Machining method for track brake disc

Abstract

The invention relates to the technical field of machining of track brake discs, and discloses a machining method for a track brake disc, which comprises the following steps: designing a brake disc model, and designing a mold model for sand mold casting; according to the mold model, an upper mold and a lower mold for sand mold casting are manufactured; molding sand is manufactured, and a sand box is designed; casting is completed through a mold, molding sand and a sand box, and a sand mold is formed; designing a brake disc sand core model, and manufacturing core sand and a sand core; a loosening detection area of the sand mold is obtained, detection is completed, and qualified sand molds are screened; combining the qualified sand mold and the sand core to form a pouring mold; metal is smelted and detected, and qualified molten metal is screened and then poured; taking out the casting rough blank after natural cooling, and cleaning to form a casting; and the casting is subjected to heat treatment and turning, and finally quality detection is conducted. The casting quality of the brake disc can be effectively improved by performing looseness detection on the sand mold, it is ensured that a casting mold does not displace or collapse when molten metal is poured, and the structural integrity of a casting is guaranteed.

Description

Technical Field

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

[0002] With the rapid development of the automobile industry, the reliability and safety of vehicle braking systems have attracted much attention. As a key component in the braking system, the performance of the brake disc directly affects the braking effect and driving safety of the vehicle. Therefore, higher and higher requirements are placed on the manufacturing process of the brake disc. The most common method for processing brake discs is generally casting.

[0003] In the prior art, the casting process of brake discs is mainly divided into two types: sand casting and metal mold casting. Sand casting refers to a method of pouring molten metal into a mold made of molding sand and forming a casting after the metal cools. The advantages of this method are that the cost is relatively low and complex shapes can be cast, which is suitable for small and medium batch production. However, in the sand casting process, the looseness of the sand mold will directly affect the quality of the final casting. In the actual casting process, if the sand mold is loose, it is easy to cause defects such as pores and sand inclusions in the casting, thereby affecting the performance and service life of the brake disc.

[0004] In the existing brake disc sand casting process, there is often a lack of accurate detection means for the loose area of ​​the sand mold, resulting in a low pass rate of the sand mold. For this reason, this method proposes a brake disc processing method. During the processing, the sand mold is detected for looseness to reduce the problems of defects such as pores and sand inclusions in the casting caused by loose sand molds. Summary of the invention

[0005] The present invention provides a method for processing a rail brake disc, which helps solve the problems mentioned in the above background technology.

[0006] The present invention provides the following technical solution: a method for processing a rail brake disc, comprising: Design brake disc model; Design the mold model for sand casting according to the brake disc model; According to the mold model, an upper mold for a brake disc and a lower mold for a brake disc for sand casting are manufactured; Making molding sand; Design and manufacture sand boxes for sand casting according to the brake disc upper mold and brake disc lower mold; The casting is completed by using the brake disc mold, molding sand and sand box to form a sand mold; Design the brake disc sand core model according to the brake disc model; Making core sand, and using the core sand to make a brake disc sand core according to a brake disc sand core model; Obtain loose detection area on the sand mold; Complete looseness detection on the looseness detection area on the sand mold, and classify the sand mold into qualified sand mold and defective sand mold according to the detection results; Combine qualified sand molds and brake disc sand cores into a casting mold; Melting metal to form metal pouring liquid, testing the composition of the metal pouring liquid, and screening and testing qualified metal pouring liquid; Pour qualified metal pouring liquid into the pouring mold, and after the pouring is completed, allow the pouring mold to cool naturally; After cooling is completed, the casting mold is disassembled and the rough blank of the brake disc casting is taken out; Cleaning the brake disc casting rough blank to form the brake disc casting; heat treating the brake disc casting to form a heat-treated casting; Use CNC machine tools to turn heat-treated castings to form brake disc components; Carry out quality inspection on the original brake discs and select qualified ones.

[0007] Optionally, the step of making a brake disc upper mold and a brake disc lower mold for sand casting according to the mold model comprises: The mold model is segmented along a horizontal plane to obtain an upper mold model and a lower mold model; According to the upper mold model and the lower mold model, a brake disc upper mold and a brake disc lower mold made of metal are turned out by using a CNC machine tool.

[0008] Optionally, the making of molding sand includes: Molding sand is obtained by mixing quartz sand, clay and water; The method of designing and manufacturing a sand box for sand casting according to the brake disc mold includes: Obtain the horizontal section with the largest area among all horizontal sections of the upper mold of the brake disc and the lower mold of the brake disc, and record them as the upper mold section and the lower mold section; According to the size of the upper mold cross section, a circle that completely covers the upper mold cross section and has the smallest area is obtained, and the circle is recorded as the upper circle; According to the size of the lower mold cross section, a circle that completely covers the lower mold cross section and has the smallest area is obtained, and the circle is recorded as the lower circle; Compare the areas of the upper circle and the lower circle, and select the one with the larger area as the reference circle; According to the area of ​​the reference circle, a square is obtained which completely covers the reference circle and the minimum distance between the four sides and the reference circle is equal to one quarter of the diameter of the reference circle, and the square is recorded as the reference square; Four metal plates are used to enclose a sand box, which has two openings at opposite positions. The surface of one opening is recorded as the upper surface of the sand box, and the surface of the other opening is recorded as the lower surface of the sand box; The top and bottom of the sand box are the same as the reference square, and the area occupied by the sand box can completely contain the upper mold and the lower mold of the brake disc.

[0009] Optionally, the method of completing the casting to form a sand mold by using a brake disc mold, molding sand, and a sand box includes: Place the sand box on a level surface; Place the brake disc upper mold in the center of the sand box; Fill the sand box with molding sand and completely cover the brake disc upper mold; Apply pressure to the molding sand in the sand box to make it compact and fit the mold on the brake disc. Clean the molding sand to make it flush with the top of the sand box. The upper mold of the brake disc is taken out from the sand box to obtain an upper sand mold; Take another sand box and place it on a horizontal surface; Place the brake disc lower mold in the center of the sand box; Fill the sand box with molding sand until it completely covers the brake disc lower mold; Apply pressure to the molding sand in the sand box to make it compact and fit the lower mold of the brake disc. Clean the molding sand to make it flush with the top of the sand box. The brake disc lower mold is taken out from the sand box to obtain a lower sand mold.

[0010] Optionally, obtaining a loose detection area on the sand mold includes: Obtain three-dimensional models of the upper sand mold and the lower sand mold respectively, and record them as the upper model and the lower model respectively; Obtain the horizontal planes that coincide with the upper and lower surfaces of the upper model respectively, and record them as the upper surface and the lower surface of the upper model; Obtain the horizontal planes that coincide with the upper and lower surfaces of the lower model respectively, and record them as the upper surface and the lower surface of the lower model; Set the progressive interval; For the upper model and the lower model, use a plane parallel to the upper and lower surfaces of the upper model and a plane parallel to the upper and lower surfaces of the lower model respectively, starting from the upper surface, in the direction from the upper surface to the lower surface, and intercept the upper model and the lower model at every progressive interval; The planes used that are parallel to the upper and lower surfaces of the upper model and the planes that are parallel to the upper and lower surfaces of the lower model are recorded as cross sections; After the upper model and the lower model are intercepted each time, the projections of the upper mold and the lower mold on the cross section are obtained respectively in the direction from the upper surface to the lower surface; After each interception of the upper model and the lower model, respectively obtain the distance between the cross section and the lower surface of the upper model or the lower model, and stop intercepting the upper model or the lower model when the distance is less than the progressive interval; For each independent projection on the cross section, obtain the edge contour of the projection; For each independent projection, obtain the centroid of the projection figure, and select any point on the edge contour line of the projection, connect the centroid of the projection figure with the edge contour line of the projection, and obtain the length of the connection line, which is recorded as the contour distance of the independent projection; For each independent projection, obtain the shortest contour distance of the independent projection; Set distance threshold; Compare the shortest contour distance of each independent projection to a distance threshold; The independent projection whose shortest contour distance is less than the distance threshold is marked, and the portion corresponding to the independent projection on the upper model or the lower model is obtained as the loose detection area.

[0011] Optionally, the performing looseness detection on the looseness detection area on the sand mold and classifying the sand mold into qualified sand mold and defective sand mold according to the detection result includes: For each looseness detection area, an image of the looseness detection area is collected before the looseness detection, and recorded as an initial image; Apply pressure to the loose detection area in a direction parallel to the upper and lower surfaces of the sand mold and pointing to the loose detection area; After applying pressure to the loose detection area, an image of the loose detection area is collected again and recorded as a comparison image; The comparison image is compared with the initial image to determine whether the looseness detection area is loosened after pressure is applied; If a loose detection area on the sand mold is loose, the sand mold is classified as a defective sand mold; If all loose detection areas on the sand mold are not loose, the sand mold is classified as a qualified sand mold.

[0012] Optionally, the step of cleaning the brake disc casting blank to form the brake disc casting includes: Clean the molding sand and burrs attached to the surface of the brake disc casting rough blank; The runner and riser portions existing on the brake disc casting blank are partially removed using a cutting tool.

[0013] Optionally, the quality inspection of the brake disc original parts to select qualified brake discs includes: Use ultrasonic waves to perform nondestructive testing on the original brake disc to check whether there are pores and cracks inside the original brake disc; Check the flatness of the brake disc surface; The original brake discs with no pores and cracks inside and a smooth surface are classified as qualified brake discs.

[0014] The present invention has the following beneficial effects: 1. By designing the size and shape of the sand box according to the upper mold and the lower mold of the brake disc, it is ensured that the designed sand box can completely wrap all parts of the mold and provide enough space for pouring molten metal, thereby reducing problems such as sand leakage and deformation that may occur during the casting process. To a certain extent, it can improve casting accuracy, reduce material waste, and improve production efficiency.

[0015] 2. By obtaining the center of gravity of the projection, and connecting the center of gravity of the projection figure with the edge contour line of the projection, the length of the connecting line is recorded as the contour distance of the projection, and all contour distances on the projection are compared to screen out the shortest contour distance. The shortest contour distance represents the area on the projection that is most likely to loosen. By comparing the shortest contour area with the set distance threshold, it can be determined whether the position corresponding to the projection on the sand mold has the possibility of loosening.

[0016] 3. By intercepting the upper model and the lower model, and obtaining the projection of the upper model and the lower model on the cross section, according to the analysis of the projection, the shortest contour distance to the projection is selected, and compared with the set distance threshold, the area on the sand mold that is most likely to loosen is screened out, so as to facilitate the subsequent corresponding looseness detection of this part of the area, and then the sand mold is detected with the least detection area to see if there is any looseness, which reduces the detection time and ensures the credibility of the looseness detection.

[0017] 4. By collecting and comparing images before and after looseness detection, image recognition technology can accurately detect whether there is a difference between the two images, and then detect the slight looseness in the looseness detection area, making the detection result more accurate, thereby improving the manufacturing quality of the final brake disc.

[0018] 5. The casting quality of the brake disc can be effectively improved by performing loose detection on the sand mold. During the casting process, loose sand molds may cause defects such as pores, cracks or deformation on the surface of the casting. Loose detection can detect these potential problems in advance, ensuring that the mold will not shift or collapse when pouring molten metal, thereby ensuring the structural integrity of the casting. Secondly, loose detection can detect and correct defective sand molds in a timely manner, which can avoid rework and waste disposal in subsequent processes and reduce production line downtime and resource waste. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of the upper mold of the brake disc of the present invention.

[0020] Figure 2It is a schematic diagram of the lower mold of the brake disc of the present invention.

[0021] Figure 3 It is a schematic diagram of the sand mold of the present invention.

[0022] Figure 4 It is a schematic diagram of the lower sand mold of the present invention.

[0023] Figure 5 It is a projection schematic diagram of the present invention. DETAILED DESCRIPTION

[0024] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] Embodiment 1, a method for processing a rail brake disc, comprising: Design a brake disc model; the designed brake disc model refers to a three-dimensional image model of the designed brake disc; According to the brake disc model, a mold model for sand casting is designed; the mold model for sand casting refers to a three-dimensional image model of the mold; According to the mold model, an upper mold for a brake disc and a lower mold for a brake disc for sand casting are manufactured; Making molding sand; Design and manufacture sand boxes for sand casting according to the brake disc upper mold and brake disc lower mold; The casting is completed by using the brake disc mold, molding sand and sand box to form a sand mold; Design the brake disc sand core model according to the brake disc model; Making core sand, and using the core sand to make a brake disc sand core according to the brake disc sand core model; the making of core sand and the making of brake disc sand core are prior arts, and will not be described in detail here; Obtain loose detection area on the sand mold; The loose detection area on the sand mold is tested for looseness, and the sand mold is divided into qualified sand molds and defective sand molds according to the test results. The casting quality of the brake disc can be effectively improved by performing loose detection on the sand mold. During the casting process, loose sand molds may cause defects such as pores, cracks or deformation on the surface of the casting. These potential problems can be discovered in advance through loose detection, ensuring that the mold will not shift or collapse when pouring molten metal, thereby ensuring the structural integrity of the casting. Secondly, loose detection can detect and correct defective sand molds in a timely manner, which can avoid rework and waste disposal in subsequent processes, and reduce production line downtime and resource waste.

[0026] Combine qualified sand molds and brake disc sand cores into a casting mold; Melting metal to form metal pouring liquid, testing the metal pouring liquid for components, and screening qualified metal pouring liquid; the above-mentioned testing the metal pouring liquid for components is a prior art and will not be described in detail here; Pour qualified metal pouring liquid into the pouring mold, and after the pouring is completed, allow the pouring mold to cool naturally; After cooling is completed, the casting mold is disassembled and the rough blank of the brake disc casting is taken out; Cleaning the brake disc casting rough blank to form the brake disc casting; The brake disc casting is heat treated to form a heat-treated casting; the heat treatment of the brake disc casting is a prior art and will not be described in detail here; Use CNC machine tools to turn heat-treated castings to form brake disc components; Carry out quality inspection on the original brake discs and select qualified ones.

[0027] The method of manufacturing a brake disc upper mold and a brake disc lower mold for sand casting according to the mold model comprises: The mold model is segmented along a horizontal plane to obtain an upper mold model and a lower mold model; According to the upper mold model and the lower mold model, the brake disc upper mold and the brake disc lower mold made of metal are turned out by using a CNC machine tool, such as Figure 1 and Figure 2 shown.

[0028] The method for making molding sand comprises: Molding sand is obtained by mixing quartz sand, clay and water; The method of designing and manufacturing a sand box for sand casting according to the brake disc mold includes: Obtain the horizontal section with the largest area among all horizontal sections of the upper mold of the brake disc and the lower mold of the brake disc, and record them as the upper mold section and the lower mold section; According to the size of the upper mold cross section, a circle that completely covers the upper mold cross section and has the smallest area is obtained, and the circle is recorded as the upper circle; According to the size of the lower mold cross section, a circle that completely covers the lower mold cross section and has the smallest area is obtained, and the circle is recorded as the lower circle; Compare the areas of the upper circle and the lower circle, and select the one with the larger area as the reference circle; According to the area of ​​the reference circle, a square is obtained which completely covers the reference circle and the minimum distance between the four sides and the reference circle is equal to one quarter of the diameter of the reference circle, and the square is recorded as the reference square; Four metal plates are used to enclose a sand box, which has two openings at opposite positions. The surface of one opening is recorded as the upper surface of the sand box, and the surface of the other opening is recorded as the lower surface of the sand box; Among them, the top and bottom of the sand box are the same as the reference square, and the area occupied by the sand box can completely contain the brake disc upper mold and the brake disc lower mold; by designing the size and shape of the sand box according to the brake disc upper mold and the brake disc lower mold, it is ensured that the designed sand box can completely wrap all parts of the mold and provide sufficient space for pouring molten metal, thereby reducing problems such as sand leakage and deformation that may occur in the casting process, which can improve the casting accuracy, reduce material waste and improve production efficiency to a certain extent.

[0029] The method of completing the casting by using the brake disc mold, the molding sand and the sand box to form the sand mold includes: Place the sand box on a level surface; Place the brake disc upper mold in the center of the sand box; Fill the sand box with molding sand and completely cover the brake disc upper mold; Apply pressure to the molding sand in the sand box to make it compact and fit the mold on the brake disc. Clean the molding sand to make it flush with the top of the sand box. Take the brake disc upper mold out of the sand box to get the upper sand mold, the basic shape is as follows Figure 3 As shown; Take another sand box and place it on a horizontal surface; Place the brake disc lower mold in the center of the sand box; Fill the sand box with molding sand until it completely covers the brake disc lower mold; Apply pressure to the molding sand in the sand box to make it compact and fit the lower mold of the brake disc. Clean the molding sand to make it flush with the top of the sand box. Take the brake disc lower mold out of the sand box to get the lower sand mold. The basic shape is as follows: Figure 4 shown.

[0030] The step of obtaining a loose detection area on a sand mold includes: Obtain three-dimensional models of the upper sand mold and the lower sand mold respectively, and record them as the upper model and the lower model respectively; Obtain the horizontal planes that coincide with the upper and lower surfaces of the upper model respectively, and record them as the upper surface and the lower surface of the upper model; Obtain the horizontal planes that coincide with the upper and lower surfaces of the lower model respectively, and record them as the upper surface and the lower surface of the lower model; Setting the progressive interval; the progressive interval is the distance between the current interception position and the previous interception position when intercepting the upper model and the lower model, which can be set according to the height of the upper model and the lower model; For the upper model and the lower model, use a plane parallel to the upper and lower surfaces of the upper model and a plane parallel to the upper and lower surfaces of the lower model respectively, starting from the upper surface, in the direction from the upper surface to the lower surface, and intercept the upper model and the lower model at every progressive interval; The planes used that are parallel to the upper and lower surfaces of the upper model and the planes that are parallel to the upper and lower surfaces of the lower model are recorded as cross sections; Reference Figure 5 , after intercepting the upper model and the lower model each time, the projections of the upper mold and the lower mold on the cross section are obtained respectively in the direction from the upper surface to the lower surface; After each interception of the upper model and the lower model, respectively obtain the distance between the cross section and the lower surface of the upper model or the lower model, and stop intercepting the upper model or the lower model when the distance is less than the progressive interval; For each independent projection on the cross section, obtain the edge contour of the projection; For each independent projection, obtain the centroid of the projection figure, and select any point on the edge contour line of the projection, connect the centroid of the projection figure with the edge contour line of the projection, and obtain the length of the connection line, which is recorded as the contour distance of the independent projection; For each independent projection, the shortest contour distance of the independent projection is obtained; by obtaining the center of gravity of the projection and connecting the center of gravity of the projection figure with the edge contour line of the projection, the length of the connecting line is recorded as the contour distance of the projection, and all contour distances on the projection are compared to screen out the shortest contour distance. The shortest contour distance represents the area on the projection that is most likely to loosen. By comparing the shortest contour area with the set distance threshold, it can be determined whether the position corresponding to the projection on the sand mold has the possibility of loosening.

[0031] Set a distance threshold; the distance threshold is a comparison standard for selecting a loose detection area, and the area most likely to loosen is screened out by comparing with the distance threshold; Compare the shortest contour distance of each independent projection to a distance threshold; The independent projection whose shortest contour distance is less than the distance threshold is marked, and the corresponding part of the independent projection on the upper model or the lower model is obtained as the loose detection area; by intercepting the upper model and the lower model, and obtaining the projection of the upper model and the lower model on the cross section, according to the analysis of the projection, the shortest contour distance to the projection is selected, and compared with the set distance threshold, the area on the sand mold most likely to loosen is screened out, so as to facilitate the subsequent corresponding looseness detection of this part of the area, and then the sand mold is detected with the least detection area to see if there is looseness, which reduces the detection time and ensures the credibility of the looseness detection.

[0032] The looseness detection is performed on the looseness detection area on the sand mold, and the sand mold is divided into a qualified sand mold and a defective sand mold according to the detection result, including: For each looseness detection area, an image of the looseness detection area is collected before the looseness detection, and recorded as an initial image; Apply pressure to the loose detection area in a direction parallel to the upper and lower surfaces of the sand mold and pointing to the loose detection area; After applying pressure to the loose detection area, an image of the loose detection area is collected again and recorded as a comparison image; The comparison image is compared with the initial image to determine whether the loose detection area is loose after pressure is applied; the comparison of the comparison image with the initial image to determine whether the loose detection area is loose is an image recognition technology, and whether there is looseness is determined based on whether there is a difference between the two images. This image recognition technology is a prior art; by collecting the image before the loose detection and the image after the loose detection and comparing them, the image recognition technology can accurately detect whether there is a difference between the two images, and then detect the slight looseness in the loose detection area, so that the detection result is more accurate, thereby improving the manufacturing quality of the final brake disc.

[0033] If a loose detection area on the sand mold is loose, the sand mold is classified as a defective sand mold; If all loose detection areas on the sand mold are not loose, the sand mold is classified as a qualified sand mold.

[0034] The method of cleaning the brake disc casting blank to form the brake disc casting comprises: Clean the molding sand and burrs attached to the surface of the brake disc casting rough blank; The runner and riser portions existing on the brake disc casting blank are partially removed using a cutting tool.

[0035] The quality inspection of the brake disc original parts to select qualified brake discs includes: Use ultrasonic waves to perform nondestructive testing on the original brake disc to check whether there are pores and cracks inside the original brake disc; Perform a flatness test on the surface of the brake disc; the non-destructive test and flatness test are prior arts and will not be described in detail here; The original brake discs with no pores and cracks inside and a smooth surface are classified as qualified brake discs.

[0036] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0037] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for processing a rail brake disc, characterized in that: include: Design brake disc model; Design the mold model for sand casting according to the brake disc model; According to the mold model, an upper mold for a brake disc and a lower mold for a brake disc for sand casting are manufactured; Making molding sand; Design and manufacture sand boxes for sand casting according to the brake disc upper mold and brake disc lower mold; The casting is completed by using the brake disc mold, molding sand and sand box to form a sand mold; Design the brake disc sand core model according to the brake disc model; Making core sand, and using the core sand to make a brake disc sand core according to a brake disc sand core model; Obtain loose detection area on the sand mold; Complete looseness detection on the looseness detection area on the sand mold, and classify the sand mold into qualified sand mold and defective sand mold according to the detection results; Combine qualified sand molds and brake disc sand cores into a casting mold; Melting metal to form metal pouring liquid, testing the composition of the metal pouring liquid, and screening and testing qualified metal pouring liquid; Pour qualified metal pouring liquid into the pouring mold, and after the pouring is completed, allow the pouring mold to cool naturally; After cooling is completed, the casting mold is disassembled and the rough blank of the brake disc casting is taken out; Cleaning the brake disc casting rough blank to form the brake disc casting; heat treating the brake disc casting to form a heat-treated casting; Use CNC machine tools to turn heat-treated castings to form brake disc components; Carry out quality inspection on the original brake discs and select qualified ones.

2. A method for machining a rail brake disc according to claim 1, characterized in that: The method of manufacturing a brake disc upper mold and a brake disc lower mold for sand casting according to the mold model comprises: The mold model is segmented along a horizontal plane to obtain an upper mold model and a lower mold model; According to the upper mold model and the lower mold model, a brake disc upper mold and a brake disc lower mold made of metal are turned out by using a CNC machine tool.

3. A method for processing a rail brake disc according to claim 1, characterized in that: The method for making molding sand comprises: Molding sand is obtained by mixing quartz sand, clay and water; The method of designing and manufacturing a sand box for sand casting according to the brake disc mold includes: Obtain the horizontal section with the largest area among all horizontal sections of the upper mold of the brake disc and the lower mold of the brake disc, and record them as the upper mold section and the lower mold section; According to the size of the upper mold cross section, a circle that completely covers the upper mold cross section and has the smallest area is obtained, which is recorded as the upper circle; According to the size of the lower mold cross section, a circle that completely covers the lower mold cross section and has the smallest area is obtained, which is recorded as the lower circle; Compare the areas of the upper circle and the lower circle, and select the one with the larger area as the reference circle; According to the area of ​​the reference circle, a square is obtained which completely covers the reference circle and the minimum distance between the four sides and the reference circle is equal to one quarter of the diameter of the reference circle, and the square is recorded as the reference square; Four metal plates are used to enclose a sand box, which has two openings at opposite positions. The surface of one opening is recorded as the upper surface of the sand box, and the surface of the other opening is recorded as the lower surface of the sand box; The top and bottom of the sand box are the same as the reference square, and the area occupied by the sand box can completely contain the upper mold and the lower mold of the brake disc.

4. A method for machining a rail brake disc according to claim 1, characterized in that: The method of completing the casting by using the brake disc mold, the molding sand and the sand box to form the sand mold includes: Place the sand box on a level surface; Place the brake disc upper mold in the center of the sand box; Fill the sand box with molding sand and completely cover the brake disc upper mold; Apply pressure to the molding sand in the sand box to make it compact and fit the mold on the brake disc. Clean the molding sand to make it flush with the top of the sand box. The upper mold of the brake disc is taken out from the sand box to obtain an upper sand mold; Take another sand box and place it on a horizontal surface; Place the brake disc lower mold in the center of the sand box; Fill the sand box with molding sand until it completely covers the brake disc lower mold; Apply pressure to the molding sand in the sand box to make it compact and fit the lower mold of the brake disc. Clean the molding sand to make it flush with the top of the sand box. The brake disc lower mold is taken out from the sand box to obtain a lower sand mold.

5. A method for machining a rail brake disc according to claim 4, characterized in that: The step of obtaining a loose detection area on a sand mold includes: Obtain three-dimensional models of the upper sand mold and the lower sand mold respectively, and record them as the upper model and the lower model respectively; Obtain the horizontal planes that coincide with the upper and lower surfaces of the upper model respectively, and record them as the upper surface and the lower surface of the upper model; Obtain the horizontal planes that coincide with the upper and lower surfaces of the lower model respectively, and record them as the upper surface and the lower surface of the lower model; Set the progressive interval; For the upper model and the lower model, use a plane parallel to the upper and lower surfaces of the upper model and a plane parallel to the upper and lower surfaces of the lower model respectively, starting from the upper surface, in the direction from the upper surface to the lower surface, and intercept the upper model and the lower model at every progressive interval; The planes used that are parallel to the upper and lower surfaces of the upper model and the planes that are parallel to the upper and lower surfaces of the lower model are recorded as cross sections; After the upper model and the lower model are intercepted each time, the projections of the upper mold and the lower mold on the cross section are obtained respectively in the direction from the upper surface to the lower surface; After each interception of the upper model and the lower model, respectively obtain the distance between the cross section and the lower surface of the upper model or the lower model, and stop intercepting the upper model or the lower model when the distance is less than the progressive interval; For each independent projection on the cross section, obtain the edge contour of the projection; For each independent projection, obtain the centroid of the projection figure, and select any point on the edge contour line of the projection, connect the centroid of the projection figure with the edge contour line of the projection, and obtain the length of the connection line, which is recorded as the contour distance of the independent projection; For each independent projection, obtain the shortest contour distance of the independent projection; Set distance threshold; Compare the shortest contour distance of each independent projection to a distance threshold; The independent projection whose shortest contour distance is less than the distance threshold is marked, and the portion corresponding to the independent projection on the upper model or the lower model is obtained as the loose detection area.

6. A method for machining a rail brake disc according to claim 5, characterized in that: The looseness detection is performed on the looseness detection area on the sand mold, and the sand mold is divided into a qualified sand mold and a defective sand mold according to the detection result, including: For each loose detection area, an image of the loose detection area is collected before the loose detection, and recorded as an initial image; Apply pressure to the loose detection area in a direction parallel to the upper and lower surfaces of the sand mold and pointing to the loose detection area; After applying pressure to the loose detection area, an image of the loose detection area is collected again and recorded as a comparison image; The comparison image is compared with the initial image to determine whether the looseness detection area is loosened after pressure is applied; If a loose detection area on the sand mold is loose, the sand mold is classified as a defective sand mold; If all loose detection areas on the sand mold are not loose, the sand mold is classified as a qualified sand mold.

7. A method for machining a rail brake disc according to claim 1, characterized in that: The method of cleaning the brake disc casting blank to form the brake disc casting comprises: Clean the molding sand and burrs attached to the surface of the brake disc casting rough blank; The runner and riser portions existing on the brake disc casting blank are partially removed using a cutting tool.

8. A method for machining a rail brake disc according to claim 1, characterized in that: The quality inspection of the brake disc original parts to select qualified brake discs includes: Use ultrasonic waves to perform nondestructive testing on the original brake disc to check whether there are pores and cracks inside the original brake disc; Check the flatness of the brake disc surface; The original brake discs with no pores and cracks inside and a smooth surface are classified as qualified brake discs.

Images