JP4309371B2 - High-strength silicon carbide sintered material used as a constituent material for sealing rings of mechanical seals - Google Patents

Description

The present invention relates to a silicon carbide sintered material having excellent mechanical strength such as bending strength, it relates to high-strength sintered silicon carbide material used as a constituent material of the seal ring of the mechanical seal.

  Since silicon carbide is hard and has excellent wear resistance, and has excellent heat resistance, corrosion resistance, chemical resistance, etc., its sintered material (silicon carbide sintered material) is sealed with a mechanical seal. It is used as a component for heat and corrosion resistant members such as rings, bearings and other sliding members, as well as burner nozzles and crucibles.

  However, since silicon carbide sintered materials are not generally superior in mechanical strength such as bending strength, they are satisfactory as constituent materials for members that require high strength, such as sliding members with a large mechanical load. It was not possible.

  Therefore, conventionally, in order to improve the strength of the silicon carbide sintered material, it has been attempted to make it composite with ceramic fibers such as carbon fibers (for example, Patent Document 1).

Japanese Patent Laid-Open No. 4-305063

  However, in such a fiber-reinforced silicon carbide sintered material, even if the mechanical strength can be improved to some extent, the original characteristics (heat resistance, corrosion resistance, etc.) of silicon carbide are impaired by the composite with the fibers. There was a fear.

The present invention has been made in view of the above points, and is a silicon carbide sintered material used as a constituent material of a sealing ring of a mechanical seal , and mechanical strength such as bending strength without impairing the original characteristics of silicon carbide. Hisage high strength sintered silicon carbide material that can significantly improve Kyosu it is an object of Rukoto.

In order to achieve the above object, the present invention comprises forming and firing a silicon carbide sintered raw material to which a predetermined amount of carbon material by-produced in the fullerene production process (hereinafter referred to as “by-product carbon material”) is added. The high strength silicon carbide used as a constituent material of the sealing ring of the mechanical seal , wherein the by-product carbon material functions as a sintering aid during firing to improve mechanical strength A sintered material is proposed.

The by-product carbon material, C strongest peak in the range of diffraction angle 3 to 30 ° in uKα line X-ray diffraction measurement results using exists in the range of diffraction angle 10 to 18 ° and a diffraction angle 23-27 There is no peak at °, and in the Raman spectrum result at an excitation wavelength of 5145 有 し, there are peaks in band G1590 ± 20 cm ⁻¹ and band D1340 ± 40 cm ⁻¹ , and the peak intensities of the respective bands are represented by I (G) and I A carbon material having a peak intensity ratio I (D) / I (G) of 0.4 to 1.0 when (D) is used . In concrete terms, Frontier Carbon Co., Ltd. "Nano-time black FB", "Nano-time black FB-X" or the like is preferred. In addition, it is also possible to use what added two or more types of mixtures selected from the above-mentioned byproduct carbon material as a silicon carbide sintering raw material.

In the preferred embodiment, the silicon carbide sintered material was added at a rate of 0.01 to 5 parts of by-product carbon material to the silicon carbide powder 100 parts is used. As the silicon carbide powder, α-type, β-type, or amorphous silicon carbide or a mixture thereof can be used, but those having an average particle size of 1 μm or less are preferably used.

Thus, by using the silicon carbide sintered raw material to which the by- product carbon material is added, the growth of columnar crystals of silicon carbide during firing is suppressed, and as a result, crystal grains become finer, A dense silicon carbide sintered material with few defects is obtained. In addition , the addition of by-product carbon material suppresses segregation of carbon or the like to the silicon carbide crystal grain boundary, thereby reducing the number of defective sintering due to cleaning of the crystal grain boundary and heterogeneous aggregation of carbon or the like. Reduction in strength due to field destruction is suppressed. Such refinement of crystal grains, cleaning of crystal grain boundaries, and reduction in the number of defective sintering points greatly improve the strength such as bending strength. By the way , the by- product carbon material is considered to function as a sintering aid at the time of firing (during sintering) because it exhibits the effect of suppressing crystal growth as described above.

Moreover, the high-strength silicon carbide sintered material of the present invention is formed by granulating a silicon carbide sintered raw material to which the above-mentioned by-product carbon material is added, and a granulated material obtained by the granulating step. And a preforming step for obtaining a preform with a predetermined shape, and a firing step for firing the preform in an inert gas atmosphere to obtain a high-strength silicon carbide sintered material. to Ru obtained by the production method of the high strength silicon carbide sintered material. In the granulation step, adding a pre-Me-product carbon material each respective raw material components, it is granulated by mixing them, so as to granulate by mixing all the ingredients at once Or any. Furthermore , as long as the by- product carbon material can be uniformly mixed with other materials and the mixed material can be granulated , for example, the by-product carbon material is dissolved and dispersed in an appropriate solvent in advance. The grain process can be performed by any known method. For example, silicon carbide sintered with a by-product carbon material added at a ratio of 0.01 to 5 parts with respect to 100 parts of silicon carbide powder. The raw material is mixed and stirred with an appropriate solvent such as alcohol and water, and the mixed slurry is granulated with a spray dryer to obtain a spherical granulated material (generally 20 to 100 μm in diameter). preferable. For firing (sintering), a known sintering method such as a hot press method (HP method), a room temperature sintering method (PLS method), a gas pressure sintering method or a hot isostatic pressing method may be employed. In general, however, the firing temperature is preferably 1900 to 2200 ° C. (more preferably 2100 to 2200 ° C.).

High strength silicon carbide sintered Yuizai the present invention has silicon carbide original characteristics (wear resistance, heat resistance, corrosion resistance, etc.) may significantly improve the mechanical strength of the flexural strength and the like without impairing the mechanical it is suitable to shall as a material of the seal ring of the seal.

According to the manufacturing method described above, the high-strength silicon carbide sintered material of the present invention in which mechanical strength such as bending strength is significantly improved while ensuring the original characteristics of silicon carbide can be easily obtained.

As a reference example , a high-strength silicon carbide sintered material (hereinafter referred to as “ reference example sintered material”) according to the present invention was obtained by the following granulation process, preforming process and firing process.

Granulation step: 200 g (100 parts) of silicon carbide powder (average particle size 0.6 μm or less), 1 g (0.5 part) of boron carbide (B ₄ C) powder and 16 g (8.0) as a sintering aid. Part) phenolic resin (carbon source), 8 g (4.0 parts) of wax as a molding aid, and 2 g (1.0 part) of fullerenes A1 are added. Was mixed and stirred for 3-4 days with a ball mill together with 320 g (160 parts) of a methanol solvent, and the mixed slurry was granulated by spray drying with a spray dryer to form a spherical shape having a diameter of 50 to 100 μm. A granulated material (granule) was obtained. As the fullerenes A1, “Nanomumix” manufactured by Frontier Carbon Co., Ltd. was used. This is a fullerene mixture composed of fullerene C ₆₀ : about 60%, fullerene C ₇₀ : about 25%, and other higher-order fullerenes: the balance.

Preliminary molding step: The granulated material obtained in the granulation step was filled in a mold, and then cold press-molded at 1000 to 2000 kg / cm ² to obtain a preform with a predetermined shape.

Firing step: The pre-formed body obtained in the pre-forming step was fired (sintered) at 2100 ° C in an inert gas (argon gas) atmosphere without applying pressure to obtain a reference example sintered material.

As Example 1 , a high-strength silicon carbide sintered material (hereinafter referred to as “ first example sintered material”) according to the present invention was obtained by the following granulation process, preforming process and firing process. In addition, the preforming process and baking process in Example 1 are the same as a reference example , and the granulation process is the same as a reference example except having replaced with fullerenes and adding the byproduct carbon material.

Granulation step: 200 g (100 parts) of silicon carbide powder (average particle size 0.6 μm or less), 1 g (0.5 parts) of B ₄ C powder, 16 g (8.0 parts) of phenol resin and 8 g (4 0.0 part) molding aid and 2 g (1.0 part) by-product carbon material A2 are added to a silicon carbide sintered raw material together with 320 g (160 parts) methanol solvent by a ball mill for 3 to 4 days. The mixed slurry was granulated by spray-drying the mixed slurry with a spray dryer to obtain a spherical granulated material having a diameter of 50 to 100 μm. As the by-product carbon material A2, “Nanome Black FB” manufactured by Frontier Carbon Co., Ltd. was used. This is obtained by separating and purifying the fullerene-containing soot, and the X-ray diffraction measurement result using CuKα rays shows the strongest peak within the diffraction angle range of 3 to 30 ° and the diffraction angle of 10 to 18 °. In the Raman spectrum result at an excitation wavelength of 5145 し having a peak in a band G1590 ± 20 cm ⁻¹ and a band D1340 ± 40 cm ⁻¹ in the range and having no diffraction peak at a diffraction angle of 23 to 27 °, each band Carbon material whose peak intensity ratio I (D) / I (G) is 0.4 to 1.0 when the peak intensity of I is G (I) and I (D) (see Japanese Patent Application No. 2004-91312) It is.

Preliminary molding step: Using the granulated material obtained in the granulation step, a preform was obtained by the same preliminary molding step as in the reference example .

Baking step: a preliminary molding step is obtained preform was fired in Reference Example in the same firing step, to obtain a first embodiment sintered material that forms the reference example and the same shape.

As Example 2 , a high-strength silicon carbide sintered material (hereinafter referred to as “ second example sintered material”) according to the present invention was obtained by the following granulation process, preforming process and firing process. In addition, the preforming process and baking process in Example 2 are the same as those in Reference Example and Example 1 , and the granulation process is the same as Example 1 except that the by-product carbon material to be added is different.

Granulation step: 200 g (100 parts) of silicon carbide powder (average particle size 0.6 μm or less), 1 g (0.5 parts) of B ₄ C powder, 16 g (8.0 parts) of phenol resin and 8 g (4 0.0 part) forming aid and 2 g (1.0 part) by-product carbon material A3 were added to a silicon carbide sintered raw material for 3 to 4 days by a ball mill together with 320 g (160 parts) of a methanol solvent. The mixed slurry was granulated by spray-drying the mixed slurry with a spray dryer to obtain a spherical granulated material having a diameter of 50 to 100 μm. As the by-product carbon material A3, “Nano Black FB-X” manufactured by Frontier Carbon Co., Ltd. was used. This is a surface-treated product of the by-product carbon raw material A2 (nano black FB) having a powder PH of about 3.

Preliminary forming step: Using the granulated material obtained in the granulating step, a preformed body was obtained by the same pre-forming step as in Reference Example and Example 1 .

Baking step: a preliminary molding step is obtained preform was fired by reference examples and the same firing process as in Example 1, to obtain a second embodiment sintered material constituting the Reference Examples and Examples 1 and same shape It was.

Further, as a comparative example, a silicon carbide sintered material (hereinafter referred to as “comparative example sintered material”) was obtained by the following granulation step, pre-forming step, and firing step. In addition, the preforming process and the firing process in the comparative example are the same as the reference example and Examples 1 and 2 , and the granulation process is a reference except that the fullerenes and the by-product carbon material are not added to the silicon carbide sintered raw material. The same as Example and Examples 1 and 2 .

Granulation step: 200 g (100 parts) of silicon carbide powder (average particle size 0.6 μm or less), 1 g (0.5 parts) of B ₄ C powder, 16 g (8.0 parts) of phenol resin and 8 g (4 0.0 parts) and a molding aid are mixed and stirred with a ball mill for 3 to 4 days together with 320 g (160 parts) of methanol solvent, and the mixed slurry is spray-dried with a spray dryer. To obtain a spherical granulated material having a diameter of 50 to 100 μm.

Preliminary forming step: Using the granulated material obtained in the granulating step, a preformed body was obtained by the same pre-forming step as in the reference example and Examples 1 and 2 .

Baking step: a preliminary molding step is obtained preform was fired by Reference Examples and Examples 1, 2 and the same firing step, Reference Examples and Examples 1, 2 and Comparative Example sintered material forming the same shape Got.

Thus, when the sintered density of each sintered material was measured, as shown in Table 1 , the sintered materials of the first and second examples, the reference example sintered material and the comparative example sintered material were sintered. The consolidation density was approximately the same at about 3.16 g / cm ³ (relative density: about 98.8%), and it was confirmed that the sintered density was not lowered by the addition of fullerenes or by-product carbon materials.

On the other hand, when the bending strength and hardness of each sintered material were measured, the sintered materials of the first and second examples and the reference example sintered material added with fullerenes or by-product carbon materials were fullerenes and by-product carbon materials. Significant improvement was observed compared to the comparative sintered material without addition of. That is, a specimen is collected from each sintered material by grinding and lapping, and each specimen is subjected to bending strength (three-point bending strength) by a three-point bending test method according to JIS-R1601 at room temperature (25 ° C.). ) Was measured. The results are shown in Table 1. The sintered materials of the first and second examples and the sintered material of the reference example in which fullerenes or by-product carbon materials are added to the silicon carbide sintering raw materials are the fullerenes and by-products. It was confirmed that the bending strength was significantly improved as compared with the comparative sintered material to which no carbon material was added. The degree of improvement differs depending on the type of additive material, and the bending strength value of the first example sintered material to which the by-product carbon material A2 (“Nanome Black FB” manufactured by Frontier Carbon Co., Ltd.) is added is the highest. This was followed by the second example sintered material to which the raw carbon material A3 (“Nanome Black FB-X” manufactured by Frontier Carbon Co., Ltd.) was added, followed by fullerenes A1 (“Nanomu Mix” manufactured by Frontier Carbon Co., Ltd.). reference example ware Yuizai with added), although is observed significant bending strength improvement compared with the comparative example sintered material, first, second embodiment sintered with the addition of by-product carbon material A2, A3 The bending strength value was lower than that of the material .

Moreover, when the hardness (micro Vickers hardness) was measured by the micro Vickers hardness test (JIS-Z2244) about the test piece extract | collected from each sintered material, the result is as showing in Table 1, and a silicon carbide sintered raw material The sintered materials of the first and second examples and the reference example sintered material to which fullerenes or by-product carbon materials are added are higher than the comparative example sintered materials to which fullerenes and by-product carbon materials are not added. It was confirmed to show a hardness value. The hardness value varies depending on the type of additive material, and the sintered materials of the first and second examples to which the by-product carbon materials A2 and A3 are added show higher values than the reference example sintered material to which the fullerenes A1 are added. It was.

As described above, the sintered materials of the first and second examples showed higher values than the reference example sintered material and the comparative example sintered material in both bending strength and hardness. The added sintered material of Example 1 showed the highest value in both bending strength and hardness. Therefore, in order to improve the strength, it is understood that the by-product carbon material is preferable as the additive material, and in particular, the by-product material A2 (“Nanomu Black FB” manufactured by Frontier Carbon Co., Ltd.) is optimal. .

1 to 4 are photographs of crystal structures in which the etching surfaces of the sintered materials of the first and second examples , the reference example sintered material, and the comparative example sintered material are magnified 500 times by a scanning electron microscope (SEM). However, the reference example sintered material (FIG. 1), the first example sintered material (FIG. 2), and the second example sintered material (FIG. 3) are all comparative example sintered materials (FIG. 4). It was confirmed that the crystal grains were made finer and the segregation to the crystal grain boundaries was small. Therefore, it is understood that the addition of fullerenes or by-product carbon raw material achieves improvement in strength of the silicon carbide sintered material by miniaturizing crystal grain growth and reducing segregation to grain boundaries.

Since the high-strength silicon carbide sintered material of the present invention is increased in strength without impairing the original characteristics of silicon carbide, it is preferably used as a constituent material for a seal ring of a mechanical seal that requires high strength. be able to.

It is a microscope picture which expands the surface of a reference example sintered material by 500 times. It is a microscope picture which expands and enlarges the surface of 1st Example sintered material 500 times. It is a microscope picture which expands and enlarges the surface of 2nd Example sintered material 500 times. It is a microscope picture which expands the surface of a comparative example sintered material by 500 times.

Claims (3)

It is a carbon material by-produced in the fullerene production process, and the strongest peak is present in the diffraction angle range of 10 to 18 ° within the diffraction angle range of 3 to 30 ° in the X-ray diffraction measurement result using CuKα rays. There is no peak at a diffraction angle of 23 to 27 °, and in the Raman spectrum result at an excitation wavelength of 5145 ピ ー ク, there are peaks in band G1590 ± 20 cm ⁻¹ and band D1340 ± 40 cm ⁻¹ , and the peak intensity of each band is represented by I A carbon material having a peak intensity ratio I (D) / I (G) of 0.4 to 1.0 when (G) and I (D) are used is 0.01 to 5 with respect to 100 parts of silicon carbide powder. molded parts silicon carbide sintered material was added at a rate of, firing will be, the carbon material is characterized by being configured as mechanical strength is improved by acting as a sintering aid during firing High strength sintered silicon carbide material used as a constituent material of the sealing ring of Kanikarushiru. Sintering density of 3.161, 3-point bending strength is 660 MPa, the micro-Vickers altitude characterized 30500MPa der Rukoto, used as a constituent material of the seal ring of the mechanical seal according to claim 1 High-strength silicon carbide sintered material. Sintering density of 3.164, 3-point bending strength is 630 MPa, the micro-Vickers altitude characterized 30500MPa der Rukoto, used as a constituent material of the seal ring of the mechanical seal according to claim 1 High-strength silicon carbide sintered material.