JPH0735300B2 - Silicon carbide sintered body - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Object of the Invention [Industrial field of use] The present invention relates to a silicon carbide-based sintered body, and in particular, electrical conductivity is ensured by electrical resistivity reduction, and electrical discharge machining is performed. The present invention relates to a silicon carbide-based sintered body which is easy to use and is also usable as a structural material by ensuring mechanical strength.

[Prior Art] Conventionally, as a silicon carbide-based sintered body of this type, II of the periodic table has been used.
It has been proposed to add carbides such as Ia group or IVa group elements, nitrides or borides to silicon carbide powder to make them by hot press sintering, and because their mechanical strength and heat resistance were secured. It was used as a material for machine parts.

[Problems to be Solved] However, in the conventional silicon carbide based sintered material, in order to reduce the electrical resistivity and ensure conductivity, a carbide, a nitride, or a boron of a group IIIa or IVa element of the periodic table is used. Since the compound was compounded in an amount of 30 to 60 parts by volume, there is a drawback that the compounding amount of (i) silicon carbide is relatively decreased, and the sinterability is deteriorated and the sintered body is compressed by pressure sintering. Even if it is made, it has a drawback that its mechanical strength is remarkably reduced. Therefore, (ii) there is a drawback that the shape of the sintered body cannot be complicated, and (iii) the range of application as a structural material is greatly limited. There was a drawback that

In view of the above, the present invention eliminates these drawbacks, lowers the electrical resistivity, secures electrical conductivity and mechanical strength, and thereby facilitates electrical discharge machining and can be used as a structural material. The purpose is to provide a sintered body.

(2) Structure of the Invention [Means for Solving Problems] Therefore, a solution provided by the present invention is as follows: "5 to 25 parts by weight of at least one of chromium and a chromium compound relative to 40 to 85 parts by weight of silicon carbide powder. 10 to 50 parts by weight of at least one of carbides, nitrides and borides of Group IVa and Va of the Periodic Table and elements of Group VIa of the 5th period and below, and oxidized. Only 5 to 25 parts by weight of aluminum powder is blended and sintered at a temperature of 1700 to 2100 ° C. in an inert gas atmosphere.

[Operation] The silicon carbide-based sintered body according to the present invention has the following properties:
To 85 parts by weight, 5 to 25 parts by weight of at least one of chromium and a chromium compound is blended, and IV of the periodic table is used.
At least one of carbides, nitrides and borides of group a and group Va and VIa group elements of the fifth period and below is
Only 10 to 50 parts by weight, and 5 to 25 parts by weight of aluminum oxide powder are mixed, and sintered at a temperature of 1700 to 2100 ° C in an inert gas atmosphere,
(I) It has a function of reducing electrical resistivity and ensuring conductivity, and thus has a function of facilitating electrical discharge machining, and (ii) has a function of securing mechanical strength such as bending strength. .

[Examples] Next, examples of the present invention will be described.

First, the details of one embodiment of the silicon carbide sintered body according to the present invention will be described.

The silicon carbide-based sintered body according to the present invention, the silicon carbide powder 40 ~
To 85 parts by weight, 5 to 25 parts by weight of at least one of chromium and a chromium compound is blended, and IV of the periodic table is used.
Group a (eg, titanium) and Va group elements (eg, tantalum, vanadium, etc.) and VIa of the fifth period or less
At least one of carbides, nitrides and borides of group elements (for example, tungsten) is mixed in an amount of 10 to 50 parts by weight, and aluminum oxide powder is added in an amount of 5 to 25 parts by weight, and then an inert gas is added. 1700-21 in the atmosphere
It is made by sintering at a temperature of 00 ° C.

Here, the compounding amount of at least one of chromium and a chromium compound, an IVa group (for example, titanium) and a Va group element (for example, tantalum, vanadium, etc.) of the periodic table, and a VIa group element of the fifth period or less (for example, tungsten) It is preferable that the total blending amount with the blending amount of at least one of the carbides, nitrides and borides is 12 to 60 parts by weight. That is, if the total blending amount is less than 12 parts by weight, the electrical conductivity of the resulting silicon carbide sintered body will decrease, and if it exceeds 60 parts by weight, the sinterability will deteriorate and its mechanical strength will decrease. This is because it will end up.

The blending amount of the aluminum oxide powder is preferably 5 to 25 parts by weight. That is, if the blending amount is less than 5 parts by weight, the sinterability is deteriorated and the mechanical strength of the resultant silicon carbide based sintered body is lowered, and if it exceeds 25 parts by weight, the mechanical strength and the electrical conductivity are reduced. This is because the sex is hindered. Aluminum oxide does not necessarily have to be added as Al ₂ O ₃ powder, but is added in the form of aluminum alkoxide, organic acid salt, or inorganic acid salt, and is converted to Al ₂ O ₃ by appropriate treatment before sintering. May be.

In addition, 10 parts by weight or less of carbon may be added to improve sinterability and mechanical strength. The reason for limiting the amount of carbon compounded to 10 parts by weight or less is that if the amount exceeds 10 parts by weight, the mechanical strength of the silicon carbide based sintered body will decrease.

Further, in order to deepen the understanding of one embodiment of the above-described silicon carbide sintered body according to the present invention, specific description will be given by using numerical values and the like.

(Example 1) 76 g of silicon carbide SiC powder having an average particle size of 0.5 μm has an average particle size of 3.0.
After addition of 10 g of chromium silicide CrCr ₂ powder of 10 μm and 10 g of titanium carbide TiC powder of average particle diameter of 2.0 μm, carbonization degree of 50
120 ml of acetone solution containing 8% by weight of phenolic resin
Was added and agitated for 100 hours using an alumina pot mill or alumina pot and balls.

The stirred mixture was then dried to remove the solvent and then granulated to obtain a granulated mixture. The granulation mixture contained about 1% aluminum oxide Al ₂ O ₃ mixed from the pot wall and balls because the pot mill was made of alumina.
Only 2% by weight was included.

The granulated mixture was molded by a die press and a rubber press to obtain a molded body of 5 mm × 5 mm × 60 mm. The molded body was housed in a graphite container and sintered at a temperature of 1900 ° C. in an argon atmosphere to obtain a silicon carbide sintered body.

The silicon carbide sintered body was measured for relative density, electrical resistivity and bending strength (three-point bending strength at room temperature, that is, room temperature), and the measurement results are shown in Table 1.

Example 2 Example 1 was repeated except that 10 g of zirconium carbide ZrC powder having an average particle diameter of 3.0 μm was added in place of titanium carbide TiC powder.
Was repeated.

The silicon carbide sintered body was measured for relative density, electrical resistivity and bending strength (three-point bending strength at room temperature, that is, room temperature), and the measurement results are shown in Table 1.

(Example 3) Example 1 was repeated except that 10 g of tantalum carbide TaC powder having an average particle size of 3.0 µm was added in place of the titanium carbide TiC powder.

The silicon carbide sintered body was measured for relative density, electrical resistivity and bending strength (three-point bending strength at room temperature, that is, room temperature), and the measurement results are shown in Table 1.

(Example 4) The amount of silicon carbide SiC powder used was 71 g, and titanium carbide was used.
Example 1 was repeated except that the amount of TiC powder blended was 15 g.

The silicon carbide sintered body was measured for relative density, electrical resistivity and bending strength (three-point bending strength at room temperature, that is, room temperature), and the measurement results are shown in Table 1.

(Example 5) Titanium nitride having an average particle size of 2.0 μm instead of titanium carbide TiC powder
Example 1 was repeated except that 10 g of TiN powder was added.

The silicon carbide sintered body was measured for relative density, electrical resistivity and bending strength (three-point bending strength at room temperature, that is, room temperature), and the measurement results are shown in Table 1.

Example 6 54 g of silicon carbide SiC powder having an average particle size of 0.5 μm has an average particle size of 3.0.
After adding 7 g of chromium silicide CrCr ₂ powder of 35 μm and 35 g of titanium boride TiB ₂ powder of average particle size 2.0 μm, carbonization degree 5
120 ml of acetone solution containing 8 g of 0% by weight phenolic resin
Was added and agitated using an alumina pot mill or pot and balls for 50 hours.

The stirred mixture was then dried to remove the solvent and then granulated to obtain a granulated mixture. Since the pot mill was made of alumina, the granulation mixture contained approximately ₂ % aluminum oxide Al ₂ O ₃ mixed from the pot wall and balls.
Only 6.0% by weight was included.

The granulated mixture was molded by a die press and a rubber press to obtain a molded body of 5 mm × 5 mm × 60 mm. The molded body was housed in a graphite container and sintered at a temperature of 1850 ° C. in an argon atmosphere to obtain a silicon carbide sintered body.

The silicon carbide sintered body was measured for relative density, electrical resistivity and bending strength (three-point bending strength at room temperature, that is, room temperature), and the measurement results are shown in Table 1.

Example 7 The amounts of silicon carbide SiC powder and titanium boride TiB ₂ powder used were 48 g and 38 g, respectively, and chromium silicide CrSi _{2 was used.}
Instead of powder, 10 g of chromium carbide Cr ₃ C ₂ powder with an average particle size of 5.6 μm
Example 6 was repeated except that was added.

The silicon carbide sintered body was measured for relative density, electrical resistivity and bending strength (three-point bending strength at room temperature, that is, room temperature), and the measurement results are shown in Table 1.

(Example 8) The amount of silicon carbide SiC powder used was 71 g, and titanium carbide was used.
Zirconium boride Zr with an average particle size of 8.0 μm instead of TiC powder
Example 1 was repeated except that 15 g of B ₂ powder was added.

The silicon carbide sintered body was measured for relative density, electrical resistivity and bending strength (three-point bending strength at room temperature, that is, room temperature), and the measurement results are shown in Table 1.

(Example 9) The amount of silicon carbide SiC powder used was 82 g, and chromium silicide was used.
Example 1 was repeated except that 4.0 g of chromium Cr powder having an average particle size of 1.0 μm was added instead of CrSi ₂ powder.

The silicon carbide sintered body was measured for relative density, electrical resistivity and bending strength (three-point bending strength at room temperature, that is, room temperature), and the measurement results are shown in Table 1.

Example 10 76 g of silicon carbide SiC powder having an average particle size of 0.5 μm has an average particle size of 3.0.
After addition of 10 g of chromium silicide CrCr ₂ powder of 10 μm, 10 g of titanium carbide TiC powder of average particle size of 2.0 μm and 10 g of aluminum oxide Al ₂ O ₃ powder of 0.5 μm of average particle size, a phenol resin having a carbonization degree of 50% by weight is further added. 120 ml of an acetone solution containing 8 g was added and mixed with stirring for 20 hours using a plastic pot mill, polypot and monoball.

The stirred mixture was then dried to remove the solvent and then granulated to obtain a granulated mixture. Since the pot mill was made of plastic, the granulation mixture did not contain aluminum oxide Al ₂ O ₃ from the pot wall or balls unlike Example 1.

The granulated mixture was molded by a die press and a rubber press to obtain a molded body of 5 mm × 5 mm × 60 mm. The molded body was housed in a graphite container and sintered at a temperature of 1900 ° C. in an argon atmosphere to obtain a silicon carbide sintered body.

The silicon carbide sintered body was measured for relative density, electrical resistivity and bending strength (three-point bending strength at room temperature, that is, room temperature), and the measurement results are shown in Table 1.

Example 11 Example 1 was repeated except that the amount of silicon carbide SiC powder used was 80 g and 4 g of vinyl acetate was added in place of the phenolic resin.

The silicon carbide sintered body was measured for relative density, electrical resistivity and bending strength (three-point bending strength at room temperature, that is, room temperature), and the measurement results are shown in Table 1.

(Comparative Example 1) 76 g of silicon carbide SiC powder having an average particle size of 0.5 μm has an average particle size of 3.0.
After adding 20 g of chromium silicidated CrSi ₂ powder having a particle size of 120 μm, 120 ml of an acetone solution containing 8 g of a phenol resin having a carbonization degree of 50% by weight was further added and mixed with stirring in an alumina pot mill for 10 hours.

The stirred mixture was then dried to remove the solvent and then granulated to obtain a granulated mixture. The granulation mixture contained about 1% aluminum oxide Al ₂ O ₃ mixed from the pot wall and balls because the pot mill was made of alumina.
Only 2% by weight was included.

The granulated mixture was molded by a die press and a rubber press to obtain a molded body of 5 mm × 5 mm × 60 mm. The molded body was housed in a graphite container and sintered at a temperature of 1900 ° C. in an argon atmosphere to obtain a silicon carbide sintered body.

The silicon carbide sintered body was measured for relative density, electrical resistivity and bending strength (three-point bending strength at room temperature, that is, room temperature), and the measurement results are shown in Table 1.

Comparative Example 2 86 g of silicon carbide SiC powder having an average particle size of 0.5 μm has an average particle size of 0.5.
Aluminum oxide Al ₂ O ₃ powder 10 μm and average particle size 2.0 μ
m addition of titanium carbide TiC10g and then carbonization degree
Acetone solution 120m containing 8g of 50 wt% phenolic resin
1 was added and mixed using a plastic pot mill, polypot and monoball, for 20 hours with stirring.

The stirred mixture was then dried to remove the solvent and then granulated to obtain a granulated mixture. Since the pot mill was made of plastic, the granulated mixture was not mixed with aluminum oxide Al ₂ O ₃ from the pot wall or balls unlike Comparative Example 1.

The granulated mixture was molded by a die press and a rubber press to obtain a molded body of 5 mm × 5 mm × 60 mm. The molded body was housed in a graphite container and sintered at a temperature of 1900 ° C. in an argon atmosphere to obtain a silicon carbide sintered body.

The silicon carbide sintered body was measured for relative density, electrical resistivity and bending strength (three-point bending strength at room temperature, that is, room temperature), and the measurement results are shown in Table 1.

As is apparent from Table 1, according to the present invention, the electrical resistivity of the silicon carbide-based sintered body can be reduced to 10 Ωcm or less as compared with the comparative example, and the bending strength is also compared with the comparative example. Can be made bigger. Therefore, according to the present invention, the electric discharge machining of the silicon carbide sintered body can be facilitated, and even a shape having a large depth can be machined in a short time, and high strength and high toughness can be secured.

Although the particle size of the silicon carbide SiC powder is 0.5 μm in the above-mentioned embodiments, the present invention is not limited to this. However, considering the mechanical strength of the silicon carbide sintered body, the particle size of the silicon carbide SiC powder is especially 1 μm.
The following is preferable.

(3) Effects of the Invention As is clear from the above, the silicon carbide-based sintered body according to the present invention contains 5 to 25 parts by weight of at least one of chromium and a chromium compound with respect to 40 to 85 parts by weight of silicon carbide powder. Blended,
In addition, 10 to 50 parts by weight of at least one of carbides, nitrides and borides of group IVa and group Va of the periodic table and group VIa of the fifth period or less is mixed, and aluminum oxide powder 5 Only 25 parts by weight are blended and sintered at a temperature of 1700 ° C to 2100 ° C in an inert gas atmosphere. (A) It has the effect of reducing the electrical resistivity to 10 Ωcm or less. As a result, (b) it has the effect of facilitating electrical discharge machining, and at the same time, it has the effect of (c) increasing the mechanical strength, such as bending strength, and achieving high strength and high toughness.

Claims (5)

[Claims] 1. To 40 to 85 parts by weight of silicon carbide powder, 5 to 25 parts by weight of at least one of chromium and a chromium compound is blended, and the group IVa and Va elements of the periodic table and elements of the fifth period or less are used. 10 to 50 parts by weight of at least one kind of carbides, nitrides and borides of VIa group elements, and 5 to 25 parts by weight of aluminum oxide powder are mixed in an inert gas atmosphere of 1700. A silicon carbide-based sintered body characterized by being sintered at a temperature of up to 2100 ° C. 2. A total combination of at least one of chromium and a chromium compound and at least one of carbides, nitrides and borides of group IVa and group Va elements of the periodic table and group VIa elements of the fifth period and below. The amount is 12 to 60 parts by weight, and the silicon carbide based sintered body according to claim (1) is characterized in that. 3. A silicon carbide-based sintered body according to claim 1, wherein carbon is added in an amount of 10 parts by weight or less to the silicon carbide powder. . 4. The silicon carbide based sintered body according to any one of claims (1) to (3), wherein the chromium compound is chromium carbide and chromium silicide. 5. The electrical resistivity is 10 Ωcm or less at room temperature,
The silicon carbide-based sintered body according to any one of claims (1) to (4), wherein the bending strength is 400 MPa or more at room temperature.