JP2011016166A - Casting apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a casting apparatus wherein a sprue of a die can be maintained constantly at a high temperature, any molten metal basin for heating the sprue is not required, any return of the molten metal to a furnace side for each release is not required, the casting cycle can be shortened, and any oxide is hardly generated in the molten metal.SOLUTION: In the casting apparatus, a molten metal is filled in a die 4 from a molten metal tank where the metal is stored in a molten state via a stoke 8, and then the molten metal is solidified in the die 4 to form a casting. A flow passage of the molten metal before reaching a sprue 9 of the die 4 is surrounded by a heat storage body 17 to be heated by a heater 18. A ceramic coating is executed on the flow passage of the molten metal before reaching the sprue 9 of the die 4.

Description

  The present invention relates to a casting apparatus for filling a mold with a molten metal from a molten metal tank in which the metal is stored in a molten state, and then solidifying the molten metal in the mold to mold a casting, and more particularly to a mold after casting. The present invention relates to a casting apparatus that prevents the molten metal from being cooled and hardened on the side of the mold when the mold is removed, thereby shortening the casting cycle and improving the casting yield.

  There are a low pressure casting method, a differential pressure casting method, a reduced pressure casting method, and the like as a method of casting by filling a molten metal into a cavity using a pressure difference between a molten metal and a casting-shaped cavity. Among these, the low-pressure casting method applies a relatively low pressure by a gas such as an inert gas or carbon dioxide to a closed furnace containing molten metal, and this pressure pushes the molten metal in the closed furnace upward through stalk. This is a method of manufacturing a casting by filling molten metal into a mold placed above a closed furnace. This low-pressure casting method is widely used for producing cast products such as aluminum alloys used for vehicle members and the like.

  FIG. 6 is a sectional view showing a conventional low-pressure casting apparatus. A supply source (not shown) of a gas such as an inert gas or carbon dioxide is connected to a gas inlet 20 provided at the top of the hermetically sealed hermetic furnace 1, and the gas is pumped into the hermetic furnace 1. A crucible 2, which is a heat-resistant graphite container having an upper surface opened, is accommodated in the closed furnace 1, and a heater 3 is disposed along the outer wall of the crucible 2. The lower end of the stalk 8 attached to the lid of the closed furnace 1 is immersed in the center of the crucible 2. A mold 4 including a lower mold 5 and an upper mold 6 is disposed on the closed furnace 1. Concave portions are respectively formed on the mating surfaces of the lower die 5 and the upper die 6, and when the lower die 5 and the upper die 6 are overlapped, a casting-shaped cavity 10 is formed by the concave portions. Is done. A core 7 is accommodated in the cavity 10 as necessary. The upper end of the stalk 8 is connected to a gate 9 that leads to a cavity 10 provided at the bottom of the mold 4.

  In such a casting apparatus, an inert gas is injected into the closed furnace 1 from the gas injection port 20. With this gas pressure, the molten metal surface in the crucible 2 is pressurized and the molten metal is pushed up and filled into the mold cavity 10 via the stalk 8. After the molten metal filled in the cavity 10 is cooled and solidified, the upper mold 6 is raised by a hydraulic mechanism (not shown) to open the cavity 10 and take out the casting from the lower mold 5.

  FIG. 7 shows an example in which the molten metal stored in the closed furnace 1 is sent to the water reservoir 12 through the stalk 8 ′ and filled into the cavity 10 of the mold 4 from the water reservoir 12. The molten metal in the closed furnace 1 is heated by the immersion heater 13 and the molten state is maintained. Molten metal is supplied into the closed furnace 1 from a molten metal supply port 11. The portion from the stalk 8 'to the hot water reservoir is heated by the heater 3 to prevent the molten metal from solidifying due to a decrease in temperature. Other configurations are basically the same as those of the conventional example of FIG. 6, and the same portions are indicated by the same reference numerals.

  FIG. 8 shows the conventional casting apparatus described above with reference to FIG. 6, in which the molten metal is pumped into the mold 4 by a molten metal electromagnetic pump regardless of the gas pressure. That is, an inductor 14 of a molten metal electromagnetic pump is provided outside the intermediate portion of the stalk (duct) 8, and a core 15 for forming a magnetic path of a magnetic field generated by the inductor 14 in the stalk 8 correspondingly. Is arranged. A three-phase current is passed through the inductor 14, thereby generating a moving magnetic field between the inductor 14 and the core 15, giving an upward thrust to the molten metal in the stalk 8. The cavity 10 is filled. Other configurations are basically the same as those of the conventional example of FIG. 6, and the same portions are indicated by the same reference numerals.

  FIG. 9 shows the conventional casting apparatus described above with reference to FIG. 7, in which the molten metal is pumped into the mold 4 by a molten metal electromagnetic pump regardless of the gas pressure. That is, an inductor 14 of a molten metal electromagnetic pump is provided outside the middle portion of the stalk (duct) 8 ', and a magnetic path for a magnetic field generated by the inductor 14 is formed in the stalk 8' correspondingly. A core 15 is arranged. A three-phase current is passed through the inductor 14, thereby generating a moving magnetic field between the inductor 14 and the core 15, and applying an upward thrust to the molten metal in the stalk 8 ′. 4 cavities 10 are filled. Other configurations are basically the same as those of the conventional example of FIG. 7, and the same portions are denoted by the same reference numerals.

  In such a low-pressure casting apparatus, when the molten metal is solidified in the cavity 10 of the mold 4, the molten metal corresponding to the solidified and contracted volume must always be supplied through the gate 9 of the mold 4. For this purpose, as shown in FIGS. 6 and 8, the stalks 8 connected to the gate 9 are heated by thermal radiation from the crucible 2 side and directly heated by the heater 3 '. As shown in FIGS. 7 and 9, in the case where the mold 4 is arranged apart from the closed furnace 1, a hot water reservoir 12 is provided under the mold 4, and the hot water reservoir 12 is heated by the heater 3. . By adopting such a structure, the mold 4 has a temperature gradient in the order of the temperature from the top 9, the lower mold 5, and the upper mold 6, and the molten metal in the cavity 10 flows from top to bottom. Directional solidification is performed in which the molten metal at the gate 9 is solidified. During this time, a volume of molten metal solidified and contracted is supplied into the cavity 10 from the gate 9 side. Thereby, it is possible to cast a casting having no so-called shrinkage nest or shrinkage.

  In the low-pressure casting method, bubbles and oxides are formed by gently filling the crucible 2 and the molten metal with a small amount of oxide in the closed furnace 1 ′ from the bottom into the cavity 10 of the mold 4 without entraining gas. There is an advantage that a casting containing no can be easily cast. Furthermore, due to the temperature gradient as described above, solidification of the molten metal occurs from the top to the bottom in the cavity 10, and finally the molten metal in the portion of the gate 9 solidifies, so that the molten metal solidifies in the cavity 10. The molten metal is additionally filled from the gate 9 by the contracted volume. Thus, no shrinkage or shrinkage occurs during the solidification of the molten metal in the cavity 10. For these reasons, the low-pressure casting method can cast a high quality casting as compared with other casting methods such as the gravity casting method and the die casting method.

  However, in the low pressure casting method, the heat capacity of the mold 4 is large, and heat is constantly supplied to the mold 4 by heat conduction from the molten metal in the stalk 8 and the sump 12. Further, the temperature of the mold 4 rises every casting cycle due to solidification latent heat released when the molten metal solidifies. For these reasons, the molten metal filled in the cavity 10 is difficult to solidify. Since the molten metal is solidified in the cavity 10 and becomes a certain strength, for example, in the case of aluminum, the casting cannot be taken out from the mold without being deformed unless the temperature is 400 ° C. or less. The casting time will be longer.

  In the case of die casting with a short casting cycle and high mass productivity, molten metal is injected and filled into the mold cavity, solidified, then demolded, and the casting is taken out. 1 casting cycle until the mold is closed is about several tens of seconds for a small casting, and within several minutes for a large casting. On the other hand, generally, in low pressure casting, one casting cycle takes 7 to 10 minutes.

  What is important in low-pressure casting is the above-described temperature gradient of the mold. That is, in order not to cause shrinkage or shrinkage in the casting, the molten metal filled in the cavity 10 starts to solidify first from a position farthest from the gate 9 and finally solidifies at the portion of the gate 9. Is required. For that purpose, it is particularly important to form a temperature gradient in the order of the gate 9, the lower mold 5, and the upper mold 6 in order of increasing temperature. For example, after the stalk 8 is replaced, if the preheating is not sufficient, the temperature of the gate 9 is lowered, and the molten metal may solidify and block the cavity 10. In order to prevent this, it is necessary to measure the temperature at the upper end of the gate 9 and the stalk 8. However, since thermocouples generally used for temperature measurement are weak against molten metal such as molten aluminum and must be covered with a protective tube, the temperature at the upper end of the gate 9 and stalk 8 is measured directly and in real time. Cannot be performed, and the temperature measurement value has an error or a time lag.

  The mold is generally made of steel, has a large heat capacity, and takes time to rise and fall. For example, in the temperature rise in preparation for casting, casting is started after preheating to a temperature of about 200 ° C. by gas burner heating for 1 to 2 hours. As the casting cycle is repeated, the temperature of the mold gradually rises. However, in order to prevent the mold temperature from becoming higher than a predetermined steady temperature (about 350 ° C in the case of aluminum casting), The peripheral member is designed to be naturally radiated and to have a saturation temperature. However, in this case, it takes time to lower the temperature to below the temperature (350 ° C. in the case of aluminum casting) at which the casting can be removed without being deformed in the cavity by the heat supply from the molten metal at the gate of the mold. .

  Conversely, when the casting in the cavity is lowered to a temperature at which the casting is not deformed, the temperature of the stalk and the sump in front of the pouring gate is taken away by the mold side, and the temperature is lowered to the vicinity of the freezing point of the molten metal. When the molten metal is injected into the mold at this temperature, the molten metal partially solidifies in the cavity, which causes a so-called hot water defect that prevents the molten metal from flowing in the cavity. Therefore, since the molten metal cannot be filled in the cavity as it is, a troublesome operation is required in which the molten metal in the stalk or the sump is once returned to the closed furnace 1, 1 'side, reheated, and then supplied again. . Further, at this time, air enters the sump or stalk, and oxides are formed in the portions of the molten metal that come into contact with the air, and maintenance such as oxide removal work is required.

  If the hot water reservoir 12 is enlarged, the temperature drop of the molten metal can be suppressed, but the apparatus becomes large. This sump must be placed under the mold because it is necessary to form a temperature gradient that heats the mold spout and gradually lowers the temperature from the spout onto the mold. For this reason, a low pressure casting apparatus cannot be cast with a mold placed sideways like a die casting machine. Placing the mold on the sump necessarily increases the position of the mold. Accordingly, the hydraulic mechanism for attaching the mold and opening / closing the mold has to be arranged at a high position, which makes the operation and maintenance troublesome.

JP 2006-334671 A Japanese Patent Laid-Open No. 07-116818 Japanese Patent Laid-Open No. 08-155629 JP 08-318361 A JP 09-94653 A

  In view of the problems in the conventional casting apparatus, the present invention can always maintain the mold gate at a high temperature, and does not require a sump for heating the mold. An object of the present invention is to provide a casting apparatus in which it is not necessary to return the molten metal to the furnace side, the casting cycle can be shortened, and oxides are not easily generated in the molten metal.

  In the present invention, in order to achieve the above-described object, a heat storage body having a large heat capacity is provided in a flow path portion that guides molten metal to the sprue of the cavity. In addition, magnesium oxide or the like, which is an inorganic heat storage material, was cast in cast iron, and the heat storage body was heated with a heater to maintain the temperature of the gate. As a result, it is possible to prevent the temperature of the gate from being lowered at the time of demolding, and to eliminate the need to return the molten metal before the gate to the furnace side, thereby shortening the casting cycle and preventing the generation of oxides of the molten metal.

  A stalk may be connected to the mold gate, and a heat storage body may be provided around the stalk gate side. Alternatively, the inner wall of the heat storage body may be a molten metal flow path, and the stalk may be connected thereto. In the latter case, the inner surface of the flow path of the molten metal surrounded by the heat storage body may be ceramic-coated or a thin ceramic tube may be inserted into the heat storage body. When the stalk is made of ceramic, a part of the stalk can also serve as the ceramic tube.

  As described above, in the casting apparatus according to the present invention, the heat storage body heated by the heater is disposed in the flow path in front of the pouring gate, instead of providing the hot water sump with a function for keeping the pouring gate, so that the pouring gate is provided at the time of demolding. The molten metal before is not cooled, and the operation of returning the molten metal once to the furnace side becomes unnecessary. Moreover, since a temperature drop on the mold side can be prevented by heating the heat storage body with a heater, so-called poor hot water can be prevented. The oxide of the molten metal generated when the molten metal is once returned to the furnace side is not generated. As a result, the casting cycle can be shortened and the casting yield can be improved.

It is sectional drawing which shows one Example of the casting apparatus by this invention. It is sectional drawing which shows the other Example of the casting apparatus by this invention. It is sectional drawing which shows the other Example of the casting apparatus by this invention. It is sectional drawing which shows the other Example of the casting apparatus by this invention. It is sectional drawing which shows the other Example of the casting apparatus by this invention. It is sectional drawing which shows the prior art example of a casting apparatus. It is sectional drawing which shows the other conventional example of a casting apparatus. It is sectional drawing which shows the other conventional example of a casting apparatus. It is sectional drawing which shows the other conventional example of a casting apparatus.

In the present invention, in order to achieve the object, a heat accumulator is disposed in the flow path before the gate of the mold, and this is heated by a heater to keep the gate hot.
Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to examples.

FIG. 1 is a sectional view showing an embodiment of a low-pressure casting apparatus according to the present invention. The configuration of the low-pressure casting apparatus is basically the same as that of the conventional example described above with reference to FIG. 6, and the same parts are denoted by the same reference numerals.
A gas supply source 20 such as an inert gas or carbon dioxide is connected to a gas inlet 20 provided in an upper portion of the hermetically sealed hermetic furnace 1, and the gas is pumped into the hermetic furnace 1. A crucible 2, which is a heat-resistant graphite container having an open top surface, is accommodated inside the closed furnace 1, and a heater 3 is disposed along the outer wall of the crucible. The lower end of the stalk 8 attached to the lid of the closed furnace 1 is immersed in the center of the crucible 2. A mold 4 including a lower mold 5 and an upper mold 6 is disposed on the closed furnace 1. Concave portions are respectively formed on the mating surfaces of the lower die 5 and the upper die 6, and when the lower die 5 and the upper die 6 are overlapped, a casting-shaped cavity 10 is formed by the concave portions. Is done. A core 7 is accommodated in the cavity 10 as necessary. The upper end of the stalk 8 is connected to a gate 9 leading to a cavity 10 provided at the bottom of the mold 4.

In such a casting apparatus, a heat storage body 17 is provided between the stalk 8 and the sprue 9 of the mold 4 that follows the stalk 8. The center of the heat storage body 17 is a hole, and that portion is a flow path of molten metal between the stalk 8 and the gate 9 of the mold 4. A ceramic coating 19 is applied to the inner surface of the flow path. Instead of the ceramic coating 19, a ceramic tube may be provided in the molten metal flow path at the center of the heat storage body 17.
The heat storage body 17 is provided with a heater 18 for heating it. For example, as shown in FIG.

  By arranging the heat storage body 17 heated by such a heater 18 in front of the gate 9 of the mold 4, the temperature of the gate 9 of the mold 4 is maintained, and the mold 4 has a gate 9 and a lower mold. 5. A temperature gradient with a higher temperature is formed in the order of the upper mold 6. Thereby, the molten metal in the cavity 10 is solidified from the top to the bottom, and finally the molten metal in the gate 9 is solidified. At this time, the molten metal of the solidified and contracted volume is additionally supplied into the cavity 10 from the side of the gate 9. Therefore, it is possible to cast a casting without so-called shrinkage nests or shrinkage.

  When casting a casting with this casting apparatus, an inert gas is injected into the closed furnace 1 from the gas inlet 20. With this gas pressure, the molten metal surface in the crucible 2 is pressurized and the molten metal is pushed up and filled into the mold cavity 10 via the stalk 8. After the molten metal filled in the cavity 10 is cooled and solidified, the upper mold 6 is raised by a hydraulic mechanism (not shown) to open the cavity 10 and take out the casting from the lower mold 5. Since the temperature of the gate 9 is maintained by the heat storage body 17 at the time of demolding for taking out the casting, it is not necessary to return the molten metal in front of the gate 9 to the crucible 2 side.

  FIG. 2 shows an example in which the molten metal stored in the closed furnace 1 ′ is filled into the cavity 10 of the mold 4 through the stalk 8 drawn out from the closed furnace 1 ′. The molten metal in the closed furnace 1 ′ is heated by the immersion heater 13 to maintain the molten state. Molten metal is supplied from the molten metal supply port 11 into the closed furnace 1 ′. The stalk 8 is continuously provided from the closed furnace 1 ′ to the gate 9 of the cavity 10 of the mold 4. The stalk 8 is heated by a heater 9 in order to prevent the molten metal from solidifying due to a temperature drop. Further, a heat storage body 17 is provided around a portion of the stalk 8 near the gate 9 of the mold 4. In other words, the portion of the stalk 8 is surrounded by the heat storage body 17.

  The heat storage body 17 is provided with a heater 18 for heating it. For example, a rod-shaped cartridge heater 18 is embedded in the heat storage body 17. Although the ceramic coating 19 is applied to the inner surface of the stalk 8, it is not necessary when the stalk 8 is made of ceramic. Other configurations are basically the same as those of the embodiment of FIG. 1, and the same portions are denoted by the same reference numerals.

  FIG. 3 shows a conventional casting apparatus described above with reference to FIG. 1, in which the molten metal is pumped into the mold 4 by a molten metal electromagnetic pump regardless of the gas pressure. That is, a molten metal inductor 14 is provided outside the middle portion of the stalk (duct) 8 and a core 15 for forming a magnetic path of the magnetic field generated in the inductor 14 is disposed in the stalk 8 correspondingly. is doing. A three-phase current is applied to the inductor 14, thereby generating a moving magnetic field between the inductor 14 and the core 15, and applying an upward thrust to the molten metal in the stalk 8. The cavity 10 is filled. Further, a ceramic tube 19 ′ is provided in the molten metal flow path at the center of the heat storage body 17 instead of the ceramic coating. Other configurations are basically the same as those of the embodiment of FIG. 1, and the same portions are denoted by the same reference numerals.

  FIG. 4 shows the conventional casting apparatus described above with reference to FIG. 2, in which the molten metal is pumped into the mold 4 by a molten metal electromagnetic pump provided in the middle of the stalk 8 regardless of the gas pressure. That is, in order to form a magnetic path of a magnetic field generated in the inductor 14 in the stalk 8 corresponding to this, the molten metal inductor 14 is provided outside the intermediate portion of the stalk (duct) 8 of the closed furnace 1 ′. The core 15 is arranged. A three-phase current is passed through the inductor 14, thereby generating a moving magnetic field between the inductor 14 and the core 15, giving an upward thrust to the molten metal in the stalk 8. The cavity 10 is filled. Other configurations are basically the same as those in the embodiment of FIG. 2, and the same portions are denoted by the same reference numerals.

FIG. 5 shows a horizontal injection casting apparatus in which the mold 4 is arranged in the horizontal direction in the conventional casting apparatus described above with reference to FIG. Since the gate 9 of the mold 4 also opens sideways, the gate side of the stalk 8 faces sideways, and the heat storage body 17 is disposed around this portion. The provision of the heater 18 for heating the heat storage body 17 is the same as that in the embodiment shown in FIG.
In this embodiment, since the mold 4 is oriented sideways, a hydraulic mechanism for attaching the mold 4 or opening the upper mold and removing it can be disposed beside the mold 4. This has the advantage that the hydraulic mechanism can be installed at a low position.

  Further, in the embodiment shown in FIG. 5, unlike the embodiment of FIG. 2, the pumping of the molten metal into the mold 4 is not dependent on the gas pressure, and the weight 21 immersed in the molten metal in the closed furnace 1 ′ This is performed by a molten metal electromagnetic pump provided in the middle of the stalk 8. That is, a molten metal inductor 14 is provided outside the middle portion of the stalk (duct) 8 and a core 15 for forming a magnetic path of the magnetic field generated in the inductor 14 is disposed in the stalk 8 correspondingly. is doing. Further, the weight 21 is immersed in the molten metal in the closed furnace 1 ′, and the liquid level of the molten metal on the stalk 8 side is adjusted by the vertical movement of the weight 21.

The molten metal in the closed furnace 1 ′ is pushed out to the stalk 8 side by the weight 2 in the closed furnace 1 ′, and the molten metal in the stalk 8 is a liquid level where the induction magnetic field by the inductor 14 acts, specifically, the molten metal. Is a liquid level exceeding the inductor 14. In this state, a three-phase current is applied to the inductor 14, thereby generating a moving magnetic field between the inductor 14 and the core 15, and applying an upward thrust to the molten metal in the stalk 8, Fill in the cavity 10 of the mold 4.
The other configurations of the embodiment shown in FIG. 5 are basically the same as those of the embodiment of FIG. 2, and the same portions are denoted by the same reference numerals.

  The present invention can be used to efficiently produce casting products such as aluminum alloys used for vehicle members and the like because casting can be cast with good yield by shortening the time of casting preparation and casting cycle. It is possible.

4 Mold 8 Stoke 9 Mold gate 17 Heat storage 18 Heater 19 Ceramic coating 19 'Ceramic tube

Claims (5)

In a casting apparatus in which molten metal is filled in a mold 4 through a stalk 8 from a molten metal tank in which a metal is stored in a molten state, and then the molten metal is solidified in the mold 4 to mold a casting. A casting apparatus characterized in that a flow path of molten metal in front of the fourth gate 9 is surrounded by a heat storage body 17 heated by a heater 18. The casting apparatus according to claim 1, wherein a ceramic coating 19 is applied to a flow path of the molten metal before reaching the gate 9 of the mold 4. The casting apparatus according to claim 1, wherein a ceramic tube (19 ') is provided in a molten metal flow path before reaching the gate (9) of the mold (4). The casting apparatus according to any one of claims 1 to 3, wherein a temperature gradient having a directivity from the gate 9 of the mold 4 to the inner part thereof is generated by a heat storage material irrespective of the hot water reservoir. The horizontal injection casting apparatus according to claim 4, wherein the mold 4 is arranged with the gate 9 facing sideways.

Images