JPS5934149B2 - 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'-sialon sintered body.

Conventionally, various methods have been proposed for producing β'-sialon (β'-8ialon) sintered bodies, but the obtained β'-sialon sintered bodies do not have a dense quality;
Even if it were dense, it would bend or shrink during firing, resulting in poor dimensional stability, and it would have to be fired at a high temperature, which would increase manufacturing costs.

The present invention was made in order to eliminate the above-mentioned drawbacks.
- The purpose is to obtain a sialon sintered body.

The present invention will be explained in detail below.

First, a β'-sialon main component material (usually containing 70 to 80% by weight of β'-sialon) is prepared by the following method.

(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, Wall thickness 50r/L or less, preferably 2cIr by slip casting method or extrusion molding method
After forming a green compact into an arbitrary shape of L or less, the green compact is reacted by heating at 1400 to 1700°C in a nitrogen-containing non-oxidizing gas atmosphere to produce a β'-SiAlON main component material in a solid solution state. .

(2) The starting raw material powder, which is a mixture of 70 to 40% by weight of silica powder and 30 to 61% by weight of metal aluminum powder, is once pulverized to an average particle size of 3μ or less, preferably 1°5μ or less, and the fine powder raw material is heat-resistant. After filling a sex container to a depth of 5 crfL or less, preferably 2 crIL or less, the vaginal fine powder raw material is subjected to a heating reaction at a temperature of 1400 to 1700°C in a nitrogen-containing non-oxidizing gas atmosphere to form β'- in a solid solution state. Create sialon-generating materials.

(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 one or two selected from the group of fluoride powders such as calcium fluoride, aluminum fluoride, magnesium fluoride powder, manganese fluoride powder, etc.
A starting material powder is prepared by adding and mixing 0.1 to 10 parts by weight of at least one additive, and this starting material powder is made into a green compact according to the method described in (1) above, or by the method described in (2) above. The raw material is made into a fine powder according to the method, and then heated at a temperature of 1200 to 1700° C. in a nitrogen-containing non-oxidizing atmosphere to produce a β'-sialon main component 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.

1) Below 1000℃, 3Si02 + 4A11→3Si+2A1203
...(I)2Al+N2→2AJl? N
・・・・・・(If) ii) At 1000℃ or higher, 3Si+2N2→β-5i3N4 ・・・・・・(
III) Solid solution of Al2O8, AAN in β-8i3 N4 → β'-Sialon main component material * ・・・・・・G
V) *β'-sialon main component material; β'-sialon is the main component, but there is also undissolved Al2O3゜Y-phase Sasialon A [Si and 0 are included in the N structure, metal: nonmetal Chemical formula with an atomic ratio of 526 (Si, Al)
s(0-N)a), AlN, 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 (volatiled-8ilica), chemically precipitated 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 (Sin2 powder/Al powder) in methods (1) to (3) above is limited to the above range is that the ratio of S t 02 powder/All powder is 40/60 (by weight If the ratio is made smaller, unreacted Al may remain or Si and AlN may be generated, resulting in β
The amount of β'-sialon produced in the main component material of '-sialon decreases, and on the other hand, if the ratio is more than 70/30, unreacted S t 02 may remain or mullite will be produced, causing the main component to be reduced. This is because the amount of β'-sialon produced in the material decreases, and the preferable ratio is SiO2 powder/Al powder of 6.
It is around 0/40.

The reason for limiting the thickness of the green compact in methods (1) and (33) above is that if the wall thickness exceeds 5 CIrL, 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 (1) and (3) above is that the filling depth is 5 crfL.
This is because, if it exceeds this amount, nitrogen gas will not sufficiently infiltrate into the filling material during heating, and a β'-sialon-based material with a high β'-sialon content 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 ( 1) It cannot be expected to have the effect of accelerating the three-cycle reaction, and on the other hand, if the amount exceeds 10 parts by weight, the purity of the obtained β'-sialon main component material will be impaired.

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 increases.
This is because the production rate of ′-Sialon decreases.

In addition, in the method (3) above, the heat treatment purity is 12
This is possible even at temperatures as low as 00°C.

A desirable heat treatment method is a heating rate of 1400 to 15
The sample is heated to a temperature of 00°C or 1200 to 1500°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, it is necessary to further increase the temperature between 1500 and 1700°C after the first stage heat treatment.

The temperature is raised to a constant temperature and heat treatment is performed for 3 hours or more (this is referred to as the second stage heat treatment).

However, even in the method (1), silica can be produced by molding the starting raw material powder having the above-mentioned composition ratio to form a green compact, and by defining the thickness of the green compact.

This improves the contact between the powder and aluminum powder, and also improves the degree of contact of nitrogen gas with each powder.
The reactions of formulas (I) to (IV) described above are promoted, and β'-
A β'-sialon-based material with a high sialon content can be 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. Did (1) ~
The reaction of (β'v) 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'-1"sialon-based material having a high content of '-sialon is 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 nitrogen, aluminum nitride, etc. They may be appropriately combined and nitrided to form a composition as a β'-sialon main component material, or in some cases, waste raw materials may be used as they are as a β'-sialon main component material.

Next, β′ obtained by the above-mentioned methods (1) to (3)
−The average particle size (Fisher
The powder is pulverized until the particle diameter (measured with a subsieve sizer) is 1.6 μ or less, preferably 1.2 μ or less, to obtain a β'-sialon main component material powder.

As the pulverization method, a wet pulverization method and a dry pulverization method are employed, and a wet pulverization method in which a ball miller made of tungsten carbide or alumina is placed in alcohol is particularly effective because it can pulverize in a short time.

Next, 0.2 to 20% by weight of silica powder and 0.2 to 20% by weight of one or more metal oxides forming silicate glass are added to the β'sialon main component material powder and mixed. β'-Sialon mixed raw material powder is made into a powder with a density of 1.5 mm by various molding methods such as die pressing, rubber pressing, slip casting, and extrusion molding. 'H!
/cIf1 or more, the molded body is fired at a temperature of 1200 to 1800°C in a nitrogen-containing non-oxidizing gas atmosphere (approximately the same pressure as the atmosphere) to form a dense β' - Obtain a Sialon sintered body.

In the present invention, the reason why the particle size of the main component material powder of β'-sialon is limited is that a dense βl-sialon sintered body having a particle size of more than 1.6μ and a low porosity due to air removal can be obtained. This is because it cannot be done.

The silica powder used in the present invention includes quartz crystal powder, silica sand powder, quartz glass powder, and evaporated silica (Vola
tiled-5 ilica), chemical precipitation silica, vapor phase silica, and the like.

The reason why the blending amount of one or more metal oxides forming the silica powder and silicate glass in the β'-Sialon mixed material powder in the present invention is limited to the above range is that the blending amount is 0.2% by weight. If the amount is less than 20% by weight, the effect of low-temperature sinterability cannot be fully exhibited, while if the amount is more than 20% by weight, a large amount of silica glass will be included in the constituent phase of the obtained sintered body, resulting in a decrease in physical properties. Because it does.

The metal oxides used here include MgO* MnOt
L i20. Ti 02゜B2O3+ Fe2O3
, Cu2O, and CaO.

The reason why the density of the molded body is limited in the present invention is that if the density is less than 1.7 g/cri1, a dense β'-sialon sintered body with low porosity cannot be obtained.

The nitrogen-containing non-oxidizing gas atmosphere in the present invention includes 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 a nitrogen gas atmosphere alone or a mixed gas atmosphere may be appropriately selected depending on the content of βl-sialon in the compact, firing temperature, etc.

The reason why the firing temperature is limited to the above range in the present invention is as follows.
If the firing temperature is lower than 1200°C, the sintering rate of the compact will be slow and it will take a long time to obtain a dense β'-sialon sintered body; This is because a part of the β'-sialon in the compact is converted into other substances, making it impossible to obtain a dense β'-sialon sintered body with a high β'-sialon content.

The firing furnace used during the sintering of the present invention is usually a graphite-lined furnace equipped with a graphite resistance heater and a high-frequency induction heating type graphite susceptor. Since CO gas is generated, the surface of the obtained β'-sialon 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, in order to solve this problem, the above-mentioned molded body is buried in a graphite container filled with powder made of boron silicide powder (BN) and aluminum nitride powder (A7N), and the graphite container is placed inside the furnace. It is desirable that the sintered body be placed in a sintered body to uniformly perform the firing and to prevent the formation of a silicon carbide film on the surface of the sintered body.

In addition, the above-mentioned β'-sialon main component material powder (fine powder) with a particle size of 1.6 μ or less and the medium grains obtained by re-pulverizing and sieving the dense β'-sialon sintered body obtained by the above-mentioned method. Coarse particles are mixed with coarse grains in an appropriate proportion and molded according to a conventional method. The molded body is fired at a temperature of 1,600 to 2,000°C in a nitrogen-containing, non-oxidizing atmosphere to form a dense β '-SiAlON sintered bodies may be manufactured.

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 provides β'-sialon, which is prepared by blending a predetermined amount of silica powder and one or more metal oxides forming silicate glass into fine β'-sialon main component material powder having a defined average particle size. Form the mixed material powder to a predetermined density,
By firing this in a nitrogen-containing non-oxidizing gas atmosphere at a predetermined temperature range, some of the substances other than β'-sialon in the βl-sialon main component material powder of the molded body are removed by β
In addition to being able to convert into '-sialon, a nitrogen-containing glass phase is formed in the grain boundary phase in which the fine powder mainly composed of β'-sialon and silica glass are combined, and the fine powder can be reduced extremely easily. Since it can be sintered at high temperature, a dense β'-sialon sintered body with excellent dimensional stability without cracking or deformation can be obtained at low cost.

Therefore, the dense β'-sialon sintered body obtained by the method of the present invention not only has excellent dimensional stability but also
Due to the characteristics of Sialon itself, 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 non-ferrous metals (hot chamber pistons, cylinders), crucibles for melting semiconductors such as Kuznets, germanium or silicon ■ Various nozzles for continuous casting of refractories for molten steel, plates for sliding nozzles, 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. The present invention will be described in detail below.

Examples 1-2 A starting material powder obtained by dry mixing 60% by weight of evaporated silica powder and 40% by weight of atomized aluminum powder (250 mesh or less) in a V-mixer was mixed in a rubber press (Lton/
cr/l) to form a tube-shaped powder compact with a wall thickness of 5 crIL, and then heat the compact in a nitrogen atmosphere at a heating rate of 200°.
The temperature was raised to 1500° C. under C/Hr conditions, and the temperature was maintained for 10 hours for heat treatment to produce a β'-sialon main component material.

When this βl-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 a small peak of Y-phase sialon were confirmed, and it was found that it consisted mostly of β'-sialon.

Next, the above β'-SiAlON main component material was preliminarily crushed using a show crusher, and then finely ground using 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. Also, the average particle size was 1.2 by pulverizing for 24 hours using the isothermal pulverizing method.
β'-Sialon main component material powder having a particle diameter of 1.6 μm (Example 1) and β′-Sialon main component material powder (Example 2) having an average particle size of 1.6 μm were prepared.

As a comparative example, 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 1.8μ.
A material powder with β'-SiAlON as its main component was prepared.

2% by weight of evaporated silica and 2% by weight of soda carbonate are added and mixed into the brigged β'-Sialon main component material powder, and β'
- Add 20% by weight of vinyl acetate to each of these mixed material powders, knead them, pass through a 50-mesh nylon sieve, granulate them, dry once, and then use a mold press to produce 550ky/C11t. Three types of plate-shaped molded products (dimensions 40WX70LX9T') were molded under the pressure conditions of
I created ji.

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.

As a result, the molded body used in Example 1 was 1.919/cr
IL, the molded body of Example 2 is 1.9397 cm, Comparative Example 1
The weight of the molded product was 1.92 g/cm.

Next, each of these molded bodies was buried in boron nitride packed powder in a graphite container, and the containers were placed in a firing furnace with a nitrogen atmosphere and heated to 1600°C at a temperature increase rate of 400°C. Three types of β'-sialon sintered bodies were obtained by holding and firing for 2 hours.

When the obtained β'-sialon sintered bodies were identified by X-ray powder diffraction, all of the sintered bodies contained βl-sialon and a small amount of α-A1203 and Y-phase sasialon.

Furthermore, when examining the porosity of each β'-Sialon sintered body, the porosity of the sintered body of Example 1 was 1%, and the porosity of the sintered body of Example 2 was 2%.
In contrast, the sintered body of Comparative Example 1 has a density of 9.
%, which had a high porosity.

These facts show that the average particle size of the β'-sialon main component material powder in the β'-sialon mixed material powder is an important factor in obtaining a dense βl-sialon sintered body.

Example 3 β'-sialon mixed material powder used in Example 1 (contains β'-sialon main component material powder with an average particle size of 1.2μ)
After mixing with vinyl acetate and passing through a 50-mesh nylon sieve to granulate it, once it was dried, it was molded into 600 kg/C111 (Example 3), 110
kg/cril (Comparative Example 2), 55ky/ffl
(Comparative Example 3) Three types of plate-shaped molded products (
It was built with dimensions 40W x 70L x 9T.

These molded bodies were heat-treated in the atmosphere for 12 hours to volatilize and remove the binder (vinyl acetate), and the density of each molded body after removal was examined. The density of the molded body used in Example 3 was 1.9.
i g7crit, the molded product of Comparative Example 2 is 1.66.9
The weight cm of the molded article of Comparative Example 3 was 1.50 g/d.

Subsequently, these molded bodies were fired in the same manner as in Example 1 to obtain three types of β' to Sialon sintered bodies.

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

As a result, the sintered body of the present invention (Example 3) has an extremely high density of 1%, while the sintered body of Comparative Example 2 has a density of 9%, and the sintered body of Comparative Example 3 has a density of 1%. The porosity was high at 15% and the density was poor.

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

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 in alcohol. A fine powder raw material with a particle size of 1.3 μm was placed in a silicon nitride container at a depth of about 1.5 μm.
After filling to a maximum of 150 ml, the fine powder raw material was heated in a nitrogen atmosphere for 15 min.
Heat treated by holding at a temperature of 00℃ for 10 hours β'
-Created Sialon main ingredient 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 a trace amount of AA'N.

Next, the above 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, 3% by weight of evaporated silica and 0.5% by weight of boric anhydride were added and mixed to this β'-Sialon main component material powder.
'-sialon mixed material powder, and using this mixed material powder, vinyl acetate was added, kneaded, granulated, and
It is molded by mold pressing (pressure condition: 550 kg/i), and the binder in the molded body is removed by volatilization to obtain a density of 1.83.
A molded body of g/cfIl was made.

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 1500°C at a temperature increase rate of 200°C/Hr. The mixture was held for 3 hours to obtain a β'-SiAlON sintered body.

When the obtained β'-Sialon sintered body was identified by X-ray powder diffraction, it was found that β'-sialon contained a trace amount of α-A120.
3, containing Y-phase sasialon.

Further, it was recognized that this β'-sialon sintered body had a porosity of 2% and was extremely dense.

Example 5 The β'-sialon main component material powder used in Example 1 (
7% by weight of evaporated silica fine powder and 3% by weight of lithium oxide powder (Li20) were added and mixed to the average particle size of 1.2μ to obtain β'-Sialon mixed material powder, and this was prepared under the same conditions as in Example 1. A molded body having a density of 1.89 g/cr71 is produced.

Next, this molded body was buried in a graphite container filled with boron nitride powder, and the container was placed in a firing furnace with a nitrogen atmosphere, and the heating rate was 4.
The temperature was raised to 1250°C under the conditions of 00'C/Hr, and the temperature was maintained for 4 hours to obtain a β'-sialon sintered body.

When the obtained β'-sialon sintered body was identified by X-ray powder diffraction method, it was found that a small amount of α-A1 was present in β'-sialon.
203, was confirmed to contain Y-phase sashyalon.

It was also found that this β'-sialon sintered body had a porosity of 4.2% and was extremely dense even when processed at the above-mentioned low firing temperature (1250°C).

As detailed above, the present invention has low porosity, excellent dimensional stability, and excellent heat resistance, acid resistance, thermal shock resistance, and abrasion resistance, and is suitable for use in the fields of refractories for molten nonferrous metals, refractories for molten steel, etc. It is possible to obtain a dense β'-sialon sintered body which can be effectively used for the purpose of the present invention in an extremely simple and inexpensive manner.

Claims (1)

[Claims] 1 β'-sialon main component material is ground to an average particle size of 1.6 μ or less to obtain βI-sialon main component material powder, and 0.2 to 20% by weight of silica powder and silicate glass are added to the main component material powder. One or more of the metal oxides to be formed is reduced to 0.
2 to 20% by weight is added and mixed to obtain a β'-Sialon mixed material powder, which is molded to a density of 1.79/cIft or more to form a molded body. 1. A method for producing a dense β'-sialon sintered body, which comprises firing at a temperature of 1200 to 1800°C in a gas atmosphere.