A powder processing apparatus and method for improving powder sphericity and surface finish

Abstract

The present application relates to a kind of powder processing device and method for improving powder sphericity and surface finish, including processing cylinder and multiple rotating mechanism, lower rotating mechanism includes stirring blade, can be rotated in positive direction, upper rotating mechanism includes shaping blade, can be rotated in positive direction or reverse direction.The stirring blade of lower rotating mechanism is a certain obtuse angle with the direction of rotation, can better lift up powder, the shaping blade of upper rotating mechanism includes two inclined planes of positive and negative direction.The rotating direction of upper and lower rotating mechanism is opposite first, the inclined plane of shaping blade towards the direction of rotation is opposite with the direction of movement of the powder lifted up, angle is close to vertical, impact and break up agglomerated powder and satellite ball, then the rotating direction of upper and lower rotating mechanism is same, the inclined plane of shaping blade towards the direction of rotation is close to the direction of movement of the powder lifted up, mainly with friction effect, improve powder surface finish.The stirring blade of lower rotating mechanism makes the friction effect between powder particles in cylinder, can also quickly improve the surface finish of powder.

Description

Technical Field

[0001] This invention relates to the field of metal powder preparation technology, and more specifically to a powder processing apparatus and method for improving powder sphericity and surface finish. Background Technology

[0002] In recent years, metal powder additive manufacturing (AM) and injection molding (MIM) technologies have developed rapidly. Both can meet the needs of rapid manufacturing of complex structural parts, but they also place higher demands on the morphology of metal powder raw materials. Metal powders prepared by VIGA atomization have relatively high sphericity and can be used as raw materials for metal powder additive manufacturing. However, the resulting powder often contains a certain number of satellite spheres, agglomerated powder, and irregular powder, leading to deterioration in powder sphericity, decreased bulk density and flowability, and overall powder performance inferior to products prepared by PREP and other processes. Metal powders prepared by water atomization or water-air combined atomization have relatively poor sphericity and can generally be used as raw materials for metal powder injection molding. However, due to the presence of a large number of irregular powder, agglomerated powder, or satellite spheres, the powder tap density decreases, limiting the loading capacity and rheological properties after feeding, affecting injection molding performance and further improvement of the density and mechanical properties of sintered parts.

[0003] For high-quality powder preparation, besides improving powder morphology through atomization process improvements, powder processing techniques can also enhance the process. Traditional post-processing methods mainly include crushing and grinding. Powder crushing processes and equipment (e.g., toothed disc crushers) can break agglomerated powder into independent small particles and separate satellite particles from the surface of larger powder particles, improving powder sphericity. However, the crushed powder surface exhibits obvious angularity, significantly increasing surface roughness, which is detrimental to improving powder bulk density, tap density, and flowability. Powder grinding processes and equipment (e.g., air jet mills) can eliminate surface angularity to some extent, improving surface smoothness. However, due to limited force and energy, the crushing effect and efficiency for agglomerated powder and satellite particles are significantly reduced. Therefore, how to simultaneously and efficiently improve powder sphericity and surface smoothness remains a challenging problem in powder processing. Summary of the Invention

[0004] The purpose of this invention is to provide a powder processing apparatus and method to improve the sphericity and surface finish of powders, solving the problem that traditional powder processing processes are unable to simultaneously and efficiently break up agglomerated powders and satellite spheres, and improve the surface finish of powders. This invention can effectively improve the morphology of metal powder materials, as well as their comprehensive properties such as bulk density, tap density, and flowability, and enhance the applicability of gas-atomized and water-atomized powder raw materials in additive manufacturing and injection molding.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a powder processing device for improving the sphericity and surface smoothness of powder, comprising a powder processing cylinder and multiple rotating mechanisms installed inside it. The powder processing cylinder has a feeding port and valve at the top and a discharging port and valve at the bottom. The rotating stirring mechanism can be divided into an upper rotating mechanism and a lower rotating mechanism. The lower rotating mechanism includes two or more stirring blades, and its central rotating shaft is connected to a drive motor outside the powder processing cylinder, allowing it to rotate at high speed under the drive of the drive motor. Its rotation direction is defined as forward rotation. There is a small gap between the stirring blades of the lower rotating mechanism and the outer shell of the powder processing cylinder. The upper rotating mechanism includes two or more shaping blades, and its central rotating shaft is connected to a drive motor outside the powder processing cylinder, allowing it to rotate at high speed under the drive of the drive motor. The drive motor of the upper rotating mechanism can switch between forward and reverse rotation, that is, the rotation directions of the upper rotating mechanism and the lower rotating mechanism can be the same or opposite. There is a small gap between the shaping blades of the upper rotating mechanism and the outer shell of the powder processing cylinder. There is a certain distance between the upper rotating mechanism and the lower rotating mechanism. The powder processing cylinder is an inverted cone shape, and the powder processing cylinder may be provided with an air inlet and an air outlet at the top, which can achieve the purpose of vacuuming or replacing the atmosphere inside the powder processing cylinder.

[0006] Preferably, the stirring blades of the lower rotating mechanism form a certain angle (obtuse angle) with the direction of rotation, so as to better scoop and lift the powder during the rotation process.

[0007] Preferably, the shaping blade of the upper rotating mechanism includes two inclined surfaces, one on the front and one on the back. When the upper rotating mechanism rotates, the two inclined surfaces form different angles with the direction of rotation, one being an acute angle and the other an obtuse angle. The purpose of this design is that when the upper rotating mechanism and the lower rotating mechanism rotate in opposite directions, the angle between the inclined surface of the shaping blade facing the direction of rotation of the upper rotating mechanism and the direction of powder movement of the lower rotating mechanism is nearly perpendicular, so as to achieve a powder processing effect mainly based on impact crushing. When the upper rotating mechanism and the lower rotating mechanism rotate in the same direction, the inclined surface of the shaping blade facing the direction of rotation of the upper rotating mechanism is close to the direction of powder movement of the lower rotating mechanism, so as to achieve a powder processing effect mainly based on friction.

[0008] Preferably, the upper rotating mechanism can be composed of multiple identical upper rotating mechanisms, which are evenly arranged on the upper part of the powder processing cylinder.

[0009] Preferably, the surface shape of the shaping blade of the upper rotating mechanism can be flat, wavy, porous honeycomb, etc.

[0010] Preferably, the drive motor is an adjustable speed variable frequency motor, and the limiting speed of the upper rotating mechanism is greater than the limiting speed of the lower rotating mechanism.

[0011] This invention also provides a powder processing method for improving powder sphericity and surface finish, comprising the following steps:

[0012] Step 1: Place the powder to be processed into the powder processing cylinder through the feeding inlet. The lower limit of the powder height should exceed half of the stirring blades of the lower rotating structure, and the upper limit should not exceed the bottom of the shaping blades of the upper rotating mechanism. Close the feeding port valve.

[0013] Step 2: Vacuum the powder processing cylinder or replace the internal air with an inert gas.

[0014] Step 3: Turn on the drive motor of the lower rotating mechanism and make it rotate forward. Set the speed of the lower rotating mechanism to 500~1500 r / min. Then immediately turn on the drive motor of the upper rotating mechanism and make it rotate in reverse. Set the speed of the upper rotating mechanism to 1000~4000 r / min. Maintain this rotation for 10~60 minutes. After the time is up, turn off the motor of the upper rotating mechanism. The motor of the lower rotating mechanism will continue to rotate.

[0015] Step 4: Change the rotation direction of the upper rotating mechanism to forward, set the speed to 1000~3000 r / min, and turn on the drive motor of the upper rotating mechanism again. Maintain this rotation for 10~60 minutes, and then turn off all drive motors. Discharge the processed powder through the discharge port at the bottom of the powder processing cylinder to obtain powder with high sphericity and surface smoothness.

[0016] Compared with the prior art, the beneficial effects of the present invention are:

[0017] In the powder processing process, the stirring blades of the lower rotating mechanism can lift the powder upwards, giving it a high initial velocity. The direction of motion of the lifted powder is similar to the rotation direction of the lower rotating mechanism. When the upper and lower rotating mechanisms rotate in opposite directions, the angle between the inclined surface of the shaping blade facing the rotation direction of the upper rotating mechanism and the direction of motion of the powder lifted by the lower rotating mechanism is nearly perpendicular. Furthermore, since the direction of motion of the shaping blade and the lifted powder are opposite, their relative velocities are superimposed, thus significantly increasing the impact energy. This achieves a significant powder processing effect primarily based on impact crushing, effectively breaking up agglomerated powder and satellite sphere powder. When the upper and lower rotating mechanisms rotate in the same direction, the inclined surface of the shaping blade facing the rotation direction of the upper rotating mechanism is similar to the direction of motion of the powder lifted by the lower rotating mechanism, achieving a powder processing effect primarily based on friction. Moreover, the relative velocity between the shaping blade and the lifted powder is lower, reducing the collision energy. Therefore, it can remove the sharp edges of the powder surface and improve the surface smoothness of the powder. Simultaneously, during the entire processing, the stirring blades of the lower rotating mechanism rapidly stir the powder in the powder processing cylinder, enabling friction between powder particles and significantly improving the surface finish of the powder. Therefore, this invention utilizes a single device for one-time powder loading, efficiently optimizing and improving both powder sphericity and surface finish simultaneously. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the structure of a powder processing device for improving powder sphericity and surface smoothness according to the present invention.

[0019] Figure 2 This is a schematic diagram illustrating the powder processing principle of the powder processing device of the present invention, which improves the sphericity and surface smoothness of powder, when the upper and lower rotating mechanisms rotate in opposite directions during use.

[0020] Figure 3 This is a schematic diagram illustrating the powder processing principle of the powder processing device for improving powder sphericity and surface smoothness during use, where the upper and lower rotating mechanisms rotate in the same direction.

[0021] Figure 4 This is a schematic diagram of the structure of a powder processing device for improving powder sphericity and surface smoothness according to Embodiment 2 of the present invention.

[0022] Figure 5 This is a schematic diagram of the blade shape of the rotating mechanism of a powder processing device for improving powder sphericity and surface smoothness, as proposed in Embodiment 2 of the present invention.

[0023] In the diagram: 1. Upper rotating mechanism and shaping blades; 2. Lower rotating mechanism and stirring blades; 3. Powder processing cylinder; 4. Drive motor of the upper rotating mechanism (can rotate forward and reverse); 5. Drive motor of the lower rotating mechanism (forward rotation); 6. Upper shaping blades; 7. Lower stirring blades. Detailed Implementation

[0024] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0025] Example 1

[0026] Reference Figure 1 , Figure 2 , Figure 3 As shown, a powder processing device for improving powder sphericity and surface smoothness includes a powder processing cylinder 3 and multiple rotating mechanisms installed inside. The powder processing cylinder 3 has a feed port and valve at the top and a discharge port and valve at the bottom. The rotating mechanisms can be divided into an upper rotating mechanism 1 and a lower rotating mechanism 2. The lower rotating mechanism 2 includes two sets of stirring blades 7, each set of stirring blades 7 including four stirring blades 7. The central rotating shaft is connected to a drive motor 4 outside the powder processing cylinder 3, and can rotate at high speed under the drive of the drive motor 4. Its rotation direction is defined as forward rotation. The stirring blades 7 of the lower rotating mechanism 2 are connected to the outer shell of the powder processing cylinder 3. There is a 5mm gap between them. The upper rotating mechanism 1 has two identical rotating mechanisms, symmetrically distributed on the top of the powder processing cylinder 3. Each upper rotating mechanism 1 contains four shaping blades 6, and the central rotating shaft is connected to the drive motor 5 outside the powder processing cylinder 3. It can rotate at high speed under the drive of the drive motor 5. The drive motor 5 of the upper rotating mechanism 1 can realize forward and reverse switching, that is, the rotation direction of the upper rotating mechanism 1 and the lower rotating mechanism 2 can be the same or opposite. There is a 5mm gap between the shaping blades 6 of the upper rotating mechanism 1 and the outer shell of the powder processing cylinder. The distance between the upper rotating mechanism 1 and the lower rotating mechanism 2 is 20mm.

[0027] The powder processing cylinder 3 is an inverted cone shape, and the stirring blades 7 of the lower rotating mechanism 1 form a certain angle (135°) with the direction of rotation. The shaping blades 6 of the upper rotating mechanism 1 contain two inclined surfaces, one on the front and one on the back. When the upper rotating mechanism 1 rotates, the two inclined surfaces form different angles with the direction of rotation, one being an acute angle (45°) and the other an obtuse angle (135°). The surface shape of the shaping blades 6 of the upper rotating mechanism 1 is flat. The drive motors of the upper rotating mechanism 1 and the lower rotating mechanism 2 are variable frequency motors with adjustable speed. The speed adjustment range of the upper rotating mechanism 1 is 0-4000 r / min, and the speed adjustment range of the lower rotating mechanism 2 is 0-1500 r / min.

[0028] The powder post-processing using the apparatus of this embodiment includes the following steps:

[0029] Step 1: The powder to be processed is put into the powder processing cylinder 3 through the feeding inlet. The height of the powder is higher than the upper edge of the stirring blade of the lower rotating mechanism 2 and lower than the bottom edge of the shaping blade 6 of the upper rotating mechanism 1.

[0030] Step 2: Introduce nitrogen into the air inlet of powder processing cylinder 3 to replace the air inside the cylinder with nitrogen;

[0031] Step 3: Turn on the drive motor 4 of the lower rotating mechanism 2 to make it rotate forward, and set the speed of the lower rotating mechanism 2 to 1000 r / min. Then immediately turn on the drive motor 5 of the upper rotating mechanism 1 to make it rotate in reverse, and set the speed of the upper rotating mechanism to 3000 r / min. Maintain this rotation for 20 minutes. After the time is up, turn off the drive motor 5 of the upper rotating mechanism 1, while the drive motor 4 of the lower rotating mechanism 2 continues to rotate.

[0032] In this step, the stirring blades 7 of the lower rotating mechanism 2 can scoop up and lift the powder during rotation, giving the powder a high initial velocity. The direction of motion of the lifted powder is similar to the rotation direction of the lower rotating mechanism 2. Since the upper rotating mechanism 1 and the lower rotating mechanism 2 rotate in opposite directions, the angle between the inclined surface of the shaping blade 6 facing the rotation direction of the upper rotating mechanism 1 and the direction of motion of the powder lifted by the lower rotating mechanism is almost perpendicular. Furthermore, the direction of motion of the shaping blade 6 and the lifted powder are opposite, and the relative velocities are superimposed. Therefore, the impact energy is greatly increased, and a significant powder processing effect based on impact crushing can be achieved.

[0033] Step 4: Change the rotation direction of the upper rotating mechanism 1 to forward rotation, set the speed to 1500 r / min, turn on the drive motor 5 of the upper rotating mechanism 1 again, maintain this rotation for 40 minutes, and then turn off all drive motors. Discharge the processed powder through the discharge port at the bottom of the powder processing cylinder to obtain powder with high powder sphericity and surface smoothness. This can efficiently break up agglomerated powder and satellite powder.

[0034] In this step, the upper rotating mechanism 1 and the lower rotating mechanism 2 rotate in the same direction. The inclined surface of the shaping blade 6 facing the rotation direction of the upper rotating mechanism 1 is similar to the direction of the powder movement of the lower rotating mechanism 2, so as to achieve a powder processing effect mainly based on friction. In addition, the relative speed between the shaping blade 6 and the powder is low, which reduces the energy of the collision. Therefore, it can remove the sharp edges of the powder surface and improve the surface smoothness of the powder.

[0035] Throughout the entire preparation process described above, the stirring blades 7 of the lower rotating mechanism 2 rapidly stir the powder in the powder processing cylinder 3, which enables friction between powder particles and significantly improves the surface finish of the powder.

[0036] Example 2

[0037] Reference Figure 4 , Figure 5 As shown, a powder processing device for improving powder sphericity and surface smoothness includes a powder processing cylinder 3 and multiple rotating mechanisms installed inside. The powder processing cylinder 3 has a feed port and valve at the top and a discharge port and valve at the bottom. The rotating mechanisms can be divided into an upper rotating mechanism 1 and a lower rotating mechanism 2. The lower rotating mechanism 2 includes two sets of stirring blades 7, each set of stirring blades 7 including two stirring blades 7, and the central rotating shaft is connected to a drive motor 4 outside the powder processing cylinder 3. It can rotate at high speed under the drive of the drive motor 4, and its rotation direction is defined as forward rotation. There is a 10mm gap between the stirring blade 7 of the upper rotating mechanism 2 and the outer shell of the powder processing cylinder 3. The upper rotating mechanism 1 includes two shaping blades 6, and the central rotating shaft is connected to the drive motor 5 outside the powder processing cylinder 3. It can rotate at high speed under the drive of the drive motor 5. The drive motor 5 of the upper rotating mechanism 1 can switch between forward and reverse rotation, that is, the rotation direction of the upper rotating mechanism 1 and the lower rotating mechanism 2 can be the same or opposite. There is a 10mm gap between the shaping blade 6 of the upper rotating mechanism 1 and the outer shell of the powder processing cylinder. The distance between the upper rotating mechanism 1 and the lower rotating mechanism 2 is 30mm.

[0038] The powder processing cylinder 3 is an inverted cone shape, and the stirring blades 7 of the lower rotating mechanism 1 form a certain angle (135°) with the direction of rotation. The shaping blades 6 of the upper rotating mechanism 1 include two inclined surfaces, one of which is flat and the other is wavy. When the upper rotating mechanism 1 rotates, the two inclined surfaces form different angles with the direction of rotation, one being an acute angle (60°) and the other an obtuse angle (120°). The drive motors of the upper rotating mechanism 1 and the lower rotating mechanism 2 are variable frequency motors with adjustable speed. The speed adjustment range of the upper rotating mechanism 1 is 0-4000 r / min, and the speed adjustment range of the lower rotating mechanism 2 is 0-2000 r / min.

[0039] The powder post-processing using the apparatus of this embodiment includes the following steps:

[0040] Step 1: The powder to be processed is put into the powder processing cylinder 3 through the feeding inlet. The height of the powder is higher than the upper edge of the stirring blade of the lower rotating mechanism 2 and lower than the bottom edge of the shaping blade 6 of the upper rotating mechanism 1.

[0041] Step 2: Connect a vacuum pump to the exhaust port of powder processing cylinder 3, seal the air inlet, and evacuate to below 1000Pa;

[0042] Step 3: Turn on the drive motor 4 of the lower rotating mechanism 2 to make it rotate forward, and set the speed of the lower rotating mechanism 2 to 1500 r / min. Then immediately turn on the drive motor 5 of the upper rotating mechanism 1 to make it rotate in reverse, and set the speed of the upper rotating mechanism to 3500 r / min. Maintain this rotation for 10 minutes. After the time is up, turn off the drive motor 5 of the upper rotating mechanism 1, while the drive motor 4 of the lower rotating mechanism 2 continues to rotate.

[0043] In this step, the stirring blades 7 of the lower rotating mechanism 2 can scoop up and lift the powder during rotation, giving the powder a high initial velocity. The direction of motion of the lifted powder is similar to the rotation direction of the lower rotating mechanism 2. Since the upper rotating mechanism 1 and the lower rotating mechanism 2 rotate in opposite directions, the angle between the inclined surface of the shaping blade 6 facing the rotation direction of the upper rotating mechanism 1 and the direction of motion of the powder lifted by the lower rotating mechanism is almost perpendicular. Furthermore, the relative velocities of the shaping blade 6 and the lifted powder are opposite, resulting in a significant increase in impact energy and achieving a remarkable powder processing effect based on impact crushing. At the same time, in this example, the side of the shaping blade facing the rotation direction is a wavy surface. Powder flying at high speed toward this surface can bounce multiple times on the concave surface, further improving the crushing efficiency.

[0044] Step 4: Change the rotation direction of the upper rotating mechanism 1 to forward rotation, set the speed to 1500 r / min, turn on the drive motor 5 of the upper rotating mechanism 1 again, maintain this rotation for 30 minutes, and then turn off all drive motors. Discharge the processed powder through the discharge port at the bottom of the powder processing cylinder to obtain powder with high powder sphericity and surface smoothness. This can efficiently break up agglomerated powder and satellite powder.

[0045] In this step, the upper rotating mechanism 1 and the lower rotating mechanism 2 rotate in the same direction. The inclined surface of the shaping blade 6 facing the rotation direction of the upper rotating mechanism 1 is similar to the direction of the powder movement of the lower rotating mechanism 2, so as to achieve a powder processing effect mainly based on friction. In addition, the relative speed between the shaping blade 6 and the powder is low, which reduces the energy of the collision. Therefore, it can remove the sharp edges of the powder surface and improve the surface smoothness of the powder.

[0046] Throughout the entire preparation process described above, the stirring blades 7 of the lower rotating mechanism 2 rapidly stir the powder in the powder processing cylinder 3, which enables friction between powder particles and significantly improves the surface finish of the powder.

[0047] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A powder processing method for improving sphericity and surface finish of a powder, characterized by, A powder processing device for improving the sphericity and surface finish of powder, The powder processing device comprises a powder processing cylinder and a plurality of rotating mechanisms installed inside, the top of the powder processing cylinder is provided with a feeding port and a valve, the bottom is provided with a discharging port and a valve, the rotating mechanisms are divided into upper rotating mechanisms and lower rotating mechanisms, the upper rotating mechanisms comprise 2 or more shaping blades, and the central rotating shaft is connected with a driving motor outside the powder processing cylinder, which can rotate at high speed under the driving of the driving motor, the driving motor of the upper rotating mechanism can realize forward and reverse rotation switching, the lower rotating mechanisms comprise 2 or more stirring blades, and the central rotating shaft is connected with a driving motor outside the powder processing cylinder, which can rotate at high speed under the driving of the driving motor, and there is a spacing of 1-5 cm between the upper rotating mechanisms and the lower rotating mechanisms; The stirring blades of the lower rotating mechanism and the rotating direction form an obtuse angle; The shaping blades of the upper rotating mechanism comprise two positive and negative inclined surfaces, when the upper rotating mechanism rotates, the two inclined surfaces form an acute angle and an obtuse angle with the rotating direction respectively; The powder processing method comprises the following steps: S1, placing the powder to be processed into the powder processing cylinder, the lower limit of the height of the placed powder should exceed half of the stirring blades of the lower rotating mechanism, and the upper limit should not exceed the bottom of the shaping blades of the upper rotating mechanism; S2, vacuumizing the powder processing cylinder or replacing the internal air with inert gas; S3, starting the driving motor of the lower rotating mechanism, defining its rotating direction as forward rotation, setting the rotating speed of the lower rotating mechanism to 500-1500 r / min, then immediately starting the driving motor of the upper rotating mechanism, making it reverse, setting the rotating speed of the upper rotating mechanism to 1000-4000 r / min, the limit rotating speed of the upper rotating mechanism is greater than or equal to that of the lower rotating mechanism, maintaining this rotating state for 10-60 minutes, then closing the driving motor of the upper rotating mechanism, and the driving motor of the lower rotating mechanism keeps rotating all the time; S4, changing the rotating direction of the upper rotating mechanism to forward rotation, setting the rotating speed to 0-3000 r / min, then starting the driving motor of the upper rotating mechanism again, maintaining this rotating state for 10-60 minutes, then closing all the driving motors of the device, and discharging the powder with improved high sphericity and high surface finish.

2. The powder handling method of claim 1, wherein: The upper rotating mechanisms in the powder processing device are composed of one or more same upper rotating mechanisms, which are uniformly arranged on the upper part of the powder processing cylinder.

3. The powder handling method of claim 1, wherein: The surface shape of the shaping blades of the upper rotating mechanism is flat or wavy or porous honeycomb.

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