Powder metallurgy friction material, method for producing the same, and use thereof

Abstract

The application belongs to the technical field of powder metallurgy friction material preparation, and particularly relates to a powder metallurgy friction material, a preparation method and application thereof. The application takes metal oxides as raw materials of the powder metallurgy friction material, and the obtained friction material has good high-temperature performance, does not have the problem of softening of a metal matrix in a high-speed braking process, has stable friction coefficient, and can reduce the production cost of the friction material by replacing part of copper powder with metal oxides.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of powder metallurgy friction material, and particularly relates to a powder metallurgy friction material and a preparation method and application thereof. BACKGROUND

[0002] Friction material is a structure-function composite material which converts kinetic energy of moving objects into heat energy by using friction force generated by contact with a counter material, and is one of indispensable materials in brakes, clutches and friction transmission devices of various mechanical equipment. Friction stability, wear resistance, heat resistance and fatigue resistance of the friction material determine whether the equipment can run smoothly and safely.

[0003] With more frequent population, economy and production factors, higher and higher requirements are put forward for the speed of railway transportation. The polymer synthetic material used in the high-speed train with a speed lower than 250 km / h in the past cannot meet the requirements of braking of the vehicle with higher speed due to low strength, poor heat resistance and serious heat recession. The brake pad mainly used in the high-speed train with a speed higher than 250 km / h at present is a copper-based powder metallurgy friction material with high heat conduction, good heat resistance and high friction coefficient. The matrix of the material is mainly copper supplemented with a small amount of iron, so that the requirements of heat conduction and strength can be well met.

[0004] However, under the condition of a speed higher than 250 km / h, on the one hand, the copper-based powder metallurgy friction material is affected by friction heat, which leads to softening of the metal matrix and instability of the friction coefficient. The existing technology enhances the high-temperature stability of the copper-based friction material by adding rod-shaped molybdenum trioxide composite particles, but for the copper-based powder friction material, the composition is complex, the non-metal raw material interrupts the continuous morphology of the metal matrix, and the high-temperature mechanical properties of the matrix decrease. On the other hand, due to poor wettability of graphite or ceramic particles and the copper matrix, there are many pores or cracks at the phase interface. These defects develop into fatigue cracks under the cyclic action of severe friction thermal stress and friction shear stress in the process of high-speed braking, and continuously proliferate and develop, leading to serious wear of the material and further causing the friction stability of the friction material to decrease.

[0005] Further, the main components of the copper-based powder metallurgy friction material in the prior art are copper powder and iron powder, and the prices of the copper powder and the iron powder have been rising in recent years, which greatly increases the production cost of the friction material. Under the premise of ensuring the friction coefficient, selecting a low-cost raw material becomes one of the problems in the field of friction materials. SUMMARY

[0006] Therefore, the present application aims to overcome the defects of the prior art, i.e., the unstable friction performance of the copper matrix powder metallurgy friction material and the high production cost of the friction material due to the use of copper and iron as the main raw materials, and to provide a powder metallurgy friction material, a preparation method and application thereof.

[0007] To this end, the present application provides the following technical solutions.

[0008] The present application provides an application of a metal oxide in the preparation of a powder metallurgy friction material.

[0009] The metal oxide includes copper oxide and iron oxide;

[0010] Optionally, the copper oxide includes copper oxide and cuprous oxide;

[0011] The iron oxide includes diiron trioxide and ferroferric oxide.

[0012] In addition, the present application also provides a powder metallurgy friction material, the raw materials of which include copper powder and metal oxide powder.

[0013] The metal oxide powder includes copper oxide powder and iron oxide powder;

[0014] The mass ratio of the copper powder, the copper oxide powder and the iron oxide powder is (15-20):(22-45):(20-50).

[0015] The copper oxide includes copper oxide powder and cuprous oxide powder;

[0016] The mass ratio of the copper powder, the copper oxide and the cuprous oxide is (15-20):(2.5-10):(20-35);

[0017] The iron oxide includes diiron trioxide powder and ferroferric oxide powder;

[0018] The mass ratio of the copper powder, the diiron trioxide powder and the ferroferric oxide powder is (15-20):(10-25):(10-25).

[0019] The raw materials of the powder metallurgy friction material further include chromium powder and / or iron powder;

[0020] The mass ratio of the copper powder and the chromium powder is (15-20):(5-8);

[0021] The mass ratio of the copper powder and the iron powder is (15-20):(0-10).

[0022] The raw materials of the powder metallurgy friction material further include polyethylene glycol;

[0023] The mass ratio of the copper powder to the polyethylene glycol is (15-20):(0.5-6).

[0024] Optionally, the raw material of the powder metallurgy friction material further comprises a lubricant, and the mass ratio of the lubricant to the copper powder is (3-20):(15-20).

[0025] The lubricant is graphite and / or molybdenum disulfide.

[0026] The raw material of the powder metallurgy friction material comprises copper powder, copper oxide powder, cuprous oxide powder, ferric sesquioxide powder, magnetite powder, chromium powder, graphite and polyethylene glycol, and the mass ratio of the copper powder to the copper oxide powder to the cuprous oxide powder to the ferric sesquioxide powder to the magnetite powder to the chromium powder to the graphite to the polyethylene glycol is (15-20):(2.5-10):(20-35):(10-25):(10-25):(5-8):(3-20):(0.5-6).

[0027] Further, the application provides a preparation method of the powder metallurgy friction material, comprising the following steps,

[0028] After the raw materials are mixed, the green body is obtained through pressing;

[0029] The powder metallurgy friction material is obtained after the green body is sintered.

[0030] The pressure of the pressing is 100-600 MPa.

[0031] The specific steps of the sintering include sintering for 0.5-2 h after the temperature is raised to 950-1050 ℃ at a temperature raising rate of 1-10 ℃ / min.

[0032] Further, the application provides a preparation method of the powder metallurgy friction material, comprising the following steps,

[0033] The other raw materials except the graphite are preliminarily mixed, and then mixed uniformly with the graphite in a ball mill mixer to obtain a mixed powder; wherein the ball-to-material ratio is 1:(3-10), the ball material is a steel ball, the ball milling medium is anhydrous ethanol, the ball milling atmosphere is argon, the ball milling time is 2-5 h, and the rotation speed is 30-180 rpm.

[0034] The mixed powder is pressed with a backing plate of the friction block under a pressure of 100-600 MPa to obtain a green body.

[0035] The powder metallurgy friction material is obtained after the green body is sintered.

[0036] In addition, the application further provides an application of the powder metallurgy friction material or the powder metallurgy friction material prepared by the method in a disc-type braking device of a high-speed train.

[0037] The technical scheme of the application has the following advantages:

[0038] 1. The application provides the application of metal oxide in powder metallurgy friction material, the metal oxide is used as the raw material of the powder metallurgy friction material, the high-temperature performance of the obtained friction material is good, the problem of softening of the metal matrix does not occur in the high-speed braking process, the friction coefficient is stable, and the production cost of the friction material can be reduced by replacing part of copper powder with the metal oxide.

[0039] 2. The powder metallurgy friction material provided by the application has stable high-temperature performance (anti-softening performance) and stable friction coefficient in the high-speed braking process, and the production cost of the friction material is lower than that of the copper-based powder metallurgy friction material in the prior art. The metal oxide powder is used in the preparation of the friction material, and cooperates with the copper powder, so that the friction coefficient stability of the friction material is improved, and the production cost is reduced. The metal oxide powder cooperates with the copper powder, so that the problem of poor compactness of the friction material obtained by using the metal oxide as the raw material is overcome, and the problems of high cost of copper powder and softening of the metal matrix caused by friction heat in high-speed braking, and instability of the friction coefficient are overcome.

[0040] Copper and oxide are main components of the friction material, and the two are used as the bearing lubricating component and the friction component of the matrix, copper can promote sintering compactness, increase the strength of the matrix after sintering, and the oxide provides stable mechanical properties and friction properties for the matrix. The powder metallurgy friction material provided by the application can be used as a brake pad, and the friction coefficient has a small change range and good stability under different braking speeds.

[0041] 3. The powder metallurgy friction material provided by the application has stable friction coefficient stability, and the production cost is lower than that of the copper-based powder metallurgy friction material in the prior art. The metal oxide powder is used in the preparation of the friction material, and cooperates with the copper powder, so that the friction coefficient stability of the friction material is improved, and the production cost is reduced. The metal oxide powder cooperates with the copper powder, so that the problem of poor compactness of the friction material obtained by using the metal oxide as the raw material is overcome, and the problems of high cost of copper powder and softening of the metal matrix caused by friction heat in high-speed braking, and instability of the friction coefficient are overcome.

[0042] By controlling the proportion of copper, copper oxide and iron oxide, the combination firmness of the matrix can be ensured, when the amount of copper is relatively large, the friction coefficient stability of the friction material will decrease; by controlling the amount of copper oxide and iron oxide, the friction stability can be improved, and too high or too low amount of copper oxide and iron oxide is not conducive to sintering into a firm friction material.

[0043] The application of the specific metal oxide and copper can also overcome the defects that graphite and the like in the prior art have poor lubricity with the copper matrix, cracks occur in the friction material in the high-speed braking process, and the friction coefficient is unstable.

[0044] 4. The powder metallurgy friction material provided by the present application can increase the friction force of the material by adding chromium powder; when the material is used in a braking device, the added lubricant can prevent the brake pad from being welded to the brake disc, reduce braking noise, and stabilize the braking process. The addition of polyethylene glycol in the friction material can facilitate the molding of the friction material. BRIEF DESCRIPTION OF DRAWINGS

[0045] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the following will briefly introduce the drawings needed to be used in the specific embodiments or prior art description. Obviously, the drawings described below are some embodiments of the present application, and those skilled in the art can also obtain other drawings according to these drawings without creative labor.

[0046] Figure 1 The friction coefficient of the friction material of the present application and the comparative example at different braking speeds. DETAILED DESCRIPTION

[0047] The following examples are provided to better further understand the present application and are not limited to the best mode, and do not limit the content and protection scope of the present application. Any product that is the same or similar to the present application obtained by the inspiration of the present application or the combination of the present application with other prior art features falls within the protection scope of the present application.

[0048] If the specific experimental steps or conditions are not specified in the examples, the operation or conditions can be carried out according to the conventional experimental steps described in the literature in the art. If the reagents or instruments are not specified by the manufacturer, they are conventional reagent products that can be obtained by purchase.

[0049] Example 1

[0050] The present example provides a powder metallurgy friction material, the raw materials of which include 15 g of copper powder, 10 g of copper oxide powder, 20 g of cuprous oxide powder, 25 g of ferric oxide powder, 10 g of ferric oxide powder, 8 g of chromium powder, 3 g of graphite, and 5 g of polyethylene glycol.

[0051] The preparation method of the above-mentioned powder metallurgy friction material comprises the following steps,

[0052] The above-mentioned raw materials except graphite are mixed, and after being preliminarily mixed uniformly by a high-speed stirrer, they are placed in a ball mill, and then graphite is added to the ball mill for ball milling for 2 h, the rotation speed is 180 rpm, the ball-to-material ratio is 1:10, the ball milling material is a steel ball, the ball milling medium is anhydrous ethanol, and the ball milling medium is argon, to obtain a mixed powder;

[0053] The mixed powder is pressed with a friction block back plate under a pressure of 600 MPa to obtain a green body;

[0054] The green body is sintered to obtain the friction material, wherein the sintering is completed by heating to 1050℃ at a heating rate of 1℃ / min and keeping for 0.5h.

[0055] Example 2

[0056] The present example provides a powder metallurgy friction material, raw materials of which include 18g copper powder, 5g copper oxide powder, 35g cuprous oxide powder, 10g ferric sesquioxide powder, 25g ferric trioxide powder, 5g chromium powder, 20g graphite and 0.5g polyethylene glycol.

[0057] The preparation method of the powder metallurgy friction material includes the following steps,

[0058] The raw materials except graphite are mixed, and then uniformly mixed by a high-speed stirrer. The mixture is placed in a ball mill, and then graphite is added into the ball mill for ball milling for 5h at a speed of 30rpm, a ball-to-material ratio of 3:10, a ball material of steel ball, a ball milling medium of anhydrous ethanol, and a ball milling medium of argon. The mixed powder is obtained.

[0059] The mixed powder is pressed with a friction block back plate under a pressure of 100MPa to obtain a green body.

[0060] The green body is sintered to obtain the friction material, wherein the sintering is completed by heating to 950℃ at a heating rate of 10℃ / min and keeping for 2h.

[0061] Example 3

[0062] The present example provides a powder metallurgy friction material, raw materials of which include 16g copper powder, 8g copper oxide powder, 28g cuprous oxide powder, 17g ferric sesquioxide powder, 20g ferric trioxide powder, 7g chromium powder, 15g graphite and 2g polyethylene glycol.

[0063] The preparation method of the powder metallurgy friction material includes the following steps,

[0064] The raw materials except graphite are mixed, and then uniformly mixed by a high-speed stirrer. The mixture is placed in a ball mill, and then graphite is added into the ball mill for ball milling for 3h at a speed of 100rpm, a ball-to-material ratio of 2:10, a ball material of steel ball, a ball milling medium of anhydrous ethanol, and a ball milling medium of argon. The mixed powder is obtained.

[0065] The mixed powder is pressed with a friction block back plate under a pressure of 400MPa to obtain a green body.

[0066] The green body is sintered to obtain the friction material, wherein the sintering is completed by heating to 1000℃ at a heating rate of 6℃ / min and keeping for 2h.

[0067] Example 4

[0068] The embodiment provides a powder metallurgy friction material, raw materials of which include 20 g of copper powder, 2.6 g of copper oxide powder, 27 g of cuprous oxide powder, 15.2 g of diiron trioxide powder, 15.2 g of ferriferrous oxide powder, 10 g of chromium powder, 10 g of graphite and 1 g of polyethylene glycol.

[0069] The preparation method of the powder metallurgy friction material comprises the following steps,

[0070] The other raw materials except the graphite are mixed, and then are uniformly mixed by a high-speed stirrer, and are placed in a ball mill, and then the graphite is added into the ball mill for ball milling for 3.5 h, a rotating speed is 50 rpm, a ball-to-material ratio is 2:10, a ball milling material is a steel ball, a ball milling medium is anhydrous ethanol, and a ball milling medium is argon, so that the mixed powder is obtained;

[0071] The mixed powder is pressed under the pressure of 270 MPa with a friction block back plate, so that a green body is obtained.

[0072] The green body is sintered, so that the friction material is obtained, wherein the sintering is completed by heating to 950 ℃ at a heating rate of 5 ℃ / min and then keeping the temperature for 2 h.

[0073] Example 5

[0074] The embodiment provides a powder metallurgy friction material, raw materials of which include 20 g of copper powder, 2.6 g of copper oxide powder, 27 g of cuprous oxide powder, 15.2 g of diiron trioxide powder, 15.2 g of ferriferrous oxide powder, 10 g of chromium powder, 10 g of graphite and 1 g of polyethylene glycol.

[0075] The preparation method of the powder metallurgy friction material comprises the following steps,

[0076] The other raw materials except the graphite are mixed, and then are uniformly mixed by a high-speed stirrer, and are placed in a ball mill, and then the graphite is added into the ball mill for ball milling for 2 h, a rotating speed is 180 rpm, a ball-to-material ratio is 1:10, a ball milling material is a steel ball, a ball milling medium is anhydrous ethanol, and a ball milling medium is argon, so that the mixed powder is obtained;

[0077] The mixed powder is pressed under the pressure of 600 MPa with a friction block back plate, so that a green body is obtained.

[0078] The green body is sintered, so that the friction material is obtained, wherein the sintering is completed by heating to 1050 ℃ at a heating rate of 1 ℃ / min and then keeping the temperature for 0.5 h.

[0079] Comparative Example 1

[0080] The embodiment provides a powder metallurgy friction material, raw materials of which include 20 g of copper powder, 2.6 g of copper oxide powder, 27 g of cuprous oxide powder, 15.2 g of diiron trioxide powder, 15.2 g of ferriferrous oxide powder, 10 g of chromium powder, 10 g of graphite and 1 g of polyethylene glycol.

[0081] The method for preparing the powder metallurgy friction material comprises the following steps,

[0082] The other raw materials except graphite are mixed, and then uniformly mixed by a high-speed stirrer, and then placed in a ball mill, and then graphite is added into the ball mill for ball milling for 2 hours at a rotating speed of 180 rpm, a ball-to-material ratio of 1:10, a ball milling material of steel ball, a ball milling medium of anhydrous ethanol, and a ball milling medium of argon, to obtain a mixed powder;

[0083] The mixed powder is pressed with a friction block back plate under a pressure of 600 MPa to obtain a green body.

[0084] The green body is sintered to obtain the friction material, wherein the sintering is completed by heating to 1050℃ at a heating rate of 1℃ / min and keeping for 0.5 hours.

[0085] Test Example

[0086] The test example provides performance tests and test results of the powder metallurgy friction materials obtained in Examples 1-5 and Comparative Example 1.

[0087] The test method for the friction coefficient of the powder metallurgy friction material is that a Xi'an Shuntong TM-1 type rail train inertia braking scaled test bench is used as a test instrument, and braking tests are respectively performed at different speeds; the braking process is that a rotating shaft drives an inertia disc and a brake disc to accelerate to a test speed, a brake caliper presses brake pads (the friction materials prepared in the examples and the comparative example) on the surface of the brake disc at a rated pressure to brake, until the rotating disc stops rotating; wherein the braking pressure is 1.37 MPa, the initial temperature is 50-60℃, and the rotational inertia is 27 kg·m; the friction coefficients of the friction materials of the examples and the comparative example at different braking speeds are shown in Table 1. Figure 1 and Table 1.

[0088] Table 1 shows the performance test results of the powder metallurgy friction materials of the examples and the comparative example.

[0089]

[0090]

[0091]

[0092] The maximum friction coefficient is the maximum friction coefficient of the friction material at different braking speeds; and the minimum friction coefficient is the minimum friction coefficient of the friction material at different braking speeds.

[0093] Figure 1 The friction coefficient of the friction material at different braking speeds is obtained by Figure 1 It can be seen that the friction materials provided in the examples have stable friction coefficients at different braking speeds, and the fluctuation is small.

[0094] By Figure 1 It can also be seen that the friction material of Comparative Example 1 has a high friction coefficient at the initial braking speed, but the friction coefficient decreases greatly with the increase of the speed; compared with Comparative Example 1, the addition of metal oxides in the friction material of the application can improve the stability of the friction coefficient of the friction material; and the use of metal oxides instead of copper powder can significantly reduce the production cost.

[0095] When the copper powder, copper oxide powder, cuprous oxide powder, ferric sesquioxide powder, ferroferric oxide powder, chromium powder, graphite and polyethylene glycol are used in a mass ratio of 20:2.6:27:15.2:15.2:10:10:1, the friction stability of the powder metallurgy friction material obtained is optimal.

[0096] Obviously, the above examples are only examples for clearly illustrating, but not limit the embodiments. For those skilled in the art, other different forms of changes or variations can be made on the basis of the above description. Here, it is not necessary and impossible to enumerate all the embodiments. The obvious changes or variations derived therefrom are still within the protection scope of the present application.

Claims

1. A powder metallurgical friction material, characterized in that, The raw materials include copper powder and metal oxide powder; the metal oxide powder includes copper oxide powder and iron oxide powder; The mass ratio of the copper powder, copper oxide powder and iron oxide powder is (15-20):(22-45):(20-50); The copper oxide includes copper oxide powder and cuprous oxide powder; The mass ratio of the copper powder, copper oxide and cuprous oxide is (15-20):(2.5-10):(20-35); The iron oxide includes diiron trioxide powder and magnetite powder; The mass ratio of the copper powder, diiron trioxide powder and magnetite powder is (15-20):(10-25):(10-25).

2. The powder metallurgical friction material according to claim 1, characterized in that The raw materials further include chromium powder and / or iron powder.

3. The powder metallurgical friction material according to claim 2, characterized in that The mass ratio of the copper powder and chromium powder is (15-20):(5-8); The mass ratio of the copper powder and iron powder is (15-20):(0-10).

4. The powder metallurgical friction material according to any one of claims 1 - 3, c h a ra cte ri zed i n that The raw materials further include polyethylene glycol; The mass ratio of the copper powder and polyethylene glycol is (15-20):(0.5-6).

5. The powder metallurgical friction material according to claim 4, characterized in that The raw materials of the powder metallurgy friction material further include lubricant, and the mass ratio of the lubricant and copper powder is (3-20):(15-20).

6. A method of producing the powder metallurgical friction material according to any one of claims 1 to 5, characterized in that The method includes the following steps, After mixing the raw materials, the green body is obtained by pressing; The powder metallurgy friction material is obtained by sintering the green body.

7. The production method according to claim 6, wherein The pressure of the pressing is 100-600MPa; The specific steps of the sintering include sintering for 0.5-2h after heating to 950-1050℃ at a heating rate of 1-10℃ / min.

8. The use of the powder metallurgy friction material of any one of claims 1-5 or the powder metallurgy friction material prepared by the method of any one of claims 6-7 in high-speed train disc brake device.

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