JPS5915113B2 - Method for manufacturing dense β′-sialon sintered body - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a dense β-iron sintered body.

Conventionally, various methods have been proposed for producing β'-sialon sintered bodies, but the obtained β'-sialon sintered bodies are not dense;
Even if it becomes dense, cracks may occur during firing, it may shrink unevenly and bend, reducing dimensional accuracy, and the structure of the sintered body may be uneven, resulting in the excellent properties unique to β'-sialon. There were disadvantages that I could not get.

The present invention was made in order to eliminate the above-mentioned drawbacks, and it is dense and has excellent dimensional stability, as well as excellent heat resistance, thermal shock resistance, oxidation resistance, abrasion resistance, acid resistance, and alkali resistance. It is an object of the present invention to provide a method for producing a dense β'-sialon sintered body that has an acid and also has low thermal expansion.

The present invention will be explained in detail below.

First, use the following method to prepare the maesiaron main component material (usually β
'-containing 70 to 80% by weight of Sialon).

(1) 70 to 40% by weight of silica powder and 30 to 60% by weight of metal aluminum powder are thoroughly mixed to obtain a starting raw material powder, and this starting raw material powder is molded by various molding methods, such as mold pressing method, rubber pressing method, After forming a green compact into an arbitrary shape with a wall thickness of 5 crfL or less, preferably 2 cm or less by slip casting or extrusion molding, this green compact is subjected to a heating reaction at 1400 to 1700°C in a nitrogen-containing non-oxidizing gas atmosphere. A β'-Sialon main component material in a solid solution state is produced using the following steps.

(2) A starting raw material powder, which is a mixture of 70 to 40% by weight of silica powder and 30 to 60% by weight of metal aluminum powder, is once pulverized to an average particle size of 3μ or less, preferably 1.5μ or less, and this fine powder raw material is In a heat-resistant container with a depth of 5 crrL or less,
Preferably, after filling to 2 CrrL or less, the fine powder raw material is heated to 1400 to 1700 CrrL in a nitrogen-containing non-oxidizing gas atmosphere.
A heating reaction is carried out at a temperature of °C to produce a β'-SiAlON main component material in a solid solution state.

(3) Metal powders such as iron powder, copper powder, cobalt powder, manganese powder, or their oxide powders are added to 100 parts by weight of a mixed powder consisting of 70 to 40% by weight of silica powder and 30 to 60% by weight of metal aluminum powder. or by adding and mixing 0.1 to 10 parts by weight of one or more additives selected from the group of fluoride powders such as calcium fluoride, aluminum fluoride, magnesium fluoride powder, manganese fluoride powder, etc. The starting raw material powder is made into a green compact according to the method (1) above, or into a fine powder raw material according to the method (2) above, and then processed into a nitrogen-containing non-oxidized powder. The material is heated at a temperature of 1,200 to 1,700° C. in a neutral atmosphere to produce a β'-sialon-based material in a solid solution state.

Chemical reaction during heating in the methods (1) to (3) above,
Although the details of the chemical change are unknown, it is thought that the following reaction basically occurs.

j) Below 1000℃, 3Si02+4A7→3S i +2A7203
...(1) 2AA10N2 → 2AAN
...(II)ji) At 1000℃ or higher, 3Si+2N2→β-8i 3N4...
(Solid solution of AA203.AAN in IIDβ-8i3N → β'-Sialon main component material * ... (IV)
*β'-sialon main component material; β'-sialon is the main component, but Al2O3 is not solidly dissolved in other materials.

The chemical formula (Si,
Al)5(0,N)6), AAN, etc.

Examples of the silica powder used in the methods (1) to (3) above include quartz powder, silica sand powder, quartz glass powder, evaporated silica, chemical precipitation silica, and vapor phase silica. In particular, evaporated silica has the best yield of β'-sialon-based material.

In this case, it is possible to use shirasu as the silica powder, but due to the high content of alkaline components, it may contaminate and deteriorate the furnace core tube, lining refractory, insulation refractory, resistance heating element, etc. during heating. It is not desirable because

The aluminum powder used in methods (1) to (3) above can be either teardrop-shaped atomized powder (sprayed powder) or scale-shaped ground powder, but the effect is the same, especially finer than 50 mesh. It is preferable to use powder.

The reason why the ratio of silica powder to aluminum powder (Si02 powder/Al powder) in methods (1) to (3) above is limited to the above range is that the ratio of 5i02 powder/All powder is 40/60 (weight ratio). If it is made smaller, unreacted A7 may remain or Si and AlN may be generated, resulting in β'-
The amount of β'-sialon produced in the sialon main component material decreases, and on the other hand, if the ratio is more than 70/30, unreacted S
This is because iO2 remains or mullite is generated, which reduces the amount of β-iron produced in the main component material, and the preferred ratio is 5i02 powder/Al! 60/40 powder
It's nearby.

The reason for limiting the thickness of the green compact in methods (1) and (3) above is that if the wall thickness exceeds 5 crrL, nitrogen gas will not penetrate sufficiently into the green compact during heating, and β ′−
This is because a β'-sialon main component material with a high sialon production rate cannot be obtained.

The reason why the filling depth of the fine powder raw material is limited in the methods (2) and (3) above is that the filling depth is 5+:'m.
This is because, if it exceeds this amount, nitrogen gas will not penetrate sufficiently into the charged raw material during heating, and a β'-sialon-based material with a high production rate of β'-sialon will not be obtained.

The containers used in this case are usually made of graphite, silicon nitride, or alumina, but when using a graphite container, the inner surface is coated with aluminum nitride powder or nitride to prevent the formation of silicon carbide. Coating with boron powder is desirable.

The reason for limiting the amount of additives added to the mixed powder consisting of silica powder and aluminum powder in the method (3) above is that if the amount of additives is less than 0.1 part by weight, the above ( The effect of promoting the reactions of formulas I) to (IV) cannot be expected, and on the other hand, if the amount exceeds 10 parts by weight,
This is because it impedes the purity of the obtained β'-sialon main component material.

Furthermore, the reason for limiting the heat treatment temperature in methods (1) and (2) above is that if the heat treatment temperature is lower than 1400°C, unreacted Si remains and the β'-SiAlON main component material is When the production rate of sialon decreases and the temperature exceeds 1700°C, Y-Phase sialon increases and β'-sialon in the main component material
This is because the production rate of ′-Sialon decreases.

In addition, in method (3) above, the heat treatment temperature is 200°C lower than the temperature in methods (1) and (2) above.
This is possible even at temperatures as low as 00°C.

A desirable heat treatment method is a heating rate of 1400 to 1
It is heated to a temperature of 500° C. or 1200 to 150° C. and held at that temperature for 5 hours or more (this is referred to as the first stage heat treatment).

This achieves the purpose of the heat treatment, but in order to further improve the production rate of β'-Sialon, the temperature must be raised to a predetermined temperature between 1500 and 1700°C in the first stage heat treatment.
Heat treatment for more than an hour (this is called second stage heat treatment)
.

However, in the method (1) above, the starting raw material powder having the above-mentioned composition ratio is molded into a green compact, and the thickness of the green compact is specified, so that the silica powder and the aluminum powder are combined. In order to improve the contact situation and improve the degree of contact of nitrogen gas with each powder, the above-mentioned (1) to
The reaction of the formula is promoted, and the high content of β
'-SiAlON main component material is obtained.

In addition, in the method (2) above, the starting raw material powder having the above-mentioned composition ratio is pulverized into a finely powdered raw material, and the filling depth of the raw material into the container is specified, so that the pulverization and mixing are performed. The aluminum powder with excellent malleability coats the silica powder to form an aluminum film, which improves the contact between aluminum and silica and improves the degree of contact of nitrogen gas with each raw material. 1)～(
The reaction IV) is promoted, and a β'-sialon-based material with a high β'-sialon content can be obtained.

Furthermore, in the method (3) above, in addition to molding or pulverizing the starting raw material powder, additives such as iron and magnesium are mixed into the raw material powder.
The reaction is further accelerated than method 2), and the β
A β'-Sialon main component material with a high content of '-Sialon can be obtained.

Note that the starting materials used in the manufacturing methods (1) to (3) above are not limited to those consisting of silica powder and aluminum powder, but may also include, for example, silica, metallic silicon, metallic aluminum, alumina, silicon nitride, aluminum nitride, etc. Appropriate combinations may be used that are blended into a composition that becomes a β'-sialon main component material by nitriding treatment, or in some cases, the starting materials can be used as they are with the β'-sialon main component material.
May be used.

Next, the β'-sialon main component material obtained by the method described above is finely pulverized until the average particle size (measured with a Fisher subsieve sizer) is 1.6 μ or less, preferably 1.2 μ or less, to obtain β' - Sialon main ingredient material powder.

Wet and dry pulverization methods are used for pulverization, but in particular, tungsten carbide,
Alternatively, a wet grinding method using an alumina ball mill is effective because it can grind in a short time.

Subsequently, the above β'-sialon main component material powder was molded using various molding methods, such as mold pressing, rubber pressing, slip casting, and extrusion molding to a density of 1.7 g/
After molding into a desired shape so that the temperature is d or more, this molded body is primarily fired at a temperature of 1600 to 2000°C in a nitrogen-containing non-oxidizing gas atmosphere (approximately the same pressure as the atmosphere), and further in the same atmosphere. 30°C or more lower than the second firing temperature, and 1
Secondary firing is performed at a temperature range of 500 to 1750°C for 1 hour or more, preferably 4 hours or more to obtain a dense β'-sialon sintered body.

The reason why the particle size of the β'-sialon main component material powder is limited in the present invention is that if the particle size of the main component material powder exceeds 1.6μ, a dense β'-sialon sintered body with low porosity will form. Because you can't get it.

The reason why the density of the molded body is limited in the present invention is that if the density is set to 1.7 g/cvi, a dense I-Sialon sintered body with low porosity cannot be obtained.

The nitrogen-containing non-oxidizing gas atmosphere used in the present invention is an atmosphere of nitrogen gas alone or a mixed gas of nitrogen gas and an inert gas such as argon gas or neon gas.

In this case, whether to use an atmosphere of nitrogen gas alone or a mixed gas atmosphere (rubbing) may be selected as appropriate depending on the content of β'-sialon in the compact, firing temperature, etc.

The reason why the primary firing temperature in the present invention is limited to the above range is that if the firing temperature is set to a low temperature below 1600°C, the sintering speed of the compact becomes slow, and it takes a long time to obtain the β-nit sialon sintered body. On the other hand, when the temperature is raised to a high temperature exceeding 2000°C, a part of β'-sialon is converted into Y-phase sasialon, and a dense β'-sialon sintered body with a high content of β-sialon is obtained. That's because there isn't.

The holding time under such primary firing temperature is usually 0.5~
It is desirable to make it 5 hours.

The reason for this is that if the holding time is less than 0.5 hours, the molded body cannot be sintered sufficiently, while if the holding time exceeds 5 hours, the grain growth of the sintered body will progress too much, resulting in - This is because the characteristics (especially strength) of the Sialon sintered body deteriorates.The reason why the secondary firing temperature in the present invention is limited to the above range is that the secondary firing temperature is the same as the primary firing temperature (1600 to 20
If the temperature is lower than 30°C (00°C), grain growth in the sintered body will progress too much and rapid solid diffusion will occur, making it impossible to uniformly crystallize the grain boundaries, resulting in a dense and dimensionally stable product. This is because an excellent β'-sialon sintered body cannot be obtained.

Moreover. If the secondary firing temperature is as low as 1,500°C, solid diffusion will not be sufficient and crystallization of grain boundaries will be insufficient.On the other hand, if the secondary firing temperature is higher than 1,750°C, grain growth will be impaired. This is because if it progresses too much, rapid solid diffusion occurs and uniform crystallization of grain boundaries is inhibited.

In addition, the reason for limiting the holding time under the secondary firing temperature is as follows.
This is because if the holding time is short, less than 1 hour, solid diffusion will not be sufficient, crystallization of grain boundaries will be insufficient, and a β'-sialon sintered body with excellent properties will not be obtained.

The firing furnace used for the primary and secondary firing is usually a graphite resistance heater or a high-frequency induction heating furnace with a graphite lining. Since CO gas is generated, the surface of the obtained Maesiaron sintered body is likely to be carbonized and a silicon carbide film is likely to be formed.

Furthermore, during firing, it is difficult to uniformly sinter the molded body at the same temperature, which may result in cracks or deformation in the sintered body.

However, to solve this problem, boron nitride powder (
The above-mentioned compact is buried in a graphite container filled with powder made of aluminum nitride powder (A#N), and the graphite container is placed in a furnace to uniformly sinter the surface of the sintered compact. It is desirable to prevent the formation of a silicon carbide film.

Next, the second invention of the present application will be explained.

First, as in the first invention of the present application, β'-Sialon main component material is finely pulverized until the average particle size (measured with a Fisher subsieve sizer) is 1.6μ or less, preferably 1.2μ or less. '~ Sialon is the main ingredient material powder.

Subsequently, 0.5 to 40% by weight of at least one of silicon nitride powder and aluminum nitride powder is added to the β'-sialon main component material powder and mixed to obtain a β'-sialon mixed material powder. This is then molded using various molding methods to a density of 1.
After molding into a desired shape so as to have a fi/d of 7 fi/d or more, this molded body is first fired and second fired in a nitrogen-containing non-oxidizing gas atmosphere as in the first invention to obtain a dense β-iron iron sinter. Obtain a body.

As mentioned above, β′- is a mixture of silicon nitride powder and/or aluminum nitride powder with β-iron main component material powder.
By using Sialon mixed raw material powder, the sinterability of the molded body during firing is promoted and the grain boundary bonding phase is improved by interaction with primary firing and secondary firing.

β'-Sialon (Si6-2A1.Z, 0ZN8-
2; Since it can be modified to a crystalline phase with a high content of O < Z 5), it has excellent compactness and dimensional stability, and is particularly alkali resistant, thermal shock resistant, abrasion resistant, low thermal expansion, and chemically resistant. A β'-sialon sintered body with improved properties and mechanical strength can be obtained.

In particular, β using a combination of silicon nitride powder and aluminum nitride powder
By using ′-Sialon mixed material powder, the grain boundaries can be modified to a crystalline phase that is almost similar to β′-Sialon, resulting in outstanding alkali resistance, thermal shock resistance, abrasion resistance, and low thermal expansion. It is possible to obtain a high-quality dense β'-sialon sintered body that has excellent chemical stability, mechanical strength, and corrosion resistance, and is composed of a single phase of β'-sialon.

It is desirable that the particle size of the silicon nitride powder and aluminum nitride powder used in the second invention of the present application is usually 1 to 5 μm.

In addition, the reason why the blending ratio of silicon nitride powder and/or aluminum nitride powder in the β-iron mixed material powder was limited to the above range is that if the amount is less than 0.5% by weight, sinterability will be promoted. On the other hand, if the amount of the grain boundary binding phase exceeds 40% by weight, the constituent phases of the obtained β-iron sintered body may contain silicon nitride or Y-phase sasialon. This is because not only does this lead to a decrease in physical properties, but also an increase in cost.

In addition, the above-mentioned β'-SiAlON main component material powder (fine powder) with a particle size of 1.6μ or less and the first. The dense β'-SiAlON sintered body obtained in the second invention is re-pulverized and sieved, and medium grains and coarse grains are mixed in an appropriate mixing ratio, and this is molded according to a conventional method. A dense β'-sialon sintered body may be produced by firing the body at a temperature of 1,600 to 2,000° C. in a nitrogen-containing non-oxidizing gas atmosphere.

According to this method, the shrinkage of the molded body during firing is slight, so there is no deformation or cracking of the obtained sintered body, making it possible to manufacture large-sized objects, and further improving dimensional stability. In addition to improving the thermal shock resistance, a dense β'-sialon sintered body with particularly excellent thermal shock resistance can be obtained.

Therefore, the present invention involves forming fine β'-SiAlON main component material powder with a defined average particle size to a predetermined density, and performing primary firing at a predetermined temperature range in a nitrogen-containing non-oxidizing gas atmosphere. By performing the secondary firing, it is possible to convert a part of the substances other than β'-siaon in the molded body into β'-siaron during the secondary firing, and at the same time, the main component material in the molded body is refined. Since it is possible to easily sinter the powder together and prevent cracks and deformation from occurring, it is possible to obtain a dense β'-sialon sintered body with an extremely high content of β'-sialon and excellent dimensional stability. be able to.

In addition, during the secondary firing process, grain growth of the fine powder mainly composed of β'-sialon is suppressed, and it is appropriately dispersed into the solid to form a dense crystalline phase, and β'-sialon is added to the grain boundary phase. By diffusing a large amount, a crystalline ratio phase is formed, and the grain boundary phase is significantly modified, whereby the constituent phases are almost β'-
Dense β'-Sialon sintered body with excellent chemical stability (especially alkali resistance), heat resistance, thermal shock resistance, low thermal expansion, mechanical strength, and abrasion resistance because it is a single phase of Sialon. can be obtained.

Therefore, the dense Maesiaron sintered body obtained by the method of the present invention has excellent dimensional stability and various other properties, so that it can be applied to a wide variety of fields as shown below.

■ Refractory melting furnace lining materials for molten nonferrous metals, pipes for transporting molten nonferrous metals, thermocouple protection tubes for temperature measurement of molten nonferrous metals, stalks for low pressure casting, nozzles for continuous casting, insert nozzles for tap holes, flow rate of molten nonferrous metals Regulating valves, sliding parts of pumps for molten nonferrous metals (pistons and cylinders of real chambers), crucibles for melting semiconductors such as goosenecks, germanium, and silicon ■ Various nozzles for continuous casting of refractories for molten steel, flats for sliding nozzles, and immersion pipes ■ Mechanical parts heat exchangers, piston heads in piston engines,
and cylinders, combustion chamber structural materials for gas turbine engines (rotors, stators, shrouds, etc.), rocket nozzles ■ Corrosion-resistant materials, acid- and alkali-resistant containers, chlorine and hydrogen sulfide gas transport pipes, chlorine gas blowing pipes, firing furnaces for plastics, etc. lining material.

The present invention will be explained in detail below.

Examples 1 to 2 and Comparative Examples 1 to 2 60% by weight of evaporated silica powder and 40% by weight of aluminum atomized powder (250 mesh or less) were dry mixed in a mixer, and the starting material powder was mixed in a rubber press (1 ton/
ff1) to form a tubular powder compact with a wall thickness of 5 mm, and then heat the compact in a nitrogen atmosphere at a heating rate of 200°C/H.
Under (7) conditions, T1 was raised to 500°C and heat treated by holding at that temperature for 10 hours to produce a β'-sialon main component material.

When this β'-Sialon main component material was examined by X-ray powder diffraction, it was found that a large peak of β'-sialon and α-A
1203 and Y-phase sialon small peaks were confirmed, and it was found that the sample consisted of almost β-sialon.

Next, the above β'-Sialon main component material was preliminarily crushed with a show crusher, and then finely crushed with a hammer crusher, and then this fine powder was crushed for 70 hours using a wet crushing method using an alumina ball mill mixed in alcohol. death,
In addition, the average particle size was 1.0% by pulverizing for 24 hours using the isothermal pulverization method.
A β'-Sialon main component material powder (Example 1 and Comparative Example 2) having a particle diameter of 2 μm and a β′-Sialon main component material powder (Example 2) having an average particle size of 1.6 μm were prepared.

In addition, as Comparative Example 1, the above fine powder was pulverized for 24 hours using the dry pulverization method using an alumina ball mill to obtain an average particle size of 1.8.
A material powder with the main component of μ β′-sialon was prepared.

Then, 20% by weight of vinyl acetate was added and kneaded to each of the above three kinds of β-iron main component powders, passed through a 50-mesh nylon sieve to granulate, dried once, and then molded into 550 kg. /d pressure condition 3
Seed plate-shaped molded body (dimensions 40w x 70L x 9TrILm)
was created.

The cholera molded bodies were heat-treated in the atmosphere at 400° C. for 12 hours to volatilize and remove the binder (vinyl acetate), and the density of each molded body after removal was examined.

As a result, the molded product used in Example I weighed 1.92 g/
crtt, the molded product of Example 2 was 1.959/criL1
The molded article of Comparative Example I had a weight of 1.94 g/crri.

Subsequently, the molded bodies of Examples 1 and 2 and Comparative Example 1 were each embedded in boron nitride packed powder in graphite containers, and the containers were placed in a firing furnace with a nitrogen atmosphere under conditions of a temperature increase rate of 400°C/Hr. After raising the temperature to 1700℃ under the same atmosphere and holding it at that temperature for 4 hours for primary firing, it was further heated to 1650℃ under the same atmosphere.
The mixture was held at a temperature of 15 hours for secondary firing to obtain three types of β-iron sintered bodies.

The compact of Comparative Example 2 was embedded in boron nitride packed powder in a graphite container and placed in a firing furnace in a nitrogen atmosphere at a heating rate of 400.
The temperature was raised to 1700°C under the conditions of °C/Hr, and the temperature was maintained for 4 hours to obtain a β-iron sintered body.

When the obtained β-SiAlON sintered bodies were identified by X-ray powder diffraction method, it was found that the β'-sialon sintered bodies of Examples 1 and 2 and Comparative Example 2 contained a trace amount of α-A120 in β-SiAlON.
In contrast, the sintered body of Comparative Example 1 contained a small amount of α-A1203 in β-iron.

In addition, when the porosity of each β-iron sintered body was investigated, the porosity of the sintered body of Example 1 was 2%, the sintered body of Comparative Example 2 was 4%,
The sintered body of Example 2 had a very dense porosity of 6%, whereas the sintered body of Comparative Example 1 had a high porosity of 13%.

From these facts, it can be seen that the average particle size of the β'-sialon main component material powder is an important factor in obtaining a dense β-sialon sintered body.

Further, the following tests were conducted using the Maesiaron sintered bodies of Example 1 and Comparative Example 2.

A): Immersed in molten aluminum at 1000°C for 5 days.

B): Immersed in 1300°C molten steel for 3 hours.

C): Boiling immersion in concentrated sulfuric acid and concentrated hydrochloric acid for 5 hours.

D): Heated in the atmosphere at 1200°C for 40 hours.

E); Boiled in 50% NaOH aqueous solution for 5 hours.

As a result, no corrosion was observed in both the β'~sialon sintered bodies of Example 1 and Comparative Example 2 in the above ^~(0 test).

However, in test (D), the sintered body of Example 1 had a very small oxidation weight gain of 3.5 rr19/crlt, whereas the sintered body of Comparative Example 2 had a weight gain of 4.5 η/cr! It was very expensive.

Furthermore, in the test (weight loss due to odor), the sintered body of Example 1 was 9.
It is extremely low at 2% and has excellent alkali resistance.
The sintered body of Comparative Example 2 had a content of 10.8%.

For these reasons, the sintered body of Comparative Example 2, which underwent only primary firing, and the sintered body of the present invention, which underwent secondary firing (Example 1)
), it can be seen that the sintered body of the present invention has excellent properties in terms of density (compactness) and chemical reactivity resistance.

Example 3 and Comparative Examples 3 to 4 β'-SiAlON main component material powder used in Example 1 above (
After kneading vinyl acetate (average particle size 1.2μ) and passing it through a 50-mesh nylon sieve to granulate it, once it was dried, it was molded into a 600-mesh powder (Example 3).
10kg/ff1 (comparative example 3) 55 kg/cyrr
Three types of plate-shaped molded bodies (dimensions: 40 W x 7 OL x 9 Tr/Lm) were produced by molding under the conditions of (Comparative Example 4).

These molded bodies were heat-treated in the atmosphere at 400°C for 12 hours to volatilize and remove the binder (vinyl acetate), and the density of each molded body after removal was examined. The molded body used in Example 3 was 1.92 g. /=The molded body of Comparative Example 3 is 1.6897ar
t, and the molded product of Comparative Example 4 was 1.53. It was p/7.

Subsequently, these molded bodies were subjected to primary firing and secondary firing in the same manner as in Example 1 to obtain three types of β'-sialon sintered bodies.

The porosity of each of the obtained β-iron sintered bodies was examined.

As a result, the sintered body of the present invention (Example 3) was extremely dense with 2%, while the sintered body of Comparative Example 3 had 10% pores, and the sintered body of Comparative Example 4 had 19%. The ratio was high.

From these facts, it can be seen that the density of the compact is also an important factor in obtaining a dense β-iron sintered body.

In addition, the corrosion resistance, acid resistance, oxidation resistance, and alkali resistance of the β'-sialon sintered body of Example 3 were tested according to the test method of ^~(E) above, and it was found that Example 1
It was recognized that it had similar excellent properties.

Example 4 Starting material powder, which is a mixture of 60% by weight of evaporated silica powder and 40% by weight of atomized aluminum powder (250 mesh), was ground for 48 hours by a wet grinding method using an alumina ball mill mixed in alcohol to obtain an average particle size. A fine powder raw material with a diameter of 1.3 μm was placed in a silicon nitride container at a depth of approximately 1.5 μm.
crr1. After filling up to.

The fine powder raw material was heated at a temperature of 1500°C in a nitrogen atmosphere for 1
The mixture was held for 0 hours and heat treated to produce a β'-SiAlON main component material.

When this β'-sialon main component material was examined by X-ray powder diffraction, it was found that β'-sialon contained a small amount of α-A1203.
It was found that the Y-phase sashyalon contained trace amounts of AIN.

Next, the above-mentioned β'-sialon main component material was preliminarily crushed with a show crusher, and further finely crushed with a hammer crusher, and then this fine powder was subjected to a wet crushing method in which a tungsten carbide ball mill was mixed in alcohol.
By time-pulverizing, a β'-SiAlON main component material powder having an average particle size of 0.7 μm was prepared.

Thereafter, vinyl acetate was added to this β'-Sialon main component material powder as in Example 1, kneaded, granulated, and mold pressed (
550 kg/i)t, and the binder in the molded body was removed by volatilization to produce a molded body having a density of 1.86.9/d.

Next, this molded body was buried in boron nitride packed powder in a graphite container, and the container was placed in a firing furnace with a nitrogen atmosphere, and the temperature was raised to 1700°C at a temperature increase rate of 180'C/Hr. After primary firing by holding at a temperature of 3 hours, secondary firing was performed by holding at a temperature of 1550° C. for 15 hours in the same atmosphere to obtain a β'-sialon sintered body.

When the obtained β-A1203 sintered body was identified by X-ray powder diffraction method, it was found that the β-A1203 contained a trace amount of α-A1203.

Further, the β'-sialon sintered body was extremely dense with a porosity of 2%.

Furthermore, the corrosion resistance of this β′-SiAlON sintered body,
When the oxidation resistance and alkali resistance were tested according to the test methods w to (E) above, it was found that the material had excellent properties similar to those of Example 1.

Example 5 β'-Sialon main component material powder used in Example 1 above (
300 mesh silicon nitride powder is added to the average particle size of 1.2μ).
0% by weight is added and mixed to make β-iron mixed material powder,
This was molded in the same manner as in Example 1, and the density of the molded product was 1.929/
cyit), primary firing, and secondary firing to obtain a β'~Sialon sintered body.

When the obtained β'-sialon sintered body was identified by X-ray powder diffraction method, it was confirmed that it consisted almost exclusively of β′-sialon.

Further, this β'-sialon sintered body was extremely dense with a porosity of 1%.

Further, the corrosion resistance, oxidation resistance, and alkali resistance of this β-iron sintered body were investigated according to the test method of Di.

As a result, the β-iron sintered body of the present invention contains molten metal,
It was found that it was not corroded by acids, had little weight loss due to oxidation, and had extremely excellent alkali resistance, with a weight loss of 25% when treated with a 50% NaOH aqueous solution.

Example 6 The β'-sialon main component material powder used in Example 1 above (
325 mesh silicon nitride powder (average particle size 1.2μ) 10
% by weight and 3% by weight of 250 mesh aluminum nitride powder are added and mixed to obtain β'-sialon mixed material powder,
This was molded in the same manner as in Example 1, and the density of the molded product was 1.91.9.
/i), primary firing and secondary firing were performed to obtain a Maesiaron sintered body.

When the obtained β-sialon sintered body was identified by X-ray powder diffraction method, it was confirmed that it consisted of a single phase of β'-sialon.

It was also found that this β'-sialon sintered body had a porosity of 1% and was extremely dense.

Furthermore, the corrosion resistance of this β-SiAlON sintered body,
Acid resistance, oxidation resistance and alkali resistance
The test was conducted according to the test method.

As a result, the β'-Sialon sintered body of the present invention is not corroded by molten metal or acid at all, and its weight loss due to oxidation is extremely small. Furthermore, the weight loss due to 50% NaOH aqueous solution is only 1.3%, and it is extremely resistant to alkali. Recognized as excellent.

As detailed above, according to the present invention, there is no cracking during firing, the porosity is extremely low, the dimensional stability is excellent, and the heat resistance, thermal shock resistance, oxidation resistance, acid resistance, and alkali resistance are excellent. We can provide a dense β'-SiAlON sintered body that has excellent wear resistance and low thermal expansion and can be effectively used in a wide range of fields such as refractories for molten nonferrous metals, large-sized materials for steel, mechanical parts, and corrosion-resistant materials. It is something.

Further, according to the second invention of the present application, it is possible to provide a dense β'-sialon sintered body which has excellent alkali resistance among the above-mentioned properties and also has excellent mechanical strength.

Claims (1)

[Scope of Claims] 1 β'-Sialon main component material is ground to an average particle size of 1.6μ or less to obtain β'-Sialon main component material powder, and the main component material powder is made to have a density of 1.797 cd or more. After molding into a molded body, the molded body is primarily fired at a temperature of 1600 to 2000 ° C. in a nitrogen-containing non-oxidizing gas atmosphere,
A method for producing a dense β-iron sintered body, which further comprises performing secondary firing in the same atmosphere at a temperature of 1,500 to 1,750°C, which is 30°C or more lower than the secondary firing temperature, for 1 hour or more. 2. Beta Nisu Iron main component material is ground to an average particle size of 1.6μ or less to obtain β Nisu Iron main component material powder, and 0.5% of one or more of silicon nitride powder and aluminum nitride powder is added to the main component material powder. ~40% by weight is mixed to obtain β'-Sialon mixed material powder, which is molded to a density of 1.7 g/cd or more to form a molded body, and then the molded body is heated with a nitrogen-containing non-oxidizing gas. Primary firing is performed at a temperature of 1,600 to 2,000°C in an atmosphere, and then 3 times higher than the temperature of the second firing in the same atmosphere.
A method for producing a dense β'-sialon sintered body, which comprises performing secondary firing at a temperature of 1500 to 1750°C, which is lower than 0°C.