阅读说明：本技术 一种低磨耗粉末冶金闸片及其制备工艺 (Low-abrasion powder metallurgy brake pad and preparation process thereof ) 是由 赵旭 魏东彬 曹静武 余程巍 丁向莹 孙志远 程景琳 张振威 于 2021-10-11 设计创作，主要内容包括：本发明公开了一种低磨耗粉末冶金闸片及其制备工艺,其中,一种低磨耗粉末冶金闸片的制备工艺包括:混配料：获取原料,将各原料混合均匀获得混合料；压制：将混合料在500-600MPa的压力条件下保压2-20s；烧结：在烧结气氛下进行烧结,烧结温度为750-1050℃、烧结压力≤10MPa,烧结时间为2-8h。本发明可以使烧结过程中的各组分能够充分的扩散结合,加强了闸片内部石墨与金属基体的结合强度,缓解了在制动过程中石墨剥离的现象,从而降低磨耗,延长寿命。(The invention discloses a low-abrasion powder metallurgy brake pad and a preparation process thereof, wherein the preparation process of the low-abrasion powder metallurgy brake pad comprises the following steps: obtaining raw materials, and uniformly mixing the raw materials to obtain a mixture; pressing: maintaining the pressure of the mixture for 2-20s under the pressure condition of 500-600 MPa; and (3) sintering: sintering in sintering atmosphere at 750-1050 deg.c under 10MPa for 2-8 hr. The invention can ensure that all components in the sintering process can be fully diffused and combined, enhances the bonding strength of the graphite in the brake pad and the metal matrix, and relieves the graphite stripping phenomenon in the braking process, thereby reducing the abrasion and prolonging the service life.)

1. A preparation process of a low-abrasion powder metallurgy brake pad is characterized by comprising the following steps:

mixing materials: obtaining raw materials, and uniformly mixing the raw materials to obtain a mixture;

pressing: maintaining the pressure of the mixture for 2-20s under the pressure condition of 500-600 MPa;

and (3) sintering: sintering in sintering atmosphere at 750-1050 deg.c under 10MPa for 2-8 hr.

2. The preparation process of the low-abrasion powder metallurgy brake pad according to claim 1, wherein the rotation speed of the raw materials during mixing is 10-50r/min, and the mixing time is 10-200 min.

3. The process for preparing the low-abrasion powder metallurgy brake pad according to claim 2, wherein the mixing time is 80-200 min.

4. The process for preparing a low-abrasion powder metallurgy brake pad according to claims 1 to 3, wherein the particle size of the graphite in the raw material is 20 to 140 meshes.

5. The process for preparing a low-wear powder metallurgy brake pad according to any one of claims 1 to 4, wherein the sintering temperature is 800-1050 ℃, and the sintering time is 4-8 h.

6. The process for preparing a low-abrasion powder metallurgy brake pad according to any one of claims 1 to 5, wherein the sintering atmosphere is a vacuum atmosphere, an inert atmosphere or a reducing atmosphere.

7. The process for preparing a low-abrasion powder metallurgy brake pad according to any one of claims 1 to 6, wherein the low-abrasion powder metallurgy brake pad is a copper-based powder metallurgy brake pad.

8. The process for preparing a low-abrasion powder metallurgy brake pad according to claim 7, wherein the copper content of the copper-based powder metallurgy brake pad is 40-70%.

9. A low-wear powder metallurgy brake pad, which is prepared by the preparation process of the low-wear powder metallurgy brake pad according to any one of claims 1 to 8.

Technical Field

The invention relates to the technical field of powder metallurgy brake pads, in particular to a low-abrasion powder metallurgy brake pad and a preparation process thereof.

Background

In order to meet the development requirements of a high-speed train for rapidness, safety, comfort and environmental protection, the high-speed train brake material has the characteristics of proper and stable friction factor, excellent wear resistance, high heat resistance and thermal fatigue resistance, sufficient mechanical strength, good matching with a brake disc, good environmental adaptability, environmental friendliness and the like. The powder metallurgy brake pad has irreplaceable superiority in braking, so that the brake pad is adopted by high-speed trains of 300km/h and above at present.

The brake pad of the motor train unit belongs to a vulnerable and consumable part, and directly influences the operation cost of the motor train unit. Meanwhile, the brake pad and the brake disc are a pair of friction pairs, and the material formula and the structure of the brake pad are directly related to the comprehensive performance of the friction pairs and the service life of the brake disc. Therefore, it is necessary to develop a powder metallurgy brake pad with lower abrasion for prolonging the service life of the brake pad and reducing the operation cost of the motor train unit.

In order to prolong the service life of the powder metallurgy high-speed rail brake pad and reduce the abrasion, the factors influencing the service life of the powder metallurgy brake pad need to be understood firstly, and then the brake pad is optimized according to the symptoms. Scanning electron microscope analysis of the brake pad by the inventor shows that the combination of the graphite inside the brake pad and the metal matrix is poor. The stripping phenomenon is easy to occur in the braking process, and the non-metallic stripping phenomenon is the main factor influencing the service life of the brake pad.

The existing method for solving the problem of poor combination of graphite and a metal matrix is just like the powder metallurgy preparation method for improving the performance of a copper alloy graphite composite material, which is disclosed in Chinese patent CN102925731A, and after the surface of graphite is modified by a chemical plating method, the modified graphite and the copper alloy are compounded to prepare the composite material with lower friction coefficient and higher wear resistance. However, the above modification method has problems of complicated operation steps and higher cost.

Disclosure of Invention

Therefore, the invention aims to solve the technical problems that the existing preparation of the powder metallurgy brake pad by using graphite modified by an electroless plating method causes the defects of complex operation and higher cost, thereby providing a preparation process of the low-abrasion powder metallurgy brake pad with simpler operation steps and lower preparation cost.

A preparation process of a low-abrasion powder metallurgy brake pad comprises the following steps:

mixing materials: obtaining raw materials, and uniformly mixing the raw materials to obtain a mixture;

pressing: maintaining the pressure of the mixture for 2-20s under the pressure condition of 500-600 MPa;

and (3) sintering: sintering in sintering atmosphere at 750-1050 deg.c under 10MPa for 2-8 hr.

The rotating speed of the raw materials is 10-50r/min when the raw materials are mixed, and the mixing time is 10-200 min. In the material mixing process, the material mixing time is properly prolonged, so that raw materials of all components can be mixed more uniformly, and the phenomenon of aggregation of non-metal raw materials is avoided; however, the mixing time is too long, which reduces the production efficiency, and in the present invention, the mixing time is preferably 80 to 200min, more preferably 80 to 140 min.

The particle size of the graphite in the raw material is 20-140 meshes.

The pressure in the pressing step is preferably 550-600MPa, and the dwell time is preferably 8-20 s.

The sintering temperature is preferably 800-1050 ℃, and more preferably 950-1050 ℃; the sintering time is preferably 4-8 h. According to the invention, by increasing the sintering temperature and the sintering duration, and combining the pressing process and the graphite particle size, the bonding strength between the graphite and the metal matrix can be remarkably increased, and more excellent performance can be effectively achieved. The sintering temperature is increased by at least 50 ℃ in the invention, and the time duration is increased by at least 1 h.

The sintering atmosphere is a vacuum atmosphere, an inert atmosphere or a reducing atmosphere.

The low-abrasion powder metallurgy brake pad is a copper-based powder metallurgy brake pad.

The copper content of the copper-based powder metallurgy brake pad is 40% -70%.

The low-abrasion powder metallurgy brake pad is prepared by the preparation process of the low-abrasion powder metallurgy brake pad.

The technical scheme of the invention has the following advantages:

according to the preparation process of the low-abrasion powder metallurgy brake pad, the pressing pressure is obviously improved and the pressing time is reduced in the pressing process, meanwhile, the sintering time is properly prolonged in the sintering process, and the sintering pressure and the sintering temperature within a specific range are combined, so that all components can be fully diffused and combined in the sintering process, the bonding strength of graphite inside the brake pad and a metal matrix is enhanced, the graphite stripping phenomenon in the braking process is relieved, the abrasion is reduced, and the service life is prolonged. The effect of reducing abrasion is basically equivalent to or even more excellent than that of a powder metallurgy brake pad prepared by graphite modified by an electroless plating method in the prior art, and compared with the graphite modified by the electroless plating method, the operation process is simpler and the cost is lower.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.

FIG. 1 is an SEM electron micrograph of a brake pad prepared in example 1 of the present invention;

FIG. 2 is an SEM electron micrograph of a brake pad prepared in example 2 of the present invention;

FIG. 3 is an SEM electron micrograph of a brake pad prepared in example 3 of the present invention;

FIG. 4 is an SEM electron micrograph of the brake pad prepared in example 4 of the present invention;

FIG. 5 is an SEM electron micrograph of a brake pad prepared in example 5 of the present invention;

FIG. 6 is an SEM electron micrograph of a shutter prepared according to comparative example 1 of the present invention.

Detailed Description

The following examples are provided to further understand the present invention, not to limit the scope of the present invention, but to provide the best mode, not to limit the content and the protection scope of the present invention, and any product similar or similar to the present invention, which is obtained by combining the present invention with other prior art features, falls within the protection scope of the present invention.

The examples do not show the specific experimental steps or conditions, and can be performed according to the conventional experimental steps described in the literature in the field. The reagents or instruments used are not indicated by manufacturers, and are all conventional reagent products which can be obtained commercially.

Example 1

A preparation process of a low-abrasion powder metallurgy brake pad comprises the following steps:

mixing materials: the weighed raw materials of the components are put into a mixer, and the mixer mixes the materials according to the speed of 10-50 rpm for 10-200 minutes. In this example, the raw material consisted of a copper source, an iron source, a molybdenum source, a chromium source, graphite, and alumina. Wherein, the weight ratio of copper powder: 45-65%, iron powder: 15-30%, anatase type titanium dioxide powder: 1-10% and molybdenum disulfide powder: 1-5% and chromium powder: 1-10%, high-carbon ferrochrome powder: 1-10%, alumina: 1-5%, graphite: 1 to 5 percent. Specifically, in this example, 57% of the copper powder (45 μm), 18% of iron powder (48 μm), 3% of anatase titanium dioxide powder (6.5 μm), 2% of molybdenum disulfide powder (48 μm), 3% of chromium powder (45 μm), 4% of high-carbon ferrochromium powder (45 μm), 1% of alumina fiber (8 μm in diameter and 75 μm in length), 5% of particulate graphite (160 μm), and 7% of flake graphite (250 μm); the concrete mixing process comprises the following steps: pouring the raw material powder into a double-cone spraying mixer, continuously rotating a mixing cylinder to turn over the material at the rotation speed of 30 revolutions per minute, enabling the sprayed bonding lubricant solution to form a fog shape under the high-pressure gas pressure of about 0.1MPa, fully contacting the fog-shaped solution with the material turned over in the mixing cylinder, and mixing for 80 minutes to form a mixture.

Pressing: and (3) putting the mixture into a press for cold pressing, wherein the pressure is set to be 500MPa, and the pressure maintaining time is 10 s.

And (3) sintering: the sintering atmosphere is mixed gas of hydrogen and nitrogen, the cold pressed compact is sintered under 2.5MPa, the sintering temperature is 960 ℃, and the sintering time is 6 hours.

Preparing a brake pad: and assembling the sintered friction material into a finished brake pad, wherein an SEM (scanning electron microscope) image of the finished brake pad is shown in FIG. 1.

Example 2

The preparation process of the low-abrasion powder metallurgy brake pad is different from that of the embodiment 1 in the process parameter conditions in the pressing and sintering processes in the embodiment, and the specific settings are as follows:

pressing: maintaining the pressure of the mixture for 20s under the pressure condition of 550 MPa;

and (3) sintering: the sintering atmosphere is hydrogen-nitrogen mixed gas, the sintering temperature is 1010 ℃, the sintering pressure is 10MPa, and the sintering time is 3 h.

An SEM electron micrograph of the finished brake pad obtained in this example is shown in fig. 2.

Example 3

The preparation process of the low-abrasion powder metallurgy brake pad is different from that of the embodiment 1 in the process parameter conditions in the pressing and sintering processes in the embodiment, and the specific settings are as follows:

pressing: maintaining the pressure of the mixture for 8s under the pressure condition of 600 MPa;

and (3) sintering: the sintering atmosphere is hydrogen-nitrogen mixed gas, the sintering temperature is 1000 ℃, the sintering pressure is 5MPa, and the sintering time is 4 h.

An SEM micrograph of the finished brake pad obtained in this example is shown in fig. 3.

Example 4

The preparation process of the low-abrasion powder metallurgy brake pad is different from that of the embodiment 1 in the process parameter conditions in the pressing and sintering processes in the embodiment, and the specific settings are as follows:

pressing: maintaining the pressure of the mixture for 20s under the pressure condition of 530 MPa;

and (3) sintering: the sintering atmosphere is mixed gas of hydrogen and nitrogen, the sintering temperature is 990 ℃, the sintering pressure is 5MPa, and the sintering time is 8 h.

An SEM micrograph of the finished brake pad obtained in this example is shown in fig. 4.

Example 5

The preparation process of the low-abrasion powder metallurgy brake pad is different from that of the embodiment 1 in the process parameter conditions in the pressing and sintering processes in the embodiment, and the specific settings are as follows:

pressing: maintaining the pressure of the mixture for 2s under the pressure condition of 600 MPa;

and (3) sintering: the sintering atmosphere is hydrogen-nitrogen mixed gas, the sintering temperature is 1000 ℃, the sintering pressure is 7MPa, and the sintering time is 6 h.

An SEM micrograph of the finished brake pad obtained in this example is shown in fig. 5.

Comparative example 1

A preparation process of a low-abrasion powder metallurgy brake pad comprises the following steps:

mixing materials: the weighed raw materials of the components are put into a mixer, and the mixer mixes the materials according to the speed of 10-50 rpm for 10-200 minutes. In this example, the raw material consisted of a copper source, an iron source, a molybdenum source, a chromium source, graphite, and alumina. Wherein, the weight ratio of copper powder: 45-65%, iron powder: 15-30%, anatase type titanium dioxide powder: 1-10% and molybdenum disulfide powder: 1-5% and chromium powder: 1-10%, high-carbon ferrochrome powder: 1-10%, alumina: 1-5%, graphite: 1 to 5 percent. Specifically, in this example, 57% of the copper powder (45 μm), 18% of iron powder (48 μm), 3% of anatase titanium dioxide powder (6.5 μm), 2% of molybdenum disulfide powder (48 μm), 3% of chromium powder (45 μm), 4% of high-carbon ferrochromium powder (45 μm), 1% of alumina fiber (8 μm in diameter and 75 μm in length), 5% of particulate graphite (160 μm), and 7% of flake graphite (250 μm); the concrete mixing process comprises the following steps: pouring the raw material powder into a double-cone spraying mixer, continuously rotating a mixing cylinder to turn over the material at the rotation speed of 30 revolutions per minute, enabling the sprayed bonding lubricant solution to form a fog shape under the high-pressure gas pressure of about 0.1MPa, fully contacting the fog-shaped solution with the material turned over in the mixing cylinder, and mixing for 360 minutes to form a mixture.

Pressing: and putting the mixture into a press for cold pressing, wherein the pressure is set to be 460MPa, and the pressure maintaining time is 10 s.

And (3) sintering: the sintering atmosphere is hydrogen-nitrogen mixed gas, the cold pressed compact is sintered under the pressure of 1.5MPa, the sintering temperature is 880 ℃, and the sintering time is 2 hours.

Preparing a brake pad: and assembling the sintered friction material into a finished brake pad. An SEM micrograph of the finished brake pad obtained in this example is shown in fig. 6.

Comparative example 2

A preparation process of a low-abrasion powder metallurgy brake pad comprises the following steps:

mixing materials: the weighed raw materials of the components are put into a mixer, and the mixer mixes the materials according to the speed of 10-50 rpm for 10-200 minutes. In this example, the raw material consisted of a copper source, an iron source, a molybdenum source, a chromium source, graphite, and alumina. Wherein, the weight ratio of copper powder: 45-65%, iron powder: 15-30%, anatase type titanium dioxide powder: 1-10% and molybdenum disulfide powder: 1-5% and chromium powder: 1-10%, high-carbon ferrochrome powder: 1-10%, alumina: 1-5%, graphite: 1 to 5 percent. Specifically, in this example, 45% of the copper powder (45 μm), 18% of iron powder (48 μm), 3% of anatase titanium dioxide powder (6.5 μm), 2% of molybdenum disulfide powder (48 μm), 3% of chromium powder (45 μm), 4% of high-carbon ferrochrome powder (45 μm), 1% of alumina fiber (diameter 8 μm, length 75 μm), and 24% of copper-coated graphite powder; the graphite is copper-coated graphite powder with copper content of 50 wt% and 200 meshes. That is, in this comparative example, the copper-coated graphite powder 24% and the copper powder 45% were used in place of 57% of the copper powder (45 μm), 5% of the granular graphite (160 μm) and 7% of the flake graphite (250 μm) described in comparative example 1, and the other examples were the same as in comparative example 1. The concrete mixing process comprises the following steps: pouring the raw material powder into a double-cone spraying mixer, continuously rotating a mixing cylinder to turn over the material at the rotation speed of 30 revolutions per minute, enabling the sprayed bonding lubricant solution to form a fog shape under the high-pressure gas pressure of about 0.1MPa, fully contacting the fog-shaped solution with the material turned over in the mixing cylinder, and mixing for 360 minutes to form a mixture.

Pressing: and putting the mixture into a press for cold pressing, wherein the pressure is set to be 460MPa, and the pressure maintaining time is 10 s.

And (3) sintering: the sintering atmosphere is hydrogen-nitrogen mixed gas, the cold pressed compact is sintered under the pressure of 1.5MPa, the sintering temperature is 880 ℃, and the sintering time is 2 hours.

Preparing a brake pad: and assembling the sintered friction material into a finished brake pad.

Test examples

According to the detection requirements in the provisional technical conditions for brake pads of motor train units (Standard technical document number: TJ/CL 307-2019), the performances of the brake pads prepared in the above examples and comparative examples are detected, and the detection results are shown in the following table 1.

TABLE 1

As can be seen from the detection results in table 1, in examples 1 to 5 of the present invention, compared with comparative example 1, the pressing pressure is increased and the pressing time is reduced during the pressing process, and meanwhile, the sintering time is properly increased during the sintering process, and the sintering pressure and temperature within a specific range are combined, so that the components can be sufficiently diffusion-bonded during the sintering process, the bonding strength between the graphite inside the brake pad and the metal matrix is enhanced, the graphite peeling phenomenon during the braking process of the brake pad is alleviated, and the wear is reduced, and the service life is prolonged. Compared with the method adopting copper-clad graphite, the method can achieve basically equivalent or even better effect and save the preparation cost.

It should be understood that the above examples are only for clarity of illustration and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. And obvious variations or modifications therefrom are within the scope of the invention.