JPH0468256B2 - - Google Patents

Description

[Detailed description of the invention]

(Field of Industrial Application) The present invention relates to a cordierite refractory with improved thermal shock resistance and heat deformation resistance. (Prior Art) Cordierite refractories have conventionally been used for shelves, pots, etc. in roller hearth kiln setters or ferrite firing for the electronics industry. Conventional cordierite refractories have been used in which mullite minerals are produced from alumina raw materials and clay raw materials, and cordierite minerals are used as aggregates and mullite minerals are used as binders. (Problems to be Solved by the Invention) However, conventional cordierite refractories have poor heat deformation resistance such as bending under hot conditions due to weak bonding force between particles, and furthermore, because they are made of a single composition, structural There was a problem that the thermal shock resistance was poor because it could not absorb heat. An object of the present invention is to eliminate the above-mentioned problems and provide a cordierite refractory having both excellent heat deformation resistance and thermal shock resistance. (Means for solving the problems) The cordierite refractory of the present invention has Al ₂ O ₃ 10
It is a cordierite refractory whose main components are ~82% by weight, _SiO2 14~54% by weight, and MgO4~8% by weight, and the main crystalline phase after firing is 10~40% andalusite mineral ( _{Al2 O3}・_SiO2 ), 35-60% cordierite mineral ₍ 2MgO・_2Al2O3・_5SiO2 ), 5
It is characterized by consisting of ~20% alumina mineral ( _Al2O3 ) and 10 _{~ 30} % mullite mineral ( _{3Al2O3.2SiO2 )} . (Function) With the above-described structure, excellent thermal shock resistance and heat deformation resistance are achieved by creating a structure in which 3Al ₂ O ₃ .2SiO ₂ is generated on the surface layer of the andalusite raw material. That is, such a composition is obtained by mixing, kneading, and molding predetermined particles of a cordierite raw material, an andalusite raw material, an alumina raw material, and a clay raw material, and then firing the mixture at, for example, 1300° C. or higher. In this case, the cordierite raw material is formed as aggregate, the andalusite raw material is formed as medium grain, fine grain, mullite, and the alumina raw material is formed as fine powder. As a result, mullite mineral is generated by the reaction between the andalusite raw material and the alumina raw material, and each particle is bonded to each other, thereby obtaining a sufficiently strong bonding strength and greatly improving heat deformation resistance compared to the conventional method. In this case, in order to obtain the above-mentioned structure, the whole andalusite raw material should not be mineralized as mullite.
It is necessary that the andalusite mineral and the alumina mineral remain. The presence of andalusite minerals and alumina minerals can be confirmed, for example, by qualitative analysis using X-ray diffraction. Next, the reason why the thermal shock resistance is improved in the present invention will be explained in more detail. The thermal expansion coefficients of andalusite mineral and alumina mineral are respectively
They are 0.4-0.6% and 0.7-0.8%, and there is a relatively large difference between the two. Therefore, numerous extremely fine microcracks are generated within the structure due to the difference in the coefficient of thermal expansion. Spalling occurs when the refractory is heated and cooled and stress is generated inside the refractory due to thermal expansion and contraction, exceeding the elastic limit of the structure. Therefore, according to the cordierite refractory of the present invention, in which countless microcracks are formed within the structure, thermal expansion and
The stress inside the refractory caused by thermal contraction is alleviated by the microcracks, which significantly improves thermal shock resistance and prevents the entire structure from being destroyed even if it receives a large thermal shock. I can do it. In addition, the andalusite mineral has a characteristic porosity that helps relieve stress within the refractory structure and further improves thermal shock resistance. In addition, the andalusite mineral in the refractory is 10 to 40
% is preferable because if it is less than 10%, the deformation becomes large, and if it exceeds 40%, the spall property becomes small. It is preferable that the cordierite mineral content is 35 to 60%, but if it is less than 35%, it will break easily and
This is because when it exceeds 60%, the bending becomes large. It is preferable that the content of mullite mineral is 10 to 30%; if it is less than 10%, the spall effect will be reduced, and 30%
%, spall resistance deteriorates. Further, if the alumina mineral content is less than 5%, the spall effect due to the difference in expansion of different types is small, and if it exceeds 25%, the difference in expansion of different types becomes too large, resulting in poor spalling resistance. (Example) An actual example will be described below. First, cordierite raw materials, andalusite raw materials, alumina raw materials, and clay raw materials with predetermined particle sizes, as well as sillimanite raw materials and kyanite raw materials as necessary, are prepared, mixed, kneaded, and shaped.
Samples having various compositions shown in Table 1 were obtained by firing at a temperature of 1350°C. That is, samples Nos. 1 to 10, which are products of the present invention, are
The chemical composition and mineral composition are as shown in the table, and all are within the range of the chemical composition and mineral composition of the present invention. On the other hand, Sample Nos. 11 to 20, which are comparative examples, are as shown in Table 1, and their chemical composition and mineral composition are outside the scope of the present invention. , using sillimanite raw materials and kyanite raw materials. In Table 1, the porosity and bulk specific gravity are JIS R2205.
The bending strength is measured according to the sample size 25 x 10 x
Measured according to JIS R2213 with a distance of 130 mm and a distance between fulcrums of 100 mm. In addition, the bending amount is 50×10×300 when the sample size is 50×10×300.
mm, distance between fulcrums 250mm, temperature 1350℃, holding time 2
The value was calculated by subtracting the amount of bending before heat treatment from the amount of bending after heat treatment, depending on the time condition. Furthermore, the thermal shock resistance is 300
180mm x 180 x 5mm on top of the mm x 300 x 10mm sample.
A ZrO ₂ setter was placed on the setter, the temperature was raised to 600°C, and after holding at that temperature for 15 minutes, the occurrence of cracks after being pulled out was observed. In the table, the number of ZrO ₂ setters installed is 5.
Those in which a crack occurred in the 7th stage are indicated by an X, those in which a crack occurred in the 7th stage are indicated by a △, and those in which no crack occurred in the 9th or higher stage are indicated by an O.

【table】

[Table] As is clear from the above-mentioned Table 1, each Example having the structure of the present invention has superior heat deformation resistance and thermal shock resistance compared to each Comparative Example. (Effects of the Invention) As described above, the cordierite refractory according to the present invention includes a predetermined amount of cordierite mineral,
It is characterized by being composed of andalusite mineral and alumina mineral, and it is possible to obtain extremely strong bonding strength due to the mullite mineral generated on the surface layer of the andalusite raw material, which can greatly improve heat deformation resistance. Moreover, due to the microcracks caused by the difference in thermal expansion coefficient between the andalusite mineral and the alumina mineral, and the porosity of the andalusite mineral, the thermal shock resistance can also be improved, which is an excellent effect. Therefore, the cordierite refractory of the present invention can be suitably used for roller hearth kiln setters, electronic industry shelf boards, ladle pots, powder metallurgy setters, and the like.

Claims (1)

[Claims] 1 _{Al2O3 10-82} % by weight, _SiO2 14-54% by weight,
It is a cordierite refractory whose main component is MgO4 to 8% by weight, and the main crystal phase after firing is 10% by weight.
~40% andalusite mineral, 35-60% cordierite mineral, 5-20% alumina mineral, 10-30
% mullite mineral.