CN110081107B

CN110081107B - Friction material, brake pad prepared from friction material and preparation method

Info

Publication number: CN110081107B
Application number: CN201910239676.9A
Authority: CN
Inventors: 种详远; 甄明晖; 仇溢; 孙海燕
Original assignee: Shandong Gold Phoenix Co Ltd
Current assignee: Shandong Gold Phoenix Co Ltd
Priority date: 2019-03-27
Filing date: 2019-03-27
Publication date: 2021-02-02
Anticipated expiration: 2039-03-27
Also published as: CN110081107A

Abstract

The invention discloses a friction material, a brake pad prepared by the friction material and a preparation method, wherein the preparation method comprises the following steps: (1) preparing a copper-free metal friction material; (2) hot-press molding: placing the copper-free metal friction material in the step (1) in a hot-pressing die cavity, flattening, placing a cushion material, flattening, placing a steel backing, and demolding after hot-press molding; (3) cooling the demolded sample to room temperature after heat treatment; (4) and (4) carrying out post-treatment on the sample treated in the step (3) to obtain the brake pad. The preparation method of the brake pad can obviously improve the storage and transportation period and the oxidation resistance of the friction material in the brake pad through the rust prevention treatment.

Description

Friction material, brake pad prepared from friction material and preparation method

Technical Field

The invention relates to the technical field of automobile parts, in particular to a friction material, a brake pad prepared from the friction material and a preparation method of the brake pad.

Background

The brake pad, i.e. the brake pad or the brake shoe, is installed on the disc brake of the automobile wheel, and is one of the most critical safety parts in the vehicle braking system, and the performance of the brake pad plays an important role in the performance of braking safety, braking comfort, environmental friendliness and the like.

Common automobile brake disc friction materials are divided into two main types, namely metal type friction materials and NAO (non-asbestos organic) type friction materials, wherein the metal type friction materials comprise semi-metal type friction materials and few metal type friction materials, and are one of the most main friction materials in the world at present. The semi-metallic friction material is widely accepted mainly by the north american market, and the less-metallic friction material is widely accepted mainly by the european market. Compared with the NAO type friction material, the metal type friction material has higher heat conductivity and good friction and wear characteristics.

However, in the case of a metallic type friction material, the iron component is rusted by long-term exposure to a corrosive environment. The rust is mainly generated by the chemical and electrochemical reaction of iron components. With the continuous development of automobile globalization, vehicles in different areas or countries have more and more extensive import and export, and vehicles in different areas are easy to rust in different corrosive environments in the marine transportation process or parking braking process. Therefore, rust inhibition is very important for the brake pad market, especially for the OE (host-complete) market.

Patent CN 202520837U utilizes a mixture of resin and antirust material to form an antirust coating on the surface of the friction material, which can prevent rust during transportation, but the antirust coating has no braking effect and has a high braking risk, and this method of shielding the friction material can make the customer not see the internal material, increasing the uncertainty of application for the user. In patent CN 202158125U, a rust preventive oxide layer is coated on the central part of the friction material at a position slightly shorter than the material, and this rust prevention method is to increase the hydrophobicity of the surface and reduce the rust of the friction material at the coated position, but the uncoated area and the side position of the surface of the friction material are not completely sealed, and oxygen and water molecules can permeate through the surface air holes to generate rust. Patent CN 107489716 a uses sulfuric acid and phosphate solution to treat steel fiber to improve the corrosion resistance of friction material, but this increases the manufacturing process and is not matched with the existing production equipment.

At present, the commercial brake pad rust prevention mode mainly adopts two modes of plastic sucking and desiccant adding, and sometimes the two modes are combined simultaneously. Although the degree of rust can be reduced to some extent by the blister and the addition of a drying agent in a short time, both of these methods gradually lose the rust-proofing ability with the lapse of time.

Disclosure of Invention

In view of the above disadvantages of the prior art, the present invention provides a friction material, a brake pad made of the friction material, and a method for making the same, which overcome the disadvantages of the prior art, such as rusting tendency, oxidation tendency, short storage period, and environmental pollution.

In order to achieve the above object or other objects, the present invention is achieved by the following aspects.

A method of making a brake pad comprising the steps of:

(1) preparing a copper-free metal friction material;

(2) hot-press molding: placing the copper-free metal friction material in the step (1) in a hot-pressing die cavity, flattening, placing a cushion material, flattening, placing a steel backing, and demolding after hot-press molding;

(3) cooling the demolded sample to room temperature after heat treatment;

(4) and (4) carrying out post-treatment on the sample treated in the step (3) to obtain the brake pad.

Further, the copper-free metal friction material comprises the following raw material components in parts by weight: 7-15 parts of a binder, 5-20 parts of inorganic fibers, 2-7 parts of an organic regulator, 5.5-15 parts of a friction enhancer, 7-20 parts of a friction reducer, 6-20 parts of a filler, 5-40 parts of steel fibers subjected to rust prevention treatment and 5-15 parts of iron powder subjected to rust prevention treatment.

Further, the rust-preventive treatment of the steel fibers or the iron powder respectively includes: and respectively spraying a silane coupling agent on the surfaces of the steel fibers or the iron powder, respectively adding a binder, zinc phosphate and cerium trifluoride, uniformly stirring and drying to obtain the steel fibers or the iron powder subjected to the rust prevention treatment.

Preferably, the length of the steel fiber is 0.15-1 mm. The purity of the iron powder is more than 95%, and the diameter of the iron powder is 45-150 microns.

Preferably, the amount of the silane coupling agent accounts for 0.1-0.5% of the mass of the steel fiber or the iron powder. More preferably, the silane coupling agent is KH-550 silane coupling agent with purity of more than 97%.

Preferably, the amount of the binder used in the rust prevention treatment accounts for 1-2% of the mass of the steel fiber or the iron powder. More preferably, the binder is selected from unmodified phenolic resins. Preferably, the flow distance of the unmodified phenolic resin is 25-35 mm, and the gelation time is 70-80S. Wherein the flow distance and the gelation time are measured with reference to the methods of appendix A2 and A4 of GB/T24411-2009 standard.

Preferably, the amount of the zinc phosphate is 0.1-0.5% of the mass of the steel fiber or the iron powder. The purity of the zinc phosphate is higher than 95%, the pH value is 7-8, and the zinc phosphate plays an important role in passivating the active surface of the ferrous material.

Preferably, the dosage of the cerium trifluoride accounts for 0.1-0.5% of the mass of the steel fiber or the iron powder. Wherein, the purity of the cerium trifluoride is more than 96 percent, and the cerium trifluoride rare earth compound has good effect on improving the corrosion resistance of the metal type friction material.

Preferably, the drying temperature is 60-70 ℃.

Furthermore, 8-12 parts of binder is contained in the copper-free metal friction material. The binder is selected from unmodified phenolic resins.

Further, the inorganic fibers are selected from the group consisting of mineral fibers and ceramic fibers.

Preferably, the weight part of any one component in the composition of the mineral fibers and the ceramic fibers (relative to the total weight of the copper-free metal friction material) is higher than 2 parts and lower than 18 parts.

Preferably, the fiber length of the mineral fiber is 0.45-0.70 mm. The fiber length of the ceramic fiber is 0.25-0.85 mm.

Further, the organic conditioning agent is selected from the group consisting of a friction powder and a tire powder.

Preferably, the weight part of any one component in the composition of the friction powder and the tire powder (relative to the total weight of the copper-free metal friction material) is higher than 1 part and lower than 6 parts.

Preferably, the friction powder is solidified and crushed particles of cashew nut shell oil modified phenolic resin, and the particle size is 0.15-0.85 mm.

Preferably, the diameter of the tire powder is 100-800 mu m, the moisture content is less than 1.0%, and the density is 2.2-2.4 g/cm³。

Further, the friction enhancer is a combination of flake iron oxide and alpha-alumina.

Preferably, the alpha-alumina accounts for 0.5 to 5 parts by weight, the purity is higher than 99.0 percent, and the diameter is less than 5 mu m;

preferably, the iron oxide is 5-14.5 parts by weight and is of a sheet structure, the sheet diameter is 5-45 mu m, the purity is higher than 90.0%, and the water-resisting property of the friction surface is improved by the sheet structure component.

Further, the anti-friction agent is a composition of crystalline flake graphite, synthetic graphite, tin sulfide and antimony sulfide.

Preferably, the flake graphite is 1-5 parts by weight and is of a flake structure, the flake diameter is 45-250 mu m, the purity is higher than 90.0%, and the water resistance of the friction surface is improved by the flake structure component.

Preferably, the synthetic graphite is 1-5 parts by weight, has a granular structure and has a particle size of 150-600 μm.

Preferably, the tin sulfide accounts for 1-5 parts by weight, and the purity is over 90%.

Preferably, the antimony sulfide accounts for 4-10 parts by weight, and the purity is over 95%.

Further, the filler is a combination of glass flake, calcium hydroxide and barite.

Preferably, the weight part of the glass flake is 1-5 parts, and the sheet diameter is less than 75 μm.

Preferably, the calcium hydroxide has a purity higher than 96.0% and a particle size of 5-45 μm.

Preferably, the weight part of the barite is 5-19 parts, the diameter is 35-75 μm, and the content of barium sulfate is higher than 90%.

Further, in the step (1), the preparation of the copper-free metal friction material is prepared by mixing materials in two steps, wherein the first step is mixing materials: mixing and uniformly stirring the steel fibers subjected to the rust prevention treatment and the materials except the iron powder subjected to the rust prevention treatment;

and a second step of mixing materials: and adding the steel fiber subjected to the rust prevention treatment and the iron powder subjected to the rust prevention treatment into the mixed material, and uniformly stirring to obtain the copper-free metal friction material. The uniform mixing of all the components can be realized through two-step mixing, and the rust-proof treatment structure of the ferrous material cannot be damaged.

Further, the hot-pressing forming pressure in the step (2) is 6-15 MPa, the hot-pressing time is 100-400 s, and the hot-pressing temperature is 145-165 ℃.

The bedding material is a conventional formula material in the field, and the purpose of adding the bedding material is to increase the shear strength, insulate heat and have certain noise reduction effect.

Preferably, the using amount of the cushion material accounts for 7-12% of the total mass of the friction material mixture and the cushion material.

Preferably, the bedding material comprises the following raw material components in percentage by mass: 15-20% of phenolic resin, 15-30% of steel fiber, 3-7% of tire powder, 3-5% of alpha-alumina, 22-40% of calcium carbonate, 10-25% of mineral fiber and 5-10% of coke powder. Wherein, the phenolic resin, the steel fiber, the tire powder and the alpha-alumina are correspondingly consistent with the corresponding components in the friction material.

The flow distance of the phenolic resin is 25-30 mm, and the gelation time is 80-90S. Wherein the flow distance and the gelation time are measured with reference to the methods of appendix A2 and A4 of GB/T24411-2009 standard.

The diameter of the tire powder is 100-800 mu m, the diameter of the alpha-alumina is less than 5 mu m, the granularity of the calcium carbonate is 45-75 mu m, the length of the mineral fiber is 0.45-0.70 mm, and the diameter of the coke powder is 150-850 mu m.

Preferably, the heat treatment is to bake the demolded brake pad at 180 ℃ for 2-3 hours and 250 ℃ for 3-6 hours in sequence, and then cool the brake pad to room temperature.

Further, the post-treatment in the step (4) comprises the working procedures of grinding, grooving, chamfering and spraying, wherein the grinding, grooving, chamfering and spraying all belong to the conventional processes in the field. Preferably, the post-treatment in step (4) further includes a rust-proof treatment process.

Further, the rust prevention treatment process in the step (4) comprises the following steps:

a. spraying calcium hydroxide solution on the surface and the side surface of the brake pad after grinding, grooving and chamfering, and drying;

b. continuously spraying a KH-550 silane coupling agent on the surface and the side surface of the brake pad and drying to form a transparent sealing layer;

c. and c, spraying a calcium hydroxide solution on the surface of the brake pad treated in the step b.

Preferably, the pH of the calcium hydroxide solution is greater than 9. The purpose of spraying the calcium hydroxide solution is to ensure an alkaline environment on the brake pad surface.

Preferably, the amount of the KH-550 silane coupling agent sprayed in step b is such that the thickness of the transparent sealing layer formed is 0.5-50 μm.

The invention also provides the brake pad prepared by the method.

The invention also protects the copper-free metal friction material adopted in the method, which comprises the following raw material components in parts by weight: 7-15 parts of a binder, 5-20 parts of inorganic fibers, 2-7 parts of an organic regulator, 5.5-15 parts of a friction enhancer, 7-20 parts of a friction reducer, 6-20 parts of a filler, 5-40 parts of steel fibers subjected to rust prevention treatment and 5-15 parts of iron powder subjected to rust prevention treatment. Wherein the raw material components are in accordance with the aforementioned definitions.

In the preparation method, through adding an antirust process, a calcium hydroxide solution with the pH value of more than 9 and a KH-550 silane coupling agent are used in combination, a compact isolation layer is formed on the interface and the side surface of the friction material of the brake pad, and the material is transparent and extremely thin and does not influence the appearance and the braking performance. The insulating layer prevents water vapor and oxygen in the air from entering, prevents metal components in the friction material from being oxidized and corroded, and further improves the storage and transportation period and the oxidation resistance of the friction material.

In the invention, the steel fiber and the iron powder which are subjected to rust prevention treatment are added, and the steel fiber and the iron powder are wrapped by phenolic resin, metal passivation material zinc phosphate and rare earth compound cerium trifluoride through KH-550 silane coupling agent. In the hot pressing process, the phenolic resin and the silane coupling agent wrap the zinc phosphate and the cerium trifluoride on the surfaces of the steel fibers and the iron powder and isolate the zinc phosphate and the cerium trifluoride from oxygen and moisture in the air, so that the oxidation resistance and the corrosion resistance of the metal friction material in long-term braking application can be effectively improved.

The copper-free metal friction material adopted by the invention adopts various materials with flaky or flaky structures, so that the water-resisting property of the friction material is improved. The sheet material adopted by the invention comprises three materials of sheet iron oxide and glass flakes besides common flake graphite, and the water resistance of the surface of the friction material is improved together. The scale graphite not only improves the surface water resistance of the friction material, but also can obviously improve the brake life of the friction material. The calcium hydroxide adopted by the invention ensures that the peripheries of the steel fiber and the iron powder components are in an alkaline environment, and improves the antirust capacity of the friction material.

In a word, the brake pad of the invention can obviously improve the storage and transportation period and the oxidation resistance of the friction material in the brake pad through the rust-proof treatment; meanwhile, the brake block is made of a copper-free metal friction material, so that the brake block has the following technical effects: (1) the antirust capacity of the copper-free metal friction material in the long-term brake application process is improved; (2) the storage period of the copper-free metal friction material is remarkably increased, the requirement on storage conditions is reduced, and rust prevention can be realized even in severe environment; (3) the heat resistance of the friction material is effectively improved; (4) the formula has no copper, and the environmental protection property of the material is effectively improved.

Drawings

Fig. 1 is a schematic diagram of a method for calculating the average thickness of a brake pad.

Detailed Description

The following description of the embodiments of the present invention is provided by way of specific examples, and other advantages and effects of the present invention will be readily apparent to those skilled in the art from the disclosure herein. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention.

It is to be noted that the features in the following embodiments and examples may be combined with each other without conflict. It is also to be understood that the terminology used in the examples is for the purpose of describing particular embodiments only, and is not intended to limit the scope of the present invention. Test methods in which specific conditions are not specified in the following examples are generally carried out under conventional conditions or under conditions recommended by the respective manufacturers.

When numerical ranges are given in the examples, it is understood that both endpoints of each of the numerical ranges and any value therebetween can be selected unless the invention otherwise indicated. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs and the description of the present invention, and any methods, apparatuses, and materials similar or equivalent to those described in the examples of the present invention may be used to practice the present invention.

The cushion material adopted in the embodiment of the invention is a conventional formula material in the field, and the using amount of the cushion material accounts for 7-12% of the total mass of the friction material mixture and the cushion material. Preferably, the bedding material comprises the following raw material components in percentage by mass: 18% of phenolic resin, 23% of steel fiber, 3% of tire powder, 3% of alpha-alumina, 26% of calcium carbonate, 22% of mineral fiber and 5% of coke powder.

Example 1

The copper-free metal friction material comprises the following raw material components in parts by weight: 7 parts of a binder, 15 parts of inorganic fiber, 5 parts of an organic regulator, 13 parts of a friction enhancer, 13 parts of a friction reducer, 20 parts of a filler, 22 parts of steel fiber subjected to rust prevention treatment and 5 parts of iron powder subjected to rust prevention treatment;

wherein the binder is a phenolic resin; the inorganic fiber comprises 10 parts of mineral fiber and 5 parts of ceramic fiber; the organic regulator comprises 3 parts of friction powder and 2 parts of tire powder; the friction enhancer comprises 3 parts of alpha-alumina and 10 parts of sheet iron oxide; the anti-friction agent comprises 3 parts of crystalline flake graphite, 3 parts of synthetic graphite, 2 parts of tin sulfide and 5 parts of antimony sulfide; the filler comprises 2 parts of glass flakes, 2 parts of calcium hydroxide and 16 parts of barite;

the preparation method of the disc brake pad comprises the following steps:

the method for preparing the brake pad by adopting the friction material with the formula comprises the following steps:

1) mixing materials by a two-step method: first step mixing: mixing and uniformly stirring the steel fibers subjected to the rust prevention treatment and the materials except the iron powder subjected to the rust prevention treatment;

and a second step of mixing materials: adding the steel fiber subjected to the rust prevention treatment and the iron powder subjected to the rust prevention treatment, and uniformly stirring to obtain the copper-free metal friction material. The uniform mixing of all the components can be realized through two-step mixing, and the rust-proof treatment structure of the ferrous material cannot be damaged.

Wherein the treatment steps of the steel fiber or the iron powder subjected to the rust prevention treatment are as follows: respectively spraying a silane coupling agent (accounting for 0.2 percent of the mass of the steel fibers or the iron powder) on the surfaces of the steel fibers or the iron powder, respectively adding a binder (accounting for 1 percent of the mass of the steel fibers or the iron powder), zinc phosphate (accounting for 0.3 percent of the mass of the steel fibers or the iron powder) and cerium trifluoride (accounting for 0.3 percent of the mass of the steel fibers or the iron powder), uniformly stirring, and drying at 60-70 ℃ to obtain the steel fibers or the iron powder subjected to the rust prevention treatment.

2) Hot-press molding: placing the copper-free metal friction material in the step (1) into a hot-pressing die cavity, flattening, then placing the cushion material into the hot-pressing die cavity, flattening, placing a steel backing, loading pressure of 15MPa, hot-pressing time of 300s, hot-pressing temperature of 150 ℃, and demolding after hot-pressing molding;

3) and (3) heat treatment: after demolding, baking the brake block at the baking temperature of 180 ℃ for 2 hours, and then baking the brake block at the baking temperature of 250 ℃ for 3 hours;

4) and grinding, grooving, chamfering and spraying post-treatment to obtain the brake pad.

Example 2

The copper-free metal friction material comprises the following raw material components in parts by weight: 15 parts of binder, 5 parts of inorganic fiber, 2 parts of organic regulator, 15 parts of friction enhancer, 20 parts of antifriction agent, 20 parts of filler, 18 parts of steel fiber subjected to rust prevention treatment and 5 parts of iron powder subjected to rust prevention treatment;

wherein the binder is a phenolic resin; the inorganic fiber comprises 2 parts of mineral fiber and 3 parts of ceramic fiber; the organic regulator comprises 1 part of friction powder and 1 part of tire powder; the friction enhancer comprises 5 parts of alpha-alumina and 10 parts of sheet iron oxide; the anti-friction agent comprises 5 parts of crystalline flake graphite, 5 parts of synthetic graphite, 3 parts of tin sulfide and 7 parts of antimony sulfide; the filler comprises 2 parts of glass flakes, 2 parts of calcium hydroxide and 16 parts of barite;

wherein the treatment steps of the steel fiber or the iron powder subjected to the rust prevention treatment are as follows: respectively spraying a silane coupling agent (accounting for 0.3 percent of the mass of the steel fibers or the iron powder) on the surfaces of the steel fibers or the iron powder, respectively adding a binder (accounting for 2 percent of the mass of the steel fibers or the iron powder), zinc phosphate (accounting for 0.4 percent of the mass of the steel fibers or the iron powder) and cerium trifluoride (accounting for 0.6 percent of the mass of the steel fibers or the iron powder), uniformly stirring, and drying at 60-70 ℃ to obtain the steel fibers or the iron powder subjected to the rust prevention treatment.

The method for preparing the brake pad by adopting the friction material with the formula is the same as the example 1, and is different from the example 1 in that: in the step (2), in the hot-press molding, the loading pressure is 12MPa, the hot-press time is 400s, and the hot-press temperature is 165 ℃; and (3) performing heat treatment, namely demolding the brake block, baking at the baking temperature of 180 ℃ for 2.5 hours, and baking at the baking temperature of 250 ℃ for 3 hours.

Example 3

The copper-free metal friction material comprises the following raw material components in parts by weight: 11 parts of binder, 20 parts of inorganic fiber, 7 parts of organic regulator, 8 parts of friction enhancer, 7 parts of anti-friction agent, 8 parts of filler, 30 parts of steel fiber subjected to rust prevention treatment and 9 parts of iron powder subjected to rust prevention treatment;

wherein the binder is a phenolic resin; the inorganic fibers comprise 13 parts of mineral fibers and 7 parts of ceramic fibers; the organic regulator comprises 1 part of friction powder and 6 parts of tire powder; the friction enhancer comprises 3 parts of alpha-alumina and 5 parts of sheet iron oxide; the anti-friction agent comprises 1 part of crystalline flake graphite, 1 part of synthetic graphite, 1 part of tin sulfide and 4 parts of antimony sulfide; the filler comprises 3 parts of glass flakes, 1 part of calcium hydroxide and 4 parts of barite;

wherein the treatment steps of the steel fiber or the iron powder subjected to the rust prevention treatment are as follows: respectively spraying a silane coupling agent (accounting for 0.3 percent of the mass of the steel fibers or the iron powder) on the surfaces of the steel fibers or the iron powder, respectively adding a binder (accounting for 1.5 percent of the mass of the steel fibers or the iron powder), zinc phosphate (accounting for 0.2 percent of the mass of the steel fibers or the iron powder) and cerium trifluoride (accounting for 0.2 percent of the mass of the steel fibers or the iron powder), uniformly stirring, and drying at 60-70 ℃ to obtain the steel fibers or the iron powder subjected to the rust prevention treatment.

The method for preparing the brake pad by adopting the friction material with the formula is the same as the example 1, and is different from the example 1 in that: in the step (2), in the hot-press molding, the loading pressure is 6MPa, the hot-press time is 400s, and the hot-press temperature is 165 ℃; and (3) performing heat treatment, namely demolding the brake block, baking the demolded brake block at the baking temperature of 180 ℃ for 3 hours, and baking the demolded brake block at the baking temperature of 250 ℃ for 2 hours.

Example 4

The copper-free metal friction material comprises the following raw material components in parts by weight: 10 parts of a binder, 19 parts of inorganic fibers, 5 parts of an organic regulator, 13 parts of a friction enhancer, 13 parts of a friction reducer, 20 parts of a filler, 5 parts of steel fibers subjected to rust prevention treatment and 15 parts of iron powder subjected to rust prevention treatment;

wherein the binder is a phenolic resin; the inorganic fibers comprise 10 parts of mineral fibers and 9 parts of ceramic fibers; the organic regulator comprises 3 parts of friction powder and 2 parts of tire powder; the friction enhancer comprises 3 parts of alpha-alumina and 10 parts of sheet iron oxide; the anti-friction agent comprises 3 parts of crystalline flake graphite, 3 parts of synthetic graphite, 2 parts of tin sulfide and 5 parts of antimony sulfide; the filler comprises 2 parts of glass flakes, 2 parts of calcium hydroxide and 16 parts of barite; the method of treating the rust-preventive treated steel fibers and the rust-preventive treated iron powder was the same as in example 1;

the preparation method of the disc brake pad comprises the following steps:

2) Hot-press molding: placing the copper-free metal friction material in the step (1) into a hot-pressing die cavity, flattening, then placing the cushion material into the hot-pressing die cavity, flattening, placing a steel backing, loading the pressure to be 6MPa, carrying out hot-pressing for 300s, carrying out hot-pressing at the temperature of 150 ℃, and demoulding after hot-pressing forming;

4) grinding, slotting and chamfering the brake pad sample after heat treatment, then spraying a calcium hydroxide solution with the pH value of more than 9 on the surface and the side surface of the brake pad, and drying to ensure the alkaline environment of the surface of the brake pad;

continuously spraying a KH-550 silane coupling agent and drying after drying, and forming a transparent sealing layer on the surface, wherein the thickness of the formed transparent sealing layer is 0.5-50 microns;

and after drying, spraying a calcium hydroxide solution with the pH value of more than 9 again, and drying.

And drying and then carrying out conventional spraying treatment to obtain the brake pad.

Example 5

The copper-free metal friction material comprises the following raw material components in parts by weight: 9 parts of binder, 15 parts of inorganic fiber, 6 parts of organic regulator, 11 parts of friction enhancer, 13 parts of anti-friction agent, 19 parts of filler, 20 parts of steel fiber and 7 parts of iron powder;

wherein the binder is a phenolic resin; the inorganic fiber comprises 10 parts of mineral fiber and 5 parts of ceramic fiber; the organic regulator comprises 3 parts of friction powder and 2 parts of tire powder; the friction enhancer comprises 3 parts of alpha-alumina and 10 parts of sheet iron oxide; the anti-friction agent comprises 3 parts of crystalline flake graphite, 3 parts of synthetic graphite, 2 parts of tin sulfide and 5 parts of antimony sulfide; the filler comprises 3 parts of glass flakes, 3 parts of calcium hydroxide and 13 parts of barite;

the method for preparing the brake pad by adopting the friction material with the formula is the same as the example 4, and is different from the example 4 in that: in the step (2), in the hot-press molding, the loading pressure is 12MPa, the hot-press time is 400s, and the hot-press temperature is 165 ℃; and (3) performing heat treatment, namely demolding the brake block, baking the demolded brake block at the baking temperature of 180 ℃ for 2 hours, and baking the demolded brake block at the baking temperature of 250 ℃ for 3 hours.

The brake pad was prepared using the friction material of the above formulation as in example 4.

Example 6

The copper-free metal friction material comprises the following raw material components in parts by weight: 11 parts of binder, 16 parts of inorganic fiber, 5.5 parts of organic regulator, 5.5 parts of friction enhancer, 7 parts of friction reducer, 6 parts of filler, 40 parts of steel fiber and 9 parts of iron powder;

wherein the binder is a phenolic resin; the inorganic fibers comprise 13 parts of mineral fibers and 3 parts of ceramic fibers; the organic regulator comprises 1 part of friction powder and 4.5 parts of tire powder; the friction enhancer comprises 3 parts of alpha-alumina and 2.5 parts of sheet iron oxide; the anti-friction agent comprises 1 part of crystalline flake graphite, 1 part of synthetic graphite, 1 part of tin sulfide and 4 parts of antimony sulfide; the filler comprises 2 parts of glass flakes, 1 part of calcium hydroxide and 3 parts of barite;

the method for preparing the brake pad by adopting the friction material with the formula is the same as the example 4, and is different from the example 4 in that: in the step (2), in the hot-press molding, the loading pressure is 8MPa, the hot-press time is 400s, and the hot-press temperature is 165 ℃; and (3) performing heat treatment, namely demolding the brake block, baking the demolded brake block at the baking temperature of 180 ℃ for 2 hours, and baking the demolded brake block at the baking temperature of 250 ℃ for 2 hours.

Comparative example 1

The copper-free metal friction material comprises the following raw material components in parts by weight: 7 parts of a binder, 15 parts of inorganic fiber, 5 parts of an organic regulator, 13 parts of a friction enhancer, 13 parts of a friction reducer, 20 parts of a filler, 22 parts of steel fiber and 5 parts of iron powder;

the preparation method of the disc brake pad comprises the following steps:

1) mixing materials by a two-step method: first step mixing: mixing and uniformly stirring the materials except the steel fiber and the iron powder;

and a second step of mixing materials: adding steel fiber and iron powder and stirring uniformly to obtain the copper-free metal friction material.

Comparative example 2

The copper-free metal friction material comprises the following raw material components in parts by weight: 15 parts of binder, 5 parts of inorganic fiber, 2 parts of organic regulator, 15 parts of friction enhancer, 20 parts of anti-friction agent, 20 parts of filler, 18 parts of steel fiber and 5 parts of iron powder;

the method for preparing the brake pad by adopting the friction material with the formula is the same as the comparative example 1, and is different from the comparative example 1 in that: in the step (2), in the hot-press molding, the loading pressure is 12MPa, the hot-press time is 400s, and the hot-press temperature is 165 ℃; and (3) performing heat treatment, namely demolding the brake block, baking at the baking temperature of 180 ℃ for 2.5 hours, and baking at the baking temperature of 250 ℃ for 3 hours.

Comparative example 3

The copper-free metal friction material comprises the following raw material components in parts by weight: 11 parts of binder, 20 parts of inorganic fiber, 7 parts of organic regulator, 8 parts of friction enhancer, 7 parts of anti-friction agent, 8 parts of filler, 30 parts of steel fiber and 9 parts of iron powder;

the method for preparing the brake pad by adopting the friction material with the formula is the same as the comparative example 1, and is different from the comparative example 1 in that: in the step (2), in the hot-press molding, the loading pressure is 6MPa, the hot-press time is 400s, and the hot-press temperature is 165 ℃; and (3) performing heat treatment, namely demolding the brake block, baking the demolded brake block at the baking temperature of 180 ℃ for 3 hours, and baking the demolded brake block at the baking temperature of 250 ℃ for 2 hours.

Performance testing

The brake pads obtained in examples 1 to 6 and comparative examples 1 to 3 were tested for performance and rust prevention, respectively.

Wherein the brake pad storage condition: the temperature and the humidity are respectively 30 ℃ and 90% humidity, and the time of D-level rusting is recorded, namely the storage time;

the rust prevention detection method comprises the following steps: soaking the brake pads and the brake disc with the degreased surface in a 5.0% sodium chloride solution for 48h, taking out the soaked brake pads and brake disc, placing the brake pads and brake disc in a constant temperature and humidity environment for 48h, observing the corrosion state, and judging the corrosion degree according to the number of rust points and the rust area.

The brake pad was subjected to a SAE J2522 bench test, as shown in Table 1, wherein the SAE J2522 nominal coefficient of friction is the average of the coefficients of friction in all chapters, except the high temperature coefficient, which is typically used to characterize the overall coefficient of friction level of the material. SAE J2522 abrasion refers to the difference between the average thickness before and after the procedure test, and the average thickness is calculated by averaging 4 points and 8 points of each brake pad as shown in FIG. 1.

TABLE 1

Wherein class a-rust almost all over the surface (rust area > 60%), rust depth;

class B-large scale rusting (rusting area greater than 30%);

class C-rusting in a certain area (rusting area greater than 5%);

grade D-small area rust (rust area < 5%);

grade E-no rust.

In conclusion, the brake pad prepared by the copper-free metal friction material subjected to the rust prevention treatment in the embodiments 1-3 of the invention has good braking performance, and the rust prevention capability is obviously improved compared with the comparison in the comparison ratios 1 to 3; in examples 5 to 6 of the present invention, the rust-proofing step was added, so that the brake pad produced had substantially no rust and had improved rust-proofing properties. In embodiment 4 of the invention, the brake pad prepared by adding the rust prevention process and adopting the copper-free metal friction material subjected to rust prevention treatment has better rust prevention performance and good brake performance. In a word, compared with the brake pad prepared by the prior art, the brake pad prepared by the invention has better antirust performance, and the service life of the friction material is slightly prolonged.

The foregoing embodiments are merely illustrative of the principles and utilities of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or change the above-mentioned embodiments without departing from the spirit and scope of the present invention. Accordingly, it is intended that all equivalent modifications or changes which can be made by those skilled in the art without departing from the spirit and technical spirit of the present invention be covered by the claims of the present invention.

Claims

1. A method of making a brake pad comprising the steps of:

(1) preparing a copper-free metal friction material;

(3) cooling the demolded sample to room temperature after heat treatment;

(4) carrying out post-treatment on the sample treated in the step (3) to prepare a brake pad;

the copper-free metal friction material comprises the following raw material components in parts by weight: 7-15 parts of a binder, 5-20 parts of inorganic fibers, 2-7 parts of an organic regulator, 5.5-15 parts of a friction enhancer, 7-20 parts of a friction reducer, 6-20 parts of a filler, 5-40 parts of steel fibers subjected to rust prevention treatment and 5-15 parts of iron powder subjected to rust prevention treatment;

the binder is selected from unmodified phenolic resins;

the inorganic fibers are selected from the group consisting of mineral fibers and ceramic fibers;

the organic conditioning agent is selected from a composition of friction powder and tire powder;

the friction enhancer is a composition of flake iron oxide and alpha-alumina;

the anti-friction agent is a composition of crystalline flake graphite, synthetic graphite, tin sulfide and antimony sulfide;

the filler is a composition of calcium hydroxide, glass flakes and barite;

the rust-proofing treatment of the steel fiber or the iron powder respectively comprises the following steps: respectively spraying a silane coupling agent on the surfaces of the steel fibers or the iron powder, respectively adding a binder, zinc phosphate and cerium trifluoride, uniformly stirring and drying to obtain the steel fibers or the iron powder subjected to the rust prevention treatment;

wherein the amount of the cushion material in the step (2) accounts for 7-12% of the total mass of the friction material mixture and the cushion material; the bedding material comprises the following raw material components in percentage by mass: 15-20% of phenolic resin, 15-30% of steel fiber, 3-7% of tire powder, 3-5% of alpha-alumina, 22-40% of calcium carbonate, 10-25% of mineral fiber and 5-10% of coke powder; the phenolic resin, the steel fiber, the tire powder and the alpha-alumina in the bedding material are correspondingly consistent with the corresponding components in the friction material;

the rust-preventive treatment in the step (4) comprises the steps of:

c. and c, spraying a calcium hydroxide solution with the pH value of more than 9 on the surface of the brake pad treated in the step b.

2. The method of claim 1, wherein the post-treatment in step (4) comprises grinding, grooving, chamfering, rust prevention, spraying.

3. The method of claim 1, comprising any one or more of the following features:

the dosage of the silane coupling agent accounts for 0.1-0.5% of the mass of the steel fiber or the iron powder;

the amount of the binder in the antirust treatment accounts for 1-2% of the mass of the steel fiber or the iron powder;

the using amount of the zinc phosphate accounts for 0.1-0.5% of the mass of the steel fiber or the iron powder;

the dosage of the cerium trifluoride accounts for 0.1-0.5% of the mass of the steel fiber or the iron powder.

4. The method of claim 3, wherein the amount of the KH-550 silane coupling agent sprayed in step b is such that the thickness of the transparent sealant layer formed is 0.5 to 50 μm.

5. Brake pads made by the method of any of claims 1 to 4.

6. A copper-free metal friction material for use in the method of claim 1.