JPH081303A - Stoke for differential pressure casting - Google Patents

Abstract

PURPOSE:To provide a stoke for differential pressure casting, in which a mechanical strength can be improved, by removing oxide, etc., in molten metal. CONSTITUTION:On the inner surface of a tubular member forming the flowing passage of the molten metal, a filter member 6a having 80-90% void ratio and 5-15kg/cm<2> of transverse rupture strength to at least one side surface of a fine filter 6a having 40-60% void ratio and 50-120kg/cm<2> of transverse rupture strength, is fitted. By this method, the product yield is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a casting stalk used for differential pressure casting of molten metal such as aluminum or its alloy.

[0002]

2. Description of the Related Art Recently, from the viewpoint of energy saving, weight reduction of automobile parts has been promoted, and aluminum wheels have come to be used for automobile disc wheels instead of conventional steel wheels. In addition, the demand for weight reduction of automobile disc wheels has become even more intense with the aim of further saving energy, and it has become necessary to study thinning of aluminum wheels in order to reduce their weight. Here, mechanical strength is insufficient if the aluminum wheel is simply made thin, and therefore it is essential to improve the mechanical strength of the material itself in order to reduce the thickness.

In order to improve the mechanical strength of the aluminum wheel, various methods such as changing the material and changing the manufacturing method can be considered. The simplest method among them is to reduce the amount of foreign substances such as non-metallic inclusions in the product so that the material has a theoretical strength as close as possible.

In order to reduce the amount of foreign matters such as non-metallic inclusions in the product, it is necessary to use a material with few impurities or remove the inclusions in the molten metal. However, when using a material containing few impurities, the raw material itself is very expensive, and thus the price of the obtained product is very high.

On the other hand, the method of removing the inclusions in the molten aluminum by using the filtering member is expected to be quite effective in spite of its simple structure. Therefore, it is generally used in low pressure casting. . For example, actual development 59-
As disclosed in Japanese Patent No. 68659, a method of removing inclusions in a molten aluminum by arranging a wire mesh in the vicinity of the pouring inlet of the stalk is performed.

[0006]

However, although the above-mentioned conventional method can remove coarse inclusions,
Fine inclusions not only pass through the wire mesh and adhere to stalks, sprues, etc., but also reach the inside of the cavity in the mold and mix into the cast product, forming coarse inclusions and shrinking. There is a problem in that casting defects such as cavities occur and the strength of the product is reduced due to the defects.

Therefore, in order to prevent such inclusion of coarse inclusions, fine wire mesh or a ceramic filter having a fine pore size has been used. Such a filter has a porosity of 80.
Foam filters with a 90% strength and a flexural strength of 6-12 kg / cm ² are commercially available. In fact, if a filter with a fine pore size is used, fine inclusions in the product will certainly decrease, and the strength of the product will increase accordingly. However, since the filter has fine meshes, coarse inclusions as well as fine inclusions are collected, so that the filter is easily clogged, and there is a problem that it cannot withstand long-term use.

Therefore, the object of the present invention is to remove both coarse inclusions and fine inclusions in the molten metal, and to extend the period of use as compared with the prior art by using the differential pressure casting stalk. Is to provide.

[0009]

As a result of various studies on the method of removing the inclusions, the present inventor has found that a metal member can be formed by mounting a filter member in which a coarse filter is adhered to at least one surface of a fine filter in a stalk. It was found that inclusions and the like can be reliably removed over a long period of time.

That is, the present invention has a tubular member that forms a flow path of molten metal, and a filter member in which a coarse filter is adhered to at least one surface of a fine filter mounted on the inner surface of the tubular member, The fine filter has a porosity of 40 to 60% and a bending strength of 50 to 120 kg.
/ cm ² , and the porosity of the coarse filter is 70-9.
It is characterized by 0% and a bending strength of 5 to 15 kg / cm ² .

In the present invention, a coarse filter may be provided on both sides of the fine filter. When the tubular member is made of Sialon, the thermal expansion coefficient of the fine filter is 3 × 10 ^-6 ~
9 × 10 ⁻⁶ / ° C., the coefficient of thermal expansion of the coarse filter is 3
It is desirable that it is × 10 ^{-6 to} 9 × 10 ^-6 / ° C. The fine filter has an average pore size of 0.3 to 1.0 mm and a thickness of 5 to 1
It is desirable that it is 5 mm. Further, it is desirable that the coarse filter has an average pore diameter of 1 to 5 mm and a thickness of 10 to 50 mm.

It is desirable that the fine filter and / or the coarse filter is formed of one or more of alumina, cordierite, mullite and silicon carbide. Of the inner peripheral surface of the tubular member for mounting the filter member,
It is desirable to have a structure in which the inner diameter of the portion where the filter member is mounted is larger than the inner diameter of the other portion, or a structure in which the outer peripheral surface of the filter member is formed in a tapered shape in the thickness direction.

Also, in order to absorb the difference in the amount of thermal expansion and to prevent the passage of unfiltered molten metal, packing is provided at least at a part between the outer peripheral edge of the filter member and the inner peripheral surface of the tubular member. Is desirable. Furthermore, a metal sheet made of a material similar to that of the molten metal may be provided on at least a part of the outer peripheral surface of the filter member.

[0014]

In the present invention, since the coarse filter is brought into close contact with at least one surface of the fine filter, coarse substances among the inclusions that move during pressurization of the molten metal should be removed by the coarse filter. Since fine particles are removed by the fine filter, clogging of the fine filter is less likely to occur, and thus the fine filter can be used for a long period of time.

[0015]

The present invention will be described below with reference to the drawings. FIG. 1 shows an example of a low pressure casting machine equipped with the stalk of the present invention. In the figure, reference numeral 1 is a cavity conforming to the shape of the cast product, and a mold 2 including an upper mold 2a, a lower mold 2b and a horizontal mold 2c.
Is formed by. The lower mold 2b has a sprue 3 communicating with the cavity 1. The stalk 4 has a tubular member 5 and a filter member 6 attached to the lower end thereof,
The upper end of the tubular member 5 is connected to the sprue 3 of the mold, the lower end is immersed in the molten metal 8 in the holding furnace 3, and the molten metal surface 10 is held above the filter member 6.

According to this low pressure casting machine, casting is performed as follows. When a pressure (indicated by an arrow in the figure) is applied to the molten metal 7 in the furnace 6, the molten metal surface 9 descends, and accordingly, the molten metal surface 10 in the tubular member 5 starts to rise, and the filter member It flows into the cavity 1 in the mold 2 via 6 and the sprue 3. The inflowing molten metal is cooled by the mold 2 and begins to solidify. Pressure is applied to the molten metal surface 9 for a certain period of time, and solidification proceeds in the cavity 1 under pressure. With the sprue 3 almost solidified, the pressure on the molten metal surface 9 is removed, and the pressure is exhausted as the molten metal surface 9 rises. The molten metal in the tube descends, and one casting cycle ends.

Here, the filter member 6 has a fine filter 6a and a coarse filter 6b adhered to the lower surface thereof. In this example, since the coarse filter is adhered to at least one side of the fine filter, among the inclusions that move during pressurization, the coarse one can be removed by the one side coarse filter, and the fine one can be removed by the fine filter. Therefore, since the fine filter is less likely to be clogged, it can be used for a long period of time.

FIG. 2 shows another example of the low pressure casting machine provided with the stalk of the present invention. In the figure, reference numeral 1 is a cavity conforming to the shape of a cast product, which is formed by a mold 2 including an upper mold 2a, a lower mold 2b, and a horizontal mold 2c. The lower mold 2b has a sprue 3 communicating with the cavity 1. The stalk 4 has a tubular member 5 and a filter member 6 attached to the lower end thereof, the upper end of the tubular member 5 is connected to the gate 3 of the mold, and the lower end is immersed in the molten metal 8 in the holding furnace 3,
The molten metal surface 10 is held below the filter member 6.

With this low-pressure casting machine, casting is performed as follows. When a pressure (indicated by an arrow in the drawing) is applied to the molten metal 7 in the furnace 6, the molten metal surface 9 descends, and accordingly, the molten metal surface 10 in the tubular member 5 starts to rise, and the filter member 6 And it flows into the cavity 1 in the mold 2 via the gate 3. The inflowing molten metal is cooled by the mold 2 and begins to solidify. Pressure is applied to the molten metal surface 9 for a certain period of time, and solidification proceeds in the cavity 1 under pressure. When the sprue 3 is about to solidify, the pressure on the molten metal surface 9 is removed, and the pressure is exhausted as the molten metal surface 9 rises. The unsolidified molten metal 10 in the tube descends through the filter member 6 to complete one casting cycle.

Here, the filter member 6 has a fine filter 6a and a coarse filter 6b adhered to both surfaces thereof. In this example, since the coarse filter is adhered to both sides of the fine filter, among the inclusions that move during pressurization, the coarse one can be removed by the coarse filter on the lower surface, and the fine one can be removed by the fine filter. Therefore, the fine filter is less likely to be clogged, and the coarse solidified film formed on the inner surface of the stalk that moves when the pressure drops after the completion of pouring and solidification is removed by the coarse filter on the top surface Since it is filtered out, it can be used for a long time.

As the filter of the present invention, it is possible to use a filter formed of alumina, cordierite, mullite, ceramics such as silicon carbide in a porous form. Such a filter is, for example, formed by molding raw material powder into a predetermined shape,
Then, it can be made by sintering. The properties of the filter can be adjusted by adjusting the molding conditions (pressure) and the sintering conditions (atmosphere, temperature).

The fine filter used in the present invention has a porosity of 40 to 60% and a bending strength of 50 to 120 kg / c.
m ² and coefficient of thermal expansion are 3 × 10 ^{−6 to} 9 × 10 ⁻⁶ / ° C.
If the porosity of the fine filter is less than 40%, clogging tends to occur, and if it exceeds 60%, minute inclusions (about several μm) cannot be removed.

If the bending strength is less than 50 kg / cm ² , even if some of the pores are clogged with inclusions, they tend to be damaged, and
If it exceeds 20 kg / cm ² , the porosity is greatly reduced and clogging is likely to occur.

The coefficient of thermal expansion must be taken into consideration when the tubular member is made of ceramics. That is, when the thermal expansion coefficient of the filter is larger than that of the tubular member, the tubular member is likely to be damaged during casting. In order to prevent breakage of the tubular member, the difference in the coefficient of thermal expansion between the two should be minimized, specifically, the difference in coefficient of thermal expansion should be 4 × 10 ^−6.
It is preferably below / ° C. For example, when the tubular member is formed of sialon (coefficient of thermal expansion 3 × 10 ^{−6 to} 5 × 10 ⁻⁶ / ° C.), the thermal expansion coefficient of the fine filter is 3 × 1.
It is preferably in the range of 0 ^{−6 to} 9 × 10 ⁻⁶ / ° C.

Further, in the present invention, the average pore size is 0.3 to
It is preferable to use a fine filter having a thickness of 1.0 mm and a thickness of 5 to 15 mm. The average pore size of the fine filter is 0.3
If it is less than mm, clogging tends to occur, and even if the hole diameter is further reduced, the effect of collecting inclusions does not increase. If the pore size is larger than 1.0 mm, the effect of collecting inclusions is small. Further, if the thickness of the fine filter is thinner than 5 mm, the fine filter is easily cracked, and if thicker than 15 mm, the flow path resistance becomes large, and the hot water flow defect occurs.

The coarse filter used in the present invention has a porosity of 70 to 90%, a bending strength of 5 to 15 kg / cm ² , and a thermal expansion coefficient of 3 × 10 ^{-6 to} 9 × 10 ^-6 / ° C. It is characterized by If the porosity of the coarse filter is less than 70%, clogging tends to occur, and if it exceeds 90%, minute inclusions (about several μm) cannot be removed. If the bending strength is less than 5 kg / cm ² , even if some of the inclusions are clogged with pores, it will be easily damaged, and if it exceeds 15 kg / cm ² , the porosity is significantly reduced and clogging is prevented. It tends to occur.

The thermal expansion coefficient is preferably 3 × 10 to 9 × 10 ⁻⁶ / ° C. for the same reason as in the case of the fine filter. The coarse filter according to the present invention has an average pore size of 1 to
It is preferable to use one having a thickness of 5 mm and a thickness of 10 to 50 mm. This is because if the average pore diameter is less than 1 mm, it is difficult for the molten metal to flow, and if the pore diameter is greater than 5 mm, the effect of preventing inflow of fine inclusions is lost. This is because if the thickness is less than 10 mm, there is a problem in life, and if it is more than 50 mm, the flow path resistance becomes large.

The filter member used in the present invention has a spherical bottom surface as shown in FIG. 3, so that the oxide film does not completely adhere to it, so that the oxide film is easily peeled off when the molten metal falls. Further, in the present invention, it is desirable that the above filter member is attached to the tubular member as follows.

That is, as shown in FIG. 4, the tubular member 5
Of the inner diameter of the filter member 6, the inner diameter of the portion to which the filter member 6 is attached is larger than the inner diameter of the other portion, or the outer peripheral surface of the filter member 6 is formed in a taper shape in the thickness direction as shown in FIG. With the structure, the filter member 6 can be firmly mounted on the inner peripheral surface of the tubular member 5, and the mounting work becomes easy.

Alternatively, as shown in FIG. 6, a packing 11 made of a composite ceramic is mounted between the end surface of the filter member 6 and the tubular member 5, or as shown in FIG. 7, the outer peripheral surface of the filter member 6 and the tubular member 5. By mounting the packing 11 between the inner peripheral surface of 5 and the inner peripheral surface of 5, the molten metal that does not pass through the filter is prevented from flowing into the mold side, and the packing 11
Can serve as a cushioning material and prevent the filter member 6 from cracking.

When the filter member 6 is always immersed in the molten metal for use, a part of the outer peripheral surface of the filter member 6 (the outer peripheral surface of 6b) and the inner peripheral surface of the tubular member 5 are used as shown in FIG. A metal (Al) sheet 12 made of the same type of material as the molten metal (Al alloy) is attached between the surface and the outer peripheral surface of the filter member 6 and the inner peripheral surface of the tubular member 5 as shown in FIG. It can be used by mounting the metal sheet 12 between them. In this case, the filter member 6 is fixed to the tubular member 5 only at the start of use, and the metal sheet 12 is eluted into the molten metal during use, so that the filter member 6 is loosely fitted in the tubular member 5, It is possible to prevent the filter member 6 or the tubular member 5 from being damaged due to the difference in expansion amount due to the difference in thermal expansion coefficient between the filter member 6 and the tubular member 5. In this case, the filter member 6 is loosely fitted in a predetermined position of the tubular member due to the buoyancy caused by the difference in specific gravity between the molten aluminum and the filter member.

Further, when the outer peripheral portion of the upper surface of the filter member 6 is an R-shaped processed portion 13 as shown in FIG.
In the case of the chamfered portion 14, as shown in 0b), the attachment portion of the filter member 6 of the tubular member 5 is also processed according to the shape of the outer peripheral portion of the upper surface of the filter member 6. By performing such processing, stress concentration at the filter mounting portion is relaxed, and an expensive tubular member can be used for a long period of time. Furthermore, for the purpose of stress relaxation, a groove 15 for stress relaxation can be provided in the filter mounting portion as shown in FIG.

Next, an Al--Si alloy (JI
S: AC4CH material), the melt temperature is 710 ° C., the furnace pressure is 0.6 kg / cm ² , the mold temperature is 450 ° C., and the inner diameter is 1
Various filter members shown in Table 1 were mounted on a ceramic stalk having a diameter of 00 mm and an outer diameter of 120 mm, and an aluminum wheel was cast by the low pressure casting machine shown in FIG. 1 to perform a comparative test.

[0034]

[Table 1]

Table 2 shows the inclusion removal rate of the filter used in the above test and the mechanical properties of the test piece cut out from the aluminum wheel obtained by the above test.

[0036]

[Table 2]

As is clear from Table 2, by using the stalk of the present invention, it is possible to obtain a product having improved mechanical properties as compared with the case of using the conventional stalk, and the service life of the filter. Can be extended.

[0038]

As described above in detail, by using the differential pressure casting stalk of the present invention, it becomes possible to reliably remove foreign matters such as inclusions over a long period of time as compared with the conventional one. It is possible to obtain a cast product having improved mechanical strength. In addition, this also makes it possible to significantly improve the product yield.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing an example of a low pressure casting machine.

FIG. 2 is a schematic sectional view showing an example of a low pressure casting machine.

FIG. 3 is an enlarged sectional view of a main part of a stalk showing an embodiment of the present invention.

FIG. 4 is an enlarged sectional view of a main part of a stalk showing another embodiment of the present invention.

FIG. 5 is an enlarged sectional view of a main part of a stalk showing another embodiment of the present invention.

FIG. 6 is an enlarged cross-sectional view of a main part of a stalk showing another embodiment of the present invention.

FIG. 7 is an enlarged sectional view of a main part of a stalk showing another embodiment of the present invention.

FIG. 8 is an enlarged cross-sectional view of a main part of a stalk showing another embodiment of the present invention.

FIG. 9 is an enlarged sectional view of a main part of a stalk showing another embodiment of the present invention.

FIG. 10 is an enlarged sectional view of a main part of a stalk showing another embodiment of the present invention.

FIG. 11 is an enlarged sectional view of a main part of a stalk showing another embodiment of the present invention.

[Explanation of symbols]

1 ... Cavity 2 ... Mold 3
… Gate 4… Stoke 5… Tubular member 6
... filter member 7 ... furnace 8 ... molten metal 9
… Bathing surface 10… Bathing surface 11… Packing 1
2 ... Metal sheet 13 ... R processing section 14 ... Chamfer processing section 1
5 ... groove

Claims (11)

[Claims] 1. A tubular member for forming a flow path for molten metal,
A filter member in which a coarse filter is adhered to at least one surface of a fine filter mounted on the inner surface of the tubular member, and the fine filter has a porosity of 40.
-60%, flexural strength is 50-120 kg / cm ² , and the coarse filter has a porosity of 70-90% and a flexural strength of 5-15 kg / cm ^2. Stoke for casting. 2. The differential pressure casting stalk according to claim 1, wherein the coarse filter is provided on both surfaces of the fine filter. 3. The tubular member is made of Sialon, and the thermal expansion coefficient of the fine filter is 3 × 10 ^{−6 to} 9 × 10 ^−6.
/ ° C. The differential pressure casting stalk according to claim 1 or 2. 4. The tubular member is made of Sialon, and the thermal expansion coefficient of the coarse filter is 3 × 10 ^{−6 to} 9 × 10 ⁻⁶ /
The differential pressure casting stalk according to any one of claims 1 to 3, which is at a temperature of ° C. 5. The fine filter has an average pore size of 0.3 to
The differential pressure casting stalk according to any one of claims 1 to 4, which has a thickness of 1.0 mm and a thickness of 5 to 15 mm. 6. The coarse filter has an average pore size of 1 to 5 m.
The differential pressure casting stalk according to any one of claims 1 to 5, wherein m and thickness are 10 to 50 mm. 7. The differential pressure according to claim 1, wherein the fine filter and / or the coarse filter is made of any one or more of alumina, cordierite, mullite and silicon carbide. Stoke for casting. 8. The inner peripheral surface of the tubular member, wherein the inner diameter of a portion where the filter member is mounted is larger than the inner diameters of other portions. Stoke for differential pressure casting described in. 9. The differential pressure casting stalk according to claim 1, wherein an outer peripheral surface of the filter member is formed in a taper shape in a thickness direction. 10. The differential pressure according to claim 1, wherein packing is provided at least at a part between an outer peripheral edge of the filter member and an inner peripheral surface of the tubular member. Stoke for casting. 11. The differential pressure casting according to claim 1, wherein a metal sheet made of the same material as the molten metal is provided on at least a part of the outer peripheral surface of the filter member. For stoke.