A system and method for preparing metal powder with controllable microstructure

Abstract

The present invention discloses a system for preparing metal powder with controllable microstructure, the system comprising: a powder making chamber, a rotating electrode, a plasma torch, a powder collecting tank, and a powder transport pipeline, the working surfaces of the rotating electrode and the plasma torch are located in the powder making chamber, the powder making chamber is connected to the powder collecting tank through the powder transport pipeline, and is characterized in that a temperature control system is provided outside the powder collecting tank to control the temperature of the powder collecting tank, and the metal powder is heat treated in the powder collecting tank. The present invention achieves heat treatment of the prepared metal powder by setting a temperature control system in the area through which the metal powder passes during the metal powder preparation process, and heat exchange between the metal powder and a liquid heat exchange medium, thereby obtaining metal powder with controllable microstructure.

Description

Technical Field

[0001] The present invention relates to the field of powder metallurgy, and in particular to a system and method for preparing metal powder with controllable microstructure. Background Art

[0002] With the advancement of science and technology and the need for industrial development, metal powder materials have received more and more attention and have been promoted and applied. Using metal powder materials and 3D printing methods to quickly manufacture personalized metal products has become a new trend. At present, the preparation methods of metal powder materials can be divided into three categories: the reduction method using metal compounds as raw materials to obtain metal powders through decomposition and reduction; the electrolysis method using bulk metal materials as electrodes through electrochemical processes; and the most commonly used atomization method in industry, which liquefies or vaporizes bulk metals by heating and other means, and then quickly cools them under the action of the ambient atmosphere to form metal powders.

[0003] Obtaining metal powders with controllable organizational structures is extremely important and necessary for obtaining metal products with higher and more reliable performance using metal powders. However, to date, the microstructure of metal powders obtained by all metal powder making technologies is based on the organizational structure naturally obtained during the powder making process, and no method has been found to improve the powder making technology from the perspective of microstructure. Summary of the invention

[0004] The purpose of the present invention is to provide a system and method for preparing metal powder with controllable microstructure, so as to solve the problem that the microstructure of powder cannot be controlled in the powder making process of the prior art.

[0005] To solve the above problems, on the one hand, the present invention provides a system for preparing metal powder with controllable microstructure, the system comprising: a powder making chamber, a rotating electrode, a plasma torch, a powder collection tank, and a powder transport pipeline, the working surfaces of the rotating electrode and the plasma torch are located in the powder making chamber, the powder making chamber is connected to the powder collection tank through the powder transport pipeline, a temperature control system is provided outside the powder collection tank to control the temperature of the powder collection tank, and the metal powder is heat treated in the powder collection tank.

[0006] Preferably, the temperature control system includes a heat exchange chamber of a powder collection tank, a liquid heat exchange medium circulation pipeline, and a liquid heat exchange medium constant temperature box. The heat exchange chamber of the powder collection tank is arranged outside the powder collection tank and is connected to the liquid heat exchange medium constant temperature box through the liquid heat exchange medium circulation pipeline to form a liquid heat exchange medium loop.

[0007] Preferably, a heat exchange chamber of the powder making chamber and / or the powder transport pipeline is arranged outside the powder making chamber and / or the powder transport pipeline, and is connected to the liquid heat exchange medium constant temperature box through the liquid heat exchange medium circulation pipeline to form a liquid heat exchange medium loop.

[0008] Preferably, when there is one liquid heat exchange medium thermostat, the liquid heat exchange medium circuit between the liquid heat exchange medium thermostat and the heat exchange chamber of the powder making chamber, the heat exchange chamber of the powder transport pipeline and / or the heat exchange chamber of the powder collection tank is connected in series and / or in parallel.

[0009] Preferably, when the number of the liquid heat exchange medium thermostats is greater than or equal to 2, the heat exchange chamber of the powder making chamber, the heat exchange chamber of the powder transport pipeline and / or the heat exchange chamber of the powder collection tank can be connected to the same or different liquid heat exchange medium thermostats.

[0010] Preferably, the liquid heat exchange medium material is water, or low-temperature liquid nitrogen, liquid helium, liquid ammonia, liquid carbon dioxide, inorganic salt solution, or high-temperature hot oil, molten salt, inorganic salt solution.

[0011] Preferably, the outside of the liquid heat exchange medium circulation pipeline, the heat exchange chamber of the powder collection tank, the heat exchange chamber of the powder making chamber and / or the heat exchange chamber of the powder transport pipeline is wrapped with a heat insulation material.

[0012] Preferably, the powder transport pipeline is extended by 1 to 10 times.

[0013] According to another aspect of the present invention, there is provided a method for preparing metal powder using the system according to the first aspect of the present invention, the method comprising the following steps:

[0014] a. Preparation of the powder making environment: The air in the powder making chamber is extracted using a vacuum system, and then the required inert gas is introduced to a specified pressure;

[0015] b. Start the circulation of liquid heat exchange medium;

[0016] c. Start the rotating electrode for making the powder rod material to start rotating and advancing;

[0017] d. Start the plasma torch to start working;

[0018] e. The arc plasma generated by the plasma torch causes the end of the rotating electrode rod to begin to liquefy. The liquefied metal forms droplets under the action of high-speed rotation and is thrown out. The droplets cool and solidify in an inert gas atmosphere to form a solid powder to be heat treated;

[0019] f. The solid powder to be heat treated first falls onto the wall of the powder making chamber, and then flows through the powder transport pipeline under the action of gravity. During this process, the powder exchanges heat with the liquid heat exchange medium through the wall of the powder making chamber and / or the wall of the powder transport pipeline, and begins to be heat treated;

[0020] g. The solid powder to be treated finally falls into the powder collection tank, and continuously exchanges heat with the liquid heat exchange medium through the wall of the powder collection tank to complete the final heat treatment and obtain metal powder that meets the microstructure requirements;

[0021] h. After the powder making is completed, the plasma torch, the rotating action of the rotating electrode, the liquid heat exchange medium entering the powder making chamber and the heat exchange chamber of the powder transport pipeline are turned off in sequence. After the metal powder entering the powder collection tank has fully completed the heat exchange treatment, the liquid heat exchange medium entering the heat exchange chamber of the powder collection tank is turned off.

[0022] Preferably, the heat exchange chamber of the powder making chamber, the heat exchange chamber of the powder transport pipeline, and the heat exchange chamber of the powder collection tank are respectively connected to the liquid heat exchange medium constant temperature boxes with different temperatures for segmented heat treatment.

[0023] The beneficial effects of the present invention compared to the prior art are as follows: the present invention sets a temperature control system in the area through which the metal powder passes during the metal powder preparation process, realizes heat treatment of the prepared metal powder through heat exchange between the metal powder and the liquid heat exchange medium, obtains metal powder with controllable microstructure, and realizes more precise and reliable application of metal powder by the rotating electrode method, which is of extremely critical significance and necessity for obtaining metal products with higher and more reliable performance using metal powder. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is a schematic structural diagram of a system for preparing metal powder with controllable microstructure according to an embodiment of the present invention;

[0025] Figure 2 It is a schematic structural diagram of a system for preparing metal powder with controllable microstructure according to another embodiment of the present invention.

[0026] Figure Number:

[0027] 1. Powder making chamber; 2. Rotating electrode; 3. Plasma torch; 4. Powder transport pipeline; 5. Powder collecting tank; 6. Heat exchange chamber of powder collecting tank; 7. First liquid heat exchange medium circulation pipeline; 8. First liquid heat exchange medium constant temperature box; 9. Heat exchange chamber of powder making chamber; 10. Second liquid heat exchange medium circulation pipeline; 11. Second liquid heat exchange medium constant temperature box; 12. Heat exchange chamber of powder transport pipeline; 13. Third liquid heat exchange medium circulation pipeline; 14. Third liquid heat exchange medium constant temperature box. DETAILED DESCRIPTION

[0028] The above and other technical features and advantages of the present invention are clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments.

[0029] The system for preparing metal powder with controllable microstructure of the present invention is as follows Figure 1 As shown, the system includes: a powder making chamber 1, a rotating electrode 2, a plasma torch 3, a powder transport pipeline 4 and a powder collecting tank 5. The rotating electrode 2 and the plasma torch 3 are sealed and connected to the powder making chamber 1, and the rotating electrode 2 and the plasma torch 3 are coaxially arranged, and the working surfaces of the two are located in the powder making chamber 1. The powder making chamber 1 is connected to the powder collecting tank 5 through the powder transport pipeline 4. A temperature control system is arranged outside the powder collecting tank 5 to control the temperature of the powder collecting tank 5, and the metal powder is heat treated in the powder collecting tank 5.

[0030] The temperature control system arranged outside the powder collection tank 5 includes a heat exchange chamber 6 of the powder collection tank, a first liquid heat exchange medium circulation pipeline 7, and a first liquid heat exchange medium constant temperature box 8. The heat exchange chamber 6 of the powder collection tank is arranged at the periphery of the powder collection tank 5 and wrapped around the outside of the outer wall of the powder collection tank 5. The heat exchange chamber 6 of the powder collection tank is provided with an inlet and an outlet of the first liquid heat exchange medium, which are respectively connected to the first liquid heat exchange medium circulation pipeline 7, and the first liquid heat exchange medium circulation pipeline 7 is connected to the inlet and outlet of the first liquid heat exchange medium constant temperature box 8 to form a first liquid heat exchange medium loop. A heat exchanger is arranged inside the first liquid heat exchange medium constant temperature box 8, which can store and form a liquid heat exchange medium with stable temperature. The first liquid heat exchange medium flowing out of the first liquid heat exchange medium constant temperature box 8 enters the heat exchange chamber 6 of the powder collection tank through the first liquid heat exchange medium circulation pipe 7. After heat exchange is formed, the temperature of the first liquid heat exchange medium changes and returns to the first liquid heat exchange medium constant temperature box 8 through the first liquid heat exchange medium circulation pipe 7. The original constant temperature is formed again through the heat exchanger in the first liquid heat exchange medium constant temperature box 8, and is output to the heat exchange chamber 6 of the powder collection tank again. The cycle is repeated to maintain the temperature of the first liquid heat exchange medium flowing into the heat exchange chamber 6 of the powder collection tank constant.

[0031] A temperature control system is provided on the outside of the wall of the powder making chamber 1. The structure of the temperature control system is similar to that of the powder collecting tank 5, and includes a heat exchange chamber 9 of the powder making chamber, a second liquid heat exchange medium circulation pipeline 10, and a second liquid heat exchange medium constant temperature box 11. The heat exchange chamber 9 of the powder making chamber is arranged on the periphery of the powder making chamber 1 and wrapped around the outside of the outer wall of the powder making chamber 1. The heat exchange chamber 9 of the powder making chamber is provided with an inlet and an outlet of the second liquid heat exchange medium, which are respectively connected to the second liquid heat exchange medium circulation pipeline 10. The second liquid heat exchange medium circulation pipeline 10 is connected to the inlet and outlet of the second liquid heat exchange medium constant temperature box 11 to form a second liquid heat exchange medium circuit. A heat exchanger is provided in the second liquid heat exchange medium constant temperature box 11, which can store and form a liquid heat exchange medium with stable temperature. The second liquid heat exchange medium circulates back and forth in the heat exchange chamber 9 of the powder making chamber, the second liquid heat exchange medium circulation pipe 10, and the second liquid heat exchange medium constant temperature box 11 to maintain a constant temperature of the second liquid heat exchange medium flowing into the heat exchange chamber 9 of the powder making chamber.

[0032] A temperature control system is provided on the outside of the wall of the powder transport pipeline 4. The structure of the temperature control system is similar to that of the powder collection tank 5, and includes a heat exchange chamber 12 of the powder transport pipeline, a third liquid heat exchange medium circulation pipeline 13, and a third liquid heat exchange medium constant temperature box 14. The heat exchange chamber 12 of the powder transport pipeline is provided on the periphery of the powder transport pipeline 4 and wrapped around the outside of the outer wall of the powder transport pipeline 4. The heat exchange chamber 12 of the powder transport pipeline is provided with an inlet and an outlet of the third liquid heat exchange medium, which are respectively connected to the third liquid heat exchange medium circulation pipeline 13. The third liquid heat exchange medium circulation pipeline 13 is connected to the inlet and outlet of the third liquid heat exchange medium constant temperature box 14 to form a third liquid heat exchange medium loop. A heat exchanger is provided in the third liquid heat exchange medium constant temperature box 14, which can store and form a liquid heat exchange medium with stable temperature. The third liquid heat exchange medium circulates back and forth in the heat exchange chamber 12 of the powder transport pipeline, the third liquid heat exchange medium circulation pipeline 13, and the third liquid heat exchange medium constant temperature box 14 to maintain a constant temperature of the third liquid heat exchange medium flowing into the heat exchange chamber 12 of the powder transport pipeline.

[0033] Compared with the powder transport pipeline of the conventional metal powder preparation device, the present invention extends the length of the powder transport pipeline 4 by 1 to 10 times, which can increase the passing time of the powder in the powder transport pipeline 4, that is, prolongs the heat treatment time of the metal powder in the powder transport pipeline 4.

[0034] The temperature control systems of the powder making chamber 1 and the powder transport pipeline 4 are determined according to the microstructure required for the metal powder to be prepared. A temperature control system may be not provided, one of them, or both of them may be provided.

[0035] The number of liquid heat exchange medium thermostats is determined according to the relationship between the heat treatment process and the microstructure of the metal material to be prepared. If heat treatment is only required at one temperature, one liquid heat exchange medium thermostat is required, and the liquid heat exchange medium circuit between the liquid heat exchange medium thermostat and the heat exchange chamber 9 of the powder making chamber, the heat exchange chamber 12 of the powder transport pipeline, and / or the heat exchange chamber 6 of the powder collection tank is connected in series and / or in parallel.

[0036] If the metal powder needs to be heat treated in different temperature zones, a corresponding number of liquid heat exchange media are required. The liquid heat exchange medium circuits between the heat exchange chamber 9 of the powder making chamber, the heat exchange chamber 12 of the powder transport pipeline and / or the heat exchange chamber 6 of the powder collection tank can be connected to the same liquid heat exchange medium thermostat or to different liquid heat exchange medium thermostats. Figure 1 As shown, the heat exchange chamber 6 of the powder collection tank, the heat exchange chamber 9 of the powder making chamber and the heat exchange chamber 12 of the powder transport pipeline are respectively connected to different liquid heat exchange medium thermostats. Figure 2 As shown, the heat exchange chamber 12 of the powder transport pipeline and the heat exchange chamber 6 of the powder collection tank are connected in series, and both share the first liquid heat exchange medium constant temperature box 8; the heat exchange chamber 9 of the powder making chamber is separately connected to the third liquid heat exchange medium constant temperature box 14.

[0037] If the segmented heat treatment exceeds three stages, different heat exchange chambers can be provided on the powder transport pipeline 4 to achieve this.

[0038] The liquid heat exchange medium material is water, or low-temperature liquid nitrogen, liquid helium, liquid ammonia, liquid carbon dioxide, inorganic salt solution, or high-temperature hot oil, molten salt, inorganic salt solution. All liquid heat exchange medium materials that have fluid properties, can circulate in the heat exchange chamber, and have no obvious or high-speed destructive effect on the liquid heat exchange medium circuit material can be used as liquid heat exchange medium materials. The temperature of the medium in the liquid heat exchange medium thermostat is different due to the different liquid heat exchange medium materials used. The constant temperature of high-temperature medium, such as hot oil, is as high as hundreds of degrees; low-temperature medium, such as liquid nitrogen, is hundreds of degrees below zero; normal temperature medium, such as water or aqueous solution, is between several degrees below zero and tens of degrees. The method of achieving constant temperature of liquid heat exchange medium in the liquid heat exchange medium thermostat is the same as the method of forming the temperature of the medium. For example, for high-temperature liquid heat exchange medium such as hot oil, a heating method is used; for ice water medium, a compressor refrigeration method is used; for ultra-low temperature medium such as liquid nitrogen, an adiabatic expansion method is used. The flow rate of the liquid heat exchange medium during the circulation process is determined according to the heat exchange power. Generally, the flow rate of the liquid heat exchange medium is required to have at least the heat flow capacity required for the minimum heat exchange power. For example, during the powder making process of the rotating electrode 2, if the input power of the plasma torch 3 is 100kW, if it is calculated according to the heat treatment principle that 20kW of the power needs to be dissipated through heat exchange, then the overall heat removal capacity of the designed liquid heat exchange medium system is at least 20kW. If the power density of the liquid heat exchange medium for removing heat is 1kW / L·s, the required flow rate of the liquid heat exchange medium is 20L / s.

[0039] When the temperature of the liquid heat exchange medium is significantly different from the ambient temperature, it is necessary to wrap the outside of the circuit through which the liquid heat exchange medium flows, including the liquid heat exchange medium circulation pipeline, the heat exchange chamber 6 of the powder collection tank, the heat exchange chamber 9 of the powder making chamber and / or the heat exchange chamber 12 of the powder transport pipeline, with insulation material to reduce energy consumption.

[0040] According to another aspect of the present invention, there is provided a method for preparing a metal powder with controllable microstructure using the system according to the first aspect of the present invention, the method comprising the following steps:

[0041] a. Preparation of the powder making environment: The air in the powder making chamber 1 is extracted by a vacuum system, and then the required inert gas is introduced to a specified pressure;

[0042] b. Start the circulation of liquid heat exchange medium;

[0043] c. Start the rotating electrode 2 for making the powder rod material to be made and start rotating and advancing;

[0044] d. Start the plasma torch 3 to start working;

[0045] e. The arc plasma generated by the plasma torch 3 causes the end of the rotating electrode 2 bar to begin to liquefy, and the liquefied metal forms droplets under the action of high-speed rotation and is thrown out. The droplets cool and solidify in an inert gas atmosphere to form a solid powder to be heat treated;

[0046] f. The solid powder to be heat treated first falls onto the wall of the powder making chamber 1, and then flows through the powder transport pipe 4 under the action of gravity. During this process, the powder exchanges heat with the liquid heat exchange medium through the wall of the powder making chamber 1 and / or the wall of the powder transport pipe 4, and begins heat treatment;

[0047] g. The solid powder to be treated finally falls into the powder collecting tank 5, and continuously exchanges heat with the liquid heat exchange medium through the wall of the powder collecting tank 5, completing the final heat treatment to obtain a metal powder that meets the microstructure requirements;

[0048] h. After the powder making is completed, the plasma torch 3, the rotating action of the rotating electrode 2, the liquid heat exchange medium in the heat exchange chamber 9 of the powder making chamber and the heat exchange chamber 12 of the powder transport pipeline are turned off in sequence. After the metal powder entering the powder collection tank 5 has fully completed the heat treatment, the liquid heat exchange medium in the heat exchange chamber 6 of the powder collection tank is turned off.

[0049] Before using the system for preparing metal powder with controllable microstructure, first determine the microstructure required for the metal powder to be prepared; determine the type of liquid heat exchange medium required in the metal powder preparation process and the required temperature based on the relationship between the heat treatment process and the microstructure of the metal material to be prepared; obtain the time required for the powder to form solid particles and reach the required heat treatment temperature based on the particle size characteristics of the metal powder to be prepared; determine the contact area between the liquid heat exchange medium and the powder making mechanism based on the required heat treatment time; if staged heat treatment is required, the heat exchange chamber 9 of the powder making chamber, the heat exchange chamber 12 of the powder transport pipeline and / or the heat exchange chamber of the powder collection tank 5 are respectively connected to constant temperature boxes with liquid heat exchange media at different temperatures for staged heat treatment.

[0050] Embodiment 1:

[0051] refer to Figure 2, taking the preparation of 45# carbon steel powder with quenched microstructure as an example. The system for preparing metal powder with controllable microstructure includes: a powder making chamber 1, a rotating electrode 2, a plasma torch 3, a powder transport pipeline 4 and a powder collection tank 5. The powder making chamber 1 is made of stainless steel, with a vertical cylindrical structure of 2000mm in diameter and 500mm in height, and is placed sideways. The diameter of the raw material bar input by the rotating electrode 2 is 80mm, the maximum input power of the plasma torch 3 is 300kW, and the rotating electrode 2 and the plasma torch 3 are installed at the center of the circular plane of the powder making chamber 1, facing each other. The length of the transport pipeline is 2000mm, the upper part of the transport pipeline is located at the bottom of the powder making chamber 1, and the lower part of the transport pipeline is connected to the powder collection tank 5.

[0052] The powder collection tank 5 is provided with a temperature control system outside, including a heat exchange chamber 6 of the powder collection tank, a first liquid heat exchange medium circulation pipeline 7, and a first liquid heat exchange medium thermostat 8. The heat exchange chamber 6 of the powder collection tank and the heat exchange chamber 12 of the powder transportation pipeline are connected in series, and the two share the first liquid heat exchange medium thermostat 8. The first liquid heat exchange medium is liquid nitrogen, and the temperature of the liquid nitrogen is maintained at -196°C. The liquid nitrogen flowing out of the first liquid heat exchange medium thermostat 8 enters the heat exchange chamber 6 of the powder collection tank through the first liquid heat exchange medium circulation pipeline 7, and then enters the heat exchange chamber 12 of the powder transportation pipeline. After heat exchange, the temperature of the liquid nitrogen changes and returns to the first liquid heat exchange medium thermostat 8 through the first liquid heat exchange medium circulation pipeline 7. The original constant temperature is formed again through the heat exchanger in the first liquid heat exchange medium thermostat 8, and then output to the heat exchange chamber 6 of the powder collection tank again, and the cycle is repeated to form a first liquid heat exchange medium loop. In order to reduce energy loss, the first liquid heat exchange medium circulation pipeline 7, the heat exchange chamber 6 of the powder collection tank, and the heat exchange chamber 12 of the powder transport pipeline are wrapped with heat insulation materials.

[0053] The temperature control system of the powder making chamber 1 includes a heat exchange chamber 9 of the powder making chamber, a second liquid heat exchange medium circulation pipeline 10, and a second liquid heat exchange medium thermostat 11. The second liquid heat exchange medium is water, and the second liquid heat exchange medium thermostat 11 uses a water chiller to maintain the water temperature at 27°C. The water flowing out of the second liquid heat exchange medium thermostat 11 enters the heat exchange chamber 9 of the powder making chamber through the second liquid heat exchange medium circulation pipeline 10. After heat exchange, the water temperature changes and returns to the second liquid heat exchange medium thermostat 11 through the second liquid heat exchange medium circulation pipeline 10. The original constant temperature is formed again in the second liquid heat exchange medium thermostat 11 through the water chiller, and then output to the heat exchange chamber 9 of the powder making chamber again, and the cycle is repeated to form a second liquid heat exchange medium loop.

[0054] The milling process is:

[0055] The processed 45# carbon steel bar is installed on the rotating electrode 2, and the air in the powder making chamber 1 is removed by vacuuming, and then argon gas is introduced until the pressure in the powder making chamber 1 reaches 1.5 atmospheres. The bar rotation speed is 80,000 rpm, the working power of the plasma torch 3 is 100kW, the tungsten electrode of the plasma torch 3 and the end of the bar are kept at a distance of 5cm, and the bar is continuously fed toward the plasma torch 3 by a stepper motor, and the feed rate is 2mm / s. During the process, the pressure in the powder making chamber 1 remains unchanged at 1.8 atmospheres, the flow rate of circulating water is 5t / h, and the circulation flow rate of liquid nitrogen is 10L / min.

[0056] The arc plasma generated by the plasma torch 3 causes the end of the rotating electrode 2 rod to begin to liquefy. The liquefied metal forms droplets under the action of high-speed rotation and is thrown out. The droplets cool and solidify in the argon atmosphere to form a solid powder to be heat treated. The solid powder to be heat treated first falls on the wall of the powder making chamber 1, and then flows through the powder transport pipeline 4 under the action of gravity. During this process, the powder exchanges heat with the liquid heat exchange medium through the wall of the powder making chamber 1 and the wall of the powder transport pipeline 4, and begins heat treatment. The solid powder to be treated finally falls into the powder collection tank 5, and continues to exchange heat with the liquid heat exchange medium through the wall of the powder collection tank 5, completing the final heat treatment and obtaining a metal powder that meets the microstructure requirements.

[0057] After the powder making is completed, the plasma torch 3, the rotating action of the rotating electrode 2, the liquid heat exchange medium in the heat exchange chamber 9 of the powder making chamber and the heat exchange chamber 12 of the powder transport pipeline are turned off in sequence; after the metal powder entering the powder collection tank 5 has fully completed the heat treatment, the liquid heat exchange medium in the heat exchange chamber 6 of the powder collection tank is turned off.

[0058] The obtained metal powder was analyzed using optical and electron microscopes, and it was found that the obtained powder had a typical martensitic structure; its strength was tested using a microhardness tester and the results showed that the hardness of the powder reached a Vickers hardness of 1000 Hv, which is much higher than the hardness obtained by the conventional atomization method.

[0059] The present invention sets a temperature control system in the area passed by the metal powder during the preparation process, and realizes heat treatment of the obtained metal powder through heat exchange between the metal powder and the liquid heat exchange medium, thereby obtaining metal powder with controllable microstructure, and realizing more accurate and reliable application of metal powder by the rotating electrode method. It is of extremely critical significance and necessity for using metal powder to obtain metal products with higher and more reliable performance.

[0060] The specific embodiments described above further describe the purpose, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. It is particularly pointed out that for those skilled in the art, any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the scope of protection of the present invention.

[0061] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0062] Unless otherwise specifically stated, the relative arrangement of the parts and steps described in these embodiments, numerical expressions and numerical values ​​do not limit the scope of the present invention. At the same time, it should be understood that, for ease of description, the sizes of the various parts shown in the accompanying drawings are not drawn according to the actual proportional relationship. The technology, method and equipment known to ordinary technicians in the relevant field may not be discussed in detail, but in appropriate cases, the technology, method and equipment should be regarded as a part of the authorization specification. In all examples shown and discussed here, any specific value should be interpreted as being merely exemplary, rather than as a limitation. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters represent similar items in the following drawings, so once a certain item is defined in an accompanying drawing, it does not need to be further discussed in subsequent drawings.

[0063] In the description of the present invention, it is necessary to understand that the directions or positional relationships indicated by directional words such as "front, back, up, down, left, right", "lateral, vertical, perpendicular, horizontal" and "top, bottom" are usually based on the directions or positional relationships shown in the drawings. They are only for the convenience of describing the present invention and simplifying the description. Unless otherwise specified, these directional words do not indicate or imply that the devices or elements referred to must have a specific direction or be constructed and operated in a specific direction. Therefore, they cannot be understood as limiting the scope of protection of the present invention. The directional words "inside and outside" refer to the inside and outside relative to the contours of each component itself.

[0064] For ease of description, spatially relative terms such as "above", "above", "on the upper surface of", "above", etc. may be used here to describe the spatial positional relationship between a device or feature and other devices or features as shown in the figure. It should be understood that spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation described in the figure. For example, if the device in the accompanying drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be positioned as "below other devices or structures" or "below other devices or structures". Thus, the exemplary term "above" can include both "above" and "below". The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatially relative descriptions used here are interpreted accordingly.

[0065] In addition, it should be noted that the use of terms such as "first" and "second" to limit components is only for the convenience of distinguishing the corresponding components. If not otherwise stated, the above terms have no special meaning and therefore cannot be understood as limiting the scope of protection of the present invention.

Claims

1. A system for preparing metal powder with controllable microstructure, the system comprising: A powder making chamber, a rotating electrode, a plasma torch, a powder collecting tank, and a powder transport pipeline, wherein the working surfaces of the rotating electrode and the plasma torch are located in the powder making chamber, and the powder making chamber is connected to the powder collecting tank through the powder transport pipeline. It is characterized in that a temperature control system is arranged outside the powder collecting tank to control the temperature of the powder collecting tank, and the metal powder is heat treated in the powder collecting tank; the temperature control system comprises a heat exchange chamber of the powder collecting tank, a liquid heat exchange medium circulation pipeline, and a liquid heat exchange medium thermostat of the powder collecting tank; the heat exchange chamber of the powder collecting tank is arranged outside the powder collecting tank, and is connected to the liquid heat exchange medium thermostat through the liquid heat exchange medium circulation pipeline to form a liquid heat exchange medium loop.

2. The system for preparing metal powder with controllable microstructure according to claim 1, characterized in that: A heat exchange chamber of the powder making chamber and / or the powder transporting pipeline is arranged outside the powder making chamber and / or the powder transporting pipeline, and is connected to the liquid heat exchange medium constant temperature box through the liquid heat exchange medium circulation pipeline to form a liquid heat exchange medium loop.

3. The system for preparing metal powder with controllable microstructure according to claim 2, characterized in that: When there is one liquid heat exchange medium thermostat, the liquid heat exchange medium circuit between the liquid heat exchange medium thermostat and the heat exchange chamber of the powder making chamber, the heat exchange chamber of the powder transport pipeline and / or the heat exchange chamber of the powder collection tank is connected in series and / or in parallel.

4. The system for preparing metal powder with controllable microstructure according to claim 2, characterized in that: When the number of the liquid heat exchange medium thermostats is greater than or equal to 2, the heat exchange chamber of the powder making chamber, the heat exchange chamber of the powder transport pipeline and / or the heat exchange chamber of the powder collection tank are connected to the same or different liquid heat exchange medium thermostats.

5. The system for preparing metal powder with controllable microstructure according to any one of claims 2 to 4, characterized in that: The liquid heat exchange medium material is water, or low-temperature liquid nitrogen, liquid helium, liquid ammonia, liquid carbon dioxide, inorganic salt solution, or high-temperature hot oil, molten salt, inorganic salt solution.

6. The system for preparing metal powder with controllable microstructure according to any one of claims 2 to 4, characterized in that: The liquid heat exchange medium circulation pipeline, the heat exchange chamber of the powder collection tank, the heat exchange chamber of the powder making chamber and / or the heat exchange chamber of the powder transport pipeline are wrapped with heat insulation material.

7. The system for preparing metal powder with controllable microstructure according to claim 1, characterized in that: The powder transport pipeline is extended by 1 to 10 times.

8. A method for preparing metal powder using the microstructure controllable system according to any one of claims 1 to 7, characterized in that: The method comprises the following steps: a. Preparation of the powder making environment: The air in the powder making chamber is extracted using a vacuum system, and then the required inert gas is introduced to a specified pressure; b. Start the circulation of liquid heat exchange medium; c. Start the rotating electrode for making the powder rod material to start rotating and advancing; d. Start the plasma torch to start working; e. The arc plasma generated by the plasma torch causes the end of the rotating electrode rod to begin to liquefy. The liquefied metal forms droplets under the action of high-speed rotation and is thrown out. The droplets cool and solidify in an inert gas atmosphere to form a solid powder to be heat treated; f. The solid powder to be heat treated first falls onto the wall of the powder making chamber, and then flows through the powder transport pipeline under the action of gravity. During this process, the powder exchanges heat with the liquid heat exchange medium through the wall of the powder making chamber and / or the wall of the powder transport pipeline, and the heat treatment begins; g. The solid powder to be treated finally falls into the powder collection tank, and continuously exchanges heat with the liquid heat exchange medium through the wall of the powder collection tank to complete the final heat treatment and obtain metal powder that meets the microstructure requirements; h. After the powder making is completed, the plasma torch, the rotating action of the rotating electrode, the liquid heat exchange medium entering the powder making chamber and the heat exchange chamber of the powder transport pipeline are turned off in sequence. After the metal powder entering the powder collection tank has fully completed the heat exchange treatment, the liquid heat exchange medium entering the heat exchange chamber of the powder collection tank is turned off.

9. The method for preparing metal powder with controllable microstructure according to claim 8, characterized in that: The heat exchange chamber of the powder making chamber, the heat exchange chamber of the powder transport pipeline, and the heat exchange chamber of the powder collecting tank are respectively connected to the liquid heat exchange medium thermostats with different temperatures to perform segmented heat treatment.

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