Tungsten alloy wire, its manufacturing method and use, tungsten carbide alloy filament

Abstract

This invention relates to tungsten alloy wire, its manufacturing method and use, and tungsten carbide alloy filament. The tungsten alloy contains 0.0005-0.3 wt% carbon, 0.25-2.6 wt% M, 0.05-0.5 wt% oxygen, the remainder being tungsten and unavoidable impurities, and does not contain thorium. The tungsten alloy wire has an initial recrystallization temperature of 48%Fc-56%Fc and / or an average grain size of 1-15 μm at 80%Fc. This tungsten alloy wire is thorium-free, free from radioactive contamination issues, has an initial recrystallization temperature of 48%Fc-56%Fc, and exhibits significantly improved processing performance compared to thorium-containing tungsten materials. Compared to thorium-containing tungsten wire, this tungsten alloy wire has fewer crack detection points. Furthermore, when used as the matrix for tungsten carbide alloy filaments, the crystal grains of the tungsten matrix after carbonization are finer, making the filaments less prone to breakage during the production and use of magnetron coils, thus improving production yield and quality.

Description

[Technical Field]

[0001] This invention relates to the technical field of filament cathode materials, and more particularly to tungsten alloy wires, methods for manufacturing and using the same, and tungsten carbide alloy filaments. [Background technology]

[0002] Filament cathodes, or electron emitters, are widely used in the field of microwave oven magnetrons. The performance of the filament cathode significantly impacts the operating characteristics and lifespan of the magnetron, and it is considered the heart of the magnetron. Existing filament materials are primarily manufactured from tungsten-thorium oxide or tungsten-rare earth oxides.

[0003] For example, Patent Document 1 (Chinese Invention Patent, published April 3, 2013) discloses a method for doping powder for magnetron coils. The process of this invention includes steps such as doping, stirring, and steam drying. It is characterized by adding an ammonia aqueous solution (NH3·H2O), which is a neutralizing additive, to a thorium nitrate solution, and uniformly spraying the prepared mixed solution onto the surface of blue tungsten oxide (WO2.9) in a doping pot and stirring. The doping pot is vacuum-suctioned and heated with water, and stirred while heating. The powder is dried by a steam heating method under vacuum, and finally, a uniformly doped tungsten-thorium oxide doped powder with a low impurity content is obtained.

[0004] The invention patent (Patent Document 1) states that a magnetron coil material made by adding thorium oxide to pure tungsten can achieve continuous operation for more than 1,000 hours. However, cathode products manufactured from such composite materials have a high brittle-ductile transition temperature and are difficult to process and mold. As a result, magnetron cathodes are prone to fracture during production and transportation. Furthermore, because the recrystallization temperature is relatively low, the recrystallization growth of the magnetron coil progresses abnormally during the carbonization process, leading to frequent fractures during use and transportation, and ultimately to magnetron failure. In addition, since thorium is a radioactive element, using thorium as the main additive raw material may not only pollute the environment during the smelting, production, transportation, and use processes, but also potentially have adverse health effects on people who come into contact with the final manufactured product.

[0005] As described above, conventional tungsten-thorium filaments are radioactive and not only contaminate the environment, but also pose potential adverse health effects to people who come into contact with the final manufactured product. Furthermore, existing tungsten-thorium filaments have a relatively low recrystallization temperature, resulting in a high number of crack points per 100m of wire. This leads to abnormal recrystallization growth during the carbonization process of magnetron coils, resulting in frequent breakage during production, use, and transportation, causing problems such as reduced product yield and poor quality. How to solve the above problems is a challenge that those skilled in the art are striving to overcome. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Chinese Patent Application Publication No. 102009179 (Chinese Patent Application No. 2010102991399.2) [Overview of the project] [Problems that the invention aims to solve]

[0007] Conventional tungsten-thorium filaments are radioactive, contaminating the environment and potentially posing adverse health effects to those who come into contact with the final manufactured product. Furthermore, existing thorium-tungsten filaments have a coarse structure with fully recrystallized tungsten grains after carbonization, making them prone to breakage during magnetron production and use. In addition, thorium-containing tungsten materials suffer from poor processing performance and numerous defects in the wire. To address these problems in the conventional technology, the present invention provides a tungsten alloy filament and a method for manufacturing the same. The specific technical solutions are as follows. [Means for solving the problem]

[0008] This invention provides a method for manufacturing tungsten alloy wire, and the technical solution is as follows.

[0009] The tungsten alloy comprises 0.0005 to 0.3 wt% carbon, 0.25 to 2.6 wt% M, 0.05 to 0.5 wt% oxygen, the remainder being tungsten and unavoidable impurities, and does not contain thorium, and the M is one or more elements selected from La, Y, Sc, Nd, Sm, Lu, Ce, Gd, Tb, Dy, Ho, Pr, Er, Tm, Yb, Eu, Hf, and Zr. The manufacturing process for the tungsten alloy wire includes the steps of doping / powdering, powder pressing, sintering, and pressurization in that order. In the pressurization step, the sintered tungsten alloy strip is processed to reduce its diameter to an intermediate standard wire of 1.5 to 3.5 mm. Subsequently, the intermediate standard wire is oxidized at (1200 to 1500) °C and an annealing rate of (3 to 10) m / min. After oxidized annealing, the intermediate standard wire is further processed to the desired wire diameter standard to obtain tungsten alloy wire. The tungsten alloy wire has an initial recrystallization temperature of 48%Fc to 56%Fc, and / or an average grain size of (1 to 15) μm at 80%Fc recrystallization.

[0010] In one embodiment, in the sintering step, a tungsten alloy sintered strip is obtained by a high-temperature sintering method, and the heating curve for the high-temperature sintering is as follows: the temperature is raised from room temperature to A1 at a predetermined rate, held at A1 for a predetermined time, the temperature is raised from A1 to A2 for a heating time of H3, and held at A2 for H4, A1 is (950~1250)°C, H3 is (1.5~2.5)h, A2 is (1300~1500)°C, H4 is (2.5~4.5), the temperature is raised from A2 to A3 at a predetermined rate, A3 is (1700~1900)°C, held at A3 for a predetermined time, the temperature is raised from A3 to A4 at a predetermined rate, A4 is (2050~2250)°C, held at A4 for a predetermined time, and then naturally cooled from A4.

[0011] In one embodiment, the heating curve for the high-temperature sintering is as follows: from room temperature to A1, the heating time H1 is (5~8)h, A1 is (950~1250)℃, A1 is held for time H2, H2 is (1~3), the temperature is raised from A1 to A2, the heating time is H3, H3 is (1.5~2.5)h, A2 is (1300~1500)℃, A2 is held for time H4, H4 is (2.5~4.5) The temperature is raised from A2 to A3, the heating time is H5, H5 is (1-3)h, A3 is (1700-1900)℃, A3 is kept warm for H6 hours, H6 is (1-3), the temperature is raised from A3 to A4, the heating time is H7, H7 is (1-3)h, A4 is (2050-2250)℃, A4 is kept warm for H8 hours, H8 is (5-10), and the mixture is allowed to cool naturally from A4.

[0012] In some embodiments, the M element exists in the form of an oxide, and the average size of the oxide particles in the tungsten alloy wire is (100-500) nm.

[0013] In some embodiments, the density of the tungsten alloy sintered strip was 17.5 to 18.3 g / cm³. 3 Therefore, the average size of the oxide particles in the tungsten alloy sintered strip is less than 2.0 μm.

[0014] The present invention provides a tungsten alloy wire comprising, as its components, 0.0005 to 0.3 wt% of carbon, 0.25 to 2.6 wt% of the M element, 0.05 to 0.5 wt% of oxygen, the remainder being tungsten and unavoidable impurities, and the components not comprising thorium, wherein the M element is one or more combinations selected from La, Y, Sc, Nd, Sm, Lu, Ce, Gd, Tb, Dy, Ho, Pr, Er, Tm, Yb, Eu, Hf, and Zr, and the tungsten alloy wire having an initial recrystallization temperature of 48%Fc to 56%Fc and / or an average grain size of (1 to 15) μm at 80%Fc recrystallization.

[0015] In some embodiments, the M element exists in the form of an oxide, and the average size of the oxide particles in the tungsten alloy wire is (100-500) nm.

[0016] In one embodiment, the element M exists in the form of an oxide, the element carbon exists in the form of a carbide or elemental carbon, the oxide of M is one or more selected from lanthanum oxide, yttrium oxide, scandium oxide, neodymium oxide, samarium oxide, lutetium oxide, cerium oxide, gadolinium oxide, terbium oxide, dysprosium oxide, holmium oxide, praseodymium oxide, erbium oxide, hafnium oxide, and zirconium oxide, and the carbide is one or more selected from lanthanum carbide, zirconium carbide, yttrium carbide, hafnium carbide, and tungsten carbide.

[0017] In one embodiment, the tungsten alloy wire has a diameter of 800 μm or less, and the number of cracks detected by flaw detection is less than 5 per 100 m.

[0018] In one embodiment, the components of the tungsten alloy wire further include a T element, the T element is a metal element, and T is at least one selected from K, Re, Mo, Fe, and Co. The mass content of Re in the tungsten alloy wire is less than 1000 ppm.

[0019] The present invention further provides the use of the above-mentioned tungsten alloy wire. After carbonizing the tungsten alloy filament, it is used as a cathode alloy wire for a microwave heating device.

[0020] The present invention further provides a tungsten carbide alloy filament obtained by carbonizing the above-mentioned tungsten alloy wire.

Advantages of the Invention

[0021] Based on the above, compared with the prior art, the present invention has the following advantages.

[0022] The tungsten alloy wire of the present invention does not contain thorium element, and there is no problem of radioactive contamination of conventional thorium-tungsten filaments.

[0023] <0000​​​​​​

[0025] To more clearly illustrate embodiments of the present invention or technical solutions in the prior art, the drawings that may be used in describing embodiments or the prior art will be briefly described below. The drawings in the following description are some embodiments of the present invention, and it will be obvious to those skilled in the art that other drawings can be obtained based on these drawings without any creative effort. [Brief explanation of the drawing]

[0026] [Figure 1] This is a schematic diagram of the partial structure of the tungsten alloy filament after carbonization according to the present invention. [Figure 2] This is a schematic diagram of the cross-sectional structure of the tungsten alloy filament after carbonization according to the present invention. [Figure 3] This is a schematic diagram of the longitudinal cross-sectional structure of the tungsten alloy filament after carbonization according to the present invention. [Figure 4] This is an enlarged view of section A in Figure 2. [Figure 5] This is a schematic diagram of the partial cross-sectional structure of a tungsten alloy filament after carbonization according to the present invention. [Figure 6] This is a microstructure image of Comparative Example 1 according to the present invention at 44% FC. [Figure 7] This is a microstructure image of Comparative Example 1 according to the present invention at 46% FC. [Figure 8] This is a microstructure image of Comparative Example 1 according to the present invention at 48% FC. [Figure 9] This is a microstructure image of Comparative Example 1 according to the present invention at 50% FC. [Figure 10] This is a microstructure image of the metallographic structure of Example 1 according to the present invention at 48% FC. [Figure 11] This is a microstructure image of the metallographic structure of Example 1 according to the present invention at 50% FC. [Figure 12] This is a microstructure image of the metallographic structure of Example 1 according to the present invention at 52% FC. [Figure 13] This is a schematic diagram of the crystal structure of Comparative Example 1 according to the present invention. [Figure 14] This is a schematic diagram of the crystal structure of Example 1 according to the present invention. [Figure 15] This figure shows the channel distribution in a cross-section of Example 1 according to the present invention. [Figure 16] This figure shows the channel distribution in a longitudinal section of Example 1 according to the present invention. [Figure 17] This figure shows the channel distribution in a cross-section of Comparative Example 1 according to the present invention. [Figure 18] This is a schematic diagram of the process flow for manufacturing a heating device using tungsten alloy wire according to the present invention. [Figure 19] This figure shows the conversion relationship between FC% and Celsius temperature. [Figure 20] This is a schematic diagram illustrating the principle of the high-temperature sintering process. [Modes for carrying out the invention]

[0027] To further clarify the object, technical solutions, and advantages of the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings of the embodiments, and obviously, the embodiments described are some of the embodiments of the present invention, not all of them. The technical features designed in the different embodiments of the present invention described below may be combined with each other, insofar as they do not conflict with each other. All other embodiments obtained by those skilled in the art without creative effort based on the embodiments of the present invention are within the scope of the protection of the present invention.

[0028] In describing the present invention, all terms used herein (including technical and scientific terms) have the same meaning as those generally understood by those skilled in the art and should not be understood as limiting the invention. Furthermore, terms used herein should be understood to have meanings consistent with their meanings in the context of this specification and in the related art, and should not be understood in an idealized or overly formal sense, except as expressly defined herein.

[0029] The present invention provides a tungsten alloy wire, and its technical solution is as follows.

[0030] The tungsten alloy comprises 0.0005 to 0.3 wt% carbon, 0.25 to 2.6 wt% M, 0.05 to 0.5 wt% oxygen, the remainder being tungsten and unavoidable impurities, and does not contain thorium. The M is one or more elements selected from La, Y, Sc, Nd, Sm, Lu, Ce, Gd, Tb, Dy, Ho, Pr, Er, Tm, Yb, Eu, Hf, and Zr, the M exists in oxide form, and the carbon exists in carbide or elemental carbon form.

[0031] The tungsten alloy wire has an initial recrystallization temperature of 48%Fc to 56%Fc, and / or an average grain size of (1 to 15) μm at 80%Fc recrystallization.

[0032] Regarding the composition of ingredients, In this invention, one or more types of M oxides and carbon elements are added. Since the M oxides and carbides in the tungsten matrix react at high temperatures (the operating temperature of tungsten carbide alloy filaments is high-temperature), for example, lanthanum oxide and tungsten carbide react to produce lanthanum atoms. The size of the produced lanthanum atoms is much smaller than the size of the lanthanum oxide particles, which results in very fast migration and diffusion rates of lanthanum atoms in the tungsten matrix, and thus accelerates the diffusion rate of M metal atoms.

[0033] As can be seen from the above, compared to a thorium-tungsten filament, the present invention achieves electron emission capabilities equivalent to, or even better than, thorium-tungsten at a lower operating voltage (excitation temperature) by combining an oxide of M and an element of carbon (carbide or elemental carbon). Furthermore, it is possible to ensure the stability of electron emission from the filament by more easily balancing the loss and replenishment of rare earth atoms through migration in the filament carbide layer.

[0034] Regarding the initial recrystallization temperature characteristics, The initial recrystallization temperature of the tungsten alloy wire according to the present invention is higher than that of thorium-containing tungsten wire, being 48%Fc to 56%Fc in this application, while that of thorium-tungsten is approximately 46%FC (2020°C).

[0035] The average 80%Fc recrystallized grain size of the tungsten alloy wire according to the present invention is finer than that of thorium-containing tungsten wire. The average 80%Fc recrystallized grain size of the tungsten alloy wire of this application is (1 to 15) μm, while the average 80%Fc recrystallized grain size of thorium-tungsten filament is (16 to 150) μm.

[0036] Due to the above-mentioned characteristics of a high recrystallization temperature and a small average grain size of 80%Fc recrystallized grains, the filaments produced with the tungsten alloy wire of the present invention have a finer tungsten matrix structure after magnetron carbonization than that of thorium-tungsten filaments.

[0037] The process of manufacturing tungsten alloy wire into a carbide-coated filament involves a carbonization step at a carbonization temperature of 2000-2500°C. Existing thorium-tungsten filaments, when carbonized at this temperature (analysis indicates that the initial recrystallization temperature is too low), undergo recrystallization of the grain structure, resulting in coarser grains. Consequently, the carbonized filament becomes highly brittle, has poor vibration resistance, and is very prone to breakage during magnetron assembly, production, transportation, and subsequent use in microwave ovens.

[0038] The filament material produced by this invention has a higher initial recrystallization temperature than existing thorium-tungsten wires and a smaller average 80%Fc recrystallized grain size than existing thorium-tungsten wires compared to thorium-tungsten filaments. The tungsten alloy filament of this application maintains a fine-grained structure even after carbonization and is less brittle than conventional thorium-tungsten filament materials. The tungsten alloy filament having a fine-grained structure has superior vibration resistance compared to thorium-tungsten filaments. The filament breakage rate of magnetrons produced by this invention is much lower than that of magnetrons produced with conventional thorium-tungsten.

[0039] Optionally, the initial recrystallization temperature of the tungsten alloy wire may be 48-52%FC, for example, 48%FC, 50%FC, 52%FC, etc.

[0040] Optionally, the average grain size of the 80%Fc recrystallized tungsten alloy wire may be (1-8) μm, (8-12)% μm, (12-15) μm, etc., or for example, 4.0 μm, 8.5 μm, 13 μm, etc.

[0041] Regarding the characteristics of the average size of oxide particles in the tungsten alloy wire: The average size of oxide particles in the tungsten alloy wire is (100-500) nm.

[0042] The average size of the oxide particles in the tungsten alloy wire of this application is (100~500) nm.

[0043] The reason for limiting the size of the oxide particles in the tungsten alloy wire in this application to the specified range is that the size of the oxide particles in the tungsten alloy wire determines the size of the oxide particles in the filament after carbonization. If the oxide particles in the wire are too coarse compared to the specified range, the oxide particles of M in the filament will have difficulty moving to the filament surface during the use of the magnetron. As a result, the balance between the loss and replenishment of rare earth elements on the filament surface will be easily disrupted, and thus, electron emission from the magnetron will become unstable.

[0044] Optionally, the average size of the oxide particles may be (100-300) nm, (300-500) nm, etc., or for example, 200 nm, 300 nm, 450 nm, etc.

[0045] The present invention further provides preferred embodiments of a method for manufacturing tungsten alloy wire that achieve the above-mentioned parameters of recrystallization temperature range and average size range of oxide particles.

[0046] The following steps are included. Step 1: The finished powdered raw material is manufactured by sequentially going through a doping process, a reduction process, and a powdering process. Here, the doping process is either solid-liquid doping or solid-solid doping.

[0047] Step 2: Powder Pressing: Using a hydrostatic pressure method, powders of different particle sizes are pressed into a compact, and the compact is pre-sintered at a low temperature under a hydrogen atmosphere to increase its strength. Here, the powder is pressed at a pressure of 160-240 MPa, resulting in a compact with a single weight of 1.5-5.0 kg.

[0048] Step 3: High-temperature sintering: Using high-temperature sintering or vertical melting sintering methods, the density is 17.5-18.3 g / cm³. 3 A sintered strip, i.e., a tungsten alloy material in the shape of a strip, is obtained.

[0049] The heating curve for the aforementioned high-temperature sintering is as follows: The temperature was raised from room temperature to A1, the heating time H1 was (5-8) hours, and A1 was (950-1250)°C. For example, H1 is (5-7)h, (7-8)h, etc., and also, for example, 6h, 7.5h, etc., and A1 is (950-1050)℃, (1050-1250)℃, etc., and also, for example, 1000℃, 1100℃, etc. In A1, the temperature is maintained for the duration of H2, and H2 is (1-3). For example, H2 can be (1-2)h, (2-3)h, etc., and also, for example, 1.5h, 2.5h, etc. The temperature was increased from A1 to A2, the heating time was H3, H3 was (1.5~2.5)h, and A2 was (1300~1500)℃. For example, H3 is (1.5~2.0)h (2.0~2.5)h, and also, for example, 1.5h, 2.0h, 2.4h, and A2 is (1300~1400)℃, (1400~1500)℃, and also, for example, 1350℃, 1500℃, The temperature was kept at A2 for H4 time, and H4 was (2.5~4.5). For example, H4 is (2.5~3.0)h, (3.0~4.0)h, etc., and also, for example, 2.8h, 3.5h, etc. The temperature was increased from A2 to A3, the heating time was H5, H5 was (1-3) hours, and A3 was (1700-1900)°C. For example, H5 is (1-2)h, (2-3)h, etc., and also, for example, 1.6h, 2.0h, 2.5h, etc., and A3 is (1700-1800)℃, (1800-1900)℃, etc., and also, for example, 1750℃, 1850℃, etc. In A3, the temperature was kept high for only H6 hours, and H6 was (1-3). For example, H6 can be (1-2)h, (2-3)h, etc., or for example, 1.5h, 2.5h, etc. The temperature was increased from A3 to A4, the heating time was H7, H7 was (1-3) hours, and A4 was (2050-2250)°C. For example, H7 is (1-2)h, (2-3)h, etc., and also, for example, 1.5h, 2.5h, etc., and A4 is (2050-2150)℃, (2150-2250)℃, etc., and also, for example, 2100℃, 2200℃, etc. In A4, keep warm for H8 time, and H8 is (5-10). For example, H8 can be (5-7)h, (7-10)h, etc., or for example, 6h, 8h, etc. It is obtained by natural cooling from A4 paper.

[0050] Step 4: Pressurization 4.1 In the pressurization step, the sintered tungsten alloy strip produced by sintering is processed to reduce its diameter to an intermediate standard wire of 1.5 to 3.5 mm.

[0051] 4.2 Subsequently, the intermediate standard wire is oxidatively annealed at (1200~1500)°C and an annealing rate of (3~10) m / min. For example, the annealing rate may be (3~7) m / min, (7~10) m / min, or for example, 3 m / min, 5 m / min, 7 m / min, and the oxidative annealing may be at (1200~1350)°C, (1350~1500)°C, or for example, 1250°C, 1400°C, etc.

[0052] 4.3 After annealing, the intermediate standard wire is further processed to the desired wire diameter to obtain tungsten alloy wire (also called black wire). Here, multi-pass rotary forging and drawing methods are used for the diameter reduction process, the annealing process is carried out in an annealing apparatus, and the annealing speed refers to the speed at which the wire passes through the annealing tank, representing the length of wire that passes through the annealing tank per unit time.

[0053] Step 5: White Wire Cleaning: The tungsten alloy wire is cleaned using an electrolytic cleaning method to produce tungsten alloy white wire that can be used as filament for microwave heating devices.

[0054] Step 6: Winding: The white wire is wound to form a spring-like filament structure for the heating device, thereby obtaining a tungsten alloy wire.

[0055] Regarding the key points of control in a preferred embodiment of the manufacturing method: (1) Oxidative annealing treatment of intermediate-grade products: This invention provides a specific method for annealing in the pressurization step described above, thereby bringing the initial recrystallization temperature of the tungsten alloy within the desired range (48%Fc to 56%Fc). Specifically, by performing stress-relieving annealing at a temperature of 1200 to 1500°C once the wire reaches an intermediate specification of 1.5 to 3.5 mm, the initial recrystallization temperature of the tungsten alloy wire can be effectively brought within the range of 48%Fc to 56%Fc. In this manufacturing process, if the annealing process is omitted, the initial recrystallization temperature of the tungsten alloy wire will exceed 56%Fc, and if the initial recrystallization temperature is too high, it will be detrimental to the electron emission performance of the tungsten carbide alloy filament under magnetron operating conditions.

[0056] (2) In the sintering process, by controlling the time it takes to raise the temperature from A1 to A2 and the sintering time at A2 (1300~1500℃): In the high-temperature sintering stage of a tungsten blank, the present invention provides a sintering process that controls the time it takes to raise the temperature from A1 to A2 and the sintering time at A2 (1300-1500°C) in the sintering process, thereby rapidly growing the sintered neck of the tungsten blank, closing the pores, preventing oxide particles in the pores from being pushed into other pores through unclosed connecting channels during the shrinkage of the sintered cavity of the strip, thereby ensuring the density of the sintered strip, and controlling the size of the oxide particles in the sintered strip, thereby controlling the size of the oxides in the tungsten alloy wire or the filament after carbonization.

[0057] Here, in the tungsten alloy sintered strip manufactured using the above sintering process, the oxide particle size distribution range is 100 to 2000 nm, and the average size of the oxide particles is 600 to 1000 nm, while in the tungsten alloy wire, the average size of the oxide particles is (100 to 500) nm. Optionally, the average size of the oxide particles may be (100 to 300) nm, (300 to 500) nm, or, for example, 200 nm, 300 nm, 450 nm, etc.

[0058] On the other hand, when the above sintering process is not used, the oxide particle size distribution range for sintered tungsten alloy strips is 400-5000 nm, and the average size of the oxide particles is 1200-2000 nm. In even thinner tungsten alloy wires, the average size of the oxide particles also becomes relatively coarser (approximately 500-900 nm).

[0059] The mechanism by which the sintering process affects the size of the oxides in the tungsten alloy wire, tungsten alloy wire, and carbonized filament, and the influence of the oxide size of the tungsten alloy wire and carbonized filament on the function and performance of the filament, are as follows.

[0060] The reason for limiting the size of oxide particles to a narrower range is that the size of the oxide particles in the wire directly determines the size of the oxides in the tungsten alloy wire or the filament after carbonization. The coarser the oxide particles in the wire, the less likely the filament particles are to move to the filament surface during magnetron use. As a result, the balance between loss and replenishment of rare earth elements on the filament surface is easily disrupted, and thus electron emission from the magnetron becomes unstable.

[0061] Adjusting the sintering process affects the growth of the sintered neck and the rate of pore closure in the tungsten blank. The process of the provided sintering method can reduce the possibility of oxide particle aggregation and further reduce the oxide particle size of the sintered elementary strip. As shown in Figure 20, the specific principle of the high-temperature sintering process is explained as follows.

[0062] The compacted powder, obtained by hydrostatic pressing, is a high-density aggregate of powder with a porosity of approximately 35-45%. These pores can be easily understood as individual cavities with multiple interconnected channels, and oxide particles are uniformly distributed on the inner surface of these cavities.

[0063] During the high-temperature sintering process, the tungsten particles that adhere together form a "sintered neck." As the sintering temperature rises, the sintered neck continues to grow, blocking the channels that connect the cavities, resulting in the formation of isolated cavities. These isolated cavities gradually become rounded, reducing their internal surface area, and furthermore, small oxide particles of similar size aggregate to form larger oxide particles. As high-temperature sintering progresses, the cavities shrink further due to diffusion, forcing the oxide particles distributed on the inner surface of the cavities to aggregate further, forming one or more larger oxide particles.

[0064] Some small cavities merge with adjacent larger cavities through diffusion, or they completely contract before the channels connecting the cavities close. As a result, oxide particles in these small cavities are pushed into adjacent, unclosed cavities, resulting in a higher concentration of oxide in the unclosed cavities than in other areas, and subsequently, the oxide particle size becomes coarser than in other areas.

[0065] 1. Characteristics of the preferred components of tungsten alloy wire: (1) Preferably, the tungsten alloy wire consists of 0.0005 to 0.3 wt% carbon, 0.25 to 2.6 wt% M, 0.05 to 0.5 wt% oxygen, the remainder being tungsten and unavoidable impurities.

[0066] Here, the amount of element M may be 1.28 to 2.6 wt%, and tungsten alloy filaments manufactured using tungsten alloy material with this composition ratio can be effectively used in microwave ovens under 800W. The amount of element M may be 0.25 to 1.28 wt%, and tungsten alloy filaments manufactured using tungsten alloy material with this composition ratio can be effectively used in microwave ovens exceeding 800W. Furthermore, the amount of element M may be 0.25 to 0.86 wt%, and tungsten alloy filaments manufactured using tungsten alloy material with this composition ratio can be effectively used in microwave ovens exceeding 1000W.

[0067] (2) The oxide M is one or more selected from lanthanum oxide, yttrium oxide, scandium oxide, neodymium oxide, samarium oxide, lutetium oxide, cerium oxide, gadolinium oxide, terbium oxide, dysprosium oxide, holmium oxide, praseodymium oxide, erbium oxide, hafnium oxide, and zirconium oxide. The carbon element is present in the tungsten alloy material in the form of a carbide or elemental carbon, and the carbide is one or more selected from lanthanum carbide, zirconium carbide, yttrium carbide, hafnium carbide, and tungsten carbide. For example, the oxide M may be selected from lanthanum oxide, or a combination of lanthanum oxide and yttrium oxide, or a combination of lanthanum oxide and zirconium oxide, or a combination of lanthanum oxide and scandium oxide, or a combination of lanthanum oxide and hafnium oxide, etc.

[0068] Preferably, the tungsten alloy material further contains T, where T is a solid solution metal element or a dispersed metal element, and T is at least one selected from K, Re, Mo, Fe, and Co. More preferably, the mass content of Re is less than 1000 ppm.

[0069] In this specification, "La, Y, Sc, Nd, Sm, Lu, Ce, Gd, Tb, Dy, Ho, Pr, Er, Tm, Yb, Eu, Hf, Zr" are element symbols in the periodic table, and are the metallic elements in the periodic table: lanthanum, yttrium, scandium, neodymium, samarium, lutetium, cerium, gadolinium, terbium, dysprosium, holmium, praseodymium, erbium, thulium, ytterbium, europieu. "K", "Re", "Mo", "Fe", and "Co" in this specification are periodic table element symbols, representing potassium, rhenium, molybdenum, iron, and cobalt, respectively, which are metallic elements in the periodic table. "W" is the symbol for tungsten in the periodic table, and "C" is the symbol for carbon in the periodic table. "M" and "T" are merely reference symbols and do not represent elements in the periodic table; they are used for reference only.

[0070] 2. Regarding the preferred structural features of the tungsten alloy wire described above: (1) The diameter of the tungsten alloy wire mentioned above may be 800 μm or less.

[0071] The tungsten alloy wire according to the present invention exhibits good processing performance in the pressurization process, can be processed into wire material of a fine wire diameter standard (i.e., fine-diameter tungsten alloy wire), and can keep the wire diameter tolerance within an extremely small range.

[0072] Furthermore, the diameter of the tungsten alloy wire can be 600 μm or less, 550 μm or less, or even 500 μm or less. The diameter of the tungsten alloy wire may be 450 to 550 μm, such as 470 μm, 490 μm, 500 μm, 520 μm, or 700 to 800 μm, such as 750 μm, 760 μm, 780 μm.

[0073] (2) The number of cracks detected in the tungsten alloy wire described above is less than 5 (cracks / 100m). Furthermore, the number of cracks detected in the tungsten alloy wire may be less than 2 / 100m, for example 0 / 100m, 0.5 / 100m, 1 / 100m, etc.

[0074] Tungsten alloy wire has a low detection crack rate, a high filament yield, and is less prone to breakage.

[0075] 3. When tungsten alloy wire is subjected to a carbonization treatment, a tungsten carbide alloy filament is obtained. The present invention further provides the following preferred embodiments of a method for manufacturing a tungsten carbide alloy filament.

[0076] Step 1. Cathode Assembly: Heat treatment assembles the spring-like filament structure and components such as assemblies, ceramics, and lead pieces into the cathode structure.

[0077] Step 2. Welding: The filament structure in the cathode structure and the end cap of the assembly are welded together as a single unit.

[0078] Step 3. Carbonization: The cathode structure is placed in a carbonization tank and carbonized. After exhausting the tank, a carbon-containing hydrocarbon gas is introduced, and a DC current of a constant value is passed through the cathode structure to heat it, completing the carbonization of the filament structure in the hydrocarbon gas. When the filament structure is carbonized, the tungsten alloy filament is formed.

[0079] Step 4. Assembling the white sphere: Assemble the components such as the cathode structure, anode tube, and antenna end cap into a single unit.

[0080] Step 5. Blackening Treatment: The white spheres were evacuated and vacuum-suctioned, and high-temperature aging was performed to complete the production of the black spheres and the activation of their emission performance.

[0081] Step 6: Assembling the heating device: Assemble the black sphere, heat sink, magnet, tube shell, etc., to finally manufacture the heating device component containing the tungsten alloy filament described above. This manufactured heating device component can then be incorporated into an appliance (e.g., a microwave oven) and used.

[0082] Here, the tungsten alloy filament produced by carbonizing the tungsten alloy filament of the present invention includes a matrix 100 and a carbonized layer 200 covering the outer periphery of the matrix 100, as shown in Figures 1 to 5, and the carbonized layer 200 has channels 210 distributed therein, including a first channel 211 and a second channel 212.

[0083] Here, at least a portion of the first channel 211 is distributed along the radial direction of the cross-section of the filament, and / or at least a portion of the first channel 211 is directed toward the center of the cross-section of the filament. The second channel 212 divides the carbonized layer 200 to form a layered structure stacked along the radial direction, and further, the first channel 211, designed to intersect with the second channel 212, divides the carbonized layer 200 to form a block-like structure, thereby giving the carbonized layer 200 a stacked block-like structure.

[0084] Furthermore, as shown in the filament structure in Figure 1, the cross-section of the filament in Figure 2, and the longitudinal section of the filament in Figure 3, the phrases "distributed along the radial direction of the cross-section of the filament" and "at least a portion of the first channel 211 is directed toward the center of the cross-section of the filament" as described herein mean that the distribution is radial and directed toward the center, respectively, that a first straight line is formed by connecting the endpoint of the first channel 211 closest to the matrix 100 and the endpoint of the filament edge, and that the distribution is such that the angle between the first straight line and the tangent line at the intersection of the outer edge 220 of the filament is (60~90)°.

[0085] As shown in Figure 5, the phrase "distributed along the circumferential direction of the cross-section of the tungsten alloy filament" as described herein means that the circumferential distribution is such that a second straight line is formed by connecting the endpoints of both ends of the second channel 212, and the angle between the second straight line and the straight line located in the radial direction of the filament is (-45 to +45)°.

[0086] In the present invention, the first channel 211 is distributed substantially radially and substantially perpendicular to the outer edge 220 of the filament (i.e., the outer edge of the carbonized layer 200). This does not mean that the first channel 211 has a linear structure, nor does it mean that the two endpoints of the first channel 211 need to penetrate to the outer edge of the matrix 100 and the carbonized layer 200 (i.e., the outer edge 220 of the filament).

[0087] In the present invention, the second channel 212 is distributed along the circumferential direction or is arranged intersecting with the first channel 211. This does not mean that the second channel 212 has a standard arc structure, nor does it mean that the second channel 212 is continuously connected so as to penetrate the entire outer ring. Rather, it may be a substantially annular distribution consisting of a plurality of separated sections of the second channel 212 to divide the carbide layer 200 and form a layered structure stacked radially, or a cross-distribution of a plurality of separated sections of the second channel 212 and the first channel 211.

[0088] The present invention further provides the following examples and comparative examples.

[0089] The weight composition of the raw material components for the examples and comparative examples of the present invention and the elemental composition ratio of the manufactured filament materials are shown in Table 1 below.

[0090] [Table 1] JPEG2026514492000003.jpg145170

[0091] Specifically, tungsten alloy filaments and heating devices were manufactured according to the formulations shown in Table 1, using the raw material components from the examples and comparative examples, and following the manufacturing method described below.

[0092] Example 1 1. Following the formulation in Table 1, 5 L of deionized water was added to a predetermined amount of lanthanum nitrate solution and stirred for 10 minutes to dissolve completely. Then, 1 L of aqueous ammonia solution (NH3·H2O) was added and stirred to neutralize. The prepared mixed solution was uniformly sprayed onto blue tungsten oxide in a doping pot and stirred. The volume ratio of lanthanum nitrate solution to aqueous ammonia solution (NH3·H2O) was 5:1.

[0093] 2. The doping pot was vacuum-suctioned, heated with water (heating temperature 80°C, vacuum degree -0.025 MPa), and stirred while heating.

[0094] 3. The powder was dried under vacuum by steam heating, with the steam pressure set to 0.1-0.3 MPa and the vacuum level in the pot to -0.02 MPa or less. Finally, a uniformly doped tungsten-lanthanum doped powder with a low impurity content was obtained.

[0095] 4. Tungsten-lanthanum doped powder was reduced collectively in a reduction furnace with four temperature zones at 650°C, 750°C, 850°C, and 900°C to obtain tungsten-lanthanum powder with appropriate particle size.

[0096] 5. The obtained tungsten-lanthanum powder and tungsten carbide were placed in a high-speed powder mixer and subjected to solid-solid mixing for 2 hours. The mixture was then sieved to obtain a mixed tungsten-lanthanum alloy powder.

[0097] 6. Using a hydrostatic pressure method, powder with a particle size of 1.5 μm was pressed at a pressure of 180 MPa to form a compact weighing 3.0 kg. The compact was then pre-sintered at a low temperature under a hydrogen atmosphere to increase its strength.

[0098] 7. In the high-temperature sintering method, a method combining rapid heating and extended heating time was used at the intermediate heating point. The sintering temperature curve was as follows: The room temperature was set to A1, the heating time H1 was 6h, A1 reached 1100°C, A1 was kept warm for H2 time, H2 was 2, the temperature was raised from A1 to A2, the heating time was H3, H3 was 2h, A2 reached 1400°C, A2 was kept warm for H4 time, H4 was 3.5, the temperature was raised from A2 to A3, the heating time was H5, H5 was 2h, A3 reached 1800°C, A3 was kept warm for H6 time, H6 was 2, the temperature was raised from A3 to A4, the heating time was H7, H7 was 2h, A4 reached 2100°C, A4 was kept warm for H8 time, H8 was 6, and the sample was obtained by natural cooling from A4. Here, by controlling the intermediate frequency sintering time to control the rate of pore occlusion and shrinkage of the streaks, oxide particles with a particle size of less than 2.0 μm and a density of 18.0 g / cm³ are achieved. 3 A sintered element strip was obtained.

[0099] 8. Using multi-pass rotary forging and drawing, a sintered strip with a diameter of 17 mm was processed into a 2.0 mm standard wire. Subsequently, oxide annealing was performed in an oxide annealing apparatus under annealing conditions of 1400°C at a temperature and an annealing speed of 5 m / min. After annealing was completed, it was further processed into a rare earth tungsten alloy black wire with a diameter of 0.52 mm ± 0.005 mm. Here, the multi-pass rotary forging and drawing processes were performed using the standard drawing process. The process parameters were as follows: the wire diameter was set to a standard of 3.7 mm by multi-pass rotary forging, then drawn to 2.0 mm, annealed, and further processed into a tungsten-lanthanum alloy black wire of 0.52 ± 0.005 mm.

[0100] 9. Using an electrolytic cleaning method, 0.52 mm black wire was cleaned to produce 0.50 mm ± 0.005 mm tungsten-lanthanum alloy white wire, which can be used as filament for microwave heating devices.

[0101] A 10.0.50mm tungsten-lanthanum alloy white wire was wound with 10 turns and a pitch of 1.29±0.03mm to create a spring-shaped cathode filament for a heating device.

[0102] 11. The filament and components such as the assembly, ceramic, and lead pieces were assembled into a cathode structure by heat treatment at a temperature of 600°C.

[0103] 12. The filament and the end cap of the assembly in the cathode structure were welded together as a single unit.

[0104] 13. The cathode structure was placed in a carbonization tank and carbonized. After exhausting the tank, a carbon-containing hydrocarbon gas (specifically, methane) was introduced, and a constant DC current (current value 16A) was passed through the cathode to heat it, completing the carbonization of the filament in the hydrocarbon gas.

[0105] 14. Assembly of the white ball: The cathode structure, anode tube, antenna end cap, and other components were assembled as a single unit.

[0106] 15. The white sphere was evacuated and vacuum-suctioned, and high-temperature aging was performed to complete the production of the black sphere and the activation of its emission performance.

[0107] 16. The black sphere, heat sink, magnet, tube shell, etc. were assembled to finally manufacture the heating device components, including the filament mentioned above, and then incorporated into a microwave oven for use.

[0108] Example 2 1. Following the formulation in Table 1, 5 L of deionized water was added to a predetermined amount of lanthanum nitrate-yttrium nitrate solution, and the mixture was stirred for 10 minutes to dissolve completely. Then, 1 L of aqueous ammonia solution (NH3·H2O) was added, and the mixture was stirred to neutralize it. The prepared mixed solution was then uniformly sprayed onto blue tungsten oxide in a doping pot and stirred. The volume ratio of lanthanum nitrate-yttrium nitrate solution to aqueous ammonia solution (NH3·H2O) was 5:1.

[0109] 2. The doping pot was vacuum-suctioned, heated with water (heating temperature 80°C, vacuum degree -0.025 MPa), and stirred while heating.

[0110] 3. The powder was dried under vacuum by steam heating, with the steam pressure set to 0.1-0.3 MPa and the vacuum level in the pot to -0.02 MPa or less. Finally, a uniformly doped tungsten-lanthanum yttrium doped powder with a low impurity content was obtained.

[0111] 4. Tungsten-lanthanum yttrium doped powder was reduced collectively in a reduction furnace with four temperature zones at 650°C, 750°C, 850°C, and 900°C to obtain tungsten-lanthanum yttrium powder with appropriate particle size.

[0112] 5. The obtained tungsten-lanthanum yttrium powder and tungsten carbide were placed in a high-speed powder mixer and subjected to solid-solid mixing for 2 hours. The mixture was then sieved to obtain a mixed tungsten-lanthanum yttrium alloy powder.

[0113] 6. Using a hydrostatic pressure method, powder with a particle size of 1.5 μm was pressed at a pressure of 180 MPa to form a compact weighing 3.0 kg. The compact was then pre-sintered at a low temperature under a hydrogen atmosphere to increase its strength.

[0114] 7. In the high-temperature sintering method, a method combining rapid heating and extended heating time was used at the intermediate heating point. The sintering temperature curve was as follows: The room temperature is set to A1, the heating time H1 is 5 hours, and A1 reaches 950°C. A1 is then kept warm for H2 hours, and H2 reaches 3 hours. The temperature is then raised from A1 to A2, the heating time is H3, H3 is 1.5 hours, and A2 reaches 1300°C. The sample was kept warm in A2 for H4 time, with H4 being 4.5°C. The temperature was then increased from A2 to A3 for H5 time, with H5 being 1 hour, resulting in A3 reaching 1700°C. The sample was then kept warm in A3 for H6 time, with H6 being 3°C. The temperature was then increased from A3 to A4 for H7 time, with H7 being 1 hour, resulting in A4 reaching 2050°C. The sample was kept warm in A4 for H8 time, with H8 being 10°C, and then allowed to cool naturally from A4.

[0115] 8. Using multi-pass rotary forging and drawing, a sintered strip with a diameter of 17 mm was processed into a 2.0 mm standard wire. Subsequently, annealing was performed in an annealing apparatus at a temperature of 1200°C and an annealing speed of 3 m / min. After annealing was complete, the material was further processed into a tungsten-lanthanum yttrium alloy black wire with a diameter of 0.52 mm ± 0.005 mm. Other conditions were the same as in Example 1.

[0116] 9. Using an electrolytic cleaning method, 0.52 mm black wire was cleaned to produce 0.50 mm ± 0.005 mm tungsten-lanthanum yttrium alloy white wire, which can be used as filament for microwave heating devices.

[0117] A 10.0.50mm tungsten-lanthanum yttrium alloy white wire was wound with 10 turns and a pitch of 1.29±0.03mm to create a spring-shaped cathode filament for a heating device.

[0118] 11. The filament and components such as the assembly, ceramic, and lead pieces were assembled into a cathode structure by heat treatment at a temperature of 600°C.

[0119] 12. The filament and the end cap of the assembly in the cathode structure were welded together as a single unit.

[0120] 13. The cathode structure was placed in a carbonization tank and carbonized. After exhausting the tank, a carbon-containing hydrocarbon gas (specifically, methane) was introduced, and a constant DC current (current value 16A) was passed through the cathode to heat it, completing the carbonization of the filament in the hydrocarbon gas.

[0121] 14. Assembly of the white ball: The cathode structure, anode tube, antenna end cap, and other components were assembled as a single unit.

[0122] 15. The white sphere was evacuated and vacuum-suctioned, and high-temperature aging was performed to complete the production of the black sphere and the activation of its emission performance.

[0123] 16. The black sphere, heat sink, magnet, tube shell, etc. were assembled to finally manufacture the heating device components, including the filament mentioned above, and then incorporated into a microwave oven for use.

[0124] Example 3 1. Following the formulation in Table 1, 5 L of deionized water was added to a predetermined amount of lanthanum nitrate-zirconium nitrate solution, and the mixture was stirred for 10 minutes to dissolve completely. Then, 1 L of aqueous ammonia solution (NH3·H2O) was added, and the mixture was stirred to neutralize it. The prepared mixed solution was then uniformly sprayed onto blue tungsten oxide in a doping pot and stirred. The ratio of lanthanum nitrate-zirconium nitrate solution to aqueous ammonia solution (NH3·H2O) was 5:1.

[0125] 2. The doping pot was vacuum-suctioned, heated with water (heating temperature 80°C, vacuum degree -0.025 MPa), and stirred while heating.

[0126] 3. The powder was dried under vacuum by steam heating, with the steam pressure set to 0.1-0.3 MPa and the vacuum level in the pot to -0.02 MPa or less. Finally, a uniformly doped tungsten-lanthanum zirconium doped powder with a low impurity content was obtained.

[0127] 4. Tungsten-lanthanum zirconium doped powder was reduced collectively in a reduction furnace with four temperature zones at 650°C, 750°C, 850°C, and 900°C to obtain tungsten-lanthanum zirconium powder with appropriate particle size.

[0128] 5. The obtained tungsten-lanthanum zirconium powder and tungsten carbide were placed in a high-speed powder mixer and solid-solid mixing was performed for 2 hours. The mixture was then sieved to obtain a mixed tungsten-lanthanum zirconium alloy powder.

[0129] 6. Using a hydrostatic pressure method, powder with a particle size of 1.5 μm was pressed at a pressure of 180 MPa to form a compact weighing 3.0 kg. The compact was then pre-sintered at a low temperature under a hydrogen atmosphere to increase its strength.

[0130] 7. In the high-temperature sintering method, a method combining rapid heating and extended heating time was used at the intermediate heating point. The sintering temperature curve was as follows: The room temperature is set to A1, the heating time H1 is 8 hours, and A1 reaches 1250°C. A1 is then maintained for H2 hours, and H2 is 1. The temperature is then raised from A1 to A2, the heating time is H3, H3 is 2.5 hours, and A2 reaches 1500°C. The sample was kept warm in A2 for H4 time, with H4 being 2.5. The temperature was then increased from A2 to A3 for H5 time, with H5 being 3 hours, resulting in A3 reaching 1900°C. The sample was then kept warm in A3 for H6 time, with H6 being 1. The temperature was then increased from A3 to A4 for H7 time, with H7 being 3 hours, resulting in A4 reaching 2250°C. The sample was kept warm in A4 for H8 time, with H8 being 5, and then allowed to cool naturally from A4.

[0131] 8. Using multi-pass rotary forging and drawing, a sintered strip with a diameter of 17 mm was processed into a 2.0 mm standard wire. Subsequently, oxide annealing was performed in an oxide annealing apparatus under annealing conditions of 1500°C at a temperature and annealing speed of 10 m / min. After annealing was completed, it was further processed into a tungsten-lanthanum zirconium alloy black wire with a diameter of 0.52 mm ± 0.005 mm.

[0132] 9. A 0.52 mm black wire was cleaned using an electrolytic cleaning method to obtain a 0.50 mm ± 0.005 mm tungsten-lanthanum zirconium alloy white wire that can be used for processing into filaments for microwave heating devices. Other conditions were the same as in Example 1.

[0133] A 10.0.50 mm tungsten-lanthanum zirconium alloy white wire was wound with 10 turns and a pitch of 1.29 ± 0.03 mm to create a spring-shaped cathode filament for a heating device.

[0134] 11. The filament and components such as the assembly, ceramic, and lead pieces were assembled into a cathode structure by heat treatment at a temperature of 600°C.

[0135] 12. The filament and the end cap of the assembly in the cathode structure were welded together as a single unit.

[0136] 13. The cathode structure was placed in a carbonization tank and carbonized. After exhausting the tank, a carbon-containing hydrocarbon gas (specifically, methane) was introduced, and a constant DC current (current value 16A) was passed through the cathode to heat it, completing the carbonization of the filament in the hydrocarbon gas.

[0137] 14. Assembly of the white ball: The cathode structure, anode tube, antenna end cap, and other components were assembled as a single unit.

[0138] 15. The white sphere was evacuated and vacuum-suctioned, and high-temperature aging was performed to complete the production of the black sphere and the activation of its emission performance.

[0139] 16. The black sphere, heat sink, magnet, tube shell, etc. were assembled to finally manufacture the heating device components, including the filament mentioned above, and then incorporated into a microwave oven for use.

[0140] Example 4 1. Following the formulation in Table 1, 5 L of deionized water was added to a predetermined amount of lanthanum nitrate-scandium nitrate solution, and the mixture was stirred for 10 minutes to dissolve completely. Then, 1 L of aqueous ammonia solution (NH3·H2O) was added, and the mixture was stirred to neutralize it. The prepared mixed solution was then uniformly sprayed onto blue tungsten oxide in a doping pot and stirred. The ratio of lanthanum nitrate-scandium nitrate solution to aqueous ammonia solution (NH3·H2O) was 5:1.

[0141] 2. The doping pot was vacuum-suctioned, heated with water (heating temperature 80°C, vacuum degree -0.025 MPa), and stirred while heating.

[0142] 3. The powder was dried under vacuum by steam heating, with the steam pressure set to 0.1-0.3 MPa and the vacuum level in the pot to -0.02 MPa or less. Finally, a uniformly doped tungsten-lanthanum scandium doped powder with a low impurity content was obtained.

[0143] 4. Tungsten-lanthanum scandium doped powder was reduced collectively in a reduction furnace with four temperature zones at 650°C, 750°C, 850°C, and 900°C to obtain tungsten-lanthanum scandium powder with appropriate particle size.

[0144] 5. The obtained tungsten-lanthanum scandium powder and tungsten carbide were placed in a high-speed powder mixer and subjected to solid-solid mixing for 2 hours. The mixture was then sieved to obtain a mixed tungsten-lanthanum scandium alloy powder.

[0145] 6. Using a hydrostatic pressure method, powder with a particle size of 1.5 μm was pressed at a pressure of 180 MPa to form a compact weighing 3.0 kg. The compact was then pre-sintered at a low temperature under a hydrogen atmosphere to increase its strength.

[0146] 7. By high-temperature sintering, oxide particles with a particle size of less than 2.0 μm and a density of 18.0 g / cm³ are produced. 3 A sintered element strip was obtained. Here, the process and conditions of this step were the same as in Example 1.

[0147] 8. Using multi-pass rotary forging and drawing, a sintered strip with a diameter of 17 mm was processed into a tungsten-lanthanum scandium alloy black wire with a diameter of 0.52 mm ± 0.005 mm. Here, the process and conditions for this step were the same as in Example 1.

[0148] 9. Using an electrolytic cleaning method, 0.52 mm black wire was cleaned to produce 0.50 mm ± 0.005 mm tungsten-lanthanum scandium alloy white wire, which can be used as filament for microwave heating devices.

[0149] A 10.0.50 mm tungsten-lanthanum scandium alloy white wire was wound with 10 turns and a pitch of 1.29 ± 0.03 mm to create a spring-shaped cathode filament for a heating device.

[0150] 11. The filament and components such as the assembly, ceramic, and lead pieces were assembled into a cathode structure by heat treatment at a temperature of 600°C.

[0151] 12. The filament and the end cap of the assembly in the cathode structure were welded together as a single unit.

[0152] 13. The cathode structure was placed in a carbonization tank and carbonized. After exhausting the tank, a carbon-containing hydrocarbon gas (specifically, methane) was introduced, and a constant DC current (current value 16A) was passed through the cathode to heat it, completing the carbonization of the filament in the hydrocarbon gas.

[0153] 14. Assembly of the white ball: The cathode structure, anode tube, antenna end cap, and other components were assembled as a single unit.

[0154] 15. The white sphere was evacuated and vacuum-suctioned, and high-temperature aging was performed to complete the production of the black sphere and the activation of its emission performance.

[0155] 16. The black sphere, heat sink, magnet, tube shell, etc. were assembled to finally manufacture the heating device components, including the filament mentioned above, and then incorporated into a microwave oven for use.

[0156] Example 5 1. Following the formulation in Table 1, 5 L of deionized water was added to a predetermined amount of lanthanum nitrate-hafnium nitrate solution, and the mixture was stirred for 10 minutes to dissolve completely. Then, 1 L of aqueous ammonia solution (NH3·H2O) was added, and the mixture was stirred to neutralize it. The prepared mixed solution was then uniformly sprayed onto blue tungsten oxide in a doping pot and stirred. The ratio of lanthanum nitrate-hafnium nitrate solution to aqueous ammonia solution (NH3·H2O) was 5:1.

[0157] 2. The doping pot was vacuum-suctioned, heated with water (heating temperature 80°C, vacuum degree -0.025 MPa), and stirred while heating.

[0158] 3. The powder was dried under vacuum by steam heating, with the steam pressure set to 0.1-0.3 MPa and the vacuum level in the pot to -0.02 MPa or less. Finally, a uniformly doped tungsten-lanthanum hafnium doped powder with a low impurity content was obtained.

[0159] 4. Tungsten-lanthanum hafnium doped powder was reduced collectively in four reduction furnaces with temperatures of 650°C, 750°C, 850°C, and 900°C to obtain tungsten-lanthanum hafnium powder with appropriate particle size and a content of 0.3% La2O3 + 0.2% HfO2.

[0160] 5. The obtained tungsten-lanthanum hafnium powder and tungsten carbide were placed in a high-speed powder mixer and solid-solid mixing was performed for 2 hours. The mixture was then sieved to obtain a tungsten-lanthanum hafnium alloy powder containing 0.3% La2O3 + 0.2% HfO2 + 0.5% WC.

[0161] 6. Using a hydrostatic pressure method, powder with a particle size of 1.5 μm was pressed at a pressure of 180 MPa to form a compact weighing 3.0 kg. The compact was then pre-sintered at a low temperature under a hydrogen atmosphere to increase its strength.

[0162] 7. By high-temperature sintering, oxide particles with a particle size of less than 2.0 μm and a density of 18.0 g / cm³ are produced. 3 A sintered element strip was obtained. Here, the process and conditions of this step were the same as in Example 1.

[0163] 8. Using multi-pass rotary forging and drawing, a sintered strip with a diameter of 17 mm was processed into a tungsten-lanthanum hafnium alloy black wire with a diameter of 0.52 mm ± 0.005 mm. Here, the process and conditions for this step were the same as in Example 1.

[0164] 9. Using an electrolytic cleaning method, 0.52 mm black wire was cleaned to produce 0.50 mm ± 0.005 mm tungsten-lanthanum hafnium alloy white wire, which can be used as filament for microwave heating devices.

[0165] A 10.0.50 mm tungsten-lanthanum hafnium alloy white wire was wound with 10 turns and a pitch of 1.29 ± 0.03 mm to create a spring-shaped cathode filament for a heating device.

[0166] 11. The filament and components such as the assembly, ceramic, and lead pieces were assembled into a cathode structure by heat treatment at a temperature of 600°C.

[0167] 12. The filament and the end cap of the assembly in the cathode structure were welded together as a single unit.

[0168] 13. The cathode structure was placed in a carbonization tank and carbonized. After exhausting the tank, a carbon-containing hydrocarbon gas (specifically, methane) was introduced, and a constant DC current (current value 16A) was passed through the cathode to heat it, completing the carbonization of the filament in the hydrocarbon gas.

[0169] 14. Assembly of the white ball: The cathode structure, anode tube, antenna end cap, and other components were assembled as a single unit.

[0170] 15. The white sphere was evacuated and vacuum-suctioned, and high-temperature aging was performed to complete the production of the black sphere and the activation of its emission performance.

[0171] 16. The black sphere, heat sink, magnet, tube shell, etc. were assembled to finally manufacture the heating device components, including the filament mentioned above, and then incorporated into a microwave oven for use.

[0172] Example 6 1. Following the formulation in Table 1, 5 L of deionized water was added to a predetermined amount of lanthanum nitrate-hafnium nitrate solution, and the mixture was stirred for 10 minutes to dissolve completely. Then, 1 L of aqueous ammonia solution (NH3·H2O) was added, and the mixture was stirred to neutralize it. The prepared mixed solution was then uniformly sprayed onto blue tungsten oxide in a doping pot and stirred. The ratio of lanthanum nitrate-hafnium nitrate solution to aqueous ammonia solution (NH3·H2O) was 5:1.

[0173] 2. The doping pot was vacuum-suctioned, heated with water (heating temperature 80°C, vacuum degree -0.025 MPa), and stirred while heating.

[0174] 3. The powder was dried under vacuum by steam heating, with the steam pressure set to 0.1-0.3 MPa and the vacuum level in the pot to -0.02 MPa or less. Finally, a uniformly doped tungsten-lanthanum hafnium doped powder with a low impurity content was obtained.

[0175] 4. Tungsten-lanthanum hafnium doped powder was reduced collectively in four temperature zones at 650°C, 750°C, 850°C, and 900°C to obtain tungsten-lanthanum hafnium powder with an appropriate particle size and a content of 2.0% La2O3 + 1.0% HfO2.

[0176] 5. The obtained tungsten-lanthanum hafnium powder and tungsten carbide were placed in a high-speed powder mixer and solid-solid mixing was performed for 2 hours. The mixture was then sieved to obtain a tungsten-lanthanum hafnium alloy powder containing 2.0% La2O3 + 1.0% HfO2 + 2.0% WC.

[0177] 6. Using a hydrostatic pressure method, powder with a particle size of 1.5 μm was pressed at a pressure of 180 MPa to form a compact weighing 3.0 kg. The compact was then pre-sintered at a low temperature under a hydrogen atmosphere to increase its strength.

[0178] 7. By high-temperature sintering, oxide particles with a particle size of less than 2.0 μm and a density of 18.0 g / cm³ are produced. 3 A sintered element strip was obtained. Here, the process and conditions of this step were the same as in Example 1.

[0179] 8. Using multi-pass rotary forging and drawing, a sintered strip with a diameter of 17 mm was processed into a tungsten-lanthanum hafnium alloy black wire with a diameter of 0.52 mm ± 0.005 mm. Here, the process and conditions for this step were the same as in Example 1.

[0180] 9. Using an electrolytic cleaning method, 0.52 mm black wire was cleaned to produce 0.50 mm ± 0.005 mm tungsten-lanthanum hafnium alloy white wire, which can be used as filament for microwave heating devices.

[0181] A 10.0.50 mm tungsten-lanthanum hafnium alloy white wire was wound with 10 turns and a pitch of 1.29 ± 0.03 mm to create a spring-shaped cathode filament for a heating device.

[0182] 11. The filament and components such as the assembly, ceramic, and lead pieces were assembled into a cathode structure by heat treatment at a temperature of 600°C.

[0183] 12. The filament and the end cap of the assembly in the cathode structure were welded together as a single unit.

[0184] 13. The cathode structure was placed in a carbonization tank and carbonized. After exhausting the tank, a carbon-containing hydrocarbon gas (specifically, methane gas) was introduced, and a constant DC current (current value 16A) was passed through the cathode to heat it, completing the carbonization of the filament in the hydrocarbon gas.

[0185] 14. Assembly of the white ball: The cathode structure, anode tube, antenna end cap, and other components were assembled as a single unit.

[0186] 15. The white sphere was evacuated and vacuum-suctioned, and high-temperature aging was performed to complete the production of the black sphere and the activation of its emission performance.

[0187] 16. The black sphere, heat sink, magnet, tube shell, etc. were assembled to finally manufacture the heating device components, including the filament mentioned above, and then incorporated into a microwave oven for use.

[0188] Example 7 1. Following the formulation in Table 1, a predetermined amount of lanthanum nitrate was added to 5 L of deionized water and stirred for 10 minutes to dissolve completely. Then, 1 L of aqueous ammonia solution (NH3·H2O) was added and stirred to neutralize. The prepared mixed solution was uniformly sprayed onto blue tungsten oxide in a doping pot and stirred. The volume ratio of lanthanum nitrate solution to aqueous ammonia solution (NH3·H2O) was 5:1.

[0189] 2. The doping pot was vacuum-suctioned, heated with water (heating temperature 80°C, vacuum degree -0.025 MPa), and stirred while heating.

[0190] 3. The powder was dried under vacuum by steam heating, with the steam pressure set to 0.1-0.3 MPa and the vacuum level in the pot to -0.02 MPa or less. Finally, a uniformly doped tungsten-lanthanum doped powder with a low impurity content was obtained.

[0191] 4. Tungsten-lanthanum doped powder was reduced collectively in a reduction furnace with four temperature zones at 650°C, 750°C, 850°C, and 900°C to obtain tungsten-lanthanum powder with appropriate particle size.

[0192] 5. Following the formulation in Table 1, 5 L of deionized water was added to the doping pot and heated to 80°C. Then, a predetermined amount of ammonium rhenate was added and stirred for 10 minutes to dissolve completely. After that, a predetermined amount of tungsten-lanthanum powder was added to the ammonium rhenate solution and stirred for 30 minutes. Then, under vacuum, the powder was dried by steam heating, with the steam pressure set to 0.1-0.3 MPa and the vacuum level in the pot to -0.02 MPa or less. Finally, a uniformly doped rhenium-doped tungsten-lanthanum powder with a low impurity content was obtained.

[0193] 6. Rhenium-doped tungsten-lanthanum powder was reduced collectively in four reduction furnaces with temperatures of 650°C, 750°C, 850°C, and 900°C to produce tungsten-lanthanum-rhenium alloy powder with a particle size of 1.5 μm.

[0194] 7. The obtained tungsten-lanthanum-rhenium alloy powder and tungsten carbide were placed in a high-speed powder mixer and subjected to solid-solid mixing for 2 hours. The mixture was then sieved to obtain mixed tungsten-lanthanum-rhenium alloy powder.

[0195] 8. Using a hydrostatic pressure method, powder with a particle size of 1.5 μm was pressed at a pressure of 180 MPa to form a compact weighing 3.0 kg. The compact was then pre-sintered at a low temperature under a hydrogen atmosphere to increase its strength.

[0196] 9. By high-temperature sintering, oxide particles with a particle size of less than 2.0 μm and a density of 18.0 g / cm³ are produced. 3 A sintered element strip was obtained. Here, the process and conditions of this step were the same as in Example 1.

[0197] 10. Using multi-pass rotary forging and drawing, a sintered strip with a diameter of 17 mm was processed into a tungsten-lanthanum-rhenium alloy black wire with a diameter of 0.52 mm ± 0.005 mm. Here, the process and conditions for this step were the same as in Example 1.

[0198] 11. Using an electrolytic cleaning method, a 0.52 mm black wire was cleaned to produce a 0.50 mm ± 0.005 mm tungsten-lanthanum-rhenium alloy white wire that can be used as a filament for microwave heating devices.

[0199] A 12.0.50mm tungsten-lanthanum-rhenium alloy white wire was wound with 10 turns and a pitch of 1.29±0.03mm to create a spring-shaped cathode filament for a heating device.

[0200] 13. The filament and components such as the assembly, ceramic, and lead pieces were assembled into a cathode structure by heat treatment at a temperature of 600°C.

[0201] 14. The filament and the end cap of the assembly in the cathode structure were welded together as a single unit.

[0202] 15. The cathode structure was placed in a carbonization tank and carbonized. After exhausting the tank, a carbon-containing hydrocarbon gas (specifically, methane) was introduced, and a constant DC current (current value 16A) was passed through the cathode to heat it, completing the carbonization of the filament in the hydrocarbon gas.

[0203] 16. Assembly of the white ball: Components such as the cathode structure, anode tube, and antenna end cap were assembled as a single unit.

[0204] 17. The white sphere was evacuated and vacuum-suctioned, and high-temperature aging was performed to complete the production of the black sphere and the activation of its emission performance.

[0205] 18. The black sphere, heat sink, magnet, tube shell, etc. were assembled to finally manufacture the heating device components, including the filament mentioned above, and then incorporated into a microwave oven for use.

[0206] Comparative Example 1: 1. Following the formulation in Table 1, 5 L of deionized water was added to a predetermined amount of thorium nitrate solution and stirred for 10 minutes to dissolve completely. Then, 1 L of aqueous ammonia solution (NH3·H2O) was added and stirred to neutralize. The prepared mixed solution was uniformly sprayed onto blue tungsten oxide in a doping pot and stirred. The ratio of thorium nitrate solution to aqueous ammonia solution (NH3·H2O) was 5:1.

[0207] 2. The doping pot was vacuum-suctioned, heated with water (heating temperature 80°C, vacuum degree -0.025 MPa), and stirred while heating.

[0208] 3. The powder was dried under vacuum by steam heating, with the steam pressure set to 0.1-0.3 MPa and the vacuum level in the pot to -0.02 MPa or less. Finally, a uniformly doped thorium-tungsten doped powder with a low impurity content was obtained.

[0209] 4. Thorium-tungsten doped powder was reduced collectively in four reduction furnaces with temperatures of 650°C, 750°C, 850°C, and 900°C to produce tungthorium-tungsten powder with a particle size of 1.5 μm.

[0210] 5. The obtained thorium-tungsten powder was placed in a V-type powder mixer and mixed for 2 hours, then sieved to obtain mixed thorium-tungsten powder.

[0211] 6. Using a hydrostatic method, tungthorium-tungsten powder with a particle size of 1.5 μm was pressed at a pressure of 180 MPa to form a compact weighing 3.0 kg. The compact was then pre-sintered at a low temperature under a hydrogen atmosphere to increase its strength.

[0212] 7. By high-temperature sintering, thorium oxide particles with a particle size of less than 2.0 μm and a density of 18.0 g / cm³ are produced. 3 A sintered element strip was obtained. Here, the process and conditions of this step were the same as in Example 1.

[0213] 8. Using multi-pass rotary forging and drawing, a sintered strip with a diameter of 17 mm was processed into a thorium-tungsten alloy black wire with a diameter of 0.52 mm ± 0.005 mm. Here, the process and conditions for this step were the same as in Example 1.

[0214] 9. Using an electrolytic cleaning method, a 0.52 mm black wire was cleaned to produce a 0.50 mm ± 0.005 mm thorium-tungsten alloy white wire that can be used as a filament for microwave heating devices.

[0215] A 10.0.50 mm thorium-tungsten white wire was wound with 10 turns and a pitch of 1.29 ± 0.03 mm to create a spring-shaped cathode filament for a heating device.

[0216] 11. The filament and components such as the assembly, ceramic, and lead pieces were assembled into a cathode structure by heat treatment at a temperature of 600°C.

[0217] 12. The filament and the end cap of the assembly in the cathode structure were welded together as a single unit.

[0218] 13. The cathode structure was placed in a carbonization tank and carbonized. After exhausting the tank, a carbon-containing hydrocarbon gas (methane gas) was introduced, and a constant DC current (current value 16A) was passed through the cathode to heat it, completing the carbonization of the filament in the hydrocarbon gas.

[0219] 14. Assembly of the white ball: The cathode structure, anode tube, antenna end cap, and other components were assembled as a single unit.

[0220] 15. The white sphere was evacuated and vacuum-suctioned, and high-temperature aging was performed to complete the production of the black sphere and the activation of its emission performance.

[0221] 16. The black sphere, heat sink, magnet, tube shell, etc. were assembled to finally manufacture the heating device components, including the filament mentioned above, and then incorporated into a microwave oven for use.

[0222] Comparative Example 2: 1. Following the formulation in Table 1, 5 L of deionized water was added to a predetermined amount of lanthanum nitrate-yttrium nitrate solution, and the mixture was stirred for 10 minutes to dissolve completely. Then, 1 L of aqueous ammonia solution (NH3·H2O) was added, and the mixture was stirred to neutralize it. The prepared mixed solution was then uniformly sprayed onto blue tungsten oxide in a doping pot and stirred. The ratio of lanthanum nitrate-yttrium nitrate solution to aqueous ammonia solution (NH3·H2O) was 5:1.

[0223] 2. The doping pot was vacuum-suctioned, heated with water (heating temperature 80°C, vacuum degree -0.025 MPa), and stirred while heating.

[0224] 3. The powder was dried under vacuum by steam heating, with the steam pressure set to 0.1-0.3 MPa and the vacuum level in the pot to -0.02 MPa or less. Finally, a uniformly doped tungsten-lanthanum yttrium doped powder with a low impurity content was obtained.

[0225] 4. The tungsten-lanthanum yttrium-doped powder was reduced in one batch in a reduction furnace with four temperature zones at 650 °C, 750 °C, 850 °C, and 900 °C to obtain tungsten-lanthanum yttrium powder with a particle size of 1.5 μm.

[0226] 5. The obtained tungsten-lanthanum yttrium powder was put into a V-type powder mixer and mixed for 2 hours, and then sieved to obtain mixed tungsten-lanthanum yttrium alloy powder.

[0227] 6. By the isostatic pressing method, the tungsten-lanthanum yttrium alloy powder with a particle size of 1.5 μm was pressed at a pressure of 180 MPa to obtain a green compact with a single weight of 3.0 kg. The green compact was pre-sintered at a low temperature under a hydrogen atmosphere to increase the strength of the green compact.

[0228] 7. By the high-temperature sintering method, a sintered blank with an oxide particle diameter of less than 2.0 μm and a density of 18.0 g / cm 3 was obtained. Here, the process and conditions of this step were the same as those in Example 1.

[0229] 8. Using multi-pass rotary forging and drawing processes, the sintered blank with a diameter of 17 mm was processed into a tungsten-lanthanum yttrium alloy black wire with a diameter of 0.52 mm ± 0.005 mm. Here, the process and conditions of this step were the same as those in Example 1.

[0230] 9. The 0.52 mm black wire was cleaned by an electrolytic cleaning method to obtain a tungsten-lanthanum yttrium alloy white wire with a diameter of 0.50 mm ± 0.005 mm that can be used for processing into the filament of a heating device in a microwave oven.

[0231] 10. The 0.50 mm tungsten-lanthanum yttrium alloy white wire was wound with 10 turns and a pitch of 1.29 ± 0.03 mm to form a spring-shaped cathode filament for a heating device.

[0232] 11. The filament and components such as the assembly, ceramic, and lead pieces were assembled into a cathode structure by heat treatment at a temperature of 600°C.

[0233] 12. The filament and the end cap of the assembly in the cathode structure were welded together as a single unit.

[0234] 13. The cathode structure was placed in a carbonization tank and carbonized. After exhausting the tank, a carbon-containing hydrocarbon gas (specifically, methane) was introduced, and a constant DC current (current value 16A) was passed through the cathode to heat it, completing the carbonization of the filament in the hydrocarbon gas.

[0235] 14. Assembly of the white ball: The cathode structure, anode tube, antenna end cap, and other components were assembled as a single unit.

[0236] 15. The white sphere was evacuated and vacuum-suctioned, and high-temperature aging was performed to complete the production of the black sphere and the activation of its emission performance.

[0237] 16. The black sphere, heat sink, magnet, tube shell, etc. were assembled to finally manufacture the heating device components, including the filament mentioned above, and then incorporated into a microwave oven for use.

[0238] Comparative Example 3: 1. Following the formulation in Table 1, 5 L of deionized water was added to a predetermined amount of lanthanum nitrate-scandium nitrate solution, and the mixture was stirred for 10 minutes to dissolve completely. Then, 1 L of aqueous ammonia solution (NH3·H2O) was added, and the mixture was stirred to neutralize it. The prepared mixed solution was then uniformly sprayed onto blue tungsten oxide in a doping pot and stirred. The ratio of lanthanum nitrate-scandium nitrate solution to aqueous ammonia solution (NNH3·H2O) was 5:1.

[0239] 2. The doping pot was vacuum-suctioned, heated with water (heating temperature 80°C, vacuum degree -0.025 MPa), and stirred while heating.

[0240] 3. The powder was dried under vacuum by steam heating, with the steam pressure set to 0.1-0.3 MPa and the vacuum level in the pot to -0.02 MPa or less. Finally, a uniformly doped tungsten-lanthanum scandium doped powder with a low impurity content was obtained.

[0241] 4. Tungsten-lanthanum scandium-doped powder was reduced collectively in four reduction furnaces with temperatures of 650°C, 750°C, 850°C, and 900°C to produce tungsten-lanthanum scandium powder with a particle size of 1.5 μm.

[0242] 5. The obtained tungsten-lanthanum scandium powder was placed in a V-type powder mixer and mixed for 2 hours, then sieved to obtain a mixed tungsten-lanthanum scandium alloy powder.

[0243] 6. Using a hydrostatic pressure method, powder with a particle size of 1.5 μm was pressed at a pressure of 180 MPa to form a compact weighing 3.0 kg. The compact was then pre-sintered at a low temperature under a hydrogen atmosphere to increase its strength.

[0244] 7. By high-temperature sintering, oxide particles with a particle size of less than 2.0 μm and a density of 18.0 g / cm³ are produced. 3 A sintered element strip was obtained. Here, the process and conditions of this step were the same as in Example 1.

[0245] 8. Using multi-pass rotary forging and drawing, a sintered strip with a diameter of 17 mm was processed into a tungsten-lanthanum scandium alloy black wire with a diameter of 0.52 mm ± 0.005 mm. Here, the process and conditions for this step were the same as in Example 1.

[0246] 9. Using an electrolytic cleaning method, 0.52 mm black wire was cleaned to produce 0.50 mm ± 0.005 mm tungsten-lanthanum scandium alloy white wire, which can be used as filament for microwave heating devices.

[0247] A 10.0.50 mm tungsten-lanthanum scandium alloy white wire was wound with 10 turns and a pitch of 1.29 ± 0.03 mm to create a spring-shaped cathode filament for a heating device.

[0248] 11. The filament and components such as the assembly, ceramic, and lead pieces were assembled into a cathode structure by heat treatment at a temperature of 600°C.

[0249] 12. The filament and the end cap of the assembly in the cathode structure were welded together as a single unit.

[0250] 13. The cathode structure was placed in a carbonization tank and carbonized. After exhausting the tank, a carbon-containing hydrocarbon gas was introduced (specifically, methane gas is preferred), and a DC current of a constant value (preferably 16A) was passed through the cathode to heat it, completing the carbonization of the filament in the hydrocarbon gas.

[0251] 14. Assembly of the white ball: The cathode structure, anode tube, antenna end cap, and other components were assembled as a single unit.

[0252] 15. The white sphere was evacuated and vacuum-suctioned, and high-temperature aging was performed to complete the production of the black sphere and the activation of its emission performance.

[0253] 16. The black sphere, heat sink, magnet, tube shell, etc. were assembled to finally manufacture a heating device component (i.e., a heating device) containing the filament described above, which was then incorporated into a microwave oven for use.

[0254] Comparative Example 4 1. Following the formulation in Table 1, a predetermined amount of lanthanum nitrate was added to 5 L of deionized water and stirred for 10 minutes to dissolve completely. Then, 1 L of aqueous ammonia solution (NH3·H2O) was added and stirred to neutralize. The prepared mixed solution was uniformly sprayed onto blue tungsten oxide in a doping pot and stirred. The volume ratio of lanthanum nitrate solution to aqueous ammonia solution (NH3·H2O) was 5:1.

[0255] 2. The doping pot was subjected to vacuum suction, heated with water (heating temperature 80°C, vacuum degree -0.025 MPa), and stirred while heating.

[0256] 3. In a vacuum state, the powder was dried by steam heating, the steam pressure was set to 0.1 - 0.3 MPa, and the vacuum degree inside the pot was set to -0.02 MPa or less. Finally, tungsten-lanthanum doped powder with uniform doping and low impurity content was obtained.

[0257] 4. The tungsten-lanthanum doped powder was collectively reduced in a reduction furnace with four temperature zones at 650°C, 750°C, 850°C, and 900°C to obtain tungsten-lanthanum powder with appropriate particle size.

[0258] 5. According to the formulation in Table 1, 5 L of deionized water was added to the doping pot and heated to 80°C. Then, a predetermined amount of ammonium perrhenate was added and stirred for 10 minutes to fully dissolve. After that, a predetermined amount of tungsten-lanthanum powder was added to the ammonium perrhenate solution and stirred for 30 minutes. Then, in a vacuum state, the powder was dried by steam heating, the steam pressure was 0.1 - 0.3 MPa, and the vacuum degree inside the pot was -0.02 MPa or less. Finally, rhenium-doped tungsten-lanthanum powder with uniform doping and low impurity content was obtained.

[0259] 6. The rhenium-doped tungsten-lanthanum powder was collectively reduced in a reduction furnace with four temperature zones at 650°C, 750°C, 850°C, and 900°C to obtain tungsten-lanthanum-rhenium alloy powder with a particle size of 1.5 μm.

[0260] 7. The obtained tungsten-lanthanum-rhenium alloy powder and tungsten carbide were put into a high-speed powder mixer, and solid-solid mixing was carried out for 2 hours, followed by sieving to obtain mixed tungsten-lanthanum-rhenium alloy powder.

[0261] 8. Using a hydrostatic pressure method, powder with a particle size of 1.5 μm was pressed at a pressure of 180 MPa to form a compact weighing 3.0 kg. The compact was then pre-sintered at a low temperature under a hydrogen atmosphere to increase its strength.

[0262] 9. By high-temperature sintering, oxide particles with a particle size of less than 2.0 μm and a density of 18.0 g / cm³ are produced. 3 A sintered element strip was obtained. Here, the process and conditions of this step were the same as in Example 1.

[0263] 10. Using multi-pass rotary forging and drawing, a sintered strip with a diameter of 17 mm was processed into a tungsten-lanthanum-rhenium alloy black wire with a diameter of 0.52 mm ± 0.005 mm. Here, the process and conditions for this step were the same as in Example 1.

[0264] 11. Using an electrolytic cleaning method, a 0.52 mm black wire was cleaned to produce a 0.50 mm ± 0.005 mm tungsten-lanthanum-rhenium alloy white wire that can be used as a filament for microwave heating devices.

[0265] A 12.0.50mm tungsten-lanthanum-rhenium alloy white wire was wound with 10 turns and a pitch of 1.29±0.03mm to create a spring-shaped cathode filament for a heating device.

[0266] 13. The filament and components such as the assembly, ceramic, and lead pieces were assembled into a cathode structure by heat treatment at a temperature of 600°C.

[0267] 14. The filament and the end cap of the assembly in the cathode structure were welded together as a single unit.

[0268] 15. The cathode structure was placed in a carbonization tank and carbonized. After exhausting the tank, a carbon-containing hydrocarbon gas (specifically, methane) was introduced, and a constant DC current (current value 16A) was passed through the cathode to heat it, completing the carbonization of the filament in the hydrocarbon gas.

[0269] 16. Assembly of the white ball: Components such as the cathode structure, anode tube, and antenna end cap were assembled as a single unit.

[0270] 17. The white sphere was evacuated and vacuum-suctioned, and high-temperature aging was performed to complete the production of the black sphere and the activation of its emission performance.

[0271] 18. The black sphere, heat sink, magnet, tube shell, etc. were assembled to finally manufacture the heating device components, including the filament mentioned above, and then incorporated into a microwave oven for use.

[0272] Comparative Example 5 This comparative example differs from Example 1 only in the following respects: In this comparative example, during the multi-pass rotary forging and drawing steps, a sintered strip with a diameter of 17 mm was directly processed into a tungsten-lanthanum tungsten alloy black wire with a diameter of 0.52 mm ± 0.005 mm, and intermediate diameter wires were not subjected to the oxide annealing process. Other process and conditions were the same as in Example 1.

[0273] Comparative Example 6 This comparative example differs from Example 1 only in the following respects: In this comparative example, the heating curve for high-temperature sintering was obtained as follows: Room temperature was set to A1, heating time H1 was 6h, A1 was 1100°C, A1 was held for H2 time, H2 was 2h, heating was increased from A1 to A2, heating time H3, H3 was 3h, A2 was 1400°C, A2 was held for H4 time, H4 was 2h, heating was increased from A2 to A3, heating time H5, H5 was 2h, A3 was 1800°C, A3 was held for H6 time, H6 was 2h, heating was increased from A3 to A4, heating time H7, H7 was 2h, A4 was 2100°C, A4 was held for H8 time, H8 was 6h, and natural cooling was obtained from A4. Other process and conditions were the same as in Example 1.

[0274] Tungsten alloy wires, tungsten alloy filaments manufactured in the above Examples and Comparative Examples, and equipment (microwave oven) equipped with the above filament components were prepared, and the related performance indicators were tested under the same test conditions. The test results are shown in Tables 2 to 7 below.

[0275]

Table 2

[0276]

Table 3

[0277]

Table 4

[0278] Table comparing the data of Example 1, Comparative Example 1 (thorium-tungsten) and Comparative Examples 5 to 6

Table 5

[0279] Table comparing the data of the results of Example 1 and Comparative Example 6

Table 6

[0280] Table comparing the data of the results of Example 1 and Comparative Example 7

Table 7

[0281] In Tables 2-7, the test standard for the recrystallization temperature range item is GB T 23272-2009 Tungsten Wire for Lighting and Electronic Equipment. Here, FC represents the magnitude of the fusing current, and the conversion method between FC% and Celsius temperature is as follows. The high-temperature performance test method in Section 4.3.2.2 of the national standard GB / T 23272-2009 for Tungsten Wire for Lighting and Electronic Equipment, shown in Figure 19, shows the reference correspondence between FC% and temperature, and the conversion can be performed by referring to this correspondence. The electron work function is measured according to the Richardson linear method. The operating life of the tungsten alloy filament is tested according to Section 6.5.2 of the lifetime test method of the national standard GB / T 23152-2008 for heating devices for household microwave ovens, which requires that heating devices for microwave ovens operate continuously for more than 500 hours. In the example, the manufacturing flow of steps 10-14 and the test nodes for each test item are shown in Figure 18.

[0282] 1. Compare Example 1 with Comparative Example 1. Comparative Example 1 is a thorium-tungsten filament, and the initial recrystallization temperature of Comparative Example 1 is lower than the range limited in this application.

[0283] Figures 6-12 show the microstructure at different fusing currents for Example 1 and Comparative Example 1. It was found that the recrystallization temperature for Example 1 was 50% FC (approximately 2120°C), and the recrystallization temperature for Comparative Example 1 was 46% FC (approximately 2020°C). It was found that the initial recrystallization temperature of the filament material of the present invention is higher than that of existing thorium-tungsten wires.

[0284] 1.1. The initial recrystallization temperature affects the grain width of the carbide layer 200. Figures 13 and 14 show the grain size of the carbonized filaments in Example 1 and Comparative Example 1. Figure 14 shows that the carbonized filament structure of Example 1 remains fine-grained, while Figure 13 shows that the grain size of the carbonized filament structure of Comparative Example 1 is significantly larger. From the data, the number of crystal grains in the carbonized tungsten matrix 100 is 4000 grains / mm in Example 1.2 In Comparative Example 1, the result was 100 pieces / mm 2 Furthermore, it was found that the grain width of the carbide layer 200 was 6.83 μm in Example 1 and 9.81 μm in Comparative Example 1.

[0285] 1.2. The initial recrystallization temperature affects the grain width of the tungsten alloy filament, which in turn affects the channel distribution in the carbide layer 200, and thereby affects the release performance.

[0286] Figures 15-17 show the distribution of channels 210 in the carbonized filaments of Example 1 and Comparative Example 1. In Example 1, shown in Figure 15, the microstructure of the carbonized layer 200 in the cross-section of the carbonized filament shows that numerous first channels 211 are distributed almost perpendicular to the filament edge, and second channels 212 are distributed almost annularly, intersecting the first channels, indicating that the carbonized layer 200 is in a stacked block structure. In Example 1, shown in Figure 16, the microstructure of the carbonized layer 200 in the longitudinal section of the carbonized filament shows that numerous first channels 211 are distributed almost perpendicular to the filament edge. On the other hand, in Comparative Example 1, shown in Figure 17, the number of first channels 211 distributed almost perpendicular to the filament edge in the microstructure of the carbonized layer 200 in the cross-section of the carbonized filament is significantly reduced, and only a very small amount of parallel second channels 212 are distributed. An analysis of the cause revealed that the grain width of the carbide layer in Comparative Example 1 was relatively large, and the number of channels 210 is related to the grain size, meaning that the grain size affects the formation of channels 210.

[0287] In Embodiment 1 of the present invention, the layered structure separated by the second channel 212 in the carbide layer 200 is where the oxide of M is distributed, and the first channel 211 is distributed almost perpendicular to the filament edge, connecting the interior of the matrix 100, the second channel 212, and the filament edge. Since the second channel 212 is bonded to the first channel 211, it is advantageous for the rare earth atoms to move outward, and for the timely replenishment of rare earth elements evaporated from the surface, thereby improving the release stability of the material.

[0288] 1.3. The initial recrystallization temperature affects the grain width of tungsten carbide alloy filaments, which in turn affects the filament breakage rate.

[0289] Because thorium-tungsten filaments have a relatively low recrystallization temperature, after carbonization of the filament, the crystal grains of the recrystallized tungsten matrix of the filament become coarser, making the filament brittle. As a result, the vibration resistance of the magnetron is poor, the filament is prone to breakage, and ultimately the magnetron becomes inoperable. Here, the data from Comparative Example 1 clearly shows that the breakage rate and operating performance of the thorium-tungsten filament are significantly worse than those of Example 1.

[0290] Similarly, if the recrystallization temperature of the tungsten alloy wire of the present invention is lower than the range limited in the present invention (48%Fc to 56%Fc), after carbonization of the filament, the crystal grains of the recrystallized tungsten matrix of the filament become coarser, the filament becomes brittle, and as a result the vibration resistance of the magnetron is poor, the filament becomes more prone to breakage, and the breakage rate is worse than that of the examples.

[0291] 2. Comparison between Example 2 and Comparative Example 2, and comparison between Example 4 and Comparative Example 3 2.1 The difference between Example 2 and Comparative Example 2 is that Comparative Example 2 does not contain added carbide raw materials, and therefore does not contain carbon. As can be seen by comparing the results of both, in Comparative Example 2, the recrystallization temperature is lower, the grain width of the carbide layer is larger, and the carbide layer 200 has a block-like structure compared to Example 2. This is reflected in the performance, which is inferior in emission stability, inferior in electron emission performance, and shorter operating life.

[0292] 2.2 The difference between Example 4 and Comparative Example 3 is that Comparative Example 3 does not contain carbide raw materials, and therefore does not contain carbon. As can be seen by comparing the results of the two, in Comparative Example 3, the recrystallization temperature is lower, the grain width of the carbide layer is wider, and the carbide layer 200 has a block-like structure compared to Example 4. This is reflected in the performance, which is inferior in emission stability, inferior in electron emission performance, and shorter operating life.

[0293] Analysis of the mechanism reveals that in the embodiments of the present invention, by adding one or more types of M oxides and carbides, or elemental carbon, the M oxides and carbides in the tungsten matrix react at high temperatures, and the resulting M metal atoms become much smaller than the M oxide particles. The migration and diffusion rates of the M metal atoms in the tungsten matrix are accelerated, and therefore, equivalent or better electron emission capacity can be achieved at a lower operating voltage (excitation temperature) compared to thorium-tungsten filaments. On the other hand, in Comparative Examples 2 and 3, since no carbon raw material was added, the above effect was clearly not obtained, and the electron emission performance was poor.

[0294] 4. Comparison of Example 7 and Comparative Example 4 The difference between Example 7 and Comparative Example 4 is that the Re content in Comparative Example 4 exceeds the range limited in this application. As can be seen by comparing the results of the two, Comparative Example 4 has a higher operating temperature and a shorter operating life. The inventors' analysis revealed that rhenium has the effect of purifying grain boundaries and strengthening the solid solution of rhenium and tungsten. However, the added rhenium content exceeds the range limited in this application, and because the rhenium content is too high, the strengthening effect is too great, work hardening becomes excessive, and cracks are more likely to occur in the wire. Looking at the flaw detection data of the wire, it was revealed that the number of detected cracks was 0.8 to 1.5 per 100m in Example 7 and 6 to 10 per 100m in Comparative Example 5.

[0295] 5. Comparison of Example 1 with Comparative Examples 5-6 5.1. Compared to Example 1, the initial recrystallization temperature of Comparative Example 5 is higher than the range limited in this application. Compared to Example 1, comparative example 5 does not use an oxide annealing treatment to keep the initial recrystallization temperature of the tungsten alloy wire within a certain range. As a result, the initial recrystallization temperature of comparative example 5 is higher (higher than the range limited in this application), the number of cracks per 100m increases, and the yield decreases. It was found that simply increasing the temperature does not necessarily improve the effect of the initial recrystallization temperature, and that exceeding the range limited in this application can have adverse effects.

[0296] 5.2. Comparing Example 1 with Comparative Example 6, in Comparative Example 6, the average size of oxide particles exceeds the range limited in this application. Compared to Example 1, in Comparative Example 6, the average size of oxide particles in the raw strip is larger, and the average size of oxide particles in the cross-section of the 0.5 mm wire is also larger. Since the size of oxide particles affects processing performance, i.e., processing yield and flaw detection level, the number of cracks per 100 m increases and the yield decreases in the wire manufactured in this comparative example.

[0297] As described above, the following can be clearly concluded from the test results of the examples and comparative examples. 1. The manufacturing process of the filament includes a carbonization step at a carbonization temperature of 2000-2200°C. Existing thorium-tungsten filaments are carbonized at this temperature, causing recrystallization of the crystal grain structure, resulting in coarser crystal grains. As a result, the carbonized filament becomes very prone to breakage, and breakage occurs even with slightly increased vibration during the production process (the breakage rate is approximately 20,000-30,000 ppm).

[0298] The recrystallization temperatures measured for Examples 1 to 7 ranged from 48%FC (approximately 2070°C) to 52%FC (approximately 2180°C), while the recrystallization temperature for Comparative Example 1 was 46%FC (approximately 2020°C). The filament material produced by the present invention has a higher initial recrystallization temperature than existing thorium-tungsten filaments, and the filament structure after carbonization remains fine-grained (the crystal grain size of the examples of the present invention is significantly smaller than that of the comparative example), and filaments with a fine-grained structure are less prone to breakage.

[0299] 2. Observation of the carbide layer 200 in the cross-sectional, longitudinal, and longitudinal sections revealed that the recrystallization temperature of the tungsten alloy wire of the present invention falls within a certain range, the initial recrystallization temperature is higher than that of existing thorium-tungsten wires, and the filament structure remains fine-grained even after carbonization.

[0300] The carbide layer 200 of the thorium-free tungsten-lanthanum filament of the present invention has smaller crystal grain size and slightly narrower crystal grain width compared to the thorium-tungsten filament, resulting in a greater number of channels 210 in the carbide layer 200 of the present invention. The structure of the carbide layer 200 at different locations within the filament according to the present invention all has a structure similar to the shape where the first channel 211 and the second channel 212 intersect, forming a stacked block-like structure. The first channel 211 is distributed almost perpendicular to the filament edge and connects the second channel 212, the interior of the matrix 100, and the filament edge, which is advantageous for moving rare earth atoms outward and replenishing rare earth elements evaporated from the surface in a timely manner, thereby improving the release stability of the material. From the release performance stabilization time data in the test results, it became clear that there was a difference in the release performance of the filament. The filament of the present invention has stable release performance equivalent to that of conventional thorium-tungsten filaments. As can be seen from this, the tungsten carbide alloy material of the present invention replenishes the rare earth elements evaporated from the surface through the stable outward movement of the rare earth elements, improving the material's release stability. Even without the addition of thorium, it achieves stable release performance equivalent to that of conventional thorium-tungsten filaments, solving the problem of the inferior release stability of existing thorium-free tungsten filaments, and also avoiding the problem of radioactive contamination associated with conventional thorium-tungsten filaments.

[0301] 3. From the parameters of the number of cracks per 100m and yield in the test results, it was revealed that the filament material of the present invention has superior processing performance compared to existing thorium-tungsten, has a relatively low number of cracks (for a filament wire diameter of 500 μm, the number of flaw detection cracks in the filament can be less than 2 / 100m), a relatively high processing yield, the filaments wound with it are less prone to breakage, production efficiency is improved, and furthermore, the number of cracks in the wire is low, and the rate of breakage after carbonization of the manufactured filaments is also low.

[0302] 4. As is evident from the electron emission performance parameters in the test results, the DC emission capability of the heating device manufactured with the filament of the present invention is nearly twice as high as that of the thorium-tungsten filament (Comparative Example 1), and as a result, the heating device manufactured with the filament of the present invention can excite electrons at a lower voltage (Note: According to the usage of heating devices in this art, the starting voltage of the thorium-tungsten heating device must be at least 2.0V. In order to ensure starting, the operating voltage is set to 3.3V, whereas in Example 1, the starting voltage only needs to be 1.4V and the operating voltage only needs to be in the range of 1.6 to 1.8V).

[0303] While conventional thorium-tungsten filaments operate at temperatures of 1600-1900°C, the heating device of the present invention can operate at temperatures ranging from 1500-1600°C to 1100-1500°C, for example, 1200-1300°C. Therefore, both the energy consumption and lifespan of the heating device according to the present invention can be improved.

[0304] As described above, the above-mentioned technical solution according to the present invention includes at least the following operating principles or mechanisms and beneficial effects.

[0305] (1) The present invention dops tungsten matrix powder with oxides and carbides of M and controls the initial recrystallization temperature of the material, thereby enabling the production of extremely fine crystal grains even at the same carbonization temperature as thorium-tungsten. This improves the processing performance of the material, reduces the filament breakage rate during production and use, and lowers the electronic work function of the material. As a result, the filament breakage rate decreases and the yield improves, reducing production and transportation costs. Furthermore, the lifespan of the filament is effectively extended, achieving a lifespan equivalent to or far exceeding that of existing thorium-tungsten filaments.

[0306] (2) The initial recrystallization temperature of the filament material according to the present invention is 48%FC (approximately 2070°C) to 56%FC (approximately 2290°C). Therefore, after carbonization at a temperature of 2000 to 2100°C, the crystal grains of the tungsten matrix 100 become relatively fine, and the brittleness of the filament after carbonization is lower than that of conventional thorium-tungsten filament materials, which can reduce the rate of filament breakage during production and use for clients.

[0307] (3) Analysis of the effect of the average size of oxide particles: By keeping the average size of oxide particles in the tungsten alloy wire within the range limited in this application, it is advantageous to further improve the processing yield and flaw detection level of the wire. (4) The processing performance of the filament material of the present invention is superior to that of existing thorium-tungsten, with a relatively small number of flaw detection cracks (less than 2 flaw detection cracks / 100m for a filament wire diameter of 500μm), a relatively high processing yield, less breakage of the wound filament, improved production efficiency, fewer cracks in the wire, and a low rate of breakage during carbonization of the manufactured filament.

[0308] (5) In the filament material according to the present invention, the oxide of M (for example, lanthanum oxide particles) has good plasticity, and as the pressurization process progresses, the oxide particles of M become elongated and exist in a linear or near-linear shape. On the other hand, thorium oxide in conventional thorium-tungsten materials has relatively poor plasticity, so when processed to a certain extent, the thorium oxide breaks, and as processing progresses, the thorium oxide becomes particulate string-like. Due to the type of rare earth oxide added in the present invention and the change in morphological structure during the miniaturization process, the filament material has good processing performance. The filament material can be used to manufacture wire for winding filaments, with the wire diameter reduced to 500 μm or less, and it also effectively reduces the number of cracks detected by flaw detection, improving yield.

[0309] (6) The operating temperature of a heating device made with the tungsten alloy filament according to the present invention (i.e., the operating temperature of the filament) can be reduced from 1500°C to 1600°C to 1100°C to 1500°C, for example, 1200°C to 1300°C, while maintaining good operating conditions. In contrast, the operating temperature of a conventional thorium-tungsten filament is 1600°C to 1900°C. Therefore, both the energy consumption and lifespan of the filament and the heating device made therefrom according to the present invention are improved.

[0310] As described above, the filament according to the present invention, by adding one or more types of oxides and carbides or elemental carbon of M to the tungsten matrix 100, allows the combination of oxides and carbides or elemental carbon to accelerate the diffusion rate of the material within the matrix 100, and enables the achievement of equivalent or superior electron emission capacity at a lower operating voltage (excitation temperature) compared to thorium-tungsten filaments.

[0311] This invention allows for the production of extremely fine crystal grains even at the same carbonization temperature as thorium-tungsten by doping tungsten matrix powder with M oxides and carbides and controlling the initial recrystallization temperature of the material. This improves the processing performance of the material, reduces the filament breakage rate during production and use, and lowers the material's electronic work function. As a result, the filament breakage rate decreases, yield improves, production and transportation costs are reduced, and the lifespan of the filament is effectively extended, achieving a lifespan equivalent to or far exceeding that of existing thorium-tungsten filaments.

[0312] The filament according to the present invention can achieve an extremely high recrystallization temperature, and extremely fine crystal grains can be obtained even at the same carbonization temperature as thorium-tungsten. This material has excellent vibration resistance, which can reduce filament breakage and failure during production, transportation, and use.

[0313] In this specification, the symbol "~" is used to represent a numerical range, and this representation includes two endpoint values.

[0314] As described above, the specific parameters or commonly used reagents or raw materials in the above examples are specific or preferred examples based on the concept of the present invention, and are not limiting. Those skilled in the art can adapt and modify the invention within its concept and scope of protection. Unless otherwise specified, the raw materials used may be commercially available products in the art or prepared by conventional methods in the art.

[0315] Furthermore, while there are many problems in the prior art, those skilled in the art should understand that each embodiment or technical solution of the present invention does not need to simultaneously solve all of the technical problems described in the prior art or background art, and that improvements can be made in only one or more embodiments. Those skilled in the art should also understand that anything not described in the claims should not be considered a limitation on those claims.

[0316] This specification frequently uses terms such as initial recrystallization temperature and average oxide size, but this does not preclude the use of other terms. These terms are used solely to more conveniently describe and interpret the essence of the invention. To interpret them as any additional limitations would be contrary to the spirit of the invention. [Explanation of symbols]

[0317] 100 Matrix 200 Carbonized layer 210 channels 220 Filament outer edge 211 Channel 1 212 Channel 2

Claims

1. A method for manufacturing tungsten alloy wire, The tungsten alloy comprises 0.0005 to 0.3 wt% carbon, 0.25 to 2.6 wt% M, 0.05 to 0.5 wt% oxygen, the remainder being tungsten and unavoidable impurities, and its composition does not include thorium. The aforementioned M element is one or more elements selected from La, Y, Sc, Nd, Sm, Lu, Ce, Gd, Tb, Dy, Ho, Pr, Er, Tm, Yb, Eu, Hf, and Zr. The manufacturing process for the tungsten alloy wire includes the steps of doping and powdering, powder pressing, sintering, and pressurization in this order. In the aforementioned pressurized treatment step, the sintered tungsten alloy strip is processed to reduce its diameter to an intermediate standard wire of 1.5 to 3.5 mm, and then the intermediate standard wire is oxidized at (1200 to 1500) °C and an annealing rate of (3 to 10) m / min. After oxidized annealing, the intermediate standard wire is further processed to the desired wire diameter standard to obtain a tungsten alloy wire. A method for manufacturing a tungsten alloy wire, characterized in that the tungsten alloy wire has an initial recrystallization temperature of 48%Fc to 56%Fc, and / or an average grain size of (1 to 15) μm at 80%Fc recrystallization.

2. In the aforementioned sintering step, a tungsten alloy sintered strip is obtained by a high-temperature sintering method. The heating curve for the aforementioned high-temperature sintering is as follows: The temperature is raised from room temperature to A1 at a predetermined rate, and then maintained at A1 for a predetermined time. The temperature was increased from A1 to A2, the heating time being H3, and then maintained at H4 in A2. A1 was (950-1250)°C, H3 was (1.5-2.5)h, A2 was (1300-1500)°C, and H4 was (2.5-4.5). The temperature is raised from A2 to A3 at a predetermined rate, A3 is (1700-1900)°C, and the temperature is maintained at A3 for a predetermined time. The temperature is raised from A3 to A4 at a predetermined rate, A4 is (2050-2250)°C, and the temperature is maintained at A4 for a predetermined time. A method for producing tungsten alloy wire according to claim 1, characterized in that it is obtained by natural cooling from A4.

3. The heating curve for the aforementioned high-temperature sintering is as follows: The temperature was raised from room temperature to A1, the heating time H1 was (5-8) hours, and A1 was (950-1250)°C. In A1, the temperature is maintained for the duration of H2, and H2 is (1-3). The temperature was increased from A1 to A2, the heating time was H3, H3 was (1.5 to 2.5) hours, and A2 was (1300 to 1500) °C. The temperature was kept warm in A2 for H4 time, and H4 was (2.5 to 4.5). The temperature was increased from A2 to A3, the heating time was H5, H5 was (1-3) hours, and A3 was (1700-1900)°C. In A3, the temperature is maintained for H6 time, and H6 is (1-3). The temperature was increased from A3 to A4, the heating time was H7, H7 was (1-3) hours, and A4 was (2050-2250)°C. In A4, keep warm for H8 time, and H8 is (5-10). A method for producing tungsten alloy wire according to claim 2, characterized by obtaining it by natural cooling from A4.

4. A method for producing a tungsten alloy wire according to any one of claims 2 to 3, characterized in that the M element exists in the form of an oxide, and the average size of the oxide particles in the tungsten alloy wire is (100 to 500) nm.

5. A tungsten alloy wire comprising 0.0005 to 0.3 wt% carbon, 0.25 to 2.6 wt% M, 0.05 to 0.5 wt% oxygen, the remainder being tungsten and unavoidable impurities, and free from thorium. The aforementioned M element is one or more elements selected from La, Y, Sc, Nd, Sm, Lu, Ce, Gd, Tb, Dy, Ho, Pr, Er, Tm, Yb, Eu, Hf, and Zr. The tungsten alloy wire is characterized in that its initial recrystallization temperature is 48%Fc to 56%Fc, and / or its average grain size at 80%Fc recrystallization is (1 to 15) μm.

6. The tungsten alloy wire according to claim 5, characterized in that the M element exists in the form of an oxide, and the average size of the oxide particles in the tungsten alloy wire is (100 to 500) nm.

7. The aforementioned element M exists in the form of an oxide, and the aforementioned carbon element exists in the form of a carbide or elemental carbon. The oxide M is one or a combination of several selected from lanthanum oxide, yttrium oxide, scandium oxide, neodymium oxide, samarium oxide, lutetium oxide, cerium oxide, gadolinium oxide, terbium oxide, dysprosium oxide, holmium oxide, praseodymium oxide, erbium oxide, hafnium oxide, and zirconium oxide. The tungsten alloy wire according to any one of claims 5 to 6, characterized in that the carbide is one or more selected from lanthanum carbide, zirconium carbide, yttrium carbide, hafnium carbide, and tungsten carbide.

8. The wire diameter is 800 μm or less, and the number of cracks detected is less than 5 per 100 m. and / or, the component further comprises element T, wherein element T is a metallic element, T is at least one selected from K, Re, Mo, Fe, and Co, and the mass content of Re is less than 1000 ppm, characterized in that, the tungsten alloy wire according to claim 5.

9. The use of tungsten alloy wire, wherein the tungsten alloy filament is carbonized and then used as a cathode alloy wire for microwave heating devices. The use of tungsten alloy wire, characterized in that the tungsten alloy wire is manufactured using a tungsten alloy filament as described in any one of claims 5 to 8, or by a manufacturing method as described in any one of claims 1 to 4.

10. A tungsten carbide alloy filament, obtained by carbonizing a tungsten alloy wire. The tungsten alloy wire is characterized by being manufactured using a tungsten alloy filament according to any one of claims 5 to 8, or by a manufacturing method according to any one of claims 1 to 4, wherein the tungsten alloy wire is a tungsten alloy filament.

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