JPS5934676B2 - Method for producing a reaction fired product containing β′-Sialon as the main component - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a reaction fired product containing β'sialon as a main component.

Conventionally, various methods have been proposed as methods for producing reaction-fired products containing β'-sialon (β' 5ialon) as a main component.

For example, a mixed green compact of silica powder and aluminum powder is fired in a nitrogen-containing non-oxidizing gas atmosphere to produce β'-
A method of producing a reaction-fired body containing Sialon as a main component has been carried out.

However, the reaction fired body obtained by this method has a porosity of 40
% or more, the density is poor, and the pore size is 0.1 to 10
It has a large μ, which gives it strength, oxidation resistance, and chemical stability (
In particular, it has low alkali resistance), poor corrosion resistance against high-temperature molten aluminum, and high air permeability, making it impractical.

The present invention was made to eliminate the above-mentioned drawbacks, and has excellent oxidation resistance, chemical stability, and AA, Zn, Pb
β′- has corrosion resistance against molten non-ferrous metals such as
A method for producing a reaction sintered body mainly composed of sialon, and a method for producing a reaction sintered body mainly composed of β'-sialon, which has the above properties as well as denseness, good dimensional stability, and high strength, hardness, thermal shock resistance, and heat resistance. It is an object of the present invention to provide a method for producing a reaction fired body as a component.

The present invention will be explained in detail below.

First, 10 to 1000 parts by weight of metal silicon powder is added to 100 parts by weight of a mixed powder consisting of 20 to 80% by weight of evaporated silica powder and 80 to 20% by weight of aluminum powder, and the mixture is thoroughly mixed to obtain a starting raw material powder.

Subsequently, this starting raw material powder is molded into a desired shape by various molding methods, such as mold pressing, rubber pressing, slip casting, extrusion molding, etc., and then the green compact is heated to 1200°C in a nitrogen-containing non-oxidizing gas atmosphere. ~1550°
The reaction product is fired at a temperature of C to produce a reaction fired product containing β'-sialon as a main component.

Volatile silica used in the present invention
Unlike ordinary amorphous or crystalline silica, silica is an ultrafine powder with few impurities, so it has good reactivity, produces a large amount of β'-SiAlON, and can shorten the firing time. Most preferred.

Examples of the aluminum powder used in the present invention include teardrop-shaped atomized aluminum powder (sprayed powder), scale-shaped ground powder, etc., and it is particularly desirable to use a powder with a particle size of less than 50 mesh.

The metal silicon powder used in the present invention preferably has a particle size of less than 200 mesh, and its properties may be crystalline or amorphous.

In some cases, ferrosilicon powder can also be used.

The reason why the ratio of evaporated silica powder to aluminum powder (SiO2 powder O M powder) in the present invention is limited to the above range is that the ratio of Si02 powder/Al powder is 20/80 (
If the weight ratio is smaller, unreacted Al may coexist, the amount of A6N and/or Y-phase sialon will increase, and the amount of β'-sialon will inevitably decrease, resulting in a strong reaction fired product. This is because it cannot be obtained.

On the other hand, if the ratio of Si02 powder/Al powder exceeds 80/20, unreacted 5i02 may remain, mullite,
-phase, 0'-sialon (silicon oxynitride (Si2ON2)
(solid solution containing Al2O3) increases,
This is because the properties (strength, corrosion resistance, etc.) of the reaction-fired body obtained are impaired accordingly.

The preferred range is a ratio of 5i02 powder/Al powder of 63/3.
7 to 50150.

The reason why the amount of metal silicon powder is limited to the above range with respect to 100 parts by weight of the mixed powder of evaporated silica powder and aluminum powder in the present invention is that if the amount of metal silicon powder is less than 10 parts by weight, it will not be possible to achieve the intended purpose. If the characteristics of a certain reaction-fired body cannot be sufficiently improved and the amount of metal silicon powder added exceeds 1000 parts by weight, the amount of metal silicon powder becomes too large (too much, and Si fusion occurs during the temperature rising process). This is because the nitriding reaction is inhibited, and therefore, the firing conditions must be strictly controlled to prevent this fusion of Si, leading to complicated operations and increased costs.

In this case, the blending ratio of the metal silicon powder is determined from the viewpoint of increasing the amount of β'-SiAlON produced and obtaining a reaction fired body with a strong structure. ) is desirably selected as appropriate within the above-mentioned range.

Specifically, the ratio of 5i02 powder/Al powder is 65/35.
When using a mixed powder of ~45155 (weight ratio), 10~45155 (weight ratio) of metal silicon powder is added to 100 parts by weight of the mixed powder.
Add 1000 parts by weight.

Also, the ratio of SiO2 powder/AA powder is 80/20~65
/35, or 45155 to 20/80 (weight ratio), 40 to 1000 parts by weight, preferably 60 to 1000 parts by weight of metal silicon powder may be added to 100 parts by weight of the mixed powder. desirable.

Examples of the nitrogen-containing non-oxidizing gas used in the present invention include nitrogen gas alone, nitrogen gas and an inert gas such as argon gas or neon gas, or a mixed gas of hydrogen gas, ammonia gas, etc. .

In the present invention, the reason why the firing temperature is limited to the above range is that when the firing temperature is less than 1200°C, the nitriding reaction rate of the molded body is slow and it takes a long time to obtain a reaction fired body; When the temperature exceeds 1550'C, Si component, Si
This is because the O2 component or the S i 3 N4 component volatilizes and dissipates, resulting in a porous structure, an increased amount of Y-phase sashyalon, and sintering cracks.

The preferred firing temperature and firing time are 1400 to 1500
℃ temperature for 5 to 20 hours.

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

First, the reaction sintered body obtained according to the first invention of the present application is pulverized,
Shape this pulverized powder using an appropriate binder, or
Alternatively, the reaction fired body may be used as it is, or after being processed with a diamond cutter, polisher, etc. as necessary, it is buried in non-reactive packing powder and heated for 16 hours in a non-oxidizing atmosphere.
A reaction sintered body containing β'-sialon as a main component is produced by heat treatment at a temperature of 00 to 1900°C.

That is, the first invention described above is a method for efficiently reacting the firing raw material to β'-sialon, and the OXX humidity temperature is limited to 1200 to 1550°C, but the second invention of the present invention The present invention was made in order to further sinter and densify the formed body of the β'-sialon component produced.

In this case, if the temperature is simply raised to 1,600 to 19,000 C, as described above, a portion of the component will be volatilized, making it difficult to obtain the β' sialon component.

However, it is embedded in a stuffing powder that has heat resistance and does not react with β'-sialon and is heated to 1,600 to 1,900°C.

Examples of the non-reactive packing powder used in the second invention of the present application include boron nitride powder (BN), aluminum nitride powder (Al
N), silicon nitride powder, graphite powder, etc.

The non-oxidizing gas used in the second invention of the present application is a single gas or a mixed gas selected from inert gases such as nitrogen gas, ammonia gas, argon gas, and neon gas.

The reason why the heat treatment temperature is limited to the above range in the second invention of the present application is that if the temperature is lower than 1600°C, the solid solution of Al2O3 and A7N into β'-sialon in the fired body is sufficiently promoted. On the other hand, the temperature is 19
If the temperature rises above 00°C, Si will disappear even if it is buried in the packed powder.
The amount of volatilization of O2 component and Si3N4 component increases and
This is because a porous altered layer is formed on the surface of the fired body due to a decrease in the amount of sialon produced or an increase in Y-phase sialon.

In this case, the preferable heat treatment temperature is 1700 to 1.75
It is in the range of 00G.

Note that this heat treatment temperature is the above-mentioned firing temperature (1200
During this heat treatment, the Si component, SiO2 component, or Si3N component of the fired body is
It is thought that volatilization and dissipation of the four components may occur, but volatilization is suppressed because the powder is buried and fired in the stuffing powder, which is heat resistant and does not easily react with β-sialon.

Furthermore, the thermal stability of the reaction-fired product obtained at the above-mentioned firing temperature is significantly improved under the high-temperature conditions.
~1900°C), the above-mentioned components hardly volatilize.

In the first invention, if necessary, a small amount (0.2 to 10% by weight) of fine alumina powder, fine silicon nitride powder, and fine nitride powder are added to the mixture of the above-mentioned evaporated silica powder, aluminum powder, and metal silicon powder. Fine aluminum powder may be added and used as the starting raw material powder.

In addition, in the first invention, the nitriding reaction O
For the purpose of improving sintering properties, improving corrosion resistance, thermal shock resistance, and making it possible to manufacture large products, medium-grained and coarse-grained alumina, silicon nitride, silicon carbide,
β'-sialon, zirconia or zircon may be blended as a starting material.

Furthermore, in the present invention, if necessary, the reaction fired product containing β'-sialon as a main component obtained in the first and second inventions is re-pulverized and sieved into fine, medium, and coarse particles. A sintered body containing β'-sialon as a main component may be produced by molding the mixed grains of these in accordance with a conventional method, and then heating the molded body at a temperature of about 1,600 to 20,000 C in a nitrogen-containing atmosphere. .

In this case, shrinkage of the molded product during firing can be significantly suppressed, deformation and cracking can be completely eliminated, and in addition to making it possible to manufacture large-sized products, it is also possible to produce ultra-dense β′-sialon with extremely low porosity. A sintered body having the main component can be obtained.

According to the present invention, a predetermined amount of metal silicon powder is blended into a mixed powder of evaporated silica powder and aluminum powder at a predetermined mixing ratio to form a starting material, which is then molded in a nitrogen-containing non-oxidizing gas atmosphere. By firing under a certain temperature range, it has good dimensional stability, excellent oxidation resistance, chemical stability (especially alkali resistance), and A
l.

To obtain a reaction sintered body mainly composed of dense β'-sialon, which has corrosion resistance against non-ferrous metals such as Zn and Pb, and molten ferrous metals, and has high strength, hardness, thermal shock resistance, and heat resistance. I can do it.

The mechanism by which reaction-fired products having various excellent properties are produced by the method of the present invention is not clear, but according to research conducted by the present inventors, it is believed that the products are produced by the following reaction.

1) Below 1000℃, 3Si02+4A#→3Si+2A1203...
・σ) 2Al + N2 → 2AIN ・・・・
...Wholesale 1i) At 10oo'C or higher, 3 S 1-1-2N2 → β-8i 3 N4
・・・・・・■Al2O3, Al to β-ni Si3N4
Solid solution of N → β′-Sialon ・・・・・・ ′(IV
) That is, below 100°C, aluminum powder with a melting point of 660°C melts and penetrates into the space between the evaporated silica powder and metal silicon powder, and when it comes into close contact with the 5102 powder, it becomes active as shown in the reaction formula α) above. Generates high Sl.

At the same time, the aluminum powder was heated to about 600'C (II
) As shown in the reaction formula, a nitriding reaction occurs to form A7N, and some of the aluminum powder is covered with an A7N film.
Maintains powder state even at temperatures above 6600C.

Note that the reactions α) and ([) above are exothermic reactions, and this heat generation increases the temperature of the compact, which will be described later in (III).
, promotes the reaction of (IV), and its ([),
Continuously transferred to reaction (IV).

Continuing, ■ At temperatures above 000°C, the metal silicon powder in the molded body is
3 and A7N crystals, the above (I)
, due to the exothermic reaction of (I) and (III), Si
Even if the temperature exceeds the melting point of (14200G), the fusion of the metal silicon powder is prevented.

Moreover, since the Si produced in the reaction (I) above is highly active and fine, the reaction formula (III) shows the reaction (
It easily undergoes a nitriding reaction to become β-8i 3 N4, which promotes the separation of the initially mixed metal silicon powder and prevents the metal silicon powder from fusing with the Si generated in the reaction α) above. .

Therefore, the initially mixed metal silicon powder is maintained in a powder state without fusing with each other or with the generated Si, and is efficiently nitrided to β-8i3N4 as shown in reaction formula (III) above. is produced, thereby a sufficient amount of β-8i3N4 is produced, and the residual rate of unreacted Si is significantly reduced.

Next, the Al2 produced in the reaction of (I) and [) above
O3 and AlN and a sufficient amount of β-8i3N4 produced in the above reaction (III) undergo a solid solution reaction as shown in reaction formula (IV) to produce β'-sialon.

As described above, it is believed that according to the present invention, a reaction sintered body containing β'-sialon as a main component having the above-mentioned various properties can be easily and efficiently obtained by the reactions (I) to (IV) above. .

Further, according to the second invention of the present application, - the above-mentioned reaction fired body is further buried in a non-reactive stuffing powder and heated for 1,600 hours in a non-oxidizing atmosphere.
By heat treatment at a temperature of ~1900'C, sinterability progresses and the solid solution reaction between Al2O3, AlN and β-8i3N4 described above is promoted and the production of β'-sialon increases. Among the various properties mentioned above, it is possible to obtain a reaction-sintered body containing β'-sialon as a main component, which has further improved compactness, dimensional stability, oxidation resistance, and strength.

Therefore, since the reaction-fired products obtained according to the first and second inventions of the present application have the various excellent properties described above, they 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, pump sliding parts for molten non-ferrous metals (hot chamber pistons, cylinders), goosenecks, crucibles for melting semiconductors such as germanium or silicon.

■ Various nozzles for continuous casting of refractories for molten steel, plates for sliding nozzles, and immersion pipes.

■ Mechanical parts heat exchangers, piston heads and cylinders in piston engines, combustion chamber structural materials (rotors, stators, shrouds, etc.) in gas turbine engines, rocket nozzles.

■ Corrosion-resistant materials Acid-resistant and alkali-resistant containers, pipes for transporting chlorine or hydrogen sulfide gas, chlorine gas injection pipes, and lining materials for firing furnaces such as plastic.

Next, the present invention will be explained in detail.

Examples 1 to 4 The starting raw material powders as shown in Table 1 below were dry mixed in a V-mixer and molded using a rubber press (1 ton/i) to form a green compact of io"X100XIOcm. This green compact was heated at a rate of 100°C/H in a nitrogen atmosphere.
Raise the temperature to 1450℃ under the condition of r and 10℃ under that temperature.
By holding and firing for a certain period of time, a reaction fired product containing four types of β'-sialon as a main component was obtained.

On the other hand, as a comparative example, silica fine powder and AA atomized powder (-250 mesh) were mixed in a V mixer as a starting material, and this was molded with a rubber press (Iton/ci) to form a 10" x 100 x 10 HcrrL compact. This was then fired under the same conditions as in Examples 1 to 4 to obtain a reaction fired product containing β'-sialon as a main component.

Therefore, the β'-
The physical properties of a reaction-fired body containing Sialon as the main component were investigated.

The results are also listed in Table 1. As is clear from Table 1 above, the reaction-fired body obtained by the present invention has a higher β'-sialon content, strength, chemical stability, and acid resistance than the reaction-fired body obtained by the conventional method. It can be seen that it is extremely excellent in all aspects of chemical properties.

Examples 5 to 6 The reaction-fired bodies of Examples 2 and 3 above were buried in a packed powder consisting of 60 weight silicon nitride wires and 40 weight boron nitride wires in a graphite container, and the heating rate was adjusted under a nitrogen atmosphere. 200℃/H
The temperature was raised to 1700° C. under the condition of r, and the temperature was maintained for 4 hours for heat treatment, and then the temperature was lowered and slowly cooled under the condition of 200° C./hr to obtain a fired body.

When the physical properties of the obtained fired body were examined, the results were as shown in Table 2 below.

As is clear from the above table, the reaction fired product (
By further heat-treating the products of Examples 2 and 3, the resulting fired products had significantly higher β'-sialon content, density, alkali resistance, and oxidation resistance than those before the heat treatment. I can see that it will be improved.

As detailed above, according to the present invention, it has good dimensional stability, excellent oxidation resistance, chemical stability, and Al
It has corrosion resistance against molten nonferrous metals such as Zny Cut Pb, and has high strength, hardness, thermal shock resistance, and heat resistance, and is effective in a wide range of fields such as refractories for ferrous metals and refractories for molten steel. It is possible to provide a reaction-sintered body containing dense β'-sialon as a main component, which can be used for.

Further, according to the second invention of the present application, it is possible to provide a fired body mainly composed of β'-sialon, which has significantly improved compactness, mechanical strength, alkali resistance, and oxidation resistance among the above-mentioned properties. It is something.

Claims (1)

[Claims] 1. 10 to 1000 parts by weight of metallic silicon powder are added to 100 parts by weight of a mixed powder consisting of 20 to 80 layers of evaporated silica powder and 80 to 20 layers of aluminum powder, and the mixture is thoroughly mixed. After forming the raw material powder into a green compact, the green compact is heated for 12 hours in a nitrogen-containing non-oxidizing gas atmosphere.
1. A method for producing a reaction fired product containing β'-Sialon as a main component, the method comprising firing at a temperature of 00 to 1550°C. 2. To 100 parts by weight of a mixed powder consisting of evaporated silica powder with 20 to 80 layers and aluminum powder with 80 to 20 layers, add 1'0 to 1000 parts by weight of metal silicon powder and mix thoroughly to obtain a starting raw material powder, After molding this into a molded body, this molded body is fired at a temperature of 1200 to 1550°C in a nitrogen-containing non-oxidizing gas atmosphere to form a fired body. 1. A method for producing a reaction fired product containing β'-sialon as a main component, which comprises immersing it in packed powder and heat-treating it at a temperature of 1,600 to 19,000 C in a non-oxidizing gas atmosphere.