JP2002331351A - Reducing casting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a casting method capable of obtaining a casting few in shrinkage, etc., to the utmost by casting wherein a forging material such as a forging aluminum alloy is used. SOLUTION: In casting a desired shaped casting by bringing an aluminum alloy molten metal poured in a cavity 11c of a mold 10 into contact with a magnesium nitride (Mg3 N2 ) as a reducing compound into contact, while reducing an oxide film formed on the surface of the molten metal, a molten metal obtained by melting the forging aluminum alloy is used as the molten metal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reduction casting method, and more particularly, to an oxide film formed on the surface of a molten metal by bringing a molten metal poured into a cavity of a mold into contact with a reducing compound. The present invention relates to a reduction casting method for casting a cast product having a desired shape while reducing the pressure.

[0002]

2. Description of the Related Art There are various aluminum casting methods. For example, a gravity casting method has high quality cast products.
It has many advantages such as simplicity of the mold. Such a mold is shown in FIG. The molding die 100 shown in FIG. 8 is made of metal and is a split die of a lower die 102a and an upper die 102b.
The lower mold 102a and the upper mold 102b form a cavity 104 in which a casting having a desired shape is cast. In the upper mold 102b, a feeder portion 108 is formed between a pouring port 106 for pouring a molten metal of aluminum or an alloy thereof and the cavity 104. Are also formed. By the way, when the molten aluminum or its alloy solidifies, it takes about 3
% Shrinkage occurs. Therefore, the cavity 104
The shrinkage caused by the solidification of the molten metal filled in the castings appears as defects such as sink marks in the obtained cast product. In this regard, FIG.
In the molding die 100 shown in FIG. 1, a part of the molten metal filled in the feeder 108 flows through a gap generated on the side of the feeder 108 due to shrinkage accompanying solidification of the melt filled in the cavity 104. To prevent sink marks on cast products.
Furthermore, the molten metal of aluminum or its alloy has a high surface tension due to the oxide film formed on its surface,
Fluidity, meltability and the like are reduced, and transferability of the mold 100 is inhibited. Therefore, the feeder 1 of the forming die 100 shown in FIG.
08 and the inner wall surface of the cavity 104 are coated with a mold wash agent capable of improving the fluidity and the like of the molten metal having an oxide film formed on the surface.

When casting aluminum using the molding die 100 shown in FIG. 8 as described above, a molten metal of aluminum or its alloy is poured into a pouring port 106 of the molding die 100, and the molten metal is discharged from air vent holes 110, 110,. The cavity 104 and the feeder unit 108 are filled with molten metal while removing air. Then
The molten metal in the cavity 104 is solidified by allowing the mold 100 filled with the molten metal in the cavity 104 and the like to cool. In the gap on the side of the feeder 108 generated due to the shrinkage of the molten metal in the cavity 104 due to solidification, a part of the molten metal in the feeder 108 flows down into the cavity 104 and is replenished. For aluminum casting using the molding die 100, an aluminum alloy is used as a casting material. As the aluminum alloy used as the casting material, an Al-Si based aluminum alloy is widely used. FIG. 9 shows a phase diagram of such an Al-Si based aluminum alloy. Among the Al-Si-based aluminum alloys shown in FIG. 9, Al commonly used as a casting material
The -Si-based aluminum alloy for casting has a hatched portion shown in FIG. 9, that is, about 5 to 10% of Si.

[0004]

As shown in FIG. 9, a molten metal obtained by melting an Al-Si casting aluminum alloy containing about 5 to 10% of Si has a liquid phase range α and a The crystal range (L + α) is wide and its fluidity is good. For this reason, when the molten metal is poured into the molding die 100 shown in FIG. 8, the fluidity of the cavity 104 is also good, and the resulting cast product is unlikely to cause sink marks or the like. However, a cast product made of an Al-Si casting aluminum alloy is inferior in strength and toughness as compared with a forged product made of an Al-Cu based forging aluminum alloy such as duralumin. On the other hand, in order to improve mechanical properties such as strength of a conventional cast product, Al-Cu
It is conceivable to use a system-based forging aluminum alloy for casting. However, as the Al-Cu-based forging aluminum alloy, an Al-Cu-based aluminum alloy containing approximately 2 to 5% of Cu, that is, a hatched portion in the phase diagram shown in Fig. 10 is used.

[0005] A molten metal obtained by melting such an Al-Cu forging aluminum alloy has a narrower liquid phase range α and lower fluidity than a molten aluminum alloy for Al-Si casting. Therefore, even if the molten metal is poured into the mold 100, the fluidity of the cavity 104 is inferior. Therefore, sink marks and the like are liable to occur in the obtained cast product, and conventionally, forging aluminum alloys have not been used for casting. However, in order to improve the strength and toughness of a cast product, it is an effective means to use a forging material such as an aluminum alloy for forging, which has not been conventionally used for casting. Accordingly, an object of the present invention is to provide a casting method capable of obtaining a cast product with as few sink marks as possible by casting using a forging material such as an aluminum alloy for forging.

[0006]

The present inventors have studied to solve the above-mentioned problems, and as a result, the present inventors have proposed a reduction casting method previously proposed in Japanese Patent Application No. 2000-108078, that is, a molding die. By applying the reduction casting method in which the molten metal is brought into contact with the reducing compound in the cavity of the molten metal and casting while reducing the oxide film formed on the surface of the molten metal to the casting of the aluminum alloy for forging, the appearance is good. The present inventors have found that a casting made of an aluminum alloy for forging can be obtained, and have reached the present invention. That is, according to the present invention, a molten metal of a metal poured into a cavity of a mold is brought into contact with a reducing compound, and an oxide film formed on the surface of the molten metal is reduced to cast a casting having a desired shape. In this case, there is provided a reduction casting method, wherein a molten metal obtained by melting a forging metal is used as the molten metal. In the present invention, Al-Cu is used as the forging metal.
Aluminum alloy for forging based on Al-Cu-Mg, Al-Cu-Mg-Zn or Al-Mg-Si, or an aluminum alloy containing copper (Cu) and / or magnesium (Mg) An aluminum alloy for forging having a copper (Cu) content of 5% or less and / or a magnesium (Mg) content of 3% or less can be suitably used. Furthermore, using an aluminum alloy for forging,
The cooling rate of the molten metal poured into the cavity is set to 500 ° C./min or more, or the cooling rate of the molten metal poured into the cavity is set such that the interval between the dendritic crystals of the solidified forging aluminum alloy is 25 μm on average. By adjusting so as to be less than the above, the appearance of the obtained cast product can be further improved.

Further, as a molding die, a feeder is formed between a pouring port for pouring the molten metal and a cavity, and the molten metal poured into the feeder is provided between the feeder and the cavity. By using a mold in which the feeder portion is formed with higher heat insulating properties than the cavity, so that a cooling rate difference in which the cooling rate of the molten metal is slower than the molten metal poured into the cavity is provided. Even if the part is reduced in size, a sufficient riser effect can be obtained, and a cast product with as few sink marks as possible can be obtained. In this case, a forging aluminum alloy is used as the forging metal, the cooling rate of the molten metal poured into the cavity is set to 500 ° C./min or more, and the cooling rate of the molten metal poured into the riser is set to 500 ° C./min. Or the cooling rate of the molten metal poured into the cavity is adjusted so that the interval between the dendritic crystals of the solidified aluminum alloy for forging is less than 25 μm on average, and the molten metal is poured into the riser. By adjusting the cooling rate of the obtained molten metal so that the interval between the dendritic crystals of the solidified aluminum alloy for forging becomes 25 μm or more on average, a cast product with even better appearance can be obtained.

[0008] The molten metal obtained by melting the forging material has poor fluidity as compared with the molten metal obtained by melting the casting material. In addition, when an oxide film is formed on the surface of the molten metal, its fluidity further decreases. For this reason, the molten metal obtained by melting the forging material has poor meltability in the cavity of the mold. In this regard, in the present invention, the molten metal obtained by melting the forging material and the reducing compound are brought into contact with each other in the cavity of the molding die, and the molten metal is cast while reducing the oxide film formed on the surface of the molten metal. For this reason, the oxide film formed on the surface of the molten metal is reduced and disappears, the fluidity of the molten metal becomes good, and the fluidity in the cavity can be improved. As a result, it is possible to easily obtain a cast product made of a forging material, which has been difficult to cast because the meltability in the cavity is poor.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A case where a reduction casting method according to the present invention is performed using a molding die 10 shown in FIG. 1 will be described. A molding die 10 shown in FIG. 1 is a molding die used for gravity casting. The molding die 10 is made of metal, and the lower die 1
This is a split type of 1a and upper die 11b. Such lower mold 11a
The upper mold 11b forms a cavity 11c in which a casting having a desired shape is cast. In the upper mold 11b, a feeder portion 17 is formed between a pouring port 11d for pouring the molten metal and the cavity 11c, and an air vent hole 15 for releasing air in the cavity 11c when the cavity 11c is poured. , 15... Are also formed.

When the casting die 10 is used to pour and cast an aluminum alloy for forging as a metal for forging, for example, an aluminum alloy for forging of the Al—Cu system, so-called duralumin, First, the mold 10
After a magnesium nitrogen compound (Mg ₃ N ₂ ), which is a reducing compound, is introduced into the cavity 11c, a molten aluminum alloy for forging is poured. As described above, the presence of the reducing compound in the cavity 11c of the mold 10 reduces the oxide film formed on the surface of the molten forged aluminum alloy for forging, thereby reducing the surface of the molten metal. Reduce tension. As a result, the fluidity and the fluidity of the molten metal can be improved, and as a result, a cast product made of an aluminum alloy for forging, which has conventionally been difficult to cast, can be easily obtained. Further, since the fluidity of the molten metal is good, the molten metal can be filled in the cavity 11c in a short time. Therefore, the heat dissipation of the mold 10 can be improved, the molten metal filled in the cavity 11c can be rapidly cooled, and the productivity of casting can be significantly improved. In addition, by rapidly cooling the molten metal filled in the cavity 11c, fine crystals are easily precipitated, and the strength of the obtained cast product can be improved. Here, as the aluminum alloy for forging, Al-
Cu system, Al-Cu-Mg system, Al-Mg-Si system, A
An l-Cu-Mg-Zn-based forging aluminum alloy can be used. In particular, the content of copper (Cu) is 5% or less (preferably 4% or less) and / or magnesium (M
An aluminum alloy for forging having a content of g) of 3% or less (preferably 2% or less) can be suitably used.

Incidentally, in casting using the molding die 10 shown in FIG. 1, it is necessary to increase the volume of the feeder portion 17 in order to minimize sink marks and the like of the obtained cast product.
That is, the feeder portion 17 is a portion that secures the molten metal that replenishes the gap on the side of the feeder portion 17 that is generated due to shrinkage accompanying solidification of the molten aluminum alloy forging filled in the cavity 11c. is there. For this reason, even if the molten metal filled in the cavity 11c solidifies, it is necessary that at least a part of the molten metal filled in the riser 17 is not solidified and has fluidity. In this way, in order to make the solidification of the molten metal filled in the feeder portion 17 slower than the solidification of the molten metal filled in the cavity 11c, the shape that the feeder portion 17 is hardly cooled, that is, the columnar shape having a large cross-sectional area, This is because it is advantageous to form the However, the solidified portion of the molten metal filled in the feeder 17 is not a product but a portion separated from the product. Even if it is melted again and reused, energy is lost. Therefore, if the feeder unit 17 can be made as small as possible, it is advantageous in terms of energy.

FIG. 2 shows a reduction casting apparatus capable of miniaturizing the feeder portion 17 of the molding die 10 as much as possible. The reduction casting apparatus shown in FIG. 2 is provided with a forming die 12, which is formed with a cavity 12b connected to a pouring port 12a into which a molten aluminum alloy for forging is poured. I have. On the inner wall surface of the cavity 12b, the metal surface of the metal forming the lower mold 14a and the upper mold 14b made of metal is exposed. The mold 12 is connected to the nitrogen gas cylinder 20 by a pipe 22,
Is opened, nitrogen gas is injected into the cavity 12b from the nitrogen gas inlet 12d, and the cavity 12b
The inside can be substantially a non-oxygen atmosphere as a nitrogen gas atmosphere. The argon gas cylinder 25 is connected to a heating furnace 28 as a generator for generating a metal gas through a pipe 26, and a valve 3 provided in the pipe 26.
By opening 0, argon gas can be injected into the heating furnace 28. The inside of the heating furnace 28 is formed so as to be heatable by a heater 32, and the temperature in the furnace is set to 800 ° C. or higher at which magnesium powder sublimates in order to generate magnesium gas as a metal gas described later. The amount of argon gas injected into the heating furnace 28 can be adjusted by the valve 30 so that the flow rate of the argon gas is also a predetermined flow rate between the valve 30 and the heating furnace 28 of the pipe 26.

The argon gas cylinder 25 is connected to a tank 36 containing magnesium 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 mold 1 via a pipe 42.
2 is connected to the metal gas inlet 12c of the heating furnace 2
The metal gas gasified in 8 is introduced into the cavity 12b through the metal gas inlet 12c. The pipe 42 is also provided with a valve 45. Argon gas is supplied from the argon gas cylinder 25 via the heating furnace 28 to the mold 1.
When injecting into the second cavity 12b, the amount of argon gas injected into the cavity 12b can be adjusted by the valve 45.

The molding die 12 used in the casting apparatus shown in FIG. 2 is, as shown in FIG.
a, the upper mold 14b, and the adapter 18 formed by firing calcium sulfate. The lower mold 14a and the upper mold 14b form a cavity 12b in which a casting having a desired shape is cast. The molten metal poured into the pouring port 12a is provided between the cavity 12b and the pouring port 12a for pouring the molten metal of the forging aluminum alloy formed in the adapter 18.
A hot water path 21 and a feeder section 16 are formed.
Feeder section 16 has an area of a cross section larger than an area product of a cross section of runner 21, and the volume of feeder section 16 is
It is preferably 5 to 20% with respect to the volume of 2b.
A metal gas introduction path 23 from the metal gas introduction port 12 c into which the gasified metal gas is introduced into the heating furnace 28 is connected to the hot water path 21. Exhaust holes 25 are formed in the adapter 18 and the upper mold 14b to exhaust gas in the cavity 12b.
An introduction path 27 for introducing nitrogen gas introduced from the nitrogen gas introduction port 12d into the cavity is formed. As shown in FIG. 3 (b), the exhaust hole 25 or the introduction path 27 is a hole having a circular cross-sectional shape, into which a columnar insert 31 having a rectangular cross-sectional shape is inserted. Through the passages 29, 29,.

In the molding die 12 shown in FIGS. 2 and 3, an adapter 18 formed by firing calcium sulfate is provided with a pouring port 12a, a hot channel 21, a metal gas inlet 12c, a metal gas introducing channel 23, and an exhaust hole 25. Form a part of. The runner 21 and the like need to be formed in accordance with the shape of the cavity 12b and the arrangement of extrusion pins (not shown) for extruding the cast product. 21 can easily be dealt with. Further, the adapter 18 may be made of metal, similarly to the lower mold 14a and the upper mold 14b, but may be formed by firing calcium sulfate.
By using, it is possible to easily form the hot water path 21 and the like. Further, in the molding die 12 shown in FIGS. 2 and 3, the feeder portion 16 is formed with higher heat insulation than the cavity 12b. That is, the inner wall surface of the feeder unit 16 is subjected to a heat insulation treatment such as application of a heat-insulating coating agent, but the inner wall surface of the cavity 12b is formed of a metal lower mold 14a and an upper mold 1a.
4b is a state where the metal surface of the metal forming the molding die 12 is exposed. Here, the heat-insulating coating agent is a coating agent applied to the inner wall surface of the cavity or the like when forming a coating die, and is a coating agent mixed with a high heat-insulating coating agent, for example, ceramic. Molding agents can be used.

As described above, by forming the feeder portion 16 of the molding die 12 with higher heat insulation than the cavity 12b,
As shown in FIG. 4 (a), the cooling rate of the molten metal filled in the riser 16 can be made slower than that of the molten metal filled in the cavity 12b, and the cooling rate between the riser 16 and the cavity 12b is large. A difference can be provided. In FIG. 4A, A
The point is the temperature of the molten metal to be poured into the mold 12, and the point B is the temperature at which the molten metal is completely solidified. Accordingly, a region where the molten metal filled in the feeder unit 16 can flow into the cavity 12b and exhibit a successful feeder effect is a region indicated by oblique lines in FIG. On the other hand, the molding die 10 shown in FIG. 1 also applies a heat-insulating coating agent to the inner wall surface of the feeder unit 17 and the cavity 11c. By making the coating mold thicker than the inner wall surface of the molten metal 11c, as shown in FIG. 4B, the cooling speed of the molten metal filled in the feeder unit 17 is made slower than the cooling speed of the molten metal filled in the cavity 11c. it can. However, the mold 1 shown in FIG.
At 0, as shown in FIG. 4 (b), the cooling rate difference is smaller than that of the molding die 12 shown in FIGS. 2 and 3, and the molten metal of the feeder 17 flows into the cavity 11c and is effective. The area where the riser effect can be obtained is also narrow. On the other hand, in the molding die 12 shown in FIGS. 2 and 3 of FIG. 4A, the cooling rate difference is larger than that of the molding die 10 shown in FIG. Since the region in which the feeder effect can be obtained is wide, even if the feeder portion 16 is downsized, a solidification time difference between the molten metal filled in the feeder portion 16 and the molten metal filled in the cavity 12b can be secured.

As shown in FIG. 4A, in order to ensure a sufficient solidification time difference between the molten metal filled in the riser 16 and the molten metal filled in the cavity 12b, the molten metal poured into the cavity 12b is required. At a cooling rate of 500 ° C./min or more (more preferably 700 ° C./min or more),
At a cooling rate of less than 500 ° C./min (more preferably 300 ° C./min or less). In particular, it is preferable to adjust the difference between the two cooling rates to be 200 ° C./min or more. Here, the molten metal of the forging aluminum alloy is used as the molten metal, and the cooling rate of the molten metal poured into the cavity 12b and the cooling rate of the molten metal poured into the feeder unit 16 are variously changed, so that the cavity 12b and the molten metal are cooled. A part of the aluminum filled and solidified in the riser 16 was sampled, and the distance between dendrites (dendrites) was measured by an electron microscope. The result is shown in FIG. FIG. 5 shows the cooling rate on the horizontal axis,
The interval between dendrites of the solidified aluminum alloy for forging (dendrites) is shown on the vertical axis as “DASII value”. As is clear from FIG. 5, the spacing between dendrites of the forging aluminum alloy filled and solidified in the cavity 12b whose cooling rate was adjusted to 500 ° C./min or more was less than 25 μm on average, and Speed 5
The interval between the dendrites of the aluminum alloy for forging filled and solidified in the riser 16 adjusted to less than 00 ° C./min is 25 μm or more on average. The reduction in the distance between the dendrites of the aluminum alloy for casting is advantageous because the crystal structure of the aluminum alloy for forging becomes denser and the mechanical strength and the like of the casting made of the aluminum alloy for forging obtained can be improved. It is. For this reason, the interval between dendrites of the aluminum alloy for forging filled and solidified in the cavity 12b is preferably 23 μm or less, particularly preferably 20 μm or less. In addition, in the part of the forging aluminum alloy filled and solidified in the feeder portion 16, the interval between dendrites (dendrites) is larger than that of the aluminum solidified by filling the cavity 12b, and the mechanical strength and the like are also reduced. Although it is inferior, there is no problem because it is cut off from the part which is filled into the cavity 12b and becomes a solidified product.

When casting a casting made of an aluminum alloy for forging using the casting apparatus shown in FIGS. 2 and 3,
First, the valve 24 is opened, nitrogen gas is injected into the cavity 12b of the mold 12 from the nitrogen gas cylinder 20 via the pipe 22, and the air in the cavity 12b is purged with nitrogen gas. The air in the cavity 12b is
2 are exhausted from the exhaust holes 25, 25,.
The inside of 2b can be a nitrogen gas atmosphere and can be a substantially non-oxygen atmosphere. Thereafter, the valve 24 is closed once.
While the air in the cavity 12b of the mold 12 is being purged, the valve 30 is opened, and argon gas is injected into the heating furnace 28 from the argon gas cylinder 20.
The inside of 8 is made anoxic. Next, the valve 30 is closed,
The valve 40 is opened, and the tank 36 is opened by the argon gas pressure.
The magnesium powder in the heating furnace 28 together with the argon gas
Send in. The heating furnace 28 is heated by the heater 32 to a furnace temperature of 800 ° C. or more at which the magnesium powder sublimes. For this reason, the magnesium powder sent to the heating furnace 28 is sublimated into magnesium gas.

Next, the valve 40 is closed, the valves 30 and 45 are opened, and while adjusting the pressure and flow rate of the argon gas, the pipe 42 and the metal gas inlet 12 of the molding die 12 are adjusted.
c, a magnesium gas is injected into the cavity 12b through the metal gas introduction path 23, the hot water path 21 and the feeder unit 16.
After injecting magnesium gas into the cavity 12b,
The valve 45 is closed and the valve 24 is opened, and nitrogen gas is injected into the cavity 12b from the nitrogen gas inlet 12d via the introduction paths 27, 27,. Thus, by injecting nitrogen gas into the mold 12, the magnesium gas and the nitrogen gas are reacted in the cavity 12b to generate a magnesium nitrogen compound (Mg ₃ N ₂ ). This magnesium nitrogen compound precipitates as a powder on the inner wall surface of the cavity 12b. When the nitrogen gas is injected into the cavity 12b, the pressure and the flow rate of the nitrogen gas are appropriately adjusted. It is also preferable that the nitrogen gas is preheated so that the nitrogen gas and the magnesium gas easily react with each other so that the temperature of the mold 12 is not lowered. Reaction time is 5 seconds ~
It may be about 90 seconds (preferably about 15 seconds to 60 seconds).
Even if the reaction time is longer than 90 seconds, the mold temperature of the mold 12 decreases, and the reactivity tends to decrease.

With the magnesium nitrogen compound adhered to the inner wall surface of the cavity 12b, a molten aluminum alloy for forging is poured from the pouring port 12a, and the molten metal is poured into the cavity 12b via the runner 21 and the feeder section 16. Inject.
The injection of the molten metal is continued until the cavity 12b, the feeder unit 16, and the pouring port 12a are filled with the molten metal. During the injection of the molten metal, the molten metal poured into the cavity 12b comes into contact with the magnesium nitrogen compound attached to the inner wall surface of the cavity 12b, and the magnesium nitrogen compound deprives the oxide film on the surface of the molten metal of oxygen. Thereby, the molten metal surface is reduced to a pure aluminum alloy for forging. Further, the oxygen remaining in the cavity 12b reacts with the magnesium nitrogen compound to become magnesium oxide or magnesium hydroxide and is taken into the molten metal. Since the amount of magnesium oxide and the like thus produced is a small amount and a stable compound, it does not adversely affect the quality of the obtained aluminum casting. As described above, since the magnesium nitrogen compound removes oxygen from the oxide film on the surface of the molten aluminum alloy for forging to form a pure aluminum alloy for forging, casting can be performed without forming an oxide film on the surface of the molten aluminum alloy. For this reason, it is possible to prevent the surface tension of the molten metal from being increased by the oxide film during the casting process, and it is possible to improve the wettability, fluidity, and flowability of the molten metal. As a result, it is possible to obtain a good cast product which is excellent in the transferability (smoothness) determined with the inner wall surface of the cavity 12b and does not cause hot water wrinkles or the like.

The cavity 12b and the feeder 16
Although the molten metal filled in the water and the like is cooled and solidified, a heat insulating coating agent is applied to the inner wall surface of the feeder unit 16 to perform a heat insulating treatment. On the other hand, on the inner wall surface of the cavity 12b, the metal surface of the metal forming the lower mold 14a and the upper mold 14b made of metal is exposed. Therefore, the cavity 12b
As shown in FIG. 4A, the cooling rate of the molten metal charged into the feeder 16 is faster than that of the molten metal filled in the feeder unit 16. Therefore,
The molten metal filled in the cavity 12b is solidified earlier than the molten metal filled in the feeder unit 16. When the molten metal in the cavity 12b solidifies, a gap is formed on the side of the feeder 16 of the cavity 12b due to shrinkage accompanying the solidification of the molten metal. On the other hand, since the molten metal still remains in the feeder portion 16 having a cooling rate lower than that of the cavity 12b, the residual molten metal in the feeder portion 16 flows into the gap toward the feeder portion 16 side of the cavity 12b, and causes sink marks and the like. Not a good casting can be cast. Further, on the inner wall surface of the cavity 12b,
Since a coating agent capable of improving the fluidity or the like of the molten metal having the oxide film formed on the surface is not applied, a cast product having an extremely smooth surface can be obtained.

As described above, the cooling rate of the feeder section 16 is controlled by applying the heat-insulating mold to the inner wall surface of the cavity 12b by applying the heat-insulating mold to the inner wall surface. Feeder 16 and cavity 12
Since a sufficient solidification time difference can be given to the molten metal filled in b, the volume of the riser 16 can be reduced. As a result, the columnar portion protruding and separated from the cast product can be made as small as possible, and as a result, the yield of the molten metal poured into the mold 12 can be improved, and operational and energy losses are reduced as much as possible. it can.

In the molding die 12 shown in FIGS. 2 and 3, the feeder portion 16 is formed in the upper die 14b. The portion formed by solidifying the molten metal filled in the feeder portion 16 is a cast product. It is not necessary to form the upper die 14b made of metal because the cut portion is cut away from the upper die 14b. For this reason, the feeder section 16 may be formed over the adapter 18 formed by firing calcium sulfate and the upper mold 14b. In this case, the adapter 18 formed by calcining calcium sulfate is a metal lower mold 1.
As shown in FIG. 6, the volume of the portion of the feeder 16 formed in the adapter 18 was formed in the upper die 14b because the heat conductivity was lower than that of the upper mold 14b. So as to be larger than the volume of the feeder 16
By forming the feeder 16, the metal lower mold 14 can be formed without applying a heat-insulating coating agent to the inner wall surface of the feeder 16.
The heat insulating property can be improved more than the cavity 12b formed in the a and 14b.

As shown in FIG. 7, a metal upper die 14b and a lower die 14 are provided between the adapter 18 and the upper die 14b.
Insertion plate 3 having a lower thermal conductivity than a, that is, better heat insulation
7 may be inserted to form the feeder 16 over the insertion plate 37 and the upper die 14b. The adapter 18 and the insertion plate 37 are detachable from each other, and the insertion plate 37 is also detachable from the upper die 14b. As the insert plate 37, an insert plate formed by firing calcium sulfate can be used, and the volume of the feeder section 16 formed on the insert plate 37 is, as shown in FIG. So that the volume of the feeder 16 is larger than the volume of the feeder 16
6, the metal lower dies 14a, 14a can be formed without applying a heat-insulating coating material to the inner wall surface of the feeder unit 16.
The heat insulating property can be improved more than the cavity 12b formed in b.

The molding die 1 shown in FIGS. 2, 3, 6 and 7
In 2, the adapter 18 and the insert plate 37 are formed by firing calcium sulfate, but may be made of metal or ceramic. However, when the adapter 18 or the insert plate 37 which substantially forms the feeder portion 16 is made of metal, a heat-insulating mold is applied to the inner wall surface of the feeder portion 16 and the heat insulation of the feeder portion 16 is performed. It is necessary to improve the performance over the cavity 12b. The heating furnace 28 shown in FIG.
As shown in FIG.
c, or may be formed by reacting magnesium gas as a metal gas gasified in the heating furnace 28 with nitrogen gas as a reactive gas that reacts with the metal gas to reduce magnesium nitrogen as a reducing compound. The reaction tank 39 for producing the compound (Mg ₃ N ₂ ) is connected to the metal gas inlet 12 of the mold 12.
It may be provided directly above c. In the above description, a casting method using a molten aluminum alloy for forging has been described, but the present invention is also applicable to a casting method using a molten metal such as an iron alloy for forging.

[0026]

According to the present invention, casting can be performed using a molten metal of a forging metal, which has conventionally been difficult to cast, and compared with a cast product obtained using a molten metal of a casting metal. Thus, it is possible to obtain a cast product having improved strength and toughness.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an example of a molding die used in a reduction casting method according to the present invention.

FIG. 2 is a schematic diagram illustrating an example of a casting apparatus for performing a reduction casting method according to the present invention.

FIG. 3 is a cross-sectional view for explaining a molding die used in the casting apparatus shown in FIG.

4 is a graph for explaining a difference between a feeder of the forming die shown in FIG. 2 and a feeder of the forming die shown in FIG. 1;

FIG. 5 is a graph showing a relationship between a cooling rate of a melt of an aluminum alloy for forging and an interval between dendritic crystals of a solidified aluminum alloy for forging.

FIG. 6 is a cross-sectional view illustrating another example of the molding die shown in FIG.

FIG. 7 is a sectional view illustrating another example of the molding die shown in FIG.

FIG. 8 is a sectional view of a molding die used in a conventional casting method.

FIG. 9 is a state diagram of an aluminum alloy for casting.

FIG. 10 is a state diagram of an aluminum alloy for forging.

[Explanation of symbols]

 10, 12 Mold 11d, 12a Pouring port 11c, 12b Cavity 16, 17 Feeder unit 21 Runner

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) C22C 21/02 C22C 21/02 21/06 21/06 21/10 21/10 21/12 21/12 ( 72) Inventor Akira Sunohara 840, Kokubu, Ueda-shi, Nagano Nissin Kogyo Co., Ltd. PB05

Claims (8)

[Claims] When casting a casting having a desired shape while bringing a molten metal of a metal poured into a cavity of a mold into contact with a reducing compound and reducing an oxide film formed on the surface of the molten metal. A reduction casting method, wherein a molten metal obtained by melting a forging metal is used as the molten metal. 2. As a metal for forging, Al—Cu based, Al
-Cu-Mg type, Al-Cu-Mg-Zn type or Al-
The reduction casting method according to claim 1, wherein an Mg-Si-based forging aluminum alloy is used. 3. An aluminum alloy containing copper (Cu) and / or magnesium (Mg) as a metal for forging, wherein the content of said copper (Cu) is 5% or less and / or said magnesium (Mg). The reduction casting method according to claim 1 or 2, wherein a forging aluminum alloy having a content of 3% or less is used. 4. The reduction casting method according to claim 1, wherein an aluminum alloy for forging is used as the metal for forging, and the cooling rate of the molten metal poured into the cavity is 500 ° C./min or more. . 5. A forging aluminum alloy is used as the forging metal, and the cooling rate of the molten metal poured into the cavity is adjusted so that the interval between dendritic crystals of the solidified forging aluminum alloy is less than 25 μm on average. The reduction casting method according to any one of claims 1 to 4, wherein the method is adjusted to: 6. A molten metal poured into a feeder between a feeder for pouring a molten metal and a cavity as a molding die, and between the feeder and the cavity. 2. The mold according to claim 1, wherein the feeder portion is formed to have a higher heat insulating property than the cavity so that a cooling rate difference in which the cooling rate of the molten metal is lower than that of the molten metal poured into the cavity is provided. Reduction casting method. 7. An aluminum alloy for forging is used as a metal for forging, the cooling rate of the molten metal poured into the cavity is set to 500 ° C./min or more, and the cooling rate of the molten metal poured to the riser is 500 ° C. 7. The reduction casting method according to claim 6, wherein the rate is less than / min. 8. An aluminum alloy for forging is used as a metal for forging, and the cooling rate of the molten metal poured into the cavity is adjusted so that the interval between dendritic crystals of the solidified aluminum alloy for forging is less than 25 μm on average. And the cooling rate of the molten metal poured into the riser is adjusted so that the interval between the dendritic crystals of the solidified aluminum alloy for forging is 2 on average.
8. The method according to claim 6, wherein the thickness is adjusted to 5 μm or more.
The reduction casting method as described.