JP3373312B2 - SiC-based kiln tool and method of manufacturing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a kiln tool such as a shelf board or a floor board used for firing ceramics and tiles.

[0002]

2. Description of the Related Art Conventionally, silicon carbide (SiC) -based refractory materials are
Because of its excellent heat resistance and fire resistance, it occupies an important position in industry, and is widely used, for example, for shelf boards, floor boards, sheaths, and other kiln tools for firing ceramics. Such SiC
As a kind of high-quality refractory, SiC particles are kneaded and molded together with a small amount of a metal oxide and the like, and the SiC particles are partially oxidized by firing in an oxidizing atmosphere. _A so-called oxide-bonded SiC refractory, which is formed by bonding SiC particles by ₂ ), is known. This oxide-bonded SiC-based sintered body is
It is widely used as a kiln tool for firing ceramics because it is inexpensive.

[0003]

However, the oxide-bonded SiC refractory is a so-called nitride-bonded SiC formed by bonding SiC particles with a binder made of silicon nitride or the like.
As compared with high quality refractory materials and recrystallized SiC quality refractory materials, the strength level was low and spall resistance was poor, so that the life was generally short. In addition, recently, rapid firing is often performed to improve production efficiency and save energy, and the load on kiln tools is also increasing. From such a background, improvement in properties such as spall resistance, oxidation resistance, and creep resistance of oxide-bonded SiC refractory is required, but there are many contradictory factors in improving these characteristics, It was difficult to improve each other in a balanced manner. The present invention has been made in view of the above conventional circumstances, and oxide-bonded SiC in which various characteristics required for a kiln tool such as spall resistance, oxidation resistance, and creep resistance are improved in a well-balanced manner. The object is to provide a quality kiln tool and a manufacturing method thereof.

[0004]

According to the present invention, a SiC powder having a maximum particle size of 4 mm or less is 0.01 to 0.
7 wt% of V ₂ O _5, by forming a powder obtained by adding 0.01 to 0.7 wt% of CaO and 0.01 to 5 wt% of clay, SiC quality obtained by firing the A kiln tool, in which the surface layer portion and the central portion of the SiC-based kiln tool were measured by powder method by X-ray diffraction, and 2θ for CuKα ray was 3
For the height of the diffraction peak of silicon carbide which is 4.0 °,
When the ratio of the heights of diffraction peaks of cristobalite with 2θ of 21.9 ° was calculated, the ratio of the above ratio value in the central part to the above ratio value in the surface layer part was 20% or more, and the bending strength at room temperature was measured. Strength is ± 2 of bending strength at 1400 ℃
SiC quality kiln tool characterized by being in the range of 0%,
Will be provided.

Further, according to the present invention, 0.01 to 0.7% by weight of V ₂ O ₅ and 0.01 to 0.7% by weight of CaO are added to the SiC powder having the maximum particle size of 4 mm or less. And 0.01
The powder obtained by adding ~ 5% by weight of clay is kneaded together with an appropriate amount of water and an organic binder, and this is molded into a desired shape. After drying the obtained molded body, the temperature is 700 to 1100 ° C. The temperature is raised over 10 hours while firing, and the maximum temperature is in the range of 1300 to 1500 ° C, and 1
Provided is a method for producing a SiC-based kiln tool, which is characterized in that firing is continuously performed under a condition that a temperature range of 300 ° C. or higher is 2 to 10 hours.

[0006]

The SiC-based kiln tool of the present invention has a maximum particle size of 4 mm or less with respect to SiC powder of 0.01 to 0.7% by weight of V ₂ O ₅ and 0.01 to 0.7% by weight. CaO and 0.01
It was produced using powder obtained by adding ~ 5% by weight of clay. An SiC-based kiln tool manufactured using such powder under the conditions shown in the manufacturing method described later has the following properties.

That is, the surface layer portion and the central portion of this SiC-based kiln tool were measured by X-ray diffraction by the powder method,
When the ratio of the height of the diffraction peak of cristobalite having a 2θ of 21.9 ° to the height of the diffraction peak of silicon carbide having a 2θ of 34.0 ° with respect to CuKα rays is calculated,
The ratio of the value of the ratio of the central portion to the value of the ratio of the surface layer portion is 20% or more.

When the above powder is molded and fired in an oxidizing atmosphere, the SiC particles are partially oxidized to produce SiO ₂ .
This reacts with a trace amount of a metal oxide flux composed of CaO or V ₂ O ₅ to form a strong bonding phase and bond the SiC particles. At this time, SiO generated by oxidation of SiC
_In No. ₂ , a part of it transforms from vitreous to cristobalite and remains as a subphase, but if there is too much difference in the amount of cristobalite between the surface layer and the center of the kiln tool, it may be due to expansion / contraction during cristobalite transformation. Thermal stress increases and spall resistance deteriorates. Therefore, in the present invention, the relationship between the surface layer portion and the central portion with respect to the above-described ratio value is defined. Good spall resistance can be obtained when the above relation of the ratio values is satisfied.

In the present invention, the surface layer portion is a portion from the surface of the kiln tool to 1/3 of the wall thickness, and the center portion is the thickness direction of 1/3 of the wall thickness of the kiln tool. It means the central part of.

Further, the SiC kiln tool of the present invention has a bending strength at room temperature of ± 2 of the bending strength at 1400 ° C.
It is within the range of 0%. For example, flexural strength Datosuruto 500 kg / cm ² at 1400 ° C., bending strength at room temperature is 400~600kg / cm ^2. The relationship between the bending strength at room temperature and 1400 ° C. is defined as above because the strength difference between the room temperature and the heat becomes large, and when the strength characteristics with respect to temperature become unbalanced, the spall resistance decreases. is there. That is, the bending strength at room temperature is 1400.
If the bending strength at ℃ is not within ± 20%,
This causes a problem that the spall resistance is reduced.

Next, a method for manufacturing the SiC-based kiln tool of the present invention will be described. The SiC-based kiln tool of the present invention has a maximum particle size of 0.01 to 0.
It is prepared using a powder obtained by adding 7 wt% V ₂ O ₅ , 0.01 to 0.7 wt% CaO and 0.01 to 5 wt% clay.

Usually, since the thickness of a SiC-based kiln tool, for example, a shelf board is about 10 to 20 mm, the maximum particle size of the SiC powder as an aggregate is 4 mm or less from the viewpoint of its characteristics and production technology. , Preferably 3 mm or less. In addition, as a particle size range of the SiC powder, it is preferable that 500 μ or more is 35 to 50% by weight, 88 to 500 μ is 20 to 30% by weight, and 88 μ or less is 30 to 35% by weight, which is suitable for a kiln tool.

Of the components added to this SiC powder,
V ₂ O ₅ acts as an oxidation promoter during firing and promotes internal oxidation to reduce the difference in the degree of oxidation with the surface layer portion. V ₂ O ₅ is Si produced by partial oxidation of SiC particles.
It reacts with O ₂ to form a glassy film on the surface of the kiln tool, preventing oxygen from penetrating inside the kiln tool and improving oxidation resistance. The amount of V ₂ O ₅ added to the SiC powder is 0.01 to 0.7% by weight, preferably 0.01 to 0.5.
%, And more preferably 0.01 to 0.3% by weight. If the amount is less than 0.01% by weight, the above effect is insufficient,
If it exceeds 0.7% by weight, surface oxidation proceeds too much and internal oxidation decreases.

CaO has a function of facilitating the formation of glass and contributes to the improvement of oxidation resistance like V ₂ O ₅ . S
The amount of CaO added to the iC powder is 0.01 to 0.7% by weight, preferably 0.01 to 0.5% by weight, and more preferably 0.01 to 0.3% by weight. If it is less than 0.01% by weight, the above effect is insufficient, and if it exceeds 0.7% by weight, the viscosity of the produced glass is lowered and the bend resistance is lowered.

Clay is added as a plasticizer to increase the density during molding. The amount of clay added to the SiC powder is 0.01 to 5% by weight, preferably 0.1 to 4% by weight. If the amount is less than 0.01% by weight, the effect is insufficient and 5
If it exceeds 5% by weight, the Al ₂ O ₃ component and impurities increase, and the bend resistance decreases.

Further, in the present invention, 5% by weight or less of amorphous SiO ₂ may be added to the above powder. When amorphous SiO ₂ is added, it changes into cristobalite during firing, which helps crystallization and improves the characteristics of the kiln tool.

Such a powder is kneaded together with an appropriate amount of water and an organic binder and molded into a desired shape. After drying the obtained molded body, it is fired while raising the temperature range of 700 to 1100 ° C. over 10 hours. Like this 700
Internal oxidation is promoted by slowly raising the temperature range of ˜1100 ° C. over 10 hours. It should be noted that the temperature raising here does not have to be performed at a constant temperature raising rate, and the temperature raising rate may be appropriately changed, or a process of keeping the temperature during heating for a certain period of time may be provided. .

In the production method of the present invention, subsequent to the above firing, further firing is performed by setting the maximum temperature in the range of 1300 to 1500 ° C. In this firing, the temperature range of 1300 ° C. or higher is 2 to 10 hours. Try to be. Therefore, for example, if the maximum temperature is set to 1400 ° C. and the temperature is raised to the maximum temperature at a temperature increase rate of 50 ° C./hr,
1300 to 1400 ° C in the process of heating up to the maximum temperature
Since the temperature range of (2) is raised over 2 hours, the subsequent firing time (after reaching the maximum temperature) must be 8 hours or less. By firing under such conditions, the amount of oxidation of the SiC particles in the surface layer portion can be limited, and the difference in the cristobalite production amount between the surface layer portion and the central portion can be suppressed to be small.

If the maximum temperature is less than 1300 ° C., the oxidation of the SiC in the surface layer portion will be insufficient and a strong glassy film will not be formed on the surface, resulting in poor oxidation resistance.
If it exceeds 1500 ° C., the amount of oxidation in the surface layer portion becomes too large and the balance with the center portion becomes poor. Similarly, 1300
If the temperature range of ℃ or more is less than 2 hours, the oxidation of SiC in the surface layer is insufficient and the oxidation resistance is inferior, and if it exceeds 10 hours, the amount of oxidation in the surface layer becomes too large and the balance with the center is poor. Become.

[0020]

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.

Tables 1 and 2 show the SiC powders whose maximum particle diameters are the values shown in Tables 1 and 2 and whose particle diameters are adjusted so as to fall within the range of the following particle size mixing ratio suitable for the kiln tool. As described above, various additives were added, 0.03% by weight of carboxymethylcellulose, 0.05% by weight of dextrin, and 6% by weight of water were added as an organic binder, and the mixture was kneaded in a wet pan.

Particle size blending ratio 500μ or more 35 to 50% by weight 88-500μ 20-30% by weight 88μ or less 30-35% by weight

After aging the kneaded material thus obtained for one day,
A vibration molding machine equipped with an air vibrator was applied with vibration for about 20 seconds to carry out molding to obtain a plate-shaped molded body. After the molded body was dried, it was fired under various firing conditions (temperature rising condition, maximum temperature condition) shown in Table 1 and Table 2 to obtain 400
A test piece with dimensions of mm × 350 mm × 10 mm was obtained. In addition, Table 1
The details of the temperature raising conditions indicated by I to X and the maximum temperature conditions indicated by A to H in Table 2 are as shown in Table 3. The physical properties shown below were measured and evaluated for each of the obtained test pieces, and the results are shown in Tables 1 and 2.

[Apparent porosity, apparent specific gravity, bulk specific gravity] JI
It was measured according to S R 2205-74.

[Bending strength] Conditionally according to JIS R 221
According to 3-78, normal temperature bending strength was measured using an autograph, and hot bending strength was measured using a hot bending tester at 1400 ° C. A sample having a size of 130 mm × 25 mm × 10 mm cut out from a test piece was used, and a span of 100 mm was measured by a three-point bending method.

[SiO ₂ (Cristobalite) / SiC
[Ratio] The surface layer portion (the portion from the surface to the thickness of 2 mm) and the central portion (the portion of the thickness center of the thickness of 2 mm) of the test body are cut out and crushed separately, and each of the obtained powders is subjected to X-ray diffraction. It was measured by the method. The peak at 2θ = 21.9 ° with respect to the CuKα ray is set as a reference peak of SiO ₂ (cristobalite), and 2
Using the peak at θ = 34.0 ° as the SiC reference peak,
The heights of both reference peaks were measured, and the ratio of the height of the reference peak of SiO ₂ (cristobalite) to the height of the reference peak of SiC was determined. Then, the ratio of the value of the ratio of the central portion to the value of the ratio of the surface layer portion was obtained.

[Spolling resistance] Specimen (400 mm × 35
0mm × 10mm) 280mm × 240mm × 20mm in the center
The Al ₂ O ₃ plate of 1 was placed and the whole was heated to a set temperature in an electric furnace. After holding at the set temperature for 2.5 hours, the sample was pulled out to room temperature and examined for cracks in the test body. The test was conducted at a preset temperature of 250 ° C. If no cracks occurred in the test piece, the set temperature was raised by 25 ° C and the test was repeated until cracks occurred. Was set as the destruction temperature.

[Creep resistance] 1 cut out from a test piece
30mm × 25mm × 10mm sample, span 100mm
Then, a load of 150 kg / cm ² was applied to the central part of the sample, and the sample was kept at 1350 ° C. for 100 hours in this state, and then the bending amount of the sample was measured.

[Oxidation resistance] 130 cut out from the test piece
The mm × 25 mm × 10 mm sample was held in an atmosphere having an O ₂ concentration of 60% at 1150 ° C. for 200 hours, and the weight increase rate of the sample was determined.

[0030]

[Table 1]

[0031]

[Table 2]

[0032]

[Table 3]

As shown in Tables 1 and 2, all of the test bodies manufactured so as to satisfy the conditions of the manufacturing method of the present invention have a SiO ₂ / SiC ratio (height of diffraction peak of silicon carbide) of the surface layer portion. The ratio of the ratio of the height of the diffraction peak of cristobalite to the value of) is 20%.
As described above, the bending strength at room temperature is within ± 20% of the bending strength at 1400 ° C, and the spall resistance, creep resistance and oxidation resistance are highly balanced, and as a kiln tool It was preferable.

[0034]

As described above, according to the present invention,
It is possible to obtain an oxide-bonded SiC quality kiln tool in which various characteristics required for a kiln tool such as spall resistance, oxidation resistance, and creep resistance are improved in a well-balanced manner.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI C04B 35/64 J (56) References JP 62-83371 (JP, A) JP 62-21762 (JP, A) JP-A-5-262564 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) F27D 3/12 C04B 33/32 C04B 35/565 C04B 35/64

Claims (2)

(57) [Claims] 1. A SiC powder having a maximum particle size of 4 mm or less, 0.01 to 0.7% by weight of V ₂ O ₅ , 0.01 to
SiC formed by adding 0.7% by weight of CaO and 0.01 to 5% by weight of clay to form a powder, and firing the powder.
A kiln tool, in which the surface layer portion and the central portion of the SiC kiln tool are respectively measured by X-ray diffraction by a powder method, and 2θ for CuKα ray
When the ratio of the height of the diffraction peak of cristobalite with 2θ of 21.9 ° to the height of the diffraction peak of silicon carbide with 34.0 ° is obtained, A ratio of the above-mentioned ratio value is 20% or more, and the bending strength at room temperature is within a range of ± 20% of the bending strength at 1400 ° C. 2. A SiC powder having a maximum particle diameter of 4 mm or less, 0.01 to 0.7% by weight of V ₂ O ₅ , 0.01 to
Powder obtained by adding 0.7% by weight of CaO and 0.01 to 5% by weight of clay was kneaded together with an appropriate amount of water and an organic binder and molded into a desired shape. After the body is dried, it is baked while raising the temperature range of 700 to 1100 ° C. over 10 hours, and the maximum temperature is 1300.
The method for producing a SiC-based kiln tool is characterized in that the firing is continued under the condition that the temperature is in the range of -1500 ° C and the temperature range of 1300 ° C or higher is 2-10 hours.