Powder metallurgy brake shoe for locomotive and preparation method

Abstract

The invention discloses a powder metallurgy brake shoe for a locomotive and a preparation method, and relates to the technical field of metallurgy brake shoes, the powder metallurgy brake shoe comprises the following raw materials by mass percentage: 50%-70% of a matrix component, 10%-18% of a reinforcing component, 10%-16% of a lubricating component and 10%-16% of a friction component; the matrix component comprises electrolytic copper powder; the reinforcing components comprise reduced iron powder, superfine iron powder, atomized nickel powder, molybdenum powder and zinc powder; the lubricating component comprises artificial graphite and sulfide. According to the invention, the performance reduction of the brake shoe and the decline of a matrix at high temperature are effectively inhibited, the stability of a friction coefficient is kept, the abrasion is reduced, and the service life is prolonged.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of metallurgical brake shoes, in particular to a powder metallurgy brake shoe for locomotive and a preparation method thereof. BACKGROUND

[0002] The conventional integral powder metallurgy brake shoe can only meet the braking at a speed of 120 km / h, and when the speed is increased to 140 km / h to 160 km / h or above, a large amount of sparks will appear during braking, which will cause the friction coefficient to decay rapidly, and further cause the brake shoe to wear too much, the braking force to be insufficient, the heat resistance limit to be insufficient, and the service life of the brake shoe to be shortened. SUMMARY

[0003] The present application aims to provide a powder metallurgy brake shoe for locomotive and a preparation method thereof, which overcomes the defects that a large amount of sparks appear during braking of the brake shoe, causing the friction coefficient to decay rapidly, and further causing the brake shoe to wear too much, the braking force to be insufficient, the heat resistance limit to be insufficient, and the service life to be shortened.

[0004] The present application provides a powder metallurgy brake shoe for locomotive, which is composed of raw materials in a mass percentage of 50% to 70% of a base component, 10% to 18% of a reinforcing component, 10% to 16% of a lubricating component, and 10% to 16% of a friction component; wherein the base component comprises electrolytic copper powder; the reinforcing component comprises reduced iron powder, ultra-fine iron powder, atomized nickel powder, molybdenum powder, and zinc powder; and the lubricating component comprises artificial graphite and sulfide.

[0005] Compared with the prior art, the present application adds reduced iron powder, ultra-fine iron powder, atomized nickel powder, molybdenum powder, and zinc powder to the reinforcing component, which are mixed with electrolytic copper powder to form copper-based alloy, and the copper-based alloy can increase the strength of the base component, improve the high-temperature strength, toughness, wet abrasion resistance, and anti-decay performance of the prepared metallurgical brake shoe friction body, thereby further stabilizing the friction performance and improving the service life of the metallurgical brake shoe in high-cold and humid environments. On this basis, the present application adds sulfide and graphite to the lubricating component, and increases the proportion of the lubricating component, because sulfide and graphite have excellent lubricating performance and can reduce the friction coefficient during braking; therefore, the high-proportion lubricating component combined with the copper-based alloy can prevent a large amount of sparks from appearing during braking of the locomotive at a high speed of 140 km / h to 160 km / h, thereby inhibiting the decay of high-temperature performance and maintaining the stability of the friction coefficient.

[0006] In addition, the application also uses electrolytic copper powder as the base component, because the electrolytic copper powder has high thermal conductivity and high cold resistance, so when the electrolytic copper powder is used as the base component, it is not only beneficial to reduce the noise during braking friction, but also beneficial to reduce the heat generated during braking friction, thereby preventing the strength of the base and the decline of the brake shoe performance caused by high temperature braking friction, and more beneficial to maintain the stability of the wet friction coefficient.

[0007] In summary, the application increases the proportion of the lubricating component, and forms a multi-alloyed copper base by using the reinforcing component and the base component, solves the problem of a large amount of sparks generated during high-speed braking of 140-160 km / h, effectively suppresses the decline of the performance of the metallurgical brake shoe and the decline of the base under high temperature, maintains the stability of the friction coefficient of the metallurgical brake shoe, reduces the wear of the metallurgical brake shoe, prolongs the service life of the metallurgical brake shoe, and meets the required dynamic friction and static friction braking performance standards to meet the braking requirements.

[0008] Further, in the reinforcing component, the mass ratio of the reduced iron powder, the ultra-fine iron powder, the atomized nickel powder, the molybdenum powder and the zinc powder is (6-7):(1-3):(1-3):(1-3):(1-2).

[0009] Compared with the prior art, the mass ratio of the reduced iron powder, the ultra-fine iron powder, the atomized nickel powder, the molybdenum powder and the zinc powder in the application is (6-7):(1-3):(1-3):(1-3):(1-2), because a high proportion of iron-based powder (including reduced iron powder and ultra-fine iron powder) can improve the basic strength and wear resistance of the metallurgical brake shoe, and after mixing with the atomized nickel powder, the molybdenum powder and the zinc powder, the high-temperature braking performance of the metallurgical brake shoe can be further optimized to achieve high strength and wear resistance.

[0010] Further, in the lubricating component, the mass ratio of the artificial graphite and the sulfide is (8-13):(2-3).

[0011] Compared with the prior art, when the mass ratio of the artificial graphite and the sulfide is (8-13):(2-3), a high proportion of artificial graphite as the main lubricating phase provides stable basic lubrication and friction coefficient regulation capability; a low proportion of sulfide as an auxiliary lubricating phase strengthens the high-temperature braking lubrication effect and suppresses the friction fluctuation under extreme working conditions, thereby reducing the friction coefficient during braking and reducing the wear during high-temperature braking.

[0012] Further, the sulfide includes at least one of antimony sulfide, molybdenum disulfide, copper sulfide, tin sulfide, zinc sulfide and manganese sulfide.

[0013] Compared with the prior art, the sulfide is used alone or in combination, so that the friction coefficient during the metallurgical brake shoe braking can be further reduced.

[0014] Further, the friction component comprises the chromite, the alumina and the carbide in a mass ratio of (8-12):(1-2):(1-2).

[0015] Compared with the prior art, the addition of the chromite, the alumina and the carbide makes the metallurgical brake shoe have higher heat resistance and friction performance during the braking friction.

[0016] Further, the carbide comprises at least one of silicon carbide, boron carbide, tungsten carbide and titanium carbide.

[0017] Compared with the prior art, the carbide is used alone or in combination, so that the heat resistance and the friction performance of the metallurgical brake shoe during the braking friction can be effectively improved.

[0018] The second aspect of the present application provides a preparation method of a powder metallurgical brake shoe for locomotive, which is applied to the powder metallurgical brake shoe for locomotive and comprises the following steps:

[0019] The raw materials are weighed according to the above-mentioned powder metallurgical brake shoe for locomotive;

[0020] The raw materials except the artificial graphite are premixed with the aviation kerosene, and then the artificial graphite is added for mixing to obtain a mixture; wherein the mass ratio of the aviation kerosene in the mixture is 0.5%-1.2%.

[0021] The shoe back and the mixture are sequentially placed in a mold cavity for pressing to obtain a shoe back pressing blank;

[0022] The shoe back pressing blank is subjected to limited sintering and cooling in an atmosphere of ammonia decomposition gas to obtain a sintered shoe;

[0023] The sintered shoe is subjected to re-pressing to obtain a finished shoe.

[0024] Compared with the prior art, when the reduced iron powder, the metal powder such as the ultra-fine iron powder, the carbide and the sulfide are premixed with the aviation kerosene, the aviation kerosene acts as a dispersing agent to uniformly disperse the metal powder, the carbide and the sulfide, and the viscosity of the aviation kerosene can temporarily adsorb the metal powder, the carbide and the sulfide to prevent the powder from entering the air during subsequent mixing; finally, the artificial graphite is added because the graphite is light and easy to float, and if it is added too early, it will be unevenly distributed due to the large difference in density with the metal powder. The limited pressure sintering tooling can avoid cracks caused by the free expansion of the side wall during sintering; and the re-pressing shaping process can improve the compactness of the metallurgical brake shoe structure.

[0025] Further, the stirring speed during the premixing is 15 rpm to 30 rpm, and the stirring time is 70 min to 90 min; and / or,

[0026] The stirring speed during the mixing is 15 rpm to 30 rpm, and the stirring time is 30 min to 50 min.

[0027] Compared with the prior art, under the stirring speed and the stirring time described above, the metallurgical brake block prepared finally has good uniformity and uniform density, and the strength and high-temperature friction braking performance of the metallurgical brake block are further improved.

[0028] Further, the placing the brake back and the mixed material into the mold cavity in sequence comprises:

[0029] The brake back is first placed into the bottom of the mold cavity and contacted with the lower punch, and then the mixed material is placed into the mold cavity.

[0030] Compared with the prior art, the brake back is directly contacted with the lower punch, and accurate positioning can be achieved through the profile of the mold cavity, so that the brake back does not deviate during the pressing process. When the mixed material is subsequently added and pressed, the mixed material will tightly wrap the surface of the brake back under the action of pressure to form a mechanical embedded interface. This positioning and filling method can avoid the phenomenon of insufficient bonding area caused by the displacement of the brake back when the mixed material is filled, and thus is beneficial to the forming of the metallurgical brake block during subsequent sintering.

[0031] Further, the pressing is carried out at room temperature, and the pressing pressure acting on the friction body is 200 MPa to 400 MPa. It should be understood that "room temperature" here refers to the normal temperature in different seasons of spring, summer, autumn and winter.

[0032] Compared with the prior art, under the pressing temperature and the pressing pressure described above, the combination of the mixed material and the brake back is more favorable, and thus the forming of the metallurgical brake block during subsequent sintering is more favorable.

[0033] Further, the temperature during the limiting sintering is 900°C to 1100°C, the holding time during the limiting sintering is 2 h to 6 h, and the pressure during the limiting sintering is 4.5 MPa to 7.5 MPa.

[0034] Compared with the prior art, when the temperature during the limiting sintering is 900°C to 1100°C, the holding time during the limiting sintering is 2 h to 6 h, and the pressure during the limiting sintering is 4.5 MPa to 7.5 MPa, the diffusion welding of the particles of each component can be promoted, and thus an alloyed copper base is formed, and the hardness and wear resistance of the metallurgical brake block are enhanced.

[0035] Further, the cooling is to 80°C or lower.

[0036] Compared with the prior art, when the temperature is reduced to below 80 DEG C, the sintered shoe can be rapidly cooled to form, and surface oxidation during discharge is prevented.

[0037] Further, the re-pressing is performed at 10-20 MPa.

[0038] Compared with the prior art, when the re-pressing pressure is 10-20 MPa, the forming of the metallurgical shoe to the required shape is further promoted, and the compactness of the metallurgical shoe is improved. DETAILED DESCRIPTION

[0039] In order to make the technical problems, technical solutions and beneficial effects of the present application clearer, the present application will be further described in detail below in combination with specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and not used to limit the present application.

[0040] In the prior art, a large amount of sparks are generated during locomotive shoe braking, which leads to rapid decline of the friction coefficient, excessive wear of the shoe, insufficient braking force, insufficient heat resistance limit and shortened service life.

[0041] In order to overcome the above-mentioned defects, in a first aspect, the present application provides a powder metallurgical shoe for locomotive, which comprises, in terms of mass percentage of raw materials for the powder metallurgical shoe, 50-70% of a base component, 10-18% of a reinforcing component, 10-16% of a lubricating component and 10-16% of a friction component; wherein the base component comprises electrolytic copper powder; the reinforcing component comprises reduced iron powder, ultra-fine iron powder, atomized nickel powder, molybdenum powder and zinc powder; and the lubricating component comprises artificial graphite and sulfide.

[0042] For example, the electrolytic copper powder has a particle size of -200 mesh and an oxygen content of ≤0.2%; the reduced iron powder has a particle size of -200 mesh and an oxygen content of ≤1.2%; the ultra-fine iron powder has a particle size of 1-7 μm and an oxygen content of ≤1.2%; the atomized nickel powder has a particle size of -200 mesh and a total content of Ni+Co of ≥99%; the molybdenum powder has a particle size of -500 mesh and a Mo content of ≥99%; the zinc powder has a particle size of -200 mesh and a Zn content of ≥99%; the artificial graphite has a particle size of -30 mesh to +100 mesh and a C content of ≥99.9%; and the sulfide has a particle size of -325 mesh.

[0043] For example, the powder metallurgical shoe for locomotive comprises, in terms of mass percentage of raw materials for the powder metallurgical shoe, 50% of a base component, 18% of a reinforcing component, 16% of a lubricating component and 16% of a friction component; wherein the base component comprises electrolytic copper powder; the reinforcing component comprises reduced iron powder, ultra-fine iron powder, atomized nickel powder, molybdenum powder and zinc powder; and the lubricating component comprises artificial graphite and sulfide.

[0044] According to the technical scheme, the powder metallurgy brake shoe for locomotive is composed of 70% of a base component, 10% of a reinforcing component, 10% of a lubricating component and 10% of a friction component; the base component comprises electrolytic copper powder; the reinforcing component comprises reduced iron powder, ultrafine iron powder, atomized nickel powder, molybdenum powder and zinc powder; and the lubricating component comprises artificial graphite and sulfide.

[0045] According to the technical scheme, the powder metallurgy brake shoe for locomotive is composed of 60% of a base component, 15% of a reinforcing component, 12% of a lubricating component and 13% of a friction component; the base component comprises electrolytic copper powder; the reinforcing component comprises reduced iron powder, ultrafine iron powder, atomized nickel powder, molybdenum powder and zinc powder; and the lubricating component comprises artificial graphite and sulfide.

[0046] According to the technical scheme, the powder metallurgy brake shoe for locomotive is composed of 55% of a base component, 13% of a reinforcing component, 16% of a lubricating component and 16% of a friction component; the base component comprises electrolytic copper powder; the reinforcing component comprises reduced iron powder, ultrafine iron powder, atomized nickel powder, molybdenum powder and zinc powder; and the lubricating component comprises artificial graphite and sulfide.

[0047] According to the technical scheme, the powder metallurgy brake shoe for locomotive is composed of 55% of a base component, 13% of a reinforcing component, 16% of a lubricating component and 16% of a friction component; the base component comprises electrolytic copper powder; the reinforcing component comprises reduced iron powder, ultrafine iron powder, atomized nickel powder, molybdenum powder and zinc powder; and the lubricating component comprises artificial graphite and sulfide.

[0048] In some embodiments, the mass ratio of the reduced iron powder, the ultrafine iron powder, the atomized nickel powder, the molybdenum powder and the zinc powder in the reinforcing component is (6-7):(1-3):(1-3):(1-3):(1-2).

[0049] In some embodiments, the mass ratio of the reduced iron powder, the ultrafine iron powder, the atomized nickel powder, the molybdenum powder and the zinc powder in the reinforcing component is (6-7):(1-3):(1-3):(1-3):(1-2).

[0050] When the technical scheme is adopted, the high proportion of iron-based powder (including reduced iron powder and ultra-fine iron powder) in the reinforcing component can improve the basic strength and wear resistance of the metallurgical brake shoe, and after being mixed with atomized nickel powder, molybdenum powder and zinc powder, the high-temperature braking performance of the metallurgical brake shoe is further optimized, and the effects of high strength and wear resistance are achieved.

[0051] In some embodiments, the mass ratio of the artificial graphite and the sulfide in the lubricating component is (8-13):(2-3).

[0052] For example, the mass ratio of the artificial graphite and the sulfide in the lubricating component can be specifically selected as 8:2, 13:3, 9.5:2.5 or a range value composed of any point value, and is preferably (8-9.5):(2.5-3).

[0053] When the technical scheme is adopted, the high proportion of artificial graphite as the main lubricating phase in the lubricating component provides stable basic lubrication and friction coefficient regulation capability; the low proportion of sulfide as the auxiliary lubricating phase strengthens the high-temperature braking lubrication effect and suppresses the friction fluctuation under extreme working conditions, thereby reducing the friction coefficient of the metallurgical brake shoe during braking and reducing the wear during high-temperature braking.

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

[0055] When the above sulfide is used alone or in combination, the friction coefficient of the metallurgical brake shoe during braking is further reduced.

[0056] In some embodiments, the friction component includes chromite, alumina and carbide with a mass ratio of (8-12):(1-2):(1-2). The chromite has a particle size of 50-325 mesh and a Cr2O3 content of 25%-40%; the alumina powder has a particle size of -200 mesh and an Al2O3 content of ≥96%; and the carbide powder has a particle size of -325 mesh and a C content of ≥90%.

[0057] For example, the mass ratio of the chromite, the alumina and the carbide can be specifically selected as 8:1:1, 10:1.5:1.5, 12:2:2 or a range value composed of any point value, and is preferably (8-10):(1-1.5):(1.5-2).

[0058] When the technical scheme is adopted, the addition of the chromite, the alumina and the carbide makes the metallurgical brake shoe have higher heat resistance and friction performance during braking.

[0059] In some embodiments, the carbide includes at least one of silicon carbide, boron carbide, tungsten carbide and titanium carbide.

[0060] The carbide is used alone or in combination, and the heat resistance and friction performance of the metallurgical brake shoe during braking friction can be effectively improved.

[0061] The second aspect of the embodiment of the present application provides a preparation method of a powder metallurgy brake shoe for locomotive, which is applied to the preparation of the powder metallurgy brake shoe for locomotive and includes the following steps.

[0062] The raw materials are weighed according to the powder metallurgy brake shoe for locomotive;

[0063] The raw materials except the artificial graphite are premixed with the aviation kerosene, and then the artificial graphite is added for mixing to obtain a mixture; the mass percentage of the aviation kerosene in the mixture is 0.5% to 1.2%.

[0064] The shoe back and the mixture are sequentially placed in a mold cavity, and are pressed to obtain a green compact with a shoe back;

[0065] The green compact with a shoe back is subjected to limited sintering and cooling in an atmosphere of ammonia decomposition gas to obtain a sintered shoe;

[0066] The sintered shoe is subjected to re-pressing to obtain a finished shoe.

[0067] For example, the mass percentage of the aviation kerosene in the mixture can be specifically selected as 0.5%, 0.8%, 1%, 1.2% or a range value composed of any point value; and preferably 0.8% to 1%.

[0068] When the technical solution is adopted, the aviation kerosene temporarily adsorbs the metal powder, carbide and sulfide when the metal powder such as reduced iron powder and ultra-fine iron powder, the carbide and the sulfide are premixed with the aviation kerosene, so as to prevent the powder from entering the air during subsequent mixing. The limited pressure sintering tooling avoids the occurrence of cracks due to the free expansion of the side wall during sintering; and the re-pressing and shaping process improves the compactness of the metallurgical brake shoe.

[0069] In some embodiments, the stirring speed during premixing is 15 rpm to 30 rpm, and the stirring time is 70 min to 90 min.

[0070] For example, the stirring speed can be specifically selected as 15 rpm, 20 rpm, 25 rpm, 30 rpm or a range value composed of any point value; and preferably 20 rpm to 25 rpm; and the stirring time can be specifically selected as 70 min, 80 min, 90 min or a range value composed of any point value; and preferably 80 min to 90 min.

[0071] In some embodiments, the stirring speed during mixing is 15 rpm to 30 rpm, and the stirring time is 30 min to 50 min.

[0072] For example, the stirring speed can be specifically selected from 15 rpm, 20 rpm, 25 rpm, 30 rpm or a range of values composed of any point value; preferably 20 rpm to 25 rpm; and the stirring time can be specifically selected from 30 min, 40 min, 50 min or a range of values composed of any point value; preferably 40 min to 50 min.

[0073] Under the above stirring speed and stirring time, the final prepared metallurgical brake shoe has good uniformity and uniform density, and further improves the strength and high-temperature friction braking performance of the metallurgical brake shoe.

[0074] In some embodiments, sequentially placing the shoe back and the mixture into the mold cavity comprises: first placing the shoe back into the mold cavity bottom in contact with the lower punch, and then placing the mixture into the mold cavity.

[0075] When the shoe back and the lower punch are directly contacted and precisely positioned through the profile of the mold cavity, it is ensured that the shoe back does not shift during the pressing process. When the mixture is subsequently added and pressed, the mixture will tightly wrap the surface of the shoe back under the action of pressure to form a mechanical embedded interface. This positioning and filling method avoids the phenomenon of insufficient bonding area caused by the displacement of the shoe back when the mixture is filled, which is beneficial to the subsequent sintering and forming of the metallurgical brake shoe.

[0076] In some embodiments, the pressing is carried out at room temperature, and the pressing pressure acting on the friction body is 200 MPa to 400 MPa. It should be understood that "room temperature" here refers to the normal temperature in different seasons of spring, summer, autumn and winter.

[0077] For example, the pressing pressure can be specifically selected from 200 MPa, 300 MPa, 400 MPa or a range of values composed of any point value; preferably 300 MPa to 400 MPa.

[0078] Under the above pressing temperature and pressing pressure, the mixture and the shoe back are better combined, which is beneficial to the subsequent sintering and forming of the metallurgical brake shoe.

[0079] In some embodiments, the temperature during the limiting sintering is 900°C to 1100°C, the holding time during the limiting sintering is 2 h to 6 h, and the pressure during the limiting sintering is 4.5 MPa to 7.5 MPa.

[0080] For example, the temperature during the limiting sintering can be specifically selected from 900°C, 1000°C, 1100°C or a range of values composed of any point value; preferably 1000°C to 1100°C; the sintering time can be specifically selected from 2 h, 4 h, 6 h or a range of values composed of any point value; preferably 4 h to 6 h; and the sintering pressure can be selected from 4.5 MPa, 6 MPa, 7.5 MPa or a range of values composed of any point value; preferably 6 MPa to 7.5 MPa.

[0081] When the limited sintering temperature is 900-1100℃, the limited sintering holding time is 2-6h, and the limited sintering pressure is 4.5-7.5MPa, the diffusion welding of the particles of each component can be promoted, and then the alloyed copper base is formed, and the hardness and wear resistance of the metallurgical brake shoe are enhanced.

[0082] In some embodiments, the cooling is cooling to below 80℃.

[0083] For example, the temperature after cooling can be specifically selected as 20℃, 25℃, 30℃ or a range value composed of any point value; and preferably 20-25℃.

[0084] In the above technical solution, when the temperature is reduced to 20-30℃, the sintered shoe is rapidly cooled and formed.

[0085] In some embodiments, the re-pressing is re-pressing at 10-20MPa.

[0086] For example, the pressure during re-pressing can be specifically selected as 10MPa, 15MPa, 20MPa or a range value composed of any point value; and preferably 15-20MPa.

[0087] In the above technical solution, when the re-pressing pressure is 10-20MPa, the forming of the metallurgical brake shoe can be further promoted, and the compactness of the metallurgical brake shoe is improved.

[0088] In order to better illustrate the technical solutions of the present application, the present application further provides the following specific embodiments. It should be understood that the raw materials used in the following embodiments are all commercially available raw materials unless otherwise specified.

[0089] The composition and proportion of the metallurgical brake shoe in examples 1-4 are shown in table 1:

[0090] Table 1 Composition and proportion of the metallurgical brake shoe in examples 1-4

[0091]

[0092]

[0093] Example 1

[0094] A type of powder metallurgy brake shoe for locomotives, comprising, by mass percentage, 50% electrolytic copper powder, 7% reduced iron powder, 3% ultrafine iron powder, 3% atomized nickel powder, 3% molybdenum powder, 2% zinc powder, 13% artificial graphite, 3% antimony sulfide, 12% chromite, 2% alumina, and 2% silicon carbide. Specifically, the electrolytic copper powder has a particle size of -200 mesh and an oxygen content of 0.15%; the reduced iron powder has a particle size of -200 mesh and an oxygen content of 1.2%; the ultrafine iron powder has a particle size of 5μm to 7μm and an oxygen content of 1.2%; the atomized nickel powder has a particle size of -200 mesh and a total Ni+Co content of 99.72%; the molybdenum powder has a particle size of -500 mesh and a Mo content of 99.3%; and the zinc powder has a particle size of... -200 mesh, with a Zn content of 99.99%; artificial graphite with a particle size of -30 mesh to 30 mesh, and a C content of 99.98%; antimony sulfide with a particle size of -325 mesh; chromite with a particle size of 50 to 100 mesh, and a Cr2O3 content of 25%; alumina powder with a particle size of -200 mesh, and an Al2O3 content of 97%; silicon carbide powder with a particle size of -325 mesh, and a C content of 92%.

[0095] The preparation process of the above-mentioned powder metallurgy brake shoes for locomotives is as follows:

[0096] Weigh out the raw materials according to the above-mentioned powder metallurgy brake shoes for locomotives;

[0097] First, premix all raw materials except artificial graphite with aviation kerosene and stir at 15 rpm for 70 minutes. Then, add artificial graphite and mix, stirring at 15 rpm for 30 minutes to obtain a mixture. The mass percentage of aviation kerosene in the mixture is 1.2%.

[0098] First, place the tile back into the bottom of the mold cavity and contact it with the lower punch. Then, put the mixture into the mold cavity and press it at room temperature and 200MPa for 0.5min to obtain a pressed blank with a tile back.

[0099] Under the atmosphere of ammonia decomposition gas, the back-pressure blank with tile was sintered for 2 hours at a controlled temperature of 900℃ and a pressure of 4.5MPa, and then cooled to 20℃ to obtain sintered tiles.

[0100] Sintered tiles are subjected to re-pressing at 18 MPa to obtain metallurgical brake shoes for locomotives.

[0101] Example 2

[0102] A type of powder metallurgy brake shoe for locomotives, comprising, by mass percentage, 70% electrolytic copper powder, 6% reduced iron powder, 1% ultrafine iron powder, 1% atomized nickel powder, 1% molybdenum powder, 1% zinc powder, 8% artificial graphite, 2% molybdenum disulfide, 8% chromite, 1% alumina, and 1% boron carbide. Specifically, the electrolytic copper powder has a particle size of -200 mesh and an oxygen content of 0.2%; the reduced iron powder has a particle size of -200 mesh and an oxygen content of 1%; the ultrafine iron powder has a particle size of 1μm to 3.5μm and an oxygen content of 0.8%; the atomized nickel powder has a particle size of -200 mesh and a total Ni+Co content of 99.4%; the molybdenum powder has a particle size of -500 mesh and a Mo content of 99.91%; and the zinc powder has a particle size of - 200 mesh, with a Zn content of 99.36%; artificial graphite with a particle size of 30-60 mesh and a C content of 99.9%; molybdenum disulfide with a particle size of -325 mesh; chromite with a particle size of 100-220 mesh and a Cr2O3 content of 40%; alumina powder with a particle size of -200 mesh and an Al2O3 content of 96%; boron carbide powder with a particle size of -325 mesh and a C content of 90%.

[0103] The preparation process of the above-mentioned powder metallurgy brake shoes for locomotives is as follows:

[0104] Weigh out the raw materials according to the above-mentioned powder metallurgy brake shoes for locomotives;

[0105] First, premix all raw materials except artificial graphite with aviation kerosene and stir at 20 rpm for 90 minutes. Then, add artificial graphite and mix, stirring at 20 rpm for 50 minutes to obtain a mixture. The mass percentage of aviation kerosene in the mixture is 1%.

[0106] First, place the tile back into the bottom of the mold cavity and contact it with the lower punch. Then, put the mixture into the mold cavity and press it at room temperature and 300MPa for 0.5 minutes to obtain a pressed blank with a tile back.

[0107] Under the atmosphere of ammonia decomposition gas, the back-pressure blank with tile was sintered for 6 hours at a controlled temperature of 1100℃ and a pressure of 7.5MPa, and then cooled to 70℃ to obtain sintered tiles.

[0108] Sintered tiles are subjected to re-pressing at 19 MPa to obtain metallurgical brake shoes for locomotives.

[0109] Example 3

[0110] The locomotive powder metallurgy brake shoe is prepared from the following raw materials in percentage by mass: 60% of electrolytic copper powder, 6.5% of reduced iron powder, 2.5% of superfine iron powder, 2.5% of atomized nickel powder, 2% of molybdenum powder, 1.5% of zinc powder, 9.5% of artificial graphite, 2.5% of copper sulfide, 10% of chromite, 1.5% of aluminum oxide and 1.5% of tungsten carbide. The electrolytic copper powder has a particle size of -200 mesh and an oxygen content of 0.1%; the reduced iron powder has a particle size of -200 mesh and an oxygen content of 0.7%; the superfine iron powder has a particle size of 3-5 microns and an oxygen content of 0.8%; the atomized nickel powder has a particle size of -200 mesh and a total content of Ni+Co of 99.99%; the molybdenum powder has a particle size of -500 mesh and a Mo content of 99.9%; the zinc powder has a particle size of -200 mesh and a Zn content of 99.95%; the artificial graphite has a particle size of 60-100 mesh and a C content of 99.99%; the copper sulfide has a particle size of -325 mesh; the chromite has a particle size of 220-325 mesh and a Cr2O3 content of 32%; the aluminum oxide powder has a particle size of -200 mesh and an Al2O3 content of 98.5%; and the tungsten carbide powder has a particle size of -325 mesh and a C content of 94.5%.

[0111] The preparation process of the above locomotive powder metallurgy brake shoe is as follows:

[0112] The raw materials of the above locomotive powder metallurgy brake shoe are weighed;

[0113] The raw materials except the artificial graphite are premixed with aviation kerosene, stirred at 25 rpm for 80 min, and then the artificial graphite is added and stirred at 25 rpm for 40 min to obtain a mixture; the mass percentage of the aviation kerosene in the mixture is 0.8%.

[0114] First, the shoe back is placed in contact with the lower punch at the bottom of the mold cavity, and then the mixture is placed in the mold cavity, and the green compact with shoe back is obtained by pressing at room temperature and 400 MPa for 0.5 min.

[0115] The green compact with shoe back is subjected to limited sintering at a temperature of 1000℃ and a pressure of 6 MPa for 4 h in an atmosphere of ammonia decomposition gas, and then cooled to 60℃ to obtain a sintered shoe.

[0116] The sintered shoe is subjected to repressing at 20 MPa to obtain the locomotive powder metallurgy brake shoe.

[0117] Example 4

[0118] The locomotive powder metallurgy brake shoe comprises, in terms of mass percentage of raw material of the powder metallurgy brake shoe, 55% of electrolytic copper powder, 6.2% of reduced iron powder, 1.8% of superfine iron powder, 2.3% of atomized nickel powder, 1.5% of molybdenum powder, 1.2% of zinc powder, 13% of artificial graphite, 3% of zinc sulfide, 12% of chromite, 2% of aluminum oxide and 2% of titanium carbide. The electrolytic copper powder has a particle size of -200 mesh and an oxygen content of 0.15%; the reduced iron powder has a particle size of -200 mesh and an oxygen content of 0.7%; the superfine iron powder has a particle size of 2-4 microns and an oxygen content of 1%; the atomized nickel powder has a particle size of -200 mesh and a total content of Ni+Co of 99.7%; the molybdenum powder has a particle size of -500 mesh and a Mo content of 99.9%; the zinc powder has a particle size of -200 mesh and a Zn content of 99.9%; the artificial graphite has a particle size of -10-+20 mesh and a C content of 99.99%; the zinc sulfide has a particle size of -325 mesh; the chromite has a particle size of 60-100 mesh and a Cr2O3 content of 35%; the aluminum oxide powder has a particle size of -200 mesh and an Al2O3 content of 96.5%; and the titanium carbide powder has a particle size of -325 mesh and a C content of 91%.

[0119] The preparation process of the above-mentioned locomotive powder metallurgy brake shoe is as follows:

[0120] The raw materials of the above-mentioned locomotive powder metallurgy brake shoe are weighed;

[0121] The other raw materials except the artificial graphite are premixed with aviation kerosene, stirred at 30 rpm for 80 min, and then the artificial graphite is added and mixed, stirred at 30 rpm for 40 min to obtain a mixture; the mass percentage of the aviation kerosene in the mixture is 0.8%.

[0122] First, the shoe back is placed in contact with the lower punch at the bottom of the mold cavity, and then the mixture is placed in the mold cavity, and the green compact with shoe back is obtained by pressing at room temperature at 400 MPa for 0.5 min.

[0123] The green compact with shoe back is subjected to limited sintering at a temperature of 1000 DEG C and a pressure of 6.5 MPa for 4 h in an atmosphere of ammonia decomposition gas, and cooled to 40 DEG C to obtain a sintered shoe.

[0124] The sintered shoe is subjected to re-pressing at 20 MPa to obtain the locomotive metallurgy brake shoe.

[0125] Comparative Example 1

[0126] Taking Example 3 as an example, compared with Example 3, the difference lies in that the total mass percentage of the artificial graphite and the copper sulfide in the lubricating component is reduced to 5%, wherein the ratio of the artificial graphite and the copper sulfide remains unchanged, still 9.5:2.5; at the same time, the mass percentage of the electrolytic copper powder is increased to 67%; the rest of the components and the preparation method remain unchanged.

[0127] Comparative Example 2

[0128] Example 3 was taken as an example, compared with Example 3, the difference was that the mass percentage of artificial graphite in the lubricating component was reduced to 5%, and the mass percentage of copper sulfide was increased to 7%, and the rest of the components and the preparation method were unchanged.

[0129] Comparative Example 3

[0130] Example 4 was taken as an example, compared with Example 4, the difference was that the artificial graphite in the lubricating component was replaced with an equal amount of zinc sulfide, and only artificial graphite was used as the lubricating component, and the rest of the components and the preparation method were unchanged.

[0131] Comparative Example 4

[0132] Example 4 was taken as an example, compared with Example 4, the difference was that the artificial graphite in the lubricating component was replaced with an equal amount of zinc sulfide, and only artificial graphite was used as the lubricating component, and the rest of the components and the preparation method were unchanged.

[0133] Comparative Example 5

[0134] The conventional brake pad on the market at present: by mass percentage, it includes:

[0135] Base component: 1000 mesh electrolytic copper powder, 47%; 1000 mesh reduced iron powder, 16%;

[0136] Lubricating component: 100 mesh artificial graphite powder, 18%; 300 nanometer molybdenum disulfide powder, 2%; 500 nanometer calcium fluoride powder, 5%.

[0137] Friction component: 100 mesh chromium powder, 7%; 1 micron silicon carbide powder, 2%; 1 nanometer silicon carbide powder, 1%; Friction stabilizing component: 80 mesh natural flake graphite powder, 2%.

[0138] The preparation method of the above brake pad is prepared according to the preparation method in Chinese patent publication No. CN 110387212 A.

[0139] Take the brake shoe products of Example 1~Example 4, Comparative Example 1~Comparative Example 5, and measure the friction coefficient. The friction coefficient is tested by LINK brake dynamic test bench of Beijing Puran Company, and the test method is according to the “Test procedure for powder metallurgy brake shoe for locomotive” compiled by the company. When testing, the wheel diameter is 1250mm, the brake friction radius is 625mm, the maximum pressure on both sides is 30kN, the axle load is 25t, the test speed is 20km / h~160km / h, and the test results of Example 1~Example 4, Comparative Example 1~Comparative Example 5 are shown in Table 2;

[0140] Table 2 test results

[0141]

[0142]

[0143] From the data in Table 2, the average friction coefficients of the brake pads in Examples 1-4 under different braking conditions in dry state are between 0.33 and 0.47, the friction coefficient changes little, the stability of the friction coefficient is high, and the effective braking in use can be ensured. In addition, the wear amount of the brake pad is between 0.08 and 0.12 cm 3 / MJ, the wear amount is low, the friction performance is stable, and the service life is long.

[0144] In Comparative Example 1 and Comparative Example 2, because the mass ratio of the artificial graphite and copper sulfide in the lubricating component is greatly changed, the average friction coefficient in dry state is between 0.258 and 0.457, the fluctuation range of the average friction coefficient of the brake pads in dry state under different braking conditions in Examples 1-4 is much increased, and the fluctuation range is proportional to the change of the initial speed of braking, especially at high speed and high pressure, the friction coefficient is significantly reduced, the lowest is 0.258 and 0.279; and the wear amount (0.57 cm 3 / MJ and 0.48 cm 3 / MJ) is about 5 times that of Examples 1-4, the maximum noise in the test reaches 110 dB and 100 dB, so that the braking performance of the product is unstable and cannot meet the use requirements.

[0145] In Comparative Example 3 and Comparative Example 4, only one kind of lubricating component, artificial graphite or zinc sulfide, is used, compared with the multiple lubricating components in Examples 1-4, the overall friction coefficient is low, and the noise is increased to 93 and 96 dB.

[0146] In Comparative Example 5, the reinforcing components such as nickel, molybdenum and zinc are missing, resulting in low alloying degree of the base body and low high-temperature strength of the brake shoe base body, compared with Examples 1-4, the average friction coefficient at high speed is greatly reduced, and the use requirements of train braking cannot be met.

[0147] The above describes the embodiments of the present disclosure. However, these embodiments are only for illustrative purposes, and are not intended to limit the scope of the present disclosure. The scope of the present disclosure is defined by the appended claims and their equivalents. Without departing from the scope of the present disclosure, those skilled in the art can make various substitutions and modifications, which should all fall within the scope of the present disclosure.

Claims

1. A powder metallurgy brake shoe for a locomotive, characterized by, The powder metallurgy brake shoe is composed of 50-70% of a base component, 10-18% of a reinforcing component, 10-16% of a lubricating component, and 10-16% of a friction component, in terms of mass percentage; The base component comprises electrolytic copper powder; the reinforcing component comprises reduced iron powder, ultrafine iron powder, atomized nickel powder, molybdenum powder, and zinc powder; and the lubricating component comprises artificial graphite and sulfide.

2. The powder metallurgy brake shoe for a locomotive according to claim 1, characterized by, In the reinforcing component, the mass ratio of the reduced iron powder, the ultrafine iron powder, the atomized nickel powder, the molybdenum powder, and the zinc powder is (6-7):(1-3):(1-3):(1-3):(1-2).

3. The powder metallurgy brake shoe for a locomotive according to claim 1, wherein In the lubricating component, the mass ratio of the artificial graphite and the sulfide is (8-13):(2-3).

4. The powder metallurgy brake shoe for a locomotive according to claim 1 or 3, characterized by, The sulfide comprises at least one of antimony sulfide, molybdenum disulfide, copper sulfide, tin sulfide, zinc sulfide, and manganese sulfide.

5. The powder metallurgy brake shoe for a locomotive according to claim 1, wherein The friction component comprises chromite, alumina, and carbide in a mass ratio of (8-12):(1-2):(1-2).

6. The powder metallurgy brake shoe for a locomotive according to claim 5, wherein The carbide comprises at least one of silicon carbide, boron carbide, tungsten carbide, and titanium carbide.

7. A method for producing a powder metallurgy brake shoe for a locomotive, which is applied to the powder metallurgy brake shoe for a locomotive according to any one of claims 1 to 6, characterized by, The method comprises the following steps: The raw materials of the powder metallurgy brake shoe are weighed according to any one of claims 1-6; The other raw materials except the artificial graphite are premixed with aviation kerosene, and then the artificial graphite is added and mixed to obtain a mixture; the mass percentage of the aviation kerosene in the mixture is 0.5%-1.2%; The shoe back and the mixture are sequentially placed in a mold cavity, and then pressed to obtain a shoe back pressing blank; The shoe back pressing blank is subjected to limited sintering in an atmosphere of ammonia decomposition gas and then cooled to obtain a sintered shoe; The sintered shoe is subjected to re-pressing to obtain a finished shoe.

8. The method of claim 7, wherein the powder metallurgy brake shoe for a locomotive is prepared by the steps of: The stirring speed during the premixing is 15-30 rpm, and the stirring time is 70-90 min; and / or The stirring speed during the mixing is 15-30 rpm, and the stirring time is 30-50 min.

9. The method of claim 7, wherein the powder metallurgy brake shoe for a locomotive is prepared by the steps of: The shoe back and the mixture are sequentially placed in a mold cavity, and then pressed to obtain a shoe back pressing blank; The shoe back is first placed in the bottom of the mold cavity and then contacted with a lower punch, and then the mixture is placed in the mold cavity; and / or The pressing is carried out at room temperature, and the pressing pressure acting on the friction body is 200-400 MPa.

10. The method of claim 7, wherein the powder metallurgy brake shoe for a locomotive is prepared by the steps of: The temperature during the limited sintering is 900-1100°C, the limited sintering holding time is 2-6 h, and the limited sintering pressure is 4.5-7.5 MPa; and / or The cooling is to a temperature below 80°C; and / or The re-pressing is carried out at a pressure of 10-20 MPa.

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