Preparation method of brake disc for rail transit vehicle

Abstract

The invention relates to a preparation method of a brake disc for a rail transit vehicle, which comprises the following steps: completely filling a friction layer, a heat dissipation substrate and heat dissipation ribs in a forming stage, but only forming a part of a circular truncated cone, only forming 70-85% of the overall height of the circular truncated cone and 65-85% of the overall inclination of the circular truncated cone, and meanwhile, controlling the shaping pressure to be 150-250MPa, the temperature to be 350-380 DEG C and the time to be 10-30 seconds, so as to facilitate demolding, and meanwhile, forming the brake disc for the rail transit vehicle. When the boss and the remaining circular truncated cone are filled, axial and circumferential materials can synchronously flow to fill the mold cavity, and the situation that the materials flow in other directions after reaching the mold wall and rub the mold wall to roll in a mold release agent attached to the mold wall, and the mold release agent is accumulated is effectively avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of brake discs, in particular to a preparation method of brake discs for rail transit vehicles. Background Art

[0002] The ceramic-reinforced aluminum matrix composite brake disc is an important lightweight component for rail transit vehicles. In the early stage, the brake discs for rail transit vehicles were mainly prepared by the stir casting process. Due to the inevitable problems such as easy segregation of ceramic particles in the stir casting process, the volume content of ceramic particles is usually difficult to exceed 25%, resulting in difficult improvement of the wear resistance and other properties of the brake disc, and the application range of the prepared brake disc is also difficult to break through the speed grade of 120 km / h.

[0003] Powder metallurgy can solve the problem of material segregation and break through the volume content of ceramic particles, so that the volume content of ceramic particles in the aluminum matrix composite brake disc for rail transit vehicles can be as high as more than 50%. For example, CN111250698B discloses a lightweight and wear-resistant aluminum matrix powder metallurgy composite rail transit brake disc, which is prepared by cold pressing, sintering and integrated hot pressing and shaping processes, and the mass content of its ceramic particles can be as high as 75%.

[0004] However, with the increase of the volume content of ceramic particles, the fluidity and deformation ability of the material will both decrease. Using the traditional powder metallurgy process, in the hot pressing and shaping process, the positions with large local deformation (such as the round platforms for forming bolt holes and key grooves) are prone to insufficient filling or cracking. Although increasing the hot pressing temperature and the die temperature can improve the fluidity and deformation ability of the material, too high temperature not only increases the engineering technical difficulty, but also reduces the service life of the shaping die. For example, for the lightweight and wear-resistant aluminum matrix powder metallurgy composite rail transit brake disc disclosed in CN111250698B, if its heat dissipation ribs and the convex platform structures for forming bolt holes and key grooves need to be fully filled without defects such as missing corners and cracks, its hot pressing and shaping temperature needs to be as high as 500°C - 600°C.

[0005] CN118437926A discloses a preparation method of a ceramic-reinforced aluminum matrix composite brake disc. By forming a frustum for forming a boss in the shaping stage and controlling the frustum to have the same height as the boss, and the volume of the frustum being 70% - 90% of the volume of the boss, the material deformation amount of forming the boss in the sizing stage can be effectively reduced. Thus, the heat dissipation ribs and the boss can be filled completely synchronously at 380°C - 400°C, and there are no cracks and missing corners. However, for the brake disc prepared by this method, there are obvious demoulding agent traces on the heat dissipation surface. This is because the frustum is directly formed to the height of the boss in this method. Although the axial material flow distance is reduced in the sizing stage, considering demoulding, the demoulding angle needs to be increased, resulting in the lateral flow of the material at the top of the frustum during the sizing process. The laterally flowing material flows upward along the mold side wall after contacting the mold side wall. At the same time, the material in other directions of the frustum flows downward along the mold side wall, and the two materials converge at a position near the bottom of the mold and are compacted under pressure. Since the material contains a high ceramic content, the frictional force between the material and the mold wall increases during the flow process, pushing the demoulding agent attached to the mold wall into the confluence of the two material flows and entering the material surface under pressure. Since this side of the brake disc is a non-machined surface, after shot peening the shaped blank, a black demoulding agent trace is left at the confluence of the material flows. If it needs to be removed, it can only be completed by manual grinding, which is time-consuming and laborious. 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 avoid the accumulation of demoulding agent.

[0007] A preparation method of a brake disc for rail transit vehicles, the brake disc for rail transit vehicles includes a heat dissipation layer and a friction layer. The heat dissipation layer includes a heat dissipation base arranged on the friction layer, heat dissipation ribs evenly distributed on the heat dissipation base, bosses arranged at the radial two ends of each heat dissipation rib, and frustums respectively used for forming bolt holes and key grooves. The preparation method of the brake disc for rail transit vehicles includes the following steps:

[0008] After the friction layer, the heat dissipation base, the heat dissipation ribs and part of the frustums are molded by pressing, sintered, and demolded, a sintered blank is obtained. The height of the part of the frustums is 70% - 85% of the overall height of the frustums, and the slope of the part of the frustums is 65% - 85% of the overall slope of the frustums;

[0009] The sintered blank is sized until the bosses and the remaining frustums are filled completely, and a brake disc for rail transit vehicles is obtained. The pressure of the sizing is 150 MPa - 250 MPa, the temperature is 350°C - 380°C, and the time is 10 - 30 seconds.

[0010] In one embodiment, the steps of molding the friction layer, the heat dissipation base, the heat dissipation ribs, and the partial frustum are specifically as follows:

[0011] Provide a molding die, the die cavity of which includes a first part for molding the heat dissipation ribs, a second part for molding the partial frustum, a third part for molding the heat dissipation base, and a fourth part for molding the friction layer;

[0012] Provide a first aluminum matrix composite and a second aluminum matrix composite. The mass content of ceramic particles in the first aluminum matrix composite is 10% - 20%, and the mass content of ceramic particles in the second aluminum matrix composite is 35% - 45%;

[0013] Fill the first aluminum matrix composite into the first part, the second part, and the third part of the die cavity respectively, scrape it flat, and pre-press it;

[0014] Fill the friction material into the fourth part of the die cavity and scrape it flat;

[0015] Close the die and press, then it's done.

[0016] In one embodiment, the pressure for closing the die and pressing is 100 MPa - 200 MPa, and the time is 5 - 15 seconds.

[0017] In one embodiment, the sintering is carried out in stages in a protective gas atmosphere: the sintering temperature in the first stage is 550 °C - 570 °C, and the time is 25 - 45 minutes; the sintering temperature in the second stage is 570 °C - 590 °C, and the time is 30 - 60 minutes; the sintering temperature in the third stage is 590 °C - 610 °C, and the time is 10 - 15 minutes.

[0018] In one embodiment, the thickness of the friction layer is 3 mm - 6 mm, and the thickness of the heat dissipation base is 20 mm - 25 mm.

[0019] In one embodiment, the overall height of the frustum is 20 mm - 26 mm, and the overall slope of the frustum is 60° - 75°.

[0020] In one embodiment, the height of the boss is 10 mm - 15 mm, and the slope of the boss is 60° - 75°.

[0021] In one embodiment, three frustums form a group, and there are six groups in total.

[0022] In one embodiment, after the boss and the remaining frustums are completely filled, the steps of machining bolt holes and key grooves at the corresponding frustums are further included.

[0023] In addition, the present application also provides a brake disc for rail transit vehicles prepared by any of the above methods. This brake disc has no demolding agent traces and meets the application requirements of brake discs for rail transit vehicles.

[0024] In the above method, by only forming a part of the frustum in the forming stage (70% - 85% of the overall height of the formed frustum and 65% - 85% of the overall slope), when subsequent shaping is carried out, the materials in the axial and circumferential directions can flow synchronously to fill the mold cavity, effectively avoiding the situation where the material flows in other directions after reaching the mold wall and rubbing against the mold wall, thereby involving and adhering to the demolding agent on the mold wall, resulting in the accumulation of the demolding agent.

[0025] In addition, by controlling the shaping pressure to be 150 MPa - 250 MPa, the temperature to be 350 °C - 380 °C, and the time to be 10 - 30 seconds, the bosses at both radial ends of the heat dissipation ribs can be quickly filled, avoiding the problem of the demolding agent being involved in the material. At the same time, it also avoids the formation of bosses in the forming stage, which may lead to difficult demolding and problems such as cracks after demolding. Description of the Drawings

[0026] Figure 1 It is a brake disc for rail transit vehicles of an embodiment. Detailed Embodiments

[0027] 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 content of the present invention more thorough and comprehensive.

[0028] It should be noted that when an element is referred to as being "disposed" on another element, it can be directly on the other element or there can also be an intermediate element.

[0029] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which the present invention belongs. The terms used in the description of the present invention in this specification are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0030] It should be noted that the brake disc for rail transit vehicles to be prepared in the present application is as Figure 1 shown, and includes a heat dissipation layer (not labeled in the figure) and a friction layer (not labeled in the figure), wherein the heat dissipation layer includes a heat dissipation base 12 disposed on the friction layer, heat dissipation ribs 14 uniformly distributed on the heat dissipation base 12, bosses 16 disposed at both radial ends of each heat dissipation rib 14, and frustums 18 respectively used to form bolt holes and key grooves.

[0031] Among them, the thickness of the friction layer is 3 mm to 6 mm. The thickness of the heat dissipation base 12 is 20 mm to 25 mm. The overall height of the frustum 18 is 20 mm to 26 mm, and the overall slope of the frustum 18 is 60° to 75°. The height of the boss 16 is 10 mm to 15 mm, and the slope of the boss 16 is 60° to 75°.

[0032] Further, three frustums 18 form a group, and there are six groups in total, which are evenly distributed along the heat dissipation base 12. The middle frustum in each group of frustums is used to form a keyway, and the frustums on both sides are respectively used to form bolt holes.

[0033] The preparation method of the brake disc for the rail transit vehicle described above includes the following steps S110 to S120:

[0034] S110. After the friction layer, the heat dissipation base 12, the heat dissipation ribs 14 and part of the frustums 18 are molded, sintered, and demolded, a sintered blank is obtained.

[0035] Among them, the height of part of the frustums 18 is 70% to 85% of the overall height of the frustum 18, and the slope of part of the frustums 18 is 65% to 85% of the overall slope of the frustum 18.

[0036] That is, in the forming stage, the friction layer 20, the heat dissipation base 12, and the heat dissipation ribs 14 are completely filled, but only part of the frustum 18 is formed, and only 70% to 85% of the overall height of the frustum 18 and 65% to 85% of the overall slope are formed. This is to facilitate demolding, and at the same time, during subsequent shaping, it will not cause the release agent to accumulate due to the material flowing to other directions after reaching the mold wall and rubbing against the mold wall and getting involved with the release agent attached to the mold wall.

[0037] It can be understood that the molding is carried out in a forming mold, and the mold cavity of this forming mold includes a first part for forming the heat dissipation ribs 14, a second part for forming part of the frustums 18, a third part for forming the heat dissipation base 12, and a fourth part for forming the friction layer.

[0038] Further, the first part, the second part, and the third part are filled with a first aluminum matrix composite material with a ceramic particle mass content of 10% to 20% to ensure sufficient structural strength while having good plasticity and thermal conductivity to facilitate the formation of the heat dissipation ribs. In addition, the boss 16 and the frustum 18 are prepared with the first aluminum matrix composite material. During the subsequent shaping stage, the material has good fluidity, which further avoids the problem of the release agent accumulating due to the material rubbing against the mold wall during the material flow process and getting involved with the release agent.

[0039] The fourth part is filled with a second aluminum matrix composite material with a ceramic particle mass content of 35% to 45% to ensure that the friction surface has good wear resistance and temperature resistance.

[0040] Meanwhile, the above two materials have similar expansion coefficients under the sintering conditions of this application. After metallurgical bonding, the interface is firmly bonded and not prone to cracking.

[0041] The specific operation steps are as follows:

[0042] Fill the above first aluminum matrix composite material into the first part, the second part, and the third part of the mold cavity respectively. After scraping flat, pre-press; fill the second aluminum matrix composite material into the fourth part of the mold cavity and scrape flat; then close the mold and press, and it's done.

[0043] Among them, the pressure for closing the mold and pressing is 100 MPa to 200 MPa, and the time is 5 to 15 seconds.

[0044] It should be noted that the sintering is carried out in stages in a protective gas atmosphere. Specifically, the sintering temperature in the first stage is 550 °C to 570 °C, and the time is 25 to 45 minutes to avoid cracking caused by too rapid heating; the sintering temperature in the second stage is 570 °C to 590 °C, and the time is 30 to 60 minutes to make the sintering densification; the sintering temperature in the third stage is 590 °C to 610 °C, and the time is 10 to 15 minutes to increase the surface temperature and avoid incomplete filling of the boss 16 due to temperature reduction during the subsequent shaping process.

[0045] Among them, the protective gas is an inert gas such as nitrogen or argon.

[0046] S120. Shape the above sintered blank until the filling of the boss 16 and the remaining frustum 18 is completed to obtain a brake disc for rail transit vehicles.

[0047] Among them, the pressure for shaping is 150 MPa to 250 MPa, the temperature is 350 °C to 380 °C, and the time is 10 to 15 minutes.

[0048] It should be noted that the boss 16 is filled by the material flow at both radial ends of the heat dissipation ribs 14, which avoids increasing the difficulty of demolding during the forming stage. At the same time, by controlling the height of the boss 16 to be 10 mm to 15 mm, the slope of the boss 16 to be 60° to 75°, and the pressure for shaping to be 150 MPa to 250 MPa, the temperature to be 350 °C to 380 °C, and the time to be 10 to 15 seconds, it can be ensured that even when the filling of the boss 16 is completed during the shaping stage, the material can avoid flowing in other directions after reaching the mold wall and rubbing against the mold wall and getting involved with the demolding agent attached to the mold wall, resulting in the problem of demolding agent accumulation.

[0049] The remaining part of the frustum 18 is also filled during the shaping stage, which can also avoid the difficulty of demoulding caused by complete shaping during the forming stage. At the same time, by forming only 70% - 85% of the overall height of the frustum 18 and 65% - 85% of the overall slope during the forming stage, when filling the remaining frustum 18 during the shaping stage, the materials in all directions can reach the die wall simultaneously, avoiding the problem that the materials flow in other directions after reaching the die wall and rubbing against the die wall to entangle and adhere to the release agent on the die wall, resulting in the accumulation of the release agent.

[0050] The following are specific embodiments.

[0051] Embodiment 1

[0052] Provide a first aluminum matrix composite with a ceramic particle mass content of 10% and a second aluminum matrix composite with a ceramic particle mass content of 35%. Using the method as in steps S110 - S120, form 70% of the overall height of the frustum and 65% of the overall slope during the forming stage.

[0053] The thickness of the friction layer of the brake disc is 3 mm, the thickness of the heat dissipation base is 20 mm, the overall height of the frustum is 20 mm, the overall slope of the frustum is 60°, the height of the boss is 10 mm, and the slope of the boss is 60°.

[0054] Observation shows that for the brake disc for rail transit vehicles prepared in Embodiment 1, demoulding is easy and there is no accumulation of release agent on the surface.

[0055] Comparative Example 1

[0056] Comparative Example 1 is basically the same as Embodiment 1, except that in Comparative Example 1, 100% of the overall height of the frustum and 65% of the overall slope are formed during the forming stage.

[0057] It is found that after sintering, demoulding is difficult, there are corners missing on the frustum, and there is an accumulation of release agent on the surface of the brake disc.

[0058] Comparative Example 2

[0059] Comparative Example 2 is basically the same as Embodiment 1, except that in Comparative Example 2, 70% of the overall height of the frustum and 100% of the overall slope are formed during the forming stage.

[0060] It is found that there is an accumulation of release agent at the position near the top of the frustum of the brake disc.

[0061] Comparative Example 3

[0062] Comparative Example 3 is basically the same as Embodiment 1, except that in Comparative Example 3, the shaping temperature is lower than 350 °C.

[0063] It is found that the boss is not completely filled.

[0064] Embodiment 2

[0065] Provide a first aluminum matrix composite with a ceramic particle mass content of 20% and a second aluminum matrix composite with a ceramic particle mass content of 45%, and adopt the method as in steps S110 - S120. In the forming stage, form 85% of the overall height of the frustum and 85% of the overall slope.

[0066] The thickness of the friction layer of the brake disc is 6 mm, the thickness of the heat dissipation base is 25 mm, the overall height of the frustum is 26 mm, the overall slope of the frustum is 75°, the height of the boss is 15 mm, and the slope of the boss is 75°.

[0067] Observation shows that for the brake disc for rail transit vehicles prepared in Example 2, demolding is easy and there is no accumulation of mold release agent on the surface.

[0068] Example 3

[0069] Provide a first aluminum matrix composite with a ceramic particle mass content of 15% and a second aluminum matrix composite with a ceramic particle mass content of 40%, and adopt the method as in steps S110 - S120. In the forming stage, form 80% of the overall height of the frustum and 80% of the overall slope.

[0070] The thickness of the friction layer of the brake disc is 5 mm, the thickness of the heat dissipation base is 22 mm, the overall height of the frustum is 22 mm, the overall slope of the frustum is 65°, the height of the boss is 12 mm, and the slope of the boss is 65°.

[0071] Observation shows that for the brake disc for rail transit vehicles prepared in Example 3, demolding is easy and there is no accumulation of mold release agent on the surface.

[0072] 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 patent of the present invention. 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 patent of the present invention should be subject to the appended claims.

Claims

1. A method for preparing a brake disc for a rail transit vehicle, wherein the brake disc for a rail transit vehicle comprises a heat dissipation layer and a friction layer, wherein the heat dissipation layer comprises a heat dissipation base arranged on the friction layer, heat dissipation ribs uniformly distributed on the heat dissipation base, bosses arranged at both radial ends of each heat dissipation rib, and truncated cones respectively used to form bolt holes and keyways, wherein: The method for preparing the brake disc for rail transit vehicles comprises the following steps: The friction layer, the heat dissipation base, the heat dissipation ribs and the partial truncated cone are molded, sintered and demolded to obtain a sintered blank, wherein the height of the partial truncated cone is 70% to 85% of the overall height of the truncated cone, and the slope of the partial truncated cone is 65% to 85% of the overall slope of the truncated cone; The sintered blank is shaped until the boss and the remaining truncated cone are filled to obtain a brake disc for rail transit vehicles. The shaping pressure is 150MPa-250MPa, the temperature is 350°C-380°C, and the time is 10-30 seconds.

2. The method for preparing a brake disc for a rail transit vehicle according to claim 1, characterized in that: The specific steps of molding the friction layer, the heat dissipation base, the heat dissipation ribs and part of the truncated cone are: Providing a forming mold, wherein the forming mold cavity includes a first portion for forming the heat dissipation rib, a second portion for forming the partial truncated cone, a third portion for forming the heat dissipation base, and a fourth portion for forming the friction layer; Providing a first aluminum-based composite material and a second aluminum-based composite material, wherein the mass content of ceramic particles in the first aluminum-based composite material is 10% to 20%, and the mass content of ceramic particles in the second aluminum-based composite material is 35% to 45%; Filling the first aluminum-based composite material into the first part, the second part and the third part of the mold cavity respectively, and pre-pressing after flattening; Filling the second aluminum-based composite material into the fourth part of the mold cavity and scraping it flat; Just close the mold and press.

3. The method for preparing a brake disc for a rail transit vehicle according to claim 2, characterized in that: The pressure of the mold closing pressing is 100MPa to 200MPa, and the time is 5 to 15 seconds.

4. The method for preparing a brake disc for a rail transit vehicle according to claim 1, characterized in that: The sintering is carried out in stages in a protective gas atmosphere: the sintering temperature of the first stage is 550°C to 570°C, and the time is 25 to 45 minutes; the sintering temperature of the second stage is 570°C to 590°C, and the time is 30 to 60 minutes; the sintering temperature of the third stage is 590°C to 610°C, and the time is 10 to 15 minutes.

5. The method for preparing a brake disc for a rail transit vehicle according to any one of claims 1 to 4, characterized in that: The thickness of the friction layer is 3 mm to 6 mm, and the thickness of the heat dissipation substrate is 20 mm to 25 mm.

6. The method for preparing a brake disc for a rail transit vehicle according to any one of claims 1 to 4, characterized in that: The overall height of the truncated cone is 20 mm to 26 mm, and the overall slope of the truncated cone is 60° to 75°.

7. The method for preparing a brake disc for a rail transit vehicle according to any one of claims 1 to 4, characterized in that: The height of the boss is 10 mm to 15 mm, and the slope of the boss is 60° to 75°.

8. The method for preparing a brake disc for a rail transit vehicle according to any one of claims 1 to 4, characterized in that: The three frustums form a group, and there are six groups in total.

9. The method for preparing a brake disc for a rail transit vehicle according to any one of claims 2 to 4, characterized in that: After the boss and the remaining truncated cone are completely filled, the method further includes the steps of machining bolt holes and keyways at the corresponding truncated cones.

Images