JPH11285782A - Ceramic filter and method for filtration of molten metal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a filter having excellent thermal impact resistance and corrosion resistance by interposing the filter of a cylindrical three-dimensional network skeleton structure having internal open cells into a passage where molten metal is poured from a sprue into a cavity. SOLUTION: A filter body is obtd. by adhering a ceramic slurry to a synthetic resin foam having no cellular films and firing the same, thereby carbonizing away the synthetic resin foam by firing and is formed of ceramics of >=1,000 deg.C in m.p. or sublimation point. The bulk sp. gr. thereof is 0.3 to 0.8, the number of pores per straight line 2.5 cm is 3 to 40 pieces and the void volume is >=65%. The molten metal flows through the inside of a sprue rod 21 and a runner 22 from the spure 20, into an annular molten metal path 30 and flows through the three-dimensional internal spaces from the outer side of the peripheral wall part 11 of the filter body 10, by which impurities in the molten metal are removed. The molten metal subjected to the filtration flows into the hollow part 12 of the filter body 10 and flows to the mold cavity. The molten metal is thus filtered rapidly with good efficiency while the fluidity thereof is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic filter and a method for filtering molten metal, which are preferably used for filtering molten iron-based metal.

[0002]

2. Description of the Related Art Conventionally, a three-dimensional network skeleton structure having an internal communication space, for example, a ceramic foam obtained from a synthetic resin foam, has been made of a non-ferrous metal such as magnesium, aluminum, copper, or iron. It is useful as a filter material for molten metal such as ductile, gray cast iron, cast steel SUS, etc. of a system casting, and a filter having a flat plate or disk shape is used.

[0003] In this case, the amount of filtration per non-ferrous molten metal differs from that of an iron-based molten metal at one time. Used in the ton range. In this case, the non-ferrous system preheats the filter, whereas the ferrous system generally uses the filter without preheating. For this reason, in particular, for iron-based filters, it is required to use a ceramic material with excellent thermal shock resistance and a filter with low passage resistance, and use silicon carbide as the material, and a filter with a relatively small number of holes as a measure against passage resistance. Is used. However, this type of filter has a problem in strength when the thickness of the filter is reduced and the passage resistance is further reduced. Further, since filtration of several tons of molten metal takes one minute or more, there is also a problem of corrosion resistance. This erosion was caused by the reaction between silicon carbide and iron, and the skeleton was eroded by pouring for more than 1 minute, and was not usable. In order to prevent this, a method of coating the skeleton surface with alumina which is difficult to react with iron is known (Japanese Patent Application Laid-Open No. 5-51278), but it is still insufficient.

[0004] Furthermore, a method of increasing the surface area for shortening the pouring time is conceivable. However, since the filter is not preheated, the temperature of the hot water tends to decrease, leading to a poor flow of the hot water and a phenomenon of being damaged by thermal shock. Was. To prevent these, the size of the filter was reduced, and several gates were provided to disperse the impact received by each filter. However, this method has solved the above-mentioned drawbacks, but it has been difficult to design a casting mold cavity, and since there are several gates, it takes a long time to filter, and at the same time, there is a problem in corrosion resistance.

As described above, in the filtration of molten metal, when casting a cast iron, it is necessary to pour the molten metal into the casting mold in a short time, and when a conventional rectangular or disk-shaped filter is used,
Particularly, pouring over several tons or more could not withstand thermal shock and corrosion resistance, and the defect rate was high.

The present invention has been made in view of the above circumstances, and has excellent thermal shock and corrosion resistance in filtering a large amount of molten metal, particularly, iron castings. It is an object of the present invention to provide a ceramic filter having a porous ceramic structure having excellent thermal shock resistance and excellent filtration performance, and a method for filtering molten metal, in which a filtration area in a cavity of a space can be made wider than that of a rectangular product.

[0007]

Means for Solving the Problems and Embodiments of the Invention In order to achieve the above object, the present invention provides the following ceramic filter and a method for filtering molten metal.

Claim 1: A ceramic filter having a three-dimensional net-like skeleton structure having an internal communication space interposed in a flow passage from the gate to the casting mold to be injected into the cavity of the casting mold. A ceramic filter characterized by being formed in a cylindrical shape.

Preferably, the filter body is obtained by depositing ceramic slurry on a synthetic resin foam having no cell membrane and calcining the ceramic slurry to remove the carbonized carbon. Ceramic filter.

Preferably, the filter body is formed of a ceramic having a melting point or a sublimation point of 1000 ° C. or higher.

Preferably, the filter body has a bulk specific gravity of 0.3 to 0.8 and a number of holes per 2.5 cm of a straight line is 3.
The ceramic filter according to claim 1, wherein the number of porosity is 40 or more and the porosity is 65% or more.

In another preferred embodiment, the ceramic filter according to any one of claims 1 to 4 is provided in the flow path from the gate to the cavity of the casting mold until the molten metal is injected into the cavity of the casting mold. Is arranged so as to flow from the outside through the peripheral wall portion into the internal hollow portion and to flow out from the lower end opening of the filter main body, and when the metal melt passes through the peripheral wall portion of the filter main body, impurities in the metal molten metal are removed. A method for filtering a molten metal, the method comprising removing the molten metal.

(6) The ceramic filter according to any one of (1) to (4) above, wherein the molten metal is filled in a flow path from the gate to the cavity of the casting mold. Arranged so that it flows into the internal hollow part from the opening and flows out through the peripheral wall of the filter body to the outside to remove impurities in the molten metal when the molten metal passes through the peripheral wall of the filter body. A method for filtering molten metal, characterized in that:

In the filter of the present invention, a porous ceramic body having a three-dimensional network skeleton structure is formed into a cylindrical structure.
By adopting the structure of No. 4, several tons of iron castings can be soundly filtered in a short time without damage or corrosion.

Hereinafter, the present invention will be described in more detail.
As shown in FIG. 1, the ceramic filter of the present invention has a filter body 10 formed in a cylindrical shape by a ceramic porous body having a three-dimensional network skeleton structure having an internal communication space. In this case, although FIG. 1 is formed in a cylindrical shape, the present invention is not limited to this, and may be formed in an elliptical cylindrical shape, a triangular cylindrical shape, a quadrangular cylindrical shape, a polygonal cylindrical shape having five or more angles, or the like. In addition,
The height or length of the filter body is preferably 3 to 1000 mm, particularly preferably 150 to 650 mm.

In this case, as the ceramic porous body, a ceramic foam obtained by adhering a ceramic slurry to a synthetic resin foam and drying and firing the same, or a rod-shaped ceramic formed by extrusion molding in a loop shape is formed. Ceramic noodles.
Among them, a ceramic foam having a box-shaped lattice structure of a regular dodecahedral structure obtained from a flexible polyurethane foam having no cell membrane is preferable because it has a small pressure loss.

As the ceramic, it is preferable to use a ceramic having a melting point or a sublimation point of 1000 ° C. or higher. Specifically, non-oxide ceramics include silicon carbide and silicon nitride. Examples of the ceramic include alumina, silica, aluminum phosphate, calcia, magnesia, cordierite and the like. These ceramic materials are used alone or as a mixture.

The selection of the material is appropriately performed depending on the molten metal to be filtered and the form of filtration. For example, in a casting mold of cast iron, the molten metal is directly dropped on a ceramic filter at room temperature and poured into a sand mold in a short time. For hot water, a material having excellent thermal shock resistance is required. Then, since the gate section is recovered as a return material, one that reacts with iron and finally dissolves is selected. Ceramics having such material properties are silicon carbide and silicon nitride. Usually, a mixture containing silicon carbide as a main component and alumina, aluminum phosphate, or silica as a sintering binder is used.

The ceramic filter of the present invention is preferably formed to have a bulk specific gravity of 0.3 to 0.8 in order to withstand the impact when pouring an iron casting. If the bulk specific gravity is less than 0.3, it cannot withstand impact and breaks, and if it exceeds 0.8, clogging due to the ceramic material occurs, and the passage of the molten metal is delayed, and good results may not be obtained. . Preferably it is 0.45-0.7.

The number of holes is 3 per 2.5 cm of a straight line.
It is preferred to have from 40 to 40, especially from 4 to 20. If the number is less than 3, the flowability is good, but the pore size is large, and the filtration efficiency is inferior. If the number is more than 40, clogging by the ceramic material occurs, and the flowability may decrease. More preferably, the number is 6 to 13.

The porosity is related to the material density and bulk specific gravity used for the porous ceramic body, but is more than 65%, especially 7%.
Preferably it is 5 to 85%. If it is less than 65%, the flowability of the molten metal decreases, and the pouring time may be extended.

As a method for producing the ceramic filter of the present invention, a known method such as roll impregnation can be used, and the following two methods can be used as a cylindrical processing method. First, as a first method, there is a method in which a polyurethane foam obtained by removing a cell film is ceramic-molded and then cylindrically processed by secondary processing. The second is a method of converting a polyurethane foam into a ceramic after cylindrical processing. In this case, the former secondary processing after ceramic molding,
The latter method is preferred because it takes a long time to process and the dimensional accuracy after molding is not obtained.

The filter of the present invention is disposed in a flow path between a gate and a cavity of a casting mold as shown in FIG.
That is, in FIG. 2, 20 is a gate, 21 is a gate, 22
Denotes a runner, which is located above a casting mold (not shown) and a runner 22.
The ceramic filter 1 is arranged between the ceramic filter 1 and the side.
In this case, the filter body 10 constituting the filter 1
The filter 1 is arranged so that the ring-shaped molten metal passage 30 is formed outside the peripheral wall portion 11 of the filter 1. In such a configuration, the molten metal flows into the ring-shaped molten metal passage 30 from the sprue 20 through the sprue rod 21 and the runner 22, and from the outside of the peripheral wall 11 of the filter body 10 to the three-dimensional internal communication space of the peripheral wall. By passing through, impurities in the molten metal are removed, and the molten metal thus filtered flows into the hollow portion 12 of the filter body 10 and then flows into the cavity of the casting mold.

As described above, in the ceramic filter of the present invention, by disposing the ceramic filter having a cylindrical structure between the cavity and the gate, only one-way inflow hole can be obtained in the conventional square or disk shape. However, the entire surrounding area becomes an inflow point, and the amount of casting per unit time increases.

In the example shown in FIG. 2, only one filter is arranged on one side of the sprue bar. However, it is optional to arrange a plurality of filters such as two filters on both sides of the sprue bar. is there.

In the above example, the molten metal is allowed to flow into the hollow portion 12 from the outside of the peripheral wall portion 11 of the filter main body 10. However, the molten metal from the gate is allowed to flow into the hollow portion 12 of the filter main body 10, and then to the peripheral wall portion. 11 from the inside to the outside, the melt filtered out from the outer peripheral surface of the peripheral wall portion 11 into the ring-shaped melt passage 30 as described above, and flows from the ring-shaped melt passage 30 to the cavity of the casting mold. Good.

Further, the thickness of the peripheral wall of the filter main body is preferably 5 to 30 mm, particularly 15 to 25 mm from the viewpoint of the above-mentioned filtration effect, efficiency, strength of the filter main body, etc. The major axis or diagonal line (the inner diameter of the filter body) is preferably 20 to 80 mm, particularly preferably 40 to 60 mm. The height or the length of the filter body is 3 to 1000 mm as described above, particularly 150 to 6 mm.
It is preferably 50 mm.

[0028]

EXAMPLES The present invention will be described below in detail with reference to examples and comparative examples, but the present invention is not limited to the following examples.

EXAMPLE A ceramic filter containing silicon carbide as a main component, having 6 holes / 2.5 cm, a bulk specific gravity of 0.52, a porosity of 81%, an outer diameter of 105 mm, an inner diameter of 60 mm, and a height of 250 mm was prepared. It was set as shown in FIG. Next, the ductile iron casting is melted at 1400 ° C.
200 kg was injected, and the pouring filtration time was measured. In addition,
For the ceramic filter, a flexible polyurethane foam without a cell membrane is processed into a cylindrical shape, and a ceramic slurry containing silicon carbide as a main component and alumina as a binder is adhered thereto, followed by drying and firing to carbonize and remove the flexible polyurethane foam. It was manufactured by doing.

Comparative Example Material of Ceramic Filter
The characteristics were the same as in the example, but the shape was 7
Using four 5 × 100 × 25 tmm square products, they were set as shown in FIG. 3, and a total of 1200 kg was melted, an iron casting was injected, and a pouring filtration time was measured. In addition, in FIG. 3, 1 'is a ceramic filter of the comparative example which consists of a square filter main body 10'.

Table 1 shows the above results.

[0032]

[Table 1]

[0033]

According to the present invention, it is possible to filter molten metal quickly and efficiently by surface filtration and internal filtration, with excellent thermal shock resistance and filtration performance, and with improved flowability of molten metal.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an embodiment of the present invention.

2A and 2B show an example of an arrangement mode of the same example, in which FIG. 2A is a front sectional view, and FIG. 2B is a transverse sectional view.

3A and 3B show an example of an arrangement of a conventional ceramic filter, wherein FIG. 3A is a front sectional view, and FIG. 3B is a transverse sectional view.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ceramic filter 10 Filter main body 11 Peripheral wall part 12 Hollow part 20 Sluice 21 Sluice bar 22 Sink 30 Ring-shaped molten metal passage

Claims (6)

[Claims] 1. A ceramic filter having a three-dimensional net-like skeleton structure having an internal communication space interposed in a flow passage from a molten metal to a casting mold to be injected into a cavity of a casting mold. A ceramic filter characterized by being formed in. 2. The ceramic according to claim 1, wherein the filter body is obtained by adhering a ceramic slurry to a synthetic resin foam having no cell membrane and firing the same to carbonize and remove the foam. filter. 3. The filter body has a melting point or a sublimation point of 1
The ceramic filter according to claim 1, wherein the ceramic filter is formed of a ceramic having a temperature of 000 ° C. or higher. 4. The filter body has a bulk specific gravity of 0.3 to 0.3.
0.8, the number of holes per 2.5 cm of a straight line is 3 to 40, and the porosity is 65% or more.
Or the ceramic filter according to 3. 5. The ceramic filter according to any one of claims 1 to 4, wherein the metal filter is provided outside a peripheral wall portion of the filter main body in a flow path from a gate to a cavity of a casting mold. Through the peripheral wall portion to flow into the internal hollow portion and to flow out from the lower end opening of the filter main body to remove impurities in the metal melt when the metal molten metal passes through the peripheral wall portion of the filter main body. A method for filtering molten metal, characterized in that: 6. The ceramic filter according to claim 1, wherein a flow path from the pouring gate to the casting mold cavity is filled with the molten metal. From the inside of the filter body and through the peripheral wall of the filter body to the outside so as to remove impurities in the molten metal when the molten metal passes through the peripheral wall of the filter body. A method for filtering molten metal, comprising: