JP6921787B2 - Braking material and its manufacturing method - Google Patents

Description

The present invention relates to a braking material and a method for producing the same, and more particularly to a braking material suitable for a brake disc or the like and a method for producing the braking material, which is based on a silicon carbide-based composite material in which silicon carbide ceramics are reinforced with carbon fibers.

Disc brakes are a type of braking device and are mainly used in railway vehicles, automobiles, bicycles, and the like. This disc brake generates frictional force by sandwiching a brake disc that rotates with wheels from both sides with brake pads, and converts kinetic energy into heat energy for braking.
Steel materials such as stainless steel and chrome steel are usually used as brake discs for railway vehicles and automobiles.

However, in recent years, in order to improve running performance and fuel efficiency, it has been required to reduce the weight of the vehicle body and the unsprung weight, and the change of the brake disc to a material lighter than the steel material is being considered.
As one of such materials, silicon carbide-based ceramics are attracting attention because of their light weight and high strength. However, conventional silicon carbide ceramics are brittle materials, have no toughness, and do not have sufficient properties for application to impact brake discs.

Therefore, in order to obtain a silicon carbide ceramic material having high damage tolerance, it is being studied to use a composite material with carbon fiber or silicon carbide fiber. Further, as a method for obtaining a silicon carbide ceramic composite material having higher oxidation resistance, a method of impregnating silicon carbide with molten silicon is known.

For example, the applicant comprises a bundle of short carbon fibers arranged in parallel and a bundle of other carbon components, carbon, silicon, and silicon carbide, and the fiber aggregate is composed of carbon, silicon, and silicon carbide. The feature is that the vertical cross-sectional shape with respect to the length direction is a flat shape with a major axis of 1 mm or more and a major axis / minor axis ratio of 1.5 or more and 5 or less, and a plurality of them are randomly oriented mainly in the two-dimensional direction. A carbon fiber reinforced silicon carbide-based composite material has been proposed (Patent Document 1).
Further, Patent Document 1 describes that this carbon fiber reinforced silicon carbide-based composite material is excellent in strength and toughness and is suitable as a braking material for a brake disc or the like.

Further, Patent Document 2 describes a step of forming a filmed fiber aggregate by assembling short fibers A made of carbon fibers and forming a carbon film on the outer surface thereof, and mixing silicon carbide and a carbon material. A step of producing a raw material to be a base material portion, and a step of mixing the coated fiber aggregate, the raw material to be a base material portion, and short fibers B made of carbon fibers without a carbon coating to prepare a mixture. A step of molding and pressurizing the mixture to prepare a molded body, a step of firing the molded body in a reducing atmosphere to prepare a fired body, and a step of impregnating the fired body with silicon under reduced pressure. A method for producing carbon fiber-reinforced silicon carbide-based ceramics has been proposed, which comprises the steps to be carried out and the steps to be carried out. Further, Patent Document 2 discloses an application to a brake disc as an application of carbon fiber reinforced silicon carbide-based ceramics.

Japanese Unexamined Patent Publication No. 2013-209281 Japanese Unexamined Patent Publication No. 2012-153575

By the way, since the braking material (brake disc) during braking becomes extremely hot due to frictional heat, even the carbon fiber-reinforced silicon carbide-based ceramics (composite material) impregnated with silicon shown in Patent Documents 1 and 2 can be used. When exposed to high temperature, the carbon fibers on the surface of the braking material are oxidized and the surface is roughened, so that the braking performance is deteriorated and it is necessary to replace it.
That is, when the carbon fiber reinforced silicon carbide composite material is exposed to a high temperature state, the carbon fibers on the surface are oxidized, and as a result, the braking performance is lowered and the product life is short.

In order to solve such a problem, the present inventor uses a carbon fiber reinforced silicon carbide-based composite material which is lightweight and has excellent mechanical strength as a base material for a braking material, and carbon fiber-free and carbonized on the surface thereof. The idea was to provide a sliding layer in which silicon is impregnated with molten silicon. Further, in order to solve the problem of brittleness and insufficient strength caused by the fact that the sliding layer does not contain carbon fibers, intensive studies have been carried out to complete the present invention.

The present invention has been made under the above circumstances, and an object of the present invention is to provide a braking material having excellent thermal shock resistance and wear resistance and a longer life, and a method for manufacturing the same.

The braking material according to the present invention made to achieve the above object is a substrate made of a silicon carbide composite material containing carbon fibers, and carbon formed on the surface of the substrate at least in a region where the brake pad slides. A braking material including a fiber-free sliding layer, wherein the sliding layer is a first silicon carbide particle having a first particle size and a first silicon carbide particle having the first particle size. A silicon carbide sintered portion formed of second silicon carbide particles having a second particle size smaller than the first particle size, and silicon carbide particles having the first particle size and the silicon carbide. the gap remaining between the sintered portion, containing carbon from silicon and a binder, is characterized in that.

In the braking material according to the present invention, since a sliding layer containing no carbon fibers is formed on the surface of the substrate, the carbon fibers are not exposed on the surface of the braking material, and the oxidation of the carbon fibers is suppressed.
Further, in the sliding layer, the first silicon carbide particles having a first particle size are silicon carbide fired formed of second silicon carbide particles having a second particle size smaller than the first particle size. Since the braking material according to the present invention is connected by a knot, the mechanical strength is increased, cracks at the Si origin are suppressed, and the product life is improved.
When the second particle size of the silicon carbide particles forming the silicon carbide sintered portion is larger than the first particle size of the first silicon carbide particles, the sintering reaction of the second silicon carbide particles It becomes difficult to form a connected silicon carbide sintered portion because the amount of silicon carbide decreases and it becomes difficult to sinter.

Here, it is desirable that the first particle size is 100 μm or more and 180 μm or less, and the second particle size is 0.4 μm or more and 5 μm or less.
If the first particle size is less than 100 μm, the molding bulk density becomes large, and the shrinkage becomes large in the subsequent heating, causing cracks and peeling, which is not preferable. On the other hand, when the first particle size exceeds 180 μm, the gap between the first silicon carbide particles becomes large and the amount of Si having low thermal shock resistance in the final form increases, which is not preferable.
Further, when the second particle size is less than 0.4 μm, it becomes difficult to disperse the first and second silicon carbide particles, and the particles are unevenly distributed, which is not preferable. On the other hand, when the second particle size exceeds 5 μm, it is difficult for the second silicon carbide particles to be embedded in the gap between the first silicon carbide particles, which is not preferable.

Further, it is desirable that the film thickness of the sliding layer is 1 mm or more and 3 mm or less.
Further, when the thickness of the sliding layer is less than 1 mm, the carbon fibers constituting the substrate may be exposed on the surface, and the oxidation inhibitory action of the carbon fibers is reduced.
If the film thickness of the sliding layer exceeds 3 mm, chipping is likely to occur, which is not preferable.

The method for producing a braking material according to the present invention, which has been made to achieve the above object, is formed on a substrate made of a silicon carbide composite material containing carbon fibers and at least a region on the surface of the substrate on which a brake pad slides. Further, a method for producing a braking material including a sliding layer containing no carbon fiber, wherein a substrate is formed from a first raw material containing at least carbon fibers, silicon carbide particles, and a binder, and at least the first step. the first silicon carbide particles having a particle size, by a second material comprising a second silicon carbide particles and the binder of the small second diameter than the first particle size, slurry for forming the sliding layer The step of forming the sliding layer by applying the slurry to at least a part of the surface of the substrate, the step of firing the substrate on which the sliding layer is formed, and the calcined, said sliding. It is characterized by including a step of impregnating a substrate on which a moving layer is formed with silicon under reduced pressure.

By mixing silicon carbide particles having different particle diameters as a raw material for the sliding layer in this way, the first silicon carbide particles having the first particle size can be made into a second particle smaller than the first particle size. It can be connected by a silicon carbide sintered portion formed of the second silicon carbide particles having a particle size of.
Further, the remaining gap between the first silicon carbide particles having the first particle size and the silicon carbide sintered portion can be impregnated with silicon.
As a result, it is possible to manufacture a long-life braking material in which the mechanical strength is improved and cracks at the Si origin are suppressed.

Here, it is desirable that the first particle size is 100 μm or more and 180 μm or less, and the second particle size is 0.4 μm or more and 5 μm or less.
If the first particle size is less than 100 μm, the molding bulk density becomes large, and the shrinkage becomes large in the subsequent heating, causing cracks and peeling, which is not preferable. On the other hand, when the first particle size exceeds 180 μm, the gap between the first silicon carbide particles becomes large and the amount of Si having low thermal shock resistance in the final form increases, which is not preferable.
Further, when the second particle size is less than 0.4 μm, it becomes difficult to disperse the first and second silicon carbide particles, and the particles are unevenly distributed, which is not preferable. On the other hand, when the second particle size exceeds 5 μm, it is difficult for the second silicon carbide particles to be embedded in the gap between the first silicon carbide particles, which is not preferable.

Further, it is desirable that the film thickness of the sliding layer is 1 mm or more and 3 mm or less.
Further, when the thickness of the sliding layer is less than 1 mm, the carbon fibers constituting the substrate may be exposed on the surface, and the oxidation inhibitory action of the carbon fibers is reduced.

According to the present invention, it is possible to obtain a braking material having excellent thermal shock resistance and wear resistance and having a longer life, and a method for producing the same.

FIG. 1 is a cross-sectional photograph of a sliding layer according to an embodiment of the present invention. FIG. 2 is a diagram schematically showing a portion of the cross-sectional photograph shown in FIG. 1 surrounded by a white line. FIG. 3 is a cross-sectional photograph of a sliding layer of a comparative example. FIG. 4 is a diagram schematically showing a portion of the cross-sectional photograph shown in FIG. 3 surrounded by a white line.

An embodiment of the braking material of the present invention will be described.
The braking material according to the present invention comprises a substrate made of a silicon carbide composite material containing carbon fibers and a carbon fiber-free sliding layer formed on the surface of the substrate at least in a region where the brake pads slide. I have.
The substrate is made of a silicon carbide composite material containing carbon fibers, and the number, length, diameter of carbon fibers, the particle size of silicon carbide, the ratio of silicon carbide to carbon fibers, and the like can be appropriately selected. It can be done, and it is not particularly limited.
Specifically, for example, the carbon fiber reinforced silicon carbide-based composite material described in Patent Document 1 (Japanese Unexamined Patent Publication No. 2013-209281) can be used. Further, carbon fiber reinforced silicon carbide-based ceramics described in Patent Document 2 (Japanese Unexamined Patent Publication No. 2012-153575) can be used.

The sliding layer is the entire surface of the main surface of the braking material (base) or a part of the main surface of the braking material (base), and is formed in a region where the brake pads slide.
This sliding layer does not contain carbon fibers and connects the first silicon carbide particles having the first particle size and the first silicon carbide particles having the first particle size, from the first particle size. A silicon carbide sintered portion formed of a second silicon carbide particle having a small second particle size, a silicon carbide particle having the first particle size, and silicon formed in a gap between the silicon carbide sintered portion. Contains carbon.

The cross-sectional structure of this sliding layer is shown in FIGS. 1 and 2.
FIG. 1 is a cross-sectional photograph of a sliding layer of the braking material of the present invention, which was taken with a microscope after polishing the cross section of the sliding layer. Further, FIG. 2 is a diagram schematically showing a part of the cross-sectional photograph shown in FIG. 1, in which the silicon carbide particles 1 having the first particle size are shown by hatching with diagonal lines downward to the right, and have the second particle size. The region of the silicon carbide sintered portion 2 formed of the second silicon carbide particles is indicated by hatching with a diagonal line downward to the left, impregnated silicon 3 is indicated by scattered dots, and carbon 4 carbonized by the binder is indicated in black. ing.

As described above, the silicon carbide sintered portion 2 is formed by react-sintering the second silicon carbide particles having a second particle size smaller than the first particle size.
Further, since the first silicon carbide particles and the second silicon carbide particles are reaction-sintered and connected to each other, the first silicon carbide particles are connected to each other via the silicon carbide sintered portion 2.
Further, as is clear from FIGS. 1 and 2, the gaps between the silicon carbide sintered portion 2 formed of the silicon carbide particles 1 having the first particle size and the silicon carbide particles having the second particle size are impregnated with the silicon 3 and the silicon carbide. Carbon 4 in which the binder is carbonized is formed.

In this way, since the first silicon carbide particles 1 are connected to each other via the silicon carbide sintered portion 2, the bond between the silicon carbide crystal grains 1 having the first particle size is strong, and the sliding layer of the sliding layer has a strong bond. Thermal impact resistance and abrasion resistance are further improved.

Further, since this sliding layer does not contain carbon fibers, the carbon fibers are not exposed on the surface of the sliding layer, and the carbon fibers are not oxidized under high temperature and high humidity.
As a result, the braking material according to the implementation of the present invention suppresses surface damage, improves durability, and further improves the life (longer life) even in an environment exposed to high temperatures due to frictional heat. do).

It is desirable that the first particle size is 100 μm or more and 180 μm or less, and the second particle size is 0.4 μm or more and 5 μm or less.
If the first particle size is less than 100 μm, the molding bulk density becomes large, and the shrinkage becomes large in the subsequent heating, causing cracks and peeling, which is not preferable. On the other hand, when the first particle size exceeds 180 μm, the gap between the first silicon carbide particles becomes large and the amount of Si having low thermal shock resistance in the final form increases, which is not preferable.
Further, when the second particle size is less than 0.4 μm, it becomes difficult to disperse the first and second silicon carbide particles, and the particles are unevenly distributed, which is not preferable. On the other hand, when the second particle size exceeds 5 μm, it is difficult for the second silicon carbide particles to be embedded in the gap between the first silicon carbide particles, which is not preferable.
Here, the particle size means the median diameter and the mesh opening.

Further, it is desirable that the film thickness of the sliding layer is 1 mm or more and 3 mm or less.
This is because when the thickness of the sliding layer is less than 1 mm, the carbon fibers constituting the substrate may be exposed on the surface, and the oxidation inhibitory action of the carbon fibers is reduced.
If the film thickness of the sliding layer exceeds 3 mm, chipping is likely to occur, which is not preferable.

Next, the manufacturing method of the embodiment according to the present invention will be described.
Method of manufacturing a dynamic material according to the present invention includes the steps of forming the substrate from a first material containing at least carbon fiber and silicon carbide particles and a binder, and a first silicon carbide particles of at least a first diameter, said A step of applying a second raw material containing a second silicon carbide particle having a second particle size smaller than the first particle size and a binder to the surface of the molded substrate to form a sliding layer. It is characterized by including a step of firing the substrate and the sliding layer, and a step of impregnating the fired substrate and the sliding layer with silicon under reduced pressure. In particular, this manufacturing method is characterized in that a sliding layer is formed on the surface of the substrate.

The method for forming the substrate is not particularly limited as long as the substrate can be formed from the first raw material containing carbon fibers, silicon carbide particles, and a binder.
For example, the method for producing a carbon fiber-reinforced silicon carbide-based composite material described in Patent Document 1 (Japanese Unexamined Patent Publication No. 2013-209281) can be used. Further, the method for producing carbon fiber reinforced silicon carbide ceramics described in Patent Document 2 (Japanese Unexamined Patent Publication No. 2012-153575) can be used.

As an example, a raw material containing carbon fibers and silicon carbide particles is mixed to prepare a slurry, and a substrate is molded by gel casting under pressure or reduced pressure.
In the preparation of this slurry, carbon fibers and carbon powder are added to the silicon carbide particles which are the main raw materials, and an organic substance having a gelling ability is further added, and the obtained slurry is cast into a mold under pressure or reduced pressure. Molding can be performed by combining so-called gel cast molding, which is gelled or cured with, and pressure or pressure molding.

Further, in the silicon impregnation step after preparing the substrate molded body, a part of the carbon fiber and the carbon powder to be impregnated react with each other to form silicon carbide. By adjusting the above conditions, the composition ratio of silicon carbide and carbon fiber and the density of silicon carbide can be freely adjusted.
The content of the carbon fiber is preferably 10% by weight or more and 40% by weight or less, and the content of the carbon powder is preferably 1% by weight or more and 15% by weight or less. If the carbon fiber content is less than 10% by weight, sufficient fracture energy cannot be secured, and if it exceeds 40% by weight, the relative ratio of silicon carbide decreases and the bending strength decreases, which is not preferable.

Further, since it is a braking material, it is preferable that the substrate is a disk-shaped flat body, the maximum length of the main surface is 300 mm or more and 1000 mm or less, and the thickness is 20 mm or more and 100 mm or less.
Here, the maximum length of the main surface is the maximum length that can be taken on the surface, such as the diameter of a disk.

The step of applying to the surface of the molded substrate to form a sliding layer involves a first silicon carbide particle having at least a first particle size and a second particle size smaller than the first particle size. This is done by mixing a second raw material containing the second silicon carbide particles to prepare a slurry and applying it to the surface of the molded substrate.

It is desirable that the first particle size is 100 μm or more and 180 μm or less, and the second particle size is 0.4 μm or more and 5 μm or less.
If the first particle size is less than 100 μm, the molding bulk density becomes large, and the shrinkage becomes large in the subsequent heating, causing cracks and peeling, which is not preferable. On the other hand, when the first particle size exceeds 180 μm, the gap between the first silicon carbide particles becomes large and the amount of Si having low thermal shock resistance in the final form increases, which is not preferable.
Further, when the second particle size is less than 0.4 μm, it becomes difficult to disperse the first and second silicon carbide particles, and the particles are unevenly distributed, which is not preferable. On the other hand, when the second particle size exceeds 5 μm, it is difficult for the second silicon carbide particles to be embedded in the gap between the first silicon carbide particles, which is not preferable.
The particle size referred to here means the median diameter and the mesh opening.

Further, in the preparation of the slurry, a binder is added to the first silicon carbide particles having a first particle size and the second silicon carbide particles having a second particle size smaller than the first particle size, and the mixture is mixed. It is done by doing.

The blending ratio of the first silicon carbide particles having the first particle size and the second silicon carbide particles having the second particle size smaller than the first particle size is 60:40 to 80:20. Is preferable.
Further, the ratio of the first silicon carbide particles and the second silicon carbide particles to the binder is preferably 100:25 to 100:35.

The method for applying the slurry for forming the sliding layer on the surface of the molded substrate is not particularly limited, and a cast molding method, a gel cast molding method, or the like can be used. Further, the coating is applied at least to the region where the brake pads slide.
The coating thickness is such that the film thickness of the sliding layer is 1 mm or more and 3 mm or less. Further, when the thickness of the sliding layer is less than 1 mm, the carbon fibers constituting the substrate may be exposed on the surface, and the oxidation inhibitory action of the carbon fibers is reduced.
If the film thickness of the sliding layer exceeds 3 mm, chipping is likely to occur, which is not preferable.

Next, the molded substrate coated with the slurry is dried at 150 ° C. for 2 hours in an air atmosphere, and then first fired at 1000 ° C. for 1 hour in a reducing atmosphere.
Further, it is secondarily fired at 2000 ° C. in a reducing atmosphere.
Then, in the silicon impregnation step, the fired body obtained by the above step is impregnated with molten silicon at 1600 ° C. under a reduced pressure of 10 Pa to prepare a braking plate.

In the above firing, as shown in FIGS. 1 and 2, the silicon carbide sintered portion 2 is formed by react-sintering the second silicon carbide particles with each other.
Further, since the first silicon carbide particles and the second silicon carbide particles are reaction-sintered and connected, the first silicon carbide particles 1 are connected to each other via the silicon carbide sintered portion 2.
Further, the impregnated silicon 3 and the carbon 4 in which the binder is carbonized are formed in the gaps between the silicon carbide particles 1 and the silicon carbide sintered portion 2.

In this way, the first silicon carbide particles and the silicon carbide sintered portion 2 (second silicon carbide particles) are reaction-sintered and connected to each other, so that the first silicon carbide particles are connected to each other in the silicon carbide sintered portion. It is connected via 2.
As a result, the bond between the silicon carbide crystal grains 1 having the first particle size is strong, and the sliding layer has further improved thermal shock resistance and wear resistance.

Further, since this sliding layer does not contain carbon fibers and is formed on the surface of a substrate made of a composite material of silicon carbide reinforced with carbon fibers, the carbon fibers can be oxidized at a high temperature. Can be prevented.
Further, since this sliding layer has few portions where silicon is continuously present and is formed of silicon carbide particles, this braking material has high thermal shock resistance and the occurrence of chips and the like is suppressed.

Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to the following examples.

[Example 1]
(Preparation of substrate)
The powder raw material was prepared by mixing 20 parts by weight of carbon fiber having an average length of 8 mm, 30 parts by weight of silicon carbide particles having an average particle size of 0.8 μm, and 10 parts by weight of carbon black having an average particle size of 50 nm. To this powder raw material, 15 parts by weight of ethanol, 10 parts by weight of phenol resin, 10 parts by weight of sorbitol polyglycidyl ether which is a crosslinkable polymerizable resin such as imine resin, and 5 parts by weight of polyethyleneimine which is a crosslinking agent are added. Mixed.

Then, the compound was placed in a SUS mold, gelled or cured under a pressure of ^{100 N / cm 2, and then demolded and dried to obtain a molded product.}

(Formation of sliding layer)
Silicon carbide particles of a particle size of 160 .mu.m, and particle size of 2μm silicon carbide particles, a binder, 75: 25: 30 were mixed in a weight ratio of to prepare a slurry.
Then, it was applied to the substrate molded body by a casting method so that the thickness of the coating film was 2 mm.

Then, the substrate molded product coated with the slurry is dried at 150 ° C. for 2 hours in an air atmosphere, and then first fired at 1000 ° C. for 1 hour in a reducing atmosphere.
Further, it is secondarily fired at 2000 ° C. in a reducing atmosphere. Then, in the silicon impregnation step, the fired body obtained by the above step was impregnated with molten silicon at 1600 ° C. under a reduced pressure of 10 Pa to prepare a braking plate.

Then, the surface of the sliding layer was polished and its cross section was observed with a microscope. The results are shown in FIGS. 1 and 2.
As already described, as is clear from FIGS. 1 and 2, impregnated silicon is formed in the gaps between the silicon carbide particles 1 having the first particle size and the silicon carbide sintered portion 2 formed of the silicon carbide particles having the second particle size. 3 and carbon 4 in which the binder is carbonized are formed.
Further, the silicon carbide particles 1 having a first particle size are connected by a sintering reaction by a silicon carbide sintering portion 2 formed of silicon carbide particles having a second particle size smaller than the first particle size. It was confirmed that

Next, the thermal shock resistance and wear resistance of this sliding layer were verified.
For verification, a scale tester test of φ150 mm × 10 t was carried out. In addition, a friction material generally used for passenger cars was used.
In the test pattern, braking at an initial speed of 100 km / h and a deceleration of 4.5 m / s ² was repeated 100 times. After the test, the chip on the rotor surface was observed and the amount of wear of the rotor material was measured.
The results are shown in Table 1.

[Comparative Example 1]
A substrate was prepared in the same manner as in Example 1. Further, unlike Example 1, the slurry of the sliding layer is prepared by mixing silicon carbide particles having a particle size of 160 μm and a binder at a weight ratio of 100:30 without using silicon carbide particles having a particle size of 2 μm. , Prepared. Then, in the same manner as in Example 1, a slurry was prepared and coated by a casting method so that the thickness of the coating film was 2 mm.
Then, under the same conditions as in Example 1, it was dried and fired, impregnated with molten silicon, and a braking plate was produced.

Then, the surface of the sliding layer was polished and its cross section was observed with a microscope. The results are shown in FIGS. 3 and 4. FIG. 3 is a diagram corresponding to FIG. 1, and FIG. 4 is a diagram corresponding to FIG. 2.
As is clear from FIGS. 3 and 4, it was found that the silicon carbide particles 1 were occupied by the impregnated silicon 3, and the silicon carbide particles 1 were not connected to each other.

Next, the thermal shock resistance and wear resistance of this sliding layer were verified.
The verification was performed under the same conditions as in Example 1, and after the test, chipping on the rotor surface was observed and the amount of wear of the rotor material was measured. The results are shown in Table 1.

Comparing Example 1 and Comparative Example 1, improvements in thermal shock resistance and wear resistance were observed.
Since the sliding layer of Comparative Example 1 is occupied by the impregnated silicon 3 between the silicon carbide particles 1 and the silicon carbide particles 1 are not connected to each other, the strength thereof is substantially determined by the impregnated silicon. It is considered to be.
On the other hand, in Example 1, the silicon carbide particles 1 having the first particle size are the silicon carbide sintered portions 2 formed of silicon carbide particles having a second particle size smaller than the first particle size. Because they are connected by the sintering reaction, the bond between the first silicon carbide particles 1 is strong. As a result, it is considered that Example 1 has improved wear resistance and durability.

(Verification of the first particle size of silicon carbide particles)
The first particle size of the silicon carbide particles forming the sliding layer was changed to 100 μm (Example 2), 180 μm (Example 3), 90 μm (Comparative Example 2), and 190 μm (Comparative Example 3), resulting in chipping and wear. The amount was verified. Other conditions were the same as in Example 1. The results are shown in Table 2.

As can be seen from Table 2, when the first particle size of the silicon carbide particles is 90 μm (Comparative Example 2), the amount of wear is large, and the first particle size of the silicon carbide particles is 190 μm (Comparative Example 3). case, chipping occurs, also possible wear amount is large has been found.
When the first particle size of the silicon carbide particles was 90 μm (Comparative Example 2), some cracks and peeling occurred during production, which made production difficult. In this verification, the one in which no crack or peeling occurred was used.
As described above, it has been found that the first particle size of the silicon carbide particles forming the sliding layer is preferably 100 μm or more and 180 μm or less.

(Verification of the second particle size of silicon carbide particles)
The second particle size of the silicon carbide particles forming the sliding layer is changed to 0.4 μm (Example 4), 5 μm (Example 5), 0.3 μm (Comparative Example 4), and 6 μm (Comparative Example 5). Then, the amount of chipping and wear was verified. Other conditions were the same as in Example 1. The results are shown in Table 3.

As can be seen from Table 3, when the second particle size of the silicon carbide particles is 0.3 μm (Comparative Example 4) and the second particle size of the silicon carbide particles is 6 μm (Comparative Example 5), the amount of wear is large. It was also found that when the second particle size was 0.3 μm (Comparative Example 4), chipping also occurred.

(First silicon carbide particles with a first particle size, and second silicon carbide particles of a second particle size, verification of blending ratio of the binder)
In Example 1, the first particle size of the silicon carbide particles is 160 μm, the second particle size of the silicon carbide particles is 2 μm, and the ratio of the first silicon carbide particles , the second silicon carbide particles, and the binder is 60. : 40:30, and other conditions were the same as in Example 1, and a sliding layer having a thickness of 2 mm was formed on the substrate (Example 6). The production conditions were the same as in Example 1.
Then, the thermal shock resistance and the wear resistance were verified under the same conditions as in Example 1. The results are shown in Table 3.

Further, as shown in Table 3, a sliding layer having a thickness of 2 mm was provided on the substrate under the same manufacturing conditions as in Example 1 by changing the ratio of the first silicon carbide particles , the second silicon carbide particles, and the binder. It was formed (Examples 7,8,9, Comparative Examples 6,7,8,9). Other conditions were the same as in Example 6.
Then, the thermal shock resistance and the wear resistance were verified under the same conditions as in Example 1. The results are shown in Table 3.

As can be seen from Table 3, Comparative Examples 6 and 7 had a large amount of wear, and Comparative Example 7 had chipping, which was not preferable. Further, Comparative Examples 8 and 9 could not be manufactured due to peeling during molding.
Therefore, the blending ratio of the first silicon carbide particles having the first particle size and the second silicon carbide particles having the second particle size smaller than the first particle size is 60:40 to 80:20. It has been found that the ratio of the first silicon carbide particles and the second silicon carbide particles to the binder is preferably 100:25 to 100:35.

(Verification of the film thickness of the sliding layer)
The film thickness of the sliding layer was changed to 0.5 mm (Comparative Example 10) and 4 μm (Comparative Example 7) in the thickness of the sliding layer in Example 1, and the amount of chipping and wear was verified. Other conditions were the same as in Example 1. The results are shown in Table 4.

In Comparative Example 10, the carbon fibers constituting the substrate were exposed on the surface, which was not preferable. Further, in Comparative Example 11, chipping occurred in the sliding layer, which was not preferable.
Therefore, it was found that the film thickness of the sliding layer is preferably 1 mm or more and 3 mm or less.

1 First silicon carbide particles with a first particle size 2 Second silicon carbide particles with a second particle size 3 Impregnated silicon 4 Carbon

Claims (6)

A braking material including a substrate made of a silicon carbide composite material containing carbon fibers and a sliding layer containing no carbon fibers formed at least in a region on the surface of the substrate on which the brake pads slide.
The sliding layer
With the first silicon carbide particles of the first particle size,
A silicon carbide sintered portion formed of second silicon carbide particles having a second particle size smaller than the first particle size, which connects the first silicon carbide particles having the first particle size.
The gap remaining between the silicon carbide sintered portion and the silicon carbide particles of the first particle size, including the carbon from the silicon and a binder, and
Braking material characterized by that. The braking material according to claim 1, wherein the first particle size is 100 μm or more and 180 μm or less, and the second particle size is 0.4 μm or more and 5 μm or less. The braking material according to claim 1 or 2, wherein the thickness of the sliding layer is 1 mm or more and 3 mm or less. A method for manufacturing a braking material including a substrate made of a silicon carbide composite material containing carbon fibers and a sliding layer containing no carbon fibers formed at least in a region where a brake pad slides on the surface of the substrate. There,
The process of molding the substrate from a first raw material containing at least carbon fibers, silicon carbide particles and a binder.
The sliding layer is made of a second raw material containing a first silicon carbide particle having at least a first particle size, a second silicon carbide particle having a second particle size smaller than the first particle size, and a binder. A step of preparing a slurry to form a sliding layer and applying the slurry to at least a part of the surface of the substrate to form a sliding layer.
The step of firing the substrate on which the sliding layer is formed and
A step of impregnating the fired substrate on which the sliding layer is formed with silicon under reduced pressure.
A method for manufacturing a braking material, which comprises. The method for producing a braking material according to claim 4, wherein the first particle size is 100 μm or more and 180 μm or less, and the second particle size is 0.4 μm or more and 5 μm or less. The method for manufacturing a braking material according to claim 5, wherein the thickness of the sliding layer is 1 mm or more and 3 mm or less.

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