JP5108311B2 - Oxide-bonded silicon carbide sintered body and manufacturing method thereof - Google Patents

Description

  The present invention relates to an oxide-bonded silicon carbide sintered body and a method for producing the same. More specifically, an oxide-bonded silicon carbide sintered body that is excellent in creep resistance and thermal shock resistance, has few firing cracks and warpage, and can be produced at a lower firing temperature than before, and production thereof It is to provide a method.

Conventionally, silicon carbide (SiC) refractories have occupied an industrially important position due to their excellent heat resistance and fire resistance. For example, shelves for ceramic firing (setters), floorboards, sheaths, setter posts, It is often used for beams, rollers, and other kiln tools. As a kind of such SiC refractories, SiC particles were kneaded and molded together with a small amount of metal oxides, etc., and fired in an oxidizing atmosphere to partially oxidize the SiC particles, resulting from the partial oxidation. A so-called oxide-bonded silicon carbide refractory (also referred to as “oxide-bonded silicon carbide sintered body”) in which SiC particles are bonded by silicon dioxide (SiO ₂ ) is known. This oxide-bonded silicon carbide refractory is widely used as a kiln tool for firing ceramics because it is inexpensive.

  However, the oxide-bonded silicon carbide refractory is compared with a so-called Si impregnated SiC or recrystallized SiC refractory formed by bonding silicon carbide particles (SiC particles) with a bonding material made of silicon nitride or the like. Since the strength level is low and the spall resistance is poor, the life is generally short.

  Recently, rapid firing is often performed to improve production efficiency and save energy, and the load on kiln tools is increasing. Against this background, improvements in properties such as spall resistance, oxidation resistance, and creep resistance of oxide-bonded silicon carbide refractories are required, but there are many conflicting factors in improving these characteristics. It was difficult to improve in a balanced manner.

In order to eliminate the above-mentioned problems, for example, 0.01 to 0.7% by mass of V ₂ O ₅ and 0.01 to 0.7% by mass of CaO with respect to SiC powder having a maximum particle size of 4 mm or less. And an oxide-bonded SiC kiln tool produced by using a powder obtained by adding 0.01 to 5% by mass of clay and a manufacturing method thereof (for example, Patent Documents 1 and 2). reference).

Further, the silicon carbide crystal particles are substantially composed of silicon carbide, have grain boundary portions and pores, and the silicon carbide crystal particles are bonded with an oxide containing silicon dioxide as a main component. An oxide-bonded silicon carbide material having a structure, a bending strength at normal temperature and high temperature of 100 MPa or more, and a bulk specific gravity of 2.65 or more is also disclosed (for example, see Patent Document 3).
Japanese Patent No. 3373312 JP-A-7-187785 JP 2006-335594 A

  However, the oxide-bonded SiC refractories as shown in Patent Documents 1 and 2 have lower strength than Si-impregnated SiC and recrystallized SiC refractories, so that they are heavy when used as products. In addition, it was not sufficient in terms of creep resistance and thermal shock resistance.

  Further, conventional oxide-bonded SiC refractories as shown in Patent Documents 1 to 3 are relatively high in temperature in order to advance crystallization of silicon oxide added to the raw material in advance or silicon oxide generated in the firing process. For example, it was manufactured by firing at a temperature exceeding 1300 ° C., but the firing cost at the time of firing increased, and the amount of carbon dioxide emission was also a problem. In addition, since the conventional oxide-bonded SiC refractory is fired at a high temperature as described above, there are many firing cracks, firing warpage, etc. due to the oxide generated in the firing process. There was also a problem that occurred.

  The present invention has been made in view of such problems of the prior art, is excellent in creep resistance and thermal shock resistance, has less firing cracks and warping, and moreover than a conventional sintered body. An object of the present invention is to provide an oxide-bonded silicon carbide sintered body that can be manufactured at a low firing temperature and a method for manufacturing the same.

  As a result of diligent studies to solve the above-mentioned problems, the inventor has a crystalline phase of silicon dioxide as a main phase and a specific vanadium oxide as a bonding portion for bonding aggregate particles substantially composed of silicon carbide. It has been found that the above problem can be solved by using a material containing a crystal phase, and the present invention has been completed. That is, according to the present invention, the following oxide-bonded silicon carbide sintered body and a method for producing the same are provided.

[1] Oxide-bonded silicon carbide having a porous structure composed of aggregate particles mainly composed of silicon carbide and substantially composed of silicon carbide, and a bonding portion containing silicon dioxide that bonds the aggregate particles. The bonded portion has a crystal phase of silicon dioxide as a main phase, NaV ₆ O ₁₅ and V ₂ O ₄ , a crystal phase of NaV ₆ O _{15 and} a crystal phase of V ₂ O ₄ . An oxide-bonded silicon carbide sintered body that is contained in the state of

[2] The total amount of vanadium (V) in the crystal phase of NaV ₆ O _{15 and} the crystal phase of V ₂ O ₄ is 0.05 to 2.8 mass with respect to the oxide-bonded silicon carbide sintered body. % Of the oxide-bonded silicon carbide sintered body according to [1].

[3] The crystal phase of NaV ₆ O _{15 and} the crystal phase of V ₂ O ₄ are both precipitated in the temperature lowering process of firing at a maximum temperature of 800 to 1300 ° C. [1] or [2] 2. An oxide-bonded silicon carbide sintered body according to 1.

[4] The oxide bond according to any one of [1] to [3], wherein a ratio of components other than silicon carbide in the oxide-bonded silicon carbide sintered body is 1 to 15% by mass. Silicon carbide based sintered body.

[5] The oxide-bonded carbonization according to any one of [1] to [4], wherein the bonding portion bonds the aggregate particles and covers at least a part of the surface of the aggregate particles. Silicon sintered body.

[6] The oxide-bonded silicon carbide based sintered body according to any one of [1] to [5], wherein the bonding portion further contains a silicon carbide crystal phase.

[7] A method for producing an oxide-bonded silicon carbide sintered body having a porous structure, in which aggregate particles composed mainly of silicon carbide and substantially composed of silicon carbide are bonded by a bonding portion containing silicon dioxide. A step of preparing a mixture by adding the silicon dioxide powder, vanadium pentoxide (V ₂ O ₅ ) powder, and Na compound necessary for producing NaV ₆ O _{15 to} the aggregate particles and mixing them (A) And the step (B) of obtaining the molded body by molding the obtained mixture, and the obtained molded body is fired under firing conditions having a maximum temperature of 800 to 1300 ° C, and the aggregate particles are obtained, Step (C) of obtaining a sintered body by bonding with the bonding portion containing silicon dioxide, and by cooling the obtained sintered body, the bonding portion having a silicon dioxide crystal phase as a main phase, NaV of ₆ O ₁₅ crystal phase and crystal phase of _V 2 _{O 4} Method of manufacturing an oxide bonded silicon carbide sintered body having a, a step (D) of Re is deposited respectively.

[8] The method for producing an oxide-bonded silicon carbide sintered body according to [7], wherein in the step (C), the firing temperature is increased from 600 ° C. to 800 ° C. for 10 to 20 hours. .

[9] The method for producing an oxide-bonded silicon carbide sintered body according to [7] or [8], wherein in the step (C), the molded body is fired in an air atmosphere.

[10] In the step (A), 0.5 to 5.0 parts by mass of silicon dioxide powder and 0.1 to 5.0 parts by mass of vanadium pentoxide powder with respect to 100 parts by mass of the aggregate particles. In addition, the method for producing an oxide-bonded silicon carbide sintered body according to any one of [7] to [9], wherein the mixture is obtained.

  The oxide-bonded silicon carbide sintered body of the present invention is excellent in creep resistance and thermal shock resistance, has few firing cracks and firing warp, and can be produced at a firing temperature lower than conventional. Moreover, the manufacturing method of the oxide bond silicon carbide sintered body of the present invention can manufacture such an oxide bond silicon carbide sintered body easily and at low cost.

  Hereinafter, embodiments of the present invention will be described. However, the present invention is not limited to the following embodiments, and appropriately designed based on ordinary knowledge of those skilled in the art without departing from the spirit of the present invention. It should be understood that changes, improvements, etc. can be made.

[1] Oxide-bonded silicon carbide sintered body:
First, an embodiment of the oxide-bonded silicon carbide sintered body of the present invention will be specifically described. The oxide-bonded silicon carbide sintered body of the present embodiment is composed of aggregate particles that are mainly composed of silicon carbide and are substantially composed of silicon carbide, and a bonding portion that includes silicon dioxide that bonds the aggregate particles. The oxide-bonded silicon carbide sintered body having a porous structure, in which the bonding portion has a crystal phase of silicon dioxide as a main phase, and NaV ₆ O ₁₅ and V ₂ O ₄ are converted into NaV ₆ O ₁₅ crystals. And a crystal phase of V ₂ O ₄ .

Conventional oxide-bonded silicon carbide sintered bodies are usually manufactured by firing a molded body at a firing temperature exceeding 1300 ° C., so that vanadium is present in the joint portion having a silicon dioxide crystal phase as a main phase. Even if it is contained, each of NaV ₆ O ₁₅ and V ₂ O ₄ is not contained in a crystalline phase state, for example, it is only a crystalline phase of V ₂ O ₄ or vanadium. This oxide is in an amorphous state (for example, glassy). An oxide-bonded silicon carbide sintered body in which aggregate particles are bonded by such a bonding portion may have low creep resistance or low thermal shock resistance.

In the oxide-bonded silicon carbide sintered body of the present embodiment, the bonding portion for bonding the aggregate particles has a crystal phase of silicon dioxide as a main phase, NaV ₆ O ₁₅ and V ₂ O ₄ , and NaV ₆ O _15. since in the state of crystalline phase of the crystalline phase and V ₂ O ₄ are those containing respectively, it is excellent in creep resistance and thermal shock resistance, firing cracks or firing warpage is reduced. Furthermore, it becomes possible to manufacture at a firing temperature lower than that of a conventional oxide-bonded silicon carbide sintered body.

  Such an oxide-bonded silicon carbide sintered body of this embodiment can be used for, for example, a shelf board (setter) for ceramics firing, a floor board, a sheath, a setter column, a beam and a roller, and other kiln tools. it can.

  In addition, the “main component” in the present invention refers to a component showing 70% by mass or more of all components. That is, the oxide-bonded silicon carbide sintered body of the present embodiment is made of silicon carbide in 70% by mass or more, and the remainder is made of silicon dioxide, vanadium, or the like constituting the bond.

  In addition, the “main phase” is a crystal phase having the highest component ratio among phases in which at least some of the plurality of components exist as crystal phases. In the bonded portion of the oxide-bonded silicon carbide sintered body of this embodiment, it is preferable that 5% by mass or more of silicon dioxide is the entire bonded portion including an amorphous component.

Whether or not each of the crystal phase of NaV ₆ O _{15 and} the crystal phase of V ₂ O ₄ is contained in the above-described bonding portion can be measured by X-ray diffraction (XRD). Specifically, for example, the diffraction peak of NaV ₆ O ₁₅ having a 2θ (diffraction angle) of 12.2 ° with respect to the X-ray source CuKα measured by a powder method by X-ray diffraction and 2θ (diffraction angle) are The presence can be confirmed by the presence or absence of a diffraction peak of V ₂ O ₄ of 27.8 °.

The NaV ₆ O ₁₅ crystal phase and the V ₂ O ₄ crystal phase described above are formed from a mixture containing aggregate particles substantially composed of silicon carbide, silicon dioxide powder, and vanadium pentoxide powder. After firing so that the temperature is 800 to 1300 ° C., it is preferable that the obtained fired body is deposited in the joint by lowering the temperature. According to this structure, the crystal phase of the crystalline phase and V ₂ O ₄ of NaV ₆ O _15, it is possible to be contained in a good condition during the coupling portion, the oxide binding silicon carbide of the present embodiment The sintered body can be produced at a relatively low temperature, and there are few firing cracks and warping. Further, the firing cost during firing can be suppressed, and the amount of carbon dioxide emitted can be reduced.

Further, although not particularly limited, in the oxide-bonded silicon carbide sintered body of the present embodiment, the above-described crystal phase does not include a crystal phase of vanadium pentoxide (V ₂ O ₅ ). It is preferable. Note that the absence of the vanadium pentoxide crystal phase means that no diffraction peak derived from the vanadium pentoxide crystal phase is detected under the above-mentioned X-ray diffraction conditions.

  Further, although not particularly limited, the oxide-bonded silicon carbide sintered body of the present embodiment has a bending strength of 30 MPa or more at room temperature and high temperature, specifically, 20 to 1400 ° C. Preferably, the pressure is 40 to 300 MPa, more preferably 45 to 300 MPa. Moreover, it is preferable that the difference in bending strength between 20 ° C. and 1400 ° C. is within 50%.

  Further, the oxide-bonded silicon carbide sintered body of this embodiment preferably has a bulk specific gravity of 2.65 or more, more preferably 2.65 to 2.90, and 2.65 to 2.90. Particularly preferred is 85.

  Furthermore, the oxide-bonded silicon carbide sintered body of the present embodiment preferably has a plate-like thermal shock temperature of 600 ° C. or more for practical use as a product.

[1-1] Aggregate particles:
Aggregate particles of the oxide-bonded silicon carbide sintered body of the present embodiment are particles substantially made of silicon carbide. “Aggregate particles substantially composed of silicon carbide” refers to aggregate particles composed of silicon carbide intentionally containing no other components other than impurities contained in the silicon carbide. In addition, as such an aggregate particle, the thing similar to the aggregate particle used for the conventional oxide bond silicon carbide sintered body can be used conveniently.

  The size of the aggregate particles used in the oxide-bonded silicon carbide sintered body of the present embodiment is not particularly limited, and may be of a size that can be used for a general oxide-bonded silicon carbide sintered body. For example, even a particle having a relatively small particle diameter or a particle having a relatively large particle diameter can be used. More specifically, the maximum particle diameter of the aggregate particles is preferably 10 to 4000 μm, more preferably 30 to 4000 μm, and particularly preferably 50 to 4000 μm.

  In addition, when the maximum particle size of the aggregate particles is less than 10 μm, the filling of the aggregate particles is poor and a sufficient bulk specific gravity may not be obtained, and when the maximum particle size of the aggregate particles exceeds 4000 μm, it is small. As in the case, the filling of the aggregate particles is poor, and a sufficient bulk specific gravity may not be obtained. Moreover, when it manufactures with big aggregate particle | grains, since the intragranular fracture | rupture of aggregate particle | grains will be produced, intensity | strength will fall and also the problem that thermal shock resistance may fall may arise.

  There is no particular limitation on the particle size distribution of the aggregate particles used in the oxide-bonded silicon carbide sintered body of the present embodiment. For example, the entire particles made of silicon carbide used in the oxide-bonded silicon carbide sintered body When the particle size is 100% by mass, particles having a particle diameter of more than 100 μm and not more than 200 μm are 30 to 55% by mass, particles having a particle size of more than 50 μm and not more than 100 μm are 2 to 18% by mass, more than 1 μm and less than 10 μm Particles are 10 to 40% by mass, and particles of 1 μm or less are 15 to 50% by mass. Of these particles, particles having a particle diameter of 10 μm or more are preferably in the range where the aggregate particles are mainly used.

  Further, when the total aggregate particle is 100% by mass, the particle diameter is in the range of 2 to 20% by mass of particles of more than 2000 μm and 4000 μm or less, and the particles of more than 500 μm and 2000 μm or less are 30 to 60% by mass The range is 2 to 20% by mass of particles greater than 250 μm and 500 μm or less, the range of 5 to 20% by mass of particles greater than 90 μm and 250 μm or less, and 20 to 35% by mass of particles 90 μm or less. A suitable product can also be obtained within the above range. By comprising in this way, the oxide bond silicon carbide sintered body excellent in creep resistance and thermal shock resistance can be obtained.

[1-2] Joining part:
The joint used in the oxide-bonded silicon carbide sintered body of the present embodiment contains silicon dioxide and is disposed in the gap between the above-described aggregate particles to bond the aggregate particles together. This bonding part has a silicon dioxide crystal phase as a main phase and contains NaV ₆ O ₁₅ and V ₂ O _{4 in the state} of a NaV ₆ O ₁₅ crystal phase and a V ₂ O ₄ crystal phase, respectively. .

  In the oxide-bonded silicon carbide sintered body of the present embodiment, the ratio of components other than silicon carbide in the oxide-bonded silicon carbide sintered body is preferably 1 to 15 parts by mass, The amount is more preferably 3 to 15 parts by mass, and particularly preferably 5 to 10 parts by mass. If the ratio of components other than silicon carbide is less than 1 part by mass, the amount of silicon dioxide constituting the bonding part is too small, the function of bonding aggregate particles decreases, and the bending strength decreases. There is. On the other hand, when the ratio of components other than silicon carbide exceeds 15 parts by mass, the content of silicon dioxide in the entire oxide-bonded silicon carbide sintered body becomes too large, and the oxide-bonded silicon carbide-based sintered body Creep resistance may decrease.

  In addition, as content of the silicon dioxide contained in a coupling | bond part, it is preferable that it is 0.45-10 mass% with respect to the whole oxide coupling | bonding silicon carbide sintered body, and it is 3-10 mass% Is more preferable, and it is especially preferable that it is 5-10 mass%.

Further, in the oxide-bonded silicon carbide sintered body of the present embodiment, the total amount of vanadium (V) in the crystal phase of NaV ₆ O _{15 and} the crystal phase of V ₂ O ₄ is the oxide-bond silicon carbide sintered body. It is preferable that it is 0.05-2.8 mass% with respect to the whole body, and it is especially preferable that it is 0.5-2 mass%. If the total amount of vanadium (V) exceeds 2.8% by mass, oxidation of the surface proceeds significantly during the firing process, so that an oxide film is formed on the surface, resulting in insufficient oxygen supply to the interior, resulting in an internal firing. In some cases, the sintering does not proceed, the bending strength of the sintered body is lowered, and the oxidation resistance and creep resistance are also lowered. On the other hand, if the total amount of vanadium (V) is less than 0.05% by mass, sintering of the bonded portion does not proceed and oxidation resistance may be lowered.

  In addition, the coupling portion is arranged in the gap between the aggregate particles to couple the aggregate particles. For example, the coupling portion couples the aggregate particles and at least a part of the surface of the aggregate particles. May be coated. By comprising in this way, oxidation produced in the process of using the oxide-bonded silicon carbide sintered body as a shelf for firing ceramics, aggregate particles (specifically, silicon carbide particles) and ceramics, etc. It is possible to avoid a problem such as a reaction that occurs in the case of direct contact.

  Further, in the oxide-bonded silicon carbide sintered body of the present embodiment, apart from the aggregate particles substantially made of silicon carbide, the bond portion may further contain a silicon carbide crystal phase. Good. The silicon carbide crystal phase contained in the bonding portion is composed of silicon carbide microparticles having a maximum particle size of less than 10 μm (more preferably 0.05 μm or more and less than 10 μm, more preferably 1 μm or less). Things can be mentioned. With this configuration, fine particles of silicon carbide (silicon carbide crystal phase) are filled in the voids in the grain boundaries of the aggregate particles, realizing close-packing and oxide-bonded silicon carbide-based firing. This can contribute to increasing the bending strength at normal temperature and high temperature of the bonded body.

In the oxide-bonded silicon carbide sintered body of the present embodiment, sodium (Na), magnesium (Mg), aluminum (Al), potassium (K), calcium (as a trace component) is added to the above-described bonding portion. It further contains an oxide containing at least one element selected from the group consisting of Ca), titanium (Ti), iron (Fe), nickel (Ni), copper (Cu), and barium (Ba). Also good. By comprising in this way, bending strength, oxidation resistance, and creep resistance can further be improved. In addition, an oxide containing a vanadium (V) element may be included in a state other than NaV ₆ O ₁₅ and V ₂ O ₄ .

  Further, in the oxide-bonded silicon carbide sintered body of this embodiment, a part of silicon dioxide contained in the bond portion may be contained as a crystal phase of cristobalite or tridymite.

[2] Method for producing oxide-bonded silicon carbide sintered body:
Next, one embodiment of the method for producing an oxide-bonded silicon carbide sintered body of the present invention will be specifically described. The method for manufacturing an oxide-bonded silicon carbide sintered body according to the present embodiment includes a porous structure in which aggregate particles mainly composed of silicon carbide and substantially composed of silicon carbide are bonded by a bonding portion including silicon dioxide. This is a method for producing an oxide-bonded silicon carbide sintered body.

And in the manufacturing method of the oxide-bonded silicon carbide sintered body of this embodiment, silicon dioxide powder and vanadium pentoxide (V ₂ O ₅ ) powder are added to the aggregate particles substantially made of silicon carbide. In addition, the step (A) of preparing a mixture by mixing, the step (B) of forming the obtained mixture to obtain a molded body, and the obtained molded body, firing conditions having a maximum temperature of 800-1300 ° C. In step (C), the aggregate particles are bonded by the bonding portion containing silicon dioxide to obtain a sintered body, and the obtained sintered body is cooled to obtain a crystalline phase of silicon dioxide. A step (D) of precipitating a crystal phase of NaV ₆ O _{15 and} a crystal phase of V ₂ O _{4 in} the bonding portion as the main phase.

  By comprising in this way, the oxide bond silicon carbide sintered body of this invention demonstrated until now can be manufactured simply and at low cost. In particular, the method for manufacturing an oxide-bonded silicon carbide sintered body according to the present embodiment can manufacture an oxide-bonded silicon carbide-based sintered body at a lower firing temperature than the conventional manufacturing method. Further, firing cracks and firing warpage of the sintered body can be reduced. Furthermore, the firing cost at the time of firing can be suppressed, and the emission amount of carbon dioxide can be reduced.

  Hereafter, each process of the manufacturing method of the oxide bond silicon carbide sintered body of this embodiment is demonstrated more concretely.

[2-1] Step (A):
Step (A) is a step of preparing a mixture by adding and mixing silicon dioxide powder and vanadium pentoxide (V ₂ O ₅ ) powder to aggregate particles substantially made of silicon carbide. In preparing this mixture, the mixture is dispersed in a liquid such as water and kneaded.

  The mixing ratio of each raw material such as aggregate particles, silicon dioxide powder, and vanadium pentoxide powder can be appropriately determined according to the configuration of the oxide-bonded silicon carbide sintered body obtained by firing. In the embodiment, 0.5 to 5.0 parts by mass of silicon dioxide powder and 0.1 to 5.0 parts by mass of vanadium pentoxide powder are added to 100 parts by mass of aggregate particles to obtain a mixture. Is preferred. By comprising in this way, the ratio of the aggregate particle | grains and the coupling | bond part of the oxide bond silicon carbide sintered body obtained becomes favorable, and the oxide bond silicon carbide sintering excellent in creep resistance and thermal shock resistance You can get a body.

  The aggregate particles used in the step (A) are preferably particles having a maximum particle size of 10 to 4000 μm, more preferably 30 to 4000 μm, and particularly preferably 50 to 4000 μm.

No particular limitation is imposed on the size of the silicon dioxide powder and penta vanadium oxide (V 2 _{O 5)} powder particles, silicon dioxide powder preferably has an average particle size of 1 to 30 [mu] m, vanadium pentoxide powder The average particle size is preferably 10 to 50 μm.

  In addition, it is preferable to further add a dispersing agent and / or a binder to the mixture prepared in the step (A). At this time, it is preferable that the dispersion material is added to the mixture, but the binder is not necessarily added. Although it does not specifically limit as a dispersing agent, Polycarboxylic acid ammonium, an acrylate ester copolymer, polyethyleneimine, sodium silicate, etc. can be used suitably. Moreover, it does not specifically limit as a binder, However, A polyacrylic acid emulsion, carboxymethylcellulose, polyvinyl alcohol, etc. can be used suitably.

  In addition, when manufacturing an oxide-bonded silicon carbide sintered body that further contains a silicon carbide crystal phase in the bonding portion, in addition to the above-mentioned aggregate particles, silicon carbide fine particles are further added. May be. The silicon carbide microparticles are particles having a particle diameter smaller than that of the aggregate particles, and the maximum particle diameter is less than 10 μm (more preferably 0.05 μm or more and less than 10 μm, and further preferably 1 μm or less). Silicon fine particles can be preferably used.

  The method of mixing the raw materials of the above mixture is not particularly limited, and a method for obtaining a mixture in a conventional method for producing an oxide-bonded silicon carbide sintered body, for example, a raw material prepared with a predetermined raw material preparation is made of a trommel or a kneader. In addition, a method of mixing in an attritor, a fret, etc. can be mentioned. In addition, granulation with a spray dryer can be carried out after slurrying.

[2-2] Step (B):
Step (B) is a step in which the mixture obtained in step (A) is molded to obtain a molded body. There is no restriction | limiting in particular about the method of obtaining a molded object, For example, well-known shaping | molding methods, such as a hydraulic press, vibration shaping | molding, and casting, can be mentioned.

  For example, when cast molding is used, there is an advantage that production is possible without requiring investment of a large press device or an extrusion molding machine. Further, there is an advantage that the density of the obtained molded body can be ensured to a necessary level and a molded body having a complicated shape can be produced relatively easily. Casting molding is a method in which powder such as ceramics is dispersed in a liquid such as water to form a slurry, which is poured into a mold and cured to form the powder into a predetermined shape. .

  In addition, in this process (B), it is preferable to dry the obtained molded object before baking in a process (C). There is no particular limitation on the drying method, and conventionally known methods such as hot air drying, microwave drying, dielectric drying, reduced pressure drying, vacuum drying, freeze drying and the like can be used.

[2-3] Step (C):
In the step (C), the molded body obtained in the step (B) is fired under firing conditions having a maximum temperature of 800 to 1300 ° C., and the aggregate particles are joined by a joint portion containing silicon dioxide and fired. It is a process of obtaining a ligation. Specifically, silicon dioxide produced by oxidation of silicon carbide in the firing process by firing in step (C), silicon dioxide powder contained in the raw material, and vanadium pentoxide (V ₂ O ₅ ) powder Once softened or dissolved, they are united to combine aggregate particles to form a joint. Thereby, a sintered body is formed.

By firing under the firing conditions where the maximum temperature is 800 to 1300 ° C., in the subsequent step (D), the crystal phase of NaV ₆ O _{15 and} the crystal phase of V ₂ O ₄ can be precipitated in the bonding part, respectively. Become. For example, if firing is performed to a temperature exceeding 1300 ° C., the crystal phase of NaV ₆ O ₁₅ does not precipitate in the temperature lowering process. In addition, when the maximum temperature is less than 800 ° C., the silicon dioxide powder and vanadium pentoxide powder in the mixture do not sufficiently soften or dissolve, so the aggregate particles cannot be firmly bonded, and the creep resistance and thermal shock resistance are high. It will decline.

  Further, since the firing temperature (maximum temperature) in this embodiment is lower than the firing temperature (maximum temperature) in the conventional method for producing an oxide-bonded silicon carbide sintered body, the sintered body is fired. Cracks and firing warpage can be reduced. Furthermore, the firing cost at the time of firing can be suppressed, and the emission amount of carbon dioxide can be reduced.

In this step (C), it is preferable that the time for raising the firing temperature from 600 ° C. to 800 ° C. is 10 to 20 hours. Thus, in the temperature range from 600 ° C. to 800 ° C., the crystal phase of NaV ₆ O _{15 and} the crystal phase of V ₂ O ₄ are satisfactorily precipitated in the temperature lowering process by raising the temperature sufficiently over time. Can be made. For example, if the temperature is rapidly increased in the temperature range from 600 ° C. to 800 ° C., the amount of precipitation of the crystalline phase is reduced, and the component to be originally precipitated becomes a crystalline phase having an amorphous or other composition. May end up. Note that the temperature increase here does not have to be performed at a constant temperature increase rate, and a process of appropriately changing the temperature increase rate or keeping a temperature during the temperature increase for a certain time may be provided. .

  In step (C), subsequent to firing in the above temperature range (600 to 800 ° C.), further firing is performed so that the maximum temperature is 800 to 1300 ° C. In this firing, the temperature is raised to the maximum temperature. It is preferable to carry out at a heating rate of 50 ° C./hr. By comprising in this way, the oxidation amount of the aggregate particle | grains of a surface layer part can be restrict | limited.

  In the step (C), the firing may be performed in any of an oxidizing atmosphere and a reducing atmosphere. In the present embodiment, it is preferable to fire the molded body in an air atmosphere. For example, when manufacturing a Si impregnated SiC or a recrystallized SiC refractory, an atmosphere adjustment furnace is indispensable, but in the manufacturing method of the oxide-bonded silicon carbide sintered body of the present embodiment, the atmosphere Since firing in an atmosphere is possible, expensive equipment is not required, manufacturing costs can be greatly reduced, and productivity can be greatly improved. As a heating method of the firing kiln, resistance heating by an electric heater, induction heating, heating by a combustion burner, or the like can be used.

[2-4] Step (D):
In the step (D), by cooling the obtained sintered body, the crystal phase of NaV ₆ O _{15 and} the crystal phase of V ₂ O ₄ are precipitated in the joint portion having the crystal phase of silicon dioxide as the main phase, respectively. It is a process to make. Specifically, the vanadium pentoxide powder dissolved or softened by the baking in the step (C) is recrystallized in the state of the crystal phase of NaV ₆ O _{15 and} the crystal phase of V ₂ O _{4 in} the bonding portion.

  Although there is no restriction | limiting in particular about temperature-fall conditions, It is preferable to temperature-fall at a temperature-fall rate of 300 degrees C / hr or less.

  As described above, the oxide-bonded silicon carbide sintered body of the present invention can be produced simply and at low cost.

  EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited to these Examples. Moreover, the measuring method and evaluation method of various physical property values are shown below.

[Crystal Phase of Bonding Portion]: The crystal phase of the bonding portion constituting the oxide-bonded silicon carbide sintered body was measured by X-ray diffraction (XRD). Specifically, it was measured by a powder method using an X-ray diffractometer (trade name “RINT-1200”) manufactured by Rigaku Corporation. The crystal phase of NaV ₆ O _{15 and} the crystal phase of V ₂ O ₄ are a diffraction peak of NaV ₆ O ₁₅ having a 2θ (diffraction angle) of 12.2 ° with respect to the X-ray source CuKα, and 2θ (diffraction angle). Was confirmed by the presence or absence of a diffraction peak of V ₂ O ₄ having a 27.8 °.

[Creep resistance]: A test body having a length of 120 mm, a width of 20 mm, and a thickness of 5 mm was cut out from the oxide-bonded silicon carbide sintered body, supported with a span of 100 mm, and a 1 MPa load was applied to the center portion. After being kept at 1300 ° C. for 200 hours, the bending amount of the test body was measured.

[Firing cracks]: Ethyl alcohol was applied by brush to the surface of the oxide-bonded silicon carbide sintered body, and the presence or absence of cracks was confirmed. When cracks are generated, the alcohol penetrates into the gaps between the cracks, so that the cracks can be confirmed linearly by visual observation. A sample having no cracks was marked as ◯, a crack having a length of 1 mm or less was evaluated as Δ, and a crack having a length of 1 mm or more was marked as ×.

[Firing warpage]: A plate-shaped product (molded product) having a length of 400 mm, a width of 400 mm, and a thickness of 10 mm is manufactured. After firing under each condition, the product is placed on a surface plate and applied with a ruler and a product. The gap was measured and the maximum gap was measured to determine the firing warpage.

[Dimensional expansion]: A plate-shaped product (molded body) having a length of 400 mm, a width of 400 mm, and a thickness of 10 mm was produced, and the length of the 400 mm portion before and after firing was measured with calipers under each condition, and the length after firing. The value obtained by dividing the length before firing from the above was defined as dimensional expansion.

[Thermal shock resistance]: A plate-shaped product (molded body) having a length of 400 mm, a width of 400 mm, and a thickness of 10 mm was manufactured, and after firing under each condition, 2 kg of a portion corresponding to 70% of the area of the top surface of the fired product Alumina refractory bricks were loaded, and 100 mm high struts were placed at four locations from the hearth, and the products were loaded thereon. Next, after heating to 600 ° C. in an electric furnace, the hearth part was taken out from the furnace into a room at 25 ° C. and rapidly cooled to check for cracks in the product. The case where no crack was generated was indicated by ◯, the case where a crack was generated was 10 mm or less, and the case where a crack having a length of 10 mm or more was generated was ×.

[Bulk Specific Gravity]: The density (bulk specific gravity) of the oxide-bonded silicon carbide sintered body was measured according to “Measurement Method of Apparent Porosity / Water Absorption / Specific Gravity of JIS R 2205 Refractory Brick”.

[Bending strength]: Measured by the 4-point bending strength in “JIS R 1601 Bending strength test method of fine ceramics”.

Example 1
With respect to 100 parts by mass of silicon carbide powder, 1 part by mass of silicon dioxide powder, 0.4 part by mass of vanadium pentoxide (V ₂ O ₅ ) powder, 0.1 part by mass of clay, 0.01 part by mass of calcium carbonate, sodium silicate A mixture obtained by adding 0.1 part by mass, 0.25 part by mass of a binder (substance name: polyvinyl alcohol) and water in a 50 kg ball mill for 24 hours was obtained. The obtained mixture was subjected to defoaming treatment for 30 minutes in a vacuum, and then molded products were obtained by pouring the mixture into a gypsum mold. Table 1 shows the formulation of the mixture. In addition, the silicon carbide powder used in Example 1 is a particle having a relatively small particle diameter to be an aggregate and a particle having a relatively small particle diameter contained in a bonded portion of the oxide-bonded silicon carbide sintered body. (Particles having a particle diameter smaller than that of the aggregate particles).

  The particle size of the silicon carbide powder used in Example 1 is 40% by mass of particles having a particle size of more than 100 μm and 200 μm or less, 5% by mass of particles of more than 50 μm and 100 μm or less, and more than 1 μm and less than 10 μm. The particles are 13% by mass, and the particles of 1 μm or less are 42% by mass. Of these particles, particles having a particle diameter of 10 μm or more are mainly aggregate particles.

Next, a sintered body (size: 400 mm × 400 mm × 10 mm) was obtained by firing the obtained molded body so as to have a maximum temperature of 800 ° C. in an air atmosphere. At this time, the temperature was raised from 20 to 600 ° C. over 12 hours, the temperature raising time from 600 to 800 ° C. was taken over 15 hours, the maximum temperature was maintained for 3 hours, and the temperature was lowered at 200 ° C./hr. By cooling the obtained sintered body, a crystal phase of NaV ₆ O _{15 and} a crystal phase of V ₂ O ₄ are precipitated in a bond part having a crystal phase of silicon dioxide as a main phase, respectively. A silicon sintered body (Example 1) was produced.

The crystal phase constituting the bonded portion of the obtained oxide-bonded silicon carbide sintered body was measured by X-ray diffraction (XRD). Table 2 shows the measurement results by X-ray diffraction (XRD). In Table 2, “◎” indicates that the crystal phase is extremely large, “◯” indicates that the crystal phase is large, “Δ” indicates that the crystal phase is confirmed even a little, and no crystal phase is confirmed. Was marked with x. In Example 1, a large number of crystal phases of silicon dioxide (SiO ₂ ) and silicon carbide (SiC) as main phases were confirmed, and a large number of crystal phases of NaV ₆ O ₁₅ were confirmed. _{Also, V 2 O 5, V 2} O 4, and the crystal phase of cristobalite is small has been confirmed.

  In addition, the characteristic values (creep resistance, fire crack, fire warp, dimensional expansion, thermal shock resistance, bulk specific gravity, and bending strength) of the obtained oxide-bonded silicon carbide sintered body were measured according to the measurement methods described above. went. The measurement results are shown in Table 2.

(Examples 2 to 5)
An oxide-bonded silicon carbide sintered body was obtained by the same method as in Example 1 except that the maximum temperature when firing the molded body was as shown in Table 1. The crystal phase constituting the bonded portion of the bonded body was measured by X-ray diffraction (XRD). Moreover, it measured according to the measuring method mentioned above about the characteristic value of the obtained oxide bond silicon carbide sintered body. The measurement results are shown in Table 2.

(Examples 6 to 10)
Oxide-bonded silicon carbide sintered in the same manner as in Example 1 except that silicon carbide powder having a different particle size from that of Example 1 was used and the maximum temperature when the molded body was fired was shown in Table 3 Got the body. The particle size of the silicon carbide powder is 5% by mass of particles having a particle size of more than 2000 μm and 3000 μm or less, 45% by mass of particles of 500 μm or more and 2000 μm or less, and 8% by mass of particles of more than 250 μm and 500 μm or less. Yes, particles of more than 90 μm and 250 μm or less are 13% by mass, and particles of 90 μm or less are 29% by mass. Of these particles, particles having a particle diameter of 10 μm or more are mainly aggregate particles. The crystal phase constituting the bonded portion of the obtained oxide-bonded silicon carbide sintered body was measured by X-ray diffraction (XRD). Moreover, it measured according to the measuring method mentioned above about the characteristic value of the obtained oxide bond silicon carbide sintered body. The measurement results are shown in Tables 3 and 4.

(Discussion)
The oxide-bonded silicon carbide sintered bodies of Examples 1 to 10 each containing a crystal phase of NaV ₆ O _{15 and} a crystal phase of V ₂ O _{4 in} the joints each have a creep resistance of 0.3 to 0.7 mm. The creep resistance was excellent .

In addition, the oxide-bonded silicon carbide sintered bodies of Examples 1 to 10 each contain the above crystal phase in the bonding portion, and are fired at a relatively low temperature of 800 to 1300 ° C. at the highest temperature during firing. Therefore, there was no problem with respect to firing cracks, firing warpage, and dimensional expansion .

Furthermore, the oxide-bonded silicon carbide sintered bodies of Examples 1 to 10 can obtain results with good thermal shock resistance, and the bending strength also includes a shelf board (setter) and a floor board for ceramic firing. It showed a value sufficient for use as a sheath, setter column, beam or roller, other kiln tools, and the like .

  The oxide-bonded silicon carbide material of the present invention includes, for example, a shelf plate (setter) for ceramic baking, a floor plate, a sheath, a setter column, a beam and a roller, other kiln tools, a wear-resistant material peculiar to SiC, etc. It can be suitably used in the field.

Claims (10)

A porous structure oxide-bonded silicon carbide sintered material composed of aggregate particles composed mainly of silicon carbide and consisting essentially of silicon carbide, and a bonding portion containing silicon dioxide for bonding the aggregate particles. Body,
The bonding part contains the crystalline phase of silicon dioxide as a main phase and contains NaV ₆ O ₁₅ and V ₂ O ₄ in the state of a crystalline phase of NaV ₆ O _{15 and} a crystalline phase of V ₂ O ₄ , respectively. An oxide-bonded silicon carbide sintered body. The total amount of vanadium (V) in the crystal phase of NaV ₆ O _{15 and} the crystal phase of V ₂ O ₄ is 0.05 to 2.8 mass% with respect to the oxide-bonded silicon carbide sintered body. The oxide-bonded silicon carbide sintered body according to claim 1. 3. The oxide bond according to claim 1, wherein both of the crystal phase of NaV ₆ O _{15 and} the crystal phase of V ₂ O ₄ are precipitated in a temperature lowering process of firing at a maximum temperature of 800 to 1300 ° C. 3. Silicon carbide based sintered body.   The ratio of components other than silicon carbide in the oxide-bonded silicon carbide sintered body is 1 to 15 mass%, and the oxide-bonded silicon carbide fired according to any one of claims 1 to 3. Union.   5. The oxide-bonded silicon carbide sintered material according to claim 1, wherein the bonding portion bonds the aggregate particles and covers at least a part of a surface of the aggregate particles. 6. body.   The oxide-bonded silicon carbide based sintered body according to any one of claims 1 to 5, wherein the bonding portion further contains a silicon carbide crystal phase. A method for producing an oxide-bonded silicon carbide sintered body having a porous structure in which aggregate particles composed mainly of silicon carbide and substantially composed of silicon carbide are bonded by a bonding portion containing silicon dioxide,
Step (A) of preparing a mixture by adding and mixing silicon dioxide powder, vanadium pentoxide (V ₂ O ₅ ) powder, and Na compound necessary for producing NaV ₆ O _{15 to} the aggregate particles;
A step (B) of obtaining the molded body by molding the obtained mixture;
A step (C) of obtaining the sintered body by firing the obtained molded body under firing conditions having a maximum temperature of 800 to 1300 ° C., and bonding the aggregate particles by the joint portion containing silicon dioxide; ,
A step of lowering the temperature of the obtained sintered body to cause a crystal phase of NaV ₆ O _{15 and} a crystal phase of V ₂ O ₄ to be precipitated in the joint portion having a crystal phase of silicon dioxide as a main phase (D And a method for producing an oxide-bonded silicon carbide sintered body.   The method for producing an oxide-bonded silicon carbide sintered body according to claim 7, wherein in the step (C), the time for raising the firing temperature from 600 ° C. to 800 ° C. is 10 to 20 hours.   The method for producing an oxide-bonded silicon carbide sintered body according to claim 7 and 8, wherein in the step (C), the compact is fired in an air atmosphere.   In the step (A), 0.5 to 5.0 parts by mass of silicon dioxide powder and 0.1 to 5.0 parts by mass of vanadium pentoxide powder are added to 100 parts by mass of the aggregate particles. The method for producing an oxide-bonded silicon carbide sintered body according to any one of claims 7 to 9, wherein a mixture is obtained.