JPH0539478A - Frictional disc - Google Patents

Abstract

PURPOSE:To obtain a frictional disc of high mechanical strength, excellent in abrasion resistance and acid resistance, useful as a brake disc for vehicles, aircraft, etc., by converting at least part of a frictional disc consisting of a C/C composite to silicon carbide. CONSTITUTION:The objective product 1470-1820kg/cm<2>AG in flexural strength and 1490-1910kg/AG in elastic modulus, consisting of a C/C composite with part or the whole thereof converted to silicon carbide. For obtaining the present product, it is preferable that a frictional disc consisting of the C/C composite be reacted with silicon monoxide gas at 1300-2300 deg.C according to the reaction formula: SiO+2C=SiC+CO to convert the disc to beta-type silicon carbide. The original disc can be obtained, for example, by impregnating a structure comprising carbon fibers with phenolic resin followed by heating and curing, and then roasting at >=700 deg.C and carbonizing the resultant form.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a friction disc,
More specifically, it relates to a brake disc or the like that controls the rotation of the wheels of a vehicle, automobile, aircraft, etc. by means of sliding friction.

[0002]

2. Description of the Related Art Brake discs for vehicles, automobiles, aircrafts, etc. have conventionally been made of cast iron, asbestos, or cast iron with graphite added to impart wear resistance and stabilize friction performance. Recently, from the viewpoint of adverse effects of asbestos powder on the human body and the environment, a brake disk made of a so-called C / C composite made of a carbon-bonded carbon fiber composite material has come to be used.

A C / C composite is obtained by reinforcing carbon fibers in one direction by filament winding, a cloth knitted with carbon fibers, a non-woven fabric laid in two directions to be strengthened, or by knitting in multiple directions. Some of them are reinforced in multiple directions, and these C / C composites have greater mechanical strength than cast iron and are superior in heat resistance and thermal conductivity, so rapid dissipation of friction heat is possible. Since it has high strength and does not cause seizure, corrosion, or rust, it is used in high-speed products such as aircraft, and in some special vehicles and brake discs of automobiles.

[0004]

However, the friction disc, which is a conventional brake disc composed of a C / C composite, has no problem in the strengthened direction in terms of strength.
The strength in other directions and the wear resistance of the sliding surface were insufficient. In addition, the frictional heat at high speed may partially exceed the temperature at which the oxidation reaction of carbon fiber is started, and as a result,
Oxidation was consumed, and a sudden deterioration in strength was observed.

Since such deterioration in strength leads to damage such as deformation and cracking of the friction disc, it is required that the friction disc itself has high strength. The C / C composite generally has a higher mechanical strength and a bending strength of 1150 kg / cm.
² AG and elastic modulus (Young's modulus) of about 1300 kg / mm ² AG can be manufactured, but they are not sufficient to prevent damage of the friction disk due to deterioration of strength due to oxidation, etc. A high friction disc was desired.

An object of the present invention is to solve the above problems and to provide a friction disk having high strength and excellent abrasion resistance and oxidation resistance.

[0007]

[Means for Solving the Problems] That is, the present invention comprises a C / C composite part or all of which is converted into silicon carbide, and has a bending strength of 1470 kg / cm ² AG to 182.
0 kg / cm ² AG, elastic modulus 1490 kg / mm ² AG
The gist of the present invention is a friction disk having a weight of -1910 kg / mm ² AG.

Such a friction disc can be manufactured as follows. The C / C composite is one-dimensional or two-dimensional using carbon fibers starting from synthetic polymer materials such as polyacrylonitrile, rayon and phenol resin, or carbon fibers starting from petroleum pitch, coal pitch, etc. , Three-dimensional structures, or higher-dimensional structures.

Next, these structures are impregnated with a carbonizing resin such as phenol resin or furan resin or pitches, and after being hardened, they are baked and carbonized at 700 ° C. or higher. In this step, it is necessary to repeat the resin impregnation-curing-carbonization process several times in order to obtain a denser and stronger C / C composite.
In addition to the resin impregnation, the pyrolytic carbon may be uniformly deposited in the carbon fiber structure by the CVD process instead of the resin impregnation.

As a method of converting a part or all of the friction disk made of the C / C composite molded in this way into silicon carbide, particularly β-type silicon carbide having excellent wear resistance, silicon vapor or There are a conversion method of reacting with various silicon compounds, and a method of applying back cementation in which an object to be processed is embedded and heat-treated with the same filler as the gas generation source of the conversion method. The most preferable method is a conversion method in which the shape of the friction disk is maintained by reacting the silicon monoxide gas with the friction disk as shown in the following formula. SiO (g) + 2C = SiC + CO (g) This reaction proceeds by heating in the temperature range of 1300 ° C to 2300 ° C. Here, to generate silicon monoxide gas, a mixture of silicon powder and silicon dioxide powder, a mixture of silicon carbide powder and silicon dioxide powder, a mixture of carbon powder and silicon dioxide powder, or the like is used as a gas generation source. It can be performed by heating various silicon compounds to 1200 ° C to 2300 ° C.

In order to convert a part or all of the friction disk into silicon carbide, the friction disk is placed in the same graphite container so as not to come into contact with the silicon monoxide gas generation source, and the silicon monoxide gas generation source is transferred to the surface of the friction disk. The silicon monoxide gas is introduced to diffuse the silicon monoxide gas through the fine pores of the friction disk to cause the silicidation reaction.

In order to convert only a desired portion of the friction disk into a silicon carbide layer, a graphite plate or the like is applied to the portion other than the desired portion to mask it, and the contact with the silicon monoxide gas is cut off. it can.

When the friction disc and silicon monoxide are reacted to convert the friction disc surface layer into silicon carbide, C /
Since the carbon atoms of the carbon fibers composing the C composite and the silicon atoms of the silicon monoxide gas proceed by a one-to-one substitution reaction, the original carbon fiber structure (porosity) is maintained as it is. The boundary between silicon carbide and carbon in the carbon fiber obtained in this way after being converted into silicon carbide has a completely continuous structure, and the silicified layer does not peel off due to repeated use under high temperature and high pressure for a long time. Oxidation resistance and wear resistance can be secured throughout.

When the friction disc and silicon monoxide are reacted to convert the friction disc surface layer into silicon carbide, the silicified layer of the friction disc surface layer is selected by selecting the treatment temperature in the range of 1300 ° C to 2300 ° C. Unreacted carbon may be left inside and various silicidation ratios, which are the proportions of silicon carbide, can be prepared according to the application.
Further, the thickness of the silicified layer on the surface of the friction disk can be controlled by adjusting the treatment time as well as the treatment temperature. Thickness of silicified layer is 0.1mm-3.5mm
Is preferred. In addition, the silicidation rate and the thickness of the silicified layer can be controlled by adjusting the concentration of silicon monoxide.

In addition to the above-mentioned method, the carbon fiber itself constituting the C / C composite is converted into silicon carbide by using the above-mentioned method, and a part or all of the fiber surface layer is converted into silicon carbide. The friction disk can be obtained by knitting into a one-dimensional, two-dimensional, or three-dimensional or higher dimensional C / C composite, and the resin impregnation-curing-carbonization or CVD process.

It is desirable to leave at least 10% or more of unreacted carbon in the silicified layer obtained by converting the surface layer of the friction disk into silicon carbide. This is because the effect of imparting wear resistance specific to the silicon carbide component is added to the thermal conductivity specific to the carbon component, and a long service life is guaranteed.

[0017]

The present invention is characterized in that the surface layer of a friction disk made of a C / C composite is permeated and diffused with a silicon monoxide gas or the like to react with the friction disk itself to be converted into silicon carbide. It is fundamentally different from the method in which various substances are deposited and coated on carbon fiber by using a method such as PVD method, PVD method, plating, thermal spraying or coating.

That is, the carbon fiber surface obtained by the CVD method, the PVD method, the plating, the thermal spraying, the coating or the like is bonded to the various deposited film substances and the carbon fiber surface only by physical adhesion by the Van der Waals force or the like. In the case of using a C / C composite friction disk made of such carbon fibers, the deposited coating material may peel off due to thermal expansion difference or shear stress due to repeated use under high temperature and high pressure. Cause deterioration in wear resistance and oxidation resistance at an early stage.

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 is not chemically corroded and which is excellent in oxidation resistance and wear resistance, and the surface layer itself of the friction disk is monoxide. Since it has changed into silicon carbide by reacting with silicon etc., the boundary has a completely continuous structure,
The silicified layer is not peeled off by repeated use under high temperature and high pressure, and oxidation resistance and wear resistance are secured for a long time.

[0020]

EXAMPLES Next, the present invention will be specifically described by way of examples.

Example 1 Layers of carbon fiber knitted fabric were superposed on each other and impregnated with a phenol resin, which was then pressure-cured at a pressure of 150 kg / cm ² using a hot press to have a diameter of 250 mmΦ and a thickness of 15 mm.
A molded body of was obtained. This was calcined and carbonized at 900 ° C. to obtain a friction disk made of a C / C composite. Here, the obtained friction disc was further impregnated with phenol resin and calcined and carbonized four times to obtain a density of 1.58 g / cm ³ and a bending strength of 1150.
kg / cm ² AG, elastic modulus (Young's modulus) 1300 kg /
A friction disk of mm ² AG was produced. This friction disk was placed in the same graphite container so as not to come in contact with 1.5 kg of a mixture of silicon powder and silicon dioxide powder (molar ratio 1: 1), sealed, heated at 1800 ° C., and held at this temperature for 90 minutes. The surface layer was converted to silicon carbide.

As a result of this processing, as shown in FIG.
A friction disk 1 having a layer 2 in which the surface layer of the composite 3 had a thickness of about 2.6 mm and which was converted into β-type silicon carbide containing unreacted carbon was produced. The layer 2 converted into silicon carbide was converted into silicon carbide, as shown in FIG. 2, with carbon fibers composed of a portion 5 added to silicon carbide and unreacted carbon portion 6 and having a thickness of about 2.6 mm from the surface. It is composed of a carbon matrix consisting of a portion 7 and unreacted carbon 8.

A wear disk made of a C / C composite obtained by converting the surface layer obtained above into silicon carbide has a density of 1.61 g / cm ³ and a bending strength of 1820 kg / cm ² A.
G, elastic modulus (Young's modulus) was 1910 kg / mm ² AG.

This friction disk was placed in an air atmosphere at 600 ° C., and the oxidation consumption rate after 100 hours was measured.
It was about 1/15 of the oxidative consumption rate of the conventional friction disc in which the surface layer was not converted to silicon carbide.

The friction rate was measured by contacting this friction disk with a rotating body made of stainless steel at a pressure of 588 N. As a result, the wear rate of the conventional friction disk whose surface layer was not converted to silicon carbide was about 1%. It was / 3.

Example 2 As shown in FIG. 3, a two-dimensional cloth was prepared by using a carbon fiber having a layer 5 in which the surface layer was converted to β-type silicon carbide, and the two-dimensional cloth was laminated on the phenol resin. After the impregnation, it was pressure-cured with a pressure of 150 kg / cm ² using a hot press to obtain a molded product having a diameter of 250 mmΦ and a thickness of 15 mm.
This was fired at 900 ° C. and carbonized to prepare a friction disk made of a C / C composite. This friction disc was further impregnated with phenol resin four times and calcined and carbonized to give a density of 1.5.
A friction disk having a bending strength of 9 g / cm ³ , a bending strength of 1470 kg / cm ² AG and an elastic modulus (Young's modulus) of 1490 kg / mm ² AG was obtained.

This friction disc was placed in an air atmosphere at 600 ° C., and the oxidation consumption rate after 100 hours was measured.
It was about 1/20 of the oxidation consumption rate of the conventional friction disk which was not converted to silicon carbide.

The friction rate was measured by contacting this friction disk with a rotating body made of stainless steel at a pressure of 588 N. As a result, the wear rate was about 1/2 of that of the conventional friction disk not converted to silicon carbide. there were.

Example 3 As in Example 1, the carbon fiber knitted fabrics were superposed and impregnated with the phenol resin, and then hot-pressed 1
Pressure of 50 kg / cm ^{2 is used} for pressure curing, and the diameter is 250 m.
A molded body having mΦ and a thickness of 15 mm was obtained. This was fired at 900 ° C. and carbonized to obtain a friction disk made of a C / C composite. Here, the obtained friction disc was repeatedly impregnated with phenol resin and calcined and carbonized four times to obtain a density of 1.58 g / c.
A friction disk having m ³ , bending strength of 1080 kg / cm ² AG and elastic modulus (Young's modulus) of 1300 kg / mm ² AG was produced. This friction disk was filled in a graphite container together with 1 kg (molar ratio 3: 1) of a mixed powder of carbon powder and silicon dioxide powder, heated at 1800 ° C., and kept at this temperature for 1 hour. The result of this treatment was a wear disc consisting of a C / C composite whose surface layer was converted to β-type silicon carbide.

This friction disk was placed in an air atmosphere at 600 ° C., and the oxidation consumption rate after 100 hours was measured.
It was about 1/12 of the oxidation consumption rate of the conventional friction disc in which the surface layer was not converted to silicon carbide. Further, as a result of contacting this friction disk with a rotating body made of stainless steel of a mating material at a pressure of 588 N, and measuring the wear rate, it was found to be about 1/3 of the wear rate of the conventional friction disk whose surface layer was not converted to silicon carbide. there were.

[0031]

As described above, since the friction disc of the present invention is partially or wholly converted to silicon carbide, the temperature at which the carbon fiber starts the oxidation reaction by friction heat exceeds 500 ° C. However, the silicon carbide in the surface layer suppresses the oxidative consumption, and the bending strength is 1470 kg / cm ² AG to 1820 kg / cm ^2.
AG, elastic modulus 1490 kg / mm ² AG to 1910 k
Since it has a high strength of g / mm ² AG, it can be used with peace of mind because it can sufficiently prevent damage such as deformation and cracking due to sudden strength deterioration.

Further, the friction disk of the present invention has a surface layer of silicon carbide, which has a wear-resistant heat dissipation effect due to the wear resistance-specific effect of silicon carbide and the heat conductivity and heat-dissipation property of carbon fibers. Provide a wear disc having excellent properties.

Further, since the friction disc of the present invention has the structure of the friction disc made of carbon fiber reinforced by silicon carbide, the friction disc has a mechanical strength by the conventional carbon fiber knitting structure, High strength,
A highly elastic material can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a friction disc manufactured by a manufacturing method of the present invention.

FIG. 2 is a schematic enlarged cross-sectional view of part A of FIG.

FIG. 3 is a schematic cross-sectional view of carbon fibers before and after silicidation treatment.

[Explanation of symbols]

 1 Friction Disk 2 Layer Converted to Silicon Carbide Containing Unreacted Carbon 3 C / C Composite 4 Carbon Fiber 5 Part Converted to Silicon Carbide of Carbon Fiber 6 Unreacted Carbon Part of Carbon Fiber 7 To Silicon Carbide of Carbon Matrix Converted part 8 Unreacted carbon part of carbon matrix

Claims (1)

[Claims] 1. C / partially or wholly converted to silicon carbide
It is made of C composite and its bending strength is 1470 kg / cm.
² AG-1820 kg / cm ² AG, elastic modulus 1490 k
Friction disc that is g / mm ² AG to 1910 kg / mm ² AG.