JPH04119966A - Production of reaction-sintering silicon carbide sintered body - Google Patents

Abstract

PURPOSE:To mass-produce a reaction-sintering silicon carbide sintered body having excellent performance by molding a mixture powder of silicon carbide powder and carbon powder, calcining to obtain plural calcined bodies, gathering these calcined bodies into an assembly with a carbonaceous material provided among the bodies and impregnating this assembly with molten metal silicon. CONSTITUTION:An org. binder is added to a mixture powder of silicon carbide powder and carbon powder or org. material which can act as the carbon source, and then the mixture is molded and calcined. Plural number of these calcined bodies are gathered into one assemble and impregnated with a molten metal silicon while heating to effect the reaction of silicon and the carbon source in the calcined bodies to obtain the reaction-sintering silicon carbide sintered body. In this process, the following procedure is carried out. Namely, plural calcined bodies 2 are assembled with a carbonaceous material 4 provided among the calcined bodies 2 to form an assemble 1 (contained in a box 3 comprising a carbonaceous material which permeates molten metal silicon), and then the molten metal silicon 6 is made to permeate each calcined body 2 of the assembly 1 through the interposed carbonaceous material 4.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention involves obtaining a calcined body from silicon carbide powder and carbon powder or an organic substance that can serve as a carbon source, and infiltrating the calcined body with molten metal silicon to sinter it. This invention relates to a fR manufacturing method of a reaction-sintered silicon carbide sintered body that advances sintering.

In particular, the present invention relates to a method for producing a reactively sintered silicon carbide sintered body, which allows molten metal silicon to simultaneously and efficiently penetrate into each calcined body of an aggregate composed of a plurality of calcined bodies.

The silicon carbide sintered body has good heat resistance, thermal shock resistance, abrasion resistance, corrosion resistance, etc. even at high temperatures exceeding 1000°C, so it is attracting attention as a structural member that can be used in high-temperature areas. has been done.

Here, silicon carbide is classified into reactive sintered silicon carbide, pressureless sintered silicon carbide, recrystallized silicon carbide, etc. depending on the manufacturing method, and each exhibits characteristic physical properties. Among these, reactive sintered silicon carbide is silicon carbide that is composed of two phases: silicon carbide and metallic silicon, and its sintered body loses its strength at high temperatures around 1400°C, which is the melting point of metallic silicon. Since this material is not observed, it is attracting a lot of attention as a member that can be used not only at room temperature but also in high temperature ranges.

The method for producing this reaction-sintered silicon carbide sintered body is to first mix silicon carbide powder and carbon powder or an organic substance that can be a carbon source, solidify this with an organic binder, and shape it into a desired shape. This molded body is heated to decompose the organic substance and organic binder in the molded body, a part of which is removed from the molded body, and a calcined body is produced in which a part of the organic substance and the organic binder are left as a carbon source. Next, molten silicon metal is infiltrated into this calcined body and reacted with the carbon powder and the residual carbon source to produce silicon carbide. As a result, silicon carbide that is originally present as a raw material in the molded body is surrounded by the generated silicon carbide. In this case, the molten metal silicon infiltrated into the calcined body is always supplied in an amount greater than the amount required to react with the carbon source to form silicon carbide. Therefore, this metallic silicon completely fills the voids in the compact and surrounds not only the silicon carbide powder in the compact but also the produced silicon carbide. Moreover, since metallic silicon undergoes a volumetric expansion of about 8% during solidification, a dense sintered body with no pores that are not wetted can be obtained. In addition, according to this method, there is almost no shrinkage during the sintering process from the calcined body to the sintered body, so if the calcined body is formed with high dimensional accuracy at the time of manufacturing, cutting can be performed after sintering. It is possible to obtain a sintered body with high dimensional accuracy without the need for carrying out other processes. Therefore, this manufacturing method is suitable for manufacturing members with complicated shapes and large-sized members.

Problem to be Solved In this case, various methods have been proposed in the past in order to facilitate and improve the penetration of molten metal silicon in the method of producing such a reaction-sintered silicon carbide sintered body.

For example, there is a method in which molten metal silicon is infiltrated into a calcined body through a porous carbonaceous material (see JP-A-55-67573), a method in which 78 molten metal silicon is infiltrated into a porous cylindrical material, There is a method of dropping the molten metal silicon onto the calcined body from this cylindrical object (see Japanese Patent Application Laid-open No. 190267/1983).

However, even if molten metal silicon is infiltrated by such a method, especially when molten metal silicon is infiltrated into each calcined body of an aggregate consisting of a plurality of calcined bodies at the same time, the molten metal silicon will be infiltrated. Penetration may be insufficient.

That is, when the calcined body is a single body, molten metal silicon can be infiltrated into the calcined body by any method, although the penetration rate may be slow depending on the infiltration method. When an aggregate is formed from calcined bodies, the points of contact between the calcined bodies act as resistance, allowing molten metal silicon to penetrate through the calcined bodies, and even if the molten silicon metal permeates throughout this calcined body, , the penetration of this molten metal silicon may be delayed or traces may be cut off at points where it comes into contact with other calcined bodies, making it impossible to supply a sufficient amount of molten metal silicon to the entire aggregate, reducing the excellent performance described above. There may be cases where a sintered body having the following properties cannot be obtained.

The present invention has been made in view of the above circumstances, and has excellent performance by allowing molten metal silicon to penetrate simultaneously and efficiently into each calcined body of an aggregate composed of a plurality of calcined bodies. It is an object of the present invention to provide a method for manufacturing a reaction-sintered silicon carbide sintered body that can reliably and efficiently manufacture the reaction-sintered silicon carbide sintered body.

Means and Action for Solving the Problems In order to achieve the above object, the inventor of the present invention has conducted extensive studies, and as a result, has produced a mixture of silicon carbide powder and carbon powder or an organic substance that can be a carbon source according to a conventional method. When infiltrating molten metal silicon into multiple aggregates of calcined bodies,
Constructing an aggregate by assembling a plurality of calcined bodies in contact with each other via a carbonaceous material such as a porous carbon material,
By infiltrating molten metal silicon from a part of the aggregate into each calcined body constituting the aggregate through the carbonaceous material, the resistance to penetration between each calcined body of the aggregate can be reduced for each calcined body. This is resolved by the action of the carbonaceous material interposed between the bodies, and a sufficient amount of molten metal scrap silicon is quickly infiltrated and supplied to the entire aggregate, that is, each calcined body, and the reaction (sintering) is quickly and successfully completed. They discovered that it is possible to mass-produce reaction-sintered silicon carbide sintered bodies with excellent performance with good productivity, and completed the present invention.

Therefore, the present invention involves adding an organic binder to a mixed powder consisting of silicon carbide powder and carbon powder or an organic substance that can serve as a carbon source, molding the mixture, heating the resulting molded body to form a calcined body, and In a method for producing a reaction-sintered silicon carbide sintered body, molten metal silicon is infiltrated into an aggregate of a plurality of calcined bodies under heating and reacts with the carbon source in each calcined body. A carbonaceous substance is interposed between the calcined bodies to form an aggregate, and molten silicon metal is infiltrated into each calcined body of the aggregate through the intervening carbonaceous substance. Provided is a method for producing a characteristic reaction-sintered silicon carbide sintered body.

The present invention will be explained in more detail below.

In the method for producing a reactively sintered silicon carbide sintered body of the present invention, first, an organic binder is added to a mixed powder consisting of silicon carbide powder and carbon powder or an organic substance that can be a carbon source, and compression molding is performed. The body is heated to produce a calcined body.

In this case, the silicon carbide powder is not particularly limited, but those with an average particle size of about 0.1 to 40 tones are preferably used, and depending on the use of the sintered body, α type, β type, etc. A type or a mixture thereof can be appropriately selected and used. In addition, the average particle size of the carbon particles is 0.1 to
A material of about 30u is preferably used. Furthermore, examples of organic substances that can serve as carbon sources include silicone resin and phenol resin.

The organic binder added to the mixed powder of silicon carbide and carbon powder or an organic substance that can serve as a carbon source may be any thermosetting binder that produces a carbon source or silicon carbide through thermal decomposition. , phenolic resin, silicone resin, etc., and these can be used after being dissolved in an organic solvent such as ethyl alcohol or acetone.

Here, the mixing ratio of the carbon source of the silicon carbide powder, carbon powder, or organic material and the organic binder is 25 to 70 parts of the carbon source powder, especially about 4 parts, 1 part organic binder
The amount is preferably 5 to 50 parts, particularly about 20 parts, and the mixing method is preferably wet mixing using an organic solvent such as acetone. In addition, when this wet mixing is adopted, after mixing, it is dried and used for molding.
Since the mixture after drying is in a solid state, it is preferable to crush it using a pulperizer or the like, and the particle size is preferably 20 mesh or less, particularly 40 mesh or less.

Next, this mixture is molded, heated and calcined to produce a calcined body. In this case, a compression molding method using a full-form press, a rubber press, etc. is suitably employed as the molding method. Further, the calcination temperature is set to a temperature at which the organic substance and organic binder in the mixture are decomposed and well cured, and specifically, it is usually about 500 to 1000°C. Note that the atmosphere during calcination is preferably an inert gas atmosphere such as argon gas. In addition, the obtained calcined body has
Machining can be performed if necessary.

Next, in the manufacturing method of the present invention, a plurality of the calcined bodies are assembled, a carbonaceous material is interposed between each calcined body, and each calcined body is an aggregate connected by the intervening carbonaceous substance. A plurality of calcined bodies are simultaneously sintered by infiltrating molten metal silicon into each calcined body of the aggregate under heating through the carbonaceous material. In this case, the carbonaceous material is interposed as described above in the areas where the calcined bodies of the aggregate contact each other, but the carbonaceous material is interposed in the areas where the calcined bodies do not contact each other, that is, the spaces formed in the aggregate. It is preferable that a carbonaceous material is disposed in the space, and that the space is filled with the carbonaceous material and that adjacent calcined bodies are connected to each other. Through this sintering process,
The molten metal silicon penetrates well and quickly into each calcined body of the aggregate through the intervening carbonaceous material, and a plurality of sintered bodies having excellent performance can be obtained at once.

This sintering process will be explained with reference to the drawings.

FIG. 1 shows an example of the sintering process of the manufacturing method of the present invention. In the figure, 1 is a calcined body aggregate consisting of a plurality of calcined bodies 2, 2..., and this aggregate 1 is a box 3 made of carbonaceous material containing a plurality of calcined bodies (12 in the figure). 2, 2..., and the molten metal silicon penetration guide material 4, 4... made of a carbonaceous material is placed between each calcined body 2, 2... in contact with the adjacent calcined body. It is constructed by interposing the Note that each calcined body disposed adjacent to the peripheral wall and the bottom wall of the box 3 is in contact with the peripheral wall and the bottom wall of the box 3, respectively. Further, the ends of the guide members 4, 4, . . . on the peripheral wall side and the bottom wall side of the box 3 are in contact with the peripheral wall and the bottom wall, respectively.

Here, as the carbonaceous material constituting the box 3 and the guide material 4, porous carbon material, graphite material, etc. are preferably used.
In particular, fibrous materials are preferred, but the material is not limited to these, and any material that can be penetrated by molten metal silicon may be used.

Next, this aggregate 1 is heated to 1450 to 2000°C, especially at 15°C.
The box 3 is placed in a sintering furnace heated to 00 to 1600°C, and in the furnace the bottom wall of the box 3 is brought into contact with the molten metal silicon 6 placed in the container 5. Molten metal silicon is allowed to penetrate into the calcined bodies 2.2... inside the box 3 through the molten silicon. The atmosphere during this sintering is preferably a non-oxidizing atmosphere. In this case, as shown in FIG. It is also possible to mold several pieces 7 so that their tips come into contact with the molten metal silicon 5, or to bundle the tips of the contact pieces 7 into one piece and make the tips come into contact with the molten metal silicon. It is also possible to do so.

By infiltrating the molten metal silicon through the carbonaceous material into the aggregate of calcined bodies with a carbonaceous substance interposed between each calcined body, the entire aggregate (each calcined body) is rapidly absorbed. As the molten metal silicon permeates, the carbonaceous material interposed between the calcined bodies in the aggregate eliminates the resistance to penetration between the calcined bodies, and the entire aggregate, that is, each calcined body, quickly dissolves. The body is infiltrated with a sufficient amount of molten metal silicon.

Therefore, it is possible to satisfactorily sinter a plurality of calcined bodies at the same time, and it is possible to simultaneously mass-produce a plurality of reaction-sintered silicon carbide sintered bodies having excellent performance with good productivity.

The structure of the aggregate and the method of infiltration of molten metal silicon in the manufacturing method of the present invention are not limited to the aggregate and the method of infiltration shown in FIGS. 1 and 2 above. Any method may be used as long as it is an aggregate in which a carbonaceous substance is interposed, and molten metal silicon is infiltrated into this aggregate through a carbonaceous substance. After reactive sintering, the material can be easily removed from the sintered body by finishing treatments such as etching.

As described above, according to the manufacturing method of the present invention, it is possible to efficiently and reliably infiltrate molten metal silicon into each calcined body constituting the aggregate, and to produce a plurality of particles having excellent performance. It is possible to simultaneously mass-produce several reaction-sintered silicon carbide sintered bodies reliably and with high productivity.

EXAMPLES Hereinafter, the present invention will be explained in more detail by showing examples and comparative examples, but the present invention is not limited to the following examples.

[Example 1] 20 parts of carbon powder (average particle size 3I!m) and 15 parts of phenol resin (resol type) were added to 80 parts (parts by weight, same below) of α-5iC powder (average particle size 5/J11). death,
After mixing for 10 hours using acetone in a ball mill, the mixture was dried under reduced pressure of 1 torr.

After drying, the mixture was pulverized using a pulperizer.

The grains were sized to 200 to 325 mesh. Using a mold press machine, this sized powder was molded into a powder with a diameter of 3 mm at a molding pressure of 1.3 t/al.
0 trm and 50 cylindrical molded bodies with a height of 50 mm were molded. These molded bodies were heated at 500°C in argon gas for 1
After heating for a period of time, the mixture was cooled to obtain 50 calcined bodies.

Next, using a bottomed cylindrical box with an inner diameter of 300 m and a height of 200 mm, and a guide material made of porous carbon material with a width of 8 to 1 o IIll and a length of 10 to 30 III, the temporary Fifty sintered bodies were impregnated with molten metal silicon in a sintering furnace heated to 1500°C, and sintered.

One hour later, when the sintered bodies inside the box were examined, all the sintered bodies had completely reacted (sintered), and no unreacted material had been generated.

[Comparative Example 1] A reactively sintered silicon carbide sintered body was produced in the same manner as in Example 1, except that in the sintering process of Example 1, no guide material was interposed between each calcined body in the box. . Note that sintering was performed for 2 hours.

When the obtained sintered body was examined, many unreacted (unsintered) products were found.

[Example 2] A calcined body was produced in the same manner as in Example 1.

Next, using a bottomed cylindrical graphite box body with an inner diameter of 300 mm and a height of 2000110 mm, a guide material made by cutting graphite yarn into lengths of 8 to 1000, and a contact piece of graphite yarn, the second
According to the method shown in the figure, 50 of the above calcined bodies were heated to 1500°C.
Sintering was performed by infiltrating molten metal silicon in a sintering furnace heated to .

One hour later, when the sintered bodies inside the box were examined, all the sintered bodies had completely reacted (sintered), and no unreacted material had been generated.

[Comparative Example 2] A reaction-sintered silicon carbide sintered body was produced in the same manner as in Example 2, except that no guide material was interposed between each calcined body in the box in the sintering process of Example 2. did. In addition, sintering is 2
I did it for an hour.

When the obtained sintered body was examined, many unreacted (unsintered) products were found.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram for explaining one implementation step of the manufacturing method of the present invention, and FIG. 2 is an explanatory diagram for explaining another example of the same implementation step. 1... Aggregate 2... Calcined body 3... Box (carbonaceous material) 4... Guide material (carbonaceous material) 6.
・・Molten metal silicon

Claims (1)

[Claims] 1. An organic binder is added to a mixed powder consisting of silicon carbide powder and carbon powder or an organic substance that can serve as a carbon source, the mixture is molded, the resulting molded body is heated to form a calcined body, and a plurality of the calcined bodies are combined. In a method for producing a reaction-sintered silicon carbide sintered body in which molten metal silicon is infiltrated into the aggregate under heating and reacts with the carbon source in each calcined body, a plurality of calcined bodies are calcined in each of the calcined bodies. Reactive sintering, characterized in that an aggregate is formed by interposing a carbonaceous material between the bodies, and molten metal silicon is infiltrated into each calcined body of the aggregate through the intervening carbonaceous substance. A method for producing a silicon carbide sintered body.