JPH04126285A - Seal and production thereof - Google Patents

Abstract

PURPOSE:To obtain a seal having a light weight, a sufficient strength, and resistances to corrosion, change of properties, and burning by a method wherein a second silicon carbide powder synthesized in a specific method and specified in average particle diameter is mixed in a specific ratio in a first silicon carbide powder specified in average particle diameter, and a sealing part is provided in a sintered body obtained by heating and sintering this mixture. CONSTITUTION:Material gas made of a silane compound or a silicon halide and a hydrocarbon is led into a plasma in a non-oxidizing atmosphere to be synthesized with each other by a gas phase reaction while a pressure of a reaction system is controlled to range from 0.1Torr to less than an atmospheric pressure, whereby a second silicon carbide powder having an average particle diameter of 0.1mum or less is obtained. A first silicon carbide powder having an average particle diameter of 0.1-10mum contains 0.5wt.% or more second silicon carbide powder. A sintered silicon carbide body is obtained by heating and sintering this mixture. The seal material made of the sintered body has a conductivity of an electric resistance of 1OMEGA.cm or less, a sintering density of 3.0g/cm<3>, and a three-point bending strength of 50.0kg/mm<2> or more. This seal material is cut into a cylindrical form, ground, and polished to be finished into a seal form. One end face thereof is subjected to electric discharge machining using electrodes, whereby a sealing part 2 is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a seal made of a conductive silicon carbide sintered body and a method for manufacturing the same.

"Conventional Technology and Its Problems" Conventional seals are made from extremely valuable natural resources such as ivory, buffalo horn, crystal, and boxwood. but,
In recent years, demands for the protection of natural resources have increased, and for example, the import of ivory, a typical material, is prohibited from the standpoint of nature protection.

Therefore, there is a desire to switch from these seals made from natural resources to seals made from artificial materials, and along with this, there is a strong demand for artificial materials that can substitute for natural resource materials.

In addition, natural resource materials such as ivory, buffalo horn, crystal, and boxwood are weak in strength, so seals made of these materials may be damaged by falling, burned out by fire, or even stored at high temperatures for long periods of time. Due to deterioration, deformation, insect damage, etc., it may no longer function as a seal.

Against this background, it has been used as a material for seals for some time.
The use of ceramics, which can be artificially produced from abundant raw materials and has excellent features such as being lightweight, strong, and free from corrosion, deterioration, and burnout, has been considered and proposed (Unexamined Japanese Patent Publication No. No. 60-131861), (Japanese Patent Application Laid-Open No. 62-212257).

However, since ceramics are difficult-to-process materials,
It has the problem of poor grinding and workability. Therefore,
In order to solve this problem when engraving a stamp part, for example, in the above-mentioned Japanese Patent Application Laid-Open No. 60-131861, a method is proposed in which a ceramic molded body is cut before sintering, and then sintered and finished. , and the above-mentioned Japanese Patent Application Laid-Open No. 62-21
No. 2257 employs a method in which a ceramic molded body is calcined at a temperature lower than the sintering temperature, subjected to cutting, and then sintered. However, in these methods, it is difficult to process fine details because the strength of the molded body or calcined body to be processed is insufficient, and chipping is likely to occur. Furthermore, since main sintering is performed after processing, the influence of shrinkage of the ceramic during sintering cannot be avoided.

Since the shrinkage rate of the design of the characters, etc. on the stamp part, which is the life of the seal, differs depending on the part, the shrinkage during the main sintering process may cause the characters, etc. to become unbalanced, and the stamp part will not be able to form the desired shape. There are complaints that precision cannot be maintained, and in some cases, machining such as cutting is required again after main sintering.

In addition, if the stamp obtained in this way is damaged due to an unexpected accident such as falling, the stamp section must be processed as described above before main sintering. Therefore, it is impossible to reprocess a stamp whose stamp part, which is a sintered body, has been damaged, and there is a dissatisfaction that the life of the stamp is short.

The present invention was made in view of this technical background, and is lightweight, has sufficient strength, and is resistant to corrosion, deterioration, burnout, etc. The object of the present invention is to provide a seal that is processed by the above process and a method for manufacturing the same.

"Means for Solving the Problem" The seal stamp according to claim 1 of the present invention is fired without adding a sintering aid, and has a sintered body density of 3. The above-mentioned problem is solved by being made of a silicon carbide sintered body having an electrical resistance of 0 g/mm2 or more, an electrical resistance value of 1 Ω・C- or less at room temperature, and a three-point bending strength of 50,0 kg/am” or more at room temperature. It was used as a means.

In the method for producing a seal stamp according to claim 2, the first silicon carbide powder having an average particle size of 0.1 to 10 μm is mixed with a silane compound or a silicon halide and a hydrocarbon in plasma in a non-oxidizing atmosphere. The average particle diameter synthesized by introducing a source gas of
A silicon carbide sintered body is obtained by mixing 0.5 fl % or more of a second silicon carbide powder with a particle size of 1μ or less, heating and sintering this, and forming a stamp part on this sintered body to make a seal. This is the solution to the above problem.

In the method for manufacturing a seal according to claim 3, a raw material gas consisting of a silane compound or a silicon halide and a hydrocarbon is introduced into plasma in a non-oxidizing atmosphere, and the pressure of the reaction system is increased from less than 1 atmosphere to 0.1 torr. The average particle diameter synthesized by controlling the gas phase reaction within the range of 0.1μ
A means for solving the above-mentioned problem is to obtain a silicon carbide sintered body by heating and sintering silicon carbide powder having a particle size of less than m, and to form a seal by providing a stamp part on this sintered body.

Furthermore, in the method for producing a seal stamp according to a fourth aspect of the present invention, a means for solving the above problem is to carve a stamp portion by electrical discharge machining the stamp surface of the stamp material obtained from the sintered body.

The present invention will be explained in detail below.

FIG. 1 is a diagram showing an example of a seal stamp according to claim 1 of the present invention, and in FIG. 1, reference numeral 1 indicates a seal stamp. This stamp 1 is fired without the addition of sintering aids, has a sintered body density of 3.0 g/am' or more, an electrical resistance value of 1 Ω・c1 or less at room temperature, and is 3-point bent at room temperature. The strength of
0,0 kg/@11″100 It is a cylindrical piece made of 100 silicon carbide sintered body, and has a stamped part 2 on one end surface.
was formed.

To manufacture such a seal l, first, prepare a first silicon carbide powder with an average particle size of 0.1 to 10 μm and a second silicon carbide powder with an average particle size of 0.1 μm or less. . Here, the first silicon carbide powder may be one commonly used, and for example, one manufactured by a method such as a silica reduction method or an Acheson method can be used. The crystalline phase of silicon carbide may be amorphous, α-type, β-type, or a mixed phase thereof. In addition, the average particle diameter of this silicon carbide powder is 0.1-1μ.
This is desirable because it improves sinterability.

In addition, as the second silicon carbide powder, a raw material gas of a silane compound or silicon halide and a hydrocarbon is introduced into plasma in a non-oxidizing atmosphere, and the pressure of the reaction system is set in a range from less than 1 atm to Q, l torr. The product obtained by controlling the gas phase reaction is used. For example, if a raw material gas consisting of monosilane and methane is introduced into an argon plasma excited by radio frequency and synthesized,
β with an average particle diameter of 0.02μ and a small aspect ratio
Depending on the synthesis conditions, a mixed phase of α-type and β-type can be obtained.

The ultrafine powder obtained in this way has very good sinterability, so it can be mixed with the first silicon carbide powder to produce dense silicon carbide sintered material without adding any sintering aid. You will be able to obtain a body.

Next, raw material powder for the seal stamp 1 is obtained using these powders. Here, as the raw material powder, a mixed powder obtained by mixing the first silicon carbide powder and the second silicon carbide powder may be used, or the second silicon carbide powder may be used alone. When mixing the first silicon carbide powder and the second silicon carbide powder, if the blending amount of the second silicon carbide powder is less than 0.5% by weight, the characteristics of the second silicon carbide powder Since a certain excellent sinterability cannot be obtained and the density of the sintered body is impaired, the effect of blending it cannot be fully exhibited, so the blending amount must be 0.5% by weight or more. Must be.

Next, the above-mentioned mixed powder or second silicon carbide powder is molded into a desired shape as a stamp material, and the obtained molded body is heated in a temperature range of 1800°C to 2400°C, and is further molded without the addition of a sintering aid. Sinter to obtain silicon carbide. When molding silicon carbide powder, press molding method, extrusion molding method,
Conventionally known methods such as injection molding can be used.

In this case, polyvinyl alcohol, polyvinylpyrrolidone, etc. can be used as the molding binder.
A dispersant such as stearate may be added if necessary.

In addition, for sintering, we use normal pressure sintering, atmospheric pressure sintering,
Hot press sintering or hot isostatic pressing (HIP)
Although conventional methods such as the above can be employed, in order to obtain silicon carbide with higher density and excellent conductivity, it is desirable to employ a pressure sintering method such as hot pressing. The sintering temperature is not particularly limited either, but heating temperatures lower than 1800°C will result in insufficient sintering, and heating temperatures higher than 2400°C will easily cause evaporation of silicon carbide (which may result in sintering due to particle growth). Since there is a possibility that the strength and toughness of the compact may decrease, it is preferable to sinter at a temperature range of 1800°C to 2400°C.

Further, as the atmosphere during sintering, any of a vacuum atmosphere, an inert atmosphere, or a reducing gas atmosphere can be adopted.

The seal material made of the silicon carbide sintered body obtained in this way has not only characteristics such as corrosion resistance and high strength, but also conductivity with an electrical resistance value of 1Ω・cl or less, regardless of the raw material powder. Therefore, electrical discharge machining as described later becomes possible. In addition, this stamp material has a sintered density of 3-Og/cgi" and a three-point bending strength of 50.0
kg/as” or more.

Next, the stamp material is cut into a cylindrical shape, and further ground and polished to form a stamp shape.

Thereafter, one end surface that will become the stamped portion is subjected to electric discharge machining using an electrode that has been previously matched to the stamped shape, thereby forming the stamped portion 2 shown in FIG. 1.

In the stamp 1 obtained in this way, the material itself made of silicon carbide sintered body has high corrosion resistance and high strength, and has low electrical conductivity with an electrical resistance value of 19・ell or less. The stamp portion 2 can be processed by electrical discharge machining. Since the stamping part 2 can be machined by electric discharge machining in this way, the occurrence of chipping during machining is suppressed, and precise machining of details is facilitated, so that the shape and size of letters etc. on the stamping part 2 can be improved. Increases accuracy.

In addition, since the average particle diameter of the second silicon carbide powder used as the raw material powder is extremely small at 0.1 μm or less, the strength of the sintered body obtained from it is not impaired (there are fine bores in the grain boundaries). Therefore, the stamp 1 obtained from this sintered body has good wettability to vermilion.

Furthermore, the silicon carbide sintered body that is the material of the seal 1 has a sintered density of 3.0 g/am' or more and a three-point bending strength of 50.0 kg/-1! Because of the above, it is less likely to be damaged due to unforeseen accidents such as falling compared to conventional ones.

"Example" Hereinafter, the present invention will be explained in more detail with reference to Examples.

(Example 1) The first silicon carbide powder has an average particle diameter of 1.1 μs, B
A β-type silicon carbide powder with an ET specific surface area of 1.7 m'' and 7 g was used.Next, silicon tetrachloride and nyletine were added to this first silicon carbide powder by vapor phase synthesis using a plasma CVD method as raw material gases. Average particle size: 0.01 μm, specific surface area: 96
7 g of amorphous silicon carbide ultrafine powder (second silicon carbide powder) was added in an amount of 5% by weight, which was dispersed in methanol and further mixed for 12 hours using a ball mill.

Next, this mixture was dried to obtain a dry mixture of 1500
A graphite mold with an inner diameter of 210 m was filled with 4 g of
90 at a sintering temperature of 2200°C.
Sintering was performed for a minute to obtain a disk-shaped sintered body with a diameter of 210 am and a thickness of 14 mm.

The obtained silicon carbide sintered body was examined for its sintered body density, three-point bending strength at room temperature, and specific resistance value at room temperature, and the results are shown in Table 1.

In addition, regarding 3-point bending strength, JIS R-16
01, and the resistance value was measured using the four-terminal method.

Next, a diameter of 10.511I1 was made from this silicon carbide sintered body.
15 A cylindrical body having a length of 60 mm was cut out, and this was further polished using a barrel polisher.

After that, set the polished material in the electrical discharge machine,
Electric discharge machining was performed on one end surface of the material, which would become the stamp part, using a copper electrode which had been previously adapted to correspond to the stamp shape, thereby forming the stamp part and completing the stamp.

(Example 2) Same silicon carbide powder as Example 1 (first silicon carbide powder)
Plasma C using monosilane and methane as raw material gases
Average particle diameter 0.02. synthesized in vapor phase by VD method. IZI
, 15% by weight of β-type ultrafine silicon carbide powder (second silicon carbide powder) with a BET specific surface area value of 70 m+”/g was added, and sintered under the same conditions as in Example 1 to obtain a silicon carbide sintered body. Manufactured.

The sintered body density, three-point bending strength at room temperature, and electrical resistance value of the obtained silicon carbide sintered body were examined in the same manner as in Example 1, and the results are also listed in Table 1.

Further, a seal was produced from this sintered body in the same manner as in Example 1.

(Example 3) Plasma CVD using monosilane and methane as raw material gases
Average particle size 0.02 μm synthesized in vapor phase by method, BET
Ultrafine β-type silicon carbide powder with a specific surface area value of 70 m''/g was dispersed in methanol, further mixed in a ball mill for 12 hours, and the resulting mixture was sintered under the same conditions as in Example 1 to obtain silicon carbide. A sintered body was obtained.

The sintered body density, three-point bending strength at room temperature, and electrical resistance value of the obtained silicon carbide sintered body were examined in the same manner as in Example 1, and the results are also listed in Table 1.

(Experimental Example) The following tests were conducted using the seals prepared in Examples 1 to 3, a conventional ivory seal, and a ceramic seal prepared according to a conventional method.

(2) Regarding the wettability to vermilion ink, the stamps of Examples 1 to 3, ivory stamps, and ceramic stamps were each coated with vermilion once and then stamped five times in a row.

As a result, for the seals of Examples 1 to 3 and the ivory seals, clear impressions were obtained all five times, and for the ceramic seals, the characters in the seal impression started to fade after about the third time, and by the fifth time, the characters were It became difficult to decipher. From the above results, the seals of Examples 1 to 3 and the ivory seals are as follows:
It was confirmed that the seal had sufficient wettability to vermilion, and was superior in wettability compared to ceramic seals.

■About the edges of characters Seals, ivory seals, and ceramics of Examples 1 to 3.

Each stamp made of wax was cut in half as shown in FIG. 2, and the edge portion 3 of the cross section of the character in the stamp portion 2 shown in FIG. 3 was observed using a microscope.

As a result, the stamps of Examples 1 to 3 had sharper edges and edges 3 than the ivory stamps and the ceramic stamps, and no difference was observed in the stamps of Examples 1 to 3. .

■About the outline of characters Seals, ivory seals, and ceramics of Examples 1 to 3.

The outlines of the characters in the stamped parts of the Kusu seals were observed using a microscope.

As a result, it was confirmed that the seals of Examples 1 to 3 had smoother and clearer character outlines than the other two types of seals.

■ Concerning the chipping of the printed part during processing Ten stamps of Examples 1 to 3 were each produced using the manufacturing method shown in the example, and 10 ceramic stamps were produced using the conventional method. The processing yield was compared.

As a result, the yield of the stamps of Examples 1 to 3 was 10
0%, but for ceramic seals made by the conventional method, it was 80%.

(2) Heat resistance The stamps of Examples 1 to 3 and the ivory stamps were heated at 1000° C. for 30 hours in an oxidizing atmosphere.

As a result, no damage was observed in any of the seals of Examples 1 to 3, but deformation occurred in the ivory seals, and the ivory seals could not be reused.

From the above results, it was confirmed that the seal of the present invention has properties equivalent to or better than the ivory seal and the conventional ceramic seal in all respects.

Furthermore, as shown in Example 2, even if a sintered body is produced using ultrafine silicon carbide powder (second silicon carbide powder) synthesized from different raw material gases, ultrafine silicon carbide powder is further added. It was confirmed that the obtained seal had excellent properties even when the amount was changed.

In addition, as shown in Fruit/Zettai 3, ultrafine silicon carbide powder (
It was confirmed that even when a sintered body was produced using only the second silicon carbide powder, the obtained seal still had excellent properties.

"Effects of the Invention" As explained above, the seal stamp according to claim 1 of the present invention provides the following excellent effects.

■Since the material of the seal is silicon carbide sintered body, it has a surface luster unique to silicon carbide sintered body, and has excellent strength, heat resistance, and corrosion resistance, so it will not be burnt out or deformed due to fire etc. No discoloration or deformation caused by chemicals, damage caused by insect bite, etc. (durability will be compromised).

■The density of the silicon carbide sintered body that is the material for the seal is 3.0~
3.2 g/cm', which is lighter than conventional Nyorceraminox materials, so it does not feel strange when used compared to conventional seals made of natural materials.

■Since the material for seals is silicon carbide sinter, the raw material is abundant and can be manufactured artificially from now on, making it possible to protect the valuable natural resources that were traditionally used as raw materials for seals. can.

Moreover, according to the seal manufacturing method of the invention described in claims 2 and 3, the following excellent effects are achieved.

■By using a second silicon carbide powder with an average particle size of 0.1μ or less and excellent sinterability as a raw material powder,
The silicon carbide sintered body that is the material for the seal has a fine microstructure with microscopic bores, and the resulting seal has better wettability of the vermillion ink than other dense ceramic stamps.
The outline of characters on the seal impression becomes clearer.

■By using a second silicon carbide powder with an average particle size of 0.1 μm or less and excellent sinterability as a raw material powder,
The silicon carbide sintered body that is the material for the seal is extremely dense, and the resulting seal has high strength and is less likely to be damaged by falling, etc., than conventional seals made from natural resources.

(2) By providing a stamp part after forming the material by sintering, even if the stamp part is damaged, the seal can be regenerated by providing a new stamp part.

Furthermore, according to the method for manufacturing a seal stamp according to claim 4, the following excellent effects are achieved.

(2) Since the stamp part is formed by electric discharge machining, the occurrence of chips during machining is suppressed, and detailed machining becomes easier, improving the accuracy of character shapes, etc.

■Since the stamp part is formed by electrical discharge machining, the edges of the finished letters, etc. will be very sharp, and the outline of the resulting seal impression will be very clear.

■Since the stamp part is formed by electrical discharge machining, the characters, etc. on the stamp part can be finished to the dimensions and shape specified by the manufacturer, making it possible to form a beautiful and precise stamp part.

[Brief explanation of drawings]

1 to 3 are views relating to the seal stamp of the present invention and its manufacturing method, in which FIG. 1 is a perspective view showing an example of the seal stamp according to claim 1, and FIG. 2 is a diagram showing the manufacturing method of the present invention. FIG. 3 is an enlarged view of the main part of FIG. 2. 1...Seal stamp, 2...Seal impression part, 3...
・・・Edge part of character cross section.

Claims (4)

[Claims] (1) Sintered without the addition of sintering aids, the sintered body density is 3.0 g/cm^3 or more, and the electrical resistance value at room temperature is 1 Ω.
cm or less, and the three-point bending strength at room temperature is 50.0 kg.
A seal made of sintered silicon carbide with a diameter of /mm^2 or more. (2) A silane compound is added to the first silicon carbide powder having an average particle size of 0.1 to 10 μm in a plasma in a non-oxidizing atmosphere,
Or particles with an average particle diameter of 0.1 μm or less synthesized by introducing a raw material gas consisting of silicon halide and hydrocarbon and performing a gas phase reaction while controlling the pressure of the reaction system in the range of less than 1 atmosphere to 0.1 torr. 0 second silicon carbide powder
．． A method for manufacturing a seal, which comprises mixing 5% by weight or more, heating and sintering the mixture to obtain a silicon carbide sintered body, and forming a seal by providing a stamp part on this sintered body. (3) Introducing a silane compound or a raw material gas consisting of silicon halide and hydrocarbon into plasma in a non-oxidizing atmosphere, and performing a gas phase reaction while controlling the pressure of the reaction system in the range of less than 1 atmosphere to 0.1 torr. A silicon carbide sintered body is obtained by heating and sintering silicon carbide powder with an average particle diameter of 0.1 μm or less synthesized by this process, and a stamp part is provided on this sintered body to make a seal. Characteristic seal manufacturing method. (4) In the method for manufacturing a seal according to claim 2 or 3,
A method for producing a seal stamp, characterized in that a stamp portion is engraved by electrical discharge machining on a stamp surface of a stamp material obtained from the sintered body.