Iron-based powder metallurgy brake shoe friction body, iron-based powder metallurgy brake shoe and preparation method and application of iron-based powder metallurgy brake shoe friction body

Abstract

The invention discloses an iron-based powder metallurgy brake shoe friction body, an iron-based powder metallurgy brake shoe and a preparation method and application of the iron-based powder metallurgy brake shoe friction body and the iron-based powder metallurgy brake shoe, and relates to the technical field of composition brake shoes, and the iron-based powder metallurgy brake shoe friction body comprises, by mass, 60-75% of a matrix component, 3-9% of a reinforcing component, 10-14% of a lubricating component and 12-18% of a friction component; wherein the matrix component comprises iron powder, steel fibers and copper powder, the reinforcing component comprises nickel powder, molybdenum powder and tin powder, the lubricating component comprises graphite and sulfide, and the friction component comprises chromite, aluminum oxide, zirconium oxide and carbide. The iron-based powder metallurgy brake shoe friction body can solve the problems of insufficient braking force, short service life and the like caused by overheating of a wheel tread during high-speed braking of a composition brake shoe.

Description

Technical Field

[0001] This invention relates to the field of synthetic brake shoe technology, and in particular to an iron-based powder metallurgy brake shoe friction element, an iron-based powder metallurgy brake shoe, its preparation method and application. Background Technology

[0002] Traditional synthetic brake shoes perform well in wheel braking at speeds below 120 km / h. However, when the speed increases to 140-160 km / h or higher, problems such as insufficient heat resistance, accelerated friction coefficient decay, increased brake shoe wear, and shortened lifespan become prominent, leading to a significant decrease in braking force and making it difficult to meet high-speed braking requirements. Because of the poor heat resistance and thermal conductivity of its matrix material, synthetic brake shoes are prone to thermal fade during braking. This causes the heat generated by braking friction to concentrate on the wheel tread, altering the microstructure of the wheel material. In severe cases, this can lead to thermal cracking, thermal crazing, or even thermal delamination of the tread. The delamination of wheel material may embed into the brake shoe surface, forming a metal inlay, further deteriorating the braking performance and lifespan of the brake shoe. Summary of the Invention

[0003] The purpose of this invention is to provide an iron-based powder metallurgy brake shoe friction element, an iron-based powder metallurgy brake shoe, its preparation method and application. This iron-based powder metallurgy brake shoe friction element can solve the problems of insufficient braking force and short service life caused by overheating of the wheel tread at high speeds in synthetic brake shoes.

[0004] To achieve the above objectives, the first aspect of the present invention provides an iron-based powder metallurgy brake shoe friction body, wherein, based on the mass percentage of the iron-based powder metallurgy brake shoe friction body, it comprises 60-75% matrix components, 3-9% reinforcing components, 10-14% lubricating components, and 12-18% friction components. The matrix component comprises iron powder, steel fiber and copper powder; the reinforcing component comprises nickel powder, molybdenum powder and tin powder; the lubricating component comprises graphite and sulfides; and the friction component comprises chromite, alumina, zirconium oxide and carbides.

[0005] Compared with existing technologies, by using iron powder, steel fiber, and copper powder as matrix components, the higher melting point and specific heat capacity of iron and steel (the specific heat capacity of iron and steel is 0.46 × 10⁻⁶) can achieve better results. 3 J / (J / kg.℃), the specific heat capacity of copper is 0.39×10 3The J / (J / kg.℃) ratio gives the iron-based powder metallurgy brake shoe friction body, made of iron powder and steel fiber, high compressive strength, shear strength, and high heat storage capacity. Meanwhile, the copper powder in the matrix components has high ductility, high thermal conductivity, and resistance to wet wear and extreme cold. This helps reduce noise generated during braking, decreases the heat and high temperature generated during braking friction, prevents the decline in matrix strength due to high frictional temperatures, and thus avoids the degradation of brake shoe friction performance, maintaining the stability of the friction coefficient.

[0006] Furthermore, the iron-based powder metallurgy brake shoe friction body of the present invention uses nickel powder, molybdenum powder and tin powder as reinforcing components. The nickel powder, molybdenum powder and tin powder are mixed with iron powder and copper powder in the matrix components to form a ternary or multi-element iron-copper-based alloy. When the content of the matrix components and reinforcing components is controlled within a specific range, the high temperature resistance, impact toughness, wet wear resistance and anti-fading ability of the iron-based powder metallurgy brake shoe friction body can be significantly improved, thereby maintaining the stability of the high temperature friction coefficient and extending the service life of the iron-based powder metallurgy brake shoe under high temperature braking conditions.

[0007] Furthermore, the iron-based powder metallurgy brake shoe friction body of the present invention contains specific amounts of matrix components, reinforcing components, lubricating components, and friction components. Under the synergistic effect of each component, the iron-based powder metallurgy brake shoe can effectively avoid the decline of the friction coefficient caused by overheating during high-speed braking (such as 140-160km / h), maintain the stability of the friction coefficient, and thus improve braking performance. At the same time, the iron-based powder metallurgy brake shoe friction body has the characteristics of low wear, long service life, and strong heat resistance, avoiding defects such as thermal cracks, thermal crazing, thermal peeling, and brake shoe metal embedding on the wheel tread during high-speed braking.

[0008] Further, based on the mass percentage of the iron-based powder metallurgy brake shoe friction body, the content of iron powder is 20-30%, the content of steel fiber is 20-30%, the content of copper powder is 10-20%; the content of nickel powder is 1-3%, the content of molybdenum powder is 1-3%, the content of tin powder is 1-3%; the content of graphite is 8-10%, the content of sulfide is 2-4%; the content of chromite is 9-12%, the content of alumina is 1-2%, the content of zirconium oxide is 1-2%, and the content of carbide is 1-2%.

[0009] In this invention, when the contents of iron powder, steel fiber, copper powder, nickel powder, molybdenum powder, tin powder, graphite, sulfides, chromite, alumina, zirconium oxide, and carbides in the iron-based powder metallurgy brake shoe friction body meet the above-mentioned ranges, the compressive strength and shear strength of the iron-based powder metallurgy brake shoe friction body can be further improved; at the same time, it is beneficial to reduce noise, improve the heat resistance and friction performance of the iron-based powder metallurgy brake shoe friction body, avoid the decline of the friction coefficient due to overheating, maintain the stability of the friction coefficient, improve braking ability, reduce the wear of the iron-based powder metallurgy brake shoe friction body, and extend its service life.

[0010] Furthermore, the iron powder has a particle size ≤75μm and an oxygen content ≤1.2wt%; the steel fiber has a diameter ≤0.1mm and a length ≤1mm; the copper powder has a particle size ≤75μm and an oxygen content ≤0.2wt%; the nickel powder has a particle size ≤75μm and a total nickel-cobalt content ≥99wt%; the molybdenum powder has a particle size ≤30μm and a molybdenum content ≥99wt%; and the tin powder has a particle size ≤75μm and a tin content ≥99wt%.

[0011] In this invention, when the particle size and oxygen content of iron powder, the diameter and length of steel fibers, the particle size and oxygen content of copper powder, the particle size and total nickel-cobalt content of nickel powder, the particle size and molybdenum content of molybdenum powder, and the particle size and tin content of tin powder meet the above-mentioned ranges, the compressive strength, shear strength, and heat resistance of the iron-based powder metallurgy brake shoe friction body can be further improved; at the same time, the running-in performance and friction stability of the iron-based powder metallurgy brake shoe friction body can be improved.

[0012] Furthermore, the graphite has a particle size of 150-500 μm and a carbon content of ≥99 wt%; the sulfide has a particle size of ≤300 μm and a purity of ≥98 wt%.

[0013] In this invention, when the particle size and carbon content of graphite, and the particle size and purity of sulfides meet the above-mentioned ranges, the iron-based powder metallurgy brake shoe friction body has excellent lubrication performance, which can prevent a large number of sparks from occurring when the vehicle brakes at high speeds of 140km / h-160km / h, thereby suppressing the degradation of the high-temperature performance of the iron-based powder metallurgy brake shoe friction body and maintaining the stability of the friction coefficient.

[0014] Furthermore, the chromite has a particle size of 45-300 μm and a chromium oxide content of 25 wt%-40 wt%; the alumina has a particle size of ≤75 μm and an alumina content of ≥96 wt%; the zirconium oxide has a particle size of ≤75 μm, a zirconium oxide content of ≥90 wt%, and a yttrium oxide content of ≥7 wt%; and the carbide has a particle size of ≤300 μm and a carbide content of ≥90 wt%.

[0015] In this invention, when the particle size and chromium oxide content of chromite, the particle size and aluminum oxide content of alumina, the particle size of zirconium oxide, the content of zirconium oxide and yttrium oxide, and the particle size and carbide content of carbides meet the above-mentioned ranges, the friction coefficient of the iron-based powder metallurgy brake shoe friction body under different working conditions (i.e., different braking speeds, braking pressures, and axle loads) can be further improved, the heat resistance of the high-temperature braking of the iron-based powder metallurgy brake shoe friction body can be enhanced, the wear of the iron-based powder metallurgy brake shoe friction body can be indirectly reduced, and the stability of the friction coefficient can be guaranteed.

[0016] Furthermore, the sulfide is selected from at least one of antimony sulfide, molybdenum disulfide, copper sulfide, tin sulfide, zinc sulfide, and manganese sulfide.

[0017] Furthermore, the carbide is selected from at least one of silicon carbide, boron carbide, tungsten carbide, and titanium carbide.

[0018] A second aspect of the present invention provides a method for preparing iron-based powder metallurgy brake shoes, comprising the following steps: Prepare each component according to the composition of the iron-based powder metallurgy brake shoe friction body described above. The components of the iron-based powder metallurgy brake shoe friction body, excluding graphite, are premixed with a liquid hydrocarbon medium, and then graphite is added for secondary mixing to obtain a mixture. The tile back is placed at the bottom of the mold cavity, and the mixture is added into the mold containing the tile back and pressed to obtain a pressed blank with a tile back. The back-pressed blank with the tile is sintered under pressure in a protective gas atmosphere, and then cooled to obtain a sintered tile. The sintered tiles are then subjected to repressing to obtain iron-based powder metallurgy brake shoes.

[0019] Compared with existing technologies, this invention premixes the components of the iron-based powder metallurgy brake shoe friction body, excluding graphite, with a liquid hydrocarbon medium, and then adds graphite for secondary mixing to obtain a mixture. The mixing method of this invention prevents dust generation, improves mixing efficiency, and ensures a more uniform distribution of components. The mixture is then added to a mold containing the back of the brake shoe for pressing to obtain a backed blank. This backed blank is then pressure-sintered under a protective gas atmosphere to obtain a sintered brake shoe. Pressure sintering avoids sidewall cracks caused by the free expansion of the blank. Re-pressing the sintered brake shoe further improves its density. The preparation method of this invention improves the compressive strength, shear strength, and heat resistance of the iron-based powder metallurgy brake shoe friction body. It also improves the heat resistance and frictional stability of the iron-based powder metallurgy brake shoe friction body, further reduces wear, and extends its service life.

[0020] Furthermore, the amount of the liquid hydrocarbon medium used is 0.3-0.8 wt% of the total weight of the friction body.

[0021] Furthermore, the liquid hydrocarbon medium is aviation kerosene.

[0022] In this invention, when the amount and type of liquid hydrocarbon medium used meet the above-mentioned limitations, the dust generated by the raw materials can be effectively avoided.

[0023] Furthermore, the protective gas is an ammonia decomposition gas.

[0024] Furthermore, the premixing treatment time is greater than or equal to 60 minutes, and the secondary mixing treatment duration is greater than or equal to 30 minutes.

[0025] Furthermore, the pressing pressure is 300-600 MPa.

[0026] Furthermore, the pressure sintering temperature is 900-1100℃, the sintering time is 2-6h, and the sintering pressure is 4.5-7.5MPa.

[0027] In this invention, when the conditions of premixing treatment, secondary mixing treatment, pressing pressure, pressure sintering temperature, pressure sintering time, and pressure sintering meet the above ranges, it is beneficial to improve the compressive strength, shear strength, and heat resistance of the iron-based powder metallurgy brake shoe friction body; at the same time, it improves the heat resistance and friction stability of the iron-based powder metallurgy brake shoe friction body, and further reduces the wear of the iron-based powder metallurgy brake shoe friction body, thus extending its service life.

[0028] Furthermore, the pressure of the repeated pressure is 3-6 t / cm. 3 ​​.

[0029] A third aspect of the present invention provides an iron-based powder metallurgy brake shoe, comprising the above-mentioned iron-based powder metallurgy brake shoe friction body and backing, and / or prepared by the above-mentioned preparation method.

[0030] Compared with the prior art, the beneficial effects of the iron-based powder metallurgy brake shoe provided by the present invention are the same as the beneficial effects of the iron-based powder metallurgy brake shoe friction body described in the above technical solution, and will not be repeated here.

[0031] The fourth aspect of the present invention provides the above-mentioned iron-based powder metallurgy brake shoe friction body, or the application of the above-mentioned iron-based powder metallurgy brake shoe in high-speed braking.

[0032] Compared with the prior art, the beneficial effects of the iron-based powder metallurgy brake shoe friction body provided by the present invention, or the application of iron-based powder metallurgy brake shoes in high-speed braking, are the same as the beneficial effects of the iron-based powder metallurgy brake shoe friction body described in the above technical solutions, and will not be repeated here. Attached Figure Description

[0033] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this invention, illustrate exemplary embodiments of the invention and are used to explain the invention, but do not constitute an undue limitation of the invention. In the drawings: Figure 1 This is a schematic diagram of the iron-based powder metallurgy brake shoe friction body in an embodiment of the present invention.

[0034] Figure 2 This is a schematic diagram of the limiting pressure sintering in an embodiment of the present invention.

[0035] Figure label: 1-Iron-based powder metallurgy brake shoe friction body, 2-Shoe back. Detailed Implementation

[0036] To make the technical problems to be solved, the technical solutions, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0037] In a first aspect, embodiments of the present invention provide an iron-based powder metallurgy brake shoe friction body, wherein, based on the mass percentage of the iron-based powder metallurgy brake shoe friction body, it comprises 60-75% matrix components, 3-9% reinforcing components, 10-14% lubricating components, and 12-18% friction components. The matrix component comprises iron powder, steel fiber and copper powder; the reinforcing component comprises nickel powder, molybdenum powder and tin powder; the lubricating component comprises graphite and sulfides; and the friction component comprises chromite, alumina, zirconium oxide and carbides.

[0038] By employing the above technical solution and using iron powder, steel fiber, and copper powder as matrix components, the high melting point and large specific heat capacity of iron and steel (the specific heat capacity of iron and steel is 0.46 × 10⁻⁶) are advantageous. 3 J / (J / kg.℃), the specific heat capacity of copper is 0.39×10 3 The J / (J / kg.℃) ratio gives the iron-based powder metallurgy brake shoe friction body, made of iron powder and steel fiber, high compressive strength, shear strength, and high heat storage capacity. Meanwhile, the copper powder in the matrix components has high ductility, high thermal conductivity, and resistance to wet wear and extreme cold. This helps reduce noise generated during braking, decreases the heat and high temperature generated during braking friction, prevents the decline in matrix strength due to high frictional temperatures, and thus avoids the degradation of brake shoe friction performance, maintaining the stability of the friction coefficient.

[0039] Furthermore, when nickel powder, molybdenum powder, and tin powder are used as reinforcing components in the friction body of iron-based powder metallurgy brake shoes, the nickel powder, molybdenum powder, and tin powder are mixed with iron powder and copper powder in the matrix components to form a ternary or multi-element iron-copper-based alloy. When the content of the matrix components and reinforcing components is controlled within a specific range, the high-temperature strength, impact toughness, wet wear resistance, and anti-fading ability of the friction body of iron-based powder metallurgy brake shoes can be significantly improved, thereby maintaining the stability of the high-temperature friction coefficient and extending the service life of iron-based powder metallurgy brake shoes under high-temperature braking conditions.

[0040] Furthermore, the iron-based powder metallurgy brake shoe friction body of the present invention contains specific amounts of matrix components, reinforcing components, lubricating components, and friction components. Under the synergistic effect of each component, the iron-based powder metallurgy brake shoe can effectively avoid the decline of the friction coefficient caused by overheating during high-speed braking (such as 140-160km / h), maintain the stability of the friction coefficient, and thus improve braking performance. At the same time, the iron-based powder metallurgy brake shoe friction body has the characteristics of low wear, long service life, and strong heat resistance, avoiding defects such as thermal cracks, thermal crazing, thermal peeling, and brake shoe metal embedding on the wheel tread during high-speed braking.

[0041] In some embodiments, based on the mass percentage of the iron-based powder metallurgy brake shoe friction element, the content of iron powder is 20-30%, the content of steel fiber is 20-30%, the content of copper powder is 10-20%; the content of nickel powder is 1-3%, the content of molybdenum powder is 1-3%, the content of tin powder is 1-3%; the content of graphite is 8-10%, the content of sulfides is 2-4%; the content of chromite is 9-12%, the content of alumina is 1-2%, the content of zirconium oxide is 1-2%, and the content of carbides is 1-2%.

[0042] By adopting the above technical solution, when the contents of iron powder, steel fiber, copper powder, nickel powder, molybdenum powder, tin powder, graphite, sulfides, chromite, alumina, zirconium oxide, and carbides in the iron-based powder metallurgy brake shoe friction body meet the above-mentioned ranges, the compressive strength and shear strength of the iron-based powder metallurgy brake shoe friction body can be further improved; at the same time, it is beneficial to reduce noise, improve the heat resistance and friction performance of the iron-based powder metallurgy brake shoe friction body, avoid the decline of the friction coefficient due to overheating, maintain the stability of the friction coefficient, improve braking ability, reduce the wear of the iron-based powder metallurgy brake shoe friction body, and extend its service life.

[0043] For example, based on the mass percentage of the iron-based powder metallurgy brake shoe friction element, the content of the iron powder can be 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, or 30%, or any range formed by any two of the above values; the content of the steel fiber can be 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, or 30%, or any range formed by any two of the above values; the content of the copper powder can be 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, or 20%, or any range formed by any two of the above values; the content of the nickel powder can be 1%, 1.5%, 2%, 2.5%, or 3%, or any range formed by any two of the above values; the content of the molybdenum powder can be 1%, 1.5%, 2%, 2.5%, or 3%, or... The content of the tin powder can be 1%, 1.5%, 2%, 2.5%, or 3%, or any two of the above-mentioned values; the content of the graphite can be 8%, 8.5%, 9%, 9.5%, or 10%, or any two of the above-mentioned values; the content of the sulfide can be 2%, 2.5%, 3%, 3.5%, or 4%, or any two of the above-mentioned values; the content of the chromite can be 9%, 10%, 11%, or 12%, or any two of the above-mentioned values; the content of the alumina can be 1%, 1.5%, or 2%, or any two of the above-mentioned values; the content of the zirconium oxide can be 1%, 1.5%, or 2%, or any two of the above-mentioned values; the content of the carbide can be 1%, 1.5%, or 2%, or any two of the above-mentioned values.

[0044] Preferably, based on the mass percentage of the iron-based powder metallurgy brake shoe friction body, the content of iron powder is 22-28%, the content of steel fiber is 23-27%, the content of copper powder is 10-20%; the content of nickel powder is 2-3%, the content of molybdenum powder is 2-3%, the content of tin powder is 2-3%; the content of graphite is 8-10%, the content of sulfide is 2-4%; the content of chromite is 9-12%, the content of alumina is 1-2%, the content of zirconium oxide is 1-2%, and the content of carbide is 1-2%.

[0045] In some embodiments, the iron powder has a particle size ≤75μm and an oxygen content ≤1.2wt%; the steel fiber has a diameter ≤0.1mm and a length ≤1mm; the copper powder has a particle size ≤75μm and an oxygen content ≤0.2wt%; the nickel powder has a particle size ≤75μm and a total nickel-cobalt content ≥99wt%; the molybdenum powder has a particle size ≤30μm and a molybdenum content ≥99wt%; and the tin powder has a particle size ≤75μm and a tin content ≥99wt%.

[0046] By adopting the above technical solution, when the particle size and oxygen content of iron powder, the diameter and length of steel fibers, the particle size and oxygen content of copper powder, the particle size and total nickel-cobalt content of nickel powder, the particle size and molybdenum content of molybdenum powder, and the particle size and tin content of tin powder meet the above ranges, the compressive strength, shear strength, and heat resistance of the iron-based powder metallurgy brake shoe friction body can be further improved; at the same time, the running-in performance and friction stability of the iron-based powder metallurgy brake shoe friction body can be improved.

[0047] In some embodiments, the graphite has a particle size of 150-500 μm and a carbon content of ≥99 wt%; the sulfide has a particle size of ≤300 μm and a purity of ≥98 wt%.

[0048] When the above technical solution is adopted, the lubrication performance of the iron-based powder metallurgy brake shoe friction body is excellent when the particle size and carbon content of graphite and the particle size and purity of sulfides meet the above range. This can prevent a large number of sparks from occurring when the vehicle brakes at high speeds of 140km / h-160km / h, thereby suppressing the degradation of the high-temperature performance of the iron-based powder metallurgy brake shoe friction body and maintaining the stability of the friction coefficient.

[0049] In some embodiments, the chromite has a particle size of 45-300 μm and a chromium oxide content of 25 wt%-40 wt%; the alumina has a particle size of ≤75 μm and an alumina content of ≥96 wt%; the zirconium oxide has a particle size of ≤75 μm, a zirconium oxide content of ≥90 wt%, and a yttrium oxide content of ≥7 wt%; and the carbide has a particle size of ≤300 μm and a carbide content of ≥90 wt%.

[0050] By adopting the above technical solution, when the particle size and chromium oxide content of chromite, the particle size and aluminum oxide content of alumina, the particle size of zirconium oxide, the content of zirconium oxide and yttrium oxide, and the particle size and carbide content of carbides meet the above ranges, the friction coefficient of the iron-based powder metallurgy brake shoe friction body under different working conditions (i.e., different braking speeds, braking pressures, and axle loads) can be further improved, the heat resistance of the high-temperature braking of the iron-based powder metallurgy brake shoe friction body can be enhanced, the wear of the iron-based powder metallurgy brake shoe friction body can be indirectly reduced, and the stability of the friction coefficient can be guaranteed.

[0051] In some embodiments, the copper powder is electrolytic copper powder.

[0052] In some embodiments, the nickel powder is atomized nickel powder.

[0053] In some embodiments, the graphite is artificial graphite.

[0054] In some embodiments, the sulfide is selected from at least one of antimony sulfide, molybdenum disulfide, copper sulfide, tin sulfide, zinc sulfide, and manganese sulfide.

[0055] In some embodiments, the carbide is selected from at least one of silicon carbide, boron carbide, tungsten carbide, and titanium carbide.

[0056] In some embodiments, the compressive strength of the iron-based powder metallurgy brake shoe friction body is ≥130MPa, the interlaminar shear strength of the iron-based powder metallurgy brake shoe friction body is ≥30MPa, and the impact toughness of the iron-based powder metallurgy brake shoe friction body is ≥5 KJ / m².

[0057] Secondly, embodiments of the present invention provide a method for preparing iron-based powder metallurgy brake shoes, comprising the following steps: Prepare each component according to the composition of the iron-based powder metallurgy brake shoe friction body described above. The components of the iron-based powder metallurgy brake shoe friction body, excluding graphite, are premixed with a liquid hydrocarbon medium, and then graphite is added for secondary mixing to obtain a mixture. The tile back is placed at the bottom of the mold cavity, and the mixture is added into the mold containing the tile back and pressed to obtain a pressed blank with a tile back. The back-pressed blank with the tile is sintered under pressure in a protective gas atmosphere, and then cooled to obtain a sintered tile. The sintered tiles are then subjected to repressing to obtain iron-based powder metallurgy brake shoes.

[0058] The above technical solution involves premixing the components of the iron-based powder metallurgy brake shoe friction body, excluding graphite, with a liquid hydrocarbon medium, followed by secondary mixing with graphite to obtain a mixture. This mixing method prevents dust generation, improves mixing efficiency, and ensures more uniform distribution of components. The mixture is then pressed into a mold containing the back of the brake shoe to obtain a backed blank. This backed blank is then pressure-sintered under a protective gas atmosphere to obtain a sintered brake shoe. Pressure sintering prevents sidewall cracks caused by free expansion of the blank. Re-pressing the sintered brake shoe further enhances its density. This preparation method improves the compressive strength, shear strength, and heat resistance of the iron-based powder metallurgy brake shoe friction body. It also enhances the heat resistance and friction stability of the friction body, further reduces wear, and extends its service life.

[0059] Using the above technical solution, it is possible to prepare such as Figure 1 The image shows an iron-based powder metallurgy brake shoe comprising the aforementioned iron-based powder metallurgy brake shoe friction body 1 and the back of the shoe 2.

[0060] In some embodiments, the amount of the liquid hydrocarbon medium is 0.3-0.8 wt% of the total weight of the friction body.

[0061] In some embodiments, the liquid hydrocarbon medium is aviation kerosene.

[0062] By adopting the above technical solution, when the amount and type of liquid hydrocarbon medium meet the above limitations, raw material dust can be effectively avoided.

[0063] In some embodiments, the protective gas is an ammonia decomposition gas.

[0064] In some embodiments, the premixing process takes 60 minutes or more, and the secondary mixing process takes 30 minutes or more.

[0065] In some embodiments, the pressing pressure is 300-600 MPa.

[0066] In this invention, there is no special limitation on the pressing temperature; pressing can be carried out at room temperature. For example, the pressing temperature can be 0-30℃.

[0067] In some embodiments, the pressure sintering temperature is 900-1100℃, the sintering time is 2-6h, and the sintering pressure is 4.5-7.5MPa.

[0068] By adopting the above technical solution, when the conditions of premixing treatment, secondary mixing treatment, pressing pressure, pressure sintering temperature, pressure sintering time, and pressure sintering meet the above ranges, it is beneficial to improve the compressive strength, shear strength, and heat resistance of the iron-based powder metallurgy brake shoe friction body; at the same time, it improves the heat resistance and friction stability of the iron-based powder metallurgy brake shoe friction body, and further reduces the wear of the iron-based powder metallurgy brake shoe friction body, thus extending its service life.

[0069] like Figure 2 As shown, in some embodiments, the pressure sintering adopts the limiting pressure sintering method, in which the tile back pressure blank is attached to the outer wall of the graphite shuttle in a step-to-side manner, and at least four limiting blocks with the same height as the width of the tile back are placed around it. Then, a graphite cover plate is pressed on it to apply pressure, and it is placed in a bell-type pressure sintering furnace to sinter in an atmosphere of ammonia decomposition gas.

[0070] In some embodiments, the pressure of the compound pressure is 3-6 t / cm. 3 ​​​​。

[0071] By adopting the above technical solution, when the pressure of the repeated pressing meets the above range, it can better correct the tread deformation during sintering, achieve the required tread curvature, increase the density of the iron-based powder metallurgy brake shoe friction body, and reduce the looseness of the structure.

[0072] Thirdly, embodiments of the present invention provide an iron-based powder metallurgy brake shoe, which includes the above-mentioned iron-based powder metallurgy brake shoe friction body and backing, and / or is prepared by the above-mentioned preparation method.

[0073] The beneficial effects of the iron-based powder metallurgy brake shoe provided by the present invention are the same as those of the iron-based powder metallurgy brake shoe friction body described in the above technical solution, and will not be repeated here.

[0074] In this invention, there is no particular limitation on the material of the roof tile backing; conventional roof tile backing materials in the art can be used. Preferably, the material of the roof tile backing can be carbon structural steel or heat-resistant steel. For example, the carbon structural steel can be Q235 or Q355 carbon structural steel; the heat-resistant steel can be 35CrMo or 42CrMo heat-resistant steel.

[0075] In some embodiments, the thickness of the friction body of the iron-based powder metallurgy brake shoe is 30mm-60mm.

[0076] Fourthly, embodiments of the present invention provide the above-mentioned iron-based powder metallurgy brake shoe friction body, or the application of the above-mentioned iron-based powder metallurgy brake shoe in high-speed braking.

[0077] The beneficial effects of the iron-based powder metallurgy brake shoe friction body provided by the present invention, or the application of iron-based powder metallurgy brake shoes in high-speed braking, are the same as the beneficial effects of the iron-based powder metallurgy brake shoe friction body described in the above technical solution, and will not be repeated here.

[0078] To better illustrate the technical solution of the present invention, the following specific embodiments are also provided.

[0079] The raw materials used in the following examples and comparative examples are all commercially available and only need to meet the following performance parameters: The reduced iron powder has a particle size ≤75μm and an oxygen content ≤1.2wt%. The steel fibers have a diameter ≤0.1mm and a length ≤1mm; The electrolytic copper powder has a particle size ≤75μm and an oxygen content ≤0.2wt%. The atomized nickel powder has a particle size ≤75μm and a total nickel-cobalt content ≥99wt%. The molybdenum powder has a particle size ≤30μm and a molybdenum content ≥99wt%. The tin powder has a particle size ≤75μm and a tin content ≥99wt%. The graphite has a particle size of 150-500 μm and a carbon content of ≥99 wt%. The sulfide has a particle size ≤300μm and a purity ≥98wt%; The chromite has a particle size of 45-300 μm and a chromium trioxide content of 25 wt%-40 wt%. The alumina has a particle size ≤75μm and an aluminum oxide content ≥96wt%. The zirconium oxide has a particle size ≤75μm, a zirconium oxide content ≥90wt%, and a yttrium oxide content ≥7wt%. The particle size of the carbide is ≤300μm and the carbide content is ≥90wt%.

[0080] Example 1 A type of iron-based powder metallurgy brake shoe, comprising an iron-based powder metallurgy brake shoe friction body (thickness of 30mm) and a backing (carbon structural steel Q235A). The specific composition of the above-mentioned iron-based powder metallurgy brake shoe friction body is shown in Table 1; The preparation process of the above-mentioned iron-based powder metallurgy brake shoe is as follows: (1) Ingredients: Weigh each component using an electronic scale; (2) Mixing: First, premix the components other than artificial graphite with aviation kerosene in a mixing cylinder for 80 minutes, then add artificial graphite and mix for another 40 minutes. Discharge the mixture from the outlet of the mixing cylinder and store it in a storage cylinder; wherein, the amount of the liquid hydrocarbon medium is 0.8 wt% of the total weight of the friction body; (3) Cold pressing: First, place the tile back into the bottom of the mold cavity, and then put the mixture into the mold containing the tile back. Press it at room temperature on a 500~1200T press with a pressing pressure of 450MPa. After pressing, it becomes a blank with tile back. (4) Limiting and pressurizing sintering: Two blanks with tile backs are attached to the two outer walls of the same graphite shuttle with their treads facing each other. Four cylindrical limiting blocks with the same height as the width of the tile back are placed around the blanks. Then, a graphite cover plate is placed on top of the blanks to apply pressure. The blanks are placed in a bell furnace and pressurized and sintered in an atmosphere of ammonia decomposition gas. The pressurized sintering temperature is 1000℃ and the temperature is held for 4 hours. The sintering pressure during the holding period is 6 MPa. After cooling to room temperature, the blanks are removed from the furnace to obtain sintered tiles. (5) Re-pressing: The above sintered tiles are placed on a shaping fixture for re-pressing to obtain iron-based powder metallurgy brake shoes. The re-pressing pressure is 3t / cm. 2 .

[0081] Table 1 Example 2 A type of iron-based powder metallurgy brake shoe, comprising an iron-based powder metallurgy brake shoe friction body (thickness of 30mm) and a backing (carbon structural steel Q235A). The specific composition of the above-mentioned iron-based powder metallurgy brake shoe friction body is shown in Table 1; The preparation process of the above-mentioned iron-based powder metallurgy brake shoe is as follows: (1) Ingredients: Weigh each component using an electronic scale; (2) Mixing: First, put the components other than artificial graphite and aviation kerosene into the mixing cylinder for premixing for 60 minutes, then add artificial graphite and mix for a second time for 30 minutes. Discharge the mixture from the outlet of the mixing cylinder and store it in the storage cylinder; wherein, the amount of the liquid hydrocarbon medium is 0.7 wt% of the total weight of the friction body; (3) Cold pressing: First, place the tile back into the bottom of the mold cavity, and then put the mixture into the mold containing the tile back. Press it at room temperature on a 500~1200T press with a pressing pressure of 300MPa. After pressing, it becomes a blank with tile back. (4) Limiting and pressurizing sintering: Two blanks with tile backs are attached to the two outer walls of the same graphite shuttle with their treads facing each other. Four cylindrical limiting blocks with the same height as the width of the tile back are placed around the blanks. Then, a graphite cover plate is placed on top of the blanks to apply pressure. The blanks are placed in a bell furnace and pressurized and sintered in an atmosphere of ammonia decomposition gas. The pressurized sintering temperature is 900℃ and the temperature is held for 2 hours. The sintering pressure during the holding time is 4.5 MPa. After cooling to room temperature, the blanks are removed from the furnace to obtain sintered tiles. (5) Re-pressing: The sintered tiles are placed on a forming fixture for re-pressing to obtain iron-based powder metallurgy brake shoes. The re-pressing pressure is 4.5 t / cm. 3 .

[0082] Example 3 A type of iron-based powder metallurgy brake shoe, comprising an iron-based powder metallurgy brake shoe friction body (thickness of 30mm) and a backing (carbon structural steel Q235A). The specific composition of the above-mentioned iron-based powder metallurgy brake shoe friction body is shown in Table 1; The preparation process of the above-mentioned iron-based powder metallurgy brake shoe is as follows: (1) Ingredients: Weigh each component using an electronic scale; (2) Mixing: First, premix the components other than artificial graphite with aviation kerosene in a mixing cylinder for 90 minutes, then add artificial graphite and mix for another 50 minutes. Discharge the mixture from the outlet of the mixing cylinder and store it in a storage cylinder; wherein, the amount of the liquid hydrocarbon medium is 0.5 wt% of the total weight of the friction body; (3) Cold pressing: First, place the tile back into the bottom of the mold cavity, and then put the mixture into the mold containing the tile back. Press it at room temperature on a 500~1200T press with a pressing pressure of 400MPa. After pressing, it becomes a blank with tile back. (4) Limiting and pressurizing sintering: Two blanks with tile backs are attached to the two outer walls of the same graphite shuttle with their treads facing each other. Four cylindrical limiting blocks with the same height as the width of the tile back are placed around the blanks. Then, a graphite cover plate is placed on top of the blanks to apply pressure. The blanks are placed in a bell furnace and pressurized and sintered in an atmosphere of ammonia decomposition gas. The pressurized sintering temperature is 1100℃ and the holding time is 6h. The sintering pressure during the holding time is 7.5Mpa. After cooling to room temperature, the blanks are removed from the furnace to obtain sintered tiles. (5) Re-pressing: The above sintered tiles are placed on a shaping fixture for re-pressing to obtain iron-based powder metallurgy brake shoes. The re-pressing pressure is 6t / cm. 3 .

[0083] Example 4 A type of iron-based powder metallurgy brake shoe, comprising an iron-based powder metallurgy brake shoe friction body (thickness of 30mm) and a backing (carbon structural steel Q235A). The specific composition of the above-mentioned iron-based powder metallurgy brake shoe friction body is shown in Table 1; The preparation process of the above-mentioned iron-based powder metallurgy brake shoe is as follows: (1) Ingredients: Weigh each component using an electronic scale; (2) Mixing: First, premix the components other than artificial graphite with aviation kerosene in a mixing cylinder for 80 minutes, then add artificial graphite and mix for another 40 minutes. Discharge the mixture from the outlet of the mixing cylinder and store it in a storage cylinder; wherein, the amount of the liquid hydrocarbon medium is 0.8 wt% of the total weight of the friction body; (3) Cold pressing: First, place the tile back into the bottom of the mold cavity, and then put the mixture into the mold containing the tile back. Press it at room temperature on a 500~1200T press with a pressing pressure of 500MPa. After pressing, it becomes a blank with tile back. (4) Limiting and pressurizing sintering: Two blanks with tile backs are attached to the two outer walls of the same graphite shuttle with their treads facing each other. Four cylindrical limiting blocks with the same height as the width of the tile back are placed around the blanks. Then, a graphite cover plate is placed on top of the blanks to apply pressure. The blanks are placed in a bell furnace and pressurized and sintered in an atmosphere of ammonia decomposition gas. The pressurized sintering temperature is 950℃ and the holding time is 5h. The sintering pressure during the holding time is 7MPa. After cooling to room temperature, the blanks are removed from the furnace to obtain sintered tiles. (5) Re-pressing: The above sintered tiles are placed on a shaping fixture for re-pressing to obtain iron-based powder metallurgy brake shoes. The re-pressing pressure is 4t / cm. 3 .

[0084] Example 5 A type of iron-based powder metallurgy brake shoe, comprising an iron-based powder metallurgy brake shoe friction body (thickness of 30mm) and a backing (carbon structural steel Q235A). The specific composition of the above-mentioned iron-based powder metallurgy brake shoe friction body is shown in Table 1; The preparation process of the above-mentioned iron-based powder metallurgy brake shoe is as follows: (1) Ingredients: Weigh each component using an electronic scale; (2) Mixing: First, premix the components other than artificial graphite with aviation kerosene in a mixing cylinder for 80 minutes, then add artificial graphite and mix for another 40 minutes. Discharge the mixture from the outlet of the mixing cylinder and store it in a storage cylinder; wherein, the amount of the liquid hydrocarbon medium is 0.8 wt% of the total weight of the friction body; (3) Cold pressing: First, place the tile back into the bottom of the mold cavity, and then put the mixture into the mold containing the tile back. Press it at room temperature on a 500~1200T press with a pressing pressure of 600MPa. After pressing, it becomes a blank with tile back. (4) Limiting and pressurizing sintering: Two blanks with tile backs are attached to the two outer walls of the same graphite shuttle with their treads facing each other. Four cylindrical limiting blocks with the same height as the width of the tile back are placed around the blanks. Then, a graphite cover plate is placed on top of the blanks to apply pressure. The blanks are placed in a bell furnace and pressurized and sintered in an atmosphere of ammonia decomposition gas. The pressurized sintering temperature is 1050℃ and the temperature is held for 3 hours. The sintering pressure during the holding time is 5 MPa. After cooling to room temperature, the blanks are removed from the furnace to obtain sintered tiles. (5) Re-pressing: The above sintered tiles are placed on a forming fixture for re-pressing to obtain iron-based powder metallurgy brake shoes. The re-pressing pressure is 5t / cm. 3 .

[0085] Comparative Example 1 A type of iron-based powder metallurgy brake shoe, comprising an iron-based powder metallurgy brake shoe friction body (thickness of 30mm) and a backing (carbon structural steel Q235A). The specific composition of the iron-based powder metallurgy brake shoe friction body in Comparative Example 1 is different from that in Example 1, the nickel powder in Example 1 is replaced with an equal mass of molybdenum powder, that is, the content of nickel powder is 0 wt% and the content of molybdenum powder is 4 wt%; the other components and the preparation process of the iron-based powder metallurgy brake shoe remain unchanged.

[0086] Comparative Example 2 A type of iron-based powder metallurgy brake shoe, comprising an iron-based powder metallurgy brake shoe friction body (thickness of 30mm) and a backing (carbon structural steel Q235A). The specific composition of the iron-based powder metallurgy brake shoe friction body in Comparative Example 2 is different from that in Example 1, the molybdenum powder in Example 1 is replaced with an equal mass of tin powder, that is, the content of molybdenum powder is 0 wt% and the content of tin powder is 4 wt%; the other components and the preparation process of the iron-based powder metallurgy brake shoe remain unchanged.

[0087] Comparative Example 3 A type of iron-based powder metallurgy brake shoe, comprising an iron-based powder metallurgy brake shoe friction body (thickness of 30mm) and a backing (carbon structural steel Q235A). The specific composition of the iron-based powder metallurgy brake shoe friction body in Comparative Example 3 is different from that in Example 1, the tin powder in Example 1 is replaced with an equal mass of nickel powder, that is, the content of tin powder is 0 wt% and the content of nickel powder is 4 wt%; the other components and the preparation process of the iron-based powder metallurgy brake shoe remain unchanged.

[0088] Comparative Example 4 A type of iron-based powder metallurgy brake shoe, comprising an iron-based powder metallurgy brake shoe friction body (thickness of 30mm) and a backing (carbon structural steel Q235A). The specific composition of the iron-based powder metallurgy brake shoe friction body in Comparative Example 4 is different from that in Example 1, the reduced iron powder in Example 1 is replaced with an equal mass of electrolytic copper powder, that is, the content of reduced iron powder is 0 wt% and the content of electrolytic copper powder is 41 wt%; the other components and the preparation process of the iron-based powder metallurgy brake shoe remain unchanged.

[0089] Comparative Example 5 A type of iron-based powder metallurgy brake shoe, comprising an iron-based powder metallurgy brake shoe friction body (thickness of 30mm) and a backing (carbon structural steel Q235A). The specific composition of the iron-based powder metallurgy brake shoe friction body in Comparative Example 5 is different from that in Example 1, the electrolytic copper powder in Example 1 is replaced with an equal mass of reduced iron powder, that is, the content of electrolytic copper powder is 0 wt% and the content of reduced iron powder is 41 wt%; the other components and the preparation process of the iron-based powder metallurgy brake shoe remain unchanged.

[0090] Comparative Example 6 A type of iron-based powder metallurgy brake shoe, comprising an iron-based powder metallurgy brake shoe friction body (thickness of 30mm) and a backing (carbon structural steel Q235A). The specific composition of the iron-based powder metallurgy brake shoe friction body in Comparative Example 6 is different from that in Example 1, the steel fibers in Example 1 are replaced with an equal mass of reduced iron powder; the other components and the preparation process of the iron-based powder metallurgy brake shoe remain unchanged.

[0091] Test Example 1 The iron-based powder metallurgy brake shoes of Examples 1-5 and Comparative Examples 1-6 were tested sequentially. The density of the friction element on the iron-based powder metallurgy brake shoes was tested according to GB / T 10421 standard; the compressive strength was tested according to GB / T 10424-2002 standard; the interlaminar shear strength was tested according to Appendix D of TJ / CL307-2019 standard; and the impact toughness was tested according to GB / T1043.1 standard. Unnotched specimens were used, with the thickness direction aligned with the impact load direction. Hardness was tested according to GB / T231.1 standard. The test results are shown in Tables 2 and 3.

[0092] Table 2 Table 3 As can be seen from the results in Tables 2 and 3, the density, compressive strength, interlaminar shear strength, impact toughness, and hardness of the iron-based powder metallurgy brake shoes in Examples 1-5 not only meet the technical parameter requirements, but also show superior compressive strength, interlaminar shear strength, and impact toughness compared to those of Comparative Examples 1-6. Comparative Examples 1-6, while meeting the technical requirements for density and hardness, have lower compressive strength, interlaminar shear strength, and impact toughness, which are not up to standard. This is mainly because the friction bodies of Comparative Examples 1-3 lack the strengthening and performance-improving effects of nickel, molybdenum, and tin on the iron matrix, respectively. Comparative Example 4 only uses copper powder and steel fiber as the matrix, lacking the dispersion strengthening effect of iron powder on the matrix. Comparative Example 5 lacks highly flexible electrolytic copper powder to supplement the toughness and strengthening of the iron matrix. Comparative Example 6 lacks steel fibers with randomized distribution characteristics, thus failing to reinforce the matrix.

[0093] Test Example 2 The dynamic friction coefficient (dry braking), static friction coefficient, and wear amount of the iron-based powder metallurgy brake shoes of Examples 1-5 and Comparative Examples 1-6 were tested in sequence. The wheel load was 12.5t, the test speed was 50-160 km / h, and the test pressure was 10-30kN. The specific test speed, pressure and test results are shown in Tables 4 and 5.

[0094] Table 4 There is no standard requirement for the coefficient of dynamic friction at a pressure of 30kN.

[0095] Table 5 The results in Tables 4 and 5 show that the dynamic friction coefficient (dry braking), static friction coefficient, and wear of the iron-based powder metallurgy brake shoes in Examples 1-5 all meet the technical requirements. Furthermore, the dynamic friction coefficient (dry braking), static friction coefficient, and wear of the iron-based powder metallurgy brake shoes in Examples 1-6 are all superior to those in Comparative Examples 1-6. In contrast, the dynamic friction coefficient (dry braking) of the iron-based powder metallurgy brake shoes in Comparative Examples 1-6 is mostly below the required lower limit, and their static friction coefficients under braking pressures of 10kN and 20kN also fail to meet the technical requirements, with wear exceeding the standard by 0.35 cm. 3 / MJ. Therefore, the iron-based powder metallurgy brake shoe of the present invention comprises a friction body composed of specific components, maintaining a high coefficient of dynamic friction under different braking speeds (50-160 km / h) and pressures (10-30 kN), while exhibiting low wear. This demonstrates that the iron-based powder metallurgy brake shoe of the present invention can prevent the degradation of brake shoe friction performance due to high frictional temperatures during high-speed braking, maintaining the stability of the friction coefficient; and extending the service life of the iron-based powder metallurgy brake shoe under high-temperature braking conditions.

[0096] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A type of iron-based powder metallurgy brake shoe friction element, characterized in that, The iron-based powder metallurgy brake shoe friction body comprises 60-75% matrix components, 3-9% reinforcing components, 10-14% lubricating components, and 12-18% friction components by mass percentage. The matrix component comprises iron powder, steel fiber and copper powder; the reinforcing component comprises nickel powder, molybdenum powder and tin powder; the lubricating component comprises graphite and sulfides; and the friction component comprises chromite, alumina, zirconium oxide and carbides.

2. The iron-based powder metallurgy brake shoe friction element according to claim 1, characterized in that, Based on the mass percentage of the iron-based powder metallurgy brake shoe friction material, the content of iron powder is 20-30%, the content of steel fiber is 20-30%, the content of copper powder is 10-20%; the content of nickel powder is 1-3%, the content of molybdenum powder is 1-3%, the content of tin powder is 1-3%; the content of graphite is 8-10%, the content of sulfides is 2-4%; the content of chromite is 9-12%, the content of alumina is 1-2%, the content of zirconium oxide is 1-2%, and the content of carbides is 1-2%.

3. The iron-based powder metallurgy brake shoe friction element according to claim 1 or 2, characterized in that, The iron powder has a particle size ≤75μm and an oxygen content ≤1.2wt%; the steel fiber has a diameter ≤0.1mm and a length ≤1mm; the copper powder has a particle size ≤75μm and an oxygen content ≤0.2wt%; the nickel powder has a particle size ≤75μm and a total nickel-cobalt content ≥99wt%; the molybdenum powder has a particle size ≤30μm and a molybdenum content ≥99wt%; and the tin powder has a particle size ≤75μm and a tin content ≥99wt%.

4. The iron-based powder metallurgy brake shoe friction element according to claim 1 or 2, characterized in that, The graphite has a particle size of 150-500 μm and a carbon content of ≥99 wt%; the sulfide has a particle size of ≤300 μm and a purity of ≥98 wt%; and / or, The chromite has a particle size of 45-300 μm and a chromium oxide content of 25 wt%-40 wt%; the alumina has a particle size of ≤75 μm and an alumina content of ≥96 wt%; the zirconium oxide has a particle size of ≤75 μm, a zirconium oxide content of ≥90 wt%, and a yttrium oxide content of ≥7 wt%; the carbide has a particle size of ≤300 μm and a carbide content of ≥90 wt%.

5. The iron-based powder metallurgy brake shoe friction element according to claim 1 or 2, characterized in that, The sulfide is selected from at least one of antimony sulfide, molybdenum disulfide, copper sulfide, tin sulfide, zinc sulfide, and manganese sulfide; and / or, The carbide is selected from at least one of silicon carbide, boron carbide, tungsten carbide, and titanium carbide.

6. A method for preparing iron-based powder metallurgy brake shoes, characterized in that, Includes the following steps: Prepare each component according to the composition of the iron-based powder metallurgy brake shoe friction body according to any one of claims 1-5; The components of the iron-based powder metallurgy brake shoe friction body, excluding graphite, are premixed with a liquid hydrocarbon medium, and then graphite is added for secondary mixing to obtain a mixture. The tile back is placed at the bottom of the mold cavity, and the mixture is added into the mold containing the tile back and pressed to obtain a pressed blank with a tile back. The back-pressed blank with the tile is sintered under pressure in a protective gas atmosphere, and then cooled to obtain a sintered tile. The sintered tiles are then subjected to repressing to obtain iron-based powder metallurgy brake shoes.

7. The preparation method according to claim 6, characterized in that, The amount of the liquid hydrocarbon medium used is 0.3-0.8 wt% of the total weight of the friction body; and / or, The liquid hydrocarbon medium is aviation kerosene; and / or, The protective gas is an ammonia decomposition gas.

8. The preparation method according to claim 6 or 7, characterized in that, The premixing treatment time is greater than or equal to 60 minutes, and the secondary mixing treatment duration is greater than or equal to 30 minutes. The pressing pressure is 300-600 MPa; and / or, The pressure sintering temperature is 900-1100℃, the pressure sintering time is 2-6 hours, and the pressure sintering pressure is 4.5-7.5 MPa; and / or, The pressure of the overpressure is 3-6 t / cm. 2 ​​.

9. A type of iron-based powder metallurgy brake shoe, characterized in that, It comprises the iron-based powder metallurgy brake shoe friction body and backing as described in any one of claims 1-5, and / or is prepared by the preparation method described in any one of claims 6-8.

10. The iron-based powder metallurgy brake shoe friction body according to any one of claims 1-5, or the application of the iron-based powder metallurgy brake shoe according to claim 9 in high-speed braking.

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