JPH0459008A - Production of filter material for molten metal - Google Patents

Abstract

PURPOSE:To produce a filter material having a specified void volume and uniform distribution and density of pores by filling a mold with aggregate particles and an inorg. binder not kneaded but individually poured into the mold, removing sludge, drying, releasing, and then calcining the obtd. molded body. CONSTITUTION:In the production process of the filter material for molten metal, comprising aggregate particles and an inorg. binder, a mold of specified shape is filled with the aggregate particles. Then a slurry of the inorg. binder is poured into the mold. Then sludge is removed from the material, and the material is dried and released. The obtd. molded body is then calcinated. By this method, a small amt. of the binder is enough, which is rather expensive compared to the aggregate, and the filter material having a specified void volume and uniform distribution and density of pores can be produced by a simple process.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for producing a filter medium for molten metal for filtering and removing solid impurities from molten metal.

[Prior art] Metal thin plates and foils are produced by casting molten metal into implants 1 and 2.
It is manufactured by rolling this. At this time, if solid impurities such as metal oxides and minute fragments of refractories contained in the molten metal are mixed into the ingot, pinballs and surface defects may occur during the rolling process for manufacturing thin plates, foils, etc. To prevent this, solid impurities are removed from the molten metal.

To remove these solid impurities, glass cloth, alumina balls, ceramic foam, etc. have conventionally been used as filters for molten metal.

However, glass cloth tends to get clogged early, alumina holes have poor filtration accuracy as impurities once captured tend to leak out again, and ceramic foam has large pores and cannot sufficiently remove fine impurities. there were.

Therefore, in recent years, molten metal filtration filters have been used in which aggregate particles such as alumina are bonded together using an inorganic binder to form a hollow pipe-shaped porous ceramic having numerous fine continuous pores between the aggregate particles.

This molten metal filtration filter is, for example, JP-A No. 48-6
As described in Publication No. 91.2 and Japanese Patent Publication No. 52-22327, etc., aggregate particles such as alumina and an inorganic binder raw material are generally kneaded, then formed into a hollow pipe shape and fired at a predetermined temperature. By cooling the aggregate particles, the aggregate particles are bonded to each other by the vitrified inorganic binding material, resulting in a porous fired body in which countless fine continuous pores are formed between the aggregate particles. Further, this filter molding is usually performed by press molding using a hydraulic press or the like, or by compaction molding, and the filling properties of the aggregate particles are adjusted to obtain a predetermined porosity. Furthermore, various proposals have been made to make the pore distribution and density of the obtained porous body uniform.

[Problems to be Solved by the Invention] However, in the method of kneading aggregate particles and an inorganic binder and filling the mixture into a mold, no matter how thorough the kneading is, fine pores with a predetermined pore size cannot be formed. It was difficult to evenly distribute the pores.

In addition, the applicant previously investigated the influence of aggregate particle-shaped filter media, and proposed the use of spherical aggregate particles in order to obtain a filter media with uniform pores at a predetermined porosity ( Japanese Patent Application No. 2-83248) discloses that a filter medium obtained by conventionally kneading and molding the above-proposed spherical aggregate particles and an inorganic binder with an organic binder and water has a non-uniform pore distribution. In addition, variations in strength occurred, and an excessive amount of inorganic binder was required.

Therefore, the inventors reviewed the kneading process of the conventional method, and in particular, in manufacturing a filter medium for molten metal using the spherical particle aggregate proposed above, the inventors found that a small amount of expensive binder is required compared to aggregate, and it is simple. As a result of extensive research into a method for manufacturing a filter medium having a uniform pore distribution and density with a predetermined porosity using a specific operation, the present invention was achieved.

[Means to solve the problem]

According to the present invention, in a method for manufacturing a filter medium for molten metal made of aggregate particles and an inorganic binder, a mold having a predetermined shape is filled with aggregate particles, then a slurry of an inorganic binder is poured into the mold, and then the slurry is discharged. A method for manufacturing a filter medium for molten metal is provided, which comprises firing a molded body obtained by muddying, drying, and releasing the mold.

The present invention is a method for manufacturing a filter medium for molten metal, in which raw material aggregate particles and inorganic binder are introduced into a mold separately without kneading them through the conventional kneading process. This is completely new. In addition, the use of expensive inorganic bond +4 is kept to the minimum necessary, and furthermore, it is possible to maintain a uniform porosity with a predetermined porosity without controlling the porosity by adjusting the filling properties of aggregate particles through pressurization operations such as pounding. This is an extremely useful manufacturing method as it provides a good pore distribution.

The present invention will be explained in more detail below.

The raw material for aggregate particles used in the present invention is not particularly limited in type, as long as it does not react with molten metal and is easily available with an appropriate particle size, but examples include alumina, silicon carbide, etc. , silicon nitride, zirconia, and other ceramic aggregates are preferred because they satisfy the above conditions.

The aggregate particles of the present invention have an average particle diameter of about 0.3 to 3.0 m.
A substantially spherical shape having a shape index of 100 to 130 is preferable.

Note that the shape index is defined as follows. That is, the second
In the projected diagram of the aggregate shown in the figure, when its maximum diameter is M, the diameter perpendicular to the maximum diameter M is B, the projected area is A, and the circumference length is P, the shape index (SF) is calculated by the following formula. It is expressed as

SF= (SF, +SF2+5Fff)/3 where: SF, -(π/4) x (M2/A,) y< 1
．． O03F2=(1/4π)X(P2/A)xlo
.

SF, =(M/B)xlOO It is.

Incidentally, the shape index of a pearl is 100. When the above-mentioned aggregate with a shape index in the range of 100 to 130 is used in a molten metal filter, a porous body having a uniform pore size can be obtained, and the degree of collection of impurities in the molten metal is improved. Therefore, it is preferable.

The type of inorganic binder used in the present invention is not limited as long as it does not react with metal. For example, silica (S+
Oz), aluminum (Δ1.203), calcia (Cab), magnesia (MgO), and oxidized carbon (
A material having a composition consisting of an oxide such as B20, ) is used. The inorganic binder phase is preferably used as a fine powder of about 200 μm or less.

The manufacturing method of the present invention is generally carried out according to the manufacturing process shown in FIG. 1, and will be explained below with reference to FIG.

First, the aggregate particles obtained as described above are filled into a mold having a predetermined shape. In this case, the mold may be vibrated during or after filling with aggregate particles to uniformly fill the entire mold with aggregate particles.

On the other hand, the inorganic binder is made into a slurry with an organic binder such as carphogycyl methyl cellulose (CMC) and an appropriate amount of water.

Next, the inorganic binder slurry is poured into a mold filled with aggregate particles. When the inorganic binder slurry is introduced, the mold may be vibrated in the same manner as in the aggregate particle filling process, or it may be vibrated after the inorganic binder slurry is introduced. That is, the porosity, density, etc. of the filter medium are i1
It is possible to obtain a uniform pore distribution with a uniform porosity and a simpler method than the conventional pounding and hardening method. The vibration method is not particularly limited. Also,
For porous materials with high porosity or when uniformity and foaming properties are not required, there is no need to vibrate the mold, and after pouring the inorganic binder slurry into the mold, it is allowed to stand still for several minutes to several hours. You can take it. Furthermore, the image processing of the vibration processing of the mold and the static processing after slurry inflow may be used in combination.

After injecting the inorganic binder slurry, excess slurry is removed. The inorganic slurry inflow and sludge removal treatment steps may be repeated as appropriate until a desired thickness of binder is obtained on the surface of the aggregate particles.

After removing the mud, it is dried, released from the mold, and if necessary, further dried and fired to obtain a porous body for a filter medium for molten metal. Firing is usually carried out at a temperature of 1200 to 1450°C, which may be selected as appropriate depending on the raw material of the aggregate particles used and the composition of the inorganic binder.

In order to smoothly release the mold from the mold, a suitable mold release agent such as latex or carbon powder may be applied to the mold.

〔Example〕

Hereinafter, the present invention will be explained in detail with reference to Examples.

However, the present invention is not limited to the following examples.

The porous fired bodies produced in the following examples were evaluated as filter media for molten metal using Method G below.

(1) Foamability Evaluation In the schematic cross-sectional view of the foamability test device shown in Figure 3, a container l is equipped with an air inlet 3 at the bottom and a support 2 for fixing the fired body for the dess 1 ~ in the middle. The porous fired body 10 produced in each example was fixed in water with a support 2, air was blown from the bottom at 50 r/min, and the state of foaming from the fired body IO was observed. Based on the foamability evaluation criteria shown in FIG. 4, the foaming state was ranked as A or -D.

That is, A: foaming occurs uniformly and continuously from the entire surface of the fired body;
Foaming occurs from almost the entire surface of the fired product, but there are some gaps.
In case C, foaming was noticeable, and in case D, foaming was sparse.

(2) Porosity: The apparent porosity determined by the boiling method according to JIS2205-74 was defined as the porosity.

(3) Maximum pore diameter Measured by mercury intrusion method.

(4) Aeration Amount Measured at a differential pressure of 14 mm in water column using a device manufactured based on Massengale's air aeration measurement device.

(5) Bending strength The bending strength was measured by a three-point bending test with a distance between fulcrums of 250 mm. Measurements were made for 20 pieces of each sintered body, and the average value and standard deviation σ were determined.

(6) Water flow rate and boron ()3) Removal rate JIS1050
The amount of molten aluminum per unit area was determined. In addition, the B removal rate was determined from the analytical value of B contained in aluminum before and after passing through the hot water.

Example 1 With each shape index shown in Table 1, the particle size was 0.85 to 1.
2 mm alumina aggregate particles were placed in a 30 mm thick, 3 mm width
It was filled into a rectangular parallelepiped acrylic mold with a diameter of 0.00 mm and a height of 300 mm. This mold was provided with a filling/inflow port and an air vent in part 1, and two mud removal ports in the bottom part 6.

On the other hand, the composition ratio is 1'1120330% by weight, Bz(h3
5% by weight, 120% by weight of Ca, MgO]-00% by weight of the inorganic binder was crushed to 200% by weight or less, and CMC
was used as bangu, and the ratio of inorganic binder to water was 1.
Water was added to achieve a weight ratio of 0:1.5, and a slurry was prepared using a trommel (alumina lining).

The prepared slurry was poured into a mold filled with the alumina aggregate particles described in -, and after the mold was slightly vibrated for 20 seconds, the slurry was drained. In addition, when using alumina aggregate particles with the same shape index, the filling rate of the bone phase particles was changed by adjusting the microvibration of the mold, and the porosity was adjusted to the porosity shown in Table 1. .

After removing the mud, it was dried at room temperature for 10 hours and at 50°C for 5 hours, and then released from the mold. After releasing the mold, it was dried for 12 hours at 105°C. Thereafter, it was fired at 1350°C to obtain a plate-shaped porous fired body.

Evaluation tests were conducted on the obtained porous fired bodies as filter media for various molten metals. The results are shown in Table 1.

(Hereinafter, blank space) Example 2 Alumina aggregate particles with an average particle diameter of 0.71 for each shape index shown in Table 2 were filled into the upper part of a cylindrical molded body with a thickness of 20 mm, and the inlet and air were vented. was filled into a double cylindrical stainless steel mold with an outer diameter of 100 cm, an inner diameter of 60 cm, and a height of 870 mm, with a mud draining port arranged at the bottom, while applying impact with an air vibrator.

Note that the impact from the air vibrator was adjusted to adjust the filling rate of the alumina aggregate particles so that the porosity was as shown in Table 2.

On the other hand, an inorganic binder made into a mass with a composition ratio of 25% by weight of Al2O3, 45% by weight of B2O3, 20% by weight of Ca, and 10% by weight of MgO is pulverized to 200 mesh or less, and CM
C was used as a binder, water was added in the same manner as in Example 1, and a slurry was prepared using a trommel.

The prepared slurry was poured into a mold filled with the above alumina aggregate particles, left to stand for 30 minutes, and then drained. After repeating this operation of slurry inflow, standing still, and mud removal 10 times,
After drying at 0°C for 10 hours, the mold was released. After demolding, 10
Main drying was performed at 5°C for 10 hours. Then 1300°C
A hollow pipe-shaped porous fired body was obtained.

Evaluation tests were conducted on the obtained hollow pipe-shaped porous fired bodies as filter media for various molten metals. The results are shown in Table 2.

(Hereinafter, blank spaces) From the results of the above examples, it can be seen that the porous fired body produced by the method of the present invention has small variations in bending strength, good foamability, and a uniform pore distribution. In addition, by adjusting the vibration of the mold and the inflow amount of the inorganic binder slurry, it is possible to adjust the filling rate to a predetermined value, and the porosity and i! ! It can be seen that a porous fired body having superior performance can be obtained.

[Effects of the Invention] The method for manufacturing a filter medium for molten metal of the present invention is to fill and flow aggregate particles and inorganic binder into a mold separately without kneading them, thereby forming a filter medium with a predetermined uniform pore size. A filter medium for molten metal of a porous fired body having a uniform pore distribution can be obtained. Furthermore, a predetermined porosity can be obtained by adjusting the filling rate of the aggregate particles by controlling the vibration of the mold, the number of times the inorganic binder slurry flows in, and the like. Furthermore, the present invention does not require a kneading operation, and the amount of inorganic binder can be adjusted to the minimum necessary level, making the operation simple and extremely useful industrially.

[Brief explanation of drawings]

FIG. 1 is a manufacturing process diagram of an embodiment of the present invention. FIG. 2 is a projection explanatory view of bones used in calculating the shape index of aggregate particles in the present invention. FIG. 3 is a schematic cross-sectional view of the foamability test device for filter media for molten metal of the present invention, and FIG. 4 is a foamability evaluation standard diagram showing the foaming state in the foamability test.

Claims (3)

[Claims] (1) In a method for producing a filter medium for molten metal consisting of aggregate particles and an inorganic binder, aggregate particles are filled into a mold with a predetermined shape, and then a slurry of the inorganic binder is poured into the mold, followed by draining and drying. A method for producing a filter medium for molten metal, which comprises firing a molded body obtained by demolding. (2) The method for producing a filter medium for molten metal according to claim (1), wherein the mold is vibrated before, during, and/or after the slurry flows in. (3) The method for producing a filter medium for molten metal according to claim (1) or (2), wherein the aggregate particles have a shape index of 100 to 130.