Method for reducing adhesive film on surface of tooth-shaped powder metallurgy die

Abstract

The invention discloses a method for reducing surface mucosa of a tooth-shaped powder metallurgy die, and belongs to the field of parts for transmitting torque in electric tools and engines. In the jet polishing process of the surface of the middle die step of the tooth-shaped powder metallurgy die, a rubber-diamond mixed material is adopted as a jet abrasive material, the rubber-diamond mixed abrasive material is conveyed into a throwing wheel system in a belt conveying mode, the initial speed of jet fluid is controlled to be 28.3 m / s by adjusting the centrifugal force of an impeller, and the jet polishing process is completed. Million of grinding materials make contact with the surface of the tooth-shaped powder metallurgy die in a sliding mode, the grinding effect is achieved under efficient impact, and finally the polishing effect is achieved. According to the invention, the discharge stress can be obviously eliminated, the surface smoothness is improved, the smoothness is increased, the purpose of preventing powder from sticking films is achieved, and meanwhile, the yield can be greatly increased.

Description

Technical Field

[0001] The invention belongs to the field of parts for transmitting torque in electric tools and engines, and in particular relates to a method for reducing sticky film on the surface of a tooth-shaped powder metallurgy die. Background Art

[0002] Powder metallurgy is an industrial technology that produces metal powder or uses metal powder (or a mixture of metal powder and non-metallic powder) as raw material, and then forms and sinters it to produce metal materials, composite materials and various types of products. Powder metallurgy technology has been widely used in transportation, machinery, electronics, aerospace, weapons, biology, new energy, information and nuclear industries, and has become one of the most dynamic branches in new materials science. Powder metallurgy technology has a series of advantages such as significant energy saving, material saving, excellent performance, high product precision and good stability, and is very suitable for mass production. In addition, some materials and complex parts that cannot be prepared by traditional casting methods and machining methods can also be manufactured by powder metallurgy technology, so it has received much attention from the industry. Powder metallurgy part molds often adopt different shapes to adapt to different part requirements. In practical applications, the part mold is a tooth-shaped middle mold step. Using traditional manual polishing methods, it is difficult to polish the step tooth tip to meet the finish requirements, which easily leads to the occurrence of powder sticking during production.

[0003] Jet polishing is a surface treatment technology that uses a high-speed jet of fluid and abrasive particles to grind and polish the surface of an object. The technology generally includes: (1) The supply of a jet medium, in which a jet medium (usually water or air) and abrasive particles are mixed to form a high-speed jet fluid. This can be achieved through a nozzle or a spray gun, where there is a small hole in the center of the nozzle, and the medium and abrasive are pushed out by pressure. (2) High-speed impact, in which the jet fluid impacts the surface of the object at a high speed. The choice of impact force and speed depends on the material of the object to be processed and the polishing effect to be achieved. The kinetic energy generated by the high-speed impact is converted into cutting and grinding forces, thereby changing the morphology of the surface of the object. (3) Grinding of suspended particles, in which the abrasive particles in the jet fluid are in direct contact with the surface of the object and grind under high-efficiency impact. The hardness and size of the abrasive particles affect the grinding effect and surface quality. (4) Surface modification, in addition to grinding, jet polishing can also achieve surface modification effects through mechanisms such as surface thermal deformation, compression and grain boundary changes. This process can eliminate surface defects and improve its mechanical properties to a certain extent. Jet polishing is widely used in the fields of polishing, deburring, and surface modification of metal materials. It has the advantages of high speed, applicability to workpieces of various shapes and materials, and less thermal impact on the workpiece surface. However, how to use conventional polishing to treat the workpiece and then use jet polishing to eliminate the discharge stress on the surface of the middle die step, improve the surface finish of the workpiece, increase the surface smoothness, and achieve the purpose of preventing sticking film on the surface of the tooth-shaped powder metallurgy mold has become an urgent problem to be solved. Summary of the invention

[0004] The purpose of the present invention is to provide a method for reducing the sticky film on the surface of a tooth-shaped powder metallurgy mold, which adopts conventional polishing followed by a jet polishing process, can significantly eliminate discharge stress, improve surface finish, and increase smoothness.

[0005] In order to solve the above problems, the technical solution adopted by the present invention is as follows:

[0006] A method for reducing sticky film on the surface of a tooth-shaped powder metallurgy mold. In the process of jet polishing the surface of a middle mold step of the tooth-shaped powder metallurgy mold, a rubber-diamond mixture is used as a jet abrasive, and the initial velocity of the jet abrasive fluid is controlled to be 25.4-33.9 m / s.

[0007] Furthermore, the mass ratio of the rubber particles to the diamond particles in the rubber-diamond mixture is 6kg:2-4g.

[0008] Furthermore, the mass ratio of the rubber particles to the diamond particles in the rubber-diamond mixture is 6kg:3g.

[0009] Furthermore, in the rubber-diamond mixture, the average particle size of the rubber particles is 0.2-0.8 mm; the average particle size of the diamond particles is 2-4 μm.

[0010] Furthermore, in the rubber-diamond mixture, the average particle size of the rubber particles is 0.2-0.6 mm; the average particle size of the diamond particles is 2-3 μm.

[0011] Furthermore, the method for controlling the initial velocity of the jet abrasive fluid is: conveying the rubber-diamond mixed abrasive into the impeller system by belt conveyor, and controlling the initial velocity of the jet fluid by adjusting the centrifugal force of the impeller.

[0012] Furthermore, the initial velocity of the sprayed abrasive fluid is controlled to be 28.3 m / s.

[0013] Furthermore, any of the above-mentioned methods for reducing sticky film on the surface of a tooth-shaped powder metallurgy mold comprises the following steps:

[0014] (1) The rubber raw material is washed, dried, crushed and cut to form rubber particles; the rubber particles are screened using a screen to retain rubber particles of 0.2 to 0.8 mm;

[0015] (2) Shearing and composite crushing the diamond raw material to obtain diamond particles, and then screening the diamond particles using a sieve to retain diamond particles of 2 to 4 μm;

[0016] (3) mixing the 0.2-0.8 mm rubber particles obtained in step (1) and the 2-4 μm diamond particles obtained in step (2) at a mass ratio of 6 kg:3 g to obtain a rubber-diamond mixed abrasive;

[0017] (4) The rubber-diamond mixed abrasive is transported into the impeller system by belt conveyor. The initial velocity of the jet fluid is controlled to 28.3 m / s by adjusting the centrifugal force of the impeller, so that millions of abrasive particles contact the surface of the toothed powder metallurgy mold in a sliding manner and perform grinding under high-efficiency impact, ultimately achieving a polishing effect.

[0018] Compared with the prior art, the advantages of the present invention are as follows:

[0019] 1) The present invention aims at solving the difficulty of conventional polishing of the mold after discharge. By adding jet polishing after conventional polishing, the time is controlled within 6 to 8 hours, which can significantly eliminate the discharge stress, improve the surface finish, increase the smoothness, and greatly increase the output.

[0020] 2) The present invention uses a mixture of rubber particles and diamond powder as an abrasive, and through high-speed spraying of the mixture of rubber particles and diamond powder, eliminates the discharge stress on the surface of the middle mold step, improves the surface finish, increases the surface smoothness, and achieves the purpose of preventing powder sticking.

[0021] 3) The present invention can reuse the same mold without the need for maintenance using traditional electrical machining methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is the principle diagram of jet polishing of each embodiment of the present invention;

[0023] Figure 2 The size diagram of the mixed abrasive of the present invention;

[0024] Figure 3 This is a physical picture of the middle mold step surface of the tooth-shaped powder metallurgy mold after conventional polishing in Comparative Example 1;

[0025] Figure 4 This is a physical picture of the middle mold step surface of the tooth-shaped powder metallurgy mold after jet polishing in Example 2;

[0026] Figure 5 This is a bar chart comparing the mass production of ZJHU0014 middle molds formed by conventional polishing in Comparative Example 1 and spray polishing in Example 2;

[0027] Figure 6 This is a bar chart comparing the mass production quantities of the two polishing methods for the JSBW0316 middle mold. DETAILED DESCRIPTION

[0028] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with specific embodiments.

[0029] The middle die step models of the tooth-shaped powder metallurgy dies involved in the following embodiments and comparative examples are: ZJHU0014 middle die and JSBW0316 middle die.

[0030] Example 1

[0031] A method for reducing sticky film on the surface of a tooth-shaped powder metallurgy mold, the steps are as follows:

[0032] (1) The rubber raw material is washed, impurities are removed, and then dried; the obtained rubber is put into a pulverizer, and the pulverizer pulverizes and cuts the rubber into rubber particles; the rubber particles are sieved using a sieve net, rubber particles with larger particle sizes are sieved out and pulverized again, and rubber particles with smaller particle sizes are sieved out, and finally rubber particles with a particle size of 0.2 to 0.8 mm are retained;

[0033] (2) The diamond raw material is sheared and composite crushed by an extrusion crusher with a shearing function to obtain diamond particles, and the diamonds are screened using a screening screen to finally screen out diamond particles of 2 to 4 μm;

[0034] (3) The 0.2-0.8 mm rubber particles obtained in step (1) and the 2-4 μm diamond particles obtained in step (2) are mixed in a mass ratio of 6 kg: 2-4 g to finally obtain a rubber-diamond mixed abrasive, such as Figure 2 shown.

[0035] (4) The rubber-diamond mixed abrasive is transported into the impeller system by belt conveyor, and the abrasive is ejected by the centrifugal force of the impeller. The initial velocity of the jet fluid is controlled to be 25.4-33.9 m / s, so that millions of abrasive particles contact the surface of the tooth-shaped powder metallurgy mold in a sliding manner and perform grinding under high-efficiency impact, ultimately achieving a polishing effect. The principle of jet polishing is as follows: Figure 1 shown.

[0036] The present invention uses diamond + rubber mixed particles as abrasives, and uses the extremely high hardness of diamonds and the performance of being mainly used for making cutting, grinding, drilling and other tools to allow its hard edges to grind the middle mold; the excellent flexibility of rubber is used to prevent the middle mold from being deformed; the excellent adhesion allows diamonds to be well adsorbed. After the two are mixed in proportion, they not only meet the requirements of abrasive hardness and have good grinding functions, but also have good adsorption effects.

[0037] Among them, rubber particles with a size of 0.2-0.8mm have the best adsorption to diamond particles with a size of 2-4μm. Rubber particles with a size of 0.2-0.8mm and diamond particles with a size of 2-4μm can take into account the grinding effect without deforming the mold. If the rubber particles are smaller than 0.2mm and the diamond particles are larger than 4μm, the diamond particle spraying time will be shorter, which will easily deform the middle mold and will be difficult to control. If the rubber particles are larger than 0.8mm and the diamond particles are smaller than 2μm, the spraying time will be longer, more than 10 hours, which is too time-consuming. Therefore, choosing rubber particles with a size of 0.2-0.8mm and diamond particles with a size of 2-4μm can not only meet the applicability requirements, but also maximize the economic benefits.

[0038] Since the actual polishing workshop requires slightly more diamond particles, the theoretical spraying time can be reduced, but if too many diamond particles are added, the rubber particles cannot absorb the diamonds, which will cause a waste of raw materials; if too few diamond particles are added, polishing can still be done normally, but the polishing efficiency will be greatly reduced, the polishing time will be longer, and the time-consuming cost will increase. Therefore, the mass ratio of rubber particles to diamond particles defined in the present invention is 6kg:2~4g, which can not only meet the polishing efficiency, but also absorb as many diamond particles as possible to reduce material waste.

[0039] The present invention controls the initial velocity of the injection fluid to be 25.4-33.9 m / s. When the initial injection velocity is higher than 33.9 m / s, although polishing can be performed, the time will be shortened, the pressure per unit time on the middle mold will increase, deformation will occur easily, and it is difficult to effectively control; when the initial injection velocity is lower than 25.4 m / s, the polishing efficiency will be greatly reduced, the time will be extended, which is not conducive to normal polishing operation.

[0040] Example 2

[0041] A method for reducing sticky film on the surface of a tooth-shaped powder metallurgy mold, the steps are as follows:

[0042] (1) The rubber raw material is washed, impurities are removed, and then dried; the obtained rubber is put into a pulverizer, and the pulverizer pulverizes and cuts the rubber into rubber particles; the rubber particles are sieved using a sieve net, rubber particles with larger particle sizes are sieved out and pulverized again, and rubber particles with smaller particle sizes are sieved out, and finally rubber particles with a particle size of 0.2 to 0.8 mm are retained;

[0043] (2) The diamond raw material is sheared and composite crushed by an extrusion crusher with a shearing function to obtain diamond particles, and the diamonds are screened using a screening screen to finally screen out diamond particles of 2 to 4 μm;

[0044] (3) The 0.2-0.8 mm rubber particles obtained in step (1) and the 2-4 μm diamond particles obtained in step (2) are mixed in a mass ratio of 6 kg:3 g to finally obtain a rubber-diamond mixed abrasive.

[0045] (4) The rubber-diamond mixed abrasive is transported into the impeller system by belt conveyor, and the abrasive is ejected by the centrifugal force of the impeller. The initial velocity of the jet fluid is controlled to be 28.3m / s, so that millions of abrasive particles contact the surface of the tooth-shaped powder metallurgy mold in a sliding manner and perform grinding under high-efficiency impact, ultimately achieving a polishing effect. The actual picture of the middle mold step surface of the polished tooth-shaped powder metallurgy mold is as follows: Figure 4 shown.

[0046] Example 3

[0047] A method for reducing sticky film on the surface of a tooth-shaped powder metallurgy mold, the steps are as follows:

[0048] (1) The rubber raw material is washed, impurities are removed, and then dried; the obtained rubber is put into a pulverizer, and the pulverizer pulverizes and cuts the rubber into rubber particles; the rubber particles are sieved using a sieve net, rubber particles with larger particle sizes are sieved out and pulverized again, and rubber particles with smaller particle sizes are sieved out, and finally rubber particles with a particle size of 0.2 to 0.8 mm are retained;

[0049] (2) The diamond raw material is sheared and composite crushed by an extrusion crusher with a shearing function to obtain diamond particles, and the diamonds are screened using a screening screen to finally screen out diamond particles of 2 to 4 μm;

[0050] (3) The 0.2-0.8 mm rubber particles obtained in step (1) and the 2-4 μm diamond particles obtained in step (2) are mixed in a mass ratio of 6 kg:2.5 g to finally obtain a rubber-diamond mixed abrasive.

[0051] (4) The rubber-diamond mixed abrasive is transported into the impeller system by belt conveyor, and the abrasive is ejected by the centrifugal force of the impeller. The initial velocity of the jet fluid is controlled to be 30.2 m / s, so that millions of abrasive particles contact the surface of the tooth-shaped powder metallurgy mold in a sliding manner and perform grinding under high-efficiency impact, ultimately achieving a polishing effect.

[0052] Example 4

[0053] A method for reducing sticky film on the surface of a tooth-shaped powder metallurgy mold, the steps are as follows:

[0054] (1) The rubber raw material is washed, impurities are removed, and then dried; the obtained rubber is put into a pulverizer, and the pulverizer pulverizes and cuts the rubber into rubber particles; the rubber particles are sieved using a sieve net, rubber particles with larger particle sizes are sieved out and pulverized again, and rubber particles with smaller particle sizes are sieved out, and finally rubber particles with a particle size of 0.2 to 0.8 mm are retained;

[0055] (2) The diamond raw material is sheared and composite crushed by an extrusion crusher with a shearing function to obtain diamond particles, and the diamonds are screened using a screening screen to finally screen out diamond particles of 2 to 4 μm;

[0056] (3) The 0.2-0.8 mm rubber particles obtained in step (1) and the 2-4 μm diamond particles obtained in step (2) are mixed in a mass ratio of 6 kg:2.1 g to finally obtain a rubber-diamond mixed abrasive.

[0057] (4) The rubber-diamond mixed abrasive is transported into the impeller system by belt conveyor, and the abrasive is ejected by the centrifugal force of the impeller. The initial velocity of the jet fluid is controlled to be 25.4 m / s, so that millions of abrasive particles contact the surface of the tooth-shaped powder metallurgy mold in a sliding manner and perform grinding under high-efficiency impact, ultimately achieving a polishing effect.

[0058] Example 5

[0059] A method for reducing sticky film on the surface of a tooth-shaped powder metallurgy mold, the steps are as follows:

[0060] (1) The rubber raw material is washed, impurities are removed, and then dried; the obtained rubber is put into a pulverizer, and the pulverizer pulverizes and cuts the rubber into rubber particles; the rubber particles are sieved using a sieve net, rubber particles with larger particle sizes are sieved out and pulverized again, and rubber particles with smaller particle sizes are sieved out, and finally rubber particles with a particle size of 0.2 to 0.8 mm are retained;

[0061] (2) The diamond raw material is sheared and composite crushed by an extrusion crusher with a shearing function to obtain diamond particles, and the diamonds are screened using a screening screen to finally screen out diamond particles of 2 to 4 μm;

[0062] (3) The 0.2-0.8 mm rubber particles obtained in step (1) and the 2-4 μm diamond particles obtained in step (2) are mixed in a mass ratio of 6 kg:3.9 g to finally obtain a rubber-diamond mixed abrasive.

[0063] (4) The rubber-diamond mixed abrasive is transported into the impeller system by belt conveyor, and the abrasive is ejected by the centrifugal force of the impeller. The initial velocity of the jet fluid is controlled to be 33.9 m / s, so that millions of abrasive particles contact the surface of the tooth-shaped powder metallurgy mold in a sliding manner and perform grinding under high-efficiency impact, ultimately achieving a polishing effect.

[0064] Comparative Example 1

[0065] The conventional polishing process (the polishing tool is a vibration grinder and the polishing medium is a grinding paste) is used to polish the middle die step surface of the tooth-shaped powder metallurgy mold. The actual picture of the middle die step surface of the tooth-shaped powder metallurgy mold after polishing is as follows: Figure 3 shown.

[0066] Conventional polishing process parameters are shown in Table 1:

[0067] Table 1 Statistics of time required for conventional polishing methods

[0068] Rough polishing Medium throw Fine polishing Abrasive paste 600# 1200#&1800# 3000# time 6h 6h 8h

[0069] The surface finish, surface smoothness and powder sticking to the mold of the middle mold step surface of the toothed powder metallurgy mold after spray polishing in the above Examples 2 to 5 and Comparative Example 1 were analyzed and tested respectively.

[0070] Among them, the surface finish test method is: instrument: surface roughness tester, model: SURFCOM 1400G; test conditions: temperature 20-25°C; humidity below 70%.

[0071] Surface smoothness test method: Instrument: electron microscope, model: ALL WAYS; Test conditions: temperature 10-30℃; humidity below 70%.

[0072] Powder sticking to mold condition: verified through the equipment used to produce the product.

[0073] Table 2 Analysis and test results of the surface condition of the middle die step of the tooth-shaped powder metallurgy die after jet polishing of Examples 2 to 5 and Comparative Example 1

[0074] Surface finish Ra Surface smoothness Powder sticking to mold Example 2 0.06 like Figure 4 Shown less Example 3 0.06-0.07 like Figure 4 Shown less Example 4 0.07-0.08 like Figure 4 Shown less Example 5 0.06-0.07 like Figure 4 Shown less Comparative Example 1 0.10-0.14 like Figure 3 Shown More

[0075] From the comparison of the data in Table 2, it is found that the jet fluid impacts the surface of the object at high speed. The choice of impact force and speed depends on the material of the object to be processed and the polishing effect to be achieved. The kinetic energy generated by the high-speed impact is converted into cutting and grinding forces, thereby changing the morphology of the surface of the object. When the initial velocity of the abrasive is within the control range, the greater the impact force on the surface of the middle mold step, and then more kinetic energy is converted into cutting and grinding forces, improving the polishing effect. The abrasive particles in the jet fluid are in direct contact with the surface of the middle mold step and perform grinding under high-efficiency impact, so the hardness and size of the abrasive particles will affect the grinding effect and surface quality.

[0076] The embodiment of the present invention uses a rubber-diamond mixed abrasive (wherein the particle size range of the rubber is controlled at 0.2 to 0.8 mm, and the particle size of the diamond is controlled at 2 to 4 μm). On the one hand, it can eliminate the discharge stress on the surface of the middle mold step and improve the surface finish and smoothness. On the other hand, it can improve the hardness of the abrasive, and can better grind the surface of the middle mold step under high-speed impact, thereby improving the polishing effect.

[0077] Compared with the conventional polishing treatment of the middle mold step surface of the tooth-shaped powder metallurgy mold in Comparative Example 1, the jet polishing treatment in the embodiment of the present invention has a significant effect on the mass production of ZJHU0014 middle mold and JSBW0316 middle mold as shown in Table 3, Table 4, Figure 5 and Figure 6 shown.

[0078] Table 3 Comparison of mass production of ZJHU0014 die by conventional polishing in comparative example 1 and spray polishing in example 2

[0079] Middle mold quantity Remark 1# 94570 Conventional polishing 2# 138198 Conventional polishing 3# 22506 Conventional polishing 4# 1000 Conventional polishing 5# 1000 Conventional polishing 6# 1370000 Jet polishing

[0080] Table 4 Comparison of mass production quantity of two polishing methods for JSBW0316

[0081]

[0082] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for reducing sticky film on the surface of tooth-shaped powder metallurgy molds, characterized in that: In the jet polishing process of the middle die step surface of the tooth-shaped powder metallurgy die, a rubber-diamond mixture is used as the jet abrasive, and the initial velocity of the jet abrasive fluid is controlled to be 25.4-33.9 m / s.

2. The method for reducing sticky film on the surface of tooth-shaped powder metallurgy mold according to claim 1, characterized in that: The mass ratio of the rubber particles to the diamond particles in the rubber-diamond mixture is 6kg:2-4g.

3. The method for reducing sticky film on the surface of tooth-shaped powder metallurgy mold according to claim 2, characterized in that: The mass ratio of the rubber particles to the diamond particles in the rubber-diamond mixture is 6kg:3g.

4. The method for reducing sticky film on the surface of tooth-shaped powder metallurgy mold according to claim 1, characterized in that: In the rubber-diamond mixture, the average particle size of the rubber particles is 0.2-0.8 mm; the average particle size of the diamond particles is 2-4 μm.

5. The method for reducing sticky film on the surface of tooth-shaped powder metallurgy mold according to claim 4, characterized in that: In the rubber-diamond mixture, the average particle size of the rubber particles is 0.2-0.6 mm; the average particle size of the diamond particles is 2-3 μm.

6. The method for reducing sticky film on the surface of tooth-shaped powder metallurgy mold according to claim 1, characterized in that: The method for controlling the initial velocity of the jet abrasive fluid is: conveying the rubber-diamond mixed abrasive into the impeller system by belt conveyor, and controlling the initial velocity of the jet fluid by adjusting the centrifugal force of the impeller.

7. The method for reducing sticky film on the surface of tooth-shaped powder metallurgy mold according to claim 1, characterized in that: The initial velocity of the sprayed abrasive fluid was controlled to be 28.3 m / s.

8. The method for reducing sticky film on the surface of tooth-shaped powder metallurgy molds according to any one of claims 1 to 7, characterized in that: Here are the steps: (1) The rubber raw material is washed, dried, crushed and cut to form rubber particles; the rubber particles are screened using a screen to retain rubber particles of 0.2 to 0.8 mm; (2) Shearing and composite crushing the diamond raw material to obtain diamond particles, and then screening the diamond particles using a sieve to retain diamond particles of 2 to 4 μm; (3) mixing the 0.2-0.8 mm rubber particles obtained in step (1) and the 2-4 μm diamond particles obtained in step (2) at a mass ratio of 6 kg:3 g to obtain a rubber-diamond mixed abrasive; (4) The rubber-diamond mixed abrasive is transported into the impeller system by belt conveyor. The initial velocity of the jet fluid is controlled to 28.3 m / s by adjusting the centrifugal force of the impeller, so that millions of abrasive particles contact the surface of the toothed powder metallurgy mold in a sliding manner and perform grinding under high-efficiency impact, ultimately achieving a polishing effect.

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