JP3600797B2 - Reduction casting method and casting apparatus used therefor - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a casting method and a casting apparatus.
[0002]
[Prior art]
Aluminum casting methods include gravity casting (GDC), low pressure casting (LPDC), die casting (DC), squeeze (SC), and thixomolding. In each of these casting methods, a molten aluminum is poured into a cavity of a mold to perform casting.
In general, aluminum or an alloy thereof has a property of easily forming an oxide film. Therefore, in the aluminum casting process, an oxide film is easily formed on the surface of a molten aluminum. As a result, the surface tension of the molten aluminum increases, and the fluidity, melting and welding properties of the molten aluminum decrease, and various casting defects occur. For this reason, various improvements and techniques have been studied regarding the use of a mold coating agent, a method for injecting a molten metal into a mold, and an injection speed and pressure for injecting the molten metal.
[0003]
For example, in the area of GDC or LPDC, a method of applying an adiabatic release agent, a method of arranging a gate, and the like in a GDC or LPDC region as a countermeasure against a molten metal run-out due to the growth of an oxide film formed on a molten metal surface, a hot water wrinkle, a hot water boundary, and the like. In addition, in the DC region, high-pressure short-time filling is performed by the filling speed, pressure, gate arrangement, overflow taking, etc. of the aluminum melt in the DC area. ing. In the area of SC or the like, the oxide film on the surface of the molten aluminum is forcibly destroyed and fused by applying high pressure in the area of GDC.
[0004]
However, the conventional aluminum casting method has advantages and disadvantages, and in particular, it is extremely difficult to eliminate hot water wrinkles, hot water boundaries and minute unfilling that occur in cast products due to the oxide film on the surface of the molten aluminum. there were. For this reason, among aluminum castings, aluminum products that are problematic in surface stress, notch, etc., especially aluminum structures used in aircraft, automobiles, etc., have variations in reliability, and therefore, fluorescent A 100% inspection by flaw detection or the like, or an aluminum cast product obtained by casting is subjected to surface processing to be a final product, which has led to an increase in cost of the aluminum product.
[0005]
[Background Art]
Japanese Patent Application Laid-Open No. 2000-280063 discloses a technique for eliminating a wrinkle or the like of a cast product caused by an oxide film on the surface of a molten aluminum, which was difficult to solve by such a conventional aluminum casting method.
The above technology reacts nitrogen gas and magnesium gas to generate a magnesium nitrogen compound, introduces a molten metal in a state where the magnesium nitrogen compound is deposited on the surface of the mold, reduces an oxide film on the metal surface, The surface tension of the molten metal is reduced to improve its fluidity and wettability with the mold (= reducing the surface tension of the molten metal to make it easier to spread and improve the adhesion to the mold). Therefore, it is possible to improve the fluidity of the molten metal and the flowability of the molten metal, and to keep the heat for ensuring the flowability of the molten metal, reduce and eliminate the heat-insulating mold release agent, and provide an inexpensive and high-quality aluminum casting method. is there.
[0006]
[Problems to be solved by the invention]
According to the above technique, a magnesium nitrogen compound (reducing compound) is generated in a heating furnace arranged at a position distant from the mold, and the magnesium nitrogen compound is introduced into a cavity of the mold using nitrogen gas. However, if the distance is long, there is a problem that the magnesium nitrogen compound precipitates and accumulates on the surface in the pipe, and the pipe is easily clogged.
Then, this invention is made in order to solve the said subject, and it aims at providing the casting method and casting apparatus which can prevent the clogging in piping.
[0007]
[Means for Solving the Problems]
According to the reduction casting method according to the present invention, in a casting method in which a reducing compound is generated on a cavity surface of a mold and a metal oxide film on a surface of a molten metal filled in the cavity is reduced by the reducing compound, Immediately before the mold, a reaction chamber for reacting a metal gas and a reactive gas that reacts with the metal gas to generate the reducing compound is disposed, and the reducing compound generated in the reaction chamber is placed in the cavity. To form a reducing compound on the surface of the cavity, and then fill the cavity with a molten metal.
As described above, since the reaction chamber (heating furnace) is disposed immediately before the mold, clogging of the pipe (introduction path) by the reducing compound is prevented as much as possible. In addition, since the reducing compound is introduced into the cavity in a more activated state in a high temperature state, the reactivity with the molten metal is improved.
[0008]
The reducing compound generated in the reaction chamber may be introduced into the cavity by the reactive gas.
Alternatively, the reducing compound generated in the reaction chamber may be separately introduced into the cavity by a carrier gas that does not react with the metal that generates the metal gas.
By using magnesium gas for the metal gas and nitrogen gas for the reactive gas, the generated magnesium nitrogen compound reduces and eliminates the oxide film on the surface of the aluminum melt, thereby increasing the fluidity of the aluminum melt. This makes it possible to eliminate defects such as hot water wrinkles, hot water borders, minute unfilling and shrinkage, and to obtain a high-quality aluminum casting.
Argon gas can be suitably used as the carrier gas.
[0009]
Also, the metal gas may be generated by a metal gas generator provided separately from the reaction chamber, and the metal gas may be sent into the reaction chamber.
In this case, a large metal gas generator is used, and the metal gas generated by the metal gas generator is distributed to a plurality of reaction chambers, so that a plurality of molds can be operated efficiently.
Further, in this case, by maintaining the wall temperature of the reaction chamber at 400 ° C. or higher, the reducing compound is introduced into the cavity in a more activated state while maintaining a high temperature state, so that the reactivity with the molten metal is improved. I do.
[0010]
Further, in the casting apparatus according to the present invention, in the casting apparatus, a reducing compound is generated on a cavity surface of a mold, and a metal oxide film on a surface of a molten metal filled in the cavity is reduced by the reducing compound. Immediately before, a reaction chamber for reacting a metal gas with a reactive gas that reacts with the metal gas to generate the reducing compound is disposed integrally with a mold, and a valve is provided between the reaction chamber and the mold. It is characterized in that it is communicated via a.
As described above, since the reaction chamber (heating furnace) is disposed immediately before the mold, clogging of the pipe (introduction path) by the reducing compound is prevented as much as possible. In addition, since the reducing compound is introduced into the cavity in a more activated state in a high temperature state, the reactivity with the molten metal is improved.
[0011]
The reaction chamber may be provided with a first introduction path for introducing a metal powder for generating the metal gas and a second introduction path for introducing the reactive gas.
Further, a third introduction path for introducing a carrier gas which does not react with the metal for generating the metal gas can be provided in the reaction chamber.
[0012]
A communication passage for introducing the reducing compound generated in the reaction chamber into the cavity may be connected to a gate or a position immediately before the cavity where the molten metal in the cavity is introduced. By doing so, the molten metal comes into contact with the reducing compound immediately before being introduced into the cavity 12a and is introduced into the cavity, so that the fluidity of the molten metal in the cavity is improved.
Further, the reaction chamber may be integrally provided on an upper portion of the mold.
[0013]
A metal gas generator may be provided separately from the reaction chamber, and the metal gas generator may be connected to the reaction chamber.
In this case, it is preferable to provide a heater on the outer peripheral wall of the reaction chamber to maintain the temperature of the wall surface of the reaction chamber at 400 ° C. or higher.
In the present invention, the term “aluminum” includes not only pure aluminum but also an aluminum alloy containing aluminum as a base material, for example, silicon, magnesium, copper, nickel, tin, or the like.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 shows an example of a casting apparatus. Reference numeral 12 denotes a molding die, and reference numeral 28 denotes a heating furnace as a reaction chamber.
The heating furnace 28 is connected to the nitrogen gas cylinder 20 by a pipe 22, and by opening a valve 24, nitrogen gas as a reactive gas is injected into the heating furnace 28.
The argon gas cylinder 25 is connected to the heating furnace 28 by a pipe 26, and the argon gas can be injected into the heating furnace 28 by opening the valve 30. The inside of the heating furnace 28 is formed so as to be heatable by a heater, and the temperature in the furnace is set to 800 ° C. or more at which magnesium powder sublimates to generate gaseous magnesium (magnesium gas) as a metal gas described later. Have been.
[0015]
The argon gas cylinder 25 is connected to a tank 36 containing magnesium powder (metal powder) by a pipe 34 in which a valve 33 is interposed, and the tank 36 is connected by a pipe 38 to a pipe 26 downstream of the valve 30. It is connected to the. This pipe 38 is also provided with a valve 40.
The heating furnace 28 is connected to the cavity 12a (FIG. 3) of the mold 12 via a pipe 42 and a valve 45.
[0016]
FIG. 2 shows an example of the heating furnace 28.
50 is an outer casing formed of a heat insulating material and having an open upper surface. Inside the outer casing 50, a furnace body 52 having a flange 51 extending outward and having an open upper surface is arranged. The furnace main body 52 is formed of a heat-resistant material.
A cover 54 made of a heat-resistant material is fixed to the flange 51 by a bolt 55 made of a heat-resistant material so as to cover the furnace main body 52. A metal seal 56 is interposed between the lid 54 and the flange 51.
The heater 32 is disposed in a space between the furnace main body 52 and the outer casing 50 so that the inside of the furnace main body 52 can be heated.
[0017]
The lid 54 is provided with four openings 58, 59, 60 (one not shown) that opens into the furnace main body 52. These openings 58, 59, 60 are formed as tapered holes having a large diameter on the upper surface side of the lid 54.
An introduction pipe 62 (introduction path) is connected to the pipe 26 via a joint 61, and the introduction pipe 62 penetrates through the opening 58 and enters the furnace main body 52, and the lower end thereof is formed on the inner bottom surface of the furnace main body 52. Open to the vicinity. A gap between the introduction pipe 62 and the inner wall surface of the opening 58 is sealed with a metal seal 64.
[0018]
An introduction pipe 72 (introduction path) is connected to the pipe 22 via a joint 71, and the introduction pipe 72 penetrates the opening (not shown) and enters the furnace main body 52. It is open near the inner bottom surface. The gap between the introduction pipe 72 and the inner wall surface of the opening is also sealed with a metal seal (not shown).
Reference numeral 65 denotes a thermocouple whose tip enters the furnace main body 52 through the opening 59 so that the temperature inside the furnace main body 52 can be detected. The gap between the thermocouple 65 and the opening 59 is also sealed by the metal seal 66.
[0019]
A delivery pipe 69 (delivery path) is connected to the pipe 42 via a joint 68, and the delivery pipe 69 is inserted through the opening 60, and the distal end of the delivery pipe 69 opens into the upper space of the furnace main body 52. The gap between the delivery pipe 69 and the opening 60 is also sealed by the metal seal 70. 45 is a valve.
The pipe 42 is communicated with the cavity 12 a of the mold 12.
As shown in the drawing, the heating furnace 28 and the forming die 12 are located as close as possible, that is, the heating furnace 28 is disposed immediately before the forming die 12, so that the pipe 42 and the delivery pipe 69 are as long as possible. Is set to be shorter.
[0020]
Reference numeral 74 denotes a cover formed of a heat insulating material, which is provided so as to cover the lid 54, the bolt 55, the metal seals 64, 66, 70, the base of the introduction pipe 62, the base of the thermocouple 65, the base of the delivery pipe 69, and the like. Have been.
Reference numeral 76 denotes a cover formed of a heat insulating material, which further covers the exposed portions of the delivery pipe 69, the joint 68, the pipe 42, and the valve 45.
This prevents the heat in the furnace main body 52 from escaping from the lid 54 side.
[0021]
In particular, if the heat retention of the delivery pipe 69 and the pipe 42 is insufficient, the magnesium nitrogen compound generated with great care adheres to the inside wall of the delivery pipe 69 and the pipe 42, and these pipes may be clogged. By shortening the lengths of the delivery pipe 69 and the pipe 42 as much as possible, and further covering these exposed portions with the cover 76, clogging could be eliminated as much as possible.
[0022]
Next, an example of the molding die 12 is shown in FIG.
The molding die 12 has a tenon 16 which is movably inserted in a vertical direction into a molten metal inlet 11a constituting a molten metal injection hole 11 into which a molten aluminum is poured into a cavity 12a. The molten metal injection port 11a and the cavity 12a are communicated with each other by a molten metal injection path 11b, and the molten metal injected from the molten metal injection port 11a passes through the molten metal injection path 11b and is injected into the cavity 12a. An injection hole 44a for a gaseous reducing compound (magnesium nitrogen compound) is connected in the middle of the hot water injection path 11b. The pipe 42 is connected to the injection hole 44a.
[0023]
Further, headers 23a and 23b are formed in the mold 12 with the cavity 12a interposed therebetween, and the pressure reducing holes 17a are connected to the headers 23a and 23b. Such header 23a, and the 23b and the cavity 12a, and is connected by a passage 15, 15 ... as shown in FIG. 3 (b).
[0024]
When performing aluminum casting by the casting apparatus 10 shown in FIG. 1, first, the valves 24 and 45 are opened, the nitrogen gas cylinder 20 passes through the pipes 22 and 42, the heating furnace 28, and the cavity 12 a of the mold 12. Nitrogen gas is injected into the heating furnace 28, and air in the heating furnace 28 and the cavity 12a is purged with the nitrogen gas. The air in the cavity 12a is exhausted from the decompression hole 17a, and the inside of the cavity 12a can be set to a nitrogen gas atmosphere and a substantially non-oxygen atmosphere. Thereafter, the valves 24 and 45 are once closed.
It is preferable that the inside of the cavity 12a is sucked by a vacuum device (not shown) through a pressure reducing hole 17a to be in a reduced pressure state. A valve is provided in a pipe (not shown) connected to the pressure reducing hole 17a.
[0025]
The valve 30 may be opened to purge the inside of the heating furnace 28 and the cavity 12a with argon gas.
Next, the valve 30 is closed, the valves 33, 40, and 45 are opened, and the magnesium powder in the tank 36 is fed into the heating furnace 28 together with the argon gas by the argon gas pressure. At the same time, the valve 24 is opened, and nitrogen gas is sent into the heating furnace 28. The heating furnace 28 is heated by the heater 32 to a furnace temperature of 800 ° C. or higher at which the magnesium powder sublimes. For this reason, the magnesium powder fed into the heating furnace 28 is sublimated into magnesium gas, and reacts with nitrogen gas to generate a magnesium nitrogen compound (reducing compound, Mg ₃ N ₂ ). This magnesium nitrogen compound is fed into the cavity 12a together with the argon gas as a carrier gas, and precipitates as a powder on the inner wall surface of the cavity 12a.
[0026]
With the magnesium nitrogen compound adhered to the inner wall surface of the cavity 12a, the tenon 16 is pulled up, and molten aluminum in a pouring tank (not shown) is injected into the cavity 12a.
The molten aluminum poured into the cavity 12a comes into contact with the magnesium-nitrogen compound attached to the inner wall surface of the cavity 12a, and the magnesium-nitrogen compound deprives the oxide film on the surface of the molten aluminum of oxygen of the molten aluminum. The surface is reduced to pure aluminum.
Oxygen remaining in the cavity 12a or oxygen mixed in the molten aluminum reacts with the magnesium nitrogen compound to become magnesium oxide or magnesium hydroxide and is taken into the molten metal. Magnesium oxide and the like produced in this manner are small and stable compounds and do not adversely affect the quality of the resulting aluminum casting.
[0027]
As described above, since the magnesium nitrogen compound removes oxygen from the oxide film on the surface of the molten aluminum to form pure aluminum, casting can be performed without forming an oxide film on the surface of the molten metal. For this reason, it is possible to prevent the surface tension of the molten aluminum from increasing due to the oxide film during the casting process, and it is possible to improve the wettability, fluidity, and flowability of the molten aluminum. As a result, it is possible to obtain a good aluminum casting having excellent transferability (smoothness) of the inner wall surface of the cavity 12a and free of hot water wrinkles and the like.
[0028]
In the present embodiment, it is necessary that the magnesium nitrogen compound attached to the surface of the cavity 12a of the mold 12 has a reducing property. Usually, the metal material forming the mold 12 is non-reactive with the magnesium nitrogen compound generated in the cavity 12a in the temperature range of the aluminum casting process.
However, when an oxide-based heat-insulating agent or release agent, which is generally used as a treatment of the inner wall surface of the cavity, is applied to the inner wall surface of the cavity 12a when casting aluminum, the magnesium nitrogen The compound loses its reducing function by reacting with an oxygen group such as a heat insulating agent. For this reason, it is necessary to form the inner wall surface of the cavity 12a with a material that is non-reactive with a reducing compound such as a magnesium nitrogen compound.
Therefore, when coating the inner wall surface of the cavity 12a of the molding die 12, it is preferable to coat with a non-oxide material such as graphite. Further, the inner wall surface of the cavity 12 which has been subjected to a heat treatment (forming process of iron tetroxide) or a nitriding treatment may be used.
[0029]
In the above description, argon gas is used as the carrier gas, but nitrogen gas itself, which is a reactive gas, may be used as the carrier gas.
That is, in FIG. 1, the nitrogen gas cylinder 20 is disposed at the position of the argon gas cylinder 25 without using the argon gas cylinder 25. The piping 22, the valve 24, etc. become unnecessary.
First, the inside of the heating furnace 28 and the inside of the cavity 12a are purged with nitrogen gas, and then nitrogen gas is supplied into the heating furnace 28 together with magnesium powder as a carrier gas and a reactive gas.
[0030]
FIG. 4 shows still another embodiment.
The same members as those in the previous embodiment are denoted by the same reference numerals.
In the present embodiment, the heating furnace 28 and the mold 12 are provided closer to each other. That is, a communication passage 44b instead of the pipe 42 is provided in the flange 51 of the furnace main body 52 and is opened to the side wall. This communication path 44b is directly connected to the injection port 44a of the molding die 12. The valve 45 was provided on the mold 12 side.
By doing so, the heat retention is further secured, so that the clogging of the magnesium nitrogen compound in the communication passage 44b or the like can be surely eliminated.
[0031]
Although the casting apparatus described in the above embodiment performs aluminum casting by gravity casting, the present invention can be applied to a conventionally practiced aluminum casting method. For example, the casting apparatus shown in FIG. 5 performs aluminum casting by a pressure casting method. In the casting apparatus shown in FIG. 5, the molding die 12 is composed of an upper molding die 46 and a pressing molding die 47. The molding die 12 shown in FIG. 5 has higher airtightness than the molding die used in the gravity casting method shown in FIG.
In the casting apparatus 10 shown in FIG. 5, a vacuum pump 49 is connected to the cavity 12a via a pipe 48. The pipe 48 is provided with a valve 53. The inside and outside of the mold 12 are connected by a pipe 57, and the pipe 57 is provided with a valve 63.
[0032]
In the case of casting using the casting apparatus 10 shown in FIG. 5, first, the valve 63 is closed and the valve 53 is opened to drive the vacuum pump 49 to reduce the pressure inside the cavity 12a of the mold 12. Due to such reduced pressure, the inside of the cavity 12a can be made substantially non-oxygen.
Next, in the same manner as above, the valve 30 was opened to inject nitrogen gas from the nitrogen gas cylinder 20 into the heating furnace 28, and then the valve 33 was opened to feed magnesium powder and nitrogen gas from the tank 36 to the heating furnace 28, The powder is sublimated and reacted with nitrogen gas to produce a magnesium nitrogen compound.
[0033]
The generated magnesium nitrogen compound is fed into the cavity 12a using nitrogen gas as a carrier gas, and the magnesium nitrogen compound is deposited on the inner wall of the cavity 12a.
In this manner, the molten aluminum is injected into the cavity 12a by pushing up the pressing mold 51 with the powder of the magnesium nitrogen compound adhered to the inner wall surface of the cavity 12a.
At this time, since the magnesium nitrogen compound adheres to the inner wall surface of the cavity 12a, casting can be performed while preventing an oxide film from being formed on the surface of the molten aluminum by the same action as described above. As a result, a good quality aluminum casting can be obtained.
Also in the present embodiment, the heating furnace 28 and the molding die 12 are arranged close to each other, as shown in FIG. 2 or FIG.
[0034]
In the molding die 12 shown in FIG. 5, the inner wall surface of the cavity 12a is heat-treated to form a treatment film 12b made of iron tetroxide. Since iron tetroxide has no reactivity with the magnesium nitrogen compound, the treatment film 12b does not impair the function of reducing the magnesium nitrogen compound.
As the treatment of the inner wall surface of the cavity 12a, a nitriding treatment can also be mentioned.
Further, in the casting apparatus 10 shown in FIG. 5, the injection of the molten aluminum can be facilitated by opening the valve 63 during the injection of the molten aluminum or during the pressure casting.
[0035]
FIG. 6 shows an example in which a metal gas generator 100 is provided separately from the reaction chamber 28.
The metal gas generator 100 includes a heating furnace (reaction chamber) 28 shown in FIG.
The reactive gas (nitrogen gas) supply unit (nitrogen gas cylinder 20, pipe 22, valve 24, etc.) is removed. Metal powder (magnesium powder) is supplied into the metal gas generator 100 from the pipe 26 by an argon gas (carrier gas). Then, the inside of the metal gas generator 100 is heated to a temperature of 800 ° C. or higher by the heater 32a, the metal powder (magnesium powder) is sublimated, and a metal gas is generated. The metal gas generator 100 is insulated by a heat insulating wall (not shown).
[0036]
The generated metal gas is supplied into the heating furnace 28 through the pipe 102. It is preferable that the inside of the pipe 102 be heated by the heater 104 so that the temperature of the metal gas does not decrease.
On the other hand, a reactive gas (nitrogen gas) is supplied into the heating furnace 28 through the pipe 22. The two pipes may be connected such that the open ends of the pipe 102 and the pipe 22 into the heating furnace 28 face each other so that the metal gas and the reactive gas collide with each other.
The heating furnace 28 is preferably maintained by the heater 32 so that the wall surface temperature (the inner wall surface temperature of the heating furnace) is 400 ° C. or higher. Further, it is preferable to insulate the heating furnace by a heat insulating wall (not shown).
[0037]
Thus, both gases are supplied into the heating furnace 28, and the two gases react to generate a reducing compound (magnesium nitrogen compound).
By maintaining the inside of the heating furnace 28 at a high temperature by the heater 32, the reactivity of both gases is increased (the reaction rate is increased), and the generated reducing compound is more activated while maintaining the high temperature state. Since it is introduced into the cavity 12a in a state, the reactivity with the molten metal is improved.
The heating furnace 28 is preferably provided directly above the mold 12 closer to the cavity 12a. The heating furnace 28 is connected through a short communicating furnace 106 immediately before the hot water inlet (gate) or the cavity 12a. By doing so, the molten metal comes into contact with the reducing compound immediately before being introduced into the cavity 12a and is introduced into the cavity, so that the fluidity of the molten metal in the cavity is improved.
[0038]
In the present embodiment, since the metal gas generator 100 is provided separately from the reaction chamber, the metal gas generator 100 is made relatively large, and the generated metal gas is supplied to the plurality of reaction chambers 28 (therefore, the plurality of reaction chambers 28). Mold). Therefore, one metal gas generator 100 can handle a plurality of molds, and each reaction chamber can be reduced in size.
Although the metal powder is supplied to the metal gas generator 100 in the illustrated example, a block-shaped or granular metal may be supplied.
[0039]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, it becomes difficult for a reducing compound (magnesium nitrogen compound) to deposit in a piping (communication path), and stable supply of a reducing compound can be performed. In addition, since the reducing compound is introduced into the cavity in a more activated state in a high temperature state, the reactivity with the molten metal is improved.
The presence of the reaction chamber (heating furnace) integrated with the mold makes the apparatus itself compact and takes up little space.
[Brief description of the drawings]
FIG. 1 is a schematic view showing an example of a casting apparatus.
FIG. 2 is a sectional view showing an example of a reaction chamber.
FIG. 3 is a cross-sectional view illustrating an example of a molding die.
FIG. 4 is an explanatory diagram showing another connection example of the reaction chamber and the mold.
FIG. 5 is a schematic view showing a casting apparatus used in another casting method.
FIG. 6 is an explanatory view showing an example in which a metal gas generator is provided separately from a reaction chamber.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Casting apparatus 12 Mold 12a Cavity 12b Processing film 17a Decompression hole 20 Nitrogen gas cylinder 25 Argon gas cylinder 28 Heating furnace (reaction chamber)
32 heater 36 tank 44a injection hole 44b communication path 100 metal gas generator 106 communication path

Claims (16)

In a casting method, a reducing compound is generated on a cavity surface of a mold, and a metal oxide film on a surface of a molten metal filled in the cavity is reduced by the reducing compound.
Immediately before the mold, a reaction chamber for reacting a metal gas and a reactive gas that reacts with the metal gas to generate the reducing compound is disposed, and the reducing compound generated in the reaction chamber is placed in the cavity. A reducing compound produced on the surface of the cavity by introducing the molten metal into the cavity, and then filling the cavity with the molten metal. The reduction casting method according to claim 1, wherein the reducing compound generated in the reaction chamber is introduced into the cavity by the reactive gas. 2. The reduction casting method according to claim 1, wherein the reducing compound generated in the reaction chamber is introduced into the cavity by a carrier gas that does not react with a metal that generates the metal gas. The metal gas is magnesium gas, the reactive gas is nitrogen gas, the reducing compound is a magnesium nitrogen compound, and the molten metal is molten aluminum. Reduction casting method. 4. The reduction casting method according to claim 3, wherein the carrier gas is an argon gas. 6. The reduction casting method according to claim 1, wherein the metal gas is generated by a metal gas generator, and the metal gas is sent into the reaction chamber. 7. The reduction casting method according to claim 6, wherein a wall surface temperature of the reaction chamber is set to 400 ° C. or higher. In a casting apparatus that generates a reducing compound on the cavity surface of the mold and reduces the metal oxide film on the surface of the molten metal filled in the cavity by the reducing compound,
Immediately before the mold, a reaction chamber for reacting a metal gas and a reactive gas that reacts with the metal gas to generate the reducing compound is disposed integrally with the mold, and the reaction chamber and the mold are provided. And a valve, which are connected via a valve. 9. The reaction chamber according to claim 8, wherein a first introduction path for introducing the metal powder for generating the metal gas and a second introduction path for introducing the reactive gas are provided. Casting equipment. The casting apparatus according to claim 8, wherein a third introduction path for introducing a carrier gas that does not react with the metal that generates the metal gas is provided in the reaction chamber. 11. The communication path for introducing a reducing compound generated in the reaction chamber into a cavity is connected immediately before a gate or a cavity for introducing molten metal in the cavity. Casting equipment. The casting apparatus according to claim 8, 9, 10, or 11, wherein the reaction chamber is provided integrally with an upper portion of the mold. The casting apparatus according to claim 8, wherein a metal gas generator is provided, and the metal gas generator is connected to the reaction chamber. 14. The casting apparatus according to claim 13, wherein a heater is provided on an outer peripheral wall of the reaction chamber, and a wall temperature of the reaction chamber is set to 400 ° C. or higher. The metal gas is magnesium gas, the reactive gas is nitrogen gas, the reducing compound is a magnesium nitrogen compound, and the molten metal is molten aluminum. The casting apparatus according to claim 11, 12, 13, or 14. 15. The casting apparatus according to claim 8, wherein the carrier gas is an argon gas .

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