JP2001214247A - Sliding material for brake composed of metal composite, producing method therefor, brake rotor and brake drum - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sliding material for a brake excellent in capacities required for a sliding material for a brake, particularly, in hardness, heat resistance, wear resistance, a moderate friction coefficient and the stability of the friction coefficient. SOLUTION: This sliding material for a brake is composed of a metal composite obtained by impregnating aluminum or an aluminum alloy containing titanium by 0.5 to 5% in a volume ratio into a preliminarily molded body formed of ceramic fibers, carbon fibers, ceramic whiskers, ceramic particles or carbon particles.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sliding material for a brake made of a metal composite having aluminum or an aluminum alloy as a matrix, a method for producing the same, a brake rotor and a brake drum.

[0002]

2. Description of the Related Art A preform formed into a desired shape by adding an appropriate excipient to fibers, whiskers or particles of ceramics such as alumina, silicon carbide or titanium carbide as a composite material having excellent wear resistance and light weight. An aluminum matrix composite material in which a body is impregnated with a molten aluminum alloy by molten forging is known.

[0003] In this aluminum matrix composite material, since the aluminum of the matrix metal is soft, even if it is formed by a molten metal forging method, heat resistance,
There was a limit in wear resistance, hardness and the like, and the performance required for a sliding material for a brake could not be sufficiently satisfied. In addition, a suitable friction coefficient required for a sliding material for a brake and stability of the friction coefficient are lacking, and thus lack practicality.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide excellent performance required for a sliding material for a brake, in particular, excellent hardness, heat resistance, wear resistance, an appropriate friction coefficient, and stability of a friction coefficient. It is to provide a sliding material for a brake.

Another object of the present invention is to provide a suitable method for producing the above-mentioned sliding material for a brake.

Another object of the present invention is to provide a brake rotor and a brake drum which are excellent in hardness, heat resistance, abrasion resistance, moderate friction coefficient and stability of friction coefficient using the sliding material for a brake. Is to do.

[0007]

SUMMARY OF THE INVENTION The present invention relates to a preform formed from ceramic fibers, carbon fibers, ceramic whiskers, ceramic particles or carbon particles, comprising aluminum containing 0.5 to 5% by volume of titanium. Also, the present invention relates to a sliding material for a brake made of a metal composite impregnated with an aluminum alloy.

The present invention also relates to a method for forming a preform from ceramic fibers, carbon fibers, ceramic whiskers, ceramic particles or carbon particles and titania particles or titania whiskers, and subjecting the preform to aluminum or aluminum alloy by molten forging. The present invention relates to a method for producing a sliding material for a brake made of a metal composite, which is characterized by impregnating a metal composite (first production method).

According to the present invention, a preform is formed from ceramic fibers, carbon fibers, ceramic whiskers, ceramic particles or carbon particles and titanium metal powder, and the preform is impregnated with aluminum or an aluminum alloy by melt forging. The present invention relates to a method for manufacturing a sliding material for a brake made of a metal composite (second manufacturing method).

According to the present invention, a preform is formed from ceramic fibers, carbon fibers, ceramic whiskers, ceramic particles or carbon particles, and the preform is impregnated with titanium metal and aluminum or an aluminum alloy by melt forging. The present invention also relates to a method for manufacturing a sliding material for a brake made of a metal composite (third manufacturing method).

The present invention also relates to a brake rotor and a brake drum having a sliding surface made of the above-mentioned sliding material for a brake.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The material of ceramic fibers, ceramic whiskers or ceramic particles forming a preform in the sliding material for a brake of the present invention is as follows.
Silica (SiO ₂ ), alumina (Al ₂ O ₃ ), silica
Alumina (SiO ₂ —Al ₂ O ₃ ), silicon carbide (Si
C), silicon nitride (Si ₃ N ₄ ), titanium carbide (Ti
C) and the like, and preferably, silica-alumina fibers are used. The preferred fiber diameter of the ceramic fiber or carbon fiber is 2 to 50 μm, and the preferred fiber length is 1 to 10 mm.
The preferred diameter of the ceramic whisker is 0.1.
2 to 0.5 μm, the preferred length is 5 to 10 μm,
The preferred particle size of the ceramic particles or carbon particles is 50 to
250 μm.

The volume ratio Vf of the preform in the sliding material for a brake is preferably from 10 to 50%, more preferably from 20 to 45%. When the volume ratio Vf is less than 10%, when used for a brake rotor or a brake drum of a final product,
The heat resistance, hardness, etc., are not sufficiently improved, and there is a tendency that the performance required for a sliding material for a brake cannot be secured. Also,
If it exceeds 50%, the impregnation with aluminum or aluminum alloy tends to be difficult.

The sliding material for a brake according to the present invention comprises a metal composite obtained by impregnating this preformed body with aluminum or an aluminum alloy containing 0.5 to 5% by volume of titanium, and comprising an Al-Ti intermetallic compound. Is formed, heat resistance and hardness are increased, and a necessary and appropriate friction coefficient for a sliding material for a brake and stability of the friction coefficient can be secured. If the volume ratio of titanium is less than 0.5%, the heat resistance and hardness of the material are insufficient, and if it exceeds 5%, the material becomes brittle.

The metal composite in which such a preformed body is impregnated with aluminum or an aluminum alloy containing 0.5 to 5% by volume of titanium is provided by the first production method, the second production method, It can be obtained by three manufacturing methods.

In the production method of the present invention, the preform is
Titanium whiskers, titania particles or titanium metal powder are mixed as necessary with ceramic fibers, carbon fibers, ceramic whiskers, ceramic particles or carbon particles, and water, a binder such as PVA (polyvinyl alcohol), and an excipient such as silica sol are appropriately added. The porous preform is obtained by mixing, forming into a predetermined shape by pressure or the like using a forming die, and drying if necessary.

As the aluminum alloy used for impregnating the preform, an Al-Mg alloy or the like can be used.

According to the first production method, titania particles or titania whiskers are used as a titanium source as a material for forming a preform. In this manufacturing method, a preform is formed of ceramic fibers, carbon fibers, ceramic whiskers, ceramic particles or carbon particles, and titania particles or titania whiskers. Next, this preform is impregnated with aluminum or an aluminum alloy by a molten metal forging method. This titania and aluminum or an aluminum alloy are subjected to a heat treatment performed later, whereby Al
Form Al-Ti intermetallic compound with ₂ O ₃ . A powder having a particle size of 0.05 to 0.5 μm is preferably used as the titania particles, and a titania whisker having a diameter of 0.2
Those having a thickness of 0.5 to 0.5 μm and a length of 5 to 10 μm are preferably used. These may be used as a mixture. The amount of titania particles or titania whiskers used is such that the volume ratio of titanium in aluminum or aluminum alloy is 0.5 to 5%.
%.

According to the second production method, titanium metal powder is used as a titanium source as a material for forming a preform. In this manufacturing method, a preform is formed from ceramic fibers, carbon fibers, ceramic whiskers, ceramic particles or carbon particles and titanium metal powder. Next, this preform is impregnated with aluminum or an aluminum alloy by a molten metal forging method. The heat treatment performed later on the titanium metal powder and aluminum or aluminum alloy forms an Al-Ti intermetallic compound. As the titanium metal powder, a powder having a particle size of 0.5 to 500 μm is preferably used. The amount of titanium metal powder used is 0.5% by volume of titanium in aluminum or aluminum alloy.
量 5%.

According to the third manufacturing method, ceramic fibers,
A preform formed from carbon fibers, ceramic whiskers, ceramic particles or carbon particles is impregnated with titanium metal and aluminum or aluminum alloy by melt forging. The heat treatment performed later on the titanium metal and aluminum or aluminum alloy forms an Al-Ti intermetallic compound. The amount of titanium metal used is 0.5% by volume of titanium in aluminum or aluminum alloy.
量 5%.

In any of the above methods, a metal composite in which a preformed body is impregnated with aluminum or an aluminum alloy containing 0.5 to 5% by volume of titanium can be obtained.
It is preferable to manufacture the metal composite by the first and second manufacturing methods from the viewpoint that, for example, when the temperature of the molten forging becomes high, the life of the mold is shortened.

The brake rotor and the brake drum of the present invention have a sliding surface made of the sliding material for a brake of the present invention. The thickness of the sliding material on the sliding surface is preferably 2 mm or more. Since the brake rotor or brake drum is mounted on the vehicle and receives heat history during its use, the heat treatment gradually progresses gradually, and the heat resistance, wear resistance, appropriate friction coefficient and friction required for the brake rotor are required. Coefficient stability and hardness can be obtained.

That is, in a stage before the heat treatment inevitably proceeds stepwise due to the heat history in the use process,
The hardness, which was only about Hv 200 to 400, is in the range of Hv 400 to 1000 due to the heat history, and the friction coefficient μ depends on the material of the friction material and the material of the brake rotor. From about 0.31 level to about 0.38 level. In addition, the coefficient of friction changed greatly, but the range of change became very small.
The performance required for the brake rotor can be satisfied. Similarly, the heat resistant temperature is improved to about 660 to 1100 ° C. When performing this heat treatment separately, in the temperature range of 450 ° C. to the solidus temperature of aluminum or aluminum alloy,
It is preferably performed for 0.5 to 10 hours.

FIG. 1 shows an example of a process chart for manufacturing the brake rotor of the present invention. As shown in FIG. 1 (a), a ceramic fiber,
A preform 2 made of ceramic whiskers, carbon fibers, ceramic particles or carbon particles and titania particles or titania whiskers is mounted at a predetermined position. Next, an appropriate amount of molten aluminum or aluminum alloy is injected. It is preferable that the preform 2 and the molding die 1 are preheated, and the preheating improves the fluidity of aluminum or an aluminum alloy, and smoothes the impregnation of the preform 2. The temperature of the molten aluminum or aluminum alloy itself is preferably 50 to 450 ° C. higher than its melting point in order to facilitate the impregnation of the preform 2. Next, as shown in FIG. 1B, the punch 3 is set on the mold 1 and pressure is applied. The pressure is preferably set to 10 to 100 MPa so that the preform is sufficiently impregnated with the molten metal and the effect of crystal refinement is obtained. It is preferable to apply this pressure until the molten metal is completely solidified. Next, as shown in FIGS. 1 (c) and 1 (d), a forged material in which a metal composite 4 in which aluminum or an aluminum alloy is impregnated in a preform and a solidified molten metal 5 is integrally joined is obtained. The mold 1 is removed from the mold 1 by a knockout pin 6 arranged at the bottom of the mold 1. The metal composite 4 of this forged material has an Hv of 200 to
Although it has a hardness of about 400, it is not at a desired level as a sliding material for a brake as it is. Next, the forged material taken out is cut as shown in FIG. 1 (e) and cut into a brake rotor having a sliding surface 6 made of the sliding material for a brake of the present invention.

The brake rotor thus obtained is mounted on a vehicle such as an automobile and subjected to a heat treatment by utilizing the heat history of its use process, and titania or titanium metal is converted to aluminum as a matrix metal. To produce Al ₂ O ₃ and a Ti-Al metal compound,
The heat resistance and the hardness are increased, and the necessary and appropriate friction coefficient for the sliding material for the brake and the stabilization of the friction coefficient are secured.

Also, in the case of a brake drum having a sliding surface 6 made of the sliding material for a brake of the present invention, when traveling in combination with traffic congestion and high-speed traveling in an urban area and confirming the drum performance, the drum thermal history is confirmed. Surface hardness by temperature,
With respect to the change over time in the heat resistance temperature, the coefficient of friction and the like, the same results as those of the brake rotor were obtained.

[0027]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to Examples of the present invention and Comparative Examples thereof, but the present invention is not limited to these Examples.

Example 1 In the manufacturing method shown in FIG. 1, silica alumina fiber (SiO ₂ 50% by weight-A ₂ l) was used as the ceramic fiber.
O ₃ % by weight, average fiber diameter 5 μm, average length 5 mm), and anatase type titania particles (average particle diameter 1.6 μm) were used as the titania particles.
A is added as appropriate, so that the volume fraction of the ceramic fibers is 35%,
A preform having a volume ratio of titania particles of 2.5% was obtained.
After preheating this to 800 ° C., it was placed at a predetermined position in a mold for a brake rotor,
FIG. 1 is a diagram showing a φ (upper 250 mm, lower 145 mm) and a thickness (a thickness of the metal composite layer 4 of 7.5 mm and a thickness of the solidified molten metal layer 5 of 5 mm) by pouring a molten Mg alloy by weight and applying a pressure of 100 MPa. A casting shown in (d) was obtained. This was machined to obtain a brake rotor having a predetermined shape as shown in FIG. The hardness of the rotor surface of this brake rotor was Hv222 in the product state immediately after machining, and the surface temperature of the rotor was 448 when it was mounted on an actual vehicle and descended on a flat surface at an altitude of 195 m while applying a brake from a mountain at an altitude of 930 m.
° C, and the hardness of the rotor surface is measured again.
It became 1. Further, when traveling from the same mountain is repeated, the temperature becomes the same, and the hardness of the surface of the rotor further increases.
v403, Hv498, Hv583, Hv658, Hv
The result changed to 720 was obtained. Similarly, the coefficient of friction between the rotor and the friction material at that time, calculated from the braking force by a brake tester, is from 0.26 to 0.31,
It gradually changed to 0.34, 0.35, 0.36, 0.37, 0.37 and stabilized.

Further, the rotor manufactured in the same manner is mounted on an actual vehicle, and another two-seater state is set to another higher mountain (at an altitude of 1000).
m) for a long distance (820 m) and a long time (40 m
(Time) When descending while applying the brake, the surface temperature became 485 ° C., and when the surface hardness was measured again, the initial surface hardness was changed from Hv254 to Hv398. Furthermore, if the load is loaded from the same mountain and descends repeatedly at various speeds, the rotor surface temperature becomes 505 ° C, 662 ° C, 56 ° C.
0 ° C, 690 ° C, 724 ° C, and the surface hardness is Hv4
61, Hv517, Hv586, Hv653, Hv72
1 and the coefficient of friction between the rotor and the friction agent at that time is 0.31 to 0.33, 0.35, 0.3 from the initial value of 0.31.
It gradually changed to 7, 0.38, 0.39 and stabilized.

The running was further repeated, and the heat history time was 4,
Hv becomes 831 and 8 when accumulated for 5, 6, 7 and 8 hours.
76, 914, 958, and 1010, and the friction coefficients changed to 0.38, 0.39, 0.37, 0.38, and 0.38.

Finally, the mixture was heated with a burner and the melting temperature was examined. The temperature was found to be 1074 ° C. and 1103 ° C.

An air-cooled type rotor having a diameter of 210 mm manufactured in the same manner (only the outer diameter of the above rotor was changed, and 45 holes having a diameter of 5 mm were uniformly formed in the side wall of the rotor having the same structure except for the above. Thing) was produced.

FIG. 2 shows the results obtained by mounting the two types of brake rotors obtained above (solid and air-cooled) on an actual vehicle and measuring the relationship between heat history time and surface hardness, and between heat history time and friction coefficient. And FIG.

Example 2 A silica alumina fiber (SiO ₂₎ was used as the ceramic fiber.
50% by weight-50% by weight of A ₂ lO ₃ , average fiber diameter 5 μm,
Average length 5 mm), average particle diameter 1 as titanium metal powder
A preform having a volume ratio of ceramic fibers of 40% and a volume ratio of titanium powder of 2.5% was obtained by appropriately using an organic binder PVA having a particle size of 50 μm. This was preheated to 700 ° C. in argon, then placed at a predetermined position in a mold for the brake rotor, poured with 750 ° C. molten AC7A, and applied with a pressure of 80 MPa to make the outer diameter φ210 mm. A forged product similar to that of Example 1 was obtained. This was machined to obtain a brake rotor having a predetermined shape. The hardness of the rotor surface of the brake rotor was Hv368 in the product state immediately after machining, and the hardness of the rotor surface was 930 when mounted on an actual vehicle.
When a brake was applied from the top of the m mountain to a level surface at an altitude of 195 m while braking, the surface temperature became 516 ° C. When the hardness of the rotor surface was measured again, it became Hv 422. Further, when traveling from the same mountain is repeated, the temperature becomes 502 to 540 ° C., and the hardness of the surface of the rotor further increases.
1, Hv577, Hv629, Hv704, Hv758
And the changed result was obtained. Similarly, the coefficient of friction between the rotor and the friction material at that time, calculated from the braking force by a brake tester, is 0.32 to 0.35, 0.3
It gradually changed to 6, 0.37, 0.36, 0.38, 0.37 and stabilized.

Further, when the rotor produced in the same manner is mounted on an actual vehicle, and the vehicle is lowered while applying a brake for a long distance and a long time from another higher mountain in a two-seater state, the surface temperature becomes 485 ° C. When the surface hardness was measured, the initial surface hardness was changed from Hv388 to Hv424. Further, when the vehicle descends repeatedly from the same mountain at various speeds in a state of five-seater, the rotor surface temperature becomes 505
° C, 498 ° C, 662 ° C, 560 ° C, 690 ° C, 724 ° C
° C, and the hardness of the surface is Hv451, Hv487, Hv
546, Hv623 and Hv681, and the coefficient of friction between the rotor and the friction material at that time is 0.32 to 0.34, 0.35, 0.36, 0.37, 0.37 from the initial value of 0.32.
It gradually changed and became stable.

The running was further repeated, and the heat history time was 4,
Hv becomes 725, 7 when accumulated for 5, 6, 7, 8 hours.
53, 890, 912, and 932, and the coefficient of friction is 0.1.
37, 0.36, 0.37, 0.37, 0.36.

Finally, the mixture was heated with a burner and the melting temperature was examined. The temperature was 1074 ° C. and 1103 ° C.

Example 3 A silica alumina fiber (SiO ₂₎ was used as the ceramic fiber.
50% by weight-50% by weight of A ₂ lO ₃ , average fiber diameter 5 μm,
Using an average length of 5 mm), an organic binder PVA was appropriately added to obtain a preform having a ceramic fiber volume ratio of 40%. This was preheated to 900 ° C., then placed at a predetermined position in a mold for a brake rotor, poured into a 1000 ° C. molten Al-2 wt% Ti alloy, and subjected to a pressure of 80 MPa.
Was added to obtain a forged product having the same shape as in Example 1. This was machined to obtain a brake rotor having the same shape as in Example 1. The hardness of the rotor surface of this brake rotor, which was Hv398 in the product state immediately after machining, was lowered to 455 m on a flat surface at an altitude of 195 m while being mounted on an actual vehicle and applying a brake from a mountain at an altitude of 930 m.
° C, and the hardness of the rotor surface is measured again.
It became 9. Repeating the run from the same mountain further 45
The temperature becomes 9 to 522 ° C., and the hardness of the surface of the rotor further increases, and Hv542, Hv647, Hv694, Hv
After changing to 704 and Hv758, the result of Hv1056 was obtained after the heat history time of 8 hours. Similarly, the coefficient of friction between the rotor and the friction material at that time, calculated from the braking force by the brake tester, is 0.33 to 0.36, which is the initial value.
It gradually changed to 0.37, 0.37, 0.38, 0.39, 0.41 and stabilized. The stable results of the friction coefficient of 0.37 to 0.39 were obtained including the lapse of the heat history time of 8 hours.

An air-cooled type rotor having a diameter of 210 mm manufactured in the same manner (only the outer diameter of the above rotor was changed, and the other side of the rotor had a uniform diameter of 45 mm was provided on the side wall of the rotor. ) Is mounted on an actual vehicle, the number of passengers is changed to two or five, and the measurement is performed while changing the brake strength and the vehicle speed.
0 ° C. and the initial surface hardness Hv372 to Hv109
It became 9.

The friction coefficient between the rotor and the friction material at that time is 0.32 to 0.35, 0.36, 0.3 from the initial value.
It gradually changed to 7, 0.38, 0.38, 0.37 and stabilized. The coefficient of friction including the heat history time of 8 hours,
Stable results of 0.37 to 0.38 were obtained.

Finally, the mixture was heated with a burner and the melting temperature was examined. The temperatures were 958 ° C. and 866 ° C.

The two types of brake rotors (pure and air-cooled) obtained above were mounted on an actual vehicle, and the relationship between heat history time and surface hardness, and the relationship between heat history time and friction coefficient was measured. And FIG.

With the air-cooled type rotor manufactured by the manufacturing method of Example 3, the same surface hardness, heat resistance and friction coefficient as those of the solid type rotor manufactured by the manufacturing method of Examples 1 and 2 were obtained.

Comparative Example 1 A brake rotor having the same size and the same shape as those of Example 1 was obtained with an aluminum composite material (matrix: AC7A) containing 20% by volume of SiC particles (average particle size: 80 μm). . When the same brake operation as in Example 1 was performed on this rotor, the rotor melted at 405 ° C.

Comparative Example 2 A brake rotor having the same size and the same shape as those of Example 2 was obtained in the same manner as in Example 2 except that the metal titanium powder was not used at the time of forging. When a brake operation similar to that of the first embodiment is performed with the above-mentioned brake system, 520 is required on a downhill course.
At ℃, the surface of the rotor partially melted. The residual surface hardness is Hv
At 330, there was no change compared to before use.

[0046]

According to the present invention, a sliding material for a brake excellent in the performance required for the sliding material for a brake, in particular, hardness, heat resistance, abrasion resistance, an appropriate friction coefficient, and stability of the friction coefficient is obtained. Obtained.

Further, according to the present invention, the above-mentioned sliding material for a brake could be easily obtained.

Further, according to the present invention, a brake rotor and a brake drum having excellent hardness, heat resistance, abrasion resistance, an appropriate coefficient of friction, and stability of the coefficient of friction were obtained.

[Brief description of the drawings]

FIG. 1 is a side view showing steps of a first manufacturing method of the present invention.

FIG. 2 is a graph showing a relationship between heat history time and surface hardness of two types of brake rotors (pure and air-cooled) obtained in Example 1 and Example 3.

FIG. 3 is a graph showing a relationship between a heat history time and a friction coefficient of two types of brake rotors (solid and air-cooled) obtained in Example 1 and Example 3;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Preform 2 Mold 3 Punch 4 Metal composite 5 Solidified molten metal 6 Knockout pin 7 Sliding surface

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) F16D 65/12 F16D 65/12 U // C22C 21/00 C22C 21/00 E (C22C 49/14 (C22C 49/14 101: 00) 101: 00) (72) Inventor Masamichi Taoka 4-10-13-401, Mita, Minato-ku, Tokyo (72) Inventor Nobuyuki Suzuki 232-26, Ashikaga-Oue, Numazu City, Shizuoka Prefecture Technology F-term (reference) 3J058 BA31 BA41 BA76 CB11 EA02 EA14 EA17 EA36 4K020 AA02 AA04 AA05 AA06 AC01 BA02 BB05 BB26 BB41

Claims (7)

[Claims] 1. A metal obtained by impregnating a preform formed of ceramic fibers, carbon fibers, ceramic whiskers, ceramic particles or carbon particles with aluminum or aluminum alloy containing 0.5 to 5% by volume of titanium. A sliding material for brakes composed of a composite. 2. The sliding material for a brake according to claim 1, wherein the volume ratio of the preform is 10 to 50%. 3. A metal composite, comprising forming a preform with ceramic fibers, carbon fibers, ceramic whiskers, ceramic particles or carbon particles, and impregnating the preform with aluminum or an aluminum alloy by molten forging. A method for manufacturing a sliding material for a brake made of a body. 4. A preform is formed from ceramic fibers, carbon fibers, ceramic whiskers, ceramic particles or carbon particles and titanium metal powder, and the preform is impregnated with aluminum or an aluminum alloy by melt forging. A method for producing a sliding material for a brake comprising a metal composite. 5. A preform is formed from ceramic fibers, carbon fibers, ceramic whiskers, ceramic particles or carbon particles, and the preform is impregnated with titanium metal and aluminum or an aluminum alloy by melt forging. Of producing a sliding material for a brake made of a metal composite. 6. A brake rotor having a sliding surface made of the brake sliding material according to claim 1. 7. A brake drum having a sliding surface made of the sliding material for a brake according to claim 1.