JP2003126956A - Casting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a casting method which realizes the improvement of yield and life of a mold by improving the dimensional accuracy and making a metallic structure soundness in a casting method using a cooled mold. SOLUTION: This casting method for pouring molten metal into the mold has a process for previously cooling the mold at a normal temperature or less in a state that moisture is not deposited to the inner face of a cavity of the mold, and a process for pouring the molten metal.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for pouring molten metal into a mold, and more particularly to a casting method for pouring molten metal into a cooled mold.

[0002]

2. Description of the Related Art A die casting method of pouring molten metal into a die is widely used for improving dimensional accuracy and miniaturizing a metal structure.

In this die casting method, the production cost of the die is high, so that the life of the die is lengthened, and the mass production is not sufficient for the economical production. The mold life is indispensable to be heat resistant and resistant to thermal fatigue due to the heat generated by pouring the mold.

Therefore, in a die casting method which is widely used at present, a heat-resistant die is used to keep the die at a temperature of 150 ° C. and the inside of the die is cooled to increase the cooling rate of the molten metal. A cooling pipe is penetrated into the mold, and cooling water is passed through the cooling pipe to refine the metal structure.

However, in recent years, further improvement in dimensional accuracy and improvement in yield by improving the soundness of the metal structure have been demanded. Moreover, the mold life is not sufficient.

[0006]

The present invention has been made in view of the above problems. And the purpose of the present invention is to
It is an object of the present invention to provide a casting method using a cooled mold, which achieves further improvement in dimensional accuracy and improvement in yield and mold life due to the soundness of the metal structure.

[0007]

In order to achieve the above object, the casting method in the present invention is a casting method in which molten metal is poured into a cooled mold, and moisture is not attached to the inner surface of the cavity of the mold. The method is characterized by including a step of previously cooling the mold to a temperature equal to or lower than room temperature in the state, and a step of pouring molten metal.

[0008] The present invention has led to the present invention as a result of intensive studies, paying attention to the soundness of the metal structure because there are many internal defects such as shrinkage cavities and pinholes in die casting. It is a thing. That is, the present invention focuses on that in the conventional mold casting method, the mold is cooled by using the heat-resistant mold during pouring to increase the cooling rate of the molten metal, and the metal structure is refined. The present invention has been accomplished in consideration of the heat resistance of the mold while further increasing the cooling rate.

According to the present invention, the heat resistance and life of the mold are extended by pre-cooling to a temperature lower than room temperature, which is lower than that of the conventional mold. Further, by pouring the molten metal into the cooled mold, the cooling rate of the molten metal can be further increased to achieve a finer metal structure. Furthermore, since the molten metal is poured in a state in which moisture does not adhere to the inner surface of the cavity of the mold, casting defects such as pinholes can be eliminated.

In order to achieve the above object, the casting method in the present invention is a casting method in which molten metal is poured into a cooled mold, and the mold is preliminarily prepared without adhering water to the inner surface of the mold cavity. A casting method comprising a step of cooling to a temperature lower than room temperature and a step of pouring molten metal, wherein the mold is a split mold, and at least one of them is a mold.

According to the present invention, the solidification of the molten metal rapidly progresses from the surface in contact with the mold surface, and the molten metal in contact with a mold other than the mold having poor thermal conductivity, for example, a refractory mold, Since the cast product is obtained from the solidified layer that has progressed from the former before completely solidifying, the product has no defects such as shrinkage cavities and pinholes inside. If the wall thickness of the casting is too thick, this effect is reduced, and the wall thickness is preferably 3 m.
The most effect can be expected when m is 10 mm, more preferably about 5 mm to 6 mm.

Further, in order to achieve the above-mentioned object, the casting method in the present invention is a casting method of pouring molten metal into a mold, wherein the mold is preliminarily kept at room temperature or below without adhering water to the inner surface of the mold cavity. And a step of pouring molten metal in a state where the mold is cooled using a cooling means having a temperature of room temperature or lower. According to the present invention, a precooled mold is used, and the molten metal is poured into the mold cavity while further cooling the mold. For this reason, the heat of the mold surface in contact with the molten metal rapidly transfers to the inside of the mold and to the outside through the mold, and this heat is also rapidly taken out of the mold by the cooling effect. Therefore, it becomes possible to solidify the molten metal more rapidly. Note that this method is particularly effective when a cast product having a large wall thickness is to be obtained.

Further, in order to achieve the above object, the casting method according to the present invention is the casting method according to any one of claims 1 to 3, wherein the step of cooling the mold comprises:
It is characterized in that the mold surface is cooled by a gas containing no water. According to the present invention, when the molten metal is poured into the mold cavity, the mold surface in the cavity is cooled by the gas containing no water, so that the state in which no water is attached can be easily ensured.

In order to achieve the above object, the casting method according to the present invention is the casting method according to claim 4, wherein after the whole or a part of the mold is placed in the chamber,
It is characterized by being cooled by a water-free gas introduced into the chamber. According to the present invention, efficient cooling can be secured.

Further, in order to achieve the above object, the casting method according to the present invention is the casting method according to any one of claims 1 to 3, wherein the step of cooling the mold is performed by drilling the mold. It is characterized in that it is cooled by the gas or liquid introduced into the cooling pipe. According to the present invention, it is efficient because it can be cooled using a refrigerant.

In order to achieve the above object, the casting method according to the present invention is the casting method according to claim 6, wherein the step of cooling the mold is introduced into a cooling pipe provided in the mold. It is characterized in that it is cooled by a gas or a liquid, and further cooled by a gas containing no water from the mold surface. According to the present invention, cooling can be efficiently performed from both the surface of the mold and the inside of the mold.

Further, in order to achieve the above object, the casting method according to the present invention is the casting method according to any one of claims 1 to 7, wherein the step of pouring the molten metal is performed by applying a vacuum to the molten metal. It is characterized by pouring by. Further, the vacuum action is performed at least from below the mold. According to the present invention, smooth and rapid pouring is possible.

Further, in order to achieve the above-mentioned object, the casting method according to the present invention is the casting method according to any one of claims 1 to 9, wherein a state in which moisture is not adhered to the inner surface of the cavity of the mold is It is characterized by being made by dry air. Since dry air is easily available at low cost, an economical casting method can be secured.

Further, in order to achieve the above-mentioned object, the casting method according to the present invention comprises:
In the casting method according to the item 1, the temperature near the mold cavity is measured at least during the step of pouring the molten metal, and the molten metal is poured corresponding to this temperature. According to the present invention, for example, the temperature is measured in order to secure a state in which moisture does not adhere to the inner surface of the cavity or to estimate the melting temperature. If necessary, the temperature of the gas containing no water and the temperature of the refrigerant are measured.

In order to achieve the above object, the casting method of the present invention is a casting method in which molten metal is poured into a cooled mold, and the mold is preliminarily cooled to room temperature without adhering moisture to the inner surface of the mold cavity. Cooling the mold surface to at least the following temperature with at least dry air;
And a step of pouring the molten metal in a state of being cooled by using a cooling unit having a temperature of 0 ° C. or less.
Here, cooling with dry air in advance is to easily secure a state in which moisture does not adhere to the inner surface of the cavity. Further, the reason why the mold is cooled by using a cooling means having a temperature of −10 ° C. or lower is to increase the cooling rate of the molten metal by further cooling.

In order to achieve the above object, the casting method in the present invention is a casting method in which molten metal is poured into a cooled mold, and the mold is preliminarily prepared in a state in which moisture does not adhere to the inner surface of the mold cavity. Cooling the mold surface to a temperature equal to or lower than room temperature with at least dry air;
And a step of pouring the molten metal by a vacuum action performed from at least a lower part of the mold in a state of being cooled by using a cooling means having a temperature of 0 ° C. or less. Here, the vacuum is used in order to speed up the pouring and to easily secure a state in which moisture does not adhere to the inner surface of the cavity.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION Here, in the present invention, the term “mold” refers to a mold (divided mold) formed by combining upper and lower or left and right half molds. It is distinguished from the integral type such as the lost wax type. Various metal molds and ceramic molds are used as the mold. As various metal molds, cast iron,
Steel, copper alloy, etc. are selected according to the material of the molten metal and the like. Further, one of the molds may be a mold and the other may be a ceramics mold. In addition, a mold is applied to the mold as needed. The molten metal is a metal obtained by melting various metals or alloy metals. The material does not matter. Moreover, the melting method does not matter. Any method such as high frequency melting, low frequency melting, and electron beam may be used. Pouring means pouring into a mold. The method does not matter. It does not matter whether the tilting tapping is performed by tilting the ladle or bottom tapping is performed from the bottom of the furnace.

In the present invention, the state in which moisture does not adhere to the inner surface of the cavity of the mold means a state in which no crack is generated during pouring. When the Kirai phenomenon occurs, the molten metal is scattered and not only a sound casting cannot be obtained, but also
It will be extremely dangerous. In the present invention, various states in which moisture is prevented from adhering to the inner surface of the cavity of the mold are secured, but the method is not limited. For example, when the mold is cooled to a temperature equal to or lower than room temperature in advance, the temperature may not be lowered to a low temperature in advance. Also, it is possible to cool with a gas that does not contain moisture, to cool with dry air, to prevent moisture from becoming a frost state by using a pressure difference, or to cool the mold atmosphere with only cooling nitrogen, the inner surface of the cavity of the mold. It is also to prevent water from adhering to. further,
It is for this reason that various temperatures such as the mold cavity and the ambient temperature are measured as necessary.

In the present invention, the reason why the mold is preliminarily cooled to room temperature or lower is to increase the cooling rate of the molten metal. Here, the normal temperature refers to 15 ° C. to 25 ° C. in which work is usually performed in a factory. The temperature equal to or lower than room temperature preferably means a temperature lower than 5 ° C and higher than -100 ° C.
More preferably, the temperature on the lower side refers to a temperature higher than -50 ° C, more preferably lower than -10 ° C and higher than -20 ° C. First, temperatures below 5 ° C and above -100 ° C are preferred. The reason why the temperature is lower than 5 ° C. is that the difference from the room temperature is clear and the temperature can be easily achieved in a refrigerator or the like. A temperature higher than -100 ° C is preferable because it takes time to lower the temperature of the mold to a temperature of -100 ° C or lower. Further, the life of the mold is shortened due to thermal fatigue due to a large temperature difference from the molten metal. The ambient temperature in which the mold is placed is also important. This is because if the ambient temperature is high and the mold is low, dew easily forms on the mold.

The moisture-free gas introduced into the chamber refers to dry air and an inert gas such as nitrogen. By measuring the humidity and controlling it, a gas containing no water can be surely secured.

In the step of pouring the molten metal in the step of pouring the molten metal by the vacuum action, it means that the mold side is evacuated and the molten metal is drawn and poured. For this,
It is also possible to make the mold breathable and suck it. The fact that the vacuum action is performed at least from below the mold is meant to include the vacuum action from the side of the mold. In order to obtain the dry air in the present invention, the air may be previously heated with a heater or the like.

To measure at least the temperature in the vicinity of the mold cavity means the temperature in the vicinity of the mold cavity, the ambient temperature, the temperature of the cooling pipe, and the like. The molten metal is poured in correspondence with this temperature in order to estimate the temperature of the mold and the molten metal temperature and smoothly pour the molten metal. For example, the rate of injection of molten metal into the mold cavity can be adjusted according to a preset temperature rise pattern.

[0028]

Embodiment 1 The invention will be described below with reference to the drawings. Figure 1
[Fig. 3] is a diagram for explaining the outline of the casting apparatus of the embodiment. Figure 1
In, the mold 1 is composed of half molds 1a and 1b, and an example in which a copper alloy is used as the material will be described. Copper alloy has a high thermal conductivity and can increase the cooling rate during pouring. The thermal conductivity is 0.84 W / c
It is preferably m.degree. C. or higher. A cooling pipe 2 in which a refrigerant circulates is provided inside the mold 1 and is connected to a refrigerant supply device 3. The mold 1 is surrounded by the heat insulating material 4. Furthermore, the upper part of the mold 1 and the heat insulating material 4 is
It is contained in the first chamber 5. Further, the first chamber 5 is provided with an introduction pipe 5a for introducing a gas containing no water, an exhaust pipe 5b for discharging a gas containing no water, and an atmosphere cooling circulation device 6. The atmosphere cooling / circulating device 6 may be connected in series with an air circulating device separately from the atmosphere cooling device. Further, another second chamber 7 is provided below the first chamber 5, and one chamber 7 a of the second chamber 7 is movable and is connected to a vacuum pump 8. As a result, the mold 1 and the cavity C in the second chamber 7 can be evacuated. On the other hand, a metal melting device 9 is provided on the upper side inside the first chamber 5, and the metal can be melted and poured into the mold 1. In the present invention, an aluminum alloy is used. A movable seal 10 is provided between the first chamber 5 and the second chamber 7. A movable heat insulating material 11 is provided between the mold 1 and the melting device 9.

The operation of the casting apparatus of the present invention constructed as above will be described below. First, in the first step, the metal melting device 9, the movable seal 10, and the movable heat insulating material 11 are placed at predetermined positions in the first chamber 5 and the second chamber 7.

Then, as the second step, the operation of the atmosphere cooling / circulating device 6 is started. Here, the temperature is not so low that the temperature is 5 ° C. and the air is cooled with dry air as a gas containing no water. As the third step, the refrigerant supply device 3 is started to operate.
This refrigerant is the refrigerant supply device 3 that uses liquid nitrogen having a temperature of -20 ° C. In this third step, the mold 1 is -20 ° C,
The second chamber 7 is set to -20 ° C.

Then, as the fourth step, the melting apparatus 9 is operated to prepare molten metal. Further, as the fifth step, the vacuum pump 8 is operated to reduce the pressure in the second chamber 7.

Then, as a sixth step, the movable heat insulating material 11
Is moved so that the melting device 9 is located right above the movable seal 9. At this stage, the melting space 9 is formed by the melting device 9 and the movable seal 10.

After that, as a seventh step, the movable seal 9 is moved to reduce the pressure in the closed space 12, and immediately after that, the molten metal is poured from the bottom of the melting apparatus 9 to the bottom to form the cavity of the mold 1. After being poured into C, the casting was taken out of the mold 1. This casting had a fine structure because of its high cooling rate.

The above steps 2 to 5 do not necessarily have to be in the order of these steps. That is, the order of cooling the first chamber 5, cooling the second chamber 7 and the mold 1, preparing molten metal, and vacuumizing the second chamber 7 does not matter.

The pressure reduction of the second chamber 7 in the fifth step is not always necessary. Furthermore, a method for ensuring a state in which moisture does not adhere to the inner surface of the cavity C, a temperature for preliminarily cooling the mold, a method for pouring molten metal, a type of gas containing no water, a location for measuring the temperature near the mold cavity C, etc. Can adopt the various methods shown in the embodiments of the present invention. Further, even when the first chamber 5 is depressurized and the second chamber 7 is further depressurized, the molten metal can be poured by the vacuum action performed from below the mold 1.

[0036]

Second Embodiment The invention will be described below with reference to the drawings. Figure 2
[Fig. 3] is a diagram for explaining the outline of the casting apparatus of the embodiment. Figure 2
In, the die 101 is a half die 101a, 101b.
The guide G allows the opening and closing. As the material of the mold 101, an example in which a copper alloy is used as in Example 1 will be described. A cooling pipe 102 through which a refrigerant circulates is provided inside the mold 101, and the cooling device 102 is provided.
It is connected to 3. Further, below the first chamber 105, it is connected to a vacuum pump 108. As a result, the inside of the first chamber 105 can be evacuated. A separately provided vacuum pump 108 is connected to the lower side of the mold 101 so as to be suckable. On the other hand, a metal pouring device 109 is provided on the upper side inside the first chamber 105, and the metal can be melted by a melting device (not shown) and poured into the mold 101. In the present invention, a zinc alloy is used.

The operation of the casting apparatus of the present invention constructed as above will be described below.

First, as the first step, the operation of the atmosphere cooling circulation device 106 is started. Here, the temperature is not very low and the gas nitrogen is cooled at −15 ° C. Then, as a second step, the refrigerant supply device 103 is started to operate. This refrigerant is a refrigerant supply device 10 that uses liquid nitrogen having a temperature of -30 ° C.
It is 3. In the second step, the mold 1 was set to -30 ° C.

Then, as a third step, the crucible type pouring section made of graphite and a pouring apparatus 109 made of a tribe L, which can maintain a molten state by an unillustrated energizing coil, are operated, and further, as a fourth step, a vacuum pump. The first chamber 105 is depressurized by operating 108.

Then, as a fifth step, the pouring device 109
The molten metal was held in the crucible type pouring part of the pouring device 109 via the tribe L of No. Then, by sucking from below the cavity C of the mold 101 with the vacuum pump 108a, bottom pouring is performed from the bottom of the crucible mold pouring part, and the mold 101
Then, the casting was taken out of the mold 101. This casting had a fine structure because of its high cooling rate.

The cavity C of the mold 101 does not need to use vacuum from the bottom of the mold 101. Further, the weight of the molten metal to be poured is measured in advance by a weight scale (not shown), and is 10 times the weight of the molten metal when the cavity C is filled.
It is adjusted within 1% to 105%. This improves the yield.

[0042]

As is apparent from the above description, the casting method according to the present invention is a casting method of pouring molten metal into a mold, in which water is not attached to the inner surface of the cavity of the mold. Since it has a step of cooling the mold to a temperature below room temperature in advance and a step of pouring molten metal, the heat resistance of the mold can be improved by pre-cooling to a temperature below room temperature, which is a lower temperature than the conventional mold. And extend the life. Further, by pouring the molten metal into the cooled mold, the cooling rate of the molten metal can be further increased to achieve a finer metal structure. Further, since the molten metal is poured in a state in which water does not adhere to the inner surface of the cavity of the mold, casting defects such as pinholes can be eliminated. Further, when a vacuum is used for the pouring, the pouring of the molten metal is easy and the flow of the molten metal is easy, and it is possible to easily secure a state in which moisture does not adhere to the cavity, so that casting defects can be eliminated. As described above, the effect on the casting industry is remarkable.

[Brief description of drawings]

FIG. 1 is an outline of a casting apparatus for carrying out the present invention.

FIG. 2 is an outline of another casting apparatus for carrying out the present invention.

[Explanation of symbols]

1,101 mold 2,102 cooling pipe 5, 105 First chamber 7 Second chamber C cavity

Claims (13)

[Claims] 1. A casting method for pouring molten metal into a mold, which comprises pre-cooling the mold to a temperature equal to or lower than room temperature without adhering water to the inner surface of the cavity of the mold, and pouring molten metal. And a casting method. 2. A casting method in which molten metal is poured into a mold in which at least one of the molds is a split mold and a mold is a mold, wherein the mold is preliminarily prepared without adhering water to the inner surface of the mold cavity. A casting method comprising a step of cooling to a temperature equal to or lower than room temperature and a step of pouring molten metal. 3. A casting method for pouring molten metal into a mold, which comprises cooling the mold to a temperature below room temperature in advance without adhering moisture to the inner surface of the cavity of the mold, and cooling the mold to a temperature below room temperature. And a step of pouring the molten metal in a cooled state using a cooling means. 4. The casting method according to claim 1, wherein the step of cooling the mold is performed by cooling the mold surface with a gas containing no water. 5. The whole or a part of the mold is placed in a chamber and then cooled by a gas containing no water introduced into the chamber.
The casting method described in. 6. The casting method according to claim 1, wherein the step of cooling the mold is cooled by a gas or a liquid introduced into a cooling pipe provided in the mold. . 7. The mold cooling step is characterized in that the mold is cooled by a gas or a liquid introduced into a cooling pipe formed in the mold, and further cooled by a gas containing no water from the mold surface. The casting method according to any one of claims 1 to 3. 8. The casting method according to claim 1, wherein the step of pouring the molten metal pours the molten metal by a vacuum action. 9. The casting method according to claim 8, wherein the vacuum action is performed at least from below the mold. 10. The casting method according to claim 1, wherein the state where moisture is not attached to the inner surface of the cavity of the mold is performed by dry air. 11. In the step of pouring the molten metal,
11. The casting method according to claim 1, wherein at least the temperature near the mold cavity is measured, and molten metal is poured corresponding to this temperature. 12. A casting method for pouring molten metal into a mold, wherein the mold is cooled to a temperature below room temperature from the mold surface with at least dry air in a state in which moisture does not adhere to the inner surface of the mold cavity. A casting method comprising: a step; and a step of pouring molten metal in a state where the mold is cooled by using a cooling means having a temperature of -10 ° C or lower. 13. A casting method for pouring molten metal into a mold, wherein the mold is cooled in advance to a temperature below room temperature from the mold surface with at least dry air without adhering moisture to the inner surface of the mold cavity. And a step of pouring the molten metal by a vacuum action performed at least from the lower side of the mold in a state where the mold is cooled using a cooling means having a temperature of −10 ° C. or lower. Casting method.