JPS6197165A - Beta' sialon bonding silicon carbide material and manufacture - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a β'sialon-bonded silicon carbide material that has excellent high-temperature strength, oxidation resistance, corrosion resistance, heat resistance, and wear resistance, and is suitable for use in various applications requiring these properties. Regarding materials and their manufacturing methods.

In general, a bonded silicon carbide-based material is composed of an aggregate phase of silicon carbide particles having features such as high heat resistance, thermal conductivity, hardness, and low thermal expansion, a binder phase that binds the aggregate phase, and pores. If the apparent porosity of these bonded silicon carbide materials is within a suitable range, that is, 10-odds of inch or less, the characteristics of the materials will depend on the material of the binder phase. Therefore, the material of the binder phase is an extremely important factor for the bonded silicon carbide material. Therefore, it is well known that many types of bonded phases have been developed and put into practical use. The main conventional examples are shown below.

Bonded silicon carbide materials that use silicate as a binder phase have drawbacks, such as a narrow temperature range in which they exhibit oxidation resistance and a low temperature at which their hot strength rapidly decreases, due to the inherent properties of silicate. It is something.

In addition, bonded silicon carbide materials that use one or both of silicon oxynitride and silicon nitride as a binder phase have a lower temperature limit at which they exhibit oxidation resistance compared to those that use the above-mentioned silicate as a binder phase. Moving to the high temperature side, the oxidation resistance is low at relatively low temperatures, for example around 1000°C, and the high temperature strength at 1400°C is significantly lower than the room temperature strength.

Furthermore, although sialon-based bonded silicon carbide refractories are disclosed in Japanese Patent Publication No. 57-267 and Japanese Patent Publication No. 57-268, these conventionally known refractories have improved corrosion resistance and thermal shock resistance. However, as a heat-resistant material, its bending strength cannot be said to be sufficiently satisfactory. In other words, since the reactive silicon carbide material produced by silicifying carbon (which is included in the formed body together with silicon carbide particles) inevitably contains free silicon, It has the disadvantage that its bending strength rapidly decreases, and it also has the disadvantage that it can only be used in applications where a silicon vapor atmosphere is permissible.

As described above, all of the bonded silicon carbide materials with various binder phases made by conventional technology cannot take full advantage of the excellent features of silicon carbide, and the high temperature strength and oxidation resistance of these materials are insufficient. Therefore, it was not possible to show a satisfactory lifespan as a heat-resistant material. In other words, in conventional bonded silicon carbide-based wear-resistant materials, the binder phase surrounding the silicon carbide grains is softer, so even though there is a phase of hard silicon carbide grains, the binder phase wears out first, and as time goes on, the silicon carbide grains It did not have sufficient durability against powder abrasion due to the abrasion mechanism in which the (aggregate phase) peels off.

It is an object of the present invention to provide a bonded silicon carbide material that can overcome the drawbacks of the conventional bonded silicon carbide materials as described above and take advantage of the advantages of silicon carbide.

In order to achieve the above object, the present inventors conducted various studies and found that the binder phase has the general formula Si, -, AI, O, N,
The value of 2 in the formula 'i:0<
By using materials with z≦3, it is possible to obtain materials with high high temperature strength, oxidation resistance, corrosion resistance, and abrasion resistance rt-, which were not seen in conventional examples, and that these materials have We have discovered a manufacturing method that can be easily obtained. The present invention is based on these findings. In other words, the material of the present invention is characterized by a maximum of 4 to 4
Consisting of an aggregate phase of silicon carbide particles having a particle size of 1 mm, and a binder phase of β' sialon represented by the general formula Sl, AI, O, N, (where 0 < z ≤ 3), The weight ratio of the aggregate phase and binder phase is 90/10~7 o/a
O, and the apparent porosity is 10 cm or less.

In addition, the manufacturing method of these materials is characterized by a maximum of 4~ill! The aggregate phase of silicon carbide particles having a particle size of of metal silicon, aluminum, and silicic acid fine powder are mixed and molded, and after drying the molded product, the temperature is 1300 to 160°C.
Calcined at 0°C under normal pressure in a non-oxidizing atmosphere containing nitrogen,
The purpose is to have an apparent porosity of 10 cm or less.

In the material of the present invention, the silicon carbide particles of the aggregate phase (hereinafter simply referred to as Gray 7) must contain between 4 and 1 particle at most. This is because those containing no coarse particles and those containing more than 4 particles at most have low density and insufficient strength and oxidation resistance. In addition, the reason for setting the value of 2 in the general formula of β′sialon to t″O<z≦3 is that 2
When the value of is O, the β'sialon bonded phase of the present invention cannot be obtained, and when 2 exceeds 3, the glass phase tends to increase, resulting in poor strength, especially high-temperature strength, and a stable bonded phase. This is because it cannot be done. The preferred range of the value of 2 is 1 to
It is 2.

The weight ratio of the aggregate phase to the binder phase is in the range of 90/1.0 to 70/30. That is, if the content of the binder phase component is less than 10% by weight, the content of the aggregate phase component will exceed 90% by weight, making it impossible to secure the desired high strength. If the content exceeds 70% by weight, the content of the aggregate phase component will be relatively too low, less than 70% by weight, and the desired wear resistance will not be obtained, and the desired strength will not be achieved despite the large amount of binder phase component. Can not do it.

Preferably the ratio is between 85/15 and 75/25.

Furthermore, if the apparent porosity exceeds 10%, the strength, oxidation resistance, and abrasion resistance will be insufficient. Preferably, the apparent porosity is 8 inches or less.

Next, a method for manufacturing the β' sialon bonded silicon carbide material as described above will be explained.

The brain used for the aggregate phase is a commercially available first grade product (SiC974 or higher) α that has been adjusted to a maximum particle size of 4 mm or less by the Acheson method.
・SiC, and the coarse particles of the brane are preferably prepared from dense sintered α・StC using a sintering method that has good crystal development, density, and filling properties. Needless to say, this includes branes prepared from scraps of sintered α-SIC material (although the quality is ensured to be higher than that of the Acheson method).

The silicon and aluminum powders used have a particle size of 20 μm or less, preferably 10 μm or less.

It is preferable to use coated powders that can prevent deterioration of the powder surface during handling of these powders before the firing process, such as silicon and aluminum powders coated with linear saturated fatty acids or salts thereof. These coating materials are selected from those that decompose and disappear at a relatively low temperature during the firing process (much lower than the nitriding reaction initiation temperature).

Examples of the silicic acid powder used include chemically high-purity quartz powder, quartz glass powder, evaporated silica, vapor phase silica, and wet precipitation silica, and evaporated silica is most suitable.

The reason for this is that when evaporated silica is used, the green density of the molded product made of the constituent components of the present invention is the highest, and after firing, the formation of the binder phase and β'sialon is the most efficient, and the thus obtained material This is because the characteristics of the present invention are exhibited to a high degree.

Combined with brane, which becomes the aggregate phase, and the final (after firing)
The details of the chemical reactions that occur during firing at temperatures below 1600°C in a non-oxidizing atmosphere containing silicon powder, aluminum powder, and silicate powder, which are the starting materials for β'sialon, which is the binder phase, are unknown, but a general overview is available. The following reactions can be considered.

3(4-Z) St +2ZAl +ZSIO,+
(8-Z)N, -+2 (5la-zAlzOzNs
-z) The blending ratio of the starting materials is the weight ratio of silicon carbide aggregate component/bond phase component (bond phase component; β′sialon0<z
≦3) and β1 sialon based on the above reaction formula.
determined according to the value of

The binder phase component starting materials 3 yuzu and the aggregate phase component Blaine are thoroughly mixed in a predetermined mixing ratio in a mixer, for example, an Eirich mixer. Prior to this mixing, it is preferable to mix three predetermined starting materials for the binder phase components in advance using a powder mixer, for example, a V-type mixer, prepare the mixture, and then mix Blaine and the mixture as described above. . Next, a general primary binder such as PVA, dextrin, lignin, methyl cellulose, etc. and water are added to this mixture and thoroughly kneaded to obtain a mixed wire product. After kneading, a general molding method such as a mold is used.
A molded body can be obtained by axial pressing, ramming, vibration pressing, cold isostatic pressing, extrusion, casting, or the like. However, depending on the molding method, suitable primary binders and water bodies generally vary, and unique additives such as plasticizers, dispersants, peptizers, lubricants, etc. are used. After drying the obtained compact, it is placed in an atmospheric furnace and heated under normal pressure in a non-oxidizing atmosphere containing nitrogen, such as nitrogen gas alone, or a mixture of nitrogen gas and an inert gas such as argon or neon, or nitrogen gas. Mixed gas atmosphere of gas, hydrogen gas, ammonia gas, etc. f, taoo ~ 160
By heating and reacting at 0° C., a β′-sialon bonded silicon carbide material can be obtained. In the present invention, the reason why the firing temperature is limited to the above-mentioned temperature range is that at temperatures below 1300°C, the formation reaction rate of β'sialon is slow and a long holding time is required;
Even if the temperature is lower than 1600°C, there is almost no contribution to the formation (speed and rate) of β'sialon, and this only increases the firing cost, so firing at a temperature higher than 1600°C is uneconomical. In a preferred firing embodiment, 200°C/
The sample is heated to 1450° C. at a heating rate of h and maintained at this temperature for 8 hours or more.

When the minerals of the product of the present invention thus obtained were identified by powder Xfi1 diffraction, α·81C and β′sialon were detected, and some extremely weak unknown peaks that were difficult to identify were observed. Furthermore, the rate of weight change before and after firing (the mold weight before firing and the mold weight after firing) of the molded article of the present invention was at least about 90 or more of the theoretically calculated value based on the above reaction formula. The reason why it is not 100% is not clear, but possible causes include the influence of impurities in the raw materials used, the volatilization loss of silicon and aluminum during the firing process, and the formation of unidentifiable substances. From the above mineral identification and weight change rate, it was confirmed that the product of the present invention essentially consists of an aggregate phase of αΦStC and a binder phase of β′sialon.

The features of the present invention are listed below.

(1) As a material, a. It has extremely high mechanical strength at room temperature and high temperature (1400°C).

(b) The strength at 1400°C is greater than that at room temperature, that is, even at a high temperature of 1400°C, the strength does not decrease, but rather maintains a high strength.

It also has extremely good oxidation resistance over a wide temperature range.

:r-,l) Body wear (ablation and erosion)
K: Shows excellent abrasion resistance.

It exhibits excellent resistance to erosion and corrosion of molten non-ferrous metals, especially copper and copper alloys.

(2) In the manufacturing method A. All raw materials used are easily available commercially available products.

B. High density can be achieved by specifying the maximum grain size of the branes used.

First, the dimensional changes (expansion or contraction) and deformation of the molded body before and after firing are negligibly small. Therefore, post-firing machining is unnecessary in most cases #1.

Otori firing is satisfactory at low temperatures that are easily obtained.

In particular, materials having the above-mentioned outstanding features can be produced by such an inexpensive method due to the features of the above-mentioned production method.

The ``β' siatetrabond silicon carbide material of the present invention has various excellent features as described above, and therefore can exhibit remarkable effects in a wide range of industrial fields such as those described below.

(1) Skid rails for steel industry heat treatment furnaces, skid tongues, radiant heat transfer tubes, immersed combustion tubes, various storage tubes, blast furnace lining refractories, etc.

(2) Nonferrous industrial melting furnace lining refractories, gutter materials, stirring impellers, Stokes, etc.

(3) Kiln tools such as shelves, supports, saggers, hanging rods, and base plates for ceramic industrial firing furnaces, rollers for a-5p hearth furnaces, hearth plates, etc.

(4) Sliding surface lining materials for transportation routes and storage tanks for various industrial raw materials, products, and waste, spray nozzles, heat exchange materials, slurry pump components, etc.

The present invention will be explained in detail below.

Example 1 Nine commercially available first grade silicon carbide particles (s
IC content: 97% by weight or more), metallic silicon powder (average particle size: 8μ)
aluminum powder (average particle size 8 μm) and evaporated silica (SIO, min. 98 wt.), specific surface area 30 m”
/f) Mix according to the formulation in Table 1 using T-T, add an appropriate amount of pulp waste liquid (approximately 3 to 5 layers) and knead further, and mix the mixed wire with an outer diameter of 150 a1, an inner diameter of 80 g, and a high Sa1
A cylindrical hot press die of 00a was molded by vibration pressure.

After drying the molded body, under normal pressure and nitrogen gas atmosphere, 1450
C. for 8 hours. After measuring the bulk specific gravity and apparent porosity of the fired body, bending strength test pieces (15X10X10
0g)'Ik was cut out, and the bending strength at room temperature and 1400°C was measured. The results are shown in Table IK.

(Left below) Regarding the components in Table 1, samples 6 and 7, which are comparative examples, have a weight ratio of aggregate phase component/binder phase component, sample 8 has a binary value, and sample 9 has a weight ratio of aggregate phase component. The maximum grain size of each silicon carbide grain is outside the range of the present invention, and the conventional sample IO is a commercially available silicon nitride bonded silicon carbide normal brick.

As is clear from Table 1, Samples 1 to 5 which are examples of the present invention
The bending strength is lower than that of the comparative and conventional samples at room temperature and 1
Both 400℃ and 1400C strength are extremely high. In addition, in the examples of the present invention, there are even examples (Samples 1, 2 and 5) whose bending strength at 1400°C exceeds that at room temperature, and in the case of samples 3 and 4, the strength at 1400°C tends to decrease very slightly compared to room temperature. The strength is still at a high level compared to comparative examples and conventional examples.

As a result of practical comparison of hot press dies similar to Sample 2 (example of the present invention) and Sample 10 (conventional example), Sample 2 exhibited a lifespan 2.0 to 2.1 times longer than Sample 10. In addition, in the same test in which the hot press pressure was 20 times higher than before due to practical requirements, Sample 2 showed three times the lifespan of Sample 10. This is considered to be one of the reasons why the high temperature and high strength of the forest material of the present invention greatly extended its life.

Example 2 Sample 2' dish-shaped bricks (230XI 14X6
5 mg K) was obtained. This brick of Sample 2' was laminated with the brick of Sample 10 at the part of the molten copper gutter where wear is the fastest, and all practical tests were carried out. After one month of operation, the brick of sample 10 showed some corrosion damage (due to corrosion and cavity erosion) near the metal line, and the brick of sample 2' showed no damage at all.

Example 3 4 parts by weight of Nosolp waste liquid and 1 part by weight of water were added and mixed to the same formulation as Sample 2 of Example 1, and plate crystals (400 x 350 x 10 M) were formed by ramming molding method under the same conditions as Example 1. Sample 2 was obtained by firing.

An oxidation test was conducted on this sample 2 and commercially available samples 11, 12, and 13 as conventional samples. Sample 11,
12 and 13 are silicon carbide plate crystals (400X350XI) with silicate bonds, silicon nitride bonds, and recrystallization, respectively.
Oa+). Oxidation test is 1000℃ and 1200℃
The test was carried out at ℃ for 500 hours each in an atmosphere of coexistence of air and water vapor. Table showing the physical property measurement results and oxidation test results for each sample.
Shown in 2.

(Left below) As is clear from Table 2, Sample 2 of the present invention has a much higher bending strength at both room temperature and 1400°C than the conventional samples, and also has an oxidation resistance of 1000°C. ℃
, 1200'C were both excellent. Compared to sample 13, sample 2 has a lower bending strength at 1400°C, but there is a decisive difference in oxidation resistance, especially at 1200°C, and it is clear that sample 13 is extremely susceptible to high-temperature oxidation. . From the above, it can be seen that the material of the present invention has excellent oxidation resistance and high-temperature strength, and is extremely suitable for use in heat treatment kiln tools, jigs, etc. that are used in high-temperature oxidizing atmospheres and under heavy loads.

Example 4 Sample 2' obtained in Example 2, Sample 1 shown in Example 1
0 (silicon nitride bond) and Conventional Example Sample 11 of Example 3, both of which were subjected to a sandblasting abrasion test on dish-shaped bricks. In both tests, each sample was randomly fixed in the radial direction of the rotary table with the fired surface of a dish-shaped brick and the cut surface of the central part of the brick (both 65 x 114 m) as the irradiation surface, and the rotary table was rotated at a constant speed. Random abrasive grains +36 were directly applied to the irradiated surface.

The results are shown in Table-3.

(The following is a blank space) As is clear from the results of Table 3, Sample 2 of the present invention example
′ has a significantly smaller wear volume than each conventional sample.
In addition, there is a gap between the wear volume of the fired surface and the cut surface in the conventional example (sample 10).
There is no such large difference as in the sample 2', which confirms the homogeneity of the structure of the brick of sample 2' of the present invention. As described above, the material of the present invention is useful as a wear-resistant lining material for transportation routes and storage tanks for natural mineral products such as coal and iron ore, and artificial mineral products such as cement clinker-1 slag.

Claims (1)

[Claims] 1. An aggregate phase of silicon carbide particles having a maximum grain size of 4 to 1 mm and having the general formula Si_6_-_zAl_zO_2N_8_
−_z (however, 0<z≦3), the weight ratio of the aggregate phase and the binder phase is 90/10 to 70/30, and the apparent porosity is 10. % or less of β′sialon bonded silicon carbide material. 2. An aggregate phase of silicon carbide particles with a particle size of up to 4-1 mm and a general formula Si_6_-_zAl_zO_z after calcination.
Metallic silicon, aluminum, and silicic acid fine powder are mixed and molded in proportions to form β' sialon represented by N_8_-_z (0<z≦3), and the molded body is dried and then heated to a temperature of 1300 to 1600. 1. A method for producing a β'-sialon bonded silicon carbide material, which comprises firing the material at 10° C. under normal pressure in a non-oxidizing atmosphere containing nitrogen to obtain an apparent porosity of 10% or less.