JP3127509B2 - Ceramic porous body - Google Patents

Ceramic porous body

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Publication number
JP3127509B2
JP3127509B2 JP03237433A JP23743391A JP3127509B2 JP 3127509 B2 JP3127509 B2 JP 3127509B2 JP 03237433 A JP03237433 A JP 03237433A JP 23743391 A JP23743391 A JP 23743391A JP 3127509 B2 JP3127509 B2 JP 3127509B2
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JP
Japan
Prior art keywords
ceramic
porous
layer
thermal expansion
alumina
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Fee Related
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JP03237433A
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Japanese (ja)
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JPH0551278A (en
Inventor
慎 多田
文雄 小高
政勇 石橋
Original Assignee
株式会社ブリヂストン
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Priority to JP03237433A priority Critical patent/JP3127509B2/en
Publication of JPH0551278A publication Critical patent/JPH0551278A/en
Application granted granted Critical
Publication of JP3127509B2 publication Critical patent/JP3127509B2/en
Anticipated expiration legal-status Critical
Expired - Fee Related legal-status Critical Current

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    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02PCLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00Technologies related to metal processing
    • Y02P10/20Recycling

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a porous ceramic material which is suitably used as a filter for castings, especially for cast iron.

[0002]

2. Description of the Related Art Conventionally, a filter material for removing impurities from a molten metal such as cast iron by using a ceramic porous body (ceramic foam) having a three-dimensional network structure having an internal communication space. It is known to be used as. In this case, as a ceramic porous body for removing impurities of cast iron by filtration, it is effective to use silicon carbide having good thermal shock resistance as a ceramic raw material.

However, when a porous ceramic body made of silicon carbide is used as a filter material for cast iron, the amount of cast iron is small, and when the temperature of the cast iron is reduced and filtration is performed in a short time, erosion of the porous ceramic body hardly occurs. Raise the temperature of the cast iron to over 1400 ° C,
Silicon carbide reacts with cast iron when filtering large-capacity cast iron, and the ceramic porous body is eroded.Therefore, use silicon carbide ceramic porous bodies for applications that require more time to filter large-capacity cast iron. Can not.

The present invention has been made in order to improve the above circumstances, and provides a porous ceramic body which is hardly melted even when a large volume of cast iron is filtered for a longer time, and is therefore suitable as a filter material for castings. The purpose is to:

[0005]

Means for Solving the Problems and Actions The present inventors have conducted intensive studies in order to achieve the above object. Silicon carbide having excellent thermal shock resistance is mainly composed of a porous ceramic body, and the reactivity with iron is silicon carbide. An attempt was made to coat a skeleton composed mainly of a porous ceramic body made of silicon carbide with alumina using lower alumina.

However, cast iron having a high temperature of 1400 ° C.
In the case of large-volume filtration of 100 kg or more in 0 seconds or more, erosion was caused. This was thought to be due to the occurrence of cracks when alumina coating was mainly applied to a ceramic porous body composed mainly of silicon carbide. .

For this reason, the present inventor has further studied and found that, when an alumina layer is formed on a skeleton composed mainly of a ceramic porous body made of silicon carbide, it contains alumina and silicon carbide and has a thermal porosity mainly composed of a ceramic porous body. 18% of expansion coefficient
By providing a ceramic layer having a thermal expansion coefficient of not more than 18% and alumina having a thermal expansion coefficient of not more than 18%, crack-free ceramic porous material can be obtained, and large-capacity cast iron can be filtered at a high temperature of 1400 ° C. or more for a long time of 20 seconds or more. And found that there was no erosion and no change in the ceramic porous body,
The present invention has been accomplished.

Accordingly, the present invention provides a ceramic porous body having a three-dimensional network structure having an internal communication space, wherein a main body of the ceramic porous body is formed of silicon carbide,
A first ceramic layer containing alumina and silicon carbide is formed on the skeleton of the ceramic porous body so as to have a coefficient of thermal expansion within 18% of the coefficient of thermal expansion of the body, and the first ceramic layer is formed on the first ceramic layer. The present invention provides a porous ceramic body suitably used as a filter material for castings, particularly cast iron, wherein an alumina layer having a thermal expansion coefficient of 18% or less of the thermal expansion coefficient of the ceramic layer is formed. is there.

Hereinafter, the present invention will be described in more detail. In the ceramic porous body of the present invention, the main body of the ceramic porous body is formed of silicon carbide. In this case, the ceramic porous body mainly has a three-dimensional network structure having an internal communication space. In particular, a soft polyurethane foam without a cell membrane is immersed in a slurry containing silicon carbide to remove excess slurry. , After drying and baking. In this case, it is preferable to use silicon carbide having a particle size of 50 μm or less, particularly 20 to 30 μm. When a material having a particle size larger than 50 μm is used, when used for filtration of cast iron, the ceramic porous body may be partially melted.

Here, the porous ceramic body mainly has a pore number of 4 to 20 in view of its use as a filter material for cast iron.
Pieces / 25 mm, especially 6 to 13 pieces / 25 mm, and a bulk specific gravity of 0.4 to 0.6, particularly 0.45 to 0.55 are suitable. If the number of pores is less than 4/25 mm, the removability (filterability) of impurities may not be sufficient, and 20/2
If it is more than 5 mm, clogging may increase when the ceramic layer is coated. If the bulk specific gravity is less than 0.4, the strength of the molten metal may be insufficient, and if the bulk specific gravity is more than 0.6, clogging may increase when the ceramic layer is coated.

In the present invention, a first ceramic layer containing alumina and silicon carbide is formed on the surface of the skeleton composed mainly of the porous ceramic body. The first ceramic layer has a coefficient of thermal expansion α1 of 18% of the coefficient of thermal expansion α 0 of the porous ceramic body.
Within, more preferably not more than 15%, and the thermal expansion coefficient alpha 2 described later alumina layer is within 18%, and more preferably is formed to be within 15%. Here, the ratio of the coefficient of thermal expansion is a comparison at 25 to 1000 ° C., and the ratio of the coefficient of thermal expansion between the main body of the ceramic porous body and the first ceramic layer is determined by 100 × (α 1 −α 0 ) / α 0. The ratio of the coefficient of thermal expansion between the first ceramic layer and the alumina layer is determined by 100 × (α 2 −α 1 ) / α 1 .

When the ratio of the above-mentioned thermal expansion coefficients exceeds 18%, cracks are generated in the obtained ceramic porous body, and the ceramic porous body is melted off at the time of filtration of cast iron, so that the object of the present invention cannot be achieved.

The first ceramic layer can be formed by adhering a slurry containing alumina, silicon carbide, and, if necessary, clay or polyacrylic acid to the skeleton composed mainly of the porous ceramic body. Here, the proportion of these components is as long as the same crystal as the starting material is maintained at the firing temperature.
Since the thermal expansion coefficient is almost additive, the composition of the slurry and the thermal expansion coefficient can be adjusted by using the additive property. However, alumina is usually 70.70 as a ratio of alumina to silicon carbide. It is preferable to contain 9 to 24.7% and silicon carbide to be 29.1 to 75.3%.

Next, according to the present invention, an alumina layer is formed on the first ceramic layer. This alumina layer is formed using an alumina slurry.

Therefore, the ceramic porous body of the present invention has a two-layer coating structure in which a first ceramic layer is formed on the skeleton surface of the ceramic porous body and an alumina layer is formed thereon. A preferred method of manufacturing is to attach a silicon carbide-containing slurry capable of forming a ceramic porous body to a flexible polyurethane foam without a cell membrane, remove excess slurry, and dry to form a first ceramic layer. A slurry containing alumina and silicon carbide is attached, excess slurry is removed, dried, and an alumina slurry capable of forming an alumina layer (second ceramic layer) is attached, and excess slurry is removed.
It is preferable to dry, coat the dried product of each slurry on the flexible polyurethane foam having no cell membrane, and then fire it. In this case, the firing conditions are preferably 50 ° C./hour or less, particularly preferably 40 ° C./hour or less, for both temperature rise and temperature decrease. If the temperature rise / fall rate is faster than 50 ° C./hour, cracks may occur in the ceramic porous body.

The total coating amount of the first ceramic layer and the alumina layer is preferably 10 to 20% with respect to the main body of the porous ceramic. If it is less than 10%, the coating amount is insufficient, and erosion may occur when the cast iron is filtered. If it exceeds 20%, the ceramic porous body is clogged, and the filtration time when the cast iron is filtered becomes long. In some cases, cracks may occur, and erosion may occur. In this case, the coating ratio between the first ceramic layer and the alumina layer is 30:70 to 70:30 by weight,
In particular, the ratio is preferably from 40:60 to 60:40.

The porous ceramic body of the present invention is effectively used particularly as a filter material for cast iron. According to the porous ceramic body of the present invention, a large-capacity cast iron of 100 kg or more can be used.
Filtration can be performed at a high temperature of 00 ° C. or higher, especially 1450 ° C. or higher, and even if the filtration is performed under such severe conditions, no erosion occurs in the ceramic porous body.

[0018]

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. In the following examples, parts are parts by weight,%
Indicates% by weight.

Example 1 A. Preparation of Ceramic Slurry Adhering Foam Made Mainly of Ceramic Porous Body To 20 parts of silicon carbide having a coefficient of thermal expansion of 5.5 × 10 -6 and a particle size of 30 μm, 20 parts of clay, 20 parts of water and 5 parts of carboxyl group-modified polyacrylic acid were added. A slurry was obtained. A polyurethane foam without cell membrane having 6 holes / 25 mm is immersed in this slurry, and the polyurethane foam with the slurry attached is passed between rolls (the gap between the rolls is 20% of the polyurethane foam thickness) to remove excess slurry. After that, it was dried at 60 ° C.

The bulk specific gravity of the obtained foam was 0.48. The thermal expansion coefficient (α 0 ) when this foam is fired is 6.3 × 10 −6 . B. First layer coating 80 parts of silicon carbide having a coefficient of thermal expansion of 5.5 × 10 -6 and a particle size of 30 μm, 20 parts of clay, and 100 parts of alumina having a coefficient of thermal expansion of 7.9 × 10 -6 were converted to 20% of carboxy-modified polyacrylic acid.
Was added to 800 parts of an aqueous solution to prepare a slurry. This slurry was impregnated with the foam prepared in A, excess slurry was removed, and the slurry was dried at 60 ° C.

The first layer coating foam obtained
The specific gravity was 0.52. Also, dry the above slurry
And the coefficient of thermal expansion (α 1) Is 7.2 × 10
-6And the coefficient of thermal expansion α of A0And the ratio is (α1−α0)
× 100 / α0= 14.3%. C. Second layer coating Thermal expansion coefficient (αTwo) 7.9 x 10-6100 parts of alumina
With a 20% aqueous solution of carboxyl group-modified polyacrylic acid 9
In addition to 100 parts, a slurry was prepared, and
Impregnate the foam and operate as in B, with a bulk specific gravity of 0.5
A second layer coating foam of No. 7 was obtained.

The ratio of the thermal expansion coefficient α 1 of the first-layer coated ceramic to the thermal expansion coefficient α 2 of the second-layer coated ceramic is (α 2 −α 1 ) × 100 / α 1 = 9.7.
%. D. Firing The second layer coating foam obtained in C is 1400 ° C.
For 35 hours from 1400 ° C. to 200 ° C. for 30 hours, and a first ceramic layer having α 1 of 7.2 × 10 −6 is formed on a ceramic porous body mainly having α 0 of 6.3 × 10 −6. A ceramic porous body was formed, on which a second ceramic layer having α 2 of 7.9 × 10 −6 was further formed. The bulk specific gravity of this ceramic porous body was 0.49, and as a result of visual observation, there was no crack.

Example 2 The particle size of silicon carbide was 20 μm
A porous ceramic body was manufactured in the same manner as in Example 1 except that the above conditions were satisfied.

Comparative Example 1 80 parts of silicon carbide and 20 parts of clay were added to the ceramic slurry-adhered form A of Example 1.
A first layer coating was performed in the same manner as in Example 1 except that alumina was used in an amount of 150 parts. The bulk specific gravity of the obtained first layer coating foam is 0.52,
When the layer coating ceramic itself was fired, the coefficient of thermal expansion (α 1 ) was 7.5 × 10 −6 , and the ratio of A to the coefficient of thermal expansion α 0 was 19.0%.

Next, a second layer coating was applied in exactly the same manner as in Example 1. The bulk specific gravity of the obtained second layer coating foam is 0.56, and the ratio of the thermal expansion coefficient α 1 of the first layer coating ceramic to the thermal expansion coefficient α 2 of the second layer coating ceramic is 5.3%. there were.

Further, firing was performed in the same manner as in Example 1 to obtain a porous ceramic body having a bulk specific gravity of 0.46. Cracks were observed in the appearance of the ceramic porous material.

Comparative Example 2 A ceramic slurry-adhered foam was obtained in the same manner as in Example 1 except that the polyurethane foam to which the slurry had been adhered was passed between rolls with a roll gap of 17% of the polyurethane foam thickness. Fired in the same manner as in step D of Example 1 to obtain a bulk specific gravity of 0.5
0 ceramic porous body was obtained.

A casting metal test was conducted under the following conditions, in which the casting metal was poured into the ceramic porous body obtained above and the casting metal was filtered. The results are shown in Tables 1 and 2.

Conditions Porous ceramic body size: 75 × 75 × 25 mm Cast iron type: FCD (The casting temperature was changed between 1380 and 1480 ° C.) Casting method: Kakezeki, open bottom

[0030]

[Table 1]

[0031]

[Table 2]

[0032]

Industrial Applicability The ceramic porous body of the present invention is used for filtering cast products, especially cast iron, and is capable of melting a large volume of cast iron of 100 kg or more at a high temperature of 1400 ° C. or more for 20 seconds or more. No loss occurs.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. 7 Identification code FI // B22C 9/08 B22C 9/08 A

Claims (2)

(57) [Claims]
1. A ceramic porous body having a three-dimensional network structure having an internal communication space, wherein a main body of the ceramic porous body is formed of silicon carbide and a skeleton of the main body of the ceramic porous body has a thermal expansion coefficient of the main body. A first ceramic layer containing alumina and silicon carbide is formed to have a coefficient of thermal expansion within 18%, and a coefficient of thermal expansion within 18% of the coefficient of thermal expansion of the first ceramic layer is formed on the first ceramic layer. A porous ceramic body comprising an alumina layer having the same.
2. The ceramic porous body according to claim 1, which is used for a filter material of cast iron.
JP03237433A 1991-08-23 1991-08-23 Ceramic porous body Expired - Fee Related JP3127509B2 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
JP03237433A JP3127509B2 (en) 1991-08-23 1991-08-23 Ceramic porous body

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP03237433A JP3127509B2 (en) 1991-08-23 1991-08-23 Ceramic porous body

Publications (2)

Publication Number Publication Date
JPH0551278A JPH0551278A (en) 1993-03-02
JP3127509B2 true JP3127509B2 (en) 2001-01-29

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JP03237433A Expired - Fee Related JP3127509B2 (en) 1991-08-23 1991-08-23 Ceramic porous body

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Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP3438382B2 (en) * 1995-02-08 2003-08-18 株式会社ブリヂストン High temperature ceramic filter
DE19621638C2 (en) 1996-05-30 2002-06-27 Fraunhofer Ges Forschung Open cell foam ceramic with high strength and process for its production
MY138532A (en) 2000-08-31 2009-06-30 Foseco Int Refractory articles
US6902836B2 (en) * 2003-05-22 2005-06-07 United Technologies Corporation Environmental barrier coating for silicon based substrates such as silicon nitride
JP5553482B2 (en) * 2008-03-19 2014-07-16 日本坩堝株式会社 Molten metal container

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