JPH02247337A - Filter for filtering aluminum molten metal and its manufacture - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to a ceramic filter and a ceramic filter used for filtering and removing inclusions and agglomerated substances in molten aluminum and aluminum alloy (hereinafter referred to as "aluminum"). Regarding the manufacturing method (prior art and problems) Generally, molten aluminum contains non-metallic inclusions and hydrogen gas, so in order to improve the yield of aluminum products, it is necessary to remove these non-metallic inclusions, etc. Is it removed before pouring? llFr molten metal treatment" is required, and various methods are implemented depending on the purpose.

Traditionally, inclusions in molten aluminum are removed by passing it through a filter, but among these, molten aluminum filters using hard media are mainly used to remove intermetallic compounds and nonmetallic inclusions. It is superior to other methods in terms of adaptability to work, etc.

The characteristics required for a filter are: 1. It should have a large number of ventilation holes of appropriate and as uniform size as possible, and it should be able to reliably remove inclusions in the molten metal. 2. It should have corrosion resistance against materials that pass through 1lJl. Yes, no elution into the molten metal 3. Heat resistance and spalling resistance 4. It is necessary that the aggregate particles are reliably bonded to each other so that there is no spillage5, and that the material has a certain level of mechanical strength.

The method for producing this hard medium uses fused alumina as the aggregate and glassy material as the binder.
For example, if fused alumina is used as aggregate, 8203 15-80
% (weight %, same below), CaO3-50%, Al2O
52-60% and S10. SfO*lG ~ 50%, which is made by baking 4 to 20% of vitreous material (10% or less) and making it into a rigid filter (Japanese Patent Publication No. 47-36347), and by using fused alumina as aggregate,
82035 - 20% of an inorganic binder and combustible substances such as grains, coke powder, organic resins, etc. are blended, molded and fired (Japanese Patent Publication No. 52-22327), pre-granulated and fired alumina porcelain particles For 5I027
A method (Japanese Patent Publication No. 55-22126) is known in which a bonding agent containing Ca5Oa.+H20 is mixed with a flux mainly composed of 0 to 54% Al2O and 21 to 39% Al2O and then fired.

However, when molten aluminum is filtered through a filter using this vitreous binder, filter components such as Sl, Mg% ZnS Ti.

It was found that B and the like were eluted little by little, contaminating the molten metal even if the inclusions were removed.

In addition, filters with low elution of components, such as those using fused alumina as aggregate, and non-vitreous binders mainly composed of Al2O3, such as 64% Al2O3, 16% Ca0, 8
A filter using 20% 203 has been proposed, but impurity elements are leached out, and although the strength at room temperature is high, when heated to the temperature of molten aluminum, the bending strength decreases to several kg/a.
d, which makes it unusable.

Furthermore, if binder components elute from the molten aluminum, it will not only contaminate the molten metal (the bonding strength between aggregates will decrease,
In extreme cases, it may collapse during use, so it was necessary to develop a filter material with high temperature strength.

(Problems to be Solved by the Invention) The inventors have developed a filtration filter that has a certain bonding strength and filtration performance without using a vitreous bonding material, and that does not contaminate passing aluminum. The aim is to find a method for producing it.

(Means and effects for solving the problem) The inventors focused on the fact that fine alumina is easy to sinter, and by using it as a binder, they created a filter made essentially only of alumina. As a result, the above-mentioned problems were solved, a manufacturing method was found, and the present invention was completed.

That is, the present invention relates to a filter applicable to an aluminum melt filter characterized by firing a molded product consisting of molten alumina and fine alumina and having an Al2O3 content of 95% or more, and for 10 on parts of molten alumina. 2 to 25 parts of fine alumina, 0.1 to 5 parts by weight of shape retaining material, and water are kneaded and molded to form a powder of 1300 to 1500"c.
The present invention relates to a method for producing a filter for filtrating molten aluminum, which is characterized in that the filter is fired by firing.

When displaying Al2O, which is the main component, the total amount is usually 100% and the remaining amount is calculated by subtracting the sum of the analyzed components from the total amount, but rA1 in the present invention
"20a content" is the amount analyzed as 8 parts of Al2O.

The filter of the present invention uses molten alumina as the aggregate and fine alumina consisting essentially of alumina as the binder, and the component after firing is Al2O3-containing fl.
! More than 95%, 71021-3%, 3102
0.5% or less, MgO0.5% or less, CaOO
, 1% or less, Na2O 0.1% or less, and each other component is 0.
It is less than 1%.

Fused alumina has been known to be resistant to aluminum molten metal and has been used as a material for various aluminum molten metals, but the one used in the present invention is T.
Those containing i021 to 3% are preferred. Further, fine alumina having an Al2O3 purity of 99 or higher is used. As a result, a filter consisting essentially of only Al2O3 and TlO2 is obtained, with a small content of 5102, MgQ, CaO, and the like.

Comparing this with a filter using a vitreous binder, the content of impurities other than TlO2 in the filter of the present invention is several times to one-tenth, and the elution of each component into the molten aluminum is extremely reduced. be able to. In particular, the decrease in the elution amount of Sl was remarkable, and it was reduced to 1/10.
◎If the Al2O content is less than 95%,
The impurity content increases and is likely to cause elution.

The practical strength of the filter is a bending strength of 30 g/g at the passing temperature of molten aluminum, that is, 760°C.
It is good if it is more than c1/. The bending strength of the filter of the present invention is 50 kg/a/ or more at room temperature and 30 kg/a/ at 760°C.
/ca1 or more, and at 850°C, it is 20 Kg/d or more. On the other hand, the bending strength of a filter using a vitreous bonding material is 100 to 200 tg/d at room temperature and 4 tg/d at 760°C.
0 to 60 Kg/lsl, and several Kg/d at 850°C. Although the filter according to the present invention has a lower flexural strength at room temperature than a filter using a vitreous bond, its flexural strength at a hot temperature is lower than that of a filter using a vitreous bond. It does not deteriorate as rapidly as with other materials, and has a constant and high practical strength.

Next, the manufacturing method of the present invention will be described.

The present invention uses fused alumina as the aggregate.

Fused alumina is usually obtained by electrically melting bauxite and adjusting the particle size after cooling. The average particle size of molten alumina is 0
．． 1 to 4■■, preferably 0.4 to l-■, and
If it is less than 0.1 m, the molten metal passing pore diameter of the resulting filter will be small (if it exceeds 4 m, the molten metal passing pore diameter will become large, making it difficult to obtain a pore diameter suitable for molten metal filtration.
The total amount of impurities is less than 1% in terms of TlO2 and oxides, the rest is Al2O3, and it is stable against molten aluminum.

Fine alumina is used as the binding material. The average particle size of fine alumina is 0.1 μm to 10 μm1, preferably 0.5
μm to 2 μm, and if it is less than 0.1 μm, it is difficult to disperse due to agglomeration (it is inconvenient to handle, and if it exceeds 10 μm, it may not be completely melted during firing, resulting in insufficient bonding, and the filter strength It is preferable that the component is 99% or more as Al2O3 and has few impurities.

To 100 parts by weight of the above fused alumina, 2 to 25 parts by weight of fine alumina, 0.1 to 5 parts by weight of a shape retaining material, and water are added and kneaded and formed. ◇ Less than 2 parts by weight of fine alumina to molten alumina. If the amount exceeds 26 parts by weight, the molten metal passage hole diameter of the obtained filter becomes small, the filtering ability decreases, and the filter becomes easily clogged, resulting in a decrease in the function as a filter.

Furthermore, a shape retaining material is used to maintain the shape of the molded product before firing. It is preferable that the shape-retaining material is one that disappears by firing and that leaves ventilation holes when it disappears. Examples: Eva, starch, P
Examples include VC (polyvinyl alcohol) and MC (methyl cellulose), but starch is suitable. If the mixing ratio is less than 0.1 part by weight per 100 parts by weight of molten alumina, the shape-retaining power will be insufficient, and if it exceeds 5 parts by weight, there is a risk that it will remain in the pores as carbide during firing. In use, the shape retaining material is used as an aqueous solution with adjusted concentration.

The molding is carried out by pressure molding at 100 to 200 kg/m according to a conventional method, and the filling between the aggregates is made dense. After sufficiently drying the molded body thus obtained, it is fired at 1300 to 1500°C, preferably 1350 to 1450°C. If the firing temperature is less than 1300°C, the melting of the fine alumina may be insufficient; if it exceeds 1500°C, the fine alumina may melt excessively and narrow the ventilation holes.1350-145
When firing at 0° C., since the fine alumina particles are fine and easily sintered, the particle surfaces are melted and the molten alumina particle surfaces are fused at the contact portions. Note that since the molten alumina has a free fracture surface, the shape of the contact portion is non-uniform and constitutes a continuous space, resulting in a large number of continuous ventilation holes.

The physical properties of the fired product produced as described above include a bending strength at room temperature of 50 kg/1 m or more and a bending strength at 760°C of 1! i:30K
g/d or more, a pore diameter of 50 to 3001 tm, a porosity of 40 to 50%, and a bulk ratio of i[2.2 to 2.4, and had the function of a filter.

(Example) Next, the present invention will be specifically explained using examples.

(1) Physical property test Three types of binders: fine alumina A, fine alumina B
The following experiment was conducted on the combination of fine alumina C, one type of aggregate, and one type of shape retaining material.

Fine alumina A is Al2O399.6%, 5i020
．． 01%, Na2O0.35%, Fe2us0.01
% composition and an average grain size of 1 μm, fine alumina B has the same composition as fine alumina A and an average grain size of 0.7 μm, and fine alumina C has Al2O599.8%, 310%.
2 0.03%, Na200.06%, pe203 0
．． It has a composition of 03%, MgOO, 05%, and an average particle size of 0.
．． It is 6 μm. Fused alumina is commercially available alumina grains (J
IS R6001#24), AlaOa 97
．． 0%, Fe2O30,12%, 3102 0.
44%, Na2O0.04%, TlO22.0Q%, B
25s has a composition of 0.01% and an average particle size of 0.7m
It is m. The shape-retaining material is starch, and it is dissolved in water for 20 minutes.
% aqueous solution.

Based on the raw materials mentioned above, the bending strength (
Three-point bending strength), total porosity, and pore diameter were measured. The measurement method was based on JIS. The result is the first
Shown in the table.

In preparing the samples, samples Nos. 31 to 3 were prepared by mixing a predetermined amount of fine alumina A-C and a shape-retaining material with molten alumina, kneading, and press-forming at a pressure of 150 g/d to a width of 25 mm and a thickness of 25 mm. The molded product was molded into a rectangular column with a length of 15 mm and a length of 135 cm, and the molded product was dried at 90°C for 5 to 15 hours, and then fired in an electric furnace at 1350 to 1450°C for 1 hour to obtain a test piece.

For comparison, two types of commercially available enamel glazes, which are vitreous binders, were used as binders for the above-mentioned fused alumina as samples N004-5. In other words, the binding material is Japanese-made.
Frit made by Kit, SI 02 30
%, Al2O, 14%, Zn0 20%,
Ca0 19%, TlO2 11%, MgO
O, 7%, 820 s 3 , 1%, Na2O2,9
%, and the binder E is a frit made by Nippon Enamel Glaze, which contains 5i02336%, Al2O311.2%, Ca
O37%, BaQ 13.5%,
MgO18.6%, B25s 17.7%, Na
It has a composition of 0.3% 2O, and a 10% aqueous solution of PVA (polyvinyl alcohol) is used as a shape retaining material, and a predetermined amount is mixed with molten alumina, kneaded, and made into a prismatic test piece in the same manner as above. did.

The same tests as for samples N01-3 were conducted on these samples N014-5. The results are also listed in Table 1.

The results show that the product of the present invention has strength, total porosity, and pore diameter equivalent to that of conventionally used filter materials. Furthermore, the bending strength at 760° C., which is the same temperature as molten aluminum, is higher than that at room temperature, indicating that the filter of the present invention is more suitable for the operating temperature. Note that the bending strength of samples Nos. 014 to 5 suddenly decreased at 850°C.

(Left below) (2) Component Analysis Component analysis was performed on sample No. 3 used in the physical property test. The results are shown in Table 2.

Table 2 (%)
For reference, commercially available aluminum molten metal filtration filters made by T company using a glassy binder (NO, 6 and NO
A sample was cut out for 7) and subjected to component analysis in the same manner. The results are also listed in Table 2.

As a result, the filter of the present invention has an Al2O3 content of 9
5% or more, and the amount of impurity components other than TlO2 is particularly 5%.
It can be seen that IO2 is low.

(3) Elution test sample N011.3 (invention) and sample N014.5 (
Regarding Comparative Example), a disk with a diameter of 60 seconds and a thickness of 20 mm was obtained using the same formulation and the same procedure as those used in the physical property test. This disk is placed in a graphite crucible with aluminum grains.
The increase in the amount of impurity elements eluted into the molten aluminum after immersing it in a melt of aluminum and holding it at 850°C for 24 hours was measured. The results are shown in Table 3. The aluminum material used was 99.99% AI and At-4% Mg alloy, and the same molten aluminum was press-fitted into the sample before immersion.

As a result, it can be seen that the filter material of the present invention has a very small amount of impurity elements eluted, whereas in all samples Nos. 014 to 5 using the vitreous binder, binder component elements are eluted.

(4) Raw materials mixed in the same manner as the sample No. 003 were molded into a bottomed filter with an outer diameter of 100mm, an inner diameter of 60mm, and a length of 900°C using the vibration molding method, and dried at 90°C for 10 hours. , 15 bottomed filters were obtained by firing at 1400"C for 2 hours in a propane gas furnace.The average physical properties of these bottomed filters were a normal temperature bending strength of 64 kg/ad and a bulk ratio of 11.
! 2.30, average pore diameter! It was 57 μm. This bottomed filter was incorporated into four upper, three middle, and four lower filtration cartridges to filter an Al-4% Mg alloy. A/l/ Miniram 711 To the beginning of the passage to il, the throat was 700-■. No intermetallic compounds or oxides were detected in the molten aluminum after passing through the bottomed filter, and an increase in various impurity elements was caused by Sl 1
-2111111, Fe 1-2 ppm, other elements are all 0. It was less than lppm.

After processing a total of 50 tons, we stopped using the filter, destroyed the bottomed filter, and examined it. As a result, oxides such as spinel and oxide film were detected in the ventilation holes, indicating that it was functioning satisfactorily as a filter. Ta.

(Effects of the Invention) The filter of the present invention does not elute trace impurities into the molten aluminum, so the quality of cast products is stable and improved, and high purity aluminum and highly active A1
- Even when filtering Mg-based alloys, continuous filtration treatment is possible without elution of impurity elements.

Further, since fused alumina was used as the aggregate and fine alumina was used as the binder, a filter with sufficient functionality could be manufactured by welding and integrating at a temperature lower than the sintering temperature of alumina.

Furthermore, it has high temperature strength, so it can be used continuously for a long time.
This invention has great industrial effects because it does not disintegrate during use.

Patent applicant: Nippon Light Metal Co., Ltd. Kuchigaru Giken Co., Ltd. Procedural amendment 1989 April Yu/Sun

Claims (2)

[Claims] (1) A filter for filtrating molten aluminum, which is produced by firing a molded product made of molten alumina and fine alumina, and has an Al_2O_3 content of 95% (wt%) or more. (2) 100 parts by weight of molten alumina, 2 to 25 parts by weight of fine alumina, 0.1 to 5 parts by weight of shape retaining material, and water are kneaded, molded, and then fired at 1300 to 1500°C. A method for manufacturing a filter for filtrating molten aluminum.