JP3114981B2 - Heat and fire resistant ceramics - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a heat-resistant and fire-resistant ceramic sintered material that can be used as an apparatus member or the like that is repeatedly heated and quenched to a high temperature repeatedly.

[Related Art] Conventionally, as a heat-resistant and fire-resistant ceramic, for example, a sintered material such as cordierite, sillimanite, or mullite, a crystalline glass, and the like are known. However, each of these materials has a drawback that heat resistance and fire resistance are inferior. Particularly, the size of the product becomes large, and furthermore, when partial rapid heating and rapid cooling are performed, cracks and deformation are likely to occur. For example, in cordierite or a mixed sintered material of β-eucryptite crystal, alumina, boron nitride and aluminosilicate glass described in Japanese Patent Application No. 1-46084 by the present applicant, local heating to a high temperature is performed. If it is rapidly heated in the state, or if it is rapidly cooled, cracks will be generated, and it will be easily deformed under a high temperature load, and cannot be used repeatedly. For this reason, the original various characteristics of these ceramics cannot be utilized.

[Problems to be Solved by the Invention] The present invention improves the drawbacks of the above-mentioned conventional heat-resistant and fire-resistant ceramics, prevents cracking and deformation due to rapid heating up to high temperatures and rapid cooling, and is excellent as a ceramic material. An object of the present invention is to provide a novel ceramic sintered material having various characteristics.

[Means for Solving the Problems] The inventor of the present invention has conducted intensive tests and researches, and was able to obtain a heat-resistant and fire-resistant ceramic material having the following features. That is, the feature of the composition of the heat-resistant and fire-resistant ceramic of the present invention that achieves the above-mentioned object is that, as a main component, 40 to 65% of a synthetic β-eucryptite powder having a large negative linear thermal expansion coefficient as a main component. A mixture containing 15 to 40% of a natural clay and 10 to 40% of a natural and / or synthetic refractory inorganic oxide powder for facilitating molding such as water kneading, casting, kneading, and press molding of the following mixture. It is where it is sintered. The heat resistance of the present invention
Refractory ceramics have a linear thermal expansion coefficient (α × 10 ⁻⁷ cm /
℃) is in the range of ± 20 and basically does not contain vitreous material. Therefore, it does not show the abnormal thermal expansion characteristic peculiar to glass, has a linear thermal expansion curve, and is locally sharp to a high temperature under load. No cracking or deformation occurs even after repeated heat quenching.

The ceramics of the present invention may be composed of 45-60% of synthetic β-eucryptite, 15-35% of natural clay, and natural and / or synthetic refractory inorganic oxide powders such as polucite, cordierite, mullite, and sillimanite. When a mixture containing 10 to 40% in total of one or two or more powders of alumina and alumina is sintered, more stable heat and fire resistance is obtained, and the mechanical strength is large, so that it is preferable. . Although refractory inorganic oxides generally improve the mechanical strength as well as the refractory properties of the final product, in the above mixture, as oxides, polucite and / or cordierite powders having a relatively low coefficient of linear thermal expansion Is more preferable from the viewpoint of heat resistance and fire resistance, and among these, porusite has the advantage of having a large sintering accelerating effect.
In the above mixture, if necessary, as a sintering aid,
Glass powder and / or BN (boron nitride) can be contained at 10% or less. This glass powder is preferably a refractory glass such as an aluminosilicate glass or a borate glass.

The coefficient of linear thermal expansion of the heat-resistant and fire-resistant ceramic of the present invention is more preferably in the range of +10 to -20,
In general, cracks due to rapid thermal quenching of this type of ceramic material are more likely to occur at the time of temperature rise, in which temperature unevenness is likely to occur.

Hereinafter, preferred examples of the heat and fire resistant ceramics of the present invention will be described.

[Example No. 1] Synthetic β-eucryptite powder (80 mesh or less) obtained by mixing and sintering raw materials in a molar ratio of Li ₂ O · Al ₂ O ₃ · 2SiO ₂
50% of natural Motoyama clay powder (fine powder) 25% and natural polucite powder (under 52 mesh) 25% were mixed. About 20% of water was added to the mixture and kneaded. Then, the mixture was formed into a plate, dried, sintered at 1250 ° C. (1 hour), and 300 × 300 × 10
A plate sample of mm ³ was obtained. This ceramic sintered sample
It has a linear thermal expansion coefficient of about -17 × 10 ^-7 / ° C. This sample was held at a fixed position of 5 mm above a nichrome heater (heating unit 250 × 250 mm ² ), and partially heated rapidly to one sample surface at a speed of about 500 ° C. in 10 minutes, and then heated to about 550 ° C. When partial quenching was performed by applying cold water to the heated portion, no crack was generated. Also, place a refractory object on this sample and apply a load of 1 kg / cm ^{2 in} an electric furnace at 1050 ° C.
No deformation was observed when held for a time.

Further, other preferred embodiments of the ceramics of the present invention (N
o.2 to No.6) and as a comparative example (No.I and No.II), a cordierite sintered material (commercial product) and the above-mentioned sintered material by the present applicant were tested in the same manner as described above. An example
The results are shown in Table 1 together with No. 1. In the case of Examples No. 2 to No. 6, as in Example No. 1, the results of the rapid heating and quenching test and the weighted heating change test were good, whereas the comparative examples all showed cracks or deformation. The test results are defective in points.

[Effects of the Invention] Since the heat-resistant and fire-resistant ceramic of the present invention has the above-described configuration, it does not crack or deform even under the condition of being rapidly heated to a high temperature and cooled under a load. It can be used,
It is useful as various members that require fire resistance or as a soldering device member.

Claims (1)

(57) [Claims] A linear thermal expansion coefficient at 50 to 600 ° C. of -20 × 1.
A heat-resistant and fire-resistant ceramic in the range of 0 ^-7 to + 10 × 10 ^-7 / ° C, with 45 to 60% by weight of synthetic β-eucryptite powder as a main component (% is indicated by weight), natural clay powder A heat-resistant and fire-resistant ceramic obtained by sintering a mixture containing 15 to 35% and 10 to 40% of volusite as a natural and / or synthetic refractory inorganic oxide powder.