JPH033086B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a friction disk, and more particularly to a brake disk or the like that controls the rotation of wheels of vehicles, automobiles, airplanes, etc. by means of sliding friction.

(Prior technology) Brake discs for vehicles, automobiles, aircraft, etc. have traditionally been made of cast iron, asbestos, or cast iron with graphite added to provide wear resistance and stabilize friction performance. Recently, due to the adverse effects of asbestos powder on the human body and the environment, brake discs made of carbon-bonded carbon fiber composite materials, so-called C/C composites, have come into use.

C/C composites are carbon fibers reinforced in one direction by filament winding, etc.
There are fabrics woven from carbon fiber, fabrics reinforced in two directions by layering nonwoven fabrics, and fabrics reinforced in multiple directions by weaving in multiple directions.These C/C composites have a high mechanical strength. Because it is large and has excellent heat resistance and thermal conductivity, it is possible to rapidly dissipate frictional heat, and its high strength prevents seizure, corrosion, and rust, making it suitable for high-speed objects such as aircraft and Used in brake discs for special vehicles and automobiles.

(Problems to be Solved by the Invention) However, in terms of strength, the friction disk, which is a brake disk made of a conventional C/C composite, has no problem in terms of strength in the reinforced direction, but the wear resistance of the sliding surface was insufficient.

Furthermore, the frictional heat at high speeds may partially reach a temperature higher than the temperature at which the oxidation reaction of the carbon fibers starts, resulting in oxidative consumption and rapid strength deterioration.

The object of the present invention is to solve these problems and provide a friction disk that has high strength and excellent wear resistance and oxidation resistance.

(Means for Solving the Problems) That is, the gist of the present invention is a friction disk made of a C/C composite, a part or all of which is converted to silicon carbide.

C/C composites are one-dimensional, using carbon fibers made from synthetic polymer materials such as polyacrylonitrile, rayon, and phenolic resins, or carbon fibers made from petroleum pits, coal pits, etc. as starting materials.
They can be assembled into two-dimensional, three-dimensional, or even higher-dimensional structures.

Next, these structures are impregnated with a carbonizable resin such as a phenol resin or a furan resin, or impregnated with pitch, and after hardening, are fired and carbonized at a temperature of 700°C or higher. In order to obtain a denser and higher strength C/C composite in this step, it is necessary to repeat the resin impregnation-hardening-carbonization process several times.

Furthermore, instead of resin impregnation, pyrolytic carbon may be uniformly deposited within the carbon fiber structure by CVD treatment.

Part or all of the friction disk made of the C/C composite formed in this way is made of silicon carbide,
Methods for converting into β-type silicon carbide, which has particularly excellent wear resistance, include a conversion method in which it is reacted with silicon vapor or various silicon compounds, and a method in which it is treated with the same filler as the gas generation source in the conversion method. There is a method using back cementation, which involves embedding objects and heating them. The most preferred method is a conversion method in which silicon monoxide gas and a friction disk are reacted as shown in the following equation, thereby maintaining the shape of the friction disk.

SiO(g)+2C=SiO+CO(g) This reaction proceeds by heating in the temperature range of 1300°C to 2300°C. Here, in order to generate silicon monoxide gas, a mixture of silicon powder and silicon dioxide powder, a mixture of silicon carbide powder and silicon dioxide powder, or a mixture of carbon powder and silicon dioxide powder, etc. can be used as the gas generation source. This can be done by heating various silicon compounds to 1200°C to 2300°C.

To convert part or all of the friction disk into silicon carbide, place it in the same graphite container so as not to come into contact with the source of silicon monoxide gas, and transfer silicon monoxide from the source of silicon monoxide gas to the surface of the friction disk. Gas is introduced and silicon monoxide gas is diffused through the fine pores of the friction disk to cause a silicification reaction.

In order to convert only the desired portion of the friction disk into a silicon carbide layer, this can be done by masking the non-desired portion with a graphite plate or the like to cut off contact with silicon monoxide gas. .

When the friction disk and silicon monoxide are reacted to convert the friction disk surface layer into silicon carbide, by selecting a treatment temperature in the range of 1300°C to 2300°C, the silicified layer of the friction disk surface layer is converted. By leaving unreacted carbon, it is possible to produce products with various silicification ratios, which are the proportions of silicon carbide, depending on the application. Further, the thickness of the silicified layer on the friction disk surface can be controlled by adjusting the treatment time as well as the treatment temperature. The thickness of the silicified layer is preferably 0.1 mm to 3.5 mm. In addition, the silicification rate and the thickness of the silicide layer can be controlled by adjusting the concentration of silicon monoxide.

In addition to the above methods, the carbon fibers constituting the C/C composite are converted into silicon carbide by converting a part or all of the fiber surface layer into silicon carbide using the above method, and this carbon fiber is used to form a silicon carbide. Knitted into a C/C composite of 3D, 2D, 3D, or higher dimensions and resin impregnated - hardened - carbonized or CVD
Friction discs can also be obtained through processing steps.

It is desirable that at least 10% or more of unreacted carbon remains in the silicified layer obtained by converting the surface layer of the friction disk into silicon carbide. This is because the heat conductivity inherent to the carbon component is added to the wear resistance imparting effect inherent to the silicon carbide component, thereby ensuring a long service life.

(Function of the Invention) The present invention is characterized in that silicon monoxide gas permeates and diffuses through the surface layer of the friction disk made of a C/C composite, reacts with the friction disk itself, and converts into silicon carbide. It is fundamentally different from the CVD method, PVD method, or methods such as plating, thermal spraying, and coating to deposit various substances onto carbon fiber.

In other words, CVD method, PVD method, or metsuki,
Carbon fiber surfaces obtained by thermal spraying, coating, etc. are bonded to various deposited coating materials and the carbon fiber surface only by physical adhesion due to Van der Waals forces, etc. When a /C composite friction disk is used, repeated use under high temperature and pressure causes the deposited coating material to peel off due to differences in thermal expansion and shear stress, resulting in poor wear resistance and
Premature loss of oxidation resistance.

However, the surface layer of the friction disk of the present invention is mainly composed of silicon carbide, which is the most stable material and has excellent oxidation resistance and wear resistance, and is not chemically corroded.The surface layer of the friction disk itself reacts with silicon monoxide. Since the silicon carbide is converted into silicon carbide, the boundary has a completely continuous structure, and the silicified layer does not peel off even after repeated use under high temperature and pressure, making it oxidation resistant and resistant for a long time. Ensure wear resistance.

Next, the present invention will be specifically explained using examples.

(Example) Example 1 After overlapping carbon fiber knitted cloth and impregnating it with phenol resin, it was heated to 150% using a hot press.
The molded product was cured under a pressure of Kg/cm ² to obtain a molded product having a diameter of 250 mmΦ and a thickness of 15 mm. This was fired and carbonized at 900°C to obtain a friction disk made of a C/C composite.

Here, the obtained friction disk was further impregnated with phenolic resin and fired and carbonized four times, and the density was 1.58.
g/cm ³ , bending strength 1150Kg/cm ² AG, elastic modulus 1300
A friction disk of Kg/mm ² was fabricated.

This friction disk was placed in the same graphite container and sealed to avoid contact with 1.5 kg of a mixed molded product of silicon powder and silicon dioxide powder (molar ratio 1:1), heated at 1800°C, and kept at this temperature for 90 minutes. , the surface layer was converted to silicon carbide.

As a result of this treatment, as shown in the cross-sectional view of Figure 1, the surface layer of the C/C composite 3 has a layer 2 with a thickness of about 2.6 mm that has been converted into β-type silicon carbide containing unreacted carbon. Friction disk 1 was produced.

As shown in the schematic diagram of FIG. 2, the layer 2 converted to silicon carbide is composed of carbon fibers consisting of a portion 5 added to silicon carbide and an unreacted carbon portion 6 at a thickness of approximately 2.6 mm from the surface, and a layer 2 of silicon carbide. It consists of a carbon matrix consisting of converted portions 7 and unreacted carbon 8.

The friction disk made of a C/C composite obtained by converting the surface layer into silicon carbide as above has a density of 1.61 g/cm ³ , a bending strength of 1820 Kg/cm ² , and an elastic modulus.
It became 1910Kg/mm ² .

This friction disk was placed in an air atmosphere at 600°C and the oxidative wear rate was measured after 100 hours. The result was approximately 1/15 of the oxidative wear rate of a conventional friction disk whose surface layer was not converted to silicon carbide. Ta.

In addition, the wear rate of this friction disk was measured by contacting it with a rotating body made of stainless steel at a pressure of 588N, and the wear rate was approximately 1/3 that of a conventional friction disk whose surface layer was not converted to silicon carbide. It was hot.

Example 2 As shown in Fig. 3, a two-dimensional cloth was prepared using carbon fibers having a layer 5 whose surface layer was converted to β-type silicon carbide, which were overlapped and impregnated with phenolic resin. After that, use a hot press to produce 150Kg/
Cured under pressure of cm ² , diameter 250mmΦ, thickness 15
A molded body of mm was obtained. This was fired and carbonized at 900°C to produce a friction disk made of a C/C composite.
This friction disk was further impregnated with phenolic resin and carbonized four times to obtain a friction disk having a density of 1.59 g/cm ³ , a bending strength of 1470 Kg/cm ² AG and a modulus of elasticity of 1490 Kg/mm ² .

This friction disk was placed in an air atmosphere at 600° C., and the oxidative wear rate after 100 hours was measured. As a result, the oxidative wear rate was about 1/20 of that of a conventional friction disk that had not been converted to silicon carbide.

Furthermore, the wear rate of this friction disk was measured by contacting it with a rotating body made of stainless steel at a pressure of 588N, and the wear rate was approximately 1/2 that of a conventional friction disk that had not been converted to silicon carbide.

Example 3 In the same manner as in Example 1, carbon fiber knitted cloth was overlapped and impregnated with phenolic resin, and then cured under pressure of 150 kg/cm ² using a hot press.
A molded body with a diameter of 250 mmΦ and a thickness of 15 mm was obtained. this
A friction disk made of a C/C composite that was fired and carbonized at 900°C was obtained.

Here, the obtained friction disk was further impregnated with phenolic resin and fired and carbonized four times to achieve a density of 1.58.
g/cm ³ , bending strength 1080Kg/cm ² AG , elastic modulus 1300
A friction disk of Kg/mm ² was fabricated.

This friction disk was filled into a graphite container with 1 kg of a mixed powder of carbon powder and silicon dioxide powder (molar ratio 3:1), heated at 1800°C, and held at this temperature for 1 hour.

As a result of this treatment, a wear disk made of a C/C composite whose surface layer was converted to β-type silicon carbide was obtained.

This friction disk was placed in an air atmosphere at 600°C and the oxidative wear rate was measured after 100 hours. The oxidative wear rate was approximately 1/12 of that of a conventional friction disk whose surface layer was not converted to silicon carbide. Ta. In addition, the wear rate of this friction disk was measured by contacting it with a rotating body made of stainless steel at a pressure of 588N, and the wear rate was approximately 1/3 that of a conventional friction disk whose surface layer was not converted to silicon carbide. It was hot.

(Effects of the Invention) As explained above, the friction disk of the present invention has a part or all of it converted to silicon carbide, so it can be heated to 500°C, the temperature at which carbon fibers start an oxidation reaction due to frictional heat. Even if the temperature exceeds the oxidation consumption, the silicon carbide surface layer suppresses oxidative wear
It can be used with confidence as it does not cause rapid strength deterioration.

Furthermore, the friction disk of the present invention has a wear-resistant heat property due to the silicon carbide surface layer, which has a wear-resistant effect inherent to silicon carbide, and the thermal conductivity and heat dissipation properties of carbon fiber. To provide a friction disk with excellent dissipation properties.

Furthermore, since the friction disk of the present invention has a friction disk structure made of carbon fiber reinforced with silicon carbide, it is better than conventional friction disks that have mechanical strength due to a knitted structure of carbon fibers. , high strength and high elasticity can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a friction disk according to the present invention;
FIG. 2 is a schematic enlarged view of section A in FIG. 1, and FIG. 3 is a cross-sectional view of the carbon fiber before and after silicification. Explanation of symbols, 1... Friction disk, 2... Layer converted to silicon carbide containing unreacted carbon, 3...
C/C composite, 4... carbon fiber, 5... portion of carbon fiber converted to silicon carbide, 6... unreacted carbon portion of carbon fiber, 7... portion of carbon matrix converted to silicon carbide, 8 ...Unreacted carbon part of the carbon matrix.

Claims (1)

[Claims] 1. A friction disk made of a C/C composite, part or all of which is converted to silicon carbide.