JP2007162779A - Disk rotor for brake - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a disk rotor for a brake, which is excellent in wear resistance, heat resistance, and economy. <P>SOLUTION: The disk rotor for the brake has a laminated coating layer formed so as to be closely laminated on the surface of a disk rotor body made of cast iron or steel by spraying the mixed powder of WC-C base cermet powder and Fe-C base material powder by the high speed flame spraying method by dividing the layer into a plurality of layers such that the mixed volume ratio of the WC-C base cermet powder and Fe-C base powder increases from the disk rotor body side toward the surface side. In addition, it is preferable that the disk rotor has the coating layer formed by spraying the mixed powder so as to have a small mixed volume ratio of 0.25 to 1.0 on the disk rotor body side and a large mixed volume ratio of 1.0 to 9.0 on the surface side, and the total thickness of the laminated coating layer is 50 to 500 μm. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a brake disk rotor that is used in automobiles, two-wheeled vehicles, railway vehicles, industrial machines, and the like and is excellent in heat resistance, wear resistance, and economy.

  Conventionally, a brake disc rotor for an automobile is made of cast iron from the viewpoints of heat resistance, wear resistance, price, ease of manufacturing process, inexpensive material characteristics, and the like. This utilizes the wear resistance and heat resistance of cast iron and the low cost of manufacturing costs.

  However, due to recent advances in automobile technology and the spread of outdoor sports and racing, there is a demand for more stable braking performance at high speed and improved wear resistance of the disk rotor.

In order to improve the heat resistance of the disk rotor, brake disk rotors using C / C composites or SiC-based ceramic composites (CMC) instead of cast iron have already been put into practical use. There is a drawback. Accordingly, a surface clad material in which a hardened layer is provided on the surface of a cast iron disk rotor to improve heat resistance and wear resistance has attracted attention. As a method for generating the clad layer, a thermal spraying method is promising in consideration of the area of the disk rotor, the generation rate of the coating film, and the cost of the apparatus, but the conventional atmospheric plasma method (Patent Document 1) and arc method (Patent Document 2), In the frame method (Patent Document 3) and the like, when the disk rotor becomes high temperature due to the difference in thermal contraction rate and elastic modulus between the base layer and the surface layer, it is easy to cause peeling of the interface and cracking of the surface layer. There is a problem. Such a problem stems from the fact that the heat resistance and wear resistance required for the disk rotor are very severe compared to other sliding members.
JP-A-5-44753 Japanese Patent No. 27679888 Japanese Patent Laid-Open No. 5-263852

  Due to the speeding up of automobiles, brakes used in outdoor sports and racing are subject to severe conditions such as braking from 200 km / h, and the disk rotor temperature reaches 800 ° C to 900 ° C by repeated braking. Therefore, it is necessary to exhibit stable friction characteristics and excellent wear resistance even in such a temperature range.

  The present invention has been made for the purpose of solving the above-mentioned problems, and provides a brake disk rotor that is excellent in heat resistance and wear resistance at high temperatures and excellent in economy.

  Due to the above-mentioned problems, the present inventors have not added a surface layer that easily causes separation or cracking of the interface when the disk rotor becomes high temperature, and the disk rotor temperature reaches 800 ° C. to 900 ° C. Therefore, various studies were made on disc rotors made of materials that do not cause friction coefficient reduction or increase in wear even during braking, and that do not cause friction coefficient instability or abnormal vibration due to rust on the disc rotor sliding surface.

  The present inventors have already proposed a Fe-based surface clad disk rotor using a high-speed flame spraying method (see Japanese Patent Application No. 2004-310594), which emphasizes improvement of general brake performance. Therefore, in brakes used in outdoor sports and racing, it may be difficult to sufficiently satisfy the high temperature friction characteristics.

Therefore, the mixing ratio of the WC-Co-based cermet powder and the Fe-C-based material powder in the Fe-based surface-clad disk rotor changes in the thickness direction and goes from the disk rotor main body side (base side) to the surface side. If the disk rotor main body side is provided with a small layer and a surface layer with a large layer, the heat resistance and wear resistance of the disk rotor at high speed can be improved. The present invention has been achieved by paying attention to the above.
That is, by changing the mixing ratio of the WC-Co-based cermet powder and the Fe-C-based material powder on the disk rotor main body side and the surface side, the ratio of the Fe-C-based material powder is high on the main body side. Since the thermal expansion coefficient of the clad layer is not significantly different from that of the clad layer, it is possible to prevent the peeling and cracking of the interface at high temperatures, and the surface side has a high ratio of WC-Co cermet powder, so heat resistance and wear resistance at high speed It became possible to secure sex.

That is, the present invention achieves the above object by the following means.
(1) A mixed powder of WC-Co cermet powder and Fe-C material powder is moved from the disk rotor body side to the surface side by a high-speed flame spraying method on the surface of the disk rotor body made of cast iron or steel. Therefore, a brake having a multilayer coating layer formed by thermal spraying into a plurality of layers and closely laminating so as to increase the mixing volume ratio of the WC-Co cermet powder and the Fe-C powder. Disc rotor.
(2) Thermal spraying was performed by dividing the mixing volume ratio of the mixed powder into two layers of a small layer of 0.25 to 1.0 on the disk rotor body side and a large layer of 1.0 to 9.0 on the surface side. The brake disk rotor according to (1) above, which has a multilayer coating layer formed in the above manner.
(3) The brake disk rotor according to (1) or (2), wherein the total thickness of the multilayer coating layer is 50 μm to 500 μm.

The configuration of the brake disc rotor will be described with reference to the drawings. The brake disc rotor of (1) has the configuration shown in FIG. 1, and the brake disc rotor of (2) is shown in FIG. It has the structure shown.
In FIGS. 1 and 2, 1 is a coating layer on the surface side where the mixed volume ratio (WC-Co / Fe-C) of the mixed powder is 1.0 to 9.0, and 2 is the main body side. The disk rotor body side (base side) having a mixing volume ratio intermediate between the mixing volume ratio and the mixing volume ratio on the surface side, 3 is an intermediate layer having a mixing volume ratio of 0.25 to 1.0, Reference numeral 4 denotes a disc rotor body made of cast iron or steel.

  The disc rotor for brake according to the present invention has excellent wear resistance and stability of friction coefficient even in a severe brake test in which the maximum reached temperature of the disc rotor reaches 800 ° C. to 900 ° C. This is effective for stabilizing the friction characteristics of automobile brakes.

  The high-speed flame spraying method is an inexpensive and simple surface clad method that does not require expensive equipment and running costs compared to the PVD method, laser or plasma spraying method, explosive welding method, etc. The surface film is completely adhered without any defects, and the thermal expansion coefficient of the base material and the thermal spray material is close so that they do not peel off during use.

  High-speed flame spraying is a method in which a high-pressure combustion gas is used and a coating is formed by spraying a powdered thermal spray material at a gas flow rate exceeding the speed of sound. The coating has few pores in the coating and has excellent adhesion to the substrate. In particular, WC-Co-based materials are excellent in adhesion to cast iron materials and steel materials.

  Here, cast iron refers to cast iron materials such as gray cast iron, ductile cast iron, malleable cast iron, etc., which are conventionally used for disk rotors, and steel materials are carbon steel, alloy steel, steel for machine structure, It refers to stainless steel.

  The WC-Co powder has a Co content of 3 to 30%, preferably 7 to 20%, and preferably has a low hardness in order to suppress the wear amount of the friction material. The Fe-C powder may contain appropriate amounts of Si and Mn and others. If the amount of C in the Fe-C powder is less than 0.02%, the strength is greatly reduced at a high temperature, and the friction coefficient is lowered. When the mixing volume ratio (WC-Co / Fe-C) of the WC-Co powder and the Fe-C powder is less than 0.25, the strength at high temperature is low and the mixing effect of the WC-Co powder is not recognized. If it exceeds 0.0, cracks occur in the disk rotor surface layer when braking at high temperature is repeated for a long time.

  The mixing volume ratio of the WC-Co powder and the Fe-C powder is a small layer of 0.25 to 1.0 on the disk rotor body side (base side), and a large layer of 1.0 to 9.0 on the surface side, Preferably, it is desirable to use a small layer of 0.25 to 0.54 on the main body side (base side) and a large layer of 3.0 to 9.0 on the surface side. Moreover, it is desirable that the amount of C of Fe-C powder is 0.02% to 1.0%, more preferably 0.02% to 0.8% on the main body side, and Fe-C powder is on the surface side. It is desirable that the C content is 1.0% to 5.0%, more preferably 2.5% to 5.0%. As an example of the method of spraying while changing the material, each time one layer is sprayed, the powder in the hopper of the spray material supply unit is replaced to perform spraying. Further, as the spray material changes, the spraying conditions are also changed little by little every time one layer is sprayed.

  Further, it is desirable to use a thermal spray powder having a diameter of 5 to 60 μm and appropriately perform pre-heat treatment and undercoat treatment.

  The total thickness of the multi-layer coating layer is desirably 50 μm to 500 μm, preferably 50 μm to 200 μm. When the thickness exceeds 500 μm, even in the case of a multi-layered type, separation of the interface and cracking of the surface layer are liable to occur during high-speed brake braking due to differences in thermal contraction rate and elastic modulus of each layer. As a heat source for thermal spraying, a mixed gas of oxygen and hydrocarbon gas and air and oxygen is used. In addition, blasting is performed as pretreatment, but care is taken so that the blasting material does not remain as a defect at the interface with the surface layer.

  The present invention will be described based on the results of a brake performance test using an actual disk rotor. However, the present invention is not limited to only these examples.

(Test method)
A real disk rotor was made of cast iron and steel, and a brake performance test (dynamometer test, etc.) was performed by spraying a mixed powder of WC-Co powder and Fe-C powder on the sliding surface by high-speed flame spraying. The actual disk rotor is a disk brake disk rotor for ventilated medium-sized passenger cars having a shape of 280 mmφ × 23 mm thickness. As the friction material, a non-asbestos friction material generally used for passenger cars was used. Table 1 shows the main components of the friction material. Moreover, the test pattern assumed the outdoor sports and the racing, and the test of the test pattern for evaluating the friction characteristic in the rotor maximum temperature 800-900 degreeC was done.

  The test pattern is shown in Table 2. The braking start temperature was set to 500 ° C. so that the maximum reached temperature of the disk rotor was 800 to 900 ° C., and the high speed test 200 km / h (5 braking) was set to 1 cycle, and 5 cycles were repeated. Table 3 shows the chemical components of the material of the present invention. Table 3 also shows the thermal spray material components used in the test. No. 1-2 show the case where a base material is cast iron. No. 1 and 2 are both high-speed flame sprayed mixed powders of WC-Co powder and Fe-C powder. No. Reference numeral 3 is a single layer, which is a comparative material outside the scope of the present invention. No. 4 is a conventional graphite cast iron (FC250).

  Before spraying, a brazing treatment using alumina and a preheat treatment at 200 ° C. were performed. After thermal spraying, the surface was ground to Rz <5 μm.

(Test results)
The test results are summarized in Table 4. Moreover, the result of a friction coefficient is shown in FIG. All of the materials of the present invention are excellent in heat resistance, wear resistance, and corrosion resistance as disk rotor materials, and disk rotors with laminated coating have friction characteristics compared to conventional materials and disk rotors with a single layer coating. It can be confirmed that it is excellent.

  The brake disk rotor of the present invention is superior to conventional cast iron brake disk rotors in friction characteristics, heat resistance, and corrosion resistance, so it is useful for brakes in automobiles, motorcycles, railway vehicles, industrial machines, etc. It is.

It is sectional drawing of the disk rotor for brakes sprayed in several layers. It is sectional drawing of the disc rotor for brakes sprayed in two layers. It is a graph which shows the measurement result of the friction coefficient of a real disk rotor evaluation test.

Explanation of symbols

1 Surface side 2 Intermediate layer 3 Disc rotor body side (underground side)
4 Disc rotor body

Claims (3)

  A mixed powder of WC-Co cermet powder and Fe-C material powder is transferred from the disk rotor body side to the surface side by a high-speed flame spraying method on the surface of the disk rotor body made of cast iron or steel. A brake disk rotor having a laminated coating layer formed by spraying in multiple layers and closely laminating so as to increase the mixing volume ratio of Co-based cermet powder and Fe-C powder. .   The mixing volume ratio of the mixed powder was formed by spraying into two layers of a small layer of 0.25 to 1.0 on the disk rotor body side and a large layer of 1.0 to 9.0 on the surface side. The brake disk rotor according to claim 1, further comprising a multilayer coating layer.   The brake disk rotor according to claim 1 or 2, wherein the total thickness of the multilayer coating layer is 50 µm to 500 µm.

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