阅读说明：本技术 一种高熔点合金增强铜基粉末冶金摩擦材料及其制备方法 (High-melting-point alloy reinforced copper-based powder metallurgy friction material and preparation method thereof ) 是由 庾正伟 田雅萍 宋川 王型俊 徐腈蔓 于 2021-06-23 设计创作，主要内容包括：本发明公开了一种高熔点合金增强铜基粉末冶金摩擦材料及其制备方法铜基粉末冶金摩擦材料由以下重量百分比的原料制成：铜粉50～60％,铁粉10～20％,锆2～4％,钨2～4％,铬2～4％,石墨10～15％,陶瓷颗粒5～10％,二硫化钼1～2％,高碳铬铁2～4％。本发明的积极效果是：解决了粉末冶金闸片在高速下制动时摩擦系数衰退严重和磨损量大的问题,具体优点为：本发明用锆、铬、钨三种高熔点合金强化了铜基粉末冶金摩擦材料,提高了铜基体软化失效的温度,减小了材料高速制动时摩擦系数的衰退。本发明的铜基粉末冶金摩擦材料提高了材料的硬度和强度,同时降低了摩擦材料制动时的磨损量,提高了粉末冶金闸片的使用寿命。(The invention discloses a high-melting-point alloy reinforced copper-based powder metallurgy friction material and a preparation method thereof, wherein the copper-based powder metallurgy friction material is prepared from the following raw materials in percentage by weight: 50-60% of copper powder, 10-20% of iron powder, 2-4% of zirconium, 2-4% of tungsten, 2-4% of chromium, 10-15% of graphite, 5-10% of ceramic particles, 1-2% of molybdenum disulfide and 2-4% of high-carbon ferrochrome. The invention has the positive effects that: the problems of serious decline of friction coefficient and large abrasion loss of the powder metallurgy brake pad during braking at high speed are solved, and the brake pad has the following specific advantages: the invention uses three high-melting point alloys of zirconium, chromium and tungsten to strengthen the copper-based powder metallurgy friction material, improves the softening failure temperature of the copper matrix, and reduces the decline of the friction coefficient when the material is braked at high speed. The copper-based powder metallurgy friction material improves the hardness and the strength of the material, reduces the abrasion loss of the friction material during braking, and prolongs the service life of the powder metallurgy brake pad.)

1. A high melting point alloy reinforced copper-based powder metallurgy friction material is characterized in that: the material is prepared from the following raw materials in percentage by weight: 50-60% of copper powder, 10-20% of iron powder, 2-4% of zirconium, 2-4% of tungsten, 2-4% of chromium, 10-15% of graphite, 5-10% of ceramic particles, 1-2% of molybdenum disulfide and 2-4% of high-carbon ferrochrome.

2. A refractory alloy reinforced copper-based powder metallurgy friction material according to claim 1, wherein: the ceramic particles comprise aluminum oxide, silicon oxide or silicon carbide and are irregularly-shaped powder with the particle size of 75 um.

3. A refractory alloy reinforced copper-based powder metallurgy friction material according to claim 1, wherein: the copper powder is electrolytic copper powder with the particle size of 45 um; the iron powder is reduced iron powder with the particle size of 100 um.

4. A refractory alloy reinforced copper-based powder metallurgy friction material according to claim 1, wherein: the zirconium powder, the tungsten powder and the chromium powder are irregularly-shaped powder with the particle size of 45 um.

5. A refractory alloy reinforced copper-based powder metallurgy friction material according to claim 1, wherein: the graphite is artificial particle graphite with the particle size of 200-500 um.

6. A refractory alloy reinforced copper-based powder metallurgy friction material according to claim 1, wherein: the molybdenum disulfide is flaky powder with the particle size of 30 um; the high carbon ferrochrome is irregular powder with the grain size of 150 um.

7. A method for preparing a high melting point alloy reinforced copper-based powder metallurgy friction material according to claim 1, which is characterized in that: the method comprises the following steps:

step one, mixing materials:

weighing the raw materials according to the weight, and putting the raw materials into a V-shaped mixer for fully mixing;

step two, forming:

putting the powder mixed in the step one into a hydraulic press die, and performing cold pressing and forming;

step three, sintering:

and D, placing the pressed compact obtained in the step two into a bell-type pressure sintering furnace for pressure sintering, and introducing hydrogen and nitrogen as reducing and protective atmosphere in the sintering process.

8. The method for preparing a high melting point alloy reinforced copper-based powder metallurgy friction material according to claim 7, wherein the method comprises the following steps: the mixing time in the step one is 4-8 hours.

9. The method for preparing a high melting point alloy reinforced copper-based powder metallurgy friction material according to claim 7, wherein the method comprises the following steps: and step two, the pressing pressure is 600-800 MPa, and the pressure maintaining time is 20-30 s.

10. The method for preparing a high melting point alloy reinforced copper-based powder metallurgy friction material according to claim 7, wherein the method comprises the following steps: and step three, the sintering pressure is 4-5 MPa, the sintering temperature is 900-980 ℃, and the heat preservation time is 2-3 hours.

Technical Field

The invention relates to a high-melting-point alloy reinforced copper-based powder metallurgy friction material and a preparation method thereof.

Background

The copper-based powder metallurgy friction material is widely applied due to good thermal conductivity and mechanical property, and the high-speed motor train unit realizes speed reduction or parking by utilizing the friction force generated by the powder metallurgy brake pad and the brake disc, wherein the brake pad is a key part for ensuring the running safety of the high-speed motor train unit, and the used friction material is the copper-based powder metallurgy friction material; the brake pads of the motor train unit work under high temperature generated by high-speed friction, and when the high-speed motor train unit brakes, the temperature of the braking elements of the motor train unit can reach over 500 ℃, and the instantaneous temperature can even reach about 1000 ℃.

The copper-based powder metallurgy friction material is manufactured by taking copper or copper alloy as a base body, adding friction components, lubrication components and certain metal and nonmetal components which play special roles, and carrying out mixing, forming and sintering by a powder metallurgy method; the existing copper-based powder metallurgy friction material works at high temperature to soften a copper matrix and reduce the strength and hardness of the material, so that the clamping force of the matrix on lubricating components and friction components in the material is reduced, the friction coefficient of the material is attenuated, the abrasion of the material is increased, and the safe operation of a motor train unit train is threatened; in order to ensure the safe operation of the train of the motor train unit, the problem of the decline of the high-temperature performance of the copper-based powder metallurgy friction material is urgently needed to be solved.

Disclosure of Invention

In order to overcome the defects in the prior art, the invention provides a high-melting-point alloy reinforced copper-based powder metallurgy friction material and a preparation method thereof, and aims to solve the problems of high-temperature friction coefficient attenuation and large abrasion loss of the copper-based powder metallurgy friction material.

The technical scheme adopted by the invention for solving the technical problems is as follows: a high-melting-point alloy reinforced copper-based powder metallurgy friction material is prepared from the following raw materials in percentage by weight: 50-60% of copper powder, 10-20% of iron powder, 2-4% of zirconium, 2-4% of tungsten, 2-4% of chromium, 10-15% of graphite, 5-10% of ceramic particles, 1-2% of molybdenum disulfide and 2-4% of high-carbon ferrochrome.

The invention also provides a preparation method of the high-melting-point alloy reinforced copper-based powder metallurgy friction material, which comprises the following steps:

step one, mixing materials:

weighing the raw materials according to the weight, and putting the raw materials into a V-shaped mixer for fully mixing;

step two, forming:

putting the powder mixed in the step one into a hydraulic press die, and performing cold pressing and forming;

step three, sintering:

and D, placing the pressed compact obtained in the step two into a bell-type pressure sintering furnace for pressure sintering, and introducing hydrogen and nitrogen as reducing and protective atmosphere in the sintering process.

Compared with the prior art, the invention has the following positive effects:

the invention provides a copper-based powder metallurgy friction material and a preparation method thereof, which solve the problems of serious decline of friction coefficient and large abrasion loss when a powder metallurgy brake pad brakes at a high speed. The invention has the following specific advantages:

1) the invention uses three high-melting point alloys of zirconium, chromium and tungsten to strengthen the copper-based powder metallurgy friction material, improves the softening failure temperature of the copper matrix, and reduces the decline of the friction coefficient when the material is braked at high speed.

2) The copper-based powder metallurgy friction material improves the hardness and the strength of the material, reduces the abrasion loss of the friction material during braking, and prolongs the service life of the powder metallurgy brake pad.

Detailed Description

The high melting point alloy reinforced copper-based powder metallurgy friction material comprises the following powder materials in percentage by weight: 50-60% of copper, 10-20% of iron, 2-4% of a reinforcing phase (zirconium, 2-4% of tungsten and 2-4% of chromium), 10-15% of graphite, 1-2% of molybdenum disulfide, 2-4% of high-carbon ferrochromium, and 5-10% of alumina, silicon oxide and silicon carbide ceramic. The copper powder is electrolytic copper powder with the particle size of 45 um; the iron powder is reduced iron powder with the particle size of 100 um; the zirconium powder, the tungsten powder and the chromium powder are irregular powder with the grain diameter of 45 um; the graphite is artificial granular graphite with the particle size of 200-500 um; the molybdenum disulfide is flaky powder with the particle size of 30 um; the high carbon ferrochrome is irregularly shaped powder with the grain size of 150um, and the aluminum oxide, silicon oxide and silicon carbide ceramics are irregularly shaped powder with the grain size of 75 um.

The preparation method of the high-melting-point alloy reinforced copper-based powder metallurgy friction material comprises the following steps: weighing the weight of powder according to the proportion of various powder materials in the formula, putting the weighed powder into a V-shaped mixer for uniform mixing, pressing and forming the mixed powder by using a hydraulic press, and sintering a formed blank under high temperature and pressure to obtain the required copper-based powder metallurgy friction material, wherein the specific steps are as follows:

the method comprises the following steps: and (3) mixing materials, namely weighing various powder materials according to the required weight, and putting the powder materials into a V-shaped mixer to mix for 4-8 hours.

Step two: and (3) forming, namely putting the mixed powder into a hydraulic press die, and carrying out cold pressing and forming, wherein the pressing pressure is 600-800 MPa, and the pressure maintaining time is 20-30 s.

Step three: and sintering, namely putting the pressed compact into a bell-type pressure sintering furnace for pressure sintering, introducing hydrogen and nitrogen as reducing and protective atmosphere in the sintering process, wherein the sintering pressure is 4-5 MPa, the sintering temperature is 900-980 ℃, and the heat preservation time is 2-3 hours.

The present invention will be described in further detail with reference to specific examples below:

example 1

The embodiment provides a copper-based powder metallurgy friction material and a preparation method thereof, wherein the friction material comprises the following powder materials in parts by weight: 60% of copper, 11% of iron, reinforcing phases (2% of zirconium, 2% of tungsten and 2% of chromium), 13% of graphite, 6% of ceramic particles such as aluminum oxide and the like and 4% of the rest.

The preparation process of the friction material mainly comprises the following steps:

the method comprises the following steps: and (3) mixing materials, namely weighing the required powder materials according to the types and the weight proportion of the powder film materials, and putting the powder materials into a V-shaped mixer for mixing for 5 hours.

Step two: and (3) forming, namely putting the mixed powder into a hydraulic press die, and carrying out cold pressing forming, wherein the pressing pressure is 650MPa, and the pressure maintaining time is 20 s.

Step three: and sintering, namely putting the pressed compact into a bell-type pressure sintering furnace for pressure sintering, introducing hydrogen and nitrogen as reducing and protective atmosphere in the sintering process, wherein the sintering pressure is 4.4MPa, the sintering temperature is 930 ℃, and the heat preservation time is 2 hours.

Example 2

The embodiment provides a copper-based powder metallurgy friction material and a preparation method thereof, wherein the friction material comprises the following powder materials in parts by weight: 57% of copper, 11% of iron, a reinforcing phase (3% of zirconium, 3% of tungsten and 3% of chromium), 13% of graphite, 6% of ceramic particles such as aluminum oxide and the like, and the balance 4%.

The preparation process of the friction material mainly comprises the following steps:

the method comprises the following steps: and (3) mixing materials, namely weighing the required powder materials according to the type and weight ratio of the powder film materials, and putting the powder materials into a V-shaped mixer for mixing for 5 hours.

Step two: and (3) forming, namely putting the mixed powder into a hydraulic press die, and carrying out cold pressing forming, wherein the pressing pressure is 720MPa, and the pressure maintaining time is 25 s.

Step three: and sintering, namely putting the pressed compact into a bell-type pressure sintering furnace for pressure sintering, introducing hydrogen and nitrogen as reducing and protective atmosphere in the sintering process, wherein the sintering pressure is 4.8MPa, the sintering temperature is 960 ℃, and the heat preservation time is 2.5 hours.

Example 3

The embodiment provides a copper-based powder metallurgy friction material and a preparation method thereof, wherein the friction material comprises the following powder materials in parts by weight: 54% of copper, 15% of iron, a reinforcing phase (2% of zirconium, 2% of tungsten and 4% of chromium), 13% of graphite, 6% of ceramic particles such as aluminum oxide and the like and the balance 4%.

The preparation process of the friction material mainly comprises the following steps:

the method comprises the following steps: and (3) mixing materials, namely weighing the required powder materials according to the types and weight proportion requirements of the powder materials, and putting the powder materials into a V-shaped mixer for mixing for 5 hours.

Step two: and (3) forming, namely putting the mixed powder into a hydraulic press die, and carrying out cold pressing forming, wherein the pressing pressure is 680MPa, and the pressure maintaining time is 30 s.

Step three: and sintering, namely putting the pressed compact into a bell-type pressure sintering furnace for pressure sintering, introducing hydrogen and nitrogen as reducing and protective atmosphere in the sintering process, wherein the sintering pressure is 4.6MPa, the sintering temperature is 950 ℃, and the heat preservation time is 2.5 hours.

Comparative example

The embodiment provides a copper-based powder metallurgy friction material and a preparation method thereof, wherein the friction material comprises the following powder materials in parts by weight: 62% of copper, 15% of iron, 13% of graphite, 6% of ceramic particles such as aluminum oxide and the like and 4% of the rest.

The preparation process of the friction material mainly comprises the following steps:

the method comprises the following steps: and (3) mixing materials, namely weighing the required powder materials according to the types and weight proportion requirements of the powder materials, and putting the powder materials into a V-shaped mixer for mixing for 5 hours.

Step two: and (3) forming, namely putting the mixed powder into a hydraulic press die, and carrying out cold pressing forming under the pressing pressure of 600MPa for 20 s.

Step three: and sintering, namely putting the pressed compact into a bell-type pressure sintering furnace for pressure sintering, introducing hydrogen and nitrogen as reducing and protective atmosphere in the sintering process, wherein the sintering pressure is 4.0MPa, the sintering temperature is 900 ℃, and the heat preservation time is 2 hours.

Performing performance tests on the above examples 1 to 3 and comparative examples, wherein the performance tests comprise Brinell hardness, shear strength, compressive strength, friction coefficient and abrasion loss; the friction coefficient and wear loss test method is defined as follows by referring to TJ/CL307-2019 motor train unit brake pad temporary technical conditions:

average coefficient of friction: instantaneous coefficient of friction at braking distance S₂The integral of the above is represented by μ, and the calculation formula is shown in formula 1.

In formula 1:

S₂-the distance of the pneumatic clamp from 95% of the total braking force to the stop at parking;

μ_a-instantaneous coefficient of friction, the ratio of tangential force to total brake pad pressure at any given braking instant.

The abrasion loss is calculated as shown in formula 2;

in formula 2:

l-abrasion loss per unit braking energy, unit is cubic centimeter per megajoule (cm)³/MJ)；

W₁-weight of material before test in grams (g);

W₂-weight of material after test in grams (g);

e, braking energy generated by all braking tests in the test process is Megajoule (MJ);

rho-density of friction material in grams per cubic centimeter (g/cm)³)。

The method for calculating the decline rate comprises the following steps: according to the detection method of the average friction coefficient, under the conditions that the initial speed is 200km/h and 350km/h, 20 times of braking tests are respectively carried out to obtain the average friction coefficient obtained by 20 times of braking, the arithmetic mean value of the average friction coefficient is obtained, the decline rate of the friction coefficient is calculated, and the calculation formula is shown in formula 3.

In formula 3:

μ_350km/h-the arithmetic mean of the average friction coefficients of 20 initial speed brakes at 350 km/h;

μ_200km/h-arithmetic mean of the mean friction coefficient of the initial speed brakes at 200km/h 20 times.

The results are shown in Table 1.

TABLE 1 test results

According to the detection results, the copper-based powder metallurgy friction material prepared by the method has the advantages that the decline of the friction coefficient is small and the abrasion loss is small along with the increase of the braking speed; compared with the comparative example, the braking speed is increased from 200km/h to 350km/h, the decline rate of the friction coefficient is reduced by about 10 percent, and the abrasion loss is reduced from 0.28cm³The MJ is reduced to 0.20-0.23 cm³The service life of the/MJ can be prolonged by 18-25%, and the Brinell hardness, the shear strength and the compressive strength of the friction material are all obviously improved.