Silicon nitride bonded silicon carbide refractories

Abstract

To provide a silicon nitride-bonded silicon carbide refractory capable of having excellent high-temperature properties.SOLUTION: The ratio of silicon carbide and silicon nitride in the silicon nitride-bonded silicon carbide refractory is such that silicon carbide is 65 mass% or more and 75 mass% or less, and silicon nitride is 25 mass% or more and 35 mass% or less. A β ratio of silicon nitride in the silicon nitride-bonded silicon carbide refractory is 75% or more and 90% or less, a calcium component of 0.05 mass% or more and 0.14% mass% or less based on the total of silicon carbide and silicon nitride is contained, a bulk specific gravity is 2.36 g / cm3 or more and 2.66 g / cm3 or less, and metallic silicon is not detected by X-ray diffraction at least in a 5 mm thick region from a surface.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a silicon nitride-bonded silicon carbide refractory, and more particularly to a silicon nitride-bonded silicon carbide refractory used in high-temperature heating devices exceeding 1000°C, such as a radiant heating plate used to control the temperature of molten glass when producing plate glass by fusion molding. [Background technology]

[0002] Silicon nitride-bonded silicon carbide refractories have excellent thermal conductivity and durability, and are therefore used in a variety of applications, such as kiln tools. For example, they can also be used as radiant heating plates used to control the temperature of molten glass when producing sheet glass by fusion molding. One known apparatus for producing sheet glass by fusion molding houses a forming body inside an enclosure defined by a first side heating plate, an upper plate, and a second side heating plate, and radiates heating the first side surface of the forming body by the first side heating plate and the second side surface by the second side heating plate (see Patent Document 1). In this apparatus, for example, molten glass is introduced into a trough-shaped portion of the forming body, overflows from the top, and flows down the side surfaces to form a first glass ribbon and a second glass ribbon, which then join at the bottom of the forming body to form a single third ribbon. The first and second side heating plates, which are radiant heating plates, are heated by heating elements arranged behind them and reach high temperatures exceeding 1000°C, so the silicon nitride-bonded silicon carbide refractory material that makes them up is required to have excellent high-temperature properties exceeding 1000°C.

[0003] Various reports have been published on silicon nitride-bonded silicon carbide refractories. For example, Patent Document 2 discloses a method for producing a silicon nitride-bonded silicon carbide refractory, which comprises firing a molded body containing at least 5-20 wt% Si and 1-10 wt% β-Si3N4, primarily composed of SiC, in an N2 gas atmosphere, so that the β-ratio of Si3N4 in the fired refractory is 55% or more and the residual Si in the refractory is substantially 0 wt%. According to the examples in Patent Document 1, the fired silicon nitride-bonded silicon carbide refractory produced by this method comprises 69-86 wt% SiC, 14-31 wt% Si3N4, a β-ratio of Si3N4 of 55-71%, and 0% residual Si. According to the invention described in Patent Document 2, by eliminating residual Si in the refractory after firing and increasing the β ratio, strong silicon nitride bonds can be obtained, and a highly tough silicon nitride-bonded silicon carbide refractory with improved oxidation resistance, heat resistance, high-temperature bending strength, and thermal shock resistance can be produced.

[0004] Furthermore, for example, Patent Document 3 discloses a nitride-bonded SiC refractory comprising 60-90 mass% SiC aggregate particles, 8-35 mass% SiN and / or SiON grain boundary bonds, 1.0-15.0 mass% grain boundary glassy and / or crystalline phases containing SiO, AlO, CaO, and FeO, and 0.05-2.0 mass% metallic Si, and also containing 0.2-1.0 mass% calcium (calculated as CaO). According to the invention described in Patent Document 3, the inclusion of a predetermined amount of metallic Si improves high-temperature properties and prevents crack propagation. Furthermore, the inclusion of a predetermined amount of Ca in the grain boundary glass phase improves oxidation resistance, thermal shock resistance, control of the amount of cristobalite formation, and control of the amount of glass phase. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-27947 [Patent Document 2] Japanese Patent Application Publication No. 3-223167 [Patent Document 3] Japanese Patent Application Publication No. 4-114969 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the invention described in Patent Document 2, the bulk density is not specified, the Si3N4 content tends to be low, and the β ratio of the Si3N4 example is substantially low, so the thermal shock resistance is not sufficient. Furthermore, although the toughness is high, the creep resistance at high temperatures is insufficient, and when used in high-temperature heating equipment, the service life is not satisfactory.

[0007] Furthermore, the invention described in Patent Document 3 contains metallic Si, and therefore when used in air at high temperatures, the metallic Si, particularly in the surface layer, turns into SiO2 and cristobalite, leading to strength deterioration and breakage. Also, because it contains a large amount of calcium, it does not have sufficient creep resistance at high temperatures, and when used in high-temperature heating equipment, it does not have a satisfactory service life.

[0008] The present invention has been made in light of the above problems, and has as its object to provide a silicon nitride-bonded silicon carbide refractory that can obtain excellent high-temperature properties that enable a longer service life. [Means for solving the problem]

[0009] The silicon nitride bonded silicon carbide refractory of the present invention has a ratio of silicon carbide to silicon nitride of 65% by mass to 75% by mass and 25% by mass to 35% by mass, the β ratio of silicon nitride is 75% to 90% and the calcium content is 0.05% to 0.14% by mass relative to the total of silicon carbide and silicon nitride, and has a bulk specific gravity of 2.36 g / cm. 3 More than 2.66g / cm 3 or less, and metallic silicon is not detected by X-ray diffraction in at least a 5 mm thick region from the surface. [Effects of the Invention]

[0010] The silicon nitride-bonded silicon carbide refractory of the present invention has a silicon nitride β ratio, calcium component concentration, and bulk specific gravity that fall within predetermined ranges, and metallic silicon is not detected by X-ray diffraction at least in the thickness region of 5 mm from the surface. This results in high high-temperature strength in an oxidizing atmosphere, thermal shock resistance, and creep resistance, as well as excellent high-temperature properties. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a diagram illustrating a method for measuring high-temperature bending strength. [Figure 2] FIG. 2 is a diagram illustrating a method for measuring creep resistance. [Figure 3] FIG. 1 is an X-ray diffraction diagram showing the detection of metallic silicon in a 5 mm thick region from the surface of a sintered body. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0013] A silicon nitride-bonded silicon carbide refractory according to one embodiment of the present invention is, for example, a refractory in which silicon carbide (SiC) aggregate particles are bonded by grain boundary bonds containing silicon nitride (Si3N4) and silicon carbide. The ratio of silicon carbide to silicon nitride in this silicon nitride-bonded silicon carbide refractory is 65% by mass to 75% by mass, and 25% by mass to 35% by mass. This provides improved high-temperature strength, thermal shock resistance, and creep resistance. Furthermore, if the silicon carbide content is less than 65% by mass and the silicon nitride content is more than 35% by mass, problems such as microcracks due to excessive reaction of fine powder can occur. Furthermore, if the silicon carbide content is more than 75% by mass and the silicon nitride content is less than 25% by mass, problems such as low strength due to insufficient reaction of fine powder can occur.

[0014] The β-ratio (β-phase ratio) of silicon nitride in the silicon nitride-bonded silicon carbide refractory is 75% or more and 90% or less. This provides the effect of improving high-temperature strength and thermal shock resistance. The total ratio of silicon carbide and silicon nitride to the entire silicon nitride-bonded silicon carbide refractory is, for example, preferably 95% by mass or more, more preferably 97% by mass or more, and even more preferably 99% by mass or more.

[0015] The silicon nitride-bonded silicon carbide refractory also contains calcium (Ca). That is, calcium is contained as a chemical component such as a compound or element. The concentration of the calcium component in the silicon nitride-bonded silicon carbide refractory is 0.05% by mass or more and 0.14% by mass or less relative to the total of silicon carbide and silicon nitride. This improves high-temperature strength and creep resistance. If the calcium component is less than 0.05% by mass, problems such as reduced high-temperature strength and creep resistance occur, while if it exceeds 0.14% by mass, problems such as reduced thermal shock resistance occur. The calcium component is present, for example, mainly in the form of calcium oxide (CaO) at grain boundary bonds.

[0016] The bulk density of silicon nitride bonded silicon carbide refractories is 2.36 g / cm 3 More than 2.66g / cm 3 This ensures proper tissue packing and improves high-temperature strength. 3 If it is less than 2.66 g / cm, problems such as low strength due to weakened tissue will occur. 3 If it is over 100%, the structure becomes too dense, which causes a problem of reduced thermal shock resistance.

[0017] Silicon nitride-bonded silicon carbide refractories are free of metallic silicon in at least the first 5 mm of the surface, and metallic silicon is not detectable by X-ray diffraction. This improves hot strength through the nitriding reaction. Furthermore, if metallic silicon remains in the surface layer, it can undergo oxidation to form cristobalite, causing localized abnormal expansion and resulting in surface cracks and other defects.

[0018] Furthermore, the silicon nitride-bonded silicon carbide refractory may contain other components, and preferably contains, for example, iron (Fe). That is, it is preferable that iron is contained as a chemical component such as a compound or element. The concentration of the iron component in the silicon nitride-bonded silicon carbide refractory is 0.05 mass% or more and 0.5 mass% or less based on the total of silicon carbide and silicon nitride. This further improves the hot strength and creep resistance. The iron component is present, for example, mainly as iron oxide at grain boundary bonds.

[0019] This silicon nitride-bonded silicon carbide refractory can be manufactured, for example, as follows. First, raw materials such as silicon carbide aggregate, silicon carbide fine powder, silicon nitride fine powder, metallic silicon powder, calcium oxide (CaO) powder as a raw material for the calcium component, and, if necessary, raw materials for other components such as iron, are prepared and weighed. It is preferable that the particle size of the silicon carbide aggregate be 0.3 mm to 3.0 mm, the particle size of the silicon carbide fine powder be 100 μm or less, the particle size of the silicon nitride fine powder be 0.1 μm to 10 μm, the particle size of the metallic silicon powder be 50 μm or less, and the particle size of the calcium oxide powder and other raw material components be 20 μm or less.

[0020] Next, for example, a solvent such as water, a dispersant, a binder, etc. are added to the raw materials and kneaded. Subsequently, for example, the kneaded product is poured into a mold, cured in the mold for a predetermined time, removed from the mold, and dried naturally and at a high temperature for a predetermined time. Next, it is fired in a nitrogen gas atmosphere. The firing temperature is preferably maintained at a maximum temperature of 1430°C to 1460°C, and the maximum temperature is preferably maintained for 8 to 12 hours.

[0021] As described above, according to this embodiment, the β ratio, calcium component concentration, and bulk specific gravity of silicon nitride are set within predetermined ranges, and metallic silicon is not detected by X-ray diffraction at least in the region 5 mm thick from the surface. Therefore, it is possible to provide a silicon nitride-bonded silicon carbide refractory having excellent high-temperature properties, such as high strength at high temperatures in an oxidizing atmosphere, higher thermal shock resistance, and creep resistance.

[0022] Therefore, this silicon nitride-bonded silicon carbide refractory is particularly suitable as a component for use in high-temperature heating equipment exceeding 1000°C, such as a radiant heating plate used to control the temperature of molten glass when producing plate glass by fusion molding. It can also be used, for example, in casting nozzles for non-ferrous metals (such as aluminum and copper) that require high-temperature properties, melting immersion tubes, or heat treatment base plates for ferrites, multilayer ceramic capacitors, etc. [Example]

[0023] Example 1 First, the raw materials were prepared and weighed: silicon carbide aggregate with a particle size of 0.3 mm to 3.0 mm, silicon carbide fine powder with a particle size of 100 μm or less, silicon nitride fine powder with a particle size of 0.1 μm to 10 μm, metal silicon fine powder with a particle size of 30 μm or less, and calcium oxide powder with a particle size of 10 μm or less. The blending ratios of the silicon carbide aggregate, silicon carbide fine powder, silicon nitride fine powder, and metal silicon fine powder were 50 mass% silicon carbide aggregate, 25 mass% silicon carbide fine powder, 10 mass% silicon nitride fine powder, and 15 mass% metal silicon fine powder. The blending ratio of calcium oxide powder was 0.18 mass% of the total of the silicon carbide aggregate, silicon carbide fine powder, silicon nitride fine powder, and metal silicon fine powder. The β ratio of the raw material silicon nitride fine powder was 82%.

[0024] Next, water, a polycarboxylic acid ammonium salt as a dispersant, and an acrylic resin binder as a binder were added to the raw materials and kneaded to obtain a slurry. The blending ratios of these were 10% by mass of water, 0.1% by mass of dispersant, and 1% by mass of binder relative to the total of the silicon carbide aggregate, silicon carbide fine powder, silicon nitride fine powder, and metal silicon fine powder. Kneading was carried out for 30 minutes using a 100 L Dalton mixer.

[0025] The slurry was then poured into a mold and cast under vibration of 25 Hz or higher. The mold had a rectangular shape measuring 50 mm x 1200 mm x 4000 mm. After 100 hours of mold curing, the mixture was removed from the mold and naturally dried for 100 hours, followed by high-temperature drying at 100°C for 100 hours. The mixture was then fired in a nitrogen gas atmosphere at a maximum temperature of 1450°C for 10 hours. This resulted in a fired silicon nitride-bonded silicon carbide refractory body.

[0026] (Examples 2 and 3 and Comparative Examples 1 and 2) Silicon nitride-bonded silicon carbide refractories were produced in the same manner as in Example 1, except that the ratio of silicon carbide to silicon nitride in the silicon nitride-bonded silicon carbide refractories was changed by changing or adjusting the blending ratio of silicon carbide fine powder and metal silicon fine powder in the raw materials. Note that in Comparative Example 1, the ratio of silicon nitride in the silicon nitride-bonded silicon carbide refractories was made to be higher, and in Comparative Example 2, the ratio of silicon carbide in the silicon nitride-bonded silicon carbide refractories was made to be higher.

[0027] (Evaluation method) <Method for determining silicon carbide and silicon nitride in fired body> The sintered body was crushed into fine powder, and the resulting samples were subjected to quantitative analysis using X-ray fluorescence. The quantitative analysis method used was the Fundamental Parameter Method (FP). The FP method is a quantitative calculation method using known parameters and measured X-ray fluorescence intensity. Since the Si content of SiC, Si3N4, and metallic silicon is calculated as total Si, the SiC, Si3N4, and metallic silicon contents were calculated from the N and C analytical values, and the abundance ratios of SiC and Si3N4 (each relative to the total of SiC and Si3N4) excluding metallic silicon were calculated. Furthermore, since the inclusion of oxygen during nitriding sintering produces Si2ON2 and SiO2, the absence of Si2ON2 and SiO2 peaks was confirmed in advance by powder X-ray diffraction.

[0028] <Method for measuring the β ratio of silicon nitride in fired body> The fired body was pulverized to obtain a fine powder sample, which was analyzed using a powder X-ray diffractometer to measure the first and second peaks of α-Si3N4 and β-Si3N4. The peak height ratio was calculated using the following formula. Beta ratio = (A+B) / (A+B+C+D) A: First peak of β-Si3N4 B: Second peak of β-Si3N4 C: First peak of α-Si3N4 D: Second peak of α-Si3N4

[0029] <Method for determining calcium concentration in fired body> The sintered body was crushed into a fine powder, which was then pressed into a mold. The resulting sample was quantitatively analyzed using fluorescent X-rays to calculate the ratio of silicon carbide and silicon nitride to the total. The quantitative analysis method used was the FP method.

[0030] <Method for measuring bulk specific gravity of fired bodies (JIS R 2205)> Using a sample measuring 20mm x 20mm x 100mm, the dry weight, submerged weight, and hydrated weight of the sample were measured and calculated using the following formula. Bulk density = dry weight / (wet weight - submerged weight) Dry weight: Weight measured after drying the sample at 110°C for 24 hours Weight in water: The sample is placed in a boiling tank, boiled for 4 hours, cooled, and then suspended in water to measure the weight. Wet weight: The weight of the sample taken out of the water and wiped with a wet cloth

[0031] <Method for detecting metallic silicon in a 5 mm thick region from the surface of a sintered body> A 5mm square x 5mm x 5mm deep cut was made from the surface of the sintered body, and then the cut was pulverized to obtain a fine powder sample, which was analyzed using a powder X-ray diffractometer to confirm the presence or absence of the first peak of metallic silicon.

[0032] <High temperature strength in oxidizing atmosphere> Measurements were performed based on the high-temperature bending strength measurement method (JIS-R2656) as follows. First, as shown in Figure 1, a sample S measuring 20 mm x 20 mm x 100 mm was used and placed in a furnace with both ends supported by support rolls R at a 60 mm interval. The sample was then heated to 1400°C at a temperature increase rate of 100°C per hour and held for 2 hours. Next, using a materials testing machine capable of maintaining a constant loading rate, a load of 0.25 MPa / s was applied to the center of the sample to measure the maximum load at which the sample broke under three-point bending. The three-point bending strength was calculated using the following formula. A calculated three-point bending strength of 50 MPa was evaluated as excellent, a value of 30 MPa or greater but not greater than 50 MPa was evaluated as good, and a value of 30 MPa or less was evaluated as poor. 3-point bending strength (MPa) = 3WL1 / 2bd 2 W: Maximum load (N) L1: Center distance between support rolls R = 60 mm b: Width of sample S = 20 mm d: thickness of sample S = 20 mm

[0033] <Thermal shock resistance (JIS-R2657)> A sample measuring 230 mm x 114 mm x 65 mm was inserted into the furnace so that approximately one-third (76 mm) of its length from the heating surface (114 mm x 65 mm) was outside the furnace. After the furnace temperature dropped to 1200°C, the sample was held at 1200°C for 15 minutes. The sample was then removed from the furnace and cooled by immersing one-third of the inserted portion in running water for three minutes. After removing the sample from the water, it was air-cooled for 12 minutes. The occurrence of cracks and elongation were recorded. This heating, water-cooling, and air-cooling cycle was repeated until the sample peeled off. If the sample did not peel off, it was repeated 10 times. Results were evaluated as follows: no peeling after 10 repetitions, ◎; peeling after 6 to 10 repetitions, 〇; and peeling after 1 to 5 repetitions, ×.

[0034] <Creep resistance> As shown in Figure 2, sample S, measuring 200 mm x 30 mm x 10 mm, was placed in the furnace with both ends supported at 160 mm intervals, and a pressure of 20 kgf / cm was applied to the center of sample S. 2 A weight w was placed on the sample, which added a load of 100°C, and the sample was heated to 1200°C at a temperature increase rate of 100°C per hour. After holding the temperature for 24 hours, the sample was cooled to room temperature, and the deformation of the sample was measured. The load W applied by the weight w was calculated using the following formula for four-point bending strength. The amount of bending was calculated as follows: amount of bending = initial amount of bending - amount of bending after the test. As a result, sample S was evaluated as having a deformation (amount of bending) of 0 to 0.03 mm (◎), a value of over 0.03 to 0.10 mm (◯), and an x value of over 0.10 mm. σ=3W(L2-L3) / 2bd 2 σ=20kgf / cm 2 W = Weight w: approx. 3.3 kg L2 = span 160 mm L3 = width of weight w 40mm b = width of sample S, 30 mm d = thickness of sample S, 10 mm

[0035] (Evaluation results) The evaluation results for Examples 1 to 3 and Comparative Examples 1 and 2 are shown in Table 1. As shown in Table 1, Examples 1 to 3 provided good results in terms of high-temperature strength in an oxidizing atmosphere, thermal shock resistance, and creep resistance. In contrast, Comparative Example 1, which had a high proportion of silicon nitride, and Comparative Example 2, which had a high proportion of silicon carbide, provided insufficient high-temperature strength in an oxidizing atmosphere and thermal shock resistance. In other words, it was found that excellent high-temperature properties that enable a longer service life can be obtained by setting the proportions of silicon carbide to silicon nitride to between 65% and 75% by mass for silicon carbide and between 25% and 35% by mass for silicon nitride.

[0036] [Table 1]

[0037] (Examples 4 and 5 and Comparative Examples 3 and 4) Silicon nitride-bonded silicon carbide refractories were produced in the same manner as in Example 1, except that the β ratio of silicon nitride in the silicon nitride-bonded silicon carbide refractories was changed by changing or adjusting the β ratio in the silicon nitride fine powder in the raw materials. Note that Comparative Example 3 was designed to have a low β ratio, and Comparative Example 4 was designed to have a high β ratio. Examples 4 and 5 and Comparative Examples 3 and 4 were also evaluated in the same manner as in Example 1. The evaluation results are shown in Table 2 together with the results of Example 1.

[0038] As shown in Table 2, Examples 1, 4, and 5 achieved good results in high-temperature strength in an oxidizing atmosphere, thermal shock resistance, and creep resistance. In contrast, Comparative Example 3, which had a low β ratio, had insufficient thermal shock resistance and creep resistance, and Comparative Example 4, which had a high β ratio, had insufficient thermal shock resistance. In other words, it was found that by setting the β ratio of silicon nitride to between 75% and 90%, excellent high-temperature properties that enable a longer service life can be obtained.

[0039] [Table 2]

[0040] (Examples 6 and 7 and Comparative Examples 5 and 6) Silicon nitride bonded silicon carbide refractories were produced in the same manner as in Example 1, except that the bulk density of the silicon nitride bonded silicon carbide refractories was changed by changing or adjusting the particle sizes of the silicon carbide fine powder and silicon nitride fine powder in the raw materials. Comparative Example 5 was designed to have a low bulk density, while Comparative Example 6 was designed to have a high bulk density. Examples 6 and 7 and Comparative Examples 5 and 6 were also evaluated in the same manner as in Example 1. The evaluation results are shown in Table 3 together with the results of Example 1.

[0041] As shown in Table 3, Examples 1, 6, and 7 all achieved good results in terms of high-temperature strength in an oxidizing atmosphere, thermal shock resistance, and creep resistance. In contrast, Comparative Example 5, which had a low bulk density, had insufficient high-temperature strength in an oxidizing atmosphere and thermal shock resistance, and Comparative Example 6, which had a high bulk density, had insufficient thermal shock resistance. That is, when the bulk density was 2.36 g / cm 3 More than 2.66g / cm 3 It has been found that by doing as follows, it is possible to obtain excellent high-temperature characteristics that enable a longer service life.

[0042] [Table 3]

[0043] (Comparative Example 7) Silicon nitride-bonded silicon carbide refractories were produced in the same manner as in Example 1, except that the time for which the slurry was left to stand after preparation before molding was changed or adjusted so that metallic silicon remained in a region 5 mm deep from the surface of the silicon nitride-bonded silicon carbide refractory. Comparative Example 7 was also evaluated in the same manner as in Example 1. The evaluation results are shown in Table 4 together with the results of Example 1, and the X-ray diffraction diagram is shown in Figure 3. For reference, the X-ray diffraction diagram of Comparative Example 3 is also shown in Figure 3.

[0044] As shown in FIG. 3, the first peak of metallic silicon was not detected in Example 1 and Comparative Example 3, whereas the first peak of metallic silicon was detected in Comparative Example 7. That is, it was found that metallic silicon remained in the 5 mm thickness region from the surface in Comparative Example 7. Furthermore, as shown in Table 4, Example 1 obtained good results in high-temperature strength in an oxidizing atmosphere, thermal shock resistance, and creep resistance, whereas Comparative Example 7 had insufficient high-temperature strength in an oxidizing atmosphere. That is, it was found that excellent high-temperature properties that enable a longer service life can be obtained by preventing metallic silicon from being detected in the 5 mm thickness region from the surface.

[0045] [Table 4]

[0046] (Examples 8 and 9 and Comparative Examples 8 and 9) Silicon nitride bonded silicon carbide refractories were produced in the same manner as in Example 1, except that the concentration of the calcium component in the silicon nitride bonded silicon carbide refractories was changed by changing or adjusting the blending ratio of calcium oxide powder to the total of silicon carbide aggregate, silicon carbide fine powder, silicon nitride fine powder, and metal silicon fine powder in the raw materials. Comparative Example 8 did not add calcium oxide powder, and Comparative Example 9 had a higher calcium component concentration. Examples 8 and 9 and Comparative Examples 8 and 9 were also evaluated in the same manner as in Example 1. The evaluation results, along with the results of Example 1, are shown in Table 5.

[0047] As shown in Table 5, Examples 1, 8, and 9 all achieved good results in terms of high-temperature strength in an oxidizing atmosphere, thermal shock resistance, and creep resistance. In contrast, Comparative Example 8, which had a low calcium content, exhibited insufficient high-temperature strength in an oxidizing atmosphere and creep resistance, while Comparative Example 9, which had a high calcium content, exhibited insufficient thermal shock resistance. In other words, it was found that by adjusting the calcium content to 0.05% by mass or more and 0.14% by mass or less relative to the total of silicon carbide and silicon nitride, excellent high-temperature properties that enable a longer service life can be obtained.

[0048] [Table 5]

[0049] Although the present invention has been described above with reference to the embodiments, the present invention is not limited to the above embodiments and can be modified in various ways. For example, although the above embodiments specifically describe the manufacturing method, the present invention is not limited to this. [Industrial Applicability]

[0050] The present invention can be used particularly for components of high temperature heating devices at temperatures exceeding 1000°C. [Explanation of symbols]

[0051] S...Sample, R...Support roll, w...Weight

Claims

1. A silicon nitride-bonded silicon carbide refractory, wherein the ratio of silicon carbide to silicon nitride is 65% by mass or more and 75% by mass or less, and silicon nitride is 25% by mass or more and 35% by mass or less, The β ratio of the silicon nitride is 75% or more and 90% or less, The calcium component is contained in an amount of 0.05% by mass or more and 0.14% by mass or less based on the total amount of the silicon carbide and the silicon nitride, Bulk density is 2.36 g / cm ３ 2.66g / cm or more ３ is as follows: Metallic silicon is not detected by X-ray diffraction in at least a 5 mm thick region from the surface. A silicon nitride bonded silicon carbide refractory characterized by:

2. 2. The silicon nitride bonded silicon carbide refractory according to claim 1, wherein the iron content is 0.05 mass % or more and 0.5 mass % or less based on the total of the silicon carbide and the silicon nitride.

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