JP2006328474A - Method for manufacturing brake disc for railway vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a brake disc for railway vehicles in which a surface layer part 3 is made of aluminum-alloy matrix composite material and a main body part 2 is made of aluminum alloy and, further, the distribution of ceramics in the surface layer part 3 is practically uniformized and strength is maintained in the interface between the surface layer part 3 and the main body part 2. <P>SOLUTION: Particles or fibers of ceramics or both of them are compacted and sintered to form a ring-shaped preform 7. The preform 7 is set, in a preheated state, in the part near an upper end to be the surface layer part 3, inside a lower mold 10 constituting a mold 8. A molten aluminum alloy 13 is fed in a pressurized state into the mold 8, and the molten metal 13 is impregnated into the preform 7 under pressure. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  This invention is a brake disk for a railway vehicle that constitutes a braking device for a high-speed railway vehicle such as a Shinkansen.It is lightweight and has high toughness, and has excellent friction resistance, heat resistance, and crack resistance. The present invention relates to an improvement in a method for manufacturing a brake disk for a railway vehicle comprising a portion made of an aluminum alloy and a portion made of an aluminum alloy matrix composite material.

  High-speed railway vehicles such as Shinkansen usually use electric and mechanical braking devices, and disk brakes are often used as the mechanical type. In such a high-speed railway vehicle using a disc brake, when braking from a high speed, usually, an electric braking device is first activated, and after decelerating to a predetermined speed, the disc brake is activated to stop the vehicle. Let Further, when an emergency such as an earthquake occurs during traveling, the disc brake may operate even during high-speed traveling.

  As such a disc brake, it has been conventionally considered to use a wheel with an integrated brake disc formed by connecting a pair of brake discs on both sides of a railcar wheel. Such brake disc-equipped wheels include first mounting holes formed at a plurality of locations on the railcar wheel, and second portions formed at a plurality of locations that align with the first mounting holes at a portion of each brake disc. The bolts and nuts inserted into the mounting holes are screwed together and further tightened, whereby the railway vehicle wheel and the brake disk are integrally coupled.

  In the case of such a wheel with a brake disc, the temperature of each brake disc rises greatly due to heat generated by friction between each brake disc and the friction material accompanying braking. In addition, the operating time of the braking device for railway vehicles is long, and the amount of heat generated per unit time is large based on the friction between the friction material and the brake disk during operation. For this reason, a large stress (especially thermal stress) is generated in the brake disc.

  That is, as described in a copy of the objection determination of objection 2002-73163 and conventionally known, in the case of a disk brake for a railway vehicle, the frictional force (adhesive force) that is the upper limit of the braking force is the railway vehicle. Unlike the case of automobiles using rubber tires, the upper limit of this friction is remarkably reduced because it is determined by the friction between the wheels and the rails. For this reason, it is difficult to particularly increase the pressing pressure of the brake disc against the friction material. Also, in the case of a brake disc for a railway vehicle that assumes that a high speed of 240 km / h or more (in some cases 300 km / h) is used as the initial braking speed, a much lower speed than this is set as the initial braking speed. Unlike the case of automobiles, it takes a long time to stop, and it is necessary to be stable from high speed to low speed with a relatively low coefficient of friction. Therefore, in the case of a brake disc for a railway vehicle, it is required to have a friction performance different from that for an automobile. Further, the brake disk for railway vehicles has a remarkably large radial size as compared with the brake disk for automobiles. In the case of such a brake disc for a railway vehicle, a large stress (particularly thermal stress) is generated due to braking, coupled with a high load applied by braking from a high speed.

  In particular, in the case of a brake disc for a railway vehicle, when the speed of the railway vehicle becomes higher and the stress applied to the brake disc during braking becomes larger, the outer diameter side half that frictions with the friction material during braking significantly increases in temperature. On the other hand, the temperature rise in the inner half on the inner diameter side which is not in friction with the friction material and is in contact with the low-temperature railcar wheel is limited. As a result, a large temperature difference is generated between the inner diameter side and the outer diameter side of the brake disk, and the outer diameter side expands and pulls the inner diameter side. A large thermal stress is generated.

  On the other hand, in recent years, the speed of railway vehicles (mainly Shinkansen) has been increasing, and the demand for suppressing noise, ground vibration, and the like during travel has increased. As measures for meeting such demands, there are reductions in the weight of railway vehicles, particularly reduction in unsprung weight. In order to reduce such unsprung weight, it is effective to change the brake disk for railway vehicles from a conventional iron-based material to light aluminum or aluminum alloy. However, when the brake disk for a railway vehicle is composed only of aluminum or an aluminum alloy whose hardness is lower than that of an iron-based material, the wear resistance of the friction surface portion is reduced, so that it cannot withstand the use of a braking apparatus for a railway vehicle. .

  Under these circumstances, in recent years, it has been considered to improve the wear resistance of the friction surface part by making the brake disk for a railway vehicle made of an aluminum alloy-based composite material obtained by adding ceramics to an aluminum alloy. However, the aluminum alloy matrix composite material can dramatically increase the hardness as compared with the aluminum alloy, but the toughness, which is an advantage of the aluminum alloy, is greatly reduced.

  For example, in the case of a railway vehicle brake disc described in Patent Document 1, the entire brake disc is made of an Al-hyeutectic Si alloy containing 6 to 13% of Si and the particle size is 3 to 50 μm. SiC, which is a ceramic of the above, is made by uniformly dispersing and strengthening in the range of 5 to 30% by weight with respect to the matrix metal. However, in this way, in the case of a railway vehicle brake disk in which the entire brake disk for a railway vehicle is made of an aluminum alloy-based composite material including a low toughness material such as SiC, the toughness of the entire brake disk is reduced. Therefore, when braking is applied with a high load, the occurrence of a large stress causes an undesirable situation in terms of strength. Further, even when braking is applied with a high load, an unfavorable situation may occur.

  On the other hand, in the case of the brake disk for railway vehicles described in Patent Document 2, an Al—Si alloy containing 6 to 13% by weight of Si is used as a parent phase, and SiC having a particle size of 3 to 50 μm is used as a parent phase metal. On the other hand, the friction surface part which has been dispersed in the range of 5 to 30% by weight to improve the wear resistance and the heat radiating surface constituted only by the Al-Si alloy are integrated by welding. In the method of manufacturing a brake disk for a railway vehicle described in Patent Document 2, first, a molten metal A in which the SiC particles are dispersed in a molten metal of the Al-Si alloy, and Al-Si. First, the molten metal B consisting only of the molten metal of the alloy is prepared. First, the molten metal A is poured into the mold gate, and a molten layer having a desired thickness is formed in a portion to be a friction surface portion in the mold. While the molten metal A stays at the pouring gate, the molten metal B is injected, filled in the other part of the mold, and integrally liquid-phase joined to the upper surface of the molten layer. Made by casting process.

  According to such a brake disc for a railway vehicle described in Patent Document 2, the strength of the brake disk is preferable because of low toughness, which is a concern in the case of the brake disk for a rail vehicle described in Patent Document 1. It is possible to suppress the problem of causing a situation that does not occur to some extent. However, in the case of the brake disc described in Patent Document 2, it is manufactured by a casting process divided into two stages, and in the first casting process, the difference in specific gravity between SiC and aluminum alloy constituting the aluminum alloy matrix composite material. SiC with a high specific gravity may cause sedimentation. When this sedimentation occurs, the distribution of SiC at the friction surface portion of the railcar brake disk becomes non-uniform. In addition, oxide entrainment may occur at the interface between the part made of aluminum alloy matrix composite material made by casting first and the part made only by Al-Si alloy made by casting. When a turbulent flow is generated in the injection, there is a possibility that a sound interface between these two members cannot be obtained. For this reason, the strength decreases at this interface during braking, and there is a possibility that good braking performance cannot be obtained.

Further, in Patent Document 3, a member to be a base formed by forging or casting an aluminum alloy is placed in a mold, the mold is preheated, and a portion to be a friction surface portion is made of aluminum or an aluminum alloy. A manufacturing method of a brake disk for a railway vehicle is described which is produced by pouring a molten metal of a composite material in which ceramic particles or fibers are dispersed into the mold and integrally molding the molten metal. In the case of the manufacturing method of the brake disk for railway vehicles described in Patent Document 3 as described above, as in the case of the manufacturing method described in Patent Document 2, due to the difference in specific gravity between SiC and aluminum alloy at the time of casting, There is a possibility that SiC having a high specific gravity will settle. For this reason, there is a possibility that the distribution of SiC on the friction surface portion is non-uniform in the finished railcar brake disc. In particular, when the amount of SiC present on the surface portion of the friction surface portion is reduced, good wear resistance cannot be obtained. In addition, there is a possibility that an oxide is involved in the interface portion between the base portion and the friction surface portion at the time of casting in which the molten metal of the composite material is poured, or a sound interface cannot be obtained due to the turbulent flow at the time of casting. For this reason, also in the case of the manufacturing method described in Patent Document 3, the strength decreases at this interface during braking, and there is a possibility that good braking performance cannot be obtained.
As prior art documents related to the present invention, there are Patent Documents 4 to 6 in addition to Patent Documents 1 to 3.

Japanese Patent No. 3316831 JP 2001-287018 A Japanese Patent Laid-Open No. 10-89389 JP-A-5-279770 Japanese Patent Laid-Open No. 2002-5208 JP 2004-316829 A

  In view of such circumstances, the method for manufacturing a brake disk for a railway vehicle according to the present invention is a brake disk for a railway vehicle in which a surface layer portion having a friction surface is made of an aluminum alloy-based composite material and the other portion is made of an aluminum alloy. With this manufacturing method, the distribution of ceramics on the surface layer part can be made almost uniform, and the brake disk for railway vehicles that can maintain the strength at the interface between this surface layer part and other parts and obtain good braking performance should be realized. Invented.

The railcar brake disk manufacturing method of the present invention is made of an aluminum alloy-based composite material in which the surface layer portion having a friction surface for pressing the friction material on the side surface includes ceramic particles such as SiC and / or fibers. There is manufactured a brake disc for a railway vehicle that is fixed to a side surface of a wheel for a railway vehicle, in which portions other than the surface layer portion are made of an aluminum alloy such as an Al-Si-Mg alloy.
For this purpose, the method for manufacturing a brake disc for a railway vehicle according to the present invention comprises forming the preform by solidifying and firing the particles and / or the fibers, and forming the preform in the surface layer portion inside the mold. The molten aluminum alloy is placed in a portion to be formed and fed into the mold in a pressurized state, and the preform is press-impregnated with the molten metal.

  According to the method for manufacturing a brake disk for a railway vehicle of the present invention configured as described above, the brake for a railway vehicle has a light weight, high toughness, and excellent wear resistance, heat resistance, and crack resistance. You can get a disc. That is, since the brake disk obtained by the manufacturing method of the present invention comprises an aluminum alloy part and an aluminum alloy matrix composite part, the weight can be reduced sufficiently. Further, since the surface layer portion of the brake disk is made of an aluminum alloy matrix composite material containing ceramic particles and / or fibers, the wear resistance of the friction surface can be sufficiently increased. Moreover, since the parts other than the surface layer part of the brake disk are made of an aluminum alloy, the toughness of the entire brake disk can be sufficiently increased, has excellent heat resistance and crack resistance, and sufficiently secures strength. it can. Moreover, in the case of the present invention, the casting process is only required once, and the preformed body is impregnated with the aluminum alloy to form the surface layer portion, and the portions other than the surface layer portion are cast by aluminum alloy. Building is done continuously. For this reason, the oxide is not involved at the interface between the surface layer portion and the portion other than the surface layer portion, and the strength can be easily secured at this interface. For this reason, both these parts are firmly joined. Further, the distribution of ceramics in the surface layer can be made substantially uniform. As a result, it is possible to realize a railway vehicle brake disk having good braking performance.

Preferably, as described in claim 2, the ceramic is silicon carbide or alumina.
According to this preferable configuration, the hardness of the surface layer portion can be increased more effectively, and the wear resistance can be improved more effectively. For this reason, the lifetime of the brake disk for railway vehicles can be improved more effectively.

More preferably, as described in claim 3, the content of the ceramic particles and / or fibers in the surface layer portion is set to 25 to 40% in terms of volume.
According to this more preferable configuration, the hardness of the surface layer portion can be increased more effectively, and the wear resistance can be improved more effectively. For this reason, the lifetime of the brake disk for railway vehicles can be improved more effectively.

More preferably, as described in claim 4, after the preform is made by firing, the preform is preheated in the mold, and the surface layer is formed inside the mold. It arrange | positions in the beak part used as a part, and it produces by carrying out the pressure impregnation of the said molten metal to the said preform.
According to this more preferable configuration, it is possible to prevent a temperature drop immediately after the molten aluminum alloy is impregnated in a very small part of the preform. Therefore, it is possible to prevent only a part of the preform from being impregnated with the molten metal, and the preform can be substantially uniformly impregnated with the aluminum alloy. As a result, a good surface layer can be easily realized.

More preferably, as described in claim 5, the preform is preferably 3 to 10 mm (more preferably) from the position on the outermost side of the inner peripheral edge of the brake disc for a railway vehicle in the mold. 3 to 5 mm) It is arranged so that the inner peripheral edge of the preform is located at a position deviating to the outer diameter side.
According to this more preferable configuration, it is possible to prevent the presence of a surface layer portion made of an aluminum alloy matrix composite material having low toughness in a portion where thermal stress is likely to be excessive during braking, and the area of the portion that becomes the friction surface of the surface layer portion. Can be secured sufficiently. On the other hand, the inner periphery of the preform is set within a range of less than 3 mm from the position of the innermost peripheral edge of the brake disk for railway vehicles in the mold to the outermost diameter side. If it is arranged so as to be positioned, the thermal stress applied to the inner diameter side end of the railcar brake disk during braking becomes excessive, which is not preferable for ensuring the strength of the brake disk. Further, the preformed body is placed at a position outside the outer peripheral side of the inner peripheral edge of the railcar brake disk within the mold by a size more than 10 mm away from the outer diameter side. If the inner peripheral edge is disposed, it becomes extremely difficult to sufficiently secure the area of the portion that becomes the friction surface of the surface layer portion, that is, the area of the portion that becomes the sliding friction portion.

More preferably, as described in claim 6, the thickness of the preform is 6 to 20% of the maximum thickness of the finished brake disc for a railway vehicle.
According to this more preferable configuration, the preformed body can be easily handled (handled) during production, and the wear resistance of the brake disk can be more effectively ensured. Also, it is possible to more effectively distribute the molten aluminum alloy throughout the preform, and to effectively crush the preform when the preform is pressure impregnated with the molten aluminum alloy. In addition, it is possible to more effectively prevent the brake disc from lowering in strength during braking. On the other hand, when the thickness of the preform is less than 6% of the maximum thickness of the finished brake disc for a railway vehicle, the ease of use of the preform and the placement (setting) in the mold The ease of handling and the like are significantly reduced. Further, in this case, when used under severe conditions where high-load braking is repeated, the preform is completely worn, making it extremely difficult to ensure the wear resistance of the brake disk. In addition, when the thickness of the preform is set to exceed 20% of the maximum thickness of the finished brake disc for a railway vehicle, the molten aluminum alloy should be spread over the entire preform. However, it becomes extremely difficult. For this reason, when this preformed body is impregnated with a molten aluminum alloy under pressure, the possibility that the preformed body will be crushed becomes extremely high, resulting in a decrease in yield. That is, a state in which only the part of the preform is impregnated with the molten metal is likely to occur, and in this case, the preform is easily crushed when further impregnated with pressure. In this case, an unfavorable situation may occur due to the strength of the brake disc during braking.

  1 to 5 show an embodiment of the present invention. Among these drawings, FIGS. 1 to 4 show a brake disk 1 for a railway vehicle manufactured by the manufacturing method of the present embodiment, and FIG. 5 shows a manufacturing method of the brake disk 1. First, the brake disk 1 manufactured by the manufacturing method of this embodiment will be described. The brake disc 1 includes an aluminum alloy main body 2 and a surface layer portion made of an aluminum alloy matrix composite material in which aluminum alloy is used as a matrix material, and particles or fibers of ceramics such as SiC and alumina, or both of them are dispersed and blended. 3 and has a ring shape as a whole. The brake disc 1 is formed by integrally connecting the surface layer portion 3 to one surface of the main body portion 2. In the case of the present embodiment, the brake disk 1 has a half portion on the outer diameter side on one side (the front side in FIG. 1, the back side in FIG. 2, the left side in FIGS. 3 and 4, the upper side in FIG. 5 (d)). The friction surface 4 is used to press a friction material (not shown) during braking. The friction surface 4 is constituted by one surface of the surface layer portion 3. In contrast, the other side of the brake disc 1 (the back side in FIG. 1, the front side in FIG. 2, the right side in FIGS. 3 and 4, the bottom side in FIG. 5 (D)) In order to be able to be fixed to a side surface of a vehicle wheel (not shown), it is configured to be able to abut against this side surface without rattling. In FIG. 1, the surface layer portion 4 is represented by an oblique lattice portion.

  In the case of this embodiment, the other half of the outer surface of the brake disk 1 near the outer diameter has a shape in which convex portions and concave portions formed radially are alternately arranged in the circumferential direction. Yes. Thereby, in a state where the convex portion of the brake disc 1 hits the side surface of the railway vehicle wheel or is in close proximity, the other half of the outer surface of the brake disc 1 closer to the outer diameter and the side surface of the rail vehicle wheel A passage through which cooling air can flow is formed between the gaps (between the recess and the side surface).

  In addition, a plurality of notches 5 and 5 that open to the inner peripheral edge of the brake disk 1 are formed at equal intervals in the circumferential direction in the inner diameter side half of the brake disk 1. The cross-sectional shape of each of the cutouts 5 and 5 is a composite arc in which a plurality of arcs are continuous. Each of the notches 5 and 5 is formed at a position distant from the friction surface 4 toward the inner diameter side, and constitutes a part of the inner peripheral edge of the brake disc 1. In particular, in the case of the present embodiment, it is 3 to 10 mm (more preferably 3 mm) from the back end of each of the notches 5 and 5, which is the position on the outermost diameter side of the inner peripheral edge of the brake disc 1. ˜5 mm) The inner peripheral edge of the friction surface 4 is positioned at a position shifted to the outer diameter side. In other words, the inner peripheral edge of the surface layer portion 3 is present at a position shifted to the outer diameter side by 3 to 10 mm (more preferably 3 to 5 mm) from the back end of the notches 5 and 5. On the other hand, the outer peripheral edge of the friction surface 4 reaches the outer peripheral edge of the brake disc 1. Further, mounting holes 6 and 6 for inserting bolts for mounting the brake disc 1 to the railway vehicle wheel are provided between the notches 5 and 5 adjacent to each other in the circumferential direction. The tops (back ends) of the notches 5 and 5 are present outside the pitch circle of the mounting holes 6 and 6.

Moreover, in the case of a present Example, the content rate of the said ceramic particle | grains (or both in the case of carrying out dispersion | distribution mixing | blending of both fiber and particle | grains) in the said surface layer part 3 is 25-25 in volume conversion. 40%. Further, the thickness t ₃ (FIG. 4) of the surface layer portion 3 is set to 6 to 20% of the maximum thickness T ₁ (FIG. 4) of the entire brake disc 1 (0.06T ₁ ≦ t ₃ ≦ 0. 20T _1).

  In order to manufacture the brake disk 1 configured as described above, the following manufacturing method is used in this embodiment. This manufacturing method will be described with reference to FIG. In the case of the manufacturing method of the present embodiment, first, a preform 7 (preform) constituting the surface layer portion 3 is made. The preform 7 is formed into an annular shape as a whole by kneading ceramic particles such as SiC and alumina and / or fibers using an appropriate binder, solidifying and firing. FIG. 5 schematically shows the preform 7 made by firing and solidifying SiC particles and alumina fibers. In addition, the said preforming body 7 can also be made by baking after solidifying the said particle | grains and / or fiber, and stirring and mixing them into a predetermined shape with a press and drying them by a drying process.

Further, in the case where the ceramic particles (or fibers, or both fibers and particles) are dispersed and blended in the surface layer portion 3 ((D) of FIG. 5) in the finished product of the brake disc 1, both of them are mixed. )) In a volume conversion of 25 to 40%, in the case of dispersing and blending the ceramic particles (or fibers, or both fibers and particles) in the preform 7, The content of both (the ratio excluding voids inside the preform 7) is 25 to 40% in terms of volume. The thickness t ₇ of the preform 7 is set to 6 to 20% of the maximum thickness T ₁ of the finished product of the brake disc 1.

  And the preforming body 7 comprised as mentioned above is installed in the casting_mold | template 8 as shown in FIG. This mold 8 has an upper mold 9 and a lower mold 10 each of which is an upper and lower divided type and each has a ring shape. In a state where the upper mold 9 and the lower mold 10 are brought into contact with each other, a cavity 11 having a shape that substantially matches the outer surface of the finished product of the brake disk 1 is formed inside the mold 8. Further, on the inner diameter side of the mold 8, a gate (not shown) for injecting a molten aluminum alloy 13 (described later) into the cavity 11 under pressure is provided. Further, a plurality of small holes (not shown) each penetrating in the thickness direction are formed in at least a portion of the upper mold 9 facing the preform 7. And the said preform 7 is installed in the lower mold | type 10 which comprises such a casting_mold | template 8 so that the surface which should become the friction surface 4 is located in the upper end of the said lower mold | type 10. FIG. Although not shown, in order to place the preform 7 at a predetermined position in the mold 8, for example, a step surface is provided on the inner peripheral surface on the outer diameter side of the lower mold 10. The preform 7 can be installed on the top. However, in this case, after the brake disc 1 is completed, the outer peripheral portion of the surface layer portion 3 protrudes to the outer diameter side with respect to the other portions. Therefore, the protruding portion is scraped off as necessary. Further, in a state where the preformed body 7 is installed in the mold 8, the notches 5, 5 (FIGS. The inner peripheral edge 12 of the preformed body 7 is positioned at a position shifted by 3 to 10 mm (preferably 3 to 5 mm) on the outer diameter side from the position (point D in FIG. 5) that should be the back end of the reference. The amount by which the inner peripheral edge 12 of the preformed body 7 is shifted from the position to be the far end of the notches 5 and 5 in this way corresponds to the dimension L in FIG.

  The preform 7 is sufficiently preheated to a predetermined temperature in the range of 350 to 600 ° C., and in this state, the preform 7 is disposed in the mold 8 and on the portion to be the surface layer portion 3 inside the mold 8. To do. Then, as shown in FIG. 5 (b), the molten aluminum 13 of the aluminum alloy is fed into the mold 8 through the pouring gate in a pressurized state. As this aluminum alloy, for example, an Al—Si—Mg alloy is used. The pressure when the molten metal 13 is fed is set to a high pressure of 50 MPa or more (for example, 80 MPa). By feeding the molten metal 13 like this, the molten metal 13 is filled in the cavity 11 in the portion to be the main body 2 of the brake disc 1 and the preform 13 is pressure-impregnated with the molten metal 13. . When the preform 7 is pressure-impregnated with the molten metal 13, the air present in the voids in the preform 7 is discharged to the outside through the plurality of small holes. As the molten metal 13 is fed into the cavity 11, the air present in the cavity 11 is also discharged to the outside through the plurality of small holes. The cavity 11 is filled with the molten metal 13, and the molten metal 13 is pressure-impregnated in the gap in the preform 7, and after the temperature is lowered, the brake disk 1 is taken out from the mold 8; Finishing processing for adjusting the shape is performed as necessary to obtain a finished product of the brake disc 1 (FIGS. 1 to 4).

  Further, the preform 7 in which a part of the cavity 11 is arranged in the portion to be the friction surface 4 becomes the surface layer portion 3 made of an aluminum alloy matrix composite material by the above-described casting process. The toughness of the surface layer portion 3 is lower than the toughness of the main body portion 2 which is another portion. For this reason, the arrangement position of the preform 7 in the mold 8 needs to be considered in order to avoid a portion where a large stress is generated during use. In particular, during braking, the outer diameter side of the brake disc 1 expands and pulls the vicinity of the inner diameter side end portion, so that a large thermal stress is likely to occur near the inner diameter side end portion. For this reason, the surface layer portion 3 made of an aluminum alloy matrix composite material having small fracture toughness with respect to thermal stress is disposed avoiding the portion that should become the inner diameter side end portion of the brake disk 1 that tends to increase thermal stress during use. It is preferable to do. More specifically, the preformed body 7 is placed at the innermost edge of the brake disk 1 in the mold 8 at the outermost side of the plurality of notches 5 and 5 ( The inner peripheral edge 12 of the preformed body 7 is located at a position deviating to the outer diameter side of 3 to 10 mm (more preferably 3 to 5 mm) corresponding to the dimension L in FIG. It is preferable to arrange.

  As in the present embodiment, the apexes (back ends) of the notches 5 and 5 formed on the inner peripheral edge of the brake disc 1 exist outside the pitch circle of the bolt insertion holes 6 and 6. In this case, the portion where the tensile stress and strain based on thermal expansion are maximized becomes the apex portion of each of the notches 5 and 5. This is a conventionally known matter as described in Patent Document 6.

  According to the manufacturing method of the railway vehicle brake disk 1 of the present embodiment configured as described above, the railway vehicle is lightweight and has high toughness, and has excellent wear resistance, heat resistance, and crack resistance. Brake disc 1 can be obtained. That is, since the brake disc 1 obtained by the manufacturing method of the present embodiment is composed of the main body portion 2 made of aluminum alloy and the surface layer portion 3 made of aluminum alloy matrix composite material, a sufficient weight reduction can be achieved. Further, since the surface layer portion 3 of the brake disk 1 is made of an aluminum alloy-based composite material containing ceramic particles and / or fibers, the wear resistance of the friction surface 4 can be sufficiently increased. Moreover, since the main body part 2 other than the surface layer part 3 of the brake disk 1 is made of an aluminum alloy, the toughness of the entire brake disk 1 can be sufficiently increased, and has excellent heat resistance and crack resistance. Enough strength can be secured. Moreover, in the case of the present embodiment, the casting process is only required once, and the surface layer portion 3 is formed by impregnating the preform 7 with the aluminum alloy, and the main body portion 2 other than the surface layer portion 3 is formed. Making by casting aluminum alloy is performed continuously. For this reason, the oxide is not involved at the interface between the surface layer portion 3 and the main body portion 2, and the strength is easily maintained at this interface. For this reason, these both parts 3 and 2 are couple | bonded firmly. Further, the distribution of ceramics in the surface layer portion 3 can be made substantially uniform. As a result, it is possible to realize the brake disc 1 having good braking performance.

  In the case of the present embodiment, since the ceramic constituting the preform 7 is silicon carbide or alumina, the hardness of the surface layer portion 3 can be increased more effectively, and the wear resistance can be improved more effectively. I can do things. For this reason, the lifetime of the brake disc 1 can be improved more effectively. Further, when the ceramic particles and / or fibers in the surface layer portion 3 of the finished product of the brake disc 1 are dispersed and blended, the content of both is 25 to 40% in terms of volume. For this reason, the hardness of the surface layer part 3 can be increased more effectively, and the wear resistance can be improved more effectively. As a result, the life of the brake disc 1 can be improved more effectively.

  In the case of the present embodiment, after the preformed body 7 is made by firing, the preformed body 7 is preheated, and the preformed body 7 is heated to a predetermined value (for example, 400 ° C.) or higher. Is placed in the mold 8 on the inner portion of the mold 8 where the surface layer portion 3 is to be placed, and the preform 7 is press-impregnated with the molten metal 13. For this reason, it is possible to prevent a temperature drop immediately after the molten aluminum 13 of the aluminum alloy is impregnated into a very small part of the preform 7. Therefore, it is possible to prevent only a part of the preform 7 from being impregnated with the molten metal 13, and the preform 7 can be impregnated with the aluminum alloy substantially uniformly. As a result, a good surface layer 3 can be easily realized.

  Further, the preform 7 is positioned at the innermost peripheral edge of the brake disk 1 in the mold 8 to be the outermost end of each notch 5 (point D in FIG. 5). 3) to 3-10 mm (more preferably 3-5 mm) from the outer diameter side of the preform 7 so that the inner peripheral edge of the preform 7 is positioned. For this reason, it is possible to prevent the surface layer portion 3 made of an aluminum alloy matrix composite material having low toughness from existing in a portion where thermal stress is likely to be excessive during braking, and a sufficient area of the portion that becomes the friction surface 4 of the surface layer portion 3 is sufficient. Can be secured. On the other hand, the preformed body 7 is moved from the position to be the far end of the notches 5 and 5, which is the position on the outermost diameter side of the inner peripheral edge of the brake disk 1 in the mold 8. If the inner periphery of the preform 7 is positioned within a range of less than 3 mm on the outer diameter side, the thermal stress applied to the inner diameter side end of the brake disk 1 during braking becomes excessive, and the brake disk 1 is not preferable for securing the strength. Further, the preformed body 7 is placed at a position where it is disengaged to the outer diameter side by a predetermined length exceeding 10 mm from the position at which the notches 5 and 5 of the brake disk 1 are to be located in the mold 8. When the preform 7 is arranged so that the inner peripheral edge 12 is positioned, the radial length of the portion that becomes the friction surface 4 of the surface layer portion 3 is reduced, and the area of this portion, that is, the sliding friction portion is formed. It becomes extremely difficult to secure a sufficient area of the portion.

Further, in the case of the present embodiment, the thickness t ₇ (FIG. 5 (a)) of the preformed body 7 is determined based on the manufacturing quality limit of the preformed body 7, the stress generated in the brake disc 1, the braking force. Appropriately regulated in consideration of wear and other factors. Specifically, the thickness t ₇ of the preform 7 is set to 6 to 20% of the maximum thickness T ₁ (FIG. 4) of the finished product of the brake disc 1 (0.06T ₁ ≦ t ₇ ≦ 0.20T _1). For this reason, it is possible to easily handle (handle) the preformed body 7 at the time of manufacture, and to ensure the wear resistance of the brake disc 1 more effectively. Further, it is possible to more effectively perform the aluminum alloy melt 13 throughout the preform 7, and this preform when the preform 7 is pressure impregnated with the aluminum alloy melt 13. It is possible to effectively prevent the body 7 from being crushed and to more effectively prevent the brake disk 1 from being reduced in strength during braking. On the other hand, when the thickness t ₇ of the preform 7 is less than 6% of the maximum thickness T ₁ of the finished brake disc 1 (t ₇ <0.06T ₁ ), The handleability such as ease of use of the molded body 7 and ease of arrangement (setting) in the mold is significantly reduced. Further, in this case, when used under severe conditions where high-load braking is repeated, the preform 7 is completely worn out, and it is extremely difficult to ensure wear resistance. Further, when the thickness t ₇ of the preform 7 is set to exceed 20% of the maximum thickness T ₁ of the finished brake disc 1 (t ₇ > 0.20 T ₁ ), the preform It is extremely difficult to spread the molten aluminum 13 on the entire body 7. For this reason, the possibility that the preformed body 7 will be crushed when the preformed body 7 is impregnated with the molten aluminum alloy 13 is remarkably increased, and the yield is deteriorated. Also, in this case, an unfavorable situation may occur due to the strength of the brake disc 1 during braking.

Table 1 below summarizes the results of the study conducted by the inventor of the present invention in order to obtain the ratio of the preferred thickness t ₇ of the preform 7 to the maximum thickness T ₁ of the brake disc 1 in this embodiment. Shows what you did. Also from the examination results shown in Table 1, when the above ratio is regulated to an appropriate range (0.06T ₁ ≦ t ₇ ≦ 0.20T ₁ ), the pre-molded body 7 can be easily handled during production. In addition, the wear resistance of the brake disk 1 can be effectively ensured, and the preform 7 can be effectively prevented from being crushed when the preform 7 is impregnated with the molten aluminum alloy 13 under pressure. Further, from such a study result, if the maximum thickness T ₁ of the brake disc 1 was 49mm, the thickness t ₇ of the preform 7, for restricting the range of 2.9~9.8mm I understand that things are preferable.

  Next, the result of the strength test of the brake disc 1 performed by the inventor to confirm the effect of the present embodiment will be described. The strength test is a brake disc 1 having the same structure as that of the embodiment shown in FIGS. 1 to 5 described above, and an arc test having a cross section taken along a rectangle indicated by a one-dot chain line arrow honey in FIG. What cut out the piece 14 (FIG. 6) is used. Also, four types of test pieces 14 are used in which notches 17 are formed at any one of four positions shifted by 1 mm with respect to the axial direction (vertical direction in FIG. 6) of one side (right side in FIG. 6). To do. And as shown in FIG. 6, the interface position of the 1st part 15 which is a part of the main-body part 2 made from an aluminum alloy, and the 2nd part 16 which is a part of the surface layer part 3 made from an aluminum alloy matrix composite material is shown. When the reference (0 mm) is used, the minus (minus) side is the first portion 15, and the plus (plus) side is the second portion 16, both ends of one side of each test piece 14 are pushed into the fixed portion. At the same time, the load F is applied to the interface position on the other side. And the intensity | strength until a crack generate | occur | produces in the peripheral part of the notch 17 (or it breaks) was confirmed by four types of test pieces 14 which varied the formation position of the said notch 17.

  FIG. 7 shows the result of the strength test performed in this manner. As is apparent from the test results shown in FIG. 7, in the case of the present embodiment, the strength of the brake disk 1 is increased in the main body portion 2 made of aluminum alloy, and the surface layer portion 3 made of aluminum alloy matrix composite material. It is low. In addition, according to the present embodiment, there is almost no difference in strength between the interface position between the main body 2 and the surface layer 3 and the surface layer 3, in other words, the surface layer 3 is formed on the main body 2. I also found it difficult to peel off. That is, as a method for manufacturing a brake disk in which an aluminum or aluminum alloy part and an aluminum alloy matrix composite part are integrally joined, the above-described Patent Documents 2, 3 The manufacturing method described in 1 is known. Among these, the manufacturing method described in Patent Document 2 is performed by dividing the casting process into two stages, and the manufacturing method described in Patent Document 3 is a base made of aluminum alloy made by forging or casting. A brake disk is manufactured by placing a power member in a mold and pouring molten metal of a composite material in which ceramic particles or fibers are dispersed in aluminum or an aluminum alloy into a portion to be a friction surface portion. Even when the brake disc is manufactured by any of the manufacturing methods described in Patent Documents 2 and 3, the separation is more at the interface between the main body (base) and the surface layer (friction surface) than in the present embodiment. It is likely to occur. For example, as indicated by a one-dot chain line a in FIG. 7, the strength when a notch is formed at this interface is significantly reduced as compared with the case where a notch is formed at another position. On the other hand, in the case of the present embodiment, since the coupling between the main body 2 and the surface layer 3 can be strengthened, even when the notch 17 is formed at the interface position, the notch 17 is formed at another position. The strength is not significantly reduced compared to the case (particularly when the notch 17 is formed in the middle portion of the aluminum alloy matrix composite material). Thereby, the effect of the present Example was confirmed.

The figure which shows the half part of the brake disc manufactured by the Example of this invention. The figure which shows the half part seen from the back side of FIG. FIG. 2 is a cross-sectional view taken along the line AOB in FIG. The C section expanded sectional view of FIG. Sectional drawing which shows typically the casting process in the manufacturing method of an Example. Sectional drawing of the test piece used for the strength test done in order to confirm the effect of an Example. The diagram which similarly shows the result of an intensity | strength test by the relationship between the position of the notch formed in a test piece, and intensity | strength.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Brake disc 2 Main body part 3 Surface layer part 4 Friction surface 5 Notch 6 Mounting hole 7 Preliminary molding 8 Mold 9 Upper mold 10 Lower mold 11 Cavity 12 Inner peripheral edge 13 Molten metal 14 Test piece 15 First part 16 Second part 17 Notch

Claims (6)

The surface layer portion having a friction surface for pressing the friction material on the side surface is made of an aluminum alloy-based composite material containing ceramic particles and / or fibers, and the portion other than the surface layer portion is made of an aluminum alloy. A method for manufacturing a brake disc for a railway vehicle fixed to a side surface of a vehicle wheel,
The particles and / or fibers are hardened and fired to prepare a preform, and this preform is placed on the inside of the mold in the portion to be the surface layer, and a molten aluminum alloy is placed in the mold. A method for producing a brake disk for a railway vehicle, which is produced by feeding in a pressurized state and impregnating the preform with the molten metal under pressure.   The method for manufacturing a brake disk for a railway vehicle according to claim 1, wherein the ceramic is silicon carbide or alumina.   The manufacturing method of the brake disk for railcars of Claim 1 or Claim 2 which makes content rate of the said ceramic particle | grains and / or fiber in a surface layer part into 25 to 40% in volume conversion.   After the preform is made by firing, the preform is preheated and placed in the mold, on the inner surface of the mold, on the beveled portion, and the preform is placed on the preform. The manufacturing method of the brake disk for rail vehicles described in any one of Claims 1-3 manufactured by press-impregnating the said molten metal.   The inner periphery of the preform is located at a position 3 to 10 mm outside the position of the outermost side of the inner periphery of the brake disc for a railway vehicle in the mold. The manufacturing method of the brake disk for rail vehicles described in any one of Claims 1-4 arrange | positioned like this.   The method for manufacturing a brake disk for a railway vehicle according to any one of claims 1 to 5, wherein a thickness of the preform is 6 to 20% of a maximum thickness of a finished brake disk for a railway vehicle. .

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