JP2840885B2 - Ceramic filter for molten metal filtration - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic filter used for filtering nonmetallic inclusions and the like mixed in a molten aluminum or an alloy thereof.

[0002]

2. Description of the Related Art Generally, foreign matters such as nonmetallic inclusions are mixed in a molten metal of aluminum or its alloy, which causes troubles such as hard spots during casting. For this reason, these foreign substances are removed by filtration prior to casting to avoid troubles in the post-processing step. There are various types of devices used for filtering the molten metal.
As described in JP-A-2-22327, SiO 2
₂ , a tube type filter using an inorganic substance such as B ₂ O ₃ as a binder is the best in terms of the quality of molten metal, and is generally used particularly for the treatment of aluminum and its alloys.

[0003] However, when filtering such molten aluminum, particularly high-purity aluminum, using such a conventional filter, SiO ₂ or C _{2 in a} molten aluminum is required.
There is a new problem that aO is reduced, free Si and free Ca are eluted, and the molten aluminum is contaminated.

For this reason, a ceramic filter containing no SiO ₂ component in the binder is disclosed in, for example, Japanese Patent Application Laid-Open No. 2-34 / 1990.
No. 732, for example. The main component of the binder in this ceramic filter is composed of one or two of Al ₂ O ₃ , B ₂ O ₃ and MgO and CaO, and is composed of a vitreous component. However, a filter using a binder composed of such a vitreous component has a low hot strength, and the filtration of molten metal having a high melting temperature such as high-purity aluminum may damage the filter during filtration. There is a problem because there is.

An object of the present invention is to provide a ceramic filter which does not contain components eluted from SiO ₂ or CaO, has a high hot strength, and can withstand practical use.

[0006]

According to the present invention, there is provided a ceramic filter used for molten metal filtration, wherein 6 to 16 parts by weight of a binder is blended with respect to 100 parts by weight of fused alumina aggregate particles. _B 2 _O 3 of the binder is less than 5 to 15 wt%, 25 to 55 wt% of MgO, 35 to 65 wt% of consists _Al 2 _{O 3,} wherein the binder is more than this and vitreous component non-glass The above problem is solved by a ceramic filter for filtering molten metal, which is characterized in that the ceramic filter is composed of a metal component.

[0007]

In the present invention, since SiO ₂ or CaO is not used as a binder component, there is no elution of Si or Ca in the process of filtering a high-purity aluminum melt or the like. Also, by setting the mixing ratio of B ₂ O ₃ , MgO and Al ₂ O _{3 in} the binder to an appropriate value, the vitreous component and the non-vitreous component more than this are mixed, whereby the room temperature strength and the hot strength are obtained. Can be increased. That is, in the early stage of the firing process, a vitreous component is generated, imparting fluidity to the entire binder, and the binder completely surrounds the aggregate. At this time, since the amount of B ₂ O ₃ is a constituent of the vitreous is not much, binder without causing excessive viscosity reduction, the aggregate is combined with a binding material sufficient thickness, the strength at room temperature Form a high ceramic filter. In addition, a non-vitreous component is generated from the latter stage of the firing process to the time of cooling to form a ceramic filter having high hot strength.

[0008] In addition, B ₂ O ₃ becomes 15% by weight or more.
Then, the vitreous component increases and the hot strength decreases. On the other hand, when the content of B ₂ O ₃ is less than 5% by weight, the amount of the vitreous component is too small, so that the binder hardly flows at the time of firing and the aggregates are not sufficiently bonded. As a result, the strength of the filter is reduced, and the binder is unevenly distributed around the aggregate, so that pores through which the molten metal passes cannot be formed properly.

[0009]

EXAMPLE 1 The binder composition was as shown in Table 1 with 100 parts by weight of fused alumina aggregate of 36 mesh, 13 parts by weight of binder, and 6.5 parts by weight of cereal flour as a combustible organic substance. Change and mix, after kneading, 20 × 100 × 100m
m, and fired at 1400 to 1450 ° C. to measure bulk specific gravity and porosity. In addition, this sample is 20 × 24 ×
It was cut into 100 mm and the hot bending strength at room temperature and 800 ° C. was measured. The bulk specific gravity was calculated from the size and weight, and the porosity was calculated by determining the weight in water by the boiling method. The bending strength was measured at a supporting span of 90 mm with a two-point supporting one-point load, and the hot bending was measured after placing the sample in an electric furnace with an ambient temperature set at 800 ° C. for 20 minutes. The results are also shown in Table 1.

[0010]

[Table 1]

In Table 1, sample numbers 2 to 6, 9 to 11
Indicates an example of the present invention, and sample numbers 1, 7, 8, and 12 indicate comparative examples. From the results of Sample Nos. 1 to 7 in Table 1, Al ₂
When the amount of O ₃ is less than 35% by weight or the amount of MgO exceeds 55% by weight, both room temperature and hot strength are low, and there is a possibility of damage during use. On the other hand, if the amount of Al ₂ O ₃ exceeds 65% by weight and the amount of MgO becomes less than 25% by weight, the porosity decreases, the amount of filtration becomes insufficient, and there is a practical problem. Also, from the results of Sample Nos. 8 and 12, when the amount of B ₂ O ₃ is less than 5% by weight, both the room temperature and the hot bending strength are low, and the B ₂ O 3
_{When the} amount of ₃ is 15% by weight or more, the room-temperature bending strength is high, but the hot bending strength is too low, and in any case, there is a problem in practical use.

[0012]

Example 2 Al ₂ O ₃ : 50% by weight, B
_With the blending ratio of ₂ O ₃ : 10% by weight and MgO: 40% by weight fixed, a half amount of the flour of the binder was added, and the ratio of the binder to the fused alumina aggregate of 36 mesh is shown in Table 2.
And a sample was prepared in the same manner as in Example 1, and the bulk specific gravity, porosity and bending strength were measured. Table 2 shows the results.

[0013]

[Table 2]

In Table 2, Sample Nos. 14 to 18 show Examples of the present invention, and Sample Nos. 13 and 19 show Comparative Examples. From these results, when the binder ratio exceeds 16 parts by weight, the flexural strength is high, but the porosity is low, the filtration amount is insufficient, and there is a practical problem. On the other hand, if the binder ratio is less than 6 parts by weight, the bending strength is low, and there is a possibility of damage during use, so that the intended effect of the present invention cannot be achieved. Sample No. 17 was immersed in pure aluminum,
C. for 240 hours, and then observed the sample under a microscope and confirmed the elution amount of Si and Ca in pure aluminum.
No remarkable abnormality of the tissue was observed, and neither elution of Si nor Ca was observed, and it was confirmed that the desired effects of the present invention could be achieved.

[0015]

As described above, the ceramic filter of the present invention does not contain SiO ₂ and CaO components, so that the contamination of the molten metal can be prevented, and the composition of the binder is a vitreous component and a non-vitreous material more than that. Since it is composed of components, it has a high normal temperature and high hot bending strength, and can be used for filtration of a molten metal having a high molten temperature such as a high-purity aluminum molten metal without fear of damage.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) C22B 9/02 B01D 39/20

Claims (1)

(57) [Claims] 1. A ceramic filter used for molten metal filtration, comprising 6 to 16 parts by weight of a binder with respect to 100 parts by weight of fused alumina aggregate particles, wherein the binder is 5 to 15% by weight. less than _B 2 _O 3, _25~55 wt%
Of MgO, it consists 35-65 wt% Al ₂ O _3, molten metal filtration ceramic filter the binder, characterized in that it is constituted by a vitreous component and which more non vitreous component.