A powder pre-treatment system and method

Abstract

The application relates to a powder pretreatment system and method, and relates to the technical field of powder metallurgy sintering. The powder pretreatment system is internally provided with a partition plate for separating a pretreatment box into a heating chamber and a cooling chamber, a pretreatment unit is detachably arranged in the heating chamber or the cooling chamber, can slide between the heating chamber and the cooling chamber, and comprises a receiving cavity for containing powder to be treated, a plurality of metal balls are arranged in the receiving cavity, and a driving unit is used for driving the pretreatment box and the pretreatment unit to synchronously rotate. When the pretreatment box and the pretreatment unit of the powder pretreatment system provided by the application synchronously rotate, the pretreatment powder and the metal balls in the receiving cavity are continuously stirred, sintering of the pretreatment powder in the heating and sintering process can be avoided, the particle size and the fluidity of the pretreatment powder are ensured, meanwhile, the cooling efficiency of the pretreatment powder is improved, and the problems of secondary phase precipitation and excessively high hardness caused by slow cooling speed are avoided.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of powder metallurgy sintering, in particular to a powder pretreatment system and method. BACKGROUND

[0002] Currently, in the cold spraying additive process, the powder needs to have uniform size, certain fluidity, high plasticity and low hardness to achieve efficient deposition. Since the throat structure of the cold spraying Laval nozzle is convergent, excessive hardness of the sprayed powder will increase the wear of the Laval nozzle throat, so the powder needs to be in a soft state during spraying to reduce the wear of the nozzle throat and improve the mechanical bonding strength of the cold sprayed coating. The hardness of alloy powder is related to the preparation process, and the powder hardness is usually high, the cold spraying deposition critical speed is large, and the deposition is difficult, which often cannot meet the requirements. Therefore, it is necessary to use a heat treatment method to regulate and control the mechanical properties of the cold sprayed powder to obtain soft high-fluidity metal powder to improve the deposition efficiency and bonding strength.

[0003] In related technologies, the heat treatment method is high-temperature solid solution process or high-temperature annealing of structural steel. The high-temperature solid solution or high-temperature annealing heat treatment process can soften the metal material, but the powder is easy to sinter during high-temperature treatment. That is, traditional rotary kiln heat treatment or traditional vacuum furnace heat treatment, the powders will diffuse and connect at high temperature to form sintered lumps, affecting the particle size and fluidity of the powder, which cannot meet the requirements of cold spraying. At the same time, due to the poor heat transfer performance of the powder, the heating crucible has large heat capacity, and the cooling speed is slow, so non-ferrous metal powder cannot be rapidly cooled, and the powder raw material cannot be heat treated to soften. SUMMARY

[0004] The embodiments of the present application provide a powder pretreatment system and method to solve the problem that in related technologies, when rotary kiln heat treatment or traditional vacuum furnace heat treatment is used, the powders will diffuse and connect at high temperature to form sintered lumps, affecting the particle size and fluidity of the powder, which cannot meet the requirements of cold spraying.

[0005] In a first aspect, a powder pretreatment system is provided, which includes:

[0006] A pretreatment box body having a partition plate movably arranged therein, the partition plate separating the pretreatment box body into a heating chamber and a cooling chamber;

[0007] At least one pretreatment unit is detachably arranged in the heating chamber or the cooling chamber and can slide between the heating chamber and the cooling chamber, the pretreatment unit including a receiving cavity for receiving the powder to be treated, the receiving cavity having a plurality of metal balls arranged therein;

[0008] a driving unit connected with the pre-treatment box or the pre-treatment unit for driving the pre-treatment box and the pre-treatment unit to rotate synchronously.

[0009] In some embodiments, the pre-treatment unit is provided with a first through hole along its length direction, and the accommodating cavity is annular.

[0010] Both ends of the pre-treatment unit are provided with a first connecting part, and both ends of the pre-treatment box are provided with a second connecting part. Each second connecting part is connected with the pre-treatment box and the first connecting part on the same side of the second connecting part, and each second connecting part is provided with a second through hole.

[0011] In some embodiments, each first connecting part is provided with at least one extension piece, which can at least partially extend from the second connecting part on the same side of the extension piece.

[0012] The driving unit comprises a driving shaft, which is arranged through the first through hole and extends from the heating chamber and the cooling chamber at both ends. The driving shaft is connected with the extension piece and is used to drive the pre-treatment box and the pre-treatment unit to rotate synchronously through the extension piece.

[0013] In some embodiments, the pre-treatment unit further comprises at least two connecting pieces. Each connecting piece is arranged through the driving shaft and at least one extension piece in sequence to connect the pre-treatment unit and the driving shaft.

[0014] In some embodiments, the partition plate is arranged on the top of the pre-treatment box. The partition plate is provided with an avoiding slot for avoiding the driving shaft. The avoiding slot is provided with a heat preservation piece along its inner wall.

[0015] In some embodiments, the powder pre-treatment system further comprises a support frame connected with the driving shaft extending from the heating chamber and the cooling chamber. The driving shaft extending from one end of the pre-treatment box is provided with a brake unit and a speed changing unit.

[0016] In some embodiments, the pre-treatment unit is provided with a vacuum extraction interface and an air filling interface respectively connected with the accommodating cavity.

[0017] The pre-treatment unit is further provided with a cooling flow channel distributed along its outer peripheral surface. The cooling flow channel comprises an inlet.

[0018] In some embodiments, the metal ball is made of the same material as the powder to be treated.

[0019] The diameter of the metal ball ranges from 3mm to 7mm.

[0020] In some embodiments, the pre-treatment box is provided with a heat insulation layer, the heating chamber is provided with a temperature raising assembly, and the cooling chamber is provided with a temperature monitoring assembly.

[0021] In a second aspect, a method for using the powder pre-treatment system is provided, and the method comprises the following steps:

[0022] Placing the powder to be treated and the plurality of metal balls into the receiving cavity of the pre-treatment unit;

[0023] Fixing the pre-treatment unit in the heating chamber, performing vacuumizing treatment on the receiving cavity, and filling the receiving cavity with protective gas after vacuumizing;

[0024] Driving the pre-treatment unit and the pre-treatment box to rotate synchronously, heating the pre-treatment unit, opening the partition plate after the heating is completed, sliding the pre-treatment unit to the cooling chamber, closing the partition plate, and driving the pre-treatment unit and the pre-treatment box to rotate synchronously again to cool the pre-treatment unit.

[0025] The technical scheme provided by the application has the following beneficial effects:

[0026] The powder pre-treatment system provided by the application is characterized in that the pre-treatment box is provided with a partition plate separating the pre-treatment box into a heating chamber and a cooling chamber, the pre-treatment unit is detachably arranged in the heating chamber or the cooling chamber and can slide between the heating chamber and the cooling chamber, the pre-treatment unit comprises a receiving cavity for receiving the powder to be treated, the receiving cavity is provided with a plurality of metal balls, and the driving unit is used to drive the pre-treatment box and the pre-treatment unit to rotate synchronously. BRIEF DESCRIPTION OF DRAWINGS

[0027] In order to more clearly illustrate the technical scheme in the embodiments of the application, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the application, and other drawings can be obtained by those skilled in the art without creative effort.

[0028] Figure 1 The structure diagram of the powder pre-treatment system provided by the application is shown in the figure.

[0029] Figure 2A vertical sectional view of a pretreatment unit of a powder pretreatment system provided by the embodiment of the present application is shown in the figure.

[0030] Figure 3 A side view of a pretreatment unit of a powder pretreatment system provided by the embodiment of the present application is shown in the figure.

[0031] In the figure: 1 - pretreatment box, 10 - partition plate, 11 - heating chamber, 12 - cooling chamber, 13 - second connecting part, 14 - thermal insulation layer, 15 - temperature rising assembly, 16 - temperature monitoring assembly, 2 - pretreatment unit, 20 - first through hole, 21 - first connecting part, 22 - extension piece, 23 - connecting piece, 24 - vacuum extraction interface, 25 - air charging interface, 26 - cooling flow channel, 3 - driving unit, 30 - driving shaft, 31 - brake unit, 32 - speed changing unit, 33 - driving motor, 4 - support frame. DETAILED DESCRIPTION

[0032] To make the objectives, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described below in connection with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of protection of the present application.

[0033] The embodiment of the present application provides a powder pretreatment system, which can solve the problem that, in the related art, when a rotary kiln furnace heat treatment or a traditional vacuum furnace heat treatment is used, diffusion connection occurs among powders at high temperature, sintered clumps are formed, powder particle size and flowability are affected, and cold spraying requirements cannot be met.

[0034] Referring to Figure 1As shown, the powder pretreatment system mainly comprises a pretreatment box 1, at least one pretreatment unit 2 and a driving unit 3. The pretreatment box 1 is movably provided with a partition plate 10, which divides the pretreatment box 1 into a heating chamber 11 and a cooling chamber 12. The partition plate 10 can be inserted into the pretreatment box 1 to divide the pretreatment box 1 into the heating chamber 11 and the cooling chamber 12 by being pulled out in the vertical direction. Alternatively, the partition plate 10 can be rotatably arranged in the pretreatment box 1, one end of the partition plate 10 is rotatably connected to the pretreatment box 1, and the other end is a movable end. Under the action of an external force, the partition plate 10 can rotate in the pretreatment box 1 to communicate the heating chamber 11 and the cooling chamber 12. The pretreatment unit 2 is detachably arranged in the heating chamber 11 or the cooling chamber 12 and can slide between the heating chamber 11 and the cooling chamber 12. The pretreatment unit 2 comprises a receiving cavity for receiving the powder to be treated, and a plurality of metal balls are arranged in the receiving cavity. The driving unit 3 is connected to the pretreatment box 1 or the pretreatment unit 2 to drive the pretreatment box 1 and the pretreatment unit 2 to rotate synchronously. During rotation, the metal balls mix with the powder to be treated and rotate together in the receiving cavity, so that the powder is uniformly heated and sintering of the powder is prevented. After heating, the pretreatment unit 2 in the heating chamber 11 is moved to the cooling chamber 12 for cooling. The metal balls can accelerate the cooling of the powder. After the cooling reaches room temperature, the powder is discharged from the furnace, and the powder solid solution treatment is completed. The pretreatment powder and the metal balls in the receiving cavity of the powder pretreatment system are continuously stirred during heating and cooling, which can effectively prevent sintering of the pretreatment powder during heating and sintering, ensure the particle size and flowability of the pretreatment powder, and also accelerate the cooling efficiency of the pretreatment powder, avoid slow cooling speed leading to secondary phase precipitation, and prevent high hardness.

[0035] Further, the pretreatment unit 2 is provided with a first through hole 20 along the length direction of the pretreatment unit 2, the first through hole 20 penetrates the pretreatment unit 2 along the length direction of the pretreatment unit 2, so that the receiving cavity is annular, and the two ends of the pretreatment unit 2 are provided with first connecting portions 21. Correspondingly, the two ends of the pretreatment box 1 are provided with second connecting portions 13, each second connecting portion 13 is connected with the pretreatment box 1 and the first connecting portion 21 located on the same side of the second connecting portion 13, the second connecting portion 13 connects and fixes the pretreatment unit 2 and the pretreatment box 1, and each second connecting portion 13 is provided with a second through hole. When the pretreatment unit 2 needs to be moved in the pretreatment box 1, an auxiliary push rod is inserted into the second through hole to move the pretreatment unit 2 in the pretreatment box 1. The second connecting portion 13 is preferably a flange structure, which is provided with at least two circles of connecting holes arranged along the circumference of circles with different diameters, and the connecting holes are provided with connecting pins. The connecting pins arranged on the circumference of the smaller diameter are connected and fixed with the pretreatment unit 2, and the connecting pins arranged on the circumference of the larger diameter are connected and fixed with the pretreatment box 1. The connecting holes for connecting with the pretreatment unit 2 can be used as the second through hole, and there is no need to additionally open the second through hole.

[0036] Further, referring to Figure 2 As shown in the drawings, at least one extension piece 22 is arranged on each first connecting part 21, the extension piece 22 can at least partially extend from the second connecting part 13 on the same side of the extension piece 22, the driving unit 3 comprises a driving shaft 30 and a driving motor 33, the driving shaft 30 is arranged in the first through hole 20, and both ends of the driving shaft 30 extend from the heating chamber 11 and the cooling chamber 12, the driving shaft 30 is connected with the extension piece 22, and is used for driving the pretreatment box 1 and the pretreatment unit 2 to synchronously rotate under the driving of the driving motor 33 through the extension piece 22.

[0037] Specifically, since the pretreatment box 1 and the pretreatment unit 2 need to be fixed during heating or cooling rotation, so that they can synchronously rotate under the rotation of the driving shaft 30, at this time, the driving shaft 30 and the pretreatment unit 2 need to be fixed, and after heating or cooling is completed, the pretreatment unit 2 needs to be moved from the heating chamber 11 to the cooling chamber 12 or directly moved out of the cooling chamber 12, so at this time, the driving shaft 30 and the pretreatment unit 2 need to be separated, since the temperature after heating of the heating chamber 11 is very high, which is inconvenient to operate, therefore, at least one extension piece 22 is arranged on each first connecting part 21, and the extension piece 22 can at least partially extend from the second connecting part 13 on the same side of the extension piece 22, and is connected with the driving shaft 30, when the driving shaft 30 and the pretreatment unit 2 need to be fixed, it can be realized outside the pretreatment box 1, which is very convenient and reduces the safety hidden danger during operation.

[0038] Further, the pretreatment unit 2 further comprises at least two connecting pieces 23, each connecting piece 23 is arranged in the driving shaft 30 and at least one extension piece 22 in sequence, so as to connect the pretreatment unit 2 and the driving shaft 30.

[0039] Specifically, in order to conveniently fix and separate the driving shaft 30 and the pretreatment unit 2, the connecting piece 23 is arranged in the driving shaft 30 and the extension piece 22 to realize locking and fixing, here, the extension piece 22 can be a cylindrical structure, which is communicated with the first through hole 20, so that the driving shaft 30 is arranged in the extension piece 22, the extension piece 22 can also be an arc-shaped sheet structure, which is fitted with the outer wall of the driving shaft 30, when the extension piece 22 is a sheet structure, in order to ensure the fastening and stability of the connection, the number of the extension piece 22 is multiple, preferably, the connecting piece 23 is a bolt structure.

[0040] Further, the partition plate 10 is slidably arranged on the top of the pretreatment box 1, the partition plate 10 is provided with an avoiding groove for avoiding the driving shaft 30, and the avoiding groove is provided with a heat preservation sheet along the inner wall thereof.

[0041] Specifically, compared to the structure rotatingly arranged in the pretreatment box 1, the structure slidingly arranged on the pretreatment box 1 is more reasonable, which can make the structure of the whole pretreatment box 1 more compact, and avoid the need of impacting the partition plate 10 when moving the pretreatment unit 2 from the heating chamber 11 to the cooling chamber 12. In addition, due to the great temperature difference between the heating chamber 11 and the cooling chamber 12, in order to ensure that the respective temperatures in the heating chamber 11 and the cooling chamber 12 can be maintained within a reasonable range, the bottom of the pretreatment box 1 is provided with a receiving groove along the width direction thereof. The receiving groove can be a structure protruding from the bottom of the pretreatment box 1, or a structure recessed in the bottom of the pretreatment box 1. When the partition plate 10 is inserted into the pretreatment box 1 to divide it into the heating chamber 11 and the cooling chamber 12, the bottom of the partition plate 10 is received in the receiving groove.

[0042] Further, the powder pretreatment system further comprises a support frame 4, which is rotationally connected with the drive shaft 30 extending from the heating chamber 11 and the cooling chamber 12. The drive shaft 30 extends out of one end of the pretreatment box 1 and is provided with a brake unit 31 and a speed changing unit 32. Specifically, the support frame 4 serves as the main frame structure of the whole powder pretreatment device, which mainly plays a supporting role. The support frame 4 is rotationally connected with the drive shaft 30 extending from the heating chamber 11 and the cooling chamber 12, and supports and fixes the pretreatment box 1, the pretreatment unit 2 and the drive unit 3. The speed changing unit 32 is used to control the speed. The number of the brake units 31 is preferably multiple. The multiple brake units 31 are used for braking, which is less likely to slip than a single brake unit 31, and has higher reliability and safety.

[0043] Further, as shown in Figure 3 The pretreatment unit 2 is provided with a vacuum extraction interface 24 and a gas filling interface 25, which respectively communicate with the receiving cavity. After the pretreatment powder is added into the receiving cavity, the receiving cavity is first subjected to vacuum extraction treatment through the vacuum extraction interface 24, and then inert protective gas is filled into the receiving cavity through the gas filling interface 25, so as to discharge the harmful gas such as oxygen in the receiving cavity and protect the pretreatment powder. The pretreatment unit 2 is further provided with a cooling flow channel 26 distributed along the outer periphery thereof. The cooling flow channel 26 comprises an inlet. After heating is completed, the pretreatment unit 2 is moved from the heating chamber 11 to the cooling chamber 12. At this time, cooling medium is introduced into the cooling flow channel 26 through the inlet, so as to assist in accelerating the cooling of the pretreatment powder.

[0044] Further, the metal ball is made of the same material as the pretreatment powder, so as to avoid the pollution of the pretreatment powder by the metal ball and ensure the composition of the pretreatment powder. The diameter of the metal ball is in the range of 3-7 mm, and the size can also be adjusted according to actual needs.

[0045] Further, since the heating chamber 11 and the cooling chamber 12 need to ensure the stability of the temperature whether heating or cooling, the pre-treatment box 1 is paved with a layer of heat preservation layer 14, which can ensure the temperature stability of the heating chamber 11 and the cooling chamber 12 as much as possible. Similarly, the heating chamber 11 is provided with a temperature increasing assembly 15 to heat the pre-treatment powder, and the cooling chamber 12 is provided with a temperature monitoring assembly 16 to monitor the real-time temperature in the cooling chamber 12 during the cooling process. When the temperature is below 100℃, the pre-treatment unit 2 can be removed from the cooling chamber 12.

[0046] Further, the pre-treatment box 1 is provided with at least two openings, one opening corresponding to the heating chamber 11 and one opening corresponding to the cooling chamber 12. The opening corresponding to the heating chamber 11 is used to put the pre-treatment unit 2, and the opening corresponding to the cooling chamber 12 is used to remove the pre-treatment unit 2. The positions of the two openings can be opened at appropriate positions according to actual needs.

[0047] The application also provides a powder pre-treatment method, which is used to implement the above-mentioned powder pre-treatment system. The steps include:

[0048] Putting the powder to be treated and a plurality of metal balls into the receiving cavity of the pre-treatment unit 2;

[0049] Fixing the pre-treatment unit 2 in the heating chamber 11, vacuumizing the receiving cavity, and filling the receiving cavity with protective gas after vacuumizing;

[0050] Driving the pre-treatment unit 2 and the pre-treatment box 1 to rotate synchronously, heating the pre-treatment unit 2, opening the partition plate 10 after heating, sliding the pre-treatment unit 2 to the cooling chamber 12, closing the partition plate 10, and driving the pre-treatment unit 2 and the pre-treatment box 1 to rotate synchronously again to cool the pre-treatment unit 2.

[0051] Further, since the number of pre-treatment units 2 can be multiple, in order to improve the efficiency of pre-treatment, when the pre-treatment unit 2 in the heating chamber 11 moves to the cooling chamber 12, another pre-treatment unit 2 can be put into the heating chamber 11, and the driving shaft 30 is driven to make the heating and cooling synchronous.

[0052] In the description of the present application, it should be noted that the terms "upper", "lower", and the like are used for indicating the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application. Unless otherwise explicitly specified and limited, the terms "mounting", "connection", "connecting" should be interpreted broadly, for example, can be fixed connection, can also be detachable connection, or integrally connected; can be mechanical connection, can also be electrical connection; can be directly connected, can also be indirectly connected through an intermediate medium, can be the internal communication of two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0053] It should be noted that in the present application, relational terms such as "first" and "second" and the like are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any such actual relationship or order between these entities or operations. Moreover, the terms "include", "contain" or any other variants thereof are intended to cover non-exclusive inclusion, so that the process, method, article or device including a series of elements not only includes those elements, but also includes other elements not explicitly listed or inherent to such process, method, article or device. Without more limitations, the element defined by the statement "including a" does not exclude the presence of other identical elements in the process, method, article or device including the element.

[0054] The above is only a specific embodiment of the present application, which enables those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to these embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features applied herein.

Claims

1. A powder pre-treatment system, characterized by, The application relates to a powder pretreatment system. The system comprises: a pretreatment box (1) with a partition plate (10) movably arranged in the box, which divides the box into a heating chamber (11) and a cooling chamber (12); at least one pretreatment unit (2) which is detachably arranged in the heating chamber (11) or the cooling chamber (12) and can slide between the heating chamber (11) and the cooling chamber (12), the pretreatment unit (2) comprising a receiving cavity for receiving powder to be treated, and a plurality of metal balls arranged in the receiving cavity; a driving unit (3) connected with the pretreatment box (1) or the pretreatment unit (2) for driving the pretreatment box (1) and the pretreatment unit (2) to rotate synchronously; the pretreatment unit (2) is provided with a first through hole (20) along the length direction of the unit, and the receiving cavity is annular; both ends of the pretreatment unit (2) are provided with first connecting parts (21), both ends of the pretreatment box (1) are provided with second connecting parts (13), each second connecting part (13) is connected with the pretreatment box (1) and the first connecting part (21) located on the same side of the second connecting part (13), and each second connecting part (13) is provided with a second through hole; each first connecting part (21) is provided with at least one extension piece (22) which at least partially extends out of the second connecting part (13) located on the same side of the extension piece (22); the driving unit (3) comprises a driving shaft (30) which passes through the first through hole (20) and extends out of the heating chamber (11) and the cooling chamber (12) at both ends, the driving shaft (30) is connected with the extension piece (22) and is used for driving the pretreatment box (1) and the pretreatment unit (2) to rotate synchronously through the extension piece (22); the pretreatment unit (2) further comprises at least two connecting pieces (23), each connecting piece (23) passes through the driving shaft (30) and at least one extension piece (22) in sequence to connect the pretreatment unit (2) and the driving shaft (30).

2. The powder pretreatment system according to claim 1, characterized in that: the partition plate (10) is slidably arranged on the top of the pretreatment box (1), the partition plate (10) is provided with an avoiding groove for avoiding the driving shaft (30), and the avoiding groove is provided with a heat preservation sheet along the inner wall.

3. The powder pretreatment system according to claim 1, characterized in that: the powder pretreatment system further comprises a support frame (4) which is rotationally connected with the driving shaft (30) extending out of the heating chamber (11) and the cooling chamber (12), and the driving shaft (30) extending out of one end of the pretreatment box (1) is provided with a brake unit (31) and a speed changing unit (32).

4. The powder pretreatment system according to claim 1, characterized in that: the pretreatment unit (2) is provided with a vacuumizing interface (24) and an air filling interface (25) which respectively communicate with the receiving cavity. The pre-treatment unit (2) is further provided with cooling flow channels (26) distributed along the outer circumferential surface thereof, and the cooling flow channels (26) comprise liquid inlets.

5. The powder pre-treatment system according to claim 1, characterized in that: The metal balls are made of the same material as the powder to be treated. The diameter of the metal balls ranges from 3 to 7 mm.

6. The powder pre-treatment system according to claim 1, characterized in that: The pre-treatment box (1) is provided with a heat insulation layer (14), the heating chamber (11) is provided with a temperature rising assembly (15), and the cooling chamber (12) is provided with a temperature monitoring assembly (16).

7. A powder pre-treatment method for implementation with a powder pre-treatment system according to any one of claims 1 to 6, characterized in that, The steps include: Placing the powder to be treated and a plurality of metal balls into a receiving cavity of the pre-treatment unit (2); Fixing the pre-treatment unit (2) in the heating chamber (11), performing vacuumizing treatment on the receiving cavity, and filling protective gas into the receiving cavity after the vacuumizing is completed; Driving the pre-treatment unit (2) and the pre-treatment box (1) to rotate synchronously, heating the pre-treatment unit (2), opening the partition plate (10) after the heating is completed, sliding the pre-treatment unit (2) to the cooling chamber (12), closing the partition plate (10), and driving the pre-treatment unit (2) and the pre-treatment box (1) to rotate synchronously again to cool the pre-treatment unit (2).

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