.5% by weight or less of manganese, and the remainder consisting of magnesium and unavoidable impurities.

The magnesium alloy die-casting product of the present invention is a magnesium alloy die-casting product without casting wrinkles, surface cracks, poor filling, and sand sticking to the metal mold, which can be produced by the above-mentioned die-casting method using the above-mentioned metal mold device.

The composition of the magnesium alloy suitable for the die-casting method of the present invention, the metal mold device suitable for die-casting or metal injection molding of magnesium alloy, the die-casting method and the die-cast product using the metal mold device will be described in detail below.

The magnesium alloy that can be cast by the die-casting method of the present invention may be any as long as it is a die-castable magnesium alloy. For example, MD1A, MD1B, MD1D, MD2A, MD2B, MD3A, etc. can be used.

However, for the purpose of reducing the weight of automobile engine parts and the like, magnesium alloy die-casting products with sufficient strength even at the required high temperature of about 523K are used.

i) 1 to 10% by weight of aluminum,

ii) at least one selected from the group consisting of 0.2 to 5% by weight of rare earth elements, 0.02 to 5% by weight of calcium, and 0.2 to 10% by weight of silicon, and

iii) Manganese is less than 1.5% by weight, and a magnesium alloy composed of magnesium and unavoidable impurities is more desirable.

In the die apparatus of the present invention, it is a prerequisite to provide a plurality of gates. In this way, in a metal mold device with several gates, first of all, in order not to disturb the flow rate of the molten metal and the flow of the molten metal, it is necessary to set a direct runner from the sprue to each gate, that is, from the sprue to each gate. The ports must be connected directly with each flow channel respectively. The flow of molten metal in each runner becomes uniform, and at the same time, the cross-sectional area of the gate can be set to suit the shape of the product. More than two gates must be set. However, the final number of gates and the cross-sectional area of each gate It is determined by the size of the product (the amount of molten metal) and the shape of the product, and is regulated by the size of the metal mold, the cost of the metal mold, and the shrinkage rate of the material. However, only for metal molds, it is ideal to make multiple gates and make each gate thinner according to the shape of the product.

As mentioned above, the cross runners and gates set in this way can be filled in the mold cavity without disturbance as much as possible and without inhibiting the flow of molten metal. It is advisable to take some basic design conditions as necessary or ideal. condition. That is, in order to fill the mold cavity without disturbing the flow of molten metal, it is ideal to make the volumes of the runners from the sprue to the gates divided into two or more the same as each other, and make each The cross-sectional area of the gate is designed to be proportional to the volume of the product to be filled from the gate. It is ideal to fill the product with molten metal from each gate.

In order not to reduce the flow rate of the molten metal, it is ideal to keep the total cross-sectional area of each runner from the sprue to the gate at the same level or decrease continuously in the flow direction of the molten metal. Set the shape of the runner as much as possible above R5 so that the molten metal can flow smoothly.

As mentioned above, since the molten metal is quickly filled from the gate to the mold cavity, cold gaps are likely to occur between the gates. Therefore, if the metal mold device of the present invention is used, the adjacent gates must be The distance between the non-gate parts, except for the case where the product design is not allowed, is set to be less than 10mm.

Also, depending on the R of the runner, a vector perpendicular to the gate surface will be generated in the width direction of each gate. Therefore, the velocity of the molten metal in the direction perpendicular to the gate becomes slower at the edge of the gate in the velocity distribution in the width direction of the gate. In order to make the velocity distribution as uniform as possible, for example, it is desired to be within 1 m/s in actual measurement or calculation of molten metal flow. As the velocity difference in this velocity distribution becomes closer to zero, since the aforementioned cold shut between the gates is likely to occur, the tendency of the flow of the molten metal at the gate end must be fully studied.

Among the injection conditions for carrying out the die-casting method of the present invention using the above-mentioned metal mold apparatus, there is the temperature of the molten metal. When the temperature of the molten metal in the melting furnace is lower than 580° C., the fluidity decreases, and problems arise in the fillability to the mold. On the other hand, if it exceeds 750° C., the risk of ignition increases when the molten metal is held, and the shrinkage rate from the molten metal to solidification increases, so thermal cracking or shrinkage cracking tends to occur. Therefore, the melt temperature of the alloy should be kept at 580 to 750°C, ideally at 650 to 710°C.

Among the injection conditions of the die casting method of the present invention, there is a filling speed into the cavity. Generally, the solidification latent heat of magnesium alloy is small, so it is recommended to increase the injection speed. Since the magnesium alloy is prone to cracks due to the generation of compounds, especially in the relatively slow-solidified grain part, casting pressure must be applied to the entire area of the casting. Therefore, the balance between the casting speed and the cooling from the metal mold must be considered. According to experience, the filling speed into the metal mold cavity is set at 1/100 to 10/100 seconds, ideally 1/100 to 5/100 seconds is a necessary condition. In order to meet this condition, the injection speed is set to be 2m/s or more, ideally 3.5m/s or more, or the gate speed is set to be 30m/s or more, preferably 50m/s or more. When the filling rate into the cavity of the metal mold is slower than 10/100 seconds, problems arise in either direction of filling property (poor filling) or thermal cracking property.

When using a cold-chamber die-casting machine, the injection conditions of the die-casting method of the present invention include pressurization after filling. Immediately after filling into the cavity of the metal mold, pressurization must be applied to prevent poor filling and suppress thermal cracking and shrinkage cracking during solidification or cooling. The pressurized condition at this time is 200kgf/cm ² or more, preferably 400kg/cm ² or more. If such a pressurized pressure is not applied, poor filling occurs, or cracks occur in all regions of the casting in which the wall thickness changes.

The above die-casting injection conditions are related to each other, and without any one of these conditions, a sound thin-walled casting of magnesium alloy cannot be obtained. On the contrary, it is carried out by using the above-mentioned metal mold device, by satisfying the three injection conditions, namely,

Keep the molten metal temperature of the magnesium alloy at 580 to 750°C,

Set the fill rate to the cavity from 1/100 to 10/100 of a second, and

When using a cold-chamber die-casting machine, set the pressurization after filling to 200kgf/cm2 ^or more, and you can cast magnesium alloy die-castings without casting wrinkles, surface cracks, poor filling, and sand sticking to the metal mold.

Among the mold conditions for carrying out the die casting method of the present invention using the above-mentioned mold apparatus is the mold temperature. When the mold temperature is lower than 150° C., the fillability of the molten metal is hindered empirically, or even if the fillability is possible, problems are caused in surface properties such as casting wrinkles. In addition, when the temperature exceeds 350°C, shrinkage cracking or thermal cracking tends to occur due to the delayed solidification rate. Therefore, the temperature of the metal mold is kept at 150 to 350°C, preferably at 180 to 280°C.

Partial cooling is included in the mold conditions of the die casting method of the present invention. Depending on the shape of the casting, there are parts where cracks are likely to occur in the shape such as the abrupt thickness change part. In such cases, in addition to the above-mentioned overall mold temperature control, local temperature control is also necessary. In order to control the temperature, it is possible to install passages for refrigerants in necessary parts of the metal mold, and to flow refrigerants such as water, oil, and air in the passages for local cooling, or to pass through the passages when the molds are opened. A method of locally cooling by spraying a release agent or air, etc. In short, the surface temperature of the part of the metal mold that needs local cooling must be cooled by 10K or more than the surrounding surface temperature, and ideally it should be cooled by 20K or more, so that the parts that are prone to shrinkage cracks are preferentially solidified to prevent shrinkage cracks.

In the die conditions of the die casting method of the present invention, there is decompression in the die. In order to help the molten metal to fill the mold cavity, and to prevent the disturbance of the flow of the molten metal caused by the air in the metal mold, decompression in the metal mold is necessary. In order to achieve this purpose, the air pressure in the mold must be set to 100 mmHg or less, preferably 50 mmHg or less, during injection of the molten metal.

In the die conditions of the die casting method of the present invention, there is a mold release agent coated on the inner surface of the die. Regarding the cooling conditions for solidification, not only the temperature conditions of the metal mold, but also the heat preservation effect of the release agent can delay the solidification and make the casting pressure work. In order to achieve this purpose, it is effective to use at least one selected from the group consisting of graphite, BN, water glass, mica, silica gel, magnesium hydroxide, and magnesium oxide as an additive for the release agent.

The above mold conditions are related to each other, but the mold temperature is particularly important. When there is no mold cavity where shrinkage cracks are likely to occur on the die-casting casting, local cooling is not required. In this case, local cooling can be eliminated from the constitutional requirements of the present invention. Depending on the shape of the mold cavity and the shape of the die-casting product, although the pressure reduction in the metal mold and the additive of the release agent are not necessarily necessary conditions, it is more desirable to use these conditions together to obtain better results.

In the present invention, it is carried out by adopting the above-mentioned metal mold device, by satisfying these four kinds of metal mold conditions, namely

Keep the metal mold temperature at 150 to 350°C,

The surface temperature of the metal mold in the mold cavity where shrinkage cracks are likely to occur on the die-casting casting is lowered by more than 10K compared with the peripheral part,

The air pressure in the metal mold during die casting is set to 100mmHg or less, and

As an additive to the release agent coated on the inner surface of the metal mold, at least one selected from the group consisting of graphite, BN, water glass, mica, silica gel, magnesium hydroxide and magnesium oxide can be used to cast without casting Magnesium alloy die castings with wrinkles, surface cracks, poor filling, and metal mold sticking sand.

The metal mold device of the present invention described above, and the die-casting method using the metal mold device are effective for thin-wall casting, especially thin-wall casting of 1.5 mm or less or casting of alloys containing silicon, rare earth elements, and calcium. , Die-casting products without casting wrinkles, surface cracks, poor filling, and sand sticking to metal molds can be obtained.

Hereinafter, the present invention will be specifically described based on examples and comparative examples.

Example 1 and Comparative Examples 1 to 6

The metal mold device is adopted:

Set four gates, and set up direct runners from the sprue to each gate,

Set the non-gate distance between adjacent gates to 5mm,

Set the volume of each runner from the sprue to each gate to be the same,

The cross-sectional area of each gate is set to be proportional to the volume of the product that should be filled from the gate,

The total cross-sectional area of each runner from the sprue to each gate is kept the same in the flow direction of the molten metal,

Set the shape of the runner to R15 or higher.

Using the above-mentioned metal mold device, using AZ91 (Mg-9Al-0.7Zn-0.2Mn) alloy, the cold chamber die-casting machine uses a 650-ton machine made by Ube Corporation of Japan, and the temperature of the alloy melt is set at 680 ° C. The filling speed of the cavity is set to 5/100 second, the boost pressure after filling is set to 300kgf/cm ² , the mold temperature is set to 250°C, and the air pressure in the mold during die casting is set to 100mmHg, and a talc-based mold release agent was coated on the inner surface of the metal mold, and the casting of a trial product of an A4 size notebook personal computer case (product thickness 0.8mm) was implemented. Casting results are shown in Table 1. Comparative Examples 1 to 6 were carried out with the mold apparatus changed as shown in Table 1 (the mold apparatus not described in Table 1 was kept unchanged as above). These casting results are shown in Table 1.

Table 1 Changing metal mold device casting result judge Example 1 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Comparative Example 6 Example 2 The distance between one gate of the standard gate is 15mm. Change the volume of one runner to 2 times. Set the cross-sectional area of one gate to 1.5 times. Set the total cross-sectional area of the runner to 1.5 times in the runner. Set some criteria for R3 Good filling Poor filling Comparative examples 3 to 6 are slightly poor in all surface properties, and the residual cold partition is good ○××△ to ○△ to ○△ to ○△ to ○○

Example 2

Casting was performed in the same manner as in Example 1 except that the temperature of the molten metal was set to 610° C. using a hot-chamber die-casting machine, and pressurization after filling was not performed. The results of the casting are shown in Table 1. Example 3

Adopt the metal mold device that adopts in embodiment 1, use the high Mg-5Al-3Ca-0.2Mn alloy of thermal cracking sensitivity, Mg-5Al-4RE-0.2Mn-0.05Ca alloy, Mg-5Al-2Si-0.5RE -0.2Mn alloy, or Mg-9Al-2Ca-2RE-1Si-0.2Mn alloy, the cold chamber die-casting machine uses a 650-ton machine made by Ube Corporation of Japan, and the temperature of the alloy melt is set at 700 ° C, and the mold cavity The filling speed is set to 5/100 seconds, the boost pressure after filling is set to 500kgf/cm ² , the mold temperature is set to 200°C, and the air pressure in the mold during die casting is set to 40mmHg , and with the size of 300mm × 300mm × 180mm imitating the size of auto parts, the casting of a box-type trial product with a wall thickness of 3mm is implemented. No hot cracking was seen in all four die castings. Example 4

In order to make the die-cast product into a shape that is prone to shrinkage cracking, a portion where the wall thickness is changed from 300 mm to 10 mm is provided at the four corners of the box-shaped trial product in Example 3. Using the Mg-5Al-4Ca-1RE-0.2Mn alloy, casting a trial product of this shape under the same conditions as in Example 3 resulted in shrinkage cracks occurring at a probability of about 10% at the edge of the wall thickness change portion, and after casting Sand sticking occurs every 100 to 300 shots at the part where the mouth enters the die-casting product.

Therefore, as a countermeasure against shrinkage cracking, the occurrence of shrinkage cracking can be suppressed when the mold part of the wall thickness changing part is cooled to 230°C (the temperature difference from the surrounding mold temperature is 20K).

As a countermeasure against sand sticking, when casting is performed by applying a release agent added with BN to the above-mentioned part where sand sticking occurs, the occurrence of sand sticking can be suppressed. In addition, equivalent effects can be obtained when graphite, water glass, mica, silica gel, magnesium hydroxide, or magnesium oxide is used instead of BN.

The die casting method using the metal mold device of the present invention is effective in thin-wall casting, especially thin-wall casting of 1.5mm or less or alloy casting containing silicon, rare earth elements, and calcium, and can obtain high-quality and stable Die-casting products with casting wrinkles, surface cracks, poor filling, and metal mold sticking sand.

Claims (19)

1. A metal mold device, which is a metal mold device suitable for die casting or metal injection molding of magnesium alloys, is characterized in that, Set up several gates and set up direct runners from the sprue to each gate, and The distance of the non-gate portion between adjacent gates is set to 10 mm or less, except for cases where the product design does not allow it. 2. The metal mold device according to claim 1, which is suitable for die casting or metal injection molding of magnesium alloys, characterized in that, Set up several gates and set up direct runners from the sprue to each gate, and The distance of the non-gate part between adjacent gates is set to be less than 10mm, except for the case where the product design does not allow it, as a necessary requirement; Furthermore, the volume of each runner from the sprue to each gate is set to be the same, The cross-sectional area of each gate is set to be proportional to the volume of the product that should be filled from the gate, maintaining the same or continuously reducing the total cross-sectional area of each runner from the sprue to each gate in the flow direction of the molten metal, and At least one of the necessary conditions is to set the shape of the flow channel to be R5 or higher as much as possible so that the molten metal flow becomes smooth. 3. The metal mold device according to claim 1, characterized in that, in the measurement or calculation of the molten metal flow, the velocity difference in the gate width direction is set to be below 1 m/s for the molten metal from The flow velocity from the gate to the cavity. 4. The metal mold device according to claim 2, characterized in that, in the measurement or calculation of the molten metal flow, the velocity difference in the gate width direction is set to be 1 m/s or less for the molten metal from The flow velocity from the gate to the cavity. 5. A die-casting method of a magnesium alloy, which is a method for casting a die-cast product without casting wrinkles, surface cracks, poor filling, and sand sticking to a metal mold from a magnesium alloy, characterized in that, Adopt the metal mold device described in claim 1, 2, 3 or 4, Keep the melt temperature of the magnesium alloy at 580 to 750°C, Set the fill rate to the cavity from 1/100 to 10/100 of a second, and When using a cold-chamber die-casting machine, set the boost pressure after filling to 200 kgf/cm ² or more. 6. A die-casting method for a magnesium alloy, which is a method for casting a die-cast product without casting wrinkles, surface cracks, poor filling, and sand sticking to a metal mold from a magnesium alloy, characterized in that, Adopt the metal mold device described in claim 1, 2, 3 or 4, Keep the metal mold temperature at 150 to 350°C, The surface temperature of the metal mold in the mold cavity where shrinkage cracks are prone to occur on the die-casting casting is lowered by more than 10K compared with the peripheral part, The air pressure in the metal mold during die casting is set to 100mmHg or less, and At least one selected from the group consisting of graphite, BN, water glass, mica, silica gel, magnesium hydroxide, and magnesium oxide is used as an additive to the release agent coated on the inner surface of the metal mold. 7. The die-casting method according to claim 6, which is a method for casting a die-cast product without casting wrinkles, surface cracks, poor filling, and sand sticking in metal molds from magnesium alloy casting, characterized in that, Adopt the metal mold device described in claim 1, 2, 3 or 4, Keep the melt temperature of the magnesium alloy at 580 to 750°C, Set the filling speed to the cavity from 1/100 to 10/100 of a second, When using a cold chamber die-casting machine, set the pressurization after filling to 200kgf/cm2 or ^more , Keep the metal mold temperature at 150 to 350°C, The surface temperature of the metal mold in the mold cavity where shrinkage cracks are prone to occur on the die-casting casting is lowered by more than 10K compared with the peripheral part, The air pressure in the metal mold during die casting is set to 100mmHg or less, and At least one selected from the group consisting of graphite, BN, water glass, mica, silica gel, magnesium hydroxide, and magnesium oxide is used as an additive to the release agent coated on the inner surface of the metal mold. 8. The die-casting method according to claim 5, characterized in that die-casting products having a wall thickness of 1.5 mm or less are cast. 9. The die-casting method according to claim 6, wherein a die-cast product having a wall thickness of 1.5 mm or less is cast. 10. The die-casting method according to claim 7, characterized in that die-casting products having a wall thickness of 1.5 mm or less are cast. 11. The die-casting method according to claim 5, characterized in that the magnesium alloy contains i) 1 to 10% by weight of aluminum, ii) at least one selected from the group consisting of 0.2 to 5% by weight of rare earth elements, 0.02 to 5% by weight of calcium, and 0.2 to 10% by weight of silicon, and iii) less than 1.5% by weight of manganese, The rest are magnesium alloys composed of magnesium and unavoidable impurities. 12. The die-casting method according to claim 6, characterized in that the magnesium alloy contains i) 1 to 10% by weight of aluminum, ii) at least one selected from the group consisting of 0.2 to 5% by weight of rare earth elements, 0.02 to 5% by weight of calcium, and 0.2 to 10% by weight of silicon, and iii) less than 1.5% by weight of manganese, The rest are magnesium alloys composed of magnesium and unavoidable impurities. 13. The die-casting method according to claim 7, characterized in that the magnesium alloy contains i) Aluminum 1 to 10% by weight, ii) at least one selected from the group consisting of 0.2 to 5% by weight of rare earth elements, 0.02 to 5% by weight of calcium, and 0.2 to 10% by weight of silicon, and iii) less than 1.5% by weight of manganese, The rest are magnesium alloys composed of magnesium and unavoidable impurities. 14. The die-casting method according to claim 8, characterized in that the magnesium alloy contains i) Aluminum 1 to 10% by weight, ii) at least one selected from the group consisting of 0.2 to 5% by weight of rare earth elements, 0.02 to 5% by weight of calcium, and 0.2 to 10% by weight of silicon, and iii) less than 1.5% by weight of manganese, The rest are magnesium alloys composed of magnesium and unavoidable impurities. 15. A magnesium alloy die-casting product that can be manufactured by the die-casting method according to claim 5 without casting wrinkles, surface cracks, poor filling, and metal mold sticking sand. 16. A magnesium alloy die-casting product that can be manufactured by the die-casting method according to claim 6 without casting wrinkles, surface cracks, poor filling, and metal mold sticking sand. 17. A magnesium alloy die-casting product that can be manufactured by the die-casting method according to claim 7 without casting wrinkles, surface cracks, poor filling, and metal mold sticking sand. 18. A magnesium alloy die-casting product that can be manufactured by the die-casting method according to claim 8 without casting wrinkles, surface cracks, poor filling, and metal mold sticking sand. 19. A magnesium alloy die-casting product that can be manufactured by the die-casting method according to claim 11 without casting wrinkles, surface cracks, poor filling, and metal mold sticking sand.