Preparation method of tungsten powder for high-dispersion narrow-particle-size-distribution cutting wire

Abstract

The invention relates to the technical field of powder metallurgy, in particular to a preparation method of tungsten powder for a high-dispersion narrow-particle-size-distribution cutting wire. The method comprises the following steps: S1, carrying out screening pretreatment on a raw material ammonium paratungstate by adopting a one-machine multi-screen vibrating screen; s2, according to a mixed batch grouping strategy, the pretreated ammonium paratungstate is loaded into a double-cone powder mixing machine in a batch grouping mode to be mixed; s3, pre-reducing the mixed ammonium paratungstate into tungsten oxide with W18O49 as a main phase by adopting a rotary pre-reduction furnace; and S4, reducing the tungsten oxide taking the W18O49 as the main phase into tungsten powder which is free of sintered aggregates and has narrow particle size distribution by adopting a fifteen-tube reduction furnace. The tungsten powder is in an irregular polyhedron shape, over-sintered aggregate particles do not exist, the obtained tungsten powder is suitable for high-performance cutting wire production, and the density, abrasion resistance and fracture resistance of a wire material are remarkably improved.

Description

Technical Field

[0001] This application relates to the field of powder metallurgy technology, and in particular to a method for preparing tungsten powder for cutting wire with high dispersion and narrow particle size distribution. Background Technology

[0002] Due to their high strength, high toughness, high temperature resistance, wear resistance, and long lifespan, fine tungsten alloy wires for cutting are widely used in the cutting of hard-faced materials such as silicon wafers, magnetic materials, sapphire, and silicon carbide. The alloy raw materials for cutting fine tungsten wires require high density, uniform composition, and fine grain structure. Therefore, the tungsten powder particles used to prepare the tungsten alloy blanks must be free of agglomeration, have uniform particle size, and small particle diameter.

[0003] Tungsten products sintered from tungsten powder with a narrow particle size distribution, fewer agglomerates, and uniform chemical composition exhibit superior performance. In existing technologies, industrially produced tungsten powder utilizes multiphase tungsten oxide, reduced by hydrogen under a high-gradient temperature regime. Due to their different reduction pathways, multiphase tungsten oxide particles vary significantly in size, typically ranging from 1.0 μm to 5 μm in Fisher particle size, resulting in a wide particle size distribution. This leads to the formation of sintering necks between particles and a large number of agglomerates. The wide particle size distribution of tungsten powder results in varying grain sizes due to differences in atomic diffusion rates during sintering. Agglomerate particles are also prone to abnormal grain growth during sintering, forming large, non-uniform crystals. These abnormally large crystal tungsten blanks are "inherited" in subsequent processing, making it difficult to control processing parameters and leading to frequent wire breakage during long processing steps. Tungsten products prepared from tungsten powder with a wide particle size distribution and numerous agglomerates exhibit poor performance and insufficient product quality stability, failing to meet the processing requirements for fine tungsten wires used in cutting hard-surface materials.

[0004] Tungsten powder with different particle size distributions is obtained by classifying and then mixing using an air jet mill, which can meet the needs of high-end applications, but significantly reduces the effective yield of tungsten powder. (The text then abruptly shifts to a seemingly unrelated topic: "Using W...") 18 O 49 Tungsten oxide, with its main phase, exhibits excellent structure and easy reduction properties. Its rod-like microstructure allows for the production of ultrafine tungsten powder particles. The rod-like framework structure facilitates breakage into uniform small particles during reduction, reducing agglomeration and improving the overall quality of the tungsten powder. In patents (CN120097386A, CN118751930A), researchers have demonstrated this by using W… 18 O 49 Tungsten oxide is used to prepare highly dispersible, non-agglomerated ultrafine tungsten powder. Due to the inherent structure and easily reducible properties of this type of tungsten oxide, it is mostly used to produce nanoscale ultrafine tungsten powder. Currently, most patents (CN115679174B, CN114250395A, CN114211049A) use blue tungsten oxide as the intermediate tungsten raw material for producing cutting wires, and the use of W is not observed. 18 O 49This invention relates to the production of tungsten powder for micron-sized cutting wires from tungsten oxide. 18 O 49 Tungsten oxide, with tungsten oxide as the main phase, is used to produce alloy tungsten powder for micron-sized cutting wires. This is achieved through pretreatment of raw materials and high W content. 18 O 49 By utilizing the structural characteristics of tungsten oxide and applying a small gradient temperature regime during the reduction process, the particle size of the tungsten powder is controlled, resulting in the production of fine tungsten powder for cutting wires that is free of hard agglomerates, has good uniformity, and a narrow particle size distribution. Summary of the Invention

[0005] This application provides a method for preparing tungsten powder for cutting wire with high dispersion and narrow particle size distribution to solve the above problems. The method includes:

[0006] S1. A vibrating screen with multiple sieves is used to pre-treat the raw material ammonium paratungstate by screening.

[0007] S2. According to the batch mixing strategy, the pretreated ammonium paratungstate is loaded into a double cone mixer in batch form for mixing.

[0008] S3. The mixed ammonium paratungstate is pre-reduced to W using a rotary pre-reduction furnace. 18 O 49 Tungsten oxide, with the main phase being tungsten oxide;

[0009] S4. A fifteen-tube reduction furnace is used to process the W... 18 O 49 Tungsten oxide, with the main phase as the tungsten oxide, is reduced to tungsten powder with no overburned agglomerates and a narrow particle size distribution.

[0010] The tungsten powder prepared using the above technical solution exhibits an irregular polyhedral morphology with minimal soft agglomerations and no over-sintered agglomerates. Compared to traditional methods, the particle size distribution is narrowed, the agglomeration rate is reduced to a negligible level (<1%), and energy consumption is lowered. The resulting tungsten powder is suitable for the production of high-performance cutting wires, significantly improving the density, wear resistance, and fracture resistance of the wire.

[0011] Optionally, the raw material mentioned in step S1 is a single-crystal cubic ammonium paratungstate conforming to the APT-0 grade in GB / T10116-2007, with a F-scale particle size of 40-45 μm. The ammonium paratungstate is sieved into five particle sizes: <100 mesh, 100-140 mesh, 140-200 mesh, 200-325 mesh, and >325 mesh using a multi-sieve vibrating screen.

[0012] Through the above technical solution, by adopting standardized APT-0 raw materials and precise five-stage sieving, this embodiment achieves three major improvements: First, the raw material crystals have good uniformity, eliminating the cause of agglomeration at the source after sieving; second, the proportion of intermediate particle size is increased, making the W formed during pre-reduction more efficient. 18 O49 Phase purity is improved; the proportion of soft agglomerates in the final tungsten powder is significantly reduced, with virtually no over-burned agglomerates, significantly improving the density and wear resistance of the sintered cutting wire. Utilizing the hereditary characteristics of ammonium paratungstate on tungsten powder, using single-crystal ammonium paratungstate as raw material, the morphology of the subsequently produced tungsten powder is controlled, improving the overall uniformity of the tungsten powder and solving the problem of low effective yield of tungsten powder caused by air jet mill classification.

[0013] Optionally, the hybrid batching strategy includes:

[0014] The ammonium paratungstate after sieving is divided into batches according to the following mass ratios: 100-140 mesh: ≤10%, 140-200 mesh: 40%~50%, 200-325 mesh: 40%~50%, >325 mesh: ≤10%.

[0015] Based on the above technical solution, the specific division scheme of the mixing batch is defined. Before mixing, the powder from each screening section is accurately weighed according to the following mass ratios: 100-140 mesh ≤ 10%, 140-200 mesh 40%-50%, 200-325 mesh 40%-50%, and >325 mesh ≤ 10%, and then fed into the powder mixer. The mixed material is directly sent to the rotary pre-reduction furnace through a pneumatic conveying system to ensure the integrity of the batch structure.

[0016] Optionally, in step S3, the rotary pre-reduction furnace is provided with five temperature zones, wherein: the first temperature zone of the rotary pre-reduction furnace is 650℃~720℃, the second temperature zone is 700℃~750℃, the third temperature zone is 740℃~780℃, the fourth temperature zone is 760℃~800℃, and the fifth temperature zone is 780℃~800℃.

[0017] Based on the above technical solution, and building upon the mixed batching method, the five-zone configuration of the rotary pre-reduction furnace is specifically defined. This five-zone configuration achieves material preheating and physical water removal, ammonium salt decomposition, promotion of WO3 mesophase formation, and conversion of WO3 to W. 18 O 49 The conversion process completes the final phase stabilization. This ensures a balanced residence time for the material in each belt, guaranteeing thorough conversion.

[0018] Optionally, in step S3, the feeding rate of the ammonium paratungstate is 150 kg / h to 180 kg / h;

[0019] The hydrogen flow rate in the rotary pre-reduction furnace is 3.0 m³ / s. 3 / h~6.0m 3 / h.

[0020] Through the above technical solution, by optimizing the feed rate and hydrogen flow rate, the W in tungsten oxide is increased. 18 O49 Maintaining a high phase content significantly reduces the agglomeration rate of tungsten powder while increasing production capacity. Furthermore, this parameter range reduces energy waste and the risk of localized over-reduction, improves process repeatability and stability, and ultimately enables precise control of the Fisher particle size of the tungsten powder, significantly enhancing the processing consistency and lifespan of the cutting wire.

[0021] Optionally, in step S4, the fifteen-tube reduction furnace adopts a low-temperature, small-gradient temperature regime and has four temperature zones. The first temperature zone of the fifteen-tube reduction furnace is 750℃~780℃, the second temperature zone is 780℃~800℃, the third temperature zone is 800℃~820℃, and the fourth temperature zone is 820℃~840℃.

[0022] By implementing the above technical solution and the low-temperature, small-gradient reduction system, the reduction time is shortened compared to traditional processes. The resulting tungsten powder has a stable Fisher particle size of 1.80 μm to 2.20 μm, a production-state laser particle size D50 of 3.0 μm to 3.5 μm, a diameter gap of less than 1.30 μm, and an agglomeration rate of less than 2%. The tungsten powder particles have regular morphology and good dispersibility, providing an ideal raw material for subsequent high-strength cutting wire drawing, and significantly improving the processing performance and mechanical consistency of the final product.

[0023] Optionally, in the fifteen-tube reduction furnace, the W... 18 O 49 During the reduction of tungsten oxide as the main phase, the reduction time is 2.5h~3.0h, the loading amount on both the upper and lower boats is 700g~800g, and the hydrogen flow rate is 30m³ / h. 3 / h~40m 3 / h, hydrogen dew point less than -60℃.

[0024] Through the above technical solution and the parameter combination of this embodiment, the prepared tungsten powder has a stable Fisher particle size between 1.80 μm and 2.20 μm, and a production-state laser particle size D50 of 3.0 μm to 3.5 μm. The yield is improved compared to traditional processes, and there is no agglomeration. This tungsten powder has excellent high dispersibility and particle size concentration, which effectively improves the densification uniformity of the cutting wire during the sintering process and the fracture resistance of the final product.

[0025] Optionally, in step S3, preferably, the temperature of the first zone in the rotary pre-reduction furnace is 680°C, the temperature of the second zone is 720°C, the temperature of the third zone is 760°C, the temperature of the fourth zone is 780°C, and the temperature of the fifth zone is 800°C.

[0026] The feed rate is 170 kg / h, and the hydrogen flow rate is 4.0 m³ / h. 3 / h.

[0027] Through the above technical solution and by adopting this set of optimized parameters, the best balance between process optimization and product performance was achieved. (W in tungsten oxide products) 18 O 49 The phase content is significantly increased and the whisker structure is highly intact, which results in an extremely low hard agglomeration rate of the tungsten powder obtained from subsequent reduction and a narrower particle size distribution. This setting optimizes energy consumption and production efficiency while ensuring high-quality output.

[0028] Optionally, in step S4, preferably, the temperature of the first zone in the fifteen-tube reduction furnace is 760°C, the temperature of the second zone is 790°C, the temperature of the third zone is 805°C, and the temperature of the fourth zone is 835°C.

[0029] The reduction time was 2.6 hours, the loading weight on the upper and lower boats was 760g, and the hydrogen flow rate was 36m³ / h. 3 / h, hydrogen dew point less than -60℃.

[0030] Through the above technical solution and by adopting this set of optimized parameters, the best balance between process optimization and product performance was achieved. (W in tungsten oxide products) 18 O 49 The phase content is significantly increased, and the whisker structure is highly intact, resulting in extremely low agglomeration rate and narrower particle size distribution of the tungsten powder obtained from subsequent reduction, with a production phase span of less than 1.30. Simultaneously, this setting optimizes energy consumption and production efficiency while ensuring high-quality output. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 A flowchart illustrating a method for preparing highly dispersed, narrow-particle-size cutting wire according to an embodiment of this application;

[0033] Figure 2 Here is a scanning electron microscope image of ammonium paratungstate, the raw material for this application;

[0034] Figure 3 The X-ray diffraction spatial pattern of tungsten oxide obtained in this application and its phase fitting results are shown.

[0035] Figure 4 The image shows a scanning electron microscope image of tungsten oxide obtained in this application at 2000x magnification.

[0036] Figure 5The image shows a scanning electron microscope (SEM) image of tungsten oxide obtained in this application at 50,000x magnification.

[0037] Figure 6 The image shows a scanning electron microscope (SEM) image of the tungsten powder obtained in this application at 3000x magnification.

[0038] Figure 7 This is a particle size distribution curve of the tungsten powder obtained in this application. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0040] Furthermore, the term "and / or" in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, the character " / " in this article, unless otherwise specified, generally indicates that the preceding and following related objects have an "or" relationship.

[0041] The embodiments of this application will now be described in further detail with reference to the accompanying drawings.

[0042] Tungsten products sintered from tungsten powder with a narrow particle size distribution, fewer agglomerates, and uniform chemical composition exhibit superior performance. In existing technologies, industrially produced tungsten powder utilizes multiphase tungsten oxide, reduced by hydrogen under a high-gradient temperature regime. Due to their different reduction pathways, multiphase tungsten oxide particles vary significantly in size, typically ranging from 1.0 μm to 5 μm in Fisher particle size, resulting in a wide particle size distribution. This leads to the formation of sintering necks between particles and a large number of sintered agglomerates. The wide particle size distribution of tungsten powder results in varying grain sizes due to differences in atomic diffusion rates during sintering. Agglomerate particles are also prone to abnormal grain growth during sintering, forming large, non-uniform crystals. These abnormally large crystal tungsten blanks are "inherited" in subsequent processing, making it difficult to control processing parameters and leading to frequent wire breakage during long processing steps. Tungsten products prepared from tungsten powder with a wide particle size distribution and numerous agglomerates exhibit poor performance and insufficient product quality stability, failing to meet the processing requirements for fine tungsten wires used in cutting hard-surface materials.

[0043] Based on this, this application provides a method for preparing tungsten powder for cutting wires with high dispersion and narrow particle size distribution. The prepared tungsten powder has an irregular polyhedral morphology and is free of over-sintered agglomerates. The Fisher's Squared Size (FSSS) is controlled at 1.80-2.20 μm, the production-state laser particle size D50 is 3.0-3.5 μm, and the span is less than 1.30. Compared with traditional methods, the particle size distribution is narrowed by 30%-40%, the agglomeration rate is reduced to a negligible level (<1%), and energy consumption is reduced by about 20%. The obtained tungsten powder is suitable for the production of high-performance cutting wires, significantly improving the density, wear resistance, and fracture resistance of the wire material.

[0044] For specific implementation details, please refer to the following examples.

[0045] Figure 1 This is a flowchart illustrating a method for preparing highly dispersed, narrow-particle-size cutting wire according to an embodiment of this application. Figure 1 As shown, the method includes:

[0046] S1. A vibrating screen with multiple sieves is used to pre-treat the raw material ammonium paratungstate by screening.

[0047] S2. According to the batch mixing strategy, the pretreated ammonium paratungstate is loaded into the double cone mixer in batch form for mixing.

[0048] S3. Ammonium paratungstate is pre-reduced to W using a rotary pre-reduction furnace. 18 O 49 Tungsten oxide, with the main phase being tungsten oxide;

[0049] S4, using a fifteen-tube reduction furnace to reduce W 18 O 49 Tungsten oxide, with tungsten as the main phase, is reduced to tungsten powder with no sintering agglomerates and a narrow particle size distribution.

[0050] The cutting of fine tungsten wire requires strict control over the particle size uniformity and sintering agglomerates of tungsten powder. In traditional preparation methods, multiphase tungsten oxides (such as WO3) are prone to significant particle size variations and agglomeration during hydrogen reduction due to uneven phase transformation and localized overheating, resulting in coarse-grained and unstable tungsten wires. This invention is based on W... 18 O 49 The unique rod-shaped whisker structure of the phase enables simultaneous internal and surface reduction in a hydrogen atmosphere. Through solid-phase diffusion under low-temperature, low-gradient conditions, it promotes uniform nucleation and effectively suppresses abnormal grain growth, thus providing a theoretical basis for the preparation of narrow-particle-size tungsten powder. Furthermore, the raw material sieving pretreatment and premixing batching strategy further eliminates the influence of large particles and compositional inhomogeneity, ensuring the consistency of the reduction process.

[0051] This embodiment employs an integrated preparation system, comprising four core units: raw material processing, mixing, pre-reduction, and final reduction. The raw material, ammonium paratungstate, is first pre-treated by sieving using a multi-screen vibrating screen. This vibrating screen integrates multiple screen sizes (<100 mesh, 100-140 mesh, 140-200 mesh, 200-325 mesh, >325 mesh) to achieve particle size classification. After pre-treatment, according to a pre-mixing batching strategy (100-140 mesh ≤10%, 140-200 mesh 40%-50%, 200-325 mesh 40%-50%, >325 mesh ≤10%), the ammonium paratungstate is loaded into a double-cone mixer for uniform mixing. The mixing time is 5-15 minutes to ensure uniform distribution of particles across all size ranges. The mixture then enters a rotary pre-reduction furnace, which has five temperature zones (zone 1: 650-720℃, zone 2: 700-750℃, zone 3: 740-780℃, zone 4: 760-800℃, and zone 5: 780-800℃). Temperature is controlled in a closed-loop manner using independent heating elements and thermocouples (accuracy ±5℃). The feed rate is 150-180 kg / h, and the hydrogen flow rate is 3.0-6.0 m³ / h, converting ammonium paratungstate into W... 18 O 49 Tungsten oxide is the main phase. Finally, the tungsten oxide undergoes final reduction in a fifteen-tube reduction furnace with four zones and twelve temperature points. The furnace employs a low-temperature, small-gradient temperature regime (zone 1: 750-780℃, zone 2: 780-800℃, zone 3: 800-820℃, zone 4: 820-840℃), with a reduction time of 2.5-3.0 hours. The loading weight of the upper and lower boats is 700-800g, the hydrogen flow rate is 30-40 m³ / h, and the dew point is <-60℃. Parameters are adjusted in real-time by a PID control system to produce tungsten powder with no sintering agglomerates and a narrow particle size distribution. The entire system achieves precise matching of temperature, flow rate, and time through automated control, ensuring a stable and efficient reduction process.

[0052] In other alternative or modified embodiments, the multi-screen vibrating screen 10 used in the S1 screening step can be replaced with a high-frequency vibrating screen or an ultrasonic vibrating screen to meet the screening requirements of different particle size ranges. The double cone mixer used in the S2 batch mixing step can be replaced with a vertical mixer or a V-type mixer. The rotary pre-reduction furnace in the S3 pre-reduction step can be replaced with a continuous rotary kiln. The fifteen-tube reduction furnace in the S4 final reduction step can be replaced with a multi-tube propeller reduction furnace or a twenty-tube horizontal reduction furnace. These replacements all require appropriate adjustment of process parameters to ensure that the final product still meets the requirements of narrow particle size distribution and no agglomerates.

[0053] In some embodiments, the raw material in step S1 is a single-crystal cubic ammonium paratungstate conforming to the APT-0 grade in GB / T10116-2007, with a Fisher particle size of 40-45 μm. The ammonium paratungstate is sieved into five particle sizes: <100 mesh, 100-140 mesh, 140-200 mesh, 200-325 mesh, and >325 mesh using a multi-sieve vibrating screen.

[0054] The particle size uniformity of tungsten powder used in wire cutting directly affects the mechanical properties and processing stability of the final product. The crystal morphology and initial particle size distribution of the raw material, ammonium paratungstate, are key factors determining whether agglomerates form during the reduction process. Traditional polycrystalline or irregularly shaped ammonium paratungstate is prone to uneven phase transformation during reduction, resulting in a wide particle size distribution and severe agglomeration of the tungsten powder. For example... Figure 2 As shown, this invention selects single-crystal cubic ammonium paratungstate conforming to the APT-0 grade in GB / T10116-2007. Its regular crystal structure and 40-45μm FSSS particle size lay the foundation for subsequent uniform reduction. Through precise classification using multiple sieves in one machine, oversized particles (>325 mesh) and excessive fine powder (<100 mesh) in the raw material can be effectively removed, maximizing the proportion of intermediate particle size (140-325 mesh), thereby forming W-type particles in the pre-reduction stage. 18 O 49 When using tungsten oxide as the main phase, ensure the synchronization of crystal transformation to avoid asynchronous reduction problems caused by differences in particle size.

[0055] This embodiment, based on the aforementioned embodiments, further specifies the raw material specifications and screening details. The raw material, ammonium paratungstate, adopts a single-crystal cubic form conforming to the GB / T10116-2007 APT-0 standard, with a Fisher particle size of 40-45 μm. It undergoes five-stage precise screening using a multi-screen vibrating screen, with screen configurations including <100 mesh, 100-140 mesh, 140-200 mesh, 200-325 mesh, and >325 mesh units. The vibrating screen employs an eccentric block vibrator to generate a three-dimensional vibration mode, achieving a screening efficiency of over 95%, ensuring clear separation of each particle size range. The screened powder is then batch-mixed in a double-cone mixer according to a preset ratio. The 140-200 mesh and 200-325 mesh components serve as core components (each accounting for 40%-50%), while the 100-140 mesh and <325 mesh components serve as control components (both ≤10%). The normalized particle size distribution of the raw material is achieved by controlling the percentage ratio. The process parameters of the subsequent pre-reduction furnace and reduction furnace are consistent with those of the aforementioned embodiments, forming a complete preparation chain.

[0056] In an alternative implementation, the multi-screen vibrating screen used in the screening equipment can be an ultrasonic vibrating screen to improve the screening efficiency and accuracy of fine powders. The raw material, ammonium paratungstate, can be replaced with APT-1 grade ammonium paratungstate, but the subsequent pre-reduction and final reduction process parameters need to be adjusted accordingly.

[0057] In some embodiments, the mixed batching strategy includes: dividing the sieved ammonium paratungstate into batches according to the mass ratios of 100-140 mesh: ≤10%, 140-200 mesh: 40%~50%, 200-325 mesh: 40%~50%, and >325 mesh: ≤10%.

[0058] In the preparation of tungsten powder, the differences in the behavior of particles of different sizes during reduction significantly affect the agglomeration state and particle size distribution of the final product. Unoptimized raw material mixing leads to asynchronous transformation of different particle size ranges during reduction: large particles require longer reduction times and are prone to forming agglomeration nuclei, while fine powders are prone to sticking together due to excessively high surface energy. This invention employs a precise batch mixing strategy to proportion sieved ammonium paratungstate in specific ratios (100-140 mesh ≤ 10%, 140-200 mesh 40%-50%, 200-325 mesh 40%-50%, <325 mesh ≤ 10%), resulting in a quasi-unimodal distribution of the mixture dominated by intermediate particle sizes. This distribution pattern ensures that particles of different sizes undergo synchronous phase transformation within the same temperature range during the pre-reduction stage, effectively suppressing the reduction hysteresis effect of large particles, and controlling the agglomeration tendency of fine powders through their dispersion state in the mixing system. This lays the foundation for preparing narrow-distribution tungsten powder without sintering agglomerates.

[0059] This embodiment, based on the sieving process described in the previous embodiment, focuses on defining the specific implementation plan for mixing and batching. Before mixing, the powder from each sieving segment is accurately weighed according to the following mass ratios: 100-140 mesh ≤ 10%, 140-200 mesh 40%-50%, 200-325 mesh 40%-50%, and <325 mesh ≤ 10%, and then fed into the mixer. The mixing time is set to 5-15 minutes, and online sampling and testing are used to ensure that the coefficient of variation (CV value) of the mixing uniformity is ≤ 5%. The mixed material is directly fed into the rotary pre-reduction furnace through a pneumatic conveying system to ensure the integrity of the batch structure.

[0060] Significant improvements were achieved by implementing this mixed batching strategy: the increased uniformity of raw material mixing led to higher densification in subsequent sintering processes, improved grain uniformity in the dicing wire products, and a correspondingly extended service life. By removing coarser particles (>325 mesh) and reducing finer particles (<100 mesh) in the raw material APT, the particle size distribution range was narrowed. By batch mixing raw materials of different particle sizes in appropriate proportions, a raw material APT with a narrow particle size range and a normal distribution was formed. Utilizing genetic characteristics, tungsten powder with a narrow particle size distribution, good uniformity, and good dispersibility was produced.

[0061] In alternative implementations, the double cone mixer can be replaced by a trough mixer or a ribbon mixer to accommodate different mixing capacities and uniformity requirements. The batching strategy ratio can be fine-tuned within the stated range; for example, 140-200 mesh and 200-325 mesh can be mixed in a 45% to 45% ratio to further optimize the uniformity of the raw materials.

[0062] In some embodiments, in step S3, the rotary pre-reduction furnace is provided with five temperature zones, wherein the first temperature zone of the rotary pre-reduction furnace is 650℃~720℃, the second temperature zone is 700℃~750℃, the third temperature zone is 740℃~780℃, the fourth temperature zone is 760℃~800℃, and the fifth temperature zone is 780℃~800℃.

[0063] The phase transformation path of ammonium paratungstate during the pre-reduction process has a decisive influence on the final particle size distribution and agglomeration state of tungsten powder. When processing ammonium paratungstate in traditional single-temperature or dual-temperature reduction furnaces, due to insufficient temperature gradient, multiple mixed tungsten oxide phases (such as WO3) are easily generated. These heterogeneous phases lead to uneven grain growth in subsequent reduction due to differences in conversion rates.

[0064] This embodiment, based on the mixed batching method of the aforementioned embodiments, specifically defines the five-zone configuration of the rotary pre-reduction furnace. The equipment adopts a cylindrical inclined structure with an adjustable rotation speed of 1-5 r / min. The five temperature zones achieve closed-loop control through independent silicon molybdenum rod heating elements and K-type thermocouples, with a temperature control accuracy of ±5℃. The specific temperature zones are set as follows: Zone 1 650-720℃, Zone 2 700-750℃, Zone 3 740-780℃, Zone 4 760-800℃, and Zone 5 780-800℃; to complete material preheating and physical water removal, ammonium salt decomposition, promote the formation of the WO3 mesophase, and realize the conversion of WO3 to W. 18 O 49 The material undergoes transformation and final phase stabilization. This ensures a uniform residence time for the material in each zone, resulting in complete transformation. The inner wall of the cylinder is equipped with lifting plates to promote material agitation and prevent localized overheating; the discharge end is equipped with a water-cooled jacket to quickly stabilize the product phase structure.

[0065] The five-zone rotary pre-reduction process has brought about significant technological advancements: Firstly, W in tungsten oxide... 18 O 49 The phase content remained stable at a high level of over 98%; secondly, the reduction rate was improved and energy consumption was reduced; thirdly, the product had a complete whisker structure with an aspect ratio controlled between 3 and 5, providing an ideal nucleation template for subsequent reduction; finally, the agglomeration rate of tungsten powder decreased to <2%, and the uniformity of particle size distribution was improved. (This is achieved using W...) 18 O 49 The unique porous structure of tungsten oxide results in low energy consumption during the reduction process to tungsten powder, and the obtained tungsten powder has relatively large particle size and controllable morphology.

[0066] In an alternative implementation, the rotary pre-reduction furnace can be replaced with a horizontal muffle furnace, but its temperature zone settings need to be adjusted to simulate the heat transfer and reaction conditions of a continuous rotary furnace. The temperature ranges of the first and second zones can be optimized within a given range; for example, the first zone temperature can be set at 680°C to maximize the balance between reaction rate and product phase purity.

[0067] In some embodiments, in step S3, the feed rate of ammonium paratungstate is 150 kg / h to 180 kg / h; the hydrogen flow rate in the rotary pre-reduction furnace is 3.0 m³ / h. 3 / h~6.0m 3 / h.

[0068] ammonium paratungstate is pre-reduced to W 18 O 49 In the tungsten oxide process, the feed rate and hydrogen flow rate are key factors affecting the uniformity of reduction and phase purity. In traditional processes, unstable feed rates or uneven hydrogen flow rates can lead to localized overheating or under-reduction in the furnace, resulting in multiphase tungsten oxide (such as WO3), which in turn causes a wide particle size distribution of tungsten powder and an increase in sintered agglomerates in subsequent reduction steps.

[0069] In this embodiment, the feeding system of the rotary pre-reduction furnace adopts a variable frequency speed-regulating screw conveyor, whose speed can be adjusted to 30 r / min to stably control the feeding speed of ammonium paratungstate within the range of 150 kg / h to 180 kg / h, ensuring that the material continuously and uniformly enters the five temperature zones (zone 1 650℃~720℃, zone 2 700℃~750℃, zone 3 740℃~780℃, zone 4 760℃~800℃, and zone 5 780℃~800℃). The hydrogen supply system precisely regulates the hydrogen flow rate at 3.0 m³ / h to 6.0 m³ / h through a mass flow meter, and works in conjunction with the airflow distributor in the furnace to ensure uniform hydrogen concentration in each temperature zone. Temperature sensors monitor the temperature of each zone in real time and feed the data back to the control system. The PID algorithm dynamically adjusts the heating element power and hydrogen flow rate to maintain optimal reduction conditions. This system works in concert to achieve the efficient conversion of ammonium paratungstate into W in the rotary furnace. 18 O 49 The tungsten oxide is the main phase, and its phase purity is stable, providing an ideal precursor for subsequent reduction steps.

[0070] In an alternative implementation, a vibrating feeder can be used instead of a screw conveyor for feeding. Hydrogen flow rate control can be precisely adjusted using a mass flow controller. When the feed rate is at its lower limit of 150 kg / h, the hydrogen flow rate can be appropriately reduced to maintain the reducing properties of the atmosphere; when the feed rate is at its upper limit of 180 kg / h, the hydrogen flow rate should be increased to approximately 6.0 m³ / h to ensure a sufficient reaction atmosphere.

[0071] In some embodiments, in step S4, the fifteen-tube reduction furnace adopts a low-temperature small-gradient temperature regime and has four temperature zones. The first temperature zone of the fifteen-tube reduction furnace is 750℃~780℃, the second temperature zone is 780℃~800℃, the third temperature zone is 800℃~820℃, and the fourth temperature zone is 820℃~840℃.

[0072] W 18 O 49 The final reduction of tungsten oxide, with tungsten oxide as the main phase, to metallic tungsten powder is a crucial step determining its particle size distribution and agglomeration state. Traditional reduction processes often employ high-temperature, large-gradient temperature increases, which can easily lead to rapid reduction on the particle surface, forming a dense layer that hinders hydrogen diffusion into the particle interior. This results in asynchronous reduction between the internal and external layers, subsequently causing grain coarsening and agglomeration. This invention employs a low-temperature, small-gradient temperature regime based on W... 18 O 49 The unique rod-shaped whisker structure and solid-phase diffusion-based reduction mechanism allow for effective control of the reduction reaction rate within a relatively low temperature range of 750℃ to 840℃, coupled with a small temperature difference of only 30℃ to 40℃ between adjacent temperature zones. This enables hydrogen gas to fully penetrate the internal pores of the tungsten oxide particles, achieving uniform nucleation and slow growth from the inside out. This significantly inhibits abnormal grain growth and the formation of sintering necks, ultimately yielding high-quality tungsten powder with no sintering agglomerates and a narrow particle size distribution.

[0073] In this embodiment, the fifteen-tube reduction furnace is the core equipment. Its furnace body is divided into four independent temperature zones, forming a twelve-point temperature control system. A PID temperature controller achieves precise temperature control (fluctuation ±3℃) for the first zone (750℃~780℃), the second zone (780℃~800℃), the third zone (800℃~820℃), and the fourth zone (820℃~840℃). The material is carried by nickel-based high-temperature alloy boats, with a loading of 700g~800g on each boat, pushed through each temperature zone at a constant speed to ensure uniform heating. High-purity hydrogen (flow rate 30m³ / h~40m³ / h, dew point <-60℃) is introduced against the material flow direction to fully contact the tungsten oxide and carry out the reduction reaction. This integrated system ensures W by coordinating temperature, atmosphere, and conveying speed. 18 O 49 Tungsten oxide is reduced to the target tungsten powder under optimized kinetic conditions, providing an ideal raw material for the subsequent drawing of high-strength cutting wires, and significantly improving the processing performance and mechanical consistency of the final product.

[0074] In an alternative implementation, the fifteen-tube reduction furnace can be replaced with a ten-tube or twenty-tube horizontal reduction furnace, but the tube diameter, loading capacity, and propulsion speed need to be adjusted accordingly to maintain the same thermal history. The arrangement of the first to fourth temperature zones can be based on W. 18 O 49The phase transition characteristics can be fine-tuned, for example, by setting the initial temperature of the first zone at 760°C to further slow down the reaction rate in the early stages of reduction.

[0075] In some embodiments, in a fifteen-tube reduction furnace, W 18 O 49 During the reduction of tungsten oxide as the main phase, the loading weight of the upper and lower boats is 700g~800g, and the hydrogen flow rate is 30m³ / h. 3 / h~40m 3 / h, hydrogen dew point less than -60℃.

[0076] In the final reduction stage from tungsten oxide to tungsten powder, time, loading amount, and atmospheric conditions together constitute the core process window that determines product performance. Too short a reduction time leads to incomplete reaction and residual oxides in the core; too long a time causes excessive grain growth, resulting in tungsten grain aggregation and recrystallization to form a sintered body. The loading amount directly affects the thickness of the material buildup in the furnace and the mass and heat transfer efficiency; excessive loading can easily cause temperature differences between the inner and outer layers and uneven reduction. Hydrogen flow rate and dew point jointly determine the reduction driving force and the ability to suppress side reactions (such as water vapor oxidation).

[0077] In this embodiment, the fifteen-tube reduction furnace operates under a four-zone low-temperature gradient temperature regime (zone 1: 750℃~780℃, zone 2: 780℃~800℃, zone 3: 800℃~820℃, zone 4: 820℃~840℃). Its boat-pushing system is controlled by a speed-regulating motor to precisely maintain the total residence time (i.e., reduction time) of the nickel-based superalloy boats carrying tungsten oxide within the furnace at 2.5h~3.0h. The loading weight of each boat is set to 700g~800g, which is determined by the thermal simulation. The proposed optimization aims to ensure appropriate material layer thickness and uniform heating. The hydrogen supply system uses a mass flow meter to stabilize the flow rate of high-purity hydrogen at 30 m³ / h to 40 m³ / h, and a deep drying tower equipped with molecular sieves continuously controls the hydrogen dew point below -60°C. The entire system is integrated and managed by a central control system, achieving closed-loop control of time, temperature, flow rate, and dew point to ensure the stability and repeatability of the reduction process, effectively improving the densification uniformity of the cutting wire during the sintering process and the fracture resistance of the final product.

[0078] In an alternative implementation, the loading amount of the upper and lower boats can be adjusted appropriately according to the tube diameter of the reduction furnace, but the consistency of the loading thickness should be maintained. Hydrogen dew point control can be achieved using a deep drying system, such as molecular sieves or a cold trap, to ensure that the dew point remains below -60°C.

[0079] In some embodiments, in step S3, preferably, the temperatures of the first zone in the rotary pre-reduction furnace are 680°C, the second zone is 720°C, the third zone is 760°C, the fourth zone is 780°C, and the fifth zone is 800°C; the feed rate is 170 kg / h, and the hydrogen flow rate is 4.0 m³ / h. 3 / h.

[0080] This embodiment provides a preferred version. This specific temperature configuration (680℃ / 720℃ / 760℃ / 780℃ / 800℃) constitutes a precisely optimized temperature gradient, designed based on the stepwise dehydrogenation of ammonium paratungstate (APT) to W. 18 O 49 The chemical reaction kinetics were analyzed. The first zone initiated the initial dehydration and decomposition of APT at 680℃ to avoid instantaneous densification of the particle surface due to excessively high temperatures. Subsequent zones increased in a gradient of approximately 40℃ to ensure a stable and gradual dehydrogenation reaction, allowing the intermediate product to be fully converted into W with a rod-like whisker structure. 18 O 49 With a feed rate of 170 kg / h and a hydrogen flow rate of 4.0 m³ / h, the material has a constant residence time in the furnace, and the hydrogen atmosphere achieves an optimal stoichiometric ratio. This ensures high conversion while maximally suppressing the formation of other tungsten oxide phases such as WO3 or WO2, thus achieving high-purity W. 18 O 49 The precursor provides an ideal thermodynamic and kinetic environment.

[0081] In this embodiment, the rotary pre-reduction furnace, through its five-band independent temperature control system, employs PID regulation and thermocouple closed-loop feedback to precisely set and stabilize the temperatures at 680℃ for the first band, 720℃ for the second band, 760℃ for the third band, 780℃ for the fourth band, and 800℃ for the fifth band. The feeding system uses a frequency-controlled screw conveyor to stabilize the feeding speed at 170 kg / h, ensuring that the material passes through each temperature zone at a uniform speed. The hydrogen supply unit controls the flow rate at 4.0 m³ / h through a high-precision mass flow meter and works in conjunction with the furnace rotation to create a uniform reducing atmosphere. The entire system is integrated by a central control system, which monitors and adjusts the temperature, rotation speed, and flow rate in real time to ensure the stable execution of the optimized process parameters, ultimately producing a high-efficiency output of W. 18 O 49 With tungsten oxide as the main phase (content >99%), this design optimizes energy consumption and production efficiency while ensuring high-quality output.

[0082] In alternative embodiments, if different grades of ammonium paratungstate raw materials (such as APT-1 grade ammonium paratungstate) are used, the temperature zones need to be fine-tuned, for example, by slightly increasing or decreasing the temperature of the first zone. However, the overall temperature gradient and dynamic parameters should be maintained at levels close to the preferred values ​​to ensure W 18 O 49 Conversion rate and quality of tungsten oxide.

[0083] In some embodiments, in step S4, preferably, the temperature of the first zone in the fifteen-tube reduction furnace is 760°C, the temperature of the second zone is 790°C, the temperature of the third zone is 805°C, and the temperature of the fourth zone is 835°C; the reduction time is 2.6 hours, the loading amount of the upper and lower boats is 760g, and the hydrogen flow rate is 36m³ / h. 3 / h, hydrogen dew point less than -60℃.

[0084] Tungsten powder used for cutting wires requires high dispersibility and an extremely narrow particle size distribution to ensure uniformity in the subsequent wire drawing process and stability of the wire's mechanical properties. Traditional reduction processes often result in inconsistent tungsten powder particle growth due to large temperature gradients and uneven hydrogen permeation, leading to hard agglomeration and a wide particle size distribution.

[0085] This embodiment is based on W 18 O 49 Based on the physicochemical properties of tungsten oxide as the main phase, it possesses a well-developed rod-shaped whisker structure and internal porosity. Under low-temperature, low-gradient reduction conditions, hydrogen can fully penetrate into the interior of the particles, achieving uniform nucleation and simultaneous reduction through a solid-phase diffusion mechanism. The optimized four-zone temperature (760℃→790℃→805℃→825℃) ensures a smooth reduction process, avoiding abnormal grain growth caused by local overheating, thereby obtaining tungsten powder with no hard agglomeration and a highly concentrated particle size distribution.

[0086] In alternative implementations, if a finer tungsten powder with a Fisher particle size (e.g., FSSS less than 1.8 μm) is required, the overall temperature of the four temperature zones can be lowered by approximately 5°C to 10°C, and the reduction time can be appropriately shortened. Conversely, if a slightly coarser powder is required, the overall temperature can be raised. However, regardless of the adjustments, a low-temperature, small-gradient temperature regime must be strictly maintained, and the hydrogen dew point must be kept below -60°C to prevent the formation of hard agglomerates.

Claims

1. A method for preparing tungsten powder for cutting wire with high dispersion and narrow particle size distribution, characterized in that, include: S1. A vibrating screen with multiple sieves is used to pre-treat the raw material ammonium paratungstate by screening. S2. According to the batch mixing strategy, the pretreated ammonium paratungstate is loaded into a double cone mixer in batch form for mixing. S3. The mixed ammonium paratungstate is pre-reduced to W using a rotary pre-reduction furnace. 18 O 49 Tungsten oxide, with the main phase being tungsten oxide; S4. A fifteen-tube reduction furnace is used to process the W... 18 O 49 Tungsten oxide, with tungsten as the main phase, is reduced to tungsten powder with no sintering agglomerates and a narrow particle size distribution.

2. The method according to claim 1, characterized in that, The raw material mentioned in step S1 is a single-crystal cubic ammonium paratungstate conforming to the APT-0 grade in GB / T10116-2007, with a Fisher particle size of 40-45 μm. The ammonium paratungstate is sieved into five particle sizes: <100 mesh, 100-140 mesh, 140-200 mesh, 200-325 mesh, and >325 mesh using a vibrating sieve with multiple sieves.

3. The method according to claim 2, characterized in that, The hybrid batching strategy includes: The ammonium paratungstate after sieving is divided into batches according to the following mass ratios: 100-140 mesh: ≤10%, 140-200 mesh: 40%~50%, 200-325 mesh: 40%~50%, >325 mesh: ≤10%.

4. The method according to claim 3, characterized in that, In step S3, the rotary pre-reduction furnace is provided with five temperature zones, wherein the first temperature zone of the rotary pre-reduction furnace is 650℃~720℃, the second temperature zone is 700℃~750℃, the third temperature zone is 740℃~780℃, the fourth temperature zone is 760℃~800℃, and the fifth temperature zone is 780℃~800℃.

5. The method according to claim 4, characterized in that, In step S3, the feeding rate of the ammonium paratungstate is 150 kg / h to 180 kg / h; The hydrogen flow rate in the rotary pre-reduction furnace is 3.0 m³ / s. 3 / h~6.0m 3 / h.

6. The method according to claim 5, characterized in that, In step S4, the fifteen-tube reduction furnace adopts a low-temperature, small-gradient temperature regime and has four temperature zones. The first temperature zone of the fifteen-tube reduction furnace is 750℃~780℃, the second temperature zone is 780℃~800℃, the third temperature zone is 800℃~820℃, and the fourth temperature zone is 820℃~840℃.

7. The method according to claim 6, characterized in that, In the fifteen-tube reduction furnace, the W 18 O 49 During the reduction of tungsten oxide as the main phase, the reduction time is 2.5h~3.0h, the loading amount on both the upper and lower boats is 700g~800g, and the hydrogen flow rate is 30m³ / h. 3 / h~40m 3 / h, hydrogen dew point less than -60℃.

8. The method according to claim 4, characterized in that, In step S3, preferably, the temperature of the first zone in the rotary pre-reduction furnace is 680°C, the temperature of the second zone is 720°C, the temperature of the third zone is 760°C, the temperature of the fourth zone is 780°C, and the temperature of the fifth zone is 800°C. The feed rate is 170 kg / h, and the hydrogen flow rate is 4.0 m³ / h. 3 / h.

9. The method according to claim 6, characterized in that, In step S4, preferably, the temperature of the first zone in the fifteen-tube reduction furnace is 760°C, the temperature of the second zone is 790°C, the temperature of the third zone is 805°C, and the temperature of the fourth zone is 835°C. The reduction time was 2.6 hours, the loading weight on the upper and lower boats was 760g, and the hydrogen flow rate was 36m³ / h. 3 / h, hydrogen dew point less than -60℃.

10. A tungsten powder for cutting wire with high dispersion and narrow particle size distribution, characterized in that, Prepared by any one of the preparation methods of claims 1-9, comprising: The tungsten powder for the high-dispersion, narrow-particle-size cutting wire has an overall irregular polyhedral morphology, without over-sintered agglomerates, a Fisher particle size of 1.80μm-2.2μm, a production-state laser particle size D50 of 3.0-3.5μm, and a diameter spacing of less than 1.30.

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