Apparatus and method for preparing spherical metal powder based on one-by-one atomization method for uniform droplets

1. An apparatus for preparing spherical metal powder, comprising a housing ( 19 ), a crucible ( 5 ) disposed in the housing ( 19 ), and a collection bin ( 13 ) disposed under the housing,

wherein:

the crucible ( 5 ) is disposed at an upper portion of the housing ( 19 ), and the collection bin ( 13 ) is disposed under the crucible ( 5 );

a transmission rod ( 3 ) connected to a piezoelectric ceramic ( 1 ) disposed outside the housing ( 19 ) is disposed in the crucible ( 5 );

a position where the transmission rod ( 3 ) is connected to a top portion of the crucible ( 5 ) is sealed by a dynamic sealing ring ( 2 );

a lower end of the transmission rod ( 3 ) faces towards a center hole at a bottom portion of the crucible ( 5 ), and a perforated plate ( 20 ) having a plurality of holes is disposed at a bottom portion of the center hole; a resistive heater ( 6 ) is disposed about an outer wall of the crucible ( 5 );

a crucible air inlet ( 27 ) extending into the crucible ( 5 ) and a crucible exhaust valve ( 26 ) are disposed at a top portion of the housing ( 19 );

a diffusion pump ( 23 ) and a mechanical pump ( 22 ) are disposed on a side wall of the housing ( 19 );

a cavity air inlet ( 21 ) and a cavity exhaust valve ( 24 ) are disposed on the housing ( 19 ); and a furnace door ( 8 ) is installed on the housing ( 19 ); and

the collection bin ( 13 ) is fixedly connected with the housing ( 19 ) through a support ( 9 );

a through ring-shaped pipe ( 10 ) is disposed between the housing ( 19 ) and the collection bin ( 13 );

a turnplate ( 11 ) is disposed in the collection bin ( 13 ) and below the through ring-shaped pipe ( 10 ); the turnplate ( 11 ) is connected to a motor ( 16 ); a collection tray ( 15 ) is disposed at a bottom of the collection bin ( 13 );

a collection bin door ( 14 ) is installed on a side of the collection bin ( 13 );

wherein the turnplate ( 11 ) comprises:

a T-shaped base having a receiving portion ( 28 ) connected with a support portion ( 29 ); an upper surface of the receiving portion ( 28 ) is provided with a circular groove with a certain radius which is coaxial with the center of the receiving portion; wherein the base is made of a material with a thermal conductivity of less than 20 W/m/k;

an atomization plane ( 30 ) with a disc structure, matching in interference fitting with the circular groove in the receiving portion; wherein the atomization plane ( 30 ) is made of a material having a wetting angle of less than 90° to an atomized droplet ( 18 ); a center of the turnplate of the atomization plane is provided with a concentric circular groove ( 32 ) disposed below the perforated plate ( 20 );

during operation, molten droplets ( 18 ) drop from the crucible through the ring-shaped pipe ( 10 ) onto the concentric circular groove ( 32 ) in the center of the rotating turnplate ( 11 ), spread across the atomization plane under a centrifugal force generated by the rotation of the turnplate, and drop into the collection tray; and

an induction heating coil ( 17 ) is disposed outside the turnplate ( 11 ), configured to heat an upper surface of the turnplate ( 11 ),

wherein the piezoelectric ceramic ( 1 ), the transmission rod ( 3 ), the crucible ( 5 ), the perforated plate ( 20 ), the ring-shaped pipe ( 10 ), the turnplate ( 11 ), the concentric circular groove ( 32 ), and the induction heating coil ( 17 ) are located on a same axis extending from top to bottom of the apparatus, and

wherein, during operation, a material is melted in the crucible, the induction heating coil heats an upper surface of the turnplate to a temperature higher than a melting point of the metal material, molten droplets drop from the crucible through the ring-shaped pipe ( 10 ) onto the concentric circular groove ( 32 ) in the center of the rotating turnplate ( 11 ), spread across the atomization plane under a centrifugal force generated by the rotation of the turnplate, and drop into the collection tray.

2. The apparatus according to claim 1 , wherein a diameter of the center hole of the crucible ( 5 ) is greater than that of the small hole of the perforated plate ( 20 ), and the plurality of holes in the perforated plate have diameters ranging from 0.02 mm to 2.0 mm.

3. The apparatus according to claim 1 , wherein a wetting angle between a material of the perforated plate ( 20 ) and a molten material ( 4 ) in the crucible ( 5 ) is greater than 90° .

4. The apparatus according to claim 1 , wherein a rotational speed of the turnplate ( 11 ) is 10000 rpm to 40000 rpm.

5. The apparatus according to claim 1 , wherein a heating thickness of the induction heating coil ( 17 ) ranges from 5 mm to 20 mm, the induction heating coil ( 17 ) is connected with a converter and a regulated power supply that are disposed outside the housing ( 19 ).

6. A method for preparing spherical metal powder using the apparatus according to claim 1 , comprising the following steps:

S1. charging: grinding a raw material to a preset average particle size and then charging the raw material into the crucible ( 5 ) for sealing;

S2. vacuumizing and heating: vacuumizing the crucible ( 5 ) and the housing ( 19 ) by using the mechanical pump ( 22 ) and the diffusion pump ( 23 ), and filling the crucible ( 5 ) and the housing ( 19 ) with a high-purity inert gas; setting a heating power of a resistive heater ( 6 ) based on a melting point of the raw material to-be-heated, and after a heating temperature reaches the melting point, keeping the temperature to melt the raw material into a melt ( 4 ) completely; manually adjusting a position of the transmission rod ( 3 ), until a preset distance exists between the transmission rod ( 3 ) and the perforated plate ( 20 );

S3 induction heating: with a rotational speed preset, enabling the turnplate ( 11 ) to rotate at a high speed by using the motor ( 16 ), followed by heating an upper surface of the turnplate ( 11 ) rotating at the high speed to a temperature higher than the melting-point of a metal material by using the induction heating coil ( 17 );

S4. preparing the powder: firstly, manually adjusting the position of the transmission rod ( 3 ) to the preset distance from the perforated plate ( 20 ); secondly, injecting a high-purity inert protective gas into the crucible ( 5 ) by using the crucible air inlet ( 27 ) disposed on the housing ( 19 ) and extending into the crucible ( 5 ), to form a positive pressure difference between the inside and the outside of the crucible ( 5 ), thereby driving the melt ( 4 ) to fill the center hole at the bottom of the crucible ( 5 ); and finally, inputting a pulse signal with a wave pattern to the piezoelectric ceramic ( 1 ), wherein the piezoelectric ceramic ( 1 ) produces a downward displacement that is transferred by the transmission rod ( 3 ) connected to the piezoelectric ceramic ( 1 ) to the molten metal in the vicinity of the center hole, so that the molten metal is ejected from the perforated plate ( 20 ) at the bottom of the center hole to form uniform droplets ( 18 );

S5. forming the powder: the uniform droplets ( 18 ) dropping freely on the turnplate ( 11 ) rotating at a high speed through the ring-shaped pipe ( 10 ); the molten uniform droplets ( 18 ) first dropping in the concentric circular groove ( 32 ) in the center of the turnplate ( 11 ), and gradually spreading over the groove; because centrifugal force is small at this time, the droplets will not disperse immediately, but spread in a circle on the turnplate ( 11 ); when the droplets spread in a certain range and the centrifugal force is large enough, spread metal will disperse on the turnplate ( 11 ) in a fiber line shape to an edge of the turnplate ( 11 ) under the action of centrifugal force, and finally split into tiny droplets to fly out; the tiny droplets solidifying without a container in a falling process to form spherical metal powder ( 12 ), and the metal powder falling onto the collection tray ( 15 ); and

S6. collecting the powder: after the preparation is completed, stopping the heating of the resistive heater ( 6 ) and the induction heating coil ( 17 ), and stopping the rotation of the turnplate ( 11 ), turning off the mechanical pump ( 22 ) and the diffusion pump ( 23 ), closing the cavity air inlet ( 21 ), cavity exhaust valve ( 24 ), crucible air inlet ( 27 ), and crucible exhaust valve ( 26 ), opening the collection bin door ( 14 ), and taking out the spherical metal powder ( 12 ) in the collection tray ( 15 ).

7. The method according to claim 6 , wherein the raw material is charged into the crucible ( 5 ) through the furnace door ( 8 ), and a quantity of the charged raw materials accounts for ¼ to ¾ of a capacity of the crucible ( 5 ).

8. The method according to claim 6 , wherein a pressure difference between a crucible cavity of the crucible ( 5 ) and a cavity of the housing ( 19 ) ranges from 50 kPa to 200 kPa.

9. A method for preparing spherical metal powder using the apparatus according to claim 2 , comprising the following steps:

S1. charging: grinding a raw material to a preset average particle size and then charging the raw material into the crucible ( 5 ) for sealing;

S2. vacuumizing and heating: vacuumizing the crucible ( 5 ) and the housing ( 19 ) by using the mechanical pump ( 22 ) and the diffusion pump ( 23 ), and filling the crucible ( 5 ) and the housing ( 19 ) with a high-purity inert gas; setting a heating power of a resistive heater ( 6 ) based on a melting point of the raw material to-be-heated, and after a heating temperature reaches the melting point, keeping the temperature to melt the raw material into a melt ( 4 ) completely; manually adjusting a position of the transmission rod ( 3 ), until a preset distance exists between the transmission rod ( 3 ) and the perforated plate ( 20 );

S3 induction heating: with a rotational speed preset, enabling the turnplate ( 11 ) to rotate at a high speed by using the motor ( 16 ), followed by heating an upper surface of the turnplate ( 11 ) rotating at the high speed to a temperature higher than the melting-point of a metal material by using the induction heating coil ( 17 );

S4. preparing the powder: firstly, manually adjusting the position of the transmission rod ( 3 ) to the preset distance from the perforated plate ( 20 ); secondly, injecting a high-purity inert protective gas into the crucible ( 5 ) by using the crucible air inlet ( 27 ) disposed on the housing ( 19 ) and extending into the crucible ( 5 ), to form a positive pressure difference between the inside and the outside of the crucible ( 5 ), thereby driving the melt ( 4 ) to fill the center hole at the bottom of the crucible ( 5 ); and finally, inputting a pulse signal with a wave pattern to the piezoelectric ceramic ( 1 ), wherein the piezoelectric ceramic ( 1 ) produces a downward displacement that is transferred by the transmission rod ( 3 ) connected to the piezoelectric ceramic ( 1 ) to the molten metal in the vicinity of the center hole, so that the molten metal is ejected from the perforated plate ( 20 ) at the bottom of the center hole to form uniform droplets ( 18 );

S5. forming the powder: the uniform droplets ( 18 ) dropping freely on the turnplate ( 11 ) rotating at a high speed through the ring-shaped pipe ( 10 ); the molten uniform droplets ( 18 ) first dropping in the concentric circular groove ( 32 ) in the center of the turnplate ( 11 ), and gradually spreading over the groove; because centrifugal force is small at this time, the droplets will not disperse immediately, but spread in a circle on the turnplate ( 11 ); when the droplets spread in a certain range and the centrifugal force is large enough, spread metal will disperse on the turnplate ( 11 ) in a fiber line shape to an edge of the turnplate ( 11 ) under the action of centrifugal force, and finally split into tiny droplets to fly out; the tiny droplets solidifying without a container in a falling process to form spherical metal powder ( 12 ), and the metal powder falling onto the collection tray ( 15 ); and

S6. collecting the powder: after the preparation is completed, stopping the heating of the resistive heater ( 6 ) and the induction heating coil ( 17 ), and stopping the rotation of the turnplate ( 11 ), turning off the mechanical pump ( 22 ) and the diffusion pump ( 23 ), closing the cavity air inlet ( 21 ), cavity exhaust valve ( 24 ), crucible air inlet ( 27 ), and crucible exhaust valve ( 26 ), opening the collection bin door ( 14 ), and taking out the spherical metal powder ( 12 ) in the collection tray ( 15 ).

10. A method for preparing spherical metal powder using the apparatus according to claim 3 , comprising the following steps:

S1. charging: grinding a raw material to a preset average particle size and then charging the raw material into the crucible ( 5 ) for sealing;

S2. vacuumizing and heating: vacuumizing the crucible ( 5 ) and the housing ( 19 ) by using the mechanical pump ( 22 ) and the diffusion pump ( 23 ), and filling the crucible ( 5 ) and the housing ( 19 ) with a high-purity inert gas; setting a heating power of a resistive heater ( 6 ) based on a melting point of the raw material to-be-heated, and after a heating temperature reaches the melting point, keeping the temperature to melt the raw material into a melt ( 4 ) completely; manually adjusting a position of the transmission rod ( 3 ), until a preset distance exists between the transmission rod ( 3 ) and the perforated plate ( 20 );

S3 induction heating: with a rotational speed preset, enabling the turnplate ( 11 ) to rotate at a high speed by using the motor ( 16 ), followed by heating an upper surface of the turnplate ( 11 ) rotating at the high speed to a temperature higher than the melting-point of a metal material by using the induction heating coil ( 17 );

S4. preparing the powder: firstly, manually adjusting the position of the transmission rod ( 3 ) to the preset distance from the perforated plate ( 20 ); secondly, injecting a high-purity inert protective gas into the crucible ( 5 ) by using the crucible air inlet ( 27 ) disposed on the housing ( 19 ) and extending into the crucible ( 5 ), to form a positive pressure difference between the inside and the outside of the crucible ( 5 ), thereby driving the melt ( 4 ) to fill the center hole at the bottom of the crucible ( 5 ); and finally, inputting a pulse signal with a wave pattern to the piezoelectric ceramic ( 1 ), wherein the piezoelectric ceramic ( 1 ) produces a downward displacement that is transferred by the transmission rod ( 3 ) connected to the piezoelectric ceramic ( 1 ) to the molten metal in the vicinity of the center hole, so that the molten metal is ejected from the perforated plate ( 20 ) at the bottom of the center hole to form uniform droplets ( 18 );

S5. forming the powder: the uniform droplets ( 18 ) dropping freely on the turnplate ( 11 ) rotating at a high speed through the ring-shaped pipe ( 10 ); the molten uniform droplets ( 18 ) first dropping in the concentric circular groove ( 32 ) in the center of the turnplate ( 11 ), and gradually spreading over the groove; because centrifugal force is small at this time, the droplets will not disperse immediately, but spread in a circle on the turnplate ( 11 ); when the droplets spread in a certain range and the centrifugal force is large enough, spread metal will disperse on the turnplate ( 11 ) in a fiber line shape to an edge of the turnplate ( 11 ) under the action of centrifugal force, and finally split into tiny droplets to fly out; the tiny droplets solidifying without a container in a falling process to form spherical metal powder ( 12 ), and the metal powder falling onto the collection tray ( 15 ); and

S6. collecting the powder: after the preparation is completed, stopping the heating of the resistive heater ( 6 ) and the induction heating coil ( 17 ), and stopping the rotation of the turnplate ( 11 ), turning off the mechanical pump ( 22 ) and the diffusion pump ( 23 ), closing the cavity air inlet ( 21 ), cavity exhaust valve ( 24 ), crucible air inlet ( 27 ), and crucible exhaust valve ( 26 ), opening the collection bin door ( 14 ), and taking out the spherical metal powder ( 12 ) in the collection tray ( 15 ).

11. A method for preparing spherical metal powder using the apparatus according to claim 4 , comprising the following steps:

S1. charging: grinding a raw material to a preset average particle size and then charging the raw material into the crucible ( 5 ) for sealing;

S2. vacuumizing and heating: vacuumizing the crucible ( 5 ) and the housing ( 19 ) by using the mechanical pump ( 22 ) and the diffusion pump ( 23 ), and filling the crucible ( 5 ) and the housing ( 19 ) with a high-purity inert gas; setting a heating power of a resistive heater ( 6 ) based on a melting point of the raw material to-be-heated, and after a heating temperature reaches the melting point, keeping the temperature to melt the raw material into a melt ( 4 ) completely; manually adjusting a position of the transmission rod ( 3 ), until a preset distance exists between the transmission rod ( 3 ) and the perforated plate ( 20 );

S3 induction heating: with a rotational speed preset, enabling the turnplate ( 11 ) to rotate at a high speed by using the motor ( 16 ), followed by heating an upper surface of the turnplate ( 11 ) rotating at the high speed to a temperature higher than the melting-point of a metal material by using the induction heating coil ( 17 );

S4. preparing the powder: firstly, manually adjusting the position of the transmission rod ( 3 ) to the preset distance from the perforated plate ( 20 ); secondly, injecting a high-purity inert protective gas into the crucible ( 5 ) by using the crucible air inlet ( 27 ) disposed on the housing ( 19 ) and extending into the crucible ( 5 ), to form a positive pressure difference between the inside and the outside of the crucible ( 5 ), thereby driving the melt ( 4 ) to fill the center hole at the bottom of the crucible ( 5 ); and finally, inputting a pulse signal with a wave pattern to the piezoelectric ceramic ( 1 ), wherein the piezoelectric ceramic ( 1 ) produces a downward displacement that is transferred by the transmission rod ( 3 ) connected to the piezoelectric ceramic ( 1 ) to the molten metal in the vicinity of the center hole, so that the molten metal is ejected from the perforated plate ( 20 ) at the bottom of the center hole to form uniform droplets ( 18 );

S5. forming the powder: the uniform droplets ( 18 ) dropping freely on the turnplate ( 11 ) rotating at a high speed through the ring-shaped pipe ( 10 ); the molten uniform droplets ( 18 ) first dropping in the concentric circular groove ( 32 ) in the center of the turnplate ( 11 ), and gradually spreading over the groove; because centrifugal force is small at this time, the droplets will not disperse immediately, but spread in a circle on the turnplate ( 11 ); when the droplets spread in a certain range and the centrifugal force is large enough, spread metal will disperse on the turnplate ( 11 ) in a fiber line shape to an edge of the turnplate ( 11 ) under the action of centrifugal force, and finally split into tiny droplets to fly out; the tiny droplets solidifying without a container in a falling process to form spherical metal powder ( 12 ), and the metal powder falling onto the collection tray ( 15 ); and

S6. collecting the powder: after the preparation is completed, stopping the heating of the resistive heater ( 6 ) and the induction heating coil ( 17 ), and stopping the rotation of the turnplate ( 11 ), turning off the mechanical pump ( 22 ) and the diffusion pump ( 23 ), closing the cavity air inlet ( 21 ), cavity exhaust valve ( 24 ), crucible air inlet ( 27 ), and crucible exhaust valve ( 26 ), opening the collection bin door ( 14 ), and taking out the spherical metal powder ( 12 ) in the collection tray ( 15 ).

12. A method for preparing spherical metal powder by using the apparatus according to claim 5 , comprising the following steps:

S1. charging: grinding a raw material to a preset average particle size and then charging the raw material into the crucible ( 5 ) for sealing;

S2. vacuumizing and heating: vacuumizing the crucible ( 5 ) and the housing ( 19 ) by using the mechanical pump ( 22 ) and the diffusion pump ( 23 ), and filling the crucible ( 5 ) and the housing ( 19 ) with a high-purity inert gas; setting a heating power of a resistive heater ( 6 ) based on a melting point of the raw material to-be-heated, and after a heating temperature reaches the melting point, keeping the temperature to melt the raw material into a melt ( 4 ) completely; manually adjusting a position of the transmission rod ( 3 ), until a preset distance exists between the transmission rod ( 3 ) and the perforated plate ( 20 );

S3 induction heating: with a rotational speed preset, enabling the turnplate ( 11 ) to rotate at a high speed by using the motor ( 16 ), followed by heating an upper surface of the turnplate ( 11 ) rotating at the high speed to a temperature higher than the melting-point of a metal material by using the induction heating coil ( 17 );

S4. preparing the powder: firstly, manually adjusting the position of the transmission rod ( 3 ) to the preset distance from the perforated plate ( 20 ); secondly, injecting a high-purity inert protective gas into the crucible ( 5 ) by using the crucible air inlet ( 27 ) disposed on the housing ( 19 ) and extending into the crucible ( 5 ), to form a positive pressure difference between the inside and the outside of the crucible ( 5 ), thereby driving the melt ( 4 ) to fill the center hole at the bottom of the crucible ( 5 ); and finally, inputting a pulse signal with a wave pattern to the piezoelectric ceramic ( 1 ), wherein the piezoelectric ceramic ( 1 ) produces a downward displacement that is transferred by the transmission rod ( 3 ) connected to the piezoelectric ceramic ( 1 ) to the molten metal in the vicinity of the center hole, so that the molten metal is ejected from the perforated plate ( 20 ) at the bottom of the center hole to form uniform droplets ( 18 );

S5. forming the powder: the uniform droplets ( 18 ) dropping freely on the turnplate ( 11 ) rotating at a high speed through the ring-shaped pipe ( 10 ); the molten uniform droplets ( 18 ) first dropping in the concentric circular groove ( 32 ) in the center of the turnplate ( 11 ), and gradually spreading over the groove; because centrifugal force is small at this time, the droplets will not disperse immediately, but spread in a circle on the turnplate ( 11 ); when the droplets spread in a certain range and the centrifugal force is large enough, spread metal will disperse on the turnplate ( 11 ) in a fiber line shape to an edge of the turnplate ( 11 ) under the action of centrifugal force, and finally split into tiny droplets to fly out; the tiny droplets solidifying without a container in a falling process to form spherical metal powder ( 12 ), and the metal powder falling onto the collection tray ( 15 ); and

S6. collecting the powder: after the preparation is completed, stopping the heating of the resistive heater ( 6 ) and the induction heating coil ( 17 ), and stopping the rotation of the turnplate ( 11 ), turning off the mechanical pump ( 22 ) and the diffusion pump ( 23 ), closing the cavity air inlet ( 21 ), cavity exhaust valve ( 24 ), crucible air inlet ( 27 ), and crucible exhaust valve ( 26 ), opening the collection bin door ( 14 ), and taking out the spherical metal powder ( 12 ) in the collection tray ( 15 ).