JPH05262564A - Sic-based refractory and its production - Google Patents

Abstract

PURPOSE:To provide a refractory having high mechanical strength such as flexural strength and extremely excellent thermal shock resistance represented by little deformation and blistering and no crack generation, etc., after the use for a long period under repeated heating and cooling. CONSTITUTION:The objective refractory contains >=60wt.% of SiC aggregate particle, has the principal phase of grain-boundary part composed of a vitreous material consisting of 1.0-10.0wt.% of SiO2, <=0.05wt.% and >0wt.% of CaO, 0.05-1.0wt.% of V2O5 and 0.01-0.15wt.% of Al2O3 and contains cristobalite nearly uniformly distributing from the surface layer to the center part as a subsidiary phase of the SiC grain-boundary part.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a SiC refractory having excellent high temperature characteristics such as thermal shock resistance and a method for producing the same.

[0002]

2. Description of the Related Art Silicon carbide (SiC) -based refractory materials occupy an important position in the industry due to their excellent fire resistance. For example, they are widely used for shelf boards for ceramics, other firing jigs, and sheaths. ing. As a method for producing such a SiC-based refractory, conventionally, about 10% by weight of clay is mixed with SiC particles, and the mixture is kneaded, molded, and fired, and the SiC particles are combined with a silicate mineral, for example, a clay mineral to form SiC Methods for producing quality refractories are known. However, since the SiC refractory thus manufactured has a clay mineral having a low refractory degree as a connective structure, there is a problem that soft deformation and oxidation are likely to occur at high temperatures. Therefore, in recent years, SiC particles are partially kneaded and molded together with a small amount of a metal oxide and then baked in an oxidizing atmosphere to partially oxidize the SiC particles,
Attention has been focused on a manufacturing method in which SiC particles are bonded by silicon dioxide generated by the partial oxidation. The SiC refractory thus produced has the excellent property of having higher high-temperature strength than the clay mineral-bonded SiC refractory.

[0003]

[Problems to be Solved by the Invention] However, SiC
Silicon dioxide produced by partial oxidation of particles has a problem that it is difficult to sinter each other because it is formed so as to cover the surface of SiC particles and has a high purity and a relatively coarse texture.
In order to promote the mutual sintering of silicon dioxide and generate a dense and strong bond structure, it is important to optimize the type and amount of auxiliary components such as metal oxides. In the SiC refractory, sufficient consideration was not given to the composition of the connective structure, so that sufficient high-temperature characteristics could not be exhibited, and the quality of the refractories was large. In addition, the total amount and distribution of cristobalite existing as a sub-phase in the grain boundary bonding portion was non-uniform, which caused deformation, swelling, cracking, etc. of the SiC refractory, and reduced thermal shock resistance. .. The present invention uses such conventional Si
An object of the present invention is to provide a SiC refractory having excellent heat resistance and other high-temperature characteristics and a method for producing the same, by solving the problem of the C refractory.

[0004]

According to the present invention, the purpose of the present invention is to provide SiC aggregate particles in an amount of 60% by weight or more and a grain boundary bonding part main phase of SiO ₂ 1.0 to 10.0% by weight. Ca
O 0.05% by weight or less (but must be included), V ₂ O ₅
0.05 to 1.0 wt%, Al ₂ O ₃ 0.01~0.
It is a SiC refractory material having a binder phase composed of 15% by weight of glass, and the amount of cristobalite existing as a subphase in the SiC grain boundary bond portion is distributed almost uniformly from the surface layer portion to the center portion. It can be achieved with the featured SiC refractory.

In the present invention, the total amount of cristobalite existing as a subphase in the SiC grain boundary joint is preferably in the range of 0.1 to 15.0% by weight based on the entire SiC refractory material. The coordinates of the center of the refractory are 0,
Assuming that the coordinates of the surface layer are 100, the weight% (Cri _(50-100) ) of cristobalite of 50 to 100 parts and 0 to 50
The ratio (Cri _(50-100) ) / (Cri _(0-50) ) of the weight% (Cri _(0-50) ) of the cristobalite in the part is preferably 10 or less.

Further, according to the present invention, the V compound and the Ca compound are mixed with the SiC aggregate particles, the mixture is molded, and the molded body is fired in the temperature range of 700 to 1100 ° C. for 5 hours or more, Then, a method for producing a SiC-based refractory material is provided, which is further fired in a temperature range of 1300 to 1600 ° C. for 3 hours or more.

[0007]

The SiC refractory material of the present invention is produced by firing a molded body composed of SiC aggregate particles, V compound and Ca compound at a given temperature in a given atmosphere and then at a given temperature. To be done. SiC manufactured by this method
The quality refractory is made of cristobalite, which is one of the polymorphs of silica (SiO ₂ ) that exists as a subphase in the grain boundary joint part.
It has a characteristic that it is generated almost uniformly from the surface layer to the center, and it is extremely excellent in that it does not deform or swell even when it is used for a long time by repeatedly heating and cooling, and it does not cause cracks. It has excellent thermal shock resistance.

Further, when the composition of the binder phase made of glass is within the above range, more excellent high temperature characteristics are exhibited, and the softening deformation resistance at high temperature, the oxidation resistance, the mechanical strength and the thermal shock strength are improved. Remarkably improved. This is because when SiO ₂ which is the main component of the connective structure is produced in an appropriate amount by the partial oxidation of the SiC particles under the above-mentioned firing conditions, Al ₂ O ₃ , SiO ₂ which are the components in the silicate mineral, C
This is because in the presence of an appropriate amount of aO or the like, a V compound such as V ₂ O ₅ or the like added separately, or a Ca compound such as CaO, a dense and strong bonded state is exhibited. Such a dense and tightly-bonded structure in which SiC particles are strongly bonded is generated because SiO ₂ generated by partial oxidation of SiC is accompanied by a volume increase of about 2 times, thereby filling the fine pores in the refractory structure. And the presence of each of the above-mentioned auxiliary components in an appropriate amount
_{2 This} is considered to promote the mutual sintering reaction. Also,
Binder phase that oxidation resistance containing 0.05 wt% or less of CaO in, thermal shock resistance, is effective in terms of control of the control and the glass phase of the amount of cristobalite, 0 V ₂ O _5.
The presence in the range of 05 to 1.0% by weight has an effect of suppressing the oxidation reaction of the SiC particles in the refractory during practical use.

The SiC refractory material of the present invention is composed of SiC aggregate particles and grain boundary joint portions mainly composed of glass. The content of the SiC aggregate particles is 60% by weight or more, preferably 70 to 85% by weight or more, and the remaining grain boundary bonding portions are SiO ₂
1.0 to 10.0% by weight, preferably 2.0 to 8% by weight, CaO 0.05% by weight or less (but always included), V ₂ O ₅ 0.05 to 1.0% by weight, Al ₂ O ₃
It is composed of 0.01 to 0.15% by weight of a glassy phase.

In the present invention, the total amount of cristobalite is in the range of 0.1 to 15.0% by weight, preferably in the range of 0.1 to 8.0% by weight, based on the entire SiC refractory. It is preferable because the thermal shock resistance of the refractory can be improved. If the total amount of cristobalite is out of the above range, SiC may be used at high temperature for a long time.
Deformation, swelling, or cracking of quality refractory material occurs.

In the present invention, when the coordinates of the center of the SiC refractory are 0 and the coordinates of the surface layer are 100, 50
% By weight (Cri _(50-100) ) of cristobalite in the range of 100 to 100 parts (hereinafter referred to as the surface side) and% by weight (C in the range of 0 to 50 parts of the cristobalite in the following)
ri _(0-50) ) ratio (Cri _(50-100) ) / (Cr
i _(0-50) ) is preferably 10 or less, more preferably 5 or less. When this ratio exceeds 10, the thermal shock resistance and the like decrease.

Next, a method of manufacturing the SiC refractory material of the present invention will be described. First, a V compound and a Ca compound are mixed with SiC aggregate particles, and the mixture is molded into a desired shape.
Here, the particle size of the SiC aggregate particles is preferably 5 mesh or less (4000 μm or less), and more preferably 6 mesh or less (3360 μm or less). Clay minerals such as bentonite and kaolin can be mixed in addition to the SiC aggregate particles, the V compound and the Ca compound.

Next, in an oxidizing atmosphere, its maximum holding temperature is usually in the range of 700 to 1100 ° C., preferably 800 to 1100 ° C.
It is fired in the range of 1000 ° C. for 5 hours or more, and the fired body thus obtained is further fired in the temperature range of 1300 to 1600 ° C., preferably 1300 to 1500 ° C. for 3 hours or more. If the firing temperature is less than 1300 ° C., a SiC refractory having excellent thermal shock resistance cannot be obtained. On the other hand, if the firing temperature exceeds 1600 ° C., the flexural strength is somewhat lowered although the thermal shock resistance is good.

[0014]

The present invention will be described in more detail based on the following examples, but the invention is not intended to be limited to these examples.

(Examples 1 to 10) 90% by weight of SiC aggregate particles having a particle size of 6 mesh or less were used so that the composition of the vitreous binder phase became the composition shown in A of Table 1, CaO, V ₂ O ₅ , and kaori. Knight was added, and 5.0% by weight of water was added thereto as an externally added amount, and the mixture was kneaded. This raw material is 400 × 350 × 10 mm
After molding to (thickness), it was dried to sufficiently remove water. These molded bodies were fired under the conditions shown in Table 2 and their characteristics were evaluated. The results are shown in Table 1.

The heating rate was 100 ° C./hr. The thickness of cristobalite is 10m.
A large number of samples of 50 mm in length and 50 mm in length and width are cut out and the thickness is 2 m
The sample was cut into pieces each having a length of 50 m and a length of 50 mm to obtain a sample at a predetermined position, and the sample was analyzed according to the quantitative analysis method described in JP-A-3-27791. That is, first, the sample at the above-mentioned predetermined position is crushed to a particle size of 200 μm or less and mixed in a hydrofluoric acid solution, and the vitreous phase is dissolved under the optimum treatment condition for dissolving the vitreous phase obtained in advance. Processed. Then
The residue from which the vitreous phase had been separated was filtered off, and this residue was again added to a fixed amount of hydrofluoric acid solution, and subjected to dissolution treatment under the optimum treatment conditions for dissolving cristobalite, which had been obtained in advance. The residue from which cristobalite was separated was filtered off, and the amount of Si in the filtrate was determined by an absorptiometric method.
_The amount was converted to _{2 and used as the} amount of cristobalite. Moreover, the thermal shock resistance is 400 × 350 × 10 mm (thickness) of a SiC-based sintered body, on which 280 × 245 × 20 mm (thickness)
The Al ₂ O ₃ plate of No. ₂ was placed in a furnace for 1 hour and then pulled out to room temperature, and the fracture strength was determined by whether or not cracking occurred at this time. That is, the temperature at which cracking occurs is the breaking temperature.

(Example 11) A sintered body was obtained in the same manner as in Example 8 except that each component was added so that the glassy binder phase had the composition shown in B of Table 1, and the characteristics thereof were evaluated. did. The results are shown in Table 1.

(Example 12) A sintered body was obtained in the same manner as in Example 8 except that each component was added so that the vitreous binder phase had the composition shown in Table 1C, and its characteristics were evaluated. did. The results are shown in Table 1.

(Comparative Example 1) A sintered body was obtained in the same manner as in Example 8 except that the respective components were added so that the vitreous binder phase had the composition shown in Table 1D, and its characteristics were evaluated. did. The results are shown in Table 1.

(Comparative Example 2) A sintered body was obtained in the same manner as in Example 6 except that the primary firing was not performed, and its characteristics were evaluated. The results are shown in Table 1.

Comparative Example 3 A sintered body was obtained in the same manner as in Example 2 except that the primary firing was carried out at 600 ° C. for 5 hours, and its characteristics were evaluated. The results are shown in Table 1.

(Comparative Example 4) A sintered body was obtained in the same manner as in Example 6 except that the secondary firing was carried out at 1300 ° C for 2 hours, and its characteristics were evaluated. The results are shown in Table 1.

[0023]

[Table 1]

[0024]

[Table 2]

From the results shown in Table 1, it can be seen that Examples 1 to 12 satisfying the requirements of the present invention have excellent thermal shock resistance. On the other hand, Comparative Example 1 containing no CaO in the binder phase was inferior in thermal shock resistance due to excessive presence of cristobalite, and Comparative Example 2 in which primary firing was not performed, Comparative Example 3 in which primary firing temperature was low and Secondary In Comparative Example 4 where the firing time was short, the distribution of cristobalite was non-uniform,
It can be seen that both have low thermal shock resistance.

[0026]

As described above, according to the present invention, the mechanical strength such as bending strength is large, and even if it is used for a long time by repeatedly using temperature rising and cooling, there is almost no deformation or swelling. It is possible to provide a SiC refractory having extremely excellent thermal shock resistance that does not cause cracks and the like and a method for producing the same.

Continued Front Page (72) Hideo Saito, Hideo Saito, 776 Ijiri, Mitake-machi, Kani-gun, Gifu Prefecture (72) Inventor, Osamu Yamakawa, 5-5 Koyodai, Kani-shi, Gifu Prefecture

Claims (5)

[Claims] 1. A SiC aggregate particle is 60 wt% or more, a grain boundary bonding part main phase is SiO ₂ 1.0-10.0 wt%, and C
aO 0.05% by weight or less (but must be included), V ₂
O ₅ 0.05 to 1.0 wt%, Al ₂ O ₃ 0.01~
Si having 0.15% by weight of glassy binder phase
A C-type refractory, characterized in that the amount of cristobalite existing as a subphase in the SiC grain boundary joint is distributed substantially uniformly from the surface layer to the center. 2. The total amount of cristobalite existing as a sub-phase in the SiC grain boundary joint is 0.
The SiC refractory material according to claim 1, which is in the range of 1 to 15.0% by weight. 3. When the coordinates of the center of the SiC refractory are 0 and the coordinates of the surface layer are 100, the weight% (Cri _(50-100) ) and 0 to 50 of the cristobalite in 50 to 100 parts are obtained.
_3. The ratio (Cri _{(50-100 )} ) / (Cri _(0-50) ) of the weight% (Cri _(0-50) ) of the cristobalite of the part is 10 or less, 3. SiC refractory. 4. A SiC aggregate particle is mixed with a V compound and a Ca compound, and the mixture is molded.
A method for producing a SiC-based refractory material, which comprises firing at a temperature range of 1100 ° C. for 5 hours or more while raising or holding the temperature. 5. Subsequent to the firing of claim 4, further 13
A method for producing a SiC-based refractory material, which comprises firing at a temperature range of 00 to 1600 ° C. for 3 hours or more while raising or holding the temperature.