High-temperature-resistant powder metallurgy friction material and preparation method thereof

Abstract

The invention relates to the technical field of copper-based powder metallurgy friction materials, in particular to a high-temperature-resistant powder metallurgy friction material and a preparation method thereof. The preparation method comprises the following steps: a material mixing process, a forming process and a sintering process in sequence; in the material mixing process, firstly, graphite particles and iron oxide powder are wrapped together by a coating machine under the action of liquid paraffin to form particles I with the graphite particles as cores and the iron oxide powder as coats; the first particles and the iron-copper alloy powder are wrapped together through a coating machine under the action of liquid paraffin, and second particles with the first particles as cores and the iron-copper alloy powder as coats are formed; finally, mixing the particles II with other residual powder; the graphite, the iron oxide powder and the iron-copper alloy powder are mixed in advance, and then in the sintering process, specific pores are formed through chemical reaction of the graphite, the iron oxide powder and the iron-copper alloy powder, so that the noise absorption performance of the material is not affected, and the high-temperature shearing resistance of the material is remarkably improved.

Description

Technical Field

[0001] The invention relates to the technical field of copper-based powder metallurgy friction materials, in particular to a high-temperature resistant powder metallurgy friction material and a preparation method thereof. Background Art

[0002] Copper-based powder metallurgy friction material has the advantages of stable friction coefficient, good thermal stability, and good compatibility with steel friction pairs. It is a high-performance friction material. It has important applications in many demanding working conditions, such as large braking inertia and the need for continuous braking. The main components of copper-based powder metallurgy friction materials are composed of three parts: 1. Basic components composed of copper, iron and their alloy components; 2. Lubricating components composed of graphite, metal sulfides, low-melting-point metals, etc.; 3. Friction components composed of ceramic materials such as metal oxides and metal carbides.

[0003] In order to meet the requirements of friction materials being noise-free and not damaging the pair, the friction materials have very strict requirements on hardness and porosity. Due to the poor wettability of metals such as graphite and copper, the porosity of copper-based powder metallurgy friction materials is generally formed along the interface between copper and graphite. Although this meets the normal use requirements of friction materials, under some high-temperature conditions, due to the oxidation of copper itself and the thermal expansion effect of the material as a whole, the risk of separation of the copper and graphite interface increases, the overall shear strength of the material decreases, and the probability of falling off increases, increasing the risk of failure during material use. Summary of the invention

[0004] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a powder metallurgy friction material with high temperature resistance and a preparation method thereof. In the mixing process, graphite is pre-mixed with iron oxide powder and iron-copper alloy powder, and then in the sintering process, the graphite and the metal are firmly bonded together through the chemical reaction between the graphite, the iron oxide powder and the iron-copper alloy powder, and unique pores are formed, which does not affect the noise absorption performance of the material and significantly improves the material's resistance to high temperature shearing.

[0005] In order to achieve the above object, the present invention is implemented through the following technical solutions:

[0006] In a first aspect, the present invention provides a powder metallurgy friction material with high temperature resistance, the material ratio of the main components is:

[0007] 40-70% copper powder, 5-20% iron-copper alloy powder, 5% iron oxide powder, 10-20% graphite particles, 2-5% low melting point metal powder and 8-10% friction component particles.

[0008] As a further implementation, the low melting point metal powder is a powder with a melting point lower than 800°C.

[0009] As a further implementation, the low melting point metal powder is tin powder or zinc powder.

[0010] As a further implementation, the friction component particles are silicon carbide, aluminum oxide or tungsten carbide.

[0011] In a second aspect, the present invention provides a method for preparing the high temperature resistant powder metallurgy friction material according to the first aspect, comprising the following steps:

[0012] The preparation method comprises a mixing process, a molding process and a sintering process in sequence; in the mixing process, firstly, graphite particles and iron oxide powder are coated together by a coating machine under the action of liquid paraffin to form particle one with graphite particles as core and iron oxide powder as outer coating; then, particle one and iron-copper alloy powder are coated together by a coating machine under the action of liquid paraffin to form particle two with particle one as core and iron-copper alloy powder as outer coating; finally, particle two is mixed together with other remaining powders.

[0013] As a further implementation, the sintering process needs to be carried out in a hydrogen and nitrogen mixed atmosphere.

[0014] As a further implementation method, the upper and lower surfaces of the product are pressurized for protection during sintering.

[0015] As a further implementation, the sintering temperature is 800-1000°C.

[0016] As a further implementation method, the mixing time of the granule 2 and other remaining powders is 30 to 180 minutes.

[0017] As a further implementation, the forming process is performed according to a normal powder metallurgy forming process.

[0018] The beneficial effects of the present invention are as follows:

[0019] 1. In the mixing process, the present invention premixes graphite with iron oxide powder and iron-copper alloy powder, and then in the sintering process, the graphite and the metal are firmly combined together through the chemical reaction of graphite with iron oxide powder and iron-copper alloy powder, and a unique pore is formed, which does not affect the noise absorption performance of the material and significantly improves the high-temperature shear performance of the material. Under the condition of maintaining the friction performance of the material, the high-temperature shear performance of the material can be improved by 20% to 50%.

[0020] 2. In the sintering process of the present invention, the iron oxide is reduced to iron by hydrogen in the environment and the wrapped graphite during high-temperature sintering. At the same time, the graphite participates in the reduction and generates carbon dioxide, so the surface becomes rough and forms micropores. The iron powder is combined with the graphite inwardly and with the iron-copper alloy powder outward, forming a good holding force on the graphite particles. The iron-copper alloy powder and the copper powder are alloyed during the sintering process, so that the metal in the friction material forms a network of continuous alloys. During the friction process, since iron has strong high temperature resistance and good bonding with graphite, the larger graphite particles are less likely to fall out, and the material has better high temperature resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0022] Figure 1 It is a flow chart of the method for preparing a powder metallurgy friction material with high temperature resistance in an embodiment of the present invention. DETAILED DESCRIPTION

[0023] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0024] Embodiment 1

[0025] In a typical embodiment of the present invention, a high temperature resistant powder metallurgy friction material has a material ratio of the main components as follows:

[0026] 40% copper powder, 20% iron-copper alloy powder, 5% iron oxide powder, 20% graphite particles, 5% zinc powder and 10% silicon carbide particles.

[0027] In this embodiment, the low melting point metal powder is zinc powder. In some other embodiments, the low melting point metal powder includes but is not limited to tin powder, zinc powder and other powders with a melting point lower than 800°C.

[0028] In this embodiment, the friction component particles are silicon carbide particles. In other embodiments, they include but are not limited to metal oxides such as silicon carbide and aluminum oxide or tungsten carbide particles.

[0029] like Figure 1 As shown, the preparation method of the high temperature resistant powder metallurgy friction material of this embodiment includes the following steps:

[0030] In the mixing process of this embodiment, the graphite particles and the iron oxide powder are firstly coated together with liquid paraffin by a coating machine to form particle 1; then the particle 1 is coated with the iron-copper alloy powder to form particle 2; finally, the particle 2 is mixed with other powders by a three-dimensional mixer for 60 minutes. The mixing time ranges from 30 to 180 minutes, which can be selected according to the actual situation.

[0031] The molding process of this embodiment can be carried out according to the normal powder metallurgy molding process.

[0032] In this embodiment, the sintering process is carried out in a hydrogen and nitrogen mixed atmosphere, the sintering temperature is 920°C, the upper and lower surfaces of the product are pressurized for protection during sintering, and the sintering pressure is 5MPa. The sintering temperature range is 800-1000°C, which can be selected according to actual conditions.

[0033] In the mixing process, graphite is pre-mixed with iron oxide powder and iron-copper alloy powder, and then in the sintering process, through the chemical reaction of graphite, iron oxide powder and iron-copper alloy powder, graphite and metal are firmly combined together and form unique pores, which does not affect the noise absorption performance of the material and significantly improves the material's high-temperature shear performance. Under the condition of maintaining the material's friction performance, the material's high-temperature shear performance can be improved by 20% to 50%.

[0034] During the sintering process, iron oxide is reduced to iron by hydrogen in the environment and the graphite it contains during high-temperature sintering. At the same time, the graphite participates in the reduction and generates carbon dioxide, so its surface becomes rough and forms micropores. The iron powder combines with the graphite internally and with the iron-copper alloy powder externally, forming a good grip on the graphite particles. The iron-copper alloy powder and the copper powder are alloyed during the sintering process, so that the metal in the friction material forms a network of continuous alloys. During the friction process, since iron has strong high-temperature resistance and good bonding with graphite, larger graphite particles are less likely to fall out, and the material has better high-temperature resistance.

[0035] The friction material prepared by the above preparation method has the following product properties:

[0036] The material friction coefficient is 0.3-0.4, which is the same as the friction material produced by normal process;

[0037] Material hardness (HB) 20-30, the same as the friction material produced by normal process;

[0038] The shear strength of the material is 20-40MPa, which is higher than the friction material produced by the normal process (8-12MPa);

[0039] At 300℃, the shear strength of the material is 20-40MPa, which is higher than the friction material produced by the normal production process (7-10MPa);

[0040] At 600°C, the shear strength of the material is 15-30MPa, which is higher than the friction material produced by the normal production process (6-8MPa).

[0041] The high temperature resistant powder metallurgy friction material prepared in this embodiment is suitable for high-speed and light-load braking conditions.

[0042] Embodiment 2

[0043] In a typical embodiment of the present invention, a high temperature resistant powder metallurgy friction material has a material ratio of the main components as follows:

[0044] 55% copper powder, 15% iron-copper alloy powder, 5% iron oxide powder, 10% graphite particles, 5% zinc powder and 10% silicon carbide particles.

[0045] The method for preparing the high temperature resistant powder metallurgy friction material of this embodiment comprises the following steps:

[0046] In the mixing process of this embodiment, the graphite particles and the iron oxide powder are firstly wrapped together with liquid paraffin by a coating machine to form particle one; then the particle one is wrapped with the iron-copper alloy powder to form particle two; finally, the particle two is mixed with other powders by a three-dimensional mixer for 60 minutes.

[0047] The molding process of this embodiment can be carried out according to the normal powder metallurgy molding process.

[0048] During the sintering process of this embodiment, the sintering is carried out in a hydrogen and nitrogen mixed atmosphere at a sintering temperature of 900° C. During sintering, the upper and lower surfaces of the product are pressurized for protection at a sintering pressure of 3 MPa.

[0049] The friction material prepared by the above preparation method has the following product properties:

[0050] The material friction coefficient is 0.3-0.4, which is the same as the friction material produced by normal process;

[0051] Material hardness (HB) 15-25, the same as the friction material produced by normal process;

[0052] The shear strength of the material is 15-20MPa, which is higher than the friction material produced by the normal process (8-12MPa);

[0053] At 300℃, the shear strength of the material is 15-20MPa, which is higher than the friction material produced by the normal process (7-10MPa);

[0054] At 600°C, the shear strength of the material is 12-18MPa, which is higher than the friction material produced by the normal production process (6-8MPa).

[0055] The high temperature resistant powder metallurgy friction material prepared in this embodiment is suitable for high-speed braking conditions under normal braking force.

[0056] Embodiment 3

[0057] In a typical embodiment of the present invention, a high temperature resistant powder metallurgy friction material has a material ratio of the main components as follows:

[0058] 70% copper powder, 5% iron-copper alloy powder, 5% iron oxide powder, 10% graphite particles, 2% zinc powder and 8% silicon carbide particles.

[0059] The method for preparing the high temperature resistant powder metallurgy friction material of this embodiment comprises the following steps:

[0060] In the mixing process of this embodiment, the graphite particles and the iron oxide powder are firstly wrapped together with liquid paraffin by a coating machine to form particle one; then the particle one is wrapped with the iron-copper alloy powder to form particle two; finally, the particle two is mixed with other powders by a three-dimensional mixer for 60 minutes.

[0061] The molding process of this embodiment can be carried out according to the normal powder metallurgy molding process.

[0062] In the present embodiment, the sintering process is carried out in a hydrogen and nitrogen mixed atmosphere at a sintering temperature of 950° C. During sintering, the upper and lower surfaces of the product are pressurized for protection at a sintering pressure of 2 MPa.

[0063] The friction material prepared by the above preparation method has the following product properties:

[0064] The material friction coefficient is 0.4 to 0.6, which is the same as the friction material produced by normal process;

[0065] Material hardness (HB) 15-25, the same as the friction material produced by normal process;

[0066] The shear strength of the material is 30-50MPa, which is higher than the friction material produced by the normal process (20-40MPa);

[0067] At 300℃, the shear strength of the material is 25-40MPa, which is higher than the friction material produced by the normal process (15-30MPa);

[0068] At 600℃, the shear strength of the material is 20-35MPa, which is higher than the friction material produced by the normal production process (10-20MPa).

[0069] The high temperature resistant powder metallurgy friction material prepared in this embodiment is particularly suitable for heavy load and low speed working conditions.

[0070] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A high temperature resistant powder metallurgy friction material, characterized in that: The material ratio of the main components is: 40-70% copper powder, 5-20% iron-copper alloy powder, 5% iron oxide powder, 10-20% graphite particles, 2-5% low melting point metal powder and 8-10% friction component particles.

2. The high temperature resistant powder metallurgy friction material according to claim 1, characterized in that: The low melting point metal powder is a powder with a melting point lower than 800°C.

3. The high temperature resistant powder metallurgy friction material according to claim 2, characterized in that: The low melting point metal powder is tin powder or zinc powder.

4. The high temperature resistant powder metallurgy friction material according to claim 1, characterized in that: The friction component particles are silicon carbide, aluminum oxide or tungsten carbide.

5. A method for preparing a high temperature resistant powder metallurgy friction material according to any one of claims 1 to 4, characterized in that: The following steps are involved: The preparation method comprises a mixing process, a molding process and a sintering process in sequence; in the mixing process, firstly, graphite particles and iron oxide powder are coated together by a coating machine under the action of liquid paraffin to form particle one with graphite particles as core and iron oxide powder as outer coating; then, particle one and iron-copper alloy powder are coated together by a coating machine under the action of liquid paraffin to form particle two with particle one as core and iron-copper alloy powder as outer coating; finally, particle two is mixed together with other remaining powders.

6. The method for preparing the high temperature resistant powder metallurgy friction material according to any one of claims 1 to 4 according to claim 5, characterized in that: The sintering process needs to be carried out in a hydrogen and nitrogen mixed atmosphere.

7. The method for preparing the high temperature resistant powder metallurgy friction material according to any one of claims 1 to 4 according to claim 6, characterized in that: During sintering, the upper and lower surfaces of the product are pressurized for protection.

8. The method for preparing the high temperature resistant powder metallurgy friction material according to any one of claims 1 to 4 according to claim 7, characterized in that: The sintering temperature is 800-1000°C.

9. The method for preparing the high temperature resistant powder metallurgy friction material according to any one of claims 1 to 4 according to claim 5, characterized in that: The mixing time of the granule 2 and other remaining powders is 30 to 180 minutes.

10. The method for preparing the high temperature resistant powder metallurgy friction material according to any one of claims 1 to 4 according to claim 5, characterized in that: The molding process is carried out according to a normal powder metallurgy molding process.

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