Powder heat treatment device and process

Abstract

The present application discloses a device for heat treatment of powders, which has a spiral conveyor belt with adjustable pitch inside the device; a process for heat treatment of powders, which uses the treatment device; and a method for producing crystalline materials using the process and device. The treatment system provided by the present application has the advantages of short heat treatment time, uniform heating of materials, controllable heat treatment degree, and no accumulation of heat-treated materials inside the system, and is easy to industrialize; the heat treatment system provided by the present application can assist in the transmission of powders, realize heat treatment of various heating rates, and improve heat treatment efficiency; the treatment method provided by the present application has the advantages of controllable heat treatment degree and adjustable processing volume, and is conducive to application at the industrial level.

Description

Technical Field

[0001] The present application relates to a device and process for heat treatment of powder, belonging to the field of heat treatment systems. Background Art

[0002] Fe-based amorphous nanocrystalline alloys offer excellent magnetic properties such as high saturation magnetic flux density, high magnetic permeability, low coercivity, and low losses, as well as advantages such as low material cost. Since their development, they have attracted considerable attention and become a hot topic of research in the materials field. However, their poor macroscopic plastic deformation and low amorphous formability limit their size and machinability, becoming major bottlenecks hindering their widespread application. Preparing Fe-based amorphous alloys into powder materials and then into bulk materials through powder metallurgy can address these application challenges and have already found widespread application in magnetic powder cores such as inductors. Conventional mass production of high-sphericity amorphous nanocrystalline powders is primarily achieved through atomization. High saturation magnetic flux density requires alloys with a higher Fe content, and excellent soft magnetic properties can be achieved by regulating (heat treatment) a uniform and dense α-Fe nanocrystalline structure. However, due to limitations in amorphous forming ability and the cooling rate of existing rapid cooling processes, achieving an amorphous structure in high-Fe powder alloys is difficult. Often, achieving a uniform nanocrystalline structure in high-Fe amorphous alloys with a good initial amorphous structure requires heat treatment at extremely high heating rates. Traditional heat treatment methods using trays (inserted or placed in a heating furnace) can easily lead to uneven heating of the powder due to the influence of the thickness and weight of the powder stack, making it difficult to obtain uniform nanocrystalline particles and resulting in poor microstructural stability. Currently, there is a lack of methods for uniform heating batch heat treatment.

[0003] The present invention is dedicated to solving the problem of non-uniform heating of amorphous alloy powder. By allowing the amorphous alloy powder to rotate or even freely fall through a heated spiral conveyor belt, the surplus Fe atoms are crystallized and precipitated in large quantities in the form of α-Fe, obtaining a uniform nanocrystalline structure and improving the soft magnetic properties of the powder.

[0004] Patent 202021299657.X discloses a furnace tube, comprising a feed zone and a heat treatment zone, wherein one end of the feed zone is provided with a feed port and the other end is connected to the heat treatment zone, the feed zone is provided with a plurality of fins, the fins extending along the length direction of the furnace tube, the plurality of fins being dispersed along the circumference of the furnace tube, the heat treatment zone being provided with a plurality of heat treatment cavities, the plurality of heat treatment cavities being arranged side by side in the circumferential direction of the furnace tube so that the heat treatment zone forms a hollow structure, and a furnace tube baffle is provided at the junction of the feed zone and the heat treatment zone for isolating the hollow parts of the feed zone and the heat treatment zone so that the feed can completely enter the heat treatment cavity. The fins guide and disperse the metal powder entering the feed zone, so that the metal powder evenly enters the multiple heat treatment cavities and is spread flat on the inner wall of the heat treatment cavity, which solves the problems of metal powder accumulation and low production capacity during mass production to a certain extent. At the same time, it solves the problem of uneven heating of the powder. However, the time and temperature windows for heat treatment of amorphous materials with some components are very narrow. This patented method still lacks more flexible heat treatment conditions, such as temperature, time, batch size, recovery method and other factors, and there is still a pile-up effect in the cavity space during the validity period. Summary of the Invention

[0005] Because the time and temperature windows for heat treatment of some amorphous materials are very narrow, we need to perform ultra-rapid heating or short-term heat treatment on some materials to control the precipitation density and grain size of the crystal nuclei. This heat treatment can be a single heat treatment or an initial heat treatment for a subsequent reheat treatment.

[0006] A first aspect of the present application provides a device for heat treatment of powders, which is a hollow cylinder. A spiral conveyor belt is installed inside the hollow cylinder, and the diameter of the spiral conveyor belt is equal to the inner diameter of the hollow cylinder.

[0007] Optionally, the spiral conveyor belt can adjust the pitch to adjust the slope of the spiral conveyor belt so that the residence time of the material to be heat treated in the device can be adjusted.

[0008] Optionally, the spiral conveyor belt may be one of a single spiral, a double spiral, and a triple spiral.

[0009] Optionally, the spiral channel can adjust the vertical angle of the spiral blade.

[0010] Optionally, the vertical angle ranges from 0° to 90°.

[0011] This device is used because it can adjust the pitch of the screws to change the residence time of the material being heat-treated in the heat treatment device. This control of the residence time can then be used to alter the material's residual amorphousness and nanocrystalline structure, achieving the desired effect desired by those skilled in the art. The use of complex spiral conveyor belt structures, such as single, double, and triple spirals, aims to double or triple the material flow rate while ensuring sufficient residence time and uniform heating of the material. This allows the material to be fed into the heat treatment device, achieving double, triple, or even greater processing capacity. Furthermore, the use of multiple spiral feed methods allows for even higher heat utilization.

[0012] Optionally, a disc for storing the material before heat treatment is provided above the hollow cylinder, and the disc can rotate to adjust the flow rate of the material; the disc can also be tilted.

[0013] Optionally, the disc has an inclination angle of 0-90° and a rotation speed of 1-100 rpm.

[0014] The reason for adopting this device is that the amount of material falling into the heat treatment device can be changed by adjusting the inclination angle and angular velocity of the disc. By combining single-helix, double-helix and triple-helix structures, the output of the material can be controlled under the premise of uniform heating.

[0015] Optionally, a heater is further provided on the outside of the hollow cylinder;

[0016] A powder receiver is provided at the bottom end of the hollow cylinder;

[0017] The hollow cylinder is also provided with an inert gas inlet;

[0018] The inlet can be placed at the upper end, middle or lower end of the cylinder.

[0019] The reason for adopting this setting scheme is that the inert gas inlet can be set at the bottom end of the heat treatment area for backblowing, making the material easier to slide down, so that it will not stay on the spiral conveyor belt, causing blockage or reducing efficiency; the inert gas inlet can also be set at the top end of the heat treatment area. The technical effect brought by setting it at the top end is similar to that of setting it at the bottom end.

[0020] Optionally, a material receiving trough is further provided at the bottom of the hollow cylinder.

[0021] The reason for adopting this setting scheme is that by setting up a material receiving tank, the heat-treated materials can be concentrated in the receiving tank, so that the recycled materials will not be lost, thereby further ensuring the recovery rate of the heat-treated materials and the operating efficiency of the heat treatment equipment.

[0022] A second aspect of the present invention provides a process for heat treatment of powders, the process flow of which is as follows:

[0023] (1) placing the material in the storage portion of the heat treatment device;

[0024] (2) heating the heat treatment device to the target material temperature and introducing an inert gas;

[0025] (3) adjusting the valve connecting the storage unit and the heat treatment device so that the material falls into the heat treatment device for heat treatment;

[0026] (4) The heat-treated material is collected by a collector at the bottom of the heat treatment device.

[0027] Wherein, the heat treatment device described in (2) is the powder heat treatment device described above;

[0028] The storage portion and valve described in (1) and (3) are the aforementioned discs;

[0029] (4) The collector is the material receiving trough mentioned above.

[0030] Optionally, the inert gas is selected from at least one of argon, helium, and nitrogen.

[0031] A third aspect of the present invention provides a method for processing amorphous powder to produce crystalline powder.

[0032] Optionally, the amorphous powder is iron-based amorphous powder.

[0033] The beneficial effects of this application include:

[0034] 1) The treatment system provided in this application has the advantages of short heating time, uniform heating of materials, high material heating rate, controllable material holding time, controllable relaxation and nanocrystalline structure (volume fraction of crystal nucleus precipitation, grain size, distribution and volume fraction), and no accumulation of heat-treated materials inside the system, and is easy to industrialize and mass-produce.

[0035] 2) The heat treatment system provided in this application can assist in the transfer of powders, achieve heat treatment at various heating rates, and improve processing efficiency.

[0036] 3) The treatment method provided in this application has the advantages of controllable heat treatment degree and adjustable treatment volume, which is conducive to application at the industrial level. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 This is a stereoscopic diagram of the device used in Example 1 of the present application, wherein a is a direct view to the outside and b is a direct view to the inside.

[0038] Figure 2 This is a cross-sectional view of the spiral conveyor belt structure in the device used in Example 1 of the present application.

[0039] Figure 3 This is the DSC graph of the input material and the recovered material after heat treatment in Example 1 of the present application, wherein S1 is the area of the first crystallization peak in the ideal amorphous crystallization process; S2 is the area of the second crystallization peak in the ideal amorphous crystallization process; S1' is the area of the first crystallization peak in the process of crystallization of the remaining amorphous in the sample after heat treatment and heating again; S2' is the area of the second crystallization peak in the process of crystallization of the remaining amorphous in the sample after heat treatment and heating again.

[0040] Figure 4 This is the XRD pattern of the input material and the recovered material after heat treatment in Example 1 of the present application. DETAILED DESCRIPTION

[0041] The present application is described in detail below with reference to embodiments, but the present application is not limited to these embodiments.

[0042] The target heat treatment conditions used in all the following embodiments and comparative examples have a set temperature of 200-1400°C; the heat-treated material is an amorphous powder with a composition range of Fe-B (-M, where M is another element); the inactive gas is argon or nitrogen gas purchased from Huayu manufacturer with high purity, and the gas flow rate used is 20 mV; the magnetic test is carried out using Lake Shore 7410 equipment manufactured by Beijing Oriental Morning View Technology Co., Ltd.; the yield is calculated using the following formula: total amount of material collected within 1 hour / total amount of material added = yield within 1 hour.

[0043] Example 1

[0044] This embodiment uses a spiral conveyor belt with a single spiral structure for heat treatment. The cross-sectional structure of the spiral conveyor belt is shown in the attached figure of the present application. Figure 2 As shown, the device used in this embodiment is the Figure 1 The device shown.

[0045] The material Fe 83.3 Si4B8P4Cu 0.7The amorphous alloy powder is placed on a disc, the heater temperature is adjusted to the target temperature of the required heat treatment conditions, and the inactive gas flow rate is adjusted. The disc is tilted to 60°, the rotation rate is set to 50 rpm, and the timing starts from the time the material falls into the heat treatment chamber. After 1 hour of heat treatment, the material at the bottom of the heat treatment equipment is collected and weighed to calculate the yield (weight ratio) of the nanocrystalline powder after the material is heat treated. The material before and after heat treatment is subjected to organizational structure, thermal properties and magnetic properties to calculate the conversion rate of the amorphous material into nanocrystalline material after the material is heat treated. The yield and conversion rate are shown in Table 1. Samples are taken every 10 minutes to calculate the yield, conversion rate, and repetition rate and stability of the nanocrystalline particle size of the product, where:

[0046] Yield: the ratio of recovered weight to input weight;

[0047] Conversion rate: when S2 does not change (no other phase precipitation), {(S1-S1') / S1)} Nanocrystal particle size: calculated using the Scherrer formula from the XRD crystallization peak data.

[0048] Table 1:

[0049]

[0050] Example 2

[0051] This embodiment uses a spiral conveyor belt with a single spiral structure for heat treatment. The cross-sectional structure of the spiral conveyor belt is shown in the attached figure of the present application. Figure 2 As shown, the device used in this embodiment is the Figure 1 The device shown.

[0052] The material Fe 83.3 Si4B8P4Cu 0.7 Amorphous alloy powder was placed on a disk. The heater temperature was adjusted to the target temperature for the desired heat treatment conditions, and the inert gas flow rate was adjusted. The disk was tilted at 45° and rotated at 50 rpm. Timing was started from the moment the powder fell into the heat treatment chamber, as in Example 1. The yield and conversion rates obtained are shown in Table 2. Samples were taken every 10 minutes to calculate the product yield, conversion rate, and the reproducibility and stability of the nanocrystal particle size.

[0053] Table 2:

[0054]

[0055] Example 3

[0056] This comparative example uses a heat treatment device without a spiral conveyor belt to obtain the organizational structure, thermal properties and magnetic properties of the product described in Example 2, and the time required for the test and output is benchmarked.

[0057] The material Fe 73.5 Si 13.5 B9Nb3Cu1 amorphous alloy powder is placed on a disc, the heater temperature is adjusted to the target temperature of the required heat treatment conditions, and the inactive gas flow rate is adjusted. The disc tilt is set to 15° and the rotation rate is set to 50rpm. The heat treatment time required for this embodiment is 2 hours. During the heat treatment process, the timer is started and the setting time is 120 minutes. When the set time is reached, the controller opens the air outlet and discharges the sample onto the material tray for weighing to calculate the yield of nanocrystalline powder after heat treatment of the material. The material before and after heat treatment is tested for its organizational structure and thermal properties to calculate the conversion rate of amorphous material into nanocrystalline material after heat treatment.

[0058] The characterization results are shown in the following table:

[0059]

[0060] Comparative Example 1

[0061] This comparative example uses a heat treatment device without a spiral conveyor belt to obtain the organizational structure, thermal properties and magnetic properties of the product described in Example 1, and the time required for the test and output is compared.

[0062] Material Fe 83.3 Si4B8P4Cu 0.7 The nanocrystalline alloy powder is obtained by conventional heat treatment of the amorphous alloy powder described in Example 1. The heat treatment time required in this comparative example is 1 hour. Samples were taken every 60 minutes during the heat treatment process. The α-Fe grain size in the nanocrystalline structure of the obtained samples was less than (16nm). According to the literature [Acta Mater. 61(3)(2013)718–734; IEEE Trans. Magn. 26(1990)1397], the material obtained by this heat treatment method has excellent soft magnetic properties.

[0063]

[0064] Comparative Example 2

[0065] This comparative example uses a heat treatment device without a spiral conveyor belt to obtain the organizational structure, thermal properties and magnetic properties of the product described in Example 3, and the time required for the test and output is benchmarked.

[0066] Material Fe 73.5 Si 13.5The B9Nb3Cu1 amorphous alloy powder was heat treated for one hour to achieve the magnetic properties and yield described in Example 3. Samples were taken and weighed every 60 minutes during the heat treatment process to calculate the yield of nanocrystalline powder after the heat treatment. The microstructure and thermal properties of the material before and after the heat treatment were tested to determine the conversion rate of the amorphous material to nanocrystalline material after the heat treatment.

[0067] The characterization results are shown in the following table:

[0068]

[0069] Analysis example

[0070] Magnetic performance test data

[0071] Fe 83.3 Si4B8P4Cu 0.7 Heat treatment conditions and performance comparison of materials

[0072]

[0073] Fe 73.5 Si 13.5 Heat treatment conditions and performance comparison of B9Nb3Cu1 materials

[0074]

[0075] Overall review: Example 1 and Example 2 found that when a spiral conveyor with a single spiral structure is used, by adjusting the heating temperature to the target temperature of the required heat treatment conditions and adjusting the inclination angle, it is possible to ensure the product yield and uniformity while allowing more materials to be uniformly heat treated compared to the method of stacking a large amount of powder. Through Example 3 and Comparative Example 2, it was found that when a single spiral conveyor is used, by adjusting the heating temperature to the target temperature of the required heat treatment conditions and adjusting the inert gas flow rate, the crystallization amount and magnetic properties of the obtained magnetic powder can also be controlled to be relatively stable, indicating that the spiral conveyor scheme allows the material to be heated evenly during the slow heat treatment process, thereby obtaining nanocrystalline magnetic powder with uniform physical properties. For the same material and final preparation yield, the method of the spiral conveyor technical solution of this patent is continuous and has higher execution efficiency.

[0076] The above descriptions are merely a few embodiments of the present application and do not constitute any form of limitation to the present application. Although the present application discloses the preferred embodiments as above, they are not intended to limit the present application. Any technical personnel familiar with the present profession, without departing from the scope of the technical solution of the present application, using the technical content disclosed above to make slight changes or modifications are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A method for converting amorphous alloy powder into nanocrystalline powder, characterized in that: The following powder heat treatment process is adopted, and the process flow is as follows: (1) Place the materials in the storage area; (2) Heating the heat treatment device to the heat treatment temperature of the material and introducing inert gas; (3) Adjust the feeding rate of the material before heat treatment so that the material falls into the heat treatment device for heat treatment; (4) The heat-treated material is collected by a collector at the bottom of the heat treatment device; Wherein, the heat treatment device described in step (2) is a powder heat treatment device; The device includes a hollow cylinder and a screw-type conveying structure; The screw conveying structure is vertically placed inside the hollow cylinder; The diameter of the screw conveying structure is equal to the inner diameter of the hollow cylinder; The screw conveying structure has a spiral channel; The device also includes a disc for storing material before heat treatment, a trough for collecting material after heat treatment, a heater for heating the heat treated material and a vent for introducing gas; The disc is placed above the hollow cylinder and can be rotated and tilted horizontally; The groove is placed below the hollow cylinder; The heater is located outside the hollow cylinder; The vent hole is located at any position of the hollow cylinder; The storage portion in step (1) is the disc; The collector described in step (4) is the trough.

2. The method according to claim 1, characterized in that The screw conveying structure is one of a single screw, a double screw and a triple screw structure.

3. The method according to claim 1, characterized in that The spiral channel can adjust the vertical angle of the spiral blade.

4. The method according to claim 1, wherein The disc has an inclination angle of 0-90° and a rotation speed of 1-100 rpm.

5. The method according to claim 1, characterized in that The inert gas is selected from at least one of argon, helium and nitrogen.

6. The method according to claim 1, characterized in that The amorphous alloy powder is iron-based amorphous powder.

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