Preparation method of brake disc for rail transit vehicle

Abstract

According to the preparation method of the brake disc for the rail transit vehicle, a concave pit is formed in the position, corresponding to a circular truncated cone, of a friction powder blank layer, and the concave pit is filled with materials of a heat dissipation powder blank layer, so that the heat dissipation powder blank layer and the friction powder blank layer form a concave-convex embedded connection structure, and the combination area of the two materials can be effectively increased; mutual intervention of the two materials in the particle size is promoted, so that the interface bonding capacity is effectively improved, and meanwhile, the machining difficulty of bolt holes and key grooves is reduced. Meanwhile, through the three-layer structural design, disc body deformation caused by expansion and shrinkage differences in the sintering and shaping process can be effectively reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of powder metallurgy, and particularly to a preparation method of a brake disc for rail transit vehicles. Background Art

[0002] Aluminum matrix composites have received extensive attention due to their low density, high strength, high hardness and excellent wear resistance. Among them, aluminum matrix brake discs can reduce weight by 40% - 65% compared with traditional cast iron brake discs, and the lightweight effect is obvious. There are a large number of researches and applications in the fields of rail transit and passenger car brake discs.

[0003] At present, the preparation methods of aluminum matrix composite brake discs include stir casting method, powder metallurgy method, infiltration method, spray deposition method, etc. In the field of rail transit, at low speeds such as 80 - 120 km / h, the braking energy is low, and aluminum matrix composites with a ceramic content of 20 - 30 vt% prepared by various methods such as stir casting, powder metallurgy, friction stir welding, and spray deposition can all meet the use requirements; but for higher speed grades, the heat resistance and wear resistance of aluminum matrix brake discs need to be further improved. It is necessary to select aluminum matrix composites with medium to high volume fractions or increase the particle size of ceramic reinforcement phases to improve the heat resistance of aluminum matrix brake discs. The powder metallurgy method is a process method that can most quickly realize the flexible adjustment and application of components, and the highest ceramic content can reach 70 vt%.

[0004] However, the increase in ceramic content will further increase the processing difficulty of aluminum matrix composites. Although diamond tools can be selected for processing at present, there are still problems such as large processing difficulty, long cycle and high cost. At the same time, when preparing an integral brake disc with aluminum matrix composites with medium to high volume fractions, the toughness and strength of the material decrease, and there are risks at key load-bearing points such as key grooves and bolts on the heat dissipation rib surface, and there is a toughness risk for thin-walled heat dissipation ribs.

[0005] Although the traditional double-layer disc can solve the problems of the integral disc, most of them are difficult to avoid the problems of deformation during the disc preparation process and weak interfacial bonding force caused by the difference in expansion coefficients of the two materials, and there is a large interfacial fluctuation at the corresponding frustum position, and the processing difficulty at bolt holes and key grooves is large. Summary of the Invention

[0006] Based on this, it is necessary to provide a preparation method of a brake disc for rail transit vehicles that can effectively reduce the deformation of the disc body, improve the interfacial bonding force, reduce the interfacial fluctuation, and thus effectively reduce the processing difficulty at bolt holes and key grooves.

[0007] A preparation method of a brake disc for a rail transit vehicle, the brake disc for a rail transit vehicle comprising a heat dissipation layer and a friction layer, the heat dissipation layer comprising a heat dissipation base provided on the friction layer, heat dissipation ribs uniformly distributed on the heat dissipation base, and a frustum for forming bolt holes and key grooves, the preparation method of the brake disc for a rail transit vehicle comprising the following steps:

[0008] Provide a brake disc green compact, the brake disc green compact comprising a heat dissipation green compact layer, a friction green compact layer, and a machining allowance green compact layer stacked in sequence, the heat dissipation green compact layer and the machining allowance green compact layer being prepared from a first aluminum matrix composite material, the volume content of ceramic particles in the first aluminum matrix composite material being 10% - 20%, and the average particle size being 5um - 10um, the friction green compact layer being prepared from a second aluminum matrix composite material, the volume content of ceramic particles in the second aluminum matrix composite material being 35% - 50%, and the average particle size being 20um - 100um, a concave pit being provided at a position corresponding to the frustum in the friction green compact layer, and the material of the heat dissipation green compact layer being filled in the concave pit to form a concave-convex fitting connection structure with the friction green compact layer;

[0009] After sintering the brake disc green compact, shape the heat dissipation ribs and the frustum to obtain a blank comprising a heat dissipation layer, a friction layer, and a machining allowance layer;

[0010] Machine-process to remove the machining allowance layer, and machine-process the bolt holes and key grooves at corresponding positions of the frustum to obtain the brake disc for a rail transit vehicle.

[0011] In one embodiment, the preparation method of the brake disc green compact is as follows:

[0012] Provide the first aluminum matrix composite material and the second aluminum matrix composite material;

[0013] Lay the first aluminum matrix composite material and the second aluminum matrix composite material in sequence according to the stacking order of the heat dissipation green compact layer, the friction green compact layer, and the machining allowance green compact layer, and press and form to obtain the brake disc green compact.

[0014] In one embodiment, the thickness of the machining allowance layer is 2mm - 5mm.

[0015] In one embodiment, the thickness of the friction layer is 11mm - 16mm.

[0016] In one embodiment, the thickness of the heat dissipation layer is 36mm - 40mm.

[0017] In one embodiment, the depth of the concave pit is 1 / 3 - 2 / 3 of the thickness of the friction green compact layer.

[0018] In one embodiment, the pit is a frustum-shaped pit with an inclination of the pit wall of 5° to 15°.

[0019] In one embodiment, the pressure for press forming is 200 MPa to 300 MPa.

[0020] In one embodiment, the sintering temperature is 580 °C to 640 °C.

[0021] In one embodiment, the sizing temperature is 500 °C to 580 °C and the pressure is 150 MPa to 300 MPa.

[0022] The preparation method of the brake disc for rail transit vehicles described above, by arranging a pit at the position corresponding to the frustum on the friction powder blank layer and filling the material of the heat dissipation powder blank layer in the pit, enables the heat dissipation powder blank layer and the friction powder blank layer to form a concave-convex interlocking connection structure, which can effectively increase the bonding area of the two materials, promote the mutual penetration of the two materials at the particle scale, and thus effectively improve the interfacial bonding ability.

[0023] Since the heat dissipation powder blank layer is prepared from a first aluminum matrix composite material with a ceramic particle volume content of 10% to 20% and an average particle size of 5 μm to 10 μm, and the friction powder blank layer is prepared from a second aluminum matrix composite material with a ceramic particle volume content of 35% to 50% and an average particle size of 20 μm to 100 μm, after sintering and sizing, the first aluminum matrix composite material in the pit flows to fill the frustum part, and at the same time, the second aluminum matrix composite material flows to fill the pit. After sizing, the whole frustum is composed of the first aluminum matrix composite material with a low ceramic content, effectively reducing the processing difficulty at the bolt holes and keyways.

[0024] At the same time, through the three-layer structure design, the deformation of the disc body caused by the difference in expansion and contraction during sintering and sizing can be effectively reduced.

[0025] In addition, for the brake disc for rail transit vehicles prepared by the above method, the fluctuation of the interface between the two materials in the thickness direction is greatly reduced, reducing the observation and analysis difficulty of ultrasonic testing and improving the detection accuracy. Detailed implementation mode

[0026] To facilitate the understanding of the present invention, the present invention will be described more comprehensively below, and preferred embodiments of the present invention are given. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0027] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the technical field to which this invention belongs. The terms used in the specification of the present invention are for the purpose of describing specific embodiments only and are not intended to limit the present invention. The term "and / or" as used herein includes any and all combinations of one or more of the related listed items.

[0028] It should be noted that the brake disc for rail transit vehicles to be prepared in this application includes a heat dissipation layer and a friction layer, wherein the heat dissipation layer includes a heat dissipation base provided on the friction layer, heat dissipation ribs evenly distributed on the heat dissipation base, and a frustum for forming bolt holes and key grooves.

[0029] Further, three frustums are in a group, and there are a total of six groups, which are evenly distributed along the heat dissipation base. Among each group of frustums, the middle frustum is used to form a key groove, and the frustums on both sides are respectively used to form bolt holes.

[0030] The preparation method of the above-mentioned brake disc for rail transit vehicles includes the following steps S110 to S130:

[0031] S110. Provide a brake disc green compact, which includes a heat dissipation green compact layer, a friction green compact layer, and a machining allowance green compact layer stacked in sequence. A concave pit is provided at the position corresponding to the frustum in the friction green compact layer, and the material of the heat dissipation green compact layer is filled in the concave pit to form a concave-convex fitting connection structure with the friction green compact layer.

[0032] In this embodiment, the concave pit is an inverted frustum-shaped concave pit. Further, the slope of the pit wall of the inverted frustum-shaped concave pit is 5° to 15°. It can be understood that the pit wall of the inverted frustum-shaped concave pit is arc-connected to the pit bottom.

[0033] Further, the depth of the concave pit is 1 / 3 to 2 / 3 of the thickness of the friction green compact layer.

[0034] The design of the above-mentioned concave pit is, on the one hand, to ensure that the interface between the two materials in the friction layer is as flat as possible after shaping. On the other hand, if the concave pit is too deep, it may cause the first aluminum matrix composite material to penetrate and distribute to the surface of the friction layer. If the concave pit is too shallow, the effect of improving the interface distribution is not obvious, and the second aluminum matrix composite material still invades a large range inside the frustum.

[0035] By filling the material of the heat dissipation green compact layer (i.e., the first aluminum matrix composite material) in the concave pit, so that the heat dissipation green compact layer and the friction green compact layer form a concave-convex fitting connection structure, the bonding area of the two materials can be effectively increased, and the two materials can be promoted to interpenetrate at the particle scale, thereby effectively improving the interfacial bonding force.

[0036] Specifically, the brake disc green compact is prepared by the following methods S1101 to S1103:

[0037] S1101. Provide a first aluminum matrix composite material for preparing a heat dissipation powder blank layer and a machining allowance powder blank layer. The volume content of ceramic particles in the first aluminum matrix composite material is 10% - 20%, and the average particle size of the ceramic particles is 5 μm - 10 μm.

[0038] When using the above first aluminum matrix composite material to prepare the heat dissipation powder blank layer and the machining allowance powder blank layer, since the volume content of ceramic particles is only 10% - 20% and the average particle size is relatively small (5 μm - 10 μm), this material has high strength, high toughness and good plastic deformation ability. When used to prepare the heat dissipation powder blank layer, it is beneficial to the good filling of complex heat dissipation ribs and frustum during the shaping stage. When used to prepare the machining allowance powder blank layer, it is beneficial to be easily machined and removed after shaping.

[0039] S1102. Provide a second aluminum matrix composite material for preparing a friction powder blank layer. The volume content of ceramic particles in the second aluminum matrix composite material is 35% - 50%, and the average particle size is 20 μm - 100 μm.

[0040] When using the above second aluminum matrix composite material to prepare the friction powder blank layer, since the volume content of ceramic particles is as high as 35% - 50% and the average particle size is relatively large (20 μm - 100 μm), the hardness and wear resistance of this material can be significantly improved. When used to prepare the friction powder blank layer, after sintering and shaping, the friction layer can directly bear the friction load and high temperature, and has good wear resistance, high temperature strength and anti-deformation ability.

[0041] S1103. Lay the above first aluminum matrix composite material and second aluminum matrix composite material in the mold in the stacking order of the heat dissipation powder blank layer, the friction powder blank layer and the machining allowance powder blank layer, demold after pressing and forming, and obtain a brake disc powder blank.

[0042] Specifically, first use the first aluminum matrix composite material to lay to form a machining allowance powder blank layer, then use the second aluminum matrix composite material to lay on the surface of the machining allowance powder blank layer to form a friction powder blank layer. There is a concave pit at the position corresponding to the frustum of the friction powder blank layer. Finally, use the first aluminum matrix composite material to lay on the surface of the friction powder blank layer to form a heat dissipation powder blank layer.

[0043] In this embodiment, the pressure for pressing and forming is 200 MPa - 300 MPa.

[0044] It should be noted that the above brake disc powder blank can also be prepared by other methods, as long as the three-layer powder blank structure of the present application can be obtained and the heat dissipation powder blank layer and the friction powder blank layer are concavo-convexly fitted.

[0045] S120. Sinter the above brake disc powder blank and shape out heat dissipation ribs and frustum to obtain a blank including a heat dissipation layer, a friction layer and a machining allowance layer.

[0046] Among them, the thickness of the heat dissipation layer is 36 mm to 40 mm. The thickness of the friction layer is 11 mm to 16 mm. The thickness of the machining allowance layer is 2 mm to 5 mm.

[0047] It can be understood that the machining allowance layer can be divided into a rough machining allowance layer and a blind area layer for ultrasonic flaw detection. Among them, the rough machining allowance layer needs to be removed to eliminate the influence of the original surface roughness and release agent on the detection, and the blind area layer can also be removed after detection.

[0048] In this embodiment, the sintering temperature is 580 °C to 640 °C. The sizing temperature is 500 °C to 580 °C, and the pressure is 150 MPa to 300 MPa.

[0049] S130. Machine-process and remove the above machining allowance layer to obtain a brake disc for rail transit vehicles.

[0050] In this application, by covering a machining allowance layer with a low volume content of ceramic particles on the surface of the friction layer, the removal difficulty is greatly reduced.

[0051] The above method for preparing a brake disc for rail transit vehicles can effectively reduce the cooling warping problem caused by the difference in thermal expansion coefficients of the two materials during the sintering and cooling process by preparing a blank including a heat dissipation layer, a friction layer, and a machining allowance layer, and the deformation amount can be reduced by 70% to 80%.

[0052] The design of the concave pits increases the contact area of the key parts, improves the interfacial bonding force, and reduces the machining difficulty at the bolt holes and keyways.

[0053] The following are specific examples.

[0054] Example 1

[0055] (1) Provide a first aluminum matrix composite material: silicon carbide particles with a volume content of 10% and an average particle size of 5 μm are added to the aluminum matrix.

[0056] (2) Provide a second aluminum matrix composite material: silicon carbide particles with a volume content of 35% and an average particle size of 20 μm are added to the aluminum matrix.

[0057] (3) First, use the first aluminum matrix composite material to lay a machining allowance powder blank layer, then use the second aluminum matrix composite material to lay a friction powder blank layer, and press out concave pits at the corresponding frustum positions of the friction powder blank layer. The depth of the concave pits is 1 / 3 of the thickness of the friction powder blank layer, and the slope of the pit wall is 10°. Finally, use the first aluminum matrix composite material to lay a heat dissipation powder blank layer and press and form it. The pressure for pressing and forming is 200 MPa to obtain a brake disc powder blank.

[0058] (4) Place the powder blank in a vacuum sintering furnace, keep it at 580 °C for 2 hours to complete densification. Then shape it at 500 °C and 300 MPa to form heat dissipation ribs and frustum, obtaining a blank including a heat dissipation layer (with a thickness of 40 mm), a friction layer (with a thickness of 11 mm) and a machining allowance layer (2 mm).

[0059] (5) Machine to remove the machining allowance layer, and correspondingly machine bolt holes and keyways at the frustum for finish machining to obtain a brake disc for rail transit vehicles.

[0060] Example 2

[0061] Adjust the volume content of ceramic particles in the first aluminum matrix composite to 20%, and the average particle size to 10 μm; adjust the volume content of ceramic particles in the second aluminum matrix composite to 50%, and the average particle size to 100 μm. The slope of the pit wall is 5°, and the depth is 2 / 3 of the thickness of the friction powder blank layer. The compression molding pressure is 300 MPa, the sintering temperature is 640 °C, the shaping temperature is 580 °C, and the shaping pressure is 150 MPa. The heat dissipation layer (with a thickness of 36 mm), the friction layer (with a thickness of 16 mm) and the machining allowance layer (5 mm). The remaining steps are the same as those in Example 1.

[0062] Example 3

[0063] Adjust the first aluminum matrix composite to add ceramic particles with a volume content of 15% and an average particle size of 8 μm in an aluminum alloy matrix; adjust the second aluminum matrix composite to add ceramic particles with a volume content of 45% and an average particle size of 80 μm in an aluminum alloy matrix. The slope of the pit wall is 15°, and the depth is 1 / 3 of the thickness of the friction powder blank layer. The compression molding pressure is 250 MPa, the sintering temperature is 620 °C, the shaping temperature is 550 °C, and the shaping pressure is 200 MPa. The heat dissipation layer (with a thickness of 38 mm), the friction layer (with a thickness of 14 mm) and the machining allowance layer (4 mm). The remaining steps are the same as those in Example 1.

[0064] After testing, for the brake discs prepared in Examples 1 to 3, the interfacial bonding strength ≥ 200 MPa. The machining time of bolt holes and keyways is shortened by about 40%, and the tool wear rate is reduced by about 50%.

[0065] Comparative Example 1

[0066] Use a traditional single aluminum matrix composite (with a ceramic particle volume content of 40%) to prepare a brake disc. The results show that chipping and relatively serious tool wear occur during the machining of bolt holes and keyways.

[0067] Comparative Example 2

[0068] The brake disc is prepared by using a traditional double-layer aluminum matrix composite material (the ceramic content of the friction surface is 40%, and the ceramic content of the heat dissipation rib surface is 10%). The results show that after machining, the thickness of the friction material at the inner diameter is 3 mm, and the thickness of the friction material at the outer diameter is 6 mm.

[0069] Through the hierarchical design and the concave-convex fitting structure, the present application effectively improves the interfacial bonding strength between the heat dissipation layer and the friction layer, and at the same time reduces the machining difficulty at the bolt holes and key grooves, and is applicable to the braking system of high-speed rail transit vehicles.

[0070] The above-described embodiments only represent several implementation manners of the present invention. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the present invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several deformations and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention patent shall be subject to the appended claims.

Claims

1. A preparation method of a brake disc for a rail transit vehicle, the brake disc for the rail transit vehicle comprising a heat dissipation layer and a friction layer, the heat dissipation layer including a heat dissipation base provided on the friction layer, heat dissipation ribs uniformly distributed on the heat dissipation base, and a frustum for forming bolt holes and key grooves, characterized in that, The preparation method of the brake disc for rail transit vehicles comprises the following steps: Provide a brake disc powder blank, which includes a heat dissipation powder blank layer, a friction powder blank layer and a machining allowance powder blank layer stacked in sequence. The heat dissipation powder blank layer and the machining allowance powder blank layer are made of a first aluminum matrix composite material, in which the volume content of ceramic particles is 10% - 20% and the average particle size is 5um - 10um. The friction powder blank layer is made of a second aluminum matrix composite material, in which the volume content of ceramic particles is 35% - 50% and the average particle size is 20um - 100um. A concave pit is provided at the position corresponding to the frustum on the friction powder blank layer, and the material of the heat dissipation powder blank layer is filled in the concave pit to form a concave-convex fitting connection structure with the friction powder blank layer; After sintering the brake disc powder blank, shape the heat dissipation ribs and the frustum to obtain a blank including the heat dissipation layer, the friction layer and the machining allowance layer; Machine-process to remove the machining allowance layer, and correspondingly machine the bolt holes and key grooves at the frustum to obtain the brake disc for rail transit vehicles.

2. The preparation method of the brake disc for rail transit vehicles according to claim 1, characterized in that, The preparation method of the brake disc powder blank is as follows: Provide the first aluminum matrix composite material and the second aluminum matrix composite material; Lay the first aluminum matrix composite material and the second aluminum matrix composite material in sequence according to the stacking order of the heat dissipation powder blank layer, the friction powder blank layer and the machining allowance powder blank layer, and press them into shape to obtain the brake disc powder blank.

3. The preparation method of the brake disc for rail transit vehicles according to claim 1, characterized in that, The thickness of the machining allowance layer is 2mm - 5mm.

4. The preparation method of the brake disc for rail transit vehicles according to claim 1, characterized in that, The thickness of the friction layer is 11mm - 16mm.

5. The preparation method of the brake disc for rail transit vehicles according to claim 1, wherein, The thickness of the heat dissipation layer is 36mm - 40mm.

6. The preparation method of the brake disc for rail transit vehicles according to claim 1, characterized in that, The depth of the concave pit is 1 / 3 - 2 / 3 of the thickness of the friction powder blank layer.

7. The preparation method of the brake disc for rail transit vehicles according to claim 6, wherein, The concave pit is a truncated cone-shaped concave pit, and the slope of the pit wall of the truncated cone-shaped concave pit is 5° - 15°.

8. The preparation method of the brake disc for rail transit vehicles according to any one of claims 2 to 7, characterized in that, The pressure for pressing into shape is 200MPa - 300MPa.

9. The preparation method of the brake disc for rail transit vehicles according to any one of claims 1 to 7, characterized in that, The temperature for sintering is 580°C - 640°C.

10. The preparation method of the brake disc for rail transit vehicles according to any one of claims 1 to 7, characterized in that, The temperature for shaping is 500°C - 580°C, and the pressure is 150MPa - 300MPa.