Preparation method of high-yield and high-ductility powder metallurgy motor end ring

Abstract

The invention discloses a high-yield and high-ductility powder metallurgy motor end ring and a preparation method thereof, and belongs to the technical field of powder metallurgy. The preparation method comprises the following steps: by taking red copper powder as a raw material, carrying out compression molding, sintering at 960-980 DEG C, and carrying out finishing, surface treatment, oil drying and annealing treatment to obtain the powder metallurgy motor end ring. The motor end ring is directly formed through powder metallurgy, the overall mechanical performance is excellent, the electrical conductivity is good, the material utilization rate can reach 95%, the yield can reach 96%, the density can reach 8.5 g / cm < 3 >, the hardness can reach HRF45-55, the ductility is good, and the motor end ring is free of cracks after being compressed by 20% in the radial direction.

Description

Technical Field

[0001] The present invention belongs to the technical field of powder metallurgy, and more specifically, relates to a method for preparing a powder metallurgy motor end ring with high yield and high ductility. Background Art

[0002] Motor end rings are part of the motor rotor, and each motor rotor typically requires two. Their primary function is to connect the conductor bars extending beyond the core, ensuring smooth current conduction. End rings offer excellent electrical and thermal conductivity, along with high strength and resistance to softening at high temperatures. This is particularly important for rotor end rings in high-speed rail transit motors.

[0003] In electric motors, end rings typically refer to a portion of the rotor windings, and their design and material selection have a significant impact on the motor's performance. For example, copper end rings are widely used in various motor applications to ensure stable operation and efficient energy conversion. Furthermore, the design and manufacturing process of the end rings must take into account the specific application scenarios and requirements of the motor to ensure performance under harsh conditions such as high temperatures and high speeds. Currently, the rotor end rings of mainstream motors are all made of copper. Copper is widely used in motor manufacturing because of its excellent electrical conductivity and thermal conductivity, second only to silver. Its excellent plasticity makes it easy to hot-press and cold-press, and it has good weldability. Its electrical conductivity is 1.5 times higher than that of aluminum.

[0004] Existing rotor end rings are produced through a mechanical process to achieve the specific structure and precision of gears. The production process is as follows: electrolytic copper is smelted into molten copper, cast into copper rods, and then traditionally machined to meet the drawing specifications. This mechanical method offers advantages such as high precision, good stability, and adaptability to a wide range of materials and shapes, but it also has disadvantages such as high equipment costs and limited flexibility. Metallurgical powder processing, on the other hand, involves forming metal powders and sintering them for subsequent processing. It offers advantages such as low cost, suitability for large-scale production, suitability for producing parts with complex shapes, and high material utilization. Summary of the Invention

[0005] In response to the above-mentioned problems existing in the prior art, the technical problem to be solved by the present invention is to provide a method for preparing powder metallurgy motor end rings with high yield and high ductility, which adopts direct forming by powder metallurgy, and the obtained motor end rings have excellent overall mechanical properties and good conductivity; another technical problem to be solved by the present invention is to provide a powder metallurgy motor end ring prepared by this preparation method.

[0006] In order to solve the above technical problems, the technical solutions adopted by the present invention are as follows:

[0007] The invention discloses a method for preparing a powder metallurgy motor end ring with high yield and high ductility. The method uses copper powder as raw material, presses and shapes the powder metallurgy motor end ring, and then sinters the powder metallurgy motor end ring at 960-1010°C. The powder metallurgy motor end ring is obtained through finishing, surface treatment, oil drying and annealing.

[0008] Preferably, the purity of the copper powder is not less than 99.9%.

[0009] Preferably, the pressing process is as follows: using a 250T mechanical press die, pressing the prepared raw material powder in a mold at a pressure of 600MPa to obtain a molding density of 7-7.5g / cm 3 of the green body.

[0010] Preferably, the sintering time is 5 to 7 hours.

[0011] Preferably, the annealing temperature is 620-680° C., and the annealing time is 3-4 hours.

[0012] Preferably, the finishing process is: placing the sintered product into a mold of a 500T hydraulic shaping machine for finishing.

[0013] The method for preparing the powder metallurgy motor end ring specifically comprises the following steps:

[0014] 1) Mixing step: preparing powdered raw materials;

[0015] 2) Forming step: placing the prepared powder raw material into a mold of a molding machine and pressing it to obtain a molded green body;

[0016] 3) Sintering step: placing the green body prepared above in a sintering furnace for sintering, so that sintering necks are formed between the green body particles;

[0017] 4) Finishing and surface treatment step: placing the sintered neck obtained in step 3) into a mold of a shaping machine for finishing and then performing surface treatment;

[0018] 5) Cleaning, oil drying and annealing step: The product obtained in step 4) is cleaned and oil dried, and then placed in a sintering furnace for annealing to obtain a powder metallurgy motor end ring.

[0019] Preferably, in step 4), the surface treatment process is: demoulding after finishing treatment, and after demoulding, using a nylon brush of a CNC lathe to remove burrs on the end surface of the product caused by processing.

[0020] Preferably, in step 5), the oil drying process is: placing the cleaned product in an oil drying furnace at 300° C. to remove the residual oil inside the product.

[0021] The powder metallurgy motor end ring is prepared by the method for preparing the powder metallurgy motor end ring with high yield and high ductility.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1) The motor end ring prepared by the present invention has excellent overall mechanical properties and good electrical conductivity. Due to the direct forming by powder metallurgy, the material utilization rate can reach 95%, the finished product rate can reach 96%, and the density can reach 8.5g / cm 3 , hardness can reach HRF45-55, good ductility (20% radial compression without cracks);

[0024] 2) The present invention adopts shaping to ensure the precision requirements of the product, replacing the machining in traditional technology and reducing the waste of raw materials;

[0025] 3) This invention utilizes an environmentally friendly and energy-saving production process, which not only reduces energy consumption but also minimizes environmental pollution. Furthermore, this method simplifies production steps, shortens production cycles, and improves production efficiency. Furthermore, the consistency and reliability of the product are significantly improved, meeting the stringent requirements of high-end motor manufacturing for high-density, high-ductility pure copper rotor end rings. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is the main view of the green compact after pressing;

[0027] Figure 2 for Figure 1 A-axis cross-sectional view of the green body after intermediate pressing;

[0028] Figure 3 Schematic diagram of the through-hole structure of the green compact after pressing;

[0029] Figure 4 Schematic diagram of the three-dimensional structure of the green body after pressing;

[0030] In the figure: 1. end ring body; 2. through hole; 3. special-shaped hole; 4. first end face; 5. second end face; 6. outer contour; 7. inner contour. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solutions and advantages of the present invention clearer, the present invention will be further described below in conjunction with specific examples. In the following examples, unless otherwise specified, the technical means used are conventional means well known to those skilled in the art. In the examples, if specific conditions are not specified, they are carried out according to conventional conditions or the conditions recommended by the manufacturer. The reagents or instruments used are not specified by the manufacturer, and are all conventional products that can be purchased commercially.

[0032] In the following examples, the electrolytic copper powder used is pure copper powder purchased from Chongqing Youyan Chongye New Materials Co., Ltd.; METALFLOW-B is a lubricant purchased from Suzhou Gaituo Lubrication Technology Co., Ltd.; and the atomized copper powder is pure copper powder purchased from Tongling Xinjia Powder New Materials Co., Ltd.

[0033] This application provides powder metallurgy motor end ring products, the structure of which is as follows Figure 1-4 As shown, it includes an end ring body 1, 22 through holes 2, 1 special-shaped hole 3, a first end face 4, a second end face 5, an outer contour 6, and an inner contour 7. The end ring body 1 has an annular geometric shape. 22 through holes 2 are evenly distributed along the circumferential direction on the end ring body 1. A stepped hierarchical structure is constructed inside each through hole 2, and the stepped hole wall is composed of an outer contour 6 and an inner contour 7. Each contour surface must meet the contour accuracy of 0.0508mm. A special-shaped hole 3 is provided in the center of the end ring body 1. The main contour of the special-shaped hole 3 is a rectangular groove structure extending outward at both ends of the inner circular hole. The edges of the grooves are treated with a smooth transition to avoid sharp edges and corners, thereby effectively reducing stress concentration and enhancing the structural strength and stability of the end ring. In addition, the overall contour of the special-shaped hole 3 needs to be controlled within an extremely small tolerance range to ensure that it can meet high-precision requirements during the assembly and use of the end ring.

[0034] Example 1

[0035] A method for preparing a powder metallurgy motor end ring with high yield and high ductility comprises the following steps:

[0036] 1) Mixing: Prepare the raw material mixture according to the specification that the copper content of powdered C11000 oxygen-free copper is not less than 99.9%. Weigh the raw material powder formula of electrolytic copper powder and METALFLOW-B at a mass ratio of 100:0.15 and mix them;

[0037] 2) Molding: Using a traditional 250T mechanical press die, the prepared powder raw materials were pressed into shape in a mold at a pressure of 600MPa to obtain a molding density of 7.35-7.45g / cm 3 The green body has 22 evenly distributed through holes and a special-shaped hole in the middle, which can reduce the friction during demoulding by step demoulding;

[0038] 3) Sintering: The green body prepared above is placed in a sintering furnace and sintered for 6 hours, wherein the green body is kept at a temperature of 970±10°C in a protective atmosphere for more than 60 minutes to form sintering necks between the green body particles;

[0039] 4) Finishing and surface treatment: A 500T hydraulic shaping machine is used to place the sintered neck obtained in step 3) into the shaping machine mold for finishing. The product is ensured to have an overall length tolerance of 0.3mm, an inner and outer diameter tolerance of 0.1mm, a profile accuracy of 0.0508mm, and an end surface hardness of HRF45-55. Step demolding is also used to reduce friction during demolding. After demolding, a nylon brush used on a CNC lathe is used to remove burrs on the end surface of the product caused by machining.

[0040] 5) Cleaning, oil drying, and annealing: The product obtained in step 4) is placed in a water washer to remove dirt from the surface of the product. The product is then subjected to an oil drying furnace at 300°C to remove residual oil from the interior of the product. The product is then annealed in a sintering furnace for 3 hours, wherein the product is kept at 670±10°C in a protective atmosphere for more than 20 minutes to remove residual stress and ensure product ductility and hardness.

[0041] 6) Product quality inspection: Confirm the size and material properties of the product, clean the product with a hydrocarbon cleaner to remove dirt on the surface of the product, inspect the product appearance, and then package the final product, which is recorded as Product 1.

[0042] Example 2

[0043] When preparing a powder metallurgy motor end ring with high yield and high ductility, the raw powder in step 1) is mechanically weighed according to a mass ratio of atomized copper powder and METALFLOW-B of 100:0.15. The remaining preparation steps and parameters are the same as those in Example 1 to obtain a powder metallurgy motor end ring, which is recorded as Product 2.

[0044] Example 3

[0045] When preparing high-yield, high-ductility powder metallurgy motor end rings, the molding density in step 2) is 7.15-7.25 g / cm 3 The remaining preparation steps and parameters are the same as those in Example 1 to obtain a powder metallurgy motor end ring, which is recorded as Product 3.

[0046] Example 4

[0047] When preparing a powder metallurgy motor end ring with high yield and high ductility, the sintering temperature in step 3) is 1000±10°C, the sintering time is 6 hours, and the holding time is 60 minutes. The remaining preparation steps and parameters are the same as those in Example 1. A powder metallurgy motor end ring is obtained, which is recorded as Product 4.

[0048] Example 5

[0049] When preparing a powder metallurgy motor end ring with high yield and high ductility, the annealing temperature in step 5) is 630±10°C, the annealing time is 3 hours, and the holding time is 20 minutes. The remaining preparation steps and parameters are the same as those in Example 1. A powder metallurgy motor end ring is obtained, which is recorded as Product 5.

[0050] Comparative Example 1

[0051] The preparation method of the traditional copper motor rotor end ring includes the following steps:

[0052] 1) Rough casting: Pour the electrolytic copper liquid into a circular mold with an outer diameter of 78mm and an inner diameter of 32mm. The mold is pre-coated and heated to 200℃. The casting temperature is 1250-1300℃. The final density is 8.6g / cm 3 The ring rough blank;

[0053] 2) Machining: First, 22 through holes and one special-shaped hole with a single-side diameter of 0.3mm are cut on the rough ring blank using wire cutting. Then, both end faces are double-sided ground. After that, the outer diameter, special-shaped hole, and inner and outer contours of the 22 through holes are rough-turned using a CNC machine tool, and then fine-turned to meet the drawing requirements.

[0054] 3) Annealing and surface treatment: The copper motor end ring was obtained by annealing at 600° C. to eliminate stress and brushing the edges to remove burrs, and was recorded as Product 6.

[0055] Example 6

[0056] Performance tests were conducted on the products prepared in Examples 1-5 and Comparative Example 1. Hardness was tested by measuring the surface using a Rockwell hardness tester, with the average value of each group of eight samples taken. Ductility was tested by performing compression tests using a universal testing machine and calculating the difference in diameter before and after compression. Density was tested using a buoyancy method using an electronic balance. Material utilization was tested by measuring the weight difference between the rough and finished products using an electronic balance. The yield rate was calculated using the direct counting method. The results are shown in Table 1.

[0057] Table 1 Product performance results

[0058]

[0059] As shown in Table 1, Product 4 has the best ductility but low hardness; Product 5 has the highest hardness but poor ductility; Product 1 achieves both high hardness and high ductility among Products 1-5; and while Products 1 and 6 have similar physical properties, Product 6's material utilization rate is far lower than that of Product 1. Compared to traditional methods, the products produced through the powder metallurgy process of the present invention not only achieve superior physical properties but also significantly reduce material consumption, energy consumption, and pollution emissions, resulting in significant economic and environmental benefits.

[0060] 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 principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for preparing a high-yield, high-ductility powder metallurgy motor end ring, characterized in that: The powder metallurgy motor end ring is made by pressing copper powder as raw material, sintering at 960-1010 DEG C, and undergoing finishing, surface treatment, oil drying and annealing treatment.

2. The method for preparing a high-yield, high-ductility powder metallurgy motor end ring according to claim 1, characterized in that: The purity of the copper powder is not less than 99.9%.

3. The method for preparing a high-yield, high-ductility powder metallurgy motor end ring according to claim 1, characterized in that: The pressing process is as follows: using a 250T mechanical press die frame, the prepared raw material powder is pressed into a mold under a pressure of 600MPa to obtain a molding density of 7-7.5g / cm 3 of the green body.

4. The method for preparing a high-yield, high-ductility powder metallurgy motor end ring according to claim 1, characterized in that: The sintering time is 5 to 7 hours.

5. The method for preparing a high-yield, high-ductility powder metallurgy motor end ring according to claim 1, characterized in that: The annealing temperature is 620-680° C., and the annealing time is 3-4 hours.

6. The method for preparing a high-yield, high-ductility powder metallurgy motor end ring according to claim 1, characterized in that: The finishing process is as follows: the sintered product is placed in a mold of a 500T hydraulic shaping machine for finishing.

7. The method for preparing a high-yield, high-ductility powder metallurgy motor end ring according to claim 1, characterized in that: The specific steps include: 1) Mixing step: preparing powdered raw materials; 2) Forming step: placing the prepared powder raw material into a mold of a molding machine and pressing it to obtain a molded green body; 3) Sintering step: placing the green body prepared above in a sintering furnace for sintering, so that sintering necks are formed between the green body particles; 4) Finishing and surface treatment step: placing the sintered neck obtained in step 3) into a mold of a shaping machine for finishing and then performing surface treatment; 5) Cleaning, oil drying and annealing step: The product obtained in step 4) is cleaned and oil dried, and then placed in a sintering furnace for annealing to obtain a powder metallurgy motor end ring.

8. The method for preparing a high-yield, high-ductility powder metallurgy motor end ring according to claim 7, characterized in that: In the step 4), the surface treatment process is as follows: demoulding after finishing treatment, and after demoulding, burrs on the end surface of the product caused by processing are removed using a nylon brush of a CNC lathe.

9. The method for preparing a high-yield, high-ductility powder metallurgy motor end ring according to claim 7, characterized in that: In step 5), the oil drying process is as follows: placing the cleaned product in an oil drying furnace at 300° C. to remove the residual oil inside the product.

10. A powder metallurgy motor end ring prepared by the method for preparing a powder metallurgy motor end ring with high yield and high ductility according to any one of claims 1 to 9.

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