Tungsten carbide alloy filament, its manufacturing method, and heating device

Abstract

The present invention provides an aluminum carbide alloy filament and its manufacturing method, a heating device, and relates to the technical field of filament cathode materials. The aluminum carbide alloy filament includes a matrix (100) and a carbide layer (200) attached to the outer surface of the matrix (100). The carbide layer (200) has a grain width of 1.0 μm to 15.0 μm. The components of both the matrix (100) and the carbide layer (200) include tungsten, carbon, oxygen, and an M element, where the M element is one or a combination of elements selected from the group consisting of La, Y, Sc, Nd, Sm, Lu, Ce, Gd, Tb, Dy, Ho, Pr, Er, Tm, Yb, Eu, Hf, and Zr. The tungsten carbide alloy filament does not include thorium. This material improves the emission stability of tungsten alloy filaments and achieves the stable emission capability of conventional thorium-tungsten filaments without adding thorium, solving the problem of the relatively poor stable emission capability of existing thorium-free tungsten filaments and also eliminating the problem of radioactive contamination that occurs with conventional thorium-tungsten filaments.

Description

[Technical Field]

[0001] This application claims priority to a Chinese patent application bearing application number 2023113863234 and entitled "Tungsten carbide alloy filament and manufacturing method thereof, heating device" filed with the China Patent Office on October 25, 2023, the entire contents of which are incorporated herein by reference.

[0002] [Technical field] The present application relates to the technical field of filament cathode materials, in particular to a tungsten carbide alloy filament and its manufacturing method, and a heating device. [Background technology]

[0003] The filament cathode is an electron emitter and is widely used in microwave oven magnetrons. The performance of the filament cathode has a significant impact on the operating characteristics and lifespan of the magnetron, and it is considered the heart of the magnetron. Existing filament materials are mainly made of tungsten-thorium oxide or tungsten-rare earth oxide materials.

[0004] For example, Chinese invention patent application number CN201010299139, published April 3, 2013, discloses a method for doping powder for magnetron coils. The process involves doping, stirring, and steam drying. The method involves adding a neutralizing additive (ammonia water NH3·H2O solution) to a thorium nitrate solution, and then uniformly spraying and stirring the resulting mixture onto the surface of blue tungsten (WO2.9) particles placed in a doping pot. The doping pot is then evacuated and heated with water while stirring. The powder is then dried under vacuum by steam heating, ultimately resulting in a uniformly doped tungsten-thorium oxide powder with low impurity content.

[0005] The invention patent (application number CN201010299139) describes a magnetron coil material made of pure tungsten with thorium oxide added, which can achieve a continuous operating life of over 1,000 hours. However, cathode products made from this composite have a high brittle-ductile transition temperature, making them difficult to process and form, making the magnetron cathode susceptible to fracture during production and transportation. Furthermore, the relatively low recrystallization temperature causes abnormal recrystallization of the magnetron coil during carbonization, often resulting in fracture during use and transportation, leading to magnetron failure. Furthermore, thorium is a radioactive element, and its use as a primary additive will result in environmental pollution during the smelting, production, transportation, and use processes. The resulting final product may also pose adverse health risks to people who come into contact with it.

[0006] Chinese invention patent application number CN201410073749.9, published June 11, 2014, discloses a non-radioactive multi-component tungsten cathode material for microwave oven magnetrons and a manufacturing process thereof. The tungsten cathode material includes lanthanum oxide, zirconium oxide, yttrium oxide, lutetium oxide, rhenium, and tungsten, each rare earth oxide accounting for 0.5% to 1.5% by mass of the tungsten electrode material, the total amount of rare earth oxides accounting for 2% to 3% by mass of the tungsten electrode material, the alloying element rhenium accounting for 1% to 4% by mass of the tungsten electrode material, and the remainder being tungsten. The manufacturing method of the non-radioactive multi-component rare earth tungsten alloy electrode material for microwave oven magnetron includes solution preparation, drying, reduction, acid washing, cold isostatic pressing, sintering, vertical melting, medium frequency induction annealing, pressure processing, winding, and mechanical straightening.

[0007] In the patent for this invention (application number CN201410073749.9), some experts added multi-element rare earth oxides to the tungsten matrix to avoid the radiation of thorium. This material has a strong instantaneous emission ability but a weak stable emission ability, and its service life is far from the life standard of thorium-tungsten magnetron coils, usually only a few tens of hours. Furthermore, the use of metallic rhenium is expensive, which makes it unsuitable for industrial use.

[0008] As described above, conventional tungsten-thorium filaments are radioactive and pollute the environment, and the final products produced may also have adverse health effects on people who come into contact with them. Furthermore, existing filaments without added thorium have the problem of low stable emission capability. How to solve the above problems is a difficult challenge that those skilled in the art are trying to overcome. Summary of the Invention [Problem to be solved by the invention]

[0009] Conventional tungsten-thorium filaments are radioactive and pollute the environment, and the final products produced from them may have adverse effects on the health of people who come into contact with them. Furthermore, existing filaments without added thorium have the disadvantage of low stable emission capability. To solve these problems in the prior art, the present application provides a tungsten carbide alloy filament, and the specific technical solutions are as follows: [Means for solving the problem]

[0010] The tungsten carbide alloy filament comprises a matrix and a carbide layer attached to the outer surface of the matrix, the carbide layer having a grain width of 1.0 μm to 15.0 μm, the components of both the matrix and the carbide layer include tungsten, carbon, oxygen, and M, the M element being one or a combination of elements selected from La, Y, Sc, Nd, Sm, Lu, Ce, Gd, Tb, Dy, Ho, Pr, Er, Tm, Yb, Eu, Hf, and Zr, and the tungsten carbide alloy filament does not include thoriated titanium.

[0011] In some embodiments, the M element in the carbonized layer is present in the form of an oxide, the particle size of the M oxide particles is 10 nm to 1000 nm, and the carbon element is present in the form of a carbide.

[0012] In some embodiments, the carbonized layer has a number of second channels distributed therein, thereby forming a radially stacked layered structure in the cross section of the filament, and the carbonized layer has a number of first channels distributed therein, at least some of the first channels being aligned crosswise with the second channels, thereby dividing the stacked layered structure into a number of block-like structures.

[0013] In some embodiments, the carbonized layer includes a number of first channels distributed therein, at least some of which are radially distributed about the cross-section of the filament and / or at least some of which are centered about the cross-section of the filament, and the carbonized layer includes a number of second channels distributed therein, at least some of which are circumferentially distributed about the cross-section of the tungsten alloy filament, and at least some of which are aligned crosswise with the first channels.

[0014] In some embodiments, the components of the carbonized layer include W2C and WC, and the weight ratio of W2C to WC is (60-100):(0-40).

[0015] In some embodiments, in the matrix, the M element is present in the form of an oxide, and the carbon element is present in the form of a carbide or elemental carbon.

[0016] In some embodiments, the matrix contains, as components, 0.0005 to 0.3 wt% carbon, 0.25 to 2.6 wt% M, 0.05 to 0.5 wt% oxygen, and the balance being tungsten and unavoidable impurities.

[0017] In some embodiments, among the matrix components, the M element is present in the form of an oxide, and the carbon element is present in the form of a carbide or elemental carbon, the oxide of M being one or a combination of at least one 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 being one or a combination of at least one selected from lanthanum carbide, zirconium carbide, yttrium carbide, hafnium carbide, and tungsten carbide.

[0018] In some embodiments, the matrix components further include a metal element T, where T is at least one selected from K, Re, Mo, Fe, and Co.

[0019] In some embodiments, the mass content of Re is less than 1000 ppm.

[0020] In some embodiments, the tungsten carbide alloy filament has a diameter of 800 μm or less.

[0021] In some embodiments, the operating temperature is between 1100°C and 1500°C.

[0022] In some embodiments, the tungsten carbide alloy filament is a helical structure having a pitch of 0.800-1.800 mm, a length of 10.00-16.00 mm, and an outer diameter of 3.00-6.00 mm.

[0023] In some embodiments, the tungsten carbide alloy filament is a helical structure with the thickness of the carbide layer of at least one helical coil reaching 30 μm to 90 μm.

[0024] The present application provides a method for producing the tungsten carbide alloy filament, Doping and powder production: Step S1 of producing a finished powder raw material product in the order of a doping process, which is solid-liquid doping or solid-solid doping, a reduction process, and a powder production process; Powder pressing: Step S2: Using an isostatic press, the powder raw material is pressed into a green compact under pressure, and the green compact is pre-sintered at a low temperature in a hydrogen atmosphere to obtain a pre-sintered billet; High-temperature sintering: Step S3 of sintering the pre-sintered billet at a high temperature by a high-temperature sintering method to obtain a sintered billet; Pressure processing: a step of reducing the diameter of the sintered billet to form a tungsten alloy wire of a certain diameter, in which an oxidation annealing treatment is performed during the reduction step S4; Cleaning: Step S5 of cleaning the tungsten alloy wire to make it into a tungsten alloy white wire; Winding: Step S6 winding the tungsten alloy white wire into a spring-like filament structure; Assembling the cathode: Step S7: Assembling the spring-like filament structure together with components such as assemblies, ceramics, and tabs into a cathode structure by heat treatment; Welding: Step S8 of welding the filament structure in the cathode structure to the cap of the assembly; Carbonization: Step S9 of carbonizing the welded cathode structure.

[0025] The present application further provides a heating device including the tungsten carbide alloy filament described above.

[0026] In some embodiments, the temperature rise curve of the high-temperature sintering step is as follows: temperature rise from room temperature to A1, temperature rise time H1 is (5-8) hours, A1 is (950-1250) °C, A1 is kept at H2 hours, H2 is (1-3), A1 rises from A1 to A2, temperature rise time H3 is (1.5-2.5) hours, A2 is (1300-1500) °C, A2 is kept at H4 hours, H4 is (2.5-4.5), A2 rises from A2 to A3, The temperature rise time is H5, H5 is (1 to 3) hours, A3 is (1700 to 1900) °C, the temperature is maintained at A3 for H6 hours, H6 is (1 to 3), the temperature is raised from A3 to A4, the temperature rise time is H7, H7 is (1 to 3) hours, A4 is (2050 to 2250) °C, the temperature is maintained at A4 for H8 hours, H8 is (5 to 10), natural cooling is performed from A4 to obtain a sintered billet.

[0027] In some embodiments, the process of the pressure processing step is to reduce the sintered billet to an intermediate wire rod with a diameter of 1.5-3.5mm, and then oxidize the intermediate wire rod at (1200-1500)℃ and an annealing speed of (3-10)m / min to obtain a tungsten alloy wire. [Effects of the Invention]

[0028] Based on the above, compared with the prior art, the present application has the following advantages:

[0029] In the tungsten carbide alloy material of the present application, through the design of the carbide layer and the composition of rare earth element components, the rare earth atoms can migrate stably outward, replenishing the rare earth element evaporated from the surface, thereby improving the emission stability of the material.Without adding thorium element, the stable emission ability of the conventional thorium-tungsten filament can be achieved, solving the problem that the stable emission ability of the existing thorium-free tungsten filament is relatively poor, and also avoiding the problem of radioactive contamination that occurs in the conventional thorium-tungsten filament.

[0030] Other features and advantageous advantages of the present application will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by the practice of the present application. The objectives and other advantageous advantages of the present application will be realized and obtained through the structure particularly pointed out in the written description, claims, and drawings. [Brief explanation of the drawings]

[0031] In order to more clearly describe the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings necessary for describing the embodiments or the prior art. It is clear that the drawings in the following description are some embodiments of the present application, and those skilled in the art can derive other drawings based on these drawings without any creative efforts.

[0032] [Figure 1] 1 is a schematic diagram of a partial structure of a tungsten alloy filament according to the present application. [Figure 2] 1 is a cross-sectional structural schematic diagram of a tungsten alloy filament according to the present application. [Figure 3] 1 is a schematic diagram of the longitudinal cross-section of a tungsten alloy filament according to the present invention. [Figure 4] FIG. 3 is an enlarged view of part A in FIG. 2. [Figure 5] FIG. 1 is a metallographic structure diagram of Comparative Example 1 according to the present invention at 44% FC. [Figure 6] FIG. 1 is a metallographic structure diagram of Comparative Example 1 according to the present invention at 46% FC. [Figure 7] FIG. 1 is a metal structure diagram of Comparative Example 1 according to the present application at 48% FC. [Figure 8] FIG. 1 is a metal structure diagram of Comparative Example 1 according to the present application at 50% FC. [Figure 9] FIG. 1 is a metallographic structure diagram of Example 1 of the present invention at 48% FC. [Figure 10] FIG. 1 is a metallographic structure diagram of Example 1 according to the present application at 50% FC. [Figure 11] FIG. 1 is a metallographic structure diagram of Example 1 of the present invention at 52% FC. [Figure 12]FIG. 2 is a structural schematic diagram of the crystal structure of Comparative Example 1 according to the present application. [Figure 13] FIG. 1 is a structural schematic diagram of a crystal structure of Example 1 according to the present application. [Figure 14] FIG. 1 is a diagram showing a channel distribution in a cross section of Example 1 according to the present application. [Figure 15] FIG. 2 is a diagram showing a channel distribution in a vertical cross section of Example 1 according to the present application. [Figure 16] FIG. 1 is a diagram showing the channel distribution in the cross section of Comparative Example 1 according to the present application. [Figure 17] FIG. 10 is a diagram showing the channel distribution in the cross section of Comparative Example 4 according to the present application. [Figure 18] FIG. 10 is a diagram showing the channel distribution in a vertical cross section of Comparative Example 4 according to the present application. [Figure 19] 1 is a schematic diagram of the overall structure of a tungsten alloy filament according to the present application. [Figure 20] 1 is a schematic diagram of a process flow for manufacturing a heating device using tungsten alloy wire according to the present application. [Figure 21] FIG. 1 is a diagram showing the conversion relationship between FC% and ° C. [Figure 22] 1 is a partial cross-sectional structural schematic diagram of a tungsten alloy filament according to the present application. DETAILED DESCRIPTION OF THE INVENTION

[0033] In order to clarify the objectives, technical solutions and advantages of the embodiments of the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, but not all of the embodiments. The technical features designed in different embodiments of the present application described below may be combined with each other as long as they are not contradictory. All other embodiments obtained by those skilled in the art based on the embodiments of the present application without any creative effort fall within the scope of protection of the present application.

[0034] In describing this application, all terms (including technical and scientific terms) used in this application have the same meaning as commonly understood by those skilled in the art and should not be understood to limit this application. Furthermore, it should be understood that the terms used in this application should be understood to have a meaning consistent with the meaning of these terms in the context of this specification and the related art, and should not be understood in an idealized or overly formal sense unless explicitly defined as such in this application.

[0035] The present application provides a tungsten carbide alloy material, the technical solutions of which are as follows:

[0036] The tungsten carbide alloy material comprises a matrix and a carbide layer attached to the outer surface of the matrix, the carbide layer having a grain width of 1.0 μm to 15.0 μm, the components of both the matrix and the carbide layer include tungsten, carbon, oxygen, and M, the M element being one or a combination of elements selected from La, Y, Sc, Nd, Sm, Lu, Ce, Gd, Tb, Dy, Ho, Pr, Er, Tm, Yb, Eu, Hf, and Zr, and the tungsten carbide alloy filament does not include thoriated tungsten.

[0037] 1. Preferred structural and phase composition characteristics of the carbonized layer 200 described above

[0038] (1) The element M in the carbonized layer exists in the form of an oxide, the element carbon exists in the form of a carbide, and the particle diameter of the oxide particles of M is 10 nm to 1000 nm.

[0039] (2) As shown in Figures 1 to 4, a number of first channels 211 are distributed in the carbonized layer 200, and at least some of the first channels 211 are distributed in the radial direction of the cross-section of the filament, and / or at least some of the first channels 211 point toward the center of the cross-section of the filament.

[0040] (3) As shown in Figures 4 and 22, a number of channels 210 are distributed in the carbonized layer 200, the channels 210 including first channels 211 and a number of second channels 212, at least some of the first channels 211 are distributed in the radial direction of the cross section of the tungsten alloy filament, and / or at least some of the first channels 211 point to the center of the cross section of the tungsten carbide alloy filament, at least some of the second channels 212 are distributed in the circumferential direction of the cross section of the tungsten alloy filament, and at least some of the second channels 212 are arranged crosswise with the first channels 211, so that the cross section of the carbonized layer 200 is in the form of a stacked lattice.

[0041] Specifically, in the present invention, the structure of the carbonized layer 200 is controlled so that the crystal grain size is controlled within a predetermined small range (crystal grain width: 1.0 μm to 15.0 μm), thereby forming many first channels 211 and second channels 212, forming a laminated block structure. In combination with the rare earth component in the tungsten alloy filament, this provides a stable emission effect. The specific mechanism is as follows.

[0042] 22 , the second channels 212 divide the carbonized layer 200 into radially stacked layer structures, and the first channels 211 designed to intersect the second channels 212 divide the carbonized layer 200 into block structures, resulting in a layered lattice structure. Compared to other structural distributions, such as a structure in which the first channels 211 divide the carbonized layer 200 into block structures and the second channels 212 divide the carbonized layer 200 into radially stacked layer structures, the second channels 212 and the first channels 211 do not intersect, resulting in the carbonized layer 200 being clearly divided into two regions, one of which has a block structure and the other a layered structure. In the present application, controlling the crystal grains of the carbonized layer 200 so that its cross section has a layered lattice-like design has the following advantages. The radial or approximately vertical distribution design of the first channels 211 is beneficial to the outward migration of M element rare earth atoms, and the layered structure of the carbonized layer 200 separated by the second channels 212 has M oxides distributed therein. By combining the second channels 212 and the first channels 211 (vertical channels 210), the carbonized layer 200 has a layered lattice structure, which can effectively control the migration speed of M oxides to the surface of the filament (i.e., the outer surface of the carbonized layer 200), thereby improving the stable release ability of the tungsten carbide alloy.

[0043] As shown in the filament structure in Fig. 1, the cross section of the filament in Fig. 2, and the longitudinal section of the filament in Fig. 3, the terms "distributed in the radial direction of the cross section of the filament" and "at least some of the first channels 211 point to the center of the cross section of the filament" in this specification refer to a radial distribution pattern and a center-pointing pattern in which an end point of the first channel 211 close to the matrix 100 is connected to an end point close to the edge of the filament to form a first straight line, and the angle between the first straight line and a tangent line at the intersection of the outer edge 220 of the filament is (60 to 90) degrees.

[0044] As shown in Figure 22, the term "distributed in the circumferential direction of the cross section of the tungsten alloy filament" in this specification refers to the fact that the end points of both ends of the second channel 212 are connected to form a second straight line, and the angle between the second straight line and the straight line on which the radial direction of the filament is located is (-45 to +45) degrees.

[0045] In the present application, the first channels 211 and the filament outer edges 220 (i.e., the outer edges of the carbonized layer 200) are distributed in a substantially vertical and substantially radial direction. A design in which the first channels 211 are distributed in a radial or substantially vertical direction is beneficial to the outward movement of the M element atoms, but this does not mean that the first channels 211 have a linear structure, nor does it mean that the two end points of the first channels 211 need to penetrate to the outer edges of the matrix 100 and the carbonized layer 200 (i.e., the filament outer edges 220).

[0046] In the present application, the second channels 212 are distributed along the circumferential direction or arranged crosswise with the first channels 211, but this does not mean that the second channels 212 have a standard arc structure, nor that the second channels 212 are continuously connected and penetrate the entire outer ring. The second channels 212 may be distributed in a generally annular manner, consisting of multiple sections of the second channels 212 separated from each other, or may be distributed crosswise with the first channels 211, so that the carbonized layer 200 is divided into a layered structure stacked in the radial direction.

[0047] (3) The tungsten carbide alloy filament has a helical structure, in which the thickness of the carbonized layer of at least one helical coil reaches 30 μm to 90 μm, preferably 35 to 45 μm, 50 to 90 μm, for example, 60 μm, 70 μm, or 80 μm.

[0048] (4) The components of the carbonized layer 200 include W2C and WC, and the weight ratio of W2C to WC is (60-100):(0-40).

[0049] 2. Preferred component characteristics of tungsten carbide alloy materials

[0050] (1) In the matrix, the M element exists in the form of an oxide, and the carbon element exists in the form of a carbide or elemental carbon.

[0051] In the present invention, one or more oxides of M and carbides or elemental carbon are added. The oxides of M in the tungsten matrix react with carbides at high temperatures. For example, lanthanum oxide reacts with tungsten carbide to generate lanthanum atoms. The size of the generated lanthanum atoms is much smaller than the size of lanthanum oxide particles, so the migration and diffusion rate of the lanthanum atoms in the tungsten matrix is ​​very fast, thereby accelerating the diffusion rate of the M metal atoms. As can be seen from the above, in the present invention, by combining an oxide of M with carbides or elemental carbon, it is possible to achieve electron emission capabilities equal to or greater than those of thorium-tungsten filaments at a lower operating voltage (excitation temperature) than that of thorium-tungsten filaments. This makes it easier to ensure a balance between the loss of rare earth atoms in the carbide layer of the filament and their replenishment by migration, thereby ensuring the electron emission stability of the filament.

[0052] (2) The matrix of the tungsten carbide alloy filament contains, as its components, 0.0005-0.3 wt% carbon, 0.25-2.6 wt% M, 0.05-0.5 wt% oxygen, and the balance being tungsten and unavoidable impurities. Preferably, the matrix of the tungsten carbide alloy filament contains, as its components, 0.0005-0.3 wt% carbon, 0.25-2.6 wt% M, 0.05-0.5 wt% oxygen, and the balance being tungsten and unavoidable impurities.

[0053] Wherein, the M element may be 1.28-2.6wt%, and the tungsten alloy filament made of the tungsten alloy material with this composition ratio is relatively effective when used in a microwave oven of less than 800W. The M element may be 0.25-1.28wt%, and the tungsten alloy filament made of the tungsten alloy material with this composition ratio is relatively effective when used in a microwave oven of more than 800W. Furthermore, the M element may be 0.25-0.86wt%, and the tungsten alloy filament made of the tungsten alloy material with this composition ratio is relatively effective when used in a microwave oven of more than 1000W.

[0054] Preferably, M is present in the tungsten alloy material in the form of an oxide, and the oxide of M is one or more selected from the group consisting of 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. 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 the group consisting of lanthanum carbide, zirconium carbide, yttrium carbide, hafnium carbide, and tungsten carbide. For example, the oxide of M may be selected from lanthanum oxide, a combination of lanthanum oxide and yttrium oxide, a combination of lanthanum oxide and zirconium oxide, a combination of lanthanum oxide and scandium oxide, or a combination of lanthanum oxide and hafnium oxide.

[0055] Preferably, the matrix components of tungstenalloy material further comprise T, T is a solid solution metal element or dispersed metal element, and T is at least one selected from K, Re, Mo, Fe, Co. More preferably, the mass content of Re is less than 1000ppm.

[0056] In this specification, "La, Y, Sc, Nd, Sm, Lu, Ce, Gd, Tb, Dy, Ho, Pr, Er, Tm, Yb, Eu, Hf, and Zr" are element symbols in the periodic table, and respectively represent the metallic elements lanthanum, yttrium, scandium, neodymium, samarium, lutetium, cerium, gadolinium, terbium, dysprosium, holmium, praseodymium, erbium, thulium, ytterbium, europium, hafnium, and zirconium in the periodic table. In this specification, "K, Re, Mo, Fe, and Co" are element symbols in the periodic table, and respectively represent the metallic elements potassium, rhenium, molybdenum, iron, and cobalt in the periodic table. W is the element symbol for tungsten in the periodic table. C is the symbol for carbon in the periodic table. In addition, "M" and "T" are merely reference symbols and do not represent elements in the periodic table; they are used only for reference.

[0057] 3. The diameter of the tungsten carbide alloy filament can reach 800μm or less.

[0058] The tungsten alloy material of the present application has good processability in pressure processing, can be processed into the wire rod of fine diameter specification (i.e., the tungsten alloy wire of fine diameter), and can control the tolerance of wire diameter within a very small range.

[0059] Furthermore, the wire diameter can reach 600 μm or less, 550 μm or less, or even 500 μm or less. The wire diameter may be 450 to 550 μm, for example, 470 μm, 490 μm, 500 μm, 520 μm, or the like, or 700 to 800 μm, for example, 750 μm, 760 μm, 780 μm, or the like.

[0060] 4. The tungsten carbide alloy filament has a helical structure in actual use. The preferred structural features of the helical structure of the tungsten alloy filament are as follows:

[0061] 4.1 Turn control: As shown in the structural diagram of the tungsten alloy filament in Figure 19, the turn number of the alloy filament is preferably (9.5-13), the tolerance is controlled to ±0.125, and the statistical CPK is greater than 1.33.

[0062] The number of turns of the alloy filament is 9.50 to 13.00 turns, and a preferred number of turns is 9.70 to 10.70 turns, for example, 9.90 turns, 10.00 turns, 10.28 turns, 10.5 turns, etc., or 10.70 to 11.70 turns, for example, 11.00 turns, 11.20 turns, 11.5 turns, etc., or 11.80 to 13.00 turns, for example, 12.00 turns, 12.20 turns, 12.5 turns, etc.

[0063] 4.2 Pitch uniformity: The pitch L1 of the tungsten carbide alloy filament has a tolerance of ±0.02, and the statistical CPK is greater than 1.33. Here, the pitch L1 of the tungsten carbide alloy filament is shown in Figure 19, i.e., the distance between two adjacent spiral coils. In practice, those skilled in the art can use a dedicated winding device to make the filament pitch uniform, so that the heating device can emit electrons more stably.

[0064] The number of turns of the filament is related to the length L of the filament and the pitch L1, and the filament length L = (number of turns of the filament - 1) * L1.

[0065] 4.3 Pitch size: The pitch L1 of the tungsten carbide alloy filaments is 0.800 to 1.800 mm, and the preferred pitch L1 may be 1.000 to 1.150 mm, such as 1.018 mm, 1.044 mm, 1.135 mm, etc., or 1.230 mm to 1.330 mm, such as 1.240 mm, 1.290 mm, etc., or 1.400 mm to 1.600 mm, such as 1.470 mm, 1.500 mm, etc.

[0066] 3.4 Length: The length L of the alloy filament is 10.00 to 16.00 mm, and a preferred length L may be 10.50 to 12.00 mm, such as 11.00 mm, 11.20 mm, 11.70 mm, or 12.50 to 14.00 mm, such as 12.83 mm, 13.40 mm, 13.55 mm.

[0067] The outer diameter Φ1 of the alloy filament is 3.00 to 6.00 mm, and a preferable outer diameter Φ1 may be 3.50 to 4.50 mm, for example, 3.70 mm, 3.80 mm, 3.90 mm, 3.92 mm, 4.00 mm, etc., or 5.00 to 6.00 mm, for example, 5.20 mm, 5.48 mm, 5.60 mm, etc.

[0068] The present application further provides the following preferred embodiments for manufacturing a tungsten alloy wire (finished product before carbonization, Steps 1-6), a tungsten alloy carbide filament (Steps 1-9), and a heating device including a tungsten alloy filament (Steps 1-12).

[0069] It includes the following steps:

[0070] Step 1: The powder raw material is manufactured in the order of a doping process (solid-liquid doping or solid-solid doping), a reduction process, and a powder manufacturing process.

[0071] Step 2: Powder Compaction: Using isostatic pressing, powders of various particle sizes are compressed into a compact, which is then pre-sintered at low temperature in a hydrogen atmosphere to improve its strength. Here, the powder is compressed at a pressure of 160-240 MPa into compacts weighing 1.5-5.0 kg each.

[0072] Step 3: High-temperature sintering: High-temperature sintering produces a density of 17.5-18.3g / cm 3 The tungsten alloy material in the form of a billet is obtained as a sintered billet.

[0073] The temperature rise curve for the high-temperature sintering is as follows:

[0074] The temperature is raised from room temperature to A1, the temperature raising time H1 is (5 to 8) hours, and A1 is (950 to 1250) ° C., For example, H1 is (5 to 7) hours, (7 to 8) hours, etc., and another example is 6 hours, 7.5 hours, etc., and A1 is (950 to 1050)°C, (1050 to 1250)°C, etc., and another example is 1000°C, 1100°C, etc. Incubate in A1 for H2 hours, where H2 is (1-3), For example, H2 is (1-2)h, (2-3)h, etc., and other examples are 1.5h, 2.5h, etc. The temperature is increased from A1 to A2, and the temperature increase time is H3, H3 is (1.5 to 2.5) hours, and A2 is (1300 to 1500) ° C., For example, H3 is (1.5 to 2.0) hours, (2.0 to 2.5) hours, etc., and other examples are 1.5 hours, 2.0 hours, 2.4 hours, etc., and A2 is (1300 to 1400°C) degrees Celsius, (1400 to 1500°C), etc., and other examples are 1350°C, 150°C, etc. Incubate in A2 for H4 hours, H4 is (2.5-4.5), For example, H4 is (2.5-3.0)h, (3.0-4.0)h, etc., and other examples are 2.8h, 3.5h, etc. The temperature is increased from A2 to A3, and the temperature increase time is H5, H5 is (1 to 3) hours, and A3 is (1700 to 1900) ° C., For example, H5 is (1 to 2) hours, (2 to 3) hours, etc., and other examples are 1.6 hours, 2.0 hours, 2.5 hours, etc.; A3 is (1700 to 1800) degrees Celsius, (1800 to 1900) degrees Celsius, etc., and other examples are 1750 degrees Celsius, 1850 degrees Celsius, etc.; Incubate in A3 for H6 hours, H6 is (1-3), For example, H6 is (1-2)h, (2-3)h, etc., and other examples are 1.5h, 2.5h, etc. The temperature is increased from A3 to A4, and the temperature increase time is H7, H7 is (1 to 3) hours, and A4 is (2050 to 2250) ° C., For example, H7 is (1-2)h, (2-3)h, etc., and other examples are 1.5h, 2.5h, etc.; A4 is (2050-2150)°C, (2150-2250)°C, etc., and other examples are 2100°C, 2200°C, etc.; Incubate in A4 for H8 hours, H8 is (5-10), For example, H8 is (5-7)h, (7-10)h, etc., and other examples are 6h, 8h, etc. A4 is naturally cooled to obtain a sintered billet.

[0075] Step 4: Pressure processing: 4.1 In the pressure processing step, the tungsten alloy sintered billet produced by sintering is thinned to be processed into an intermediate wire rod having a diameter of 1.5 to 3.5 mm.

[0076] 4.2 Next, the intermediate gauge wire is subjected to oxidation annealing at (1200-1500)°C and an annealing speed of (3-10) m / min.

[0077] For example, the annealing rate is (3 to 7) m / min, (7 to 10) m / min, etc., and other examples are 3 m / min, 5 m / min, 7 m / min, etc., and the oxidation annealing temperature is (1200 to 1350) °C, (1350 to 1500) °C, etc., and other examples are 1250 °C, 1400 °C, etc.

[0078] 4.3 After oxidation annealing, the intermediate wire is processed to a desired diameter to obtain a tungsten alloy wire.

[0079] Here, the diameter reduction process is performed by multiple rotary swaging and drawing, the oxidation annealing process is performed in an oxidation annealing device, and the annealing rate represents the speed at which the wire material passes through the annealing tank, i.e., the length of the wire material passing through the annealing tank per unit time.

[0080] Step 5: Cleaning to white wire: The black wire is cleaned by electrolytic cleaning to be processed into tungsten alloy white wire for the filament of microwave oven heating devices.

[0081] Step 6: Winding: Wind the white wire into a spring-like filament structure for the heating device to obtain a tungsten alloy wire.

[0082] Step 7: Assembling the cathode: The spring-like filament structure is assembled into a cathode structure together with other components such as assemblies, ceramics, and tabs through heat treatment.

[0083] Step 8: Welding: The filament structure of the cathode structure is welded to the cap of the assembly.

[0084] Step 9: Carbonization: The welded cathode structure is carbonized to obtain a tungsten carbide alloy filament.

[0085] Step 10: Assembling the white sphere: Assemble the cathode structure, anode cylinder, antenna cap, and other components into a single unit.

[0086] Step 11: The white ball is evacuated and vacuumed, and then subjected to high-temperature burn-in to realize the production of the black ball and activation of its emission performance.

[0087] Step 12: Assemble the black sphere, heat sink, magnet, tube shell, etc., and finally obtain the heating device member containing the tungsten carbide alloy filament, which is then installed in a microwave oven for use.

[0088] 1. The preferred structural characteristics of the produced tungsten alloy wire before carbonization (i.e., the wire material obtained by pressure processing) itself are as follows:

[0089] 1.1 Characteristics of recrystallization start temperature

[0090] The recrystallization start temperature of the tungsten alloy wire according to the present invention is 48% Fc to 56% Fc, which is higher than the recrystallization start temperature of the thorium-containing tungsten wire, but the recrystallization start temperature of the thorium-tungsten is about 46% Fc (2020°C).

[0091] The average size of the recrystallized grains at 80% Fc of the tungsten alloy wire according to the present application is smaller than that of the thorium-containing tungsten wire. The average size of the recrystallized grains at 80% Fc of the tungsten alloy wire according to the present application is (1 to 15) μm, and the average size of the recrystallized grains at 80% Fc of the thorium-tungsten filament is (16 to 150) μm.

[0092] Due to the above characteristics of a high recrystallization start temperature and a small average size of recrystallized crystal grains at 80% Fc, the tungsten matrix structure of the filament produced by the tungsten alloy wire of the present application is finer than the tungsten matrix structure of the thorium-tungsten filament after magnetron carbonization, thereby making the grain width of the carbonized layer of the tungsten alloy filament after carbonization finer and controlling the grain width of the carbonized layer within a desired range.

[0093] The process of converting tungsten alloy wire into tungsten carbide involves a carbonization step at a temperature of 2000-2500°C. Original thorium-tungsten filaments carbonize at this temperature (analysis has shown that the reason is that the recrystallization onset temperature is too low). The grain structure exhibits recrystallization, resulting in coarse grains. As a result, the carbonized filament is highly brittle and has poor vibration resistance. Wire breakage is highly likely during magnetron assembly, production, and transportation, as well as subsequent use in microwave ovens. Compared to thorium-tungsten filaments, the recrystallization onset temperature of the filament material selected herein is higher than that of the original thorium-tungsten wire, and the average size of the recrystallized grains at 80% Fc is smaller than that of the original thorium-tungsten wire. The tungsten alloy wire of the present invention maintains a fine-grained filament structure after carbonization, making it less brittle than conventional thorium-tungsten filament materials. The fine-grained tungsten alloy filaments are more vibration resistant than thorium-tungsten filaments, and the filament breakage rate of magnetrons produced according to the present invention is much lower than that of magnetrons produced with conventional thorium-tungsten.

[0094] Optionally, the recrystallization start temperature of the tungsten alloy wire may be 48-52%FC, for example, 48%FC, 50%FC, 52%FC, etc.

[0095] Optionally, the average size of the recrystallized grains at 80% Fc of the tungsten alloy wire may be (1-8) μm, (8-12) μm, (12-15) μm, etc., as another example, 4.0 μm, 8.5 μm, 13 μm, etc.

[0096] 1.2 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.

[0097] The average oxide particle size of the tungsten alloy wire according to the present invention is (100-500) nm. The size of the oxide particles of the tungsten alloy wire determines the size of the oxide particles of the carbonized filament. If the oxide particles of the wire material are too coarse compared to the limited range of the present invention, the particles of the carbonized tungsten alloy filament will be relatively coarse, making it more difficult for the oxide particles of M to migrate to the surface of the filament during use in the magnetron. This will easily disrupt the balance between the loss and replenishment of rare earth elements on the surface of the filament, thereby causing instability in the electron emission of the magnetron.

[0098] Optionally, the average size of the oxide particles may also be (100-300) nm, (300-500) nm, etc., as another example, 200 nm, 300 nm, 450 nm, etc.

[0099] 1.3 Characteristics of the number of cracks detected by the above tungsten alloy wires

[0100] The number of flaws detected by the above-mentioned tungsten alloy wire is 5 (pieces / 100 meters) or less. Furthermore, the number of flaws detected by the tungsten alloy wire may be less than 2 pieces / 100 meters, such as 0 pieces / 100 meters, 0.5 pieces / 100 meters, or 1 piece / 100 meters.

[0101] Tungsten alloy wire has fewer cracks to detect, a higher filament yield, and is less likely to break.

[0102] 2. Key control points of the preferred embodiment of the method for producing the tungsten alloy wire before carbonization

[0103] In the present application, through the preferred embodiment of the above-mentioned manufacturing method, can obtain the above-mentioned tungsten alloy wire before carbonization, which has the above-mentioned recrystallization start temperature and the average size of oxide particles.By carbonizing this tungsten alloy wire, can obtain the tungsten carbide alloy filament, which has the above-mentioned characteristics of the grain width of the carbonized layer, the oxide particle size of the carbonized layer, etc.The specific control points of the manufacturing method for obtaining this tungsten alloy wire before carbonization are as follows:

[0104] (1) Oxidation annealing treatment for intermediate standard products This application provides a specific processing method for performing oxidation annealing in the above pressure processing step, thereby controlling the recrystallization start temperature of the tungsten alloy within the desired range (48% Fc to 56% Fc). By performing stress relief oxidation annealing at a temperature of 1200 to 1500°C at a location of 1.5 to 3.5 mm intermediate gauge of the wire material, the recrystallization start temperature of the tungsten alloy wire is effectively controlled to 48% Fc to 56% Fc. If the oxidation annealing process is omitted in this manufacturing process, the recrystallization start temperature of the tungsten alloy wire will exceed 56% Fc. An excessively high recrystallization start temperature will adversely affect the electron emission performance of the tungsten carbide alloy filament under the operating conditions of the magnetron.

[0105] (2) In the sintering process, by controlling the temperature rise time from A1 to A2 and the sintering time at A2 (1300-1500°C), In the high-temperature sintering stage of the tungsten blank, the present application provides a sintering process in which the temperature rise time from A1 to A2 and the sintering time at A2 (1300-1500°C) are controlled so that the sintering neck of the tungsten blank grows rapidly and blocks the pores, preventing oxide particles in the pores from being pushed into other pores through unblocked communicating channels during the contraction of the sintering cavity of the billet, thereby ensuring the density of the sintered billet and controlling the size of oxide particles in the sintered billet, thereby controlling the size of oxide particles in the tungsten alloy wire material or filament after carbonization.

[0106] The tungsten alloy sintered billet manufactured by the above sintering process has an oxide particle size distribution range of 100-2000nm and an average oxide particle size of 600-1000nm, and the tungsten alloy wire has an average oxide particle size of (100-500)nm, optionally, the average oxide particle size can be (100-300)nm, (300-500)nm, etc., as another example, 200nm, 300nm, 450nm, etc.

[0107] Without the above sintering process, the oxide particle size distribution range of the tungsten alloy sintered billet is 400-5000nm, and the average size of the oxide particles is 1200-2000nm. Furthermore, the average size of the oxide particles in the refined tungsten alloy wire is also relatively coarse (about 500-900nm).

[0108] The mechanism of the sintering process that affects the oxide size of the billet, tungsten alloy wire, and carbonized filament, and the impact of the oxide size of the tungsten alloy wire and carbonized filament on the performance of the filament, are as follows: The reason for controlling the oxide particle size within a narrow range is that the oxide particle size of the billet directly determines the oxide size of the tungsten alloy wire or carbonized filament. The coarser the oxide particles of the wire, the more difficult it is for the particles to migrate to the surface of the filament during use in the magnetron. This can easily lead to an imbalance between the loss and replenishment of rare earth elements on the filament surface, resulting in unstable electron emission from the magnetron.

[0109] Adjusting the sintering process can affect the growth rate of the sintered neck and the closure rate of the voids in the tungsten blank. The sintering process can reduce the possibility of oxide particle agglomeration and even reduce the size of oxide particles in the sintered billet. The specific principle of the high-temperature sintering process is explained as follows:

[0110] The compact produced by isostatic pressing is a densely packed powder with a porosity of approximately 35-45%. These voids can be thought of as holes connected by multiple channels, with oxide particles evenly distributed on the inner surfaces of the holes. During the high-temperature sintering process, the tungsten particles that are stuck together form "sinter necks." As the sintering temperature increases, the sinter necks continue to grow, blocking the channels that connect the holes, resulting in the creation of isolated holes. These isolated holes gradually become rounder, reducing the surface area within the holes, causing small oxide particles that were originally the same size to aggregate and form larger oxide particles. As high-temperature sintering progresses, the holes further shrink due to diffusion, and the oxide particles distributed on the inner surfaces of the holes further aggregate, only to form one or more larger oxide particles.

[0111] Some of the smaller holes may merge with larger adjacent holes through diffusion, or may shrink before the connecting channels close. Oxide particles in these smaller holes may be pushed out into adjacent open holes, causing the open holes to contain more oxide than elsewhere, resulting in coarser oxide particles.

[0112] The present application also provides the following examples and comparative examples.

[0113] The weight ratios of the raw material components and the elemental ratios of the produced filament materials in the examples and comparative examples of the present application are shown in Table 1 below.

[0114] [Table 1] TIFF2026505917000003.tif108164

[0115] Specifically, according to the formulations in Table 1, the raw material components in the examples and comparative examples are used to manufacture tungsten alloy filaments and heating devices by the following manufacturing method.

[0116] Example 1 1. According to the formula in Table 1, add 5 L of deionized water to the specified amount of lanthanum nitrate solution and stir for 10 minutes to fully dissolve it. Then add 1 L of ammonia water (NH3·H2O) and stir to neutralize. The resulting mixture was sprayed evenly onto the blue tungsten in the doping pot and stirred. The volume ratio of the lanthanum nitrate solution to the ammonia water (NH3·H2O) solution was 5:1. 2. The doping pot was evacuated and stirred with water while heating (heating temperature 80°C, vacuum degree -0.025MPa). 3. In a vacuum state, the powder was dried using a steam heating method, the steam pressure was set to 0.1-0.3 MPa, and the vacuum degree in the pot was set to -0.02 MPa or less. Finally, a tungsten-lanthanum doped powder with uniform doping and low impurity content was obtained. 4. The tungsten-lanthanum doped powder was reduced once in a reduction furnace with four temperature zones of 650°C, 750°C, 850°C, and 900°C to produce tungsten-lanthanum powder with appropriate particle size. 5. The obtained tungsten-lanthanum powder and tungsten carbide were placed in a high-speed powder mixer and mixed for 2 hours, then sieved to obtain a mixed tungsten-lanthanum alloy powder. 6. Using the isostatic press method, powder with a particle size of 1.5 μm was pressed into a green compact weighing 3.0 kg at a pressure of 180 MPa, and the green compact was then pre-sintered at low temperature in a hydrogen atmosphere to improve its strength. 7. High temperature sintering method, adopting high speed temperature rise and extended temperature keeping time at intermediate temperature keeping point. The sintering temperature curve is as follows: The temperature is raised from room temperature to A1, the temperature rise time H1 is 6 hours, and A1 is 1100°C. Incubate at A1 for H2 hours, H2 is 2, The temperature is increased from A1 to A2, and the temperature increase time is H3, H3 is 2 hours, and A2 is 1400°C, Incubate in A2 for H4 hours, H4 is 3.5, The temperature is increased from A2 to A3, and the temperature increase time is H5, H5 is 2 hours, and A3 is 1800 ° C. Incubate in A3 for H6 hours, H6 is 2, The temperature is increased from A3 to A4, and the temperature increase time is H7, H7 is 2 hours, and A4 is 2100 ° C. Incubate in A4 for H8 hours, H8 is 6, A4 was naturally cooled to obtain a sintered billet. Here, by controlling the medium frequency sintering time, the speed of closing and shrinking the voids in the billet can be controlled, resulting in oxide particle diameters of less than 2.0 μm and densities of 18.0 g / cm. 3 A sintered billet of 10 ... 8. The sintered billet with a diameter of 17 mm was processed into a wire rod with a standard of 2.0 mm by multiple rotary swaging and drawing processes, and then oxidized and annealed in an oxidized annealing device at a temperature of 1400°C and an annealing speed of 5 m / min. After annealing was completed, the billet was further processed into a rare earth tungsten alloy black wire with a diameter of 0.52 mm ± 0.005 mm. Here, the multiple rotary swaging and drawing processes were performed using a conventional drawing process. The process parameters were: multiple rotary swaging to make the wire diameter 3.7 mm, then drawing to 2.0 mm, and after annealing, continuing to process into a tungsten-lanthanum alloy black wire of 0.52±0.005 mm. 9. 0.52 mm black wire was electrolytically cleaned to 0.50 mm ± 0.005 mm tungsten-lanthanum alloy white wire, which can be processed into filaments for microwave heating devices. 10. 0.50 mm tungsten-lanthanum alloy white wire was wound with 10 turns at a pitch of 1.29 ± 0.03 mm to form a spring-shaped cathode filament for the heating device. 11. The filament was assembled into a cathode structure together with other components such as assemblies, ceramics, and tabs by heat treatment at 600°C. 12. The filament in the cathode structure was welded integrally to the cap of the assembly. 13. The cathode structure was placed in a carbonization tank and carbonized. After evacuation, a carbon-containing hydrocarbon gas (specifically, methane) was introduced, and a constant direct current (current value: 16 A) was applied to the cathode to heat it, and the filament was carbonized in the hydrocarbon gas. 14. Assembly of the white sphere: The cathode structure, anode cylinder, antenna cap, and other components were assembled into a single unit. 15. The white bulb was evacuated and vacuumed, and then subjected to high-temperature burn-in to activate the black bulb and its emission performance. 16. The black sphere, heat sink, magnet, tube shell, etc. were assembled to finally obtain a heating device member including the filament, which was then installed in a microwave oven for use.

[0117] Example 2 1. According to the formula in Table 1, add 5 L of deionized water to the specified amount of lanthanum nitrate-yttrium nitrate solution and stir for 10 minutes to fully dissolve it. Then, add 1 L of ammonia water (NH3·H2O) and stir to neutralize. The resulting mixed solution was sprayed evenly onto the blue tungsten placed in the doping pot and stirred. The volume ratio of the lanthanum nitrate-yttrium nitrate solution to the ammonia water (NH3·H2O) solution was 5:1. 2. The doping pot was evacuated and stirred with water while heating (heating temperature 80°C, vacuum degree -0.025MPa). 3. In a vacuum state, the powder was dried using a steam heating method, the steam pressure was set to 0.1-0.3 MPa, and the vacuum degree in the pot was set to -0.02 MPa or less. Finally, a tungsten-lanthanum-yttrium doped powder with uniform doping and low impurity content was obtained. 4. The tungsten-lanthanum yttrium doped powder was reduced once in a reduction furnace with four temperature zones of 650°C, 750°C, 850°C, and 900°C to produce tungsten-lanthanum yttrium powder with appropriate particle size. 5. The obtained tungsten-lanthanum yttrium powder and tungsten carbide were placed in a high-speed powder mixer and mixed for 2 hours, then sieved to obtain a mixed tungsten-lanthanum yttrium alloy powder. 6. Using the isostatic press method, powder with a particle size of 1.5 μm was pressed into a green compact weighing 3.0 kg at a pressure of 180 MPa, and the green compact was then pre-sintered at low temperature in a hydrogen atmosphere to improve its strength. 7. High temperature sintering method, adopting high speed temperature rise and extended temperature keeping time at intermediate temperature keeping point. The sintering temperature curve is as follows: The temperature is raised from room temperature to A1, the temperature rise time H1 is 5 hours, and A1 is 950°C. Incubate at A1 for H2 hours, H2 is 3, The temperature is increased from A1 to A2, and the temperature increase time is H3, H3 is 1.5 h, and A2 is 1300 ° C. Incubate in A2 for H4 hours, H4 is 4.5, The temperature is increased from A2 to A3, and the temperature increase time is H5, H5 is 1 hour, and A3 is 1700 ° C. Incubate in A3 for H6 hours, H6 is 3, The temperature is increased from A3 to A4, and the temperature increase time is H7, H7 is 1 hour, and A4 is 2050 ° C. Incubate in A4 for H8 hours, H8 is 10, A4 was naturally cooled to obtain a sintered billet. 8. The 17 mm diameter sintered billet was processed into a 2.0 mm standard wire by multiple rotary swaging and drawing processes, and then oxidized and annealed in an oxidized annealing apparatus at a temperature of 1200°C and an annealing speed of 3 m / min. After annealing was completed, the billet was processed into a 0.52 mm ± 0.005 mm diameter tungsten-lanthanum-yttrium alloy black wire. The remaining conditions were the same as in Example 1. 9. 0.52 mm black wire was electrolytically cleaned to 0.50 mm ± 0.005 mm tungsten-lanthanum-yttrium alloy white wire, which can be processed into filaments for microwave heating devices. 10. 0.50 mm tungsten-lanthanum yttrium alloy white wire was wound with 10 turns at a pitch of 1.29 ± 0.03 mm to form a spring-shaped cathode filament for the heating device. 11. The filament was assembled into a cathode structure by heat treatment at 600°C with components such as assemblies, ceramics, and tabs. 12. The filament in the cathode structure was welded integrally to the cap of the assembly. 13. The cathode structure was placed in a carbonization tank and carbonized. After evacuation, a carbon-containing hydrocarbon gas (specifically, methane) was introduced, and a constant direct current (current value: 16 A) was applied to the cathode to heat it, and the filament was carbonized in the hydrocarbon gas. 14. Assembly of the white sphere: The cathode structure, anode cylinder, antenna cap, and other components were assembled into a single unit. 15. The white bulb was evacuated and vacuumed, and then subjected to high-temperature burn-in to activate the black bulb and its emission performance. 16. The black sphere, heat sink, magnet, tube shell, etc. were assembled to finally obtain a heating device member including the filament, which was then installed in a microwave oven for use.

[0118] Example 3 1. According to the formula in Table 1, add 5 L of deionized water to the specified amount of lanthanum nitrate-zirconium nitrate solution and stir for 10 minutes to fully dissolve. Then, add 1 L of aqueous ammonia (NH3·H2O) solution and stir to neutralize. The resulting mixture was sprayed evenly onto the blue tungsten in the doping pot and stirred. The ratio of the lanthanum nitrate-zirconium nitrate solution to the aqueous ammonia (NH3·H2O) solution was 5:1. 2. The doping pot was evacuated and stirred with water while heating (heating temperature 80°C, vacuum degree -0.025MPa). 3. In a vacuum state, the powder was dried using a steam heating method, the steam pressure was set to 0.1-0.3 MPa, and the vacuum degree in the pot was set to -0.02 MPa or less. Finally, a tungsten-lanthanum zirconium doped powder with uniform doping and low impurity content was obtained. 4. The tungsten-lanthanum zirconium doped powder was reduced once in a reduction furnace with four temperature zones of 650°C, 750°C, 850°C and 900°C to produce tungsten-lanthanum zirconium powder with appropriate particle size. 5. The obtained tungsten-lanthanum zirconium powder and tungsten carbide were placed in a high-speed powder mixer and mixed for 2 hours, then sieved to obtain a mixed tungsten-lanthanum zirconium alloy powder. 6. Using the isostatic press method, powder with a particle size of 1.5 μm was pressed into a green compact weighing 3.0 kg at a pressure of 180 MPa, and the green compact was then pre-sintered at low temperature in a hydrogen atmosphere to improve its strength. 7. High temperature sintering method, adopting high speed temperature rise and extended temperature keeping time at intermediate temperature keeping point. The sintering temperature curve is as follows: The temperature is raised from room temperature to A1, the temperature rise time H1 is 8 hours, and A1 is 1250°C. Incubate at A1 for H2 hours, H2 is 1, The temperature is increased from A1 to A2, and the temperature increase time is H3, H3 is 2.5 h, and A2 is 1500 ° C. Incubate in A2 for H4 hours, H4 is 2.5, The temperature is increased from A2 to A3, and the temperature increase time is H5, H5 is 3 hours, and A3 is 1900 ° C. Incubate in A3 for H6 hours, H6 is 1, The temperature is increased from A3 to A4, and the temperature increase time is H7, H7 is 3 hours, and A4 is 2250 ° C. Incubate for H8 hours in A4, and H8 is 5. A4 was naturally cooled to obtain a sintered billet. 8. The sintered billet with a diameter of 17 mm was processed into a wire rod with a standard of 2.0 mm by multiple rotary swaging and drawing processes, and then oxidative annealing was performed in an oxidative annealing device under the annealing conditions of a temperature of 1500°C and an annealing speed of 10 m / min. After the annealing was completed, the billet was further processed into a tungsten-lanthanum zirconium alloy black wire with a diameter of 0.52 mm ± 0.005 mm. 9. The 0.52 mm black wire was electrolytically cleaned to produce a 0.50 mm±0.005 mm tungsten-lanthanum zirconium alloy white wire suitable for processing into filaments for microwave oven heating devices. The remaining conditions were the same as in Example 1. 10. 0.50 mm tungsten-lanthanum zirconium alloy white wire was wound with 10 turns at a pitch of 1.29 ± 0.03 mm to form a spring-shaped cathode filament for the heating device. 11. The filament was assembled into a cathode structure together with other components such as assemblies, ceramics, and tabs by heat treatment at 600°C. 12. The filament in the cathode structure was welded integrally to the cap of the assembly. 13. The cathode structure was placed in a carbonization tank and carbonized. After evacuation, a carbon-containing hydrocarbon gas (specifically, methane) was introduced, and a constant direct current (current value: 16 A) was applied to the cathode to heat it, and the filament was carbonized in the hydrocarbon gas. 14. Assembly of the white sphere: The cathode structure, anode cylinder, antenna cap, and other components were assembled into a single unit. 15. The white bulb was evacuated and vacuumed, and then subjected to high-temperature burn-in to activate the black bulb and its emission performance. 16. The black sphere, heat sink, magnet, tube shell, etc. were assembled to finally obtain a heating device member including the filament, which was then installed in a microwave oven for use.

[0119] Example 4 1. According to the formula in Table 1, add 5 L of deionized water to the specified amount of lanthanum nitrate-scandium nitrate solution and stir for 10 minutes to fully dissolve. Then, add 1 L of aqueous ammonia (NH3·H2O) solution and stir to neutralize. The resulting mixture was sprayed evenly onto the blue tungsten in the doping pot and stirred. The ratio of the lanthanum nitrate-scandium nitrate solution to the aqueous ammonia (NH3·H2O) solution was 5:1. 2. The doping pot was evacuated and stirred with water while heating (heating temperature 80°C, vacuum degree -0.025MPa). 3. In a vacuum state, the powder was dried using a steam heating method, the steam pressure was set to 0.1-0.3 MPa, and the vacuum degree in the pot was set to -0.02 MPa or less. Finally, a uniformly doped tungsten-lanthanum-scandium doped powder with a low impurity content was obtained. 4. The tungsten-lanthanum scandium doped powder was reduced once in a reduction furnace with four temperature zones of 650°C, 750°C, 850°C and 900°C to produce tungsten-lanthanum scandium powder with appropriate particle size. 5. The obtained tungsten-lanthanum scandium powder and tungsten carbide were placed in a high-speed powder mixer and mixed for 2 hours, then sieved to obtain a mixed tungsten-lanthanum scandium alloy powder. 6. Using the isostatic press method, powder with a particle size of 1.5 μm was pressed into a green compact weighing 3.0 kg at a pressure of 180 MPa, and the green compact was then pre-sintered at low temperature in a hydrogen atmosphere to improve its strength. 7. High-temperature sintering method, oxide particle size less than 2.0 μm, density 18.0 g / cm 3 A sintered billet of 10 ... 8. The sintered billet 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 by multiple rotary swaging and drawing processes, where the process and conditions of this step were consistent with those of Example 1. 9. 0.52 mm black wire was electrolytically cleaned to produce 0.50 mm ± 0.005 mm tungsten-lanthanum-scandium alloy white wire, which can be processed into filaments for microwave heating devices. 10. 0.50 mm tungsten-lanthanum-scandium alloy white wire was wound with 10 turns at a pitch of 1.29 ± 0.03 mm to form a spring-shaped cathode filament for the heating device. 11. The filament was assembled into a cathode structure together with other components such as assemblies, ceramics, and tabs by heat treatment at 600°C. 12. The filament in the cathode structure was welded integrally to the cap of the assembly. 13. The cathode structure was placed in a carbonization tank and carbonized. After evacuation, a carbon-containing hydrocarbon gas (specifically, methane) was introduced, and a constant direct current (current value: 16 A) was applied to the cathode to heat it, and the filament was carbonized in the hydrocarbon gas. 14. Assembly of the white sphere: The cathode structure, anode cylinder, antenna cap, and other components were assembled into a single unit. 15. The white bulb was evacuated and vacuumed, and then subjected to high-temperature burn-in to activate the black bulb and its emission performance. 16. The black sphere, heat sink, magnet, tube shell, etc. were assembled to finally obtain a heating device member including the filament, which was then installed in a microwave oven for use.

[0120] Example 5 1. According to the formula in Table 1, add 5 L of deionized water to the specified amount of lanthanum nitrate-hafnium nitrate solution and stir for 10 minutes to fully dissolve. Then, add 1 L of aqueous ammonia (NH3·H2O) solution and stir to neutralize. The resulting mixture was sprayed evenly onto the blue tungsten in the doping pot and stirred. The ratio of the lanthanum nitrate-hafnium nitrate solution to the aqueous ammonia (NH3·H2O) solution was 5:1. 2. The doping pot was evacuated and stirred with water while heating (heating temperature 80°C, vacuum degree -0.025MPa). 3. In a vacuum state, the powder was dried using a steam heating method, the steam pressure was set to 0.1-0.3 MPa, and the vacuum degree in the pot was set to -0.02 MPa or less. Finally, a tungsten-lanthanum hafnium doped powder with uniform doping and low impurity content was obtained. 4. The tungsten-lanthanum hafnium doped powder was reduced once in a reduction furnace with four temperature zones of 650°C, 750°C, 850°C, and 900°C to produce tungsten-lanthanum hafnium powder with an appropriate particle size and a content of 0.3% La2O3 + 0.2% HfO2. 5. The obtained tungsten-lanthanum hafnium powder and tungsten carbide were placed in a high-speed powder mixer and mixed for 2 hours. After sieving, a mixed tungsten-lanthanum hafnium alloy powder containing 0.3% La2O3, 0.2% HfO2, and 0.5% WC was obtained. 6. Using the isostatic press method, powder with a particle size of 1.5 μm was pressed into a green compact weighing 3.0 kg at a pressure of 180 MPa, and the green compact was then pre-sintered at low temperature in a hydrogen atmosphere to improve its strength. 7. High-temperature sintering method, oxide particle size less than 2.0 μm, density 18.0 g / cm 3 A sintered billet of 10 ... 8. The sintered billet 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 by multiple rotary swaging and drawing processes, where the process and conditions of the steps were consistent with those of Example 1. 9. 0.52 mm black wire was electrolytically cleaned to 0.50 mm ± 0.005 mm tungsten-lanthanum-hafnium alloy white wire, which can be processed into filaments for microwave heating devices. 10. 0.50 mm tungsten-lanthanum hafnium alloy white wire was wound with 10 turns at a pitch of 1.29 ± 0.03 mm to form a spring-shaped cathode filament for the heating device. 11. The filament was assembled into a cathode structure together with other components such as assemblies, ceramics, and tabs by heat treatment at 600°C. 12. The filament in the cathode structure was welded integrally to the cap of the assembly. 13. The cathode structure was placed in a carbonization tank and carbonized. After evacuation, a carbon-containing hydrocarbon gas (specifically, methane) was introduced, and a constant direct current (current value: 16 A) was applied to the cathode to heat it, and the filament was carbonized in the hydrocarbon gas. 14. Assembly of the white sphere: The cathode structure, anode cylinder, antenna cap, and other components were assembled into a single unit. 15. The white bulb was evacuated and vacuumed, and then subjected to high-temperature burn-in to activate the black bulb and its emission performance. 16. The black sphere, heat sink, magnet, tube shell, etc. were assembled to finally obtain a heating device member including the filament, which was then installed in a microwave oven for use.

[0121] Example 6 1. According to the formula in Table 1, add 5 L of deionized water to the specified amount of lanthanum nitrate-hafnium nitrate solution and stir for 10 minutes to fully dissolve. Then, add 1 L of aqueous ammonia (NH3·H2O) solution and stir to neutralize. The resulting mixture was sprayed evenly onto the blue tungsten in the doping pot and stirred. The ratio of the lanthanum nitrate-hafnium nitrate solution to the aqueous ammonia (NH3·H2O) solution was 5:1. 2. The doping pot was evacuated and stirred with water while heating (heating temperature 80°C, vacuum degree -0.025MPa). 3. In a vacuum state, the powder was dried using a steam heating method, the steam pressure was set to 0.1-0.3 MPa, and the vacuum degree in the pot was set to -0.02 MPa or less. Finally, a tungsten-lanthanum hafnium doped powder with uniform doping and low impurity content was obtained. 4. The tungsten-lanthanum hafnium doped powder was reduced once in a reduction furnace with four temperature zones of 650℃, 750℃, 850℃ and 900℃ to tungsten-lanthanum hafnium powder with appropriate particle size and a content of 2.0%La2O3+1.0%HfO2. 5. The obtained tungsten-lanthanum hafnium powder and tungsten carbide were placed in a high-speed powder mixer and mixed for 2 hours. After sieving, a mixed tungsten-lanthanum hafnium alloy powder containing 2.0% La2O3 + 1.0% HfO2 + 2.0% WC was obtained. 6. Using the isostatic press method, powder with a particle size of 1.5 μm was pressed into a green compact weighing 3.0 kg at a pressure of 180 MPa, and the green compact was then pre-sintered at low temperature in a hydrogen atmosphere to improve its strength. 7. High-temperature sintering method, oxide particle size less than 2.0 μm, density 18.0 g / cm 3 A sintered billet of 10 ... 8. The sintered billet 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 by multiple rotary swaging and drawing processes, where the process and conditions of the steps were consistent with those of Example 1. 9. 0.52 mm black wire was electrolytically cleaned to 0.50 mm ± 0.005 mm tungsten-lanthanum-hafnium alloy white wire, which can be processed into filaments for microwave heating devices. 10. 0.50 mm tungsten-lanthanum hafnium alloy white wire was wound with 10 turns at a pitch of 1.29 ± 0.03 mm to form a spring-shaped cathode filament for the heating device. 11. The filament was assembled into a cathode structure together with other components such as assemblies, ceramics, and tabs by heat treatment at 600°C. 12. The filament in the cathode structure was welded integrally to the cap of the assembly. 13. The cathode structure was placed in a carbonization tank and carbonized. After evacuating, a carbon-containing hydrocarbon gas (specifically, methane gas) was introduced, and a constant direct current (current value: 16 A) was applied to the cathode to heat it, and the filament was carbonized in the hydrocarbon gas. 14. Assembly of the white sphere: The cathode structure, anode cylinder, antenna cap, and other components were assembled into a single unit. 15. The white bulb was evacuated and vacuumed, and then subjected to high-temperature burn-in to activate the black bulb and its emission performance. 16. The black sphere, heat sink, magnet, tube shell, etc. were assembled to finally obtain a heating device member including the filament, which was then installed in a microwave oven for use.

[0122] Example 7 1. According to the formula in Table 1, add the specified amount of lanthanum nitrate to 5 L of deionized water and stir for 10 minutes to fully dissolve it. Then, add 1 L of aqueous ammonia (NH3·H2O) solution and stir to neutralize. The resulting mixture was sprayed evenly onto the blue tungsten in the doping pot and stirred. The volume ratio of the lanthanum nitrate solution to the aqueous ammonia (NH3·H2O) solution was 5:1. 2. The doping pot was evacuated and stirred with water while heating (heating temperature 80°C, vacuum degree -0.025MPa). 3. In a vacuum state, the powder was dried using a steam heating method, the steam pressure was set to 0.1-0.3 MPa, and the vacuum degree in the pot was set to -0.02 MPa or less. Finally, a tungsten-lanthanum doped powder with uniform doping and low impurity content was obtained. 4. The tungsten-lanthanum doped powder was reduced once in a reduction furnace with four temperature zones of 650°C, 750°C, 850°C, and 900°C to produce tungsten-lanthanum powder with appropriate particle size. 5. According to the formulation in Table 1, 5 L of deionized water was added to a doping pot and heated to 80°C. A predetermined amount of ammonium rhenate was then added and stirred for 10 minutes to fully dissolve. A predetermined amount of tungsten-lanthanum powder was then added to the ammonium rhenate solution and stirred for 30 minutes. The powder was then dried using a steam heating method under vacuum, with the steam pressure set to 0.1-0.3 MPa and the vacuum level in the pot set to -0.02 MPa or less. Finally, a uniformly doped rhenium-doped tungsten-lanthanum powder with low impurity content was obtained. 6. The rhenium-doped tungsten-lanthanum powder was reduced once in a reduction furnace with four temperature zones 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. 7. The obtained tungsten-lanthanum rhenium alloy powder and tungsten carbide were placed in a high-speed powder mixer and mixed for 2 hours, then sieved to obtain a mixed tungsten-lanthanum rhenium alloy powder. 8. Using the isostatic pressing method, powder with a particle size of 1.5 μm was pressed into a green compact weighing 3.0 kg at a pressure of 180 MPa, and the green compact was then pre-sintered at low temperature in a hydrogen atmosphere to improve its strength. 9. High-temperature sintering method, oxide particle size less than 2.0 μm, density 18.0 g / cm 3 A sintered billet of 10 ... 10. The sintered billet 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 by multiple rotary swaging and drawing processes, where the process and conditions of the steps were consistent with those of Example 1. 11. 0.52 mm black wire was electrolytically cleaned to 0.50 mm ± 0.005 mm tungsten-lanthanum-rhenium alloy white wire, which can be processed into filaments for microwave heating devices. 12. A spring-shaped cathode filament for the heating device was prepared by winding 10 turns of 0.50 mm tungsten-lanthanum-rhenium alloy white wire with a pitch of 1.29 ± 0.03 mm. 13. The filament was assembled into a cathode structure together with other components such as assemblies, ceramics, and tabs by heat treatment at 600°C. 14. The filament in the cathode structure was welded integrally to the cap of the assembly. 15. The cathode structure was placed in a carbonization tank and carbonized. After evacuation, a carbon-containing hydrocarbon gas (specifically, methane) was introduced, and a constant direct current (current value: 16 A) was applied to the cathode to heat it, and the filament was carbonized in the hydrocarbon gas. 16. Assembly of the white sphere: The cathode structure, anode cylinder, antenna cap, and other components were assembled into a single unit. 17. The white bulb was evacuated and vacuumed, and then subjected to high-temperature burn-in to activate the black bulb and its emission performance. 18. The black sphere, heat sink, magnet, tube shell, etc. were assembled to finally obtain a heating device member including the filament, which was then installed in a microwave oven for use.

[0123] Comparative Example 1 1. According to the formula in Table 1, add 5 L of deionized water to the specified amount of tritium nitrate solution and stir for 10 minutes to fully dissolve it. Then add 1 L of aqueous ammonia (NH3·H2O) and stir to neutralize. The resulting mixed solution was sprayed evenly onto the blue tungsten placed in the doping pot and stirred. The ratio of tritium nitrate solution to aqueous ammonia (NH3·H2O) was 5:1. 2. The doping pot was evacuated and stirred with water while heating (heating temperature 80°C, vacuum degree -0.025MPa). 3. In a vacuum state, the powder was dried using a steam heating method, the steam pressure was set to 0.1-0.3 MPa, and the vacuum degree in the pot was set to -0.02 MPa or less, and finally, a thoriated tungsten-doped powder with uniform doping and low impurity content was obtained. 4. The thoriated tungsten-doped powder was reduced once in a reduction furnace with four temperature zones of 650°C, 750°C, 850°C, and 900°C to thoriated tungsten powder with a particle size of 1.5 μm. 5. The obtained thoriated tungsten powder was placed in a V-type powder mixer and mixed for 2 hours, then sieved to obtain a mixed thoriated tungsten powder. 6. Using the isostatic press method, thoriated tungsten powder with a particle size of 1.5 μm was pressed into a green compact weighing 3.0 kg at a pressure of 180 MPa, and the green compact was then pre-sintered at low temperature in a hydrogen atmosphere to improve its strength. 7. High-temperature sintering method, the particle size of thoriated titanium oxide particles is less than 2.0 μm, and the density is 18.0 g / cm 3 A sintered billet of 10 ... 8. The sintered billet with a diameter of 17 mm was processed into a thoriated tungsten alloy black wire with a diameter of 0.52 mm±0.005 mm by multiple rotary swaging and drawing processes, where the process and conditions of this step were consistent with those of Example 1. 9. 0.52 mm black wire was electrolytically cleaned to produce 0.50 mm ± 0.005 mm thoriated tungsten alloy white wire, which can be processed into filaments for microwave heating devices. 10. Ten turns of 0.50 mm thoriated tungsten white wire were wound with a pitch of 1.29 ± 0.03 mm to form a spring-shaped cathode filament for the heating device. 11. The filament was assembled into a cathode structure together with other components such as assemblies, ceramics, and tabs by heat treatment at 600°C. 12. The filament in the cathode structure was welded integrally to the cap of the assembly. 13. The cathode structure was placed in a carbonization tank and carbonized. After evacuation, carbon-containing hydrocarbon gas (methane gas) was introduced, and a constant direct current (current value 16 A) was applied to the cathode to heat it, and the filament was carbonized in the hydrocarbon gas. 14. Assembly of the white sphere: The cathode structure, anode cylinder, antenna cap, and other components were assembled into a single unit. 15. The white bulb was evacuated and vacuumed, and then subjected to high-temperature burn-in to activate the black bulb and its emission performance. 16. The black sphere, heat sink, magnet, tube shell, etc. were assembled to finally obtain a heating device member including the filament, which was then installed in a microwave oven for use.

[0124] Comparative Example 2 1. According to the formula in Table 1, add 5 L of deionized water to the specified amount of lanthanum nitrate-yttrium nitrate solution and stir for 10 minutes to fully dissolve. Then, add 1 L of ammonia water (NH3·H2O) and stir to neutralize. The resulting mixed solution was sprayed evenly onto the blue tungsten in the doping pot and stirred. The ratio of the lanthanum nitrate-yttrium nitrate solution to the ammonia water (NH3·H2O) solution was 5:1. 2. The doping pot was evacuated and stirred with water while heating (heating temperature 80°C, vacuum degree -0.025MPa). 3. In a vacuum state, the powder was dried using a steam heating method, the steam pressure was set to 0.1-0.3 MPa, and the vacuum degree in the pot was set to -0.02 MPa or less. Finally, a tungsten-lanthanum-yttrium doped powder with uniform doping and low impurity content was obtained. 4. The tungsten-lanthanum yttrium doped powder was reduced once in a reduction furnace with four temperature zones of 650°C, 750°C, 850°C, and 900°C to produce tungsten-lanthanum yttrium powder with a particle size of 1.5 μm. 5. The obtained tungsten-lanthanum yttrium powder was placed in a V-type powder mixer and mixed for 2 hours, and then sieved to obtain a mixed tungsten-lanthanum yttrium alloy powder. 6. Using the isostatic pressing method, tungsten-lanthanum-yttrium alloy powder with a particle size of 1.5 μm was pressed into a green compact weighing 3.0 kg at a pressure of 180 MPa, and the green compact was then pre-sintered at low temperature in a hydrogen atmosphere to improve its strength. 7. High-temperature sintering method, oxide particle size less than 2.0 μm, density 18.0 g / cm 3 A sintered billet of 10 ... 8. The sintered billet 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 by multiple rotary swaging and drawing processes, where the process and conditions of the steps were consistent with those of Example 1. 9. 0.52 mm black wire was electrolytically cleaned to 0.50 mm ± 0.005 mm tungsten-lanthanum-yttrium alloy white wire, which can be processed into filaments for microwave heating devices. 10. 0.50 mm tungsten-lanthanum yttrium alloy white wire was wound with 10 turns at a pitch of 1.29 ± 0.03 mm to form a spring-shaped cathode filament for the heating device. 11. The filament was assembled into a cathode structure together with other components such as assemblies, ceramics, and tabs by heat treatment at 600°C. 12. The filament in the cathode structure was welded integrally to the cap of the assembly. 13. The cathode structure was placed in a carbonization tank and carbonized. After evacuation, a carbon-containing hydrocarbon gas (specifically, methane) was introduced, and a constant direct current (current value: 16 A) was applied to the cathode to heat it, and the filament was carbonized in the hydrocarbon gas. 14. Assembly of the white sphere: The cathode structure, anode cylinder, antenna cap, and other components were assembled into a single unit. 15. The white bulb was evacuated and vacuumed, and then subjected to high-temperature burn-in to activate the black bulb and its emission performance. 16. The black sphere, heat sink, magnet, tube shell, etc. were assembled to finally obtain a heating device member including the filament, which was then installed in a microwave oven for use.

[0125] Comparative Example 3 1. According to the formula in Table 1, add 5 L of deionized water to the specified amount of lanthanum nitrate-scandium nitrate solution and stir for 10 minutes to fully dissolve. Then, add 1 L of aqueous ammonia (NH3·H2O) solution and stir to neutralize. The resulting mixture was sprayed evenly onto the blue tungsten in the doping pot and stirred. The ratio of the lanthanum nitrate-scandium nitrate solution to the aqueous ammonia (NH3·H2O) solution was 5:1. 2. The doping pot was evacuated and stirred with water while heating (heating temperature 80°C, vacuum degree -0.025MPa). 3. In a vacuum state, the powder was dried using a steam heating method, the steam pressure was set to 0.1-0.3 MPa, and the vacuum degree in the pot was set to -0.02 MPa or less. Finally, a uniformly doped tungsten-lanthanum-scandium doped powder with a low impurity content was obtained. 4. The tungsten-lanthanum scandium doped powder was reduced once in a reduction furnace with four temperature zones of 650°C, 750°C, 850°C, and 900°C to produce tungsten-lanthanum scandium powder with a particle size of 1.5 μm. 5. The obtained tungsten-lanthanum scandium powder was placed in a V-type powder mixer and mixed for 2 hours, and then sieved to obtain a mixed tungsten-lanthanum scandium alloy powder. 6. Using the isostatic press method, powder with a particle size of 1.5 μm was pressed into a green compact weighing 3.0 kg at a pressure of 180 MPa, and the green compact was then pre-sintered at low temperature in a hydrogen atmosphere to improve its strength. 7. High-temperature sintering method, oxide particle size less than 2.0 μm, density 18.0 g / cm 3 A sintered billet of 10 ... 8. The sintered billet 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 by multiple rotary swaging and drawing processes, where the process and conditions of this step were consistent with those of Example 1. 9. 0.52 mm black wire was electrolytically cleaned to produce 0.50 mm ± 0.005 mm tungsten-lanthanum-scandium alloy white wire, which can be processed into filaments for microwave heating devices. 10. 0.50 mm tungsten-lanthanum-scandium alloy white wire was wound with 10 turns at a pitch of 1.29 ± 0.03 mm to form a spring-shaped cathode filament for the heating device. 11. The filament was assembled into a cathode structure together with other components such as assemblies, ceramics, and tabs by heat treatment at 600°C. 12. The filament in the cathode structure was welded integrally to the cap of the assembly. 13. The cathode structure was placed in a carbonization tank and carbonized. After evacuation, a carbon-containing hydrocarbon gas (specifically, methane gas is preferred) was introduced, and a direct current of a certain current value (preferably 16 A) was applied to the cathode to heat it, and the filament was carbonized in the hydrocarbon gas. 14. Assembly of the white sphere: The cathode structure, anode cylinder, antenna cap, and other components were assembled into a single unit. 15. The white bulb was evacuated and vacuumed, and then subjected to high-temperature burn-in to activate the black bulb and its emission performance. 16. The black sphere, heat sink, magnet, tube shell, etc. were assembled to finally obtain a heating device member (i.e., a heating device) containing the filament, which was then installed in a microwave oven for use.

[0126] Comparative Example 4 Using the cathode filament of Example 1, the carbonization current in the carbonization process of Example 1 was increased by 2 A, the crystal grains of the carbonized structure were enlarged, and the crystal grain width was increased from 3 to 10 μm in Example 1 to 10 to 30 μm. One way to adjust the grain size is to adjust the carbonization current. By adjusting the magnitude of the carbonization current, the grain size can be controlled within a desired range. The key to achieving the desired effect in this application is to control the grain size within the limited range specified in this application.

[0127] Comparative Example 5 1. According to the formula in Table 1, add the specified amount of lanthanum nitrate to 5 L of deionized water and stir for 10 minutes to fully dissolve it. Then, add 1 L of aqueous ammonia (NH3·H2O) solution and stir to neutralize. The resulting mixture was sprayed evenly onto the blue tungsten in the doping pot and stirred. The volume ratio of the lanthanum nitrate solution to the aqueous ammonia (NH3·H2O) solution was 5:1. 2. The doping pot was evacuated and stirred with water while heating (heating temperature 80°C, vacuum degree -0.025MPa). 3. In a vacuum state, the powder was dried using a steam heating method, the steam pressure was set to 0.1-0.3 MPa, and the vacuum degree in the pot was set to -0.02 MPa or less. Finally, a tungsten-lanthanum doped powder with uniform doping and low impurity content was obtained. 4. The tungsten-lanthanum doped powder was reduced once in a reduction furnace with four temperature zones of 650°C, 750°C, 850°C, and 900°C to produce tungsten-lanthanum powder with appropriate particle size. 5. According to the formulation in Table 1, 5 L of deionized water was added to a doping pot and heated to 80°C. A predetermined amount of ammonium rhenate was then added and stirred for 10 minutes to fully dissolve. A predetermined amount of tungsten-lanthanum powder was then added to the ammonium rhenate solution and stirred for 30 minutes. The powder was then dried using a steam heating method under vacuum, with the steam pressure set to 0.1-0.3 MPa and the vacuum level in the pot set to -0.02 MPa or less. Finally, a uniformly doped rhenium-doped tungsten-lanthanum powder with low impurity content was obtained. 6. The rhenium-doped tungsten-lanthanum powder was reduced once in a reduction furnace with four temperature zones 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. 7. The obtained tungsten-lanthanum rhenium alloy powder and tungsten carbide were placed in a high-speed powder mixer and mixed for 2 hours, then sieved to obtain a mixed tungsten-lanthanum rhenium alloy powder. 8. Using the isostatic pressing method, powder with a particle size of 1.5 μm was pressed into a green compact weighing 3.0 kg at a pressure of 180 MPa, and the green compact was then pre-sintered at low temperature in a hydrogen atmosphere to improve its strength. 9. High-temperature sintering method, oxide particle size less than 2.0 μm, density 18.0 g / cm 3 A sintered billet of 10 ... 10. The sintered billet 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 by multiple rotary swaging and drawing processes, where the process and conditions of the steps were consistent with those of Example 1. 11. 0.52 mm black wire was electrolytically cleaned to 0.50 mm ± 0.005 mm tungsten-lanthanum-rhenium alloy white wire, which can be processed into filaments for microwave heating devices. 12. A spring-shaped cathode filament for the heating device was prepared by winding 10 turns of 0.50 mm tungsten-lanthanum-rhenium alloy white wire with a pitch of 1.29 ± 0.03 mm. 13. The filament was assembled into a cathode structure together with other components such as assemblies, ceramics, and tabs by heat treatment at 600°C. 14. The filament in the cathode structure was welded integrally to the cap of the assembly. 15. The cathode structure was placed in a carbonization tank and carbonized. After evacuation, a carbon-containing hydrocarbon gas (specifically, methane) was introduced, and a constant direct current (current value: 16 A) was applied to the cathode to heat it, and the filament was carbonized in the hydrocarbon gas. 16. Assembly of the white sphere: The cathode structure, anode cylinder, antenna cap, and other components were assembled into a single unit. 17. The white bulb was evacuated and vacuumed, and then subjected to high-temperature burn-in to activate the black bulb and its emission performance. 18. The black sphere, heat sink, magnet, tube shell, etc. were assembled to finally obtain a heating device member including the filament, which was then installed in a microwave oven for use.

[0128] The tungsten alloy wire, tungsten alloy filament, and the device (microwave oven) including the filament member manufactured in the above examples and comparative examples were tested for the relevant performance indexes under the same test conditions. The test results are shown in the following table.

[0129] [Table 2] TIFF2026505917000005.tif183164

[0130] [Table 3]

[0131] In Tables 2 and 3, 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 fusing current, and the conversion method between FC% and °C is as follows: As shown in Figure 21, Section 4.3.2.2 of GB / T 23272-2009 National Standard for Tungsten Wire for Lighting and Electronic Equipment, Section 4.3.2.2, for the high-temperature performance test method, provides a reference relationship between FC% and temperature. Conversion can be performed by referring to this relationship. The electron work function was measured using the Richardson linear method. The service life of the tungsten alloy filament was tested according to Section 6.5.2 of GB / T 23152-2008 National Standard for Household Microwave Oven Heating Devices. This standard specifies that the continuous operating time of microwave heating devices must exceed 500 hours. The manufacturing process and test nodes for steps 10-14 in this example are shown in Figure 20.

[0132] 1. Comparison between Example 1 and Comparative Example 1 (Comparative Example 1 is a thorium-tungsten filament) The metal structure states of Example 1 and Comparative Example 1 at various fusing currents are shown in Figures 5 to 11. It was revealed that the recrystallization temperature of Example 1 was 50% FC (approximately 2120°C), and the recrystallization temperature of Comparative Example 1 was 46% FC (approximately 2020°C). It was found that the recrystallization start temperature of the filament material of the present invention is higher than the recrystallization start temperature of the original thorium-tungsten wire material.

[0133] The grain sizes of the filaments after carbonization in Example 1 and Comparative Example 1 are shown in Figures 12 and 13. Figure 13 shows that the filament structure after carbonization in Example 1 remains a fine-grained structure, while Figure 12 shows that the grains in the filament structure after carbonization in Comparative Example 1 have become significantly larger. From the data, it can be seen that the number of grains in the tungsten matrix 100 after carbonization of the matrix 100 is 4000 grains / mm in Example 1. 2 In Comparative Example 1, the density was 100 pieces / mm 2It was found that the crystal grain width of the carbonized layer 200 was 6.83 μm in Example 1 and 9.81 μm in Comparative Example 1.

[0134] The distribution of channels 210 in the carbonized filaments of Example 1 and Comparative Example 1 is shown in Figures 14 to 16. Figure 14 shows that in the structure of the carbonized layer 200 in the cross section of the carbonized filament of Example 1, a large number of first channels 211 are distributed substantially perpendicular to the filament edge, and the second channels 212 and the first channels intersect and are distributed substantially annularly, resulting in a laminated lattice structure of the carbonized layer 200. Figure 15 shows that in the structure of the carbonized layer 200 in the longitudinal cross section of the carbonized filament of Example 1, a large number of first channels 211 are distributed substantially perpendicular to the filament edge. On the other hand, in the structure of the carbonized layer 200 in the cross section of the carbonized filament of Comparative Example 1 shown in Figure 16, the number of first channels 211 substantially perpendicular to the filament edge is significantly reduced, and the distribution of parallel second channels 212 is also very small. This is because the crystal grain width of the carbonized layer of Comparative Example 1 is relatively large, the number of channels 210 is related to the size of the crystal grains, and the size of the crystal grains affects the formation of the channels 210.

[0135] In Example 1 of the present application, oxides of M are distributed in a layered structure in the carbonized layer 200 separated by second channels 212. The first channels 211 are distributed approximately perpendicular to the filament edges and connect the interior of the matrix 100, the second channels 212, and the filament edges. The combination of the second channels 212 and the first channels 211 is beneficial to the outward migration of rare earth atoms to timely replenish the rare earth elemental elements evaporated from the surface, thereby improving the emission stability of the material.

[0136] 2. Comparison of Example 1 and Comparative Example 4 (Comparative Example 4 differs from Example 1 in that the size of the crystal grains in the carbonized layer is significantly larger) 17 and 18, the channels 210 distributed in the structure of the carbonized layer 200 in the cross section and longitudinal section of the filament after carbonization of Comparative Example 4 are clearly approximately parallel to the outer edge 220 of the filament, and do not form a stacked block structure. From the data in Tables 2 and 3, it can be seen that the emission performance of Example 1 is stable even after 30 minutes of operation, whereas in Comparative Example 4, microwave disappearance occurs after less than 10 minutes of operation, and the emission effect is unstable.

[0137] The analysis of the mechanism is as follows.

[0138] The carbonized layer 200 of Comparative Example 4 also has a structure similar to the channels 210, but these channels 210 are parallel to the filament edges, resulting in a layered cross section of the carbonized layer 200. The reason for this is believed to be as follows: The crystal grain size of the carbonized layer 200 is relatively large at 23.12 μm. The crystal grain size affects the formation of the channels 210, making it difficult to form a large number of vertically distributed channels 210 within the carbonized layer 200. The layered structure of the carbonized layer 200 separates the interior of the matrix 100 from the filament edges. When rare earth atoms migrate from the interior to the exterior and encounter channels 210 parallel to the filament edges, their migration is hindered, preventing or making further diffusion to the exterior difficult, resulting in reduced emission performance.

[0139] In contrast, in Example 1 of the present application, the crystal grain size in the carbonized layer 200 is small (6.83 μm), resulting in the formation of a relatively large number of first channels 211 intersecting with the second channels 212, forming a layered lattice structure in the carbonized layer 200. The layered structure in the carbonized layer 200 separated by the second channels 212 contains oxides of M. The first channels 211 are distributed approximately perpendicular to the filament edges and connect the interior of the matrix 100, the second channels 212, and the filament edges. The greater the number of channels 210, the more beneficial it is for the migration of rare earth atoms. In Example 1, the combination of the second channels 212 and the first channels 211 is beneficial for the outward migration of rare earth atoms to timely replenish the rare earth elemental elements evaporated from the surface, thereby improving the emission stability of the material.

[0140] 3. Comparison between Example 2 and Comparative Example 2, and Comparison between Example 4 and Comparative Example 3 3.1 The difference between Example 2 and Comparative Example 2 is that in Comparative Example 2, no carbide raw material was added, and no carbon was present in the components.

[0141] Comparing the results of both cases, the following was found: Compared with Example 2, Comparative Example 2 had a lower recrystallization temperature, wider crystal grains in the carbonized layer, and the carbonized layer 200 had a blocky structure. This was reflected in performance, resulting in a decrease in the stability of emission performance, a decrease in electron emission performance, and a shortened service life.

[0142] 3.2 The difference between Example 4 and Comparative Example 3 is that Comparative Example 3 does not contain any added carbide raw material, and therefore does not contain carbon. Comparing the results of the two, the following was found: Compared to Example 4, Comparative Example 3 has a lower recrystallization temperature, a wider grain width in the carbonized layer, and a blocky structure in the carbonized layer 200. This is reflected in performance, resulting in a decrease in the stability of emission performance, a decrease in electron emission performance, and a shorter service life.

[0143] The analysis of the mechanism is as follows.

[0144] In the examples of the present application, by adding one or more types of M oxides and carbides or elemental carbon, the M oxides in the tungsten matrix react with the carbides at high temperatures, and the resulting M metal atoms become much smaller than the M oxide particles, thereby accelerating the rate of migration and diffusion of the M metal atoms in the tungsten matrix. Therefore, compared to thorium-tungsten filaments, equivalent or superior electron emission performance can be achieved at a lower operating voltage (excitation temperature). On the other hand, in Comparative Examples 2 and 3, the absence of a carbon raw material prevents the above effect from being achieved, resulting in reduced electron emission performance.

[0145] 4. Comparison between Comparative Example 7 and Comparative Example 5 The difference between Example 7 and Comparative Example 5 is that the Re content in Comparative Example 5 exceeds the range limited by the present application.

[0146] Comparing the results of both examples, it was found that Comparative Example 5 had a higher operating temperature and a shorter operating life. The applicants' analysis revealed that rhenium has the effect of purifying grain boundaries and strengthening the wire by forming a solid solution of rhenium and tungsten. However, if the rhenium content exceeds the range limited by the present application, the rhenium content becomes too high, the strengthening effect becomes too great, and work hardening becomes too great, making the wire material more susceptible to cracking. The flaw detection data for the wire material revealed that in Example 7, the number of flaw detection cracks was 0.8 to 1.5 per 100 meters, while in Comparative Example 5, the number of flaw detection cracks was 6 to 10 per 100 meters.

[0147] From the above, the following conclusions can be clearly drawn from the test results of the Examples and Comparative Examples.

[0148] 1. The carbonized layer 200 of the cross-sectional structure, the longitudinal-sectional structure, and the longitudinal-cut structure was observed. The carbide layer 200 of the present thorium-free tungsten lanthanum filament has smaller grain size and slightly narrower grain width than the thorium-tungsten filament, resulting in a larger number of channels 210 in the present carbide layer 200. The structure of the carbide layer 200 at various positions on the present filament resembles a crossing of first channels 211 and second channels 212, forming a stacked block structure. The first channels 211 are distributed approximately perpendicular to the filament edges and connect to the second channels 212, the interior of the matrix 100, and the filament edges. This is beneficial for the outward migration of rare earth atoms to timely replenish the rare earth elements evaporated from the surface, thereby improving the emission stability of the material. The emission performance stabilization time data from the test results clearly showed differences in the emission performance of the filaments. Here, the emission performance of the present filament was stable and comparable to that of conventional thorium-tungsten filaments.

[0149] The tungsten carbide alloy material of the present application replenishes the rare earth element evaporated from the surface by the stable migration of the rare earth element outward, thereby improving the emission stability of the material. It has been found that the stable emission ability of the conventional thorium-tungsten filament can be achieved without adding thorium element, solving the problem of the low stable emission ability of the existing thorium-free tungsten filament and eliminating the problem of radioactive contamination that occurs with the conventional thorium-tungsten filament.

[0150] 2. During the manufacturing of the filament, there is a carbonization process at a temperature of 2000-2200°C. The original thorium-tungsten filament is carbonized at this temperature, and the crystal grain structure shows recrystallization, resulting in coarse crystal grains. This means that the filament breaks very easily after carbonization, and even a slight increase in vibration during the production process will cause breakage (the breakage rate is approximately 20,000-30,000 ppm).

[0151] The recrystallization temperatures measured in Examples 1 to 7 were 48% FC (approximately 2070°C) to 52% FC (approximately 2180°C), and the recrystallization temperature in Comparative Example 1 was 46% FC (approximately 2020°C). The recrystallization onset temperature of the filament material produced in this application is higher than that of the original thorium-tungsten wire, and the filament structure after carbonization remains a fine-grained structure (the grain size in the Examples of this application is significantly smaller than that in the Comparative Example), and filaments with a fine-grained structure are less likely to break.

[0152] 3. From the test results, it is clear that the number of cracks per 100 meters and the yield parameters of the filament material of the present application are superior to existing thorium-tungsten, with fewer cracks to be detected (when the filament diameter is 500 μm, the number of cracks to be detected in the filament is less than 2 per 100 meters), the processing yield is high, the wound filament is less likely to break, production efficiency is improved, there are fewer cracks in the wire material, and the rate of breakage due to carbonization in the produced filament is also low.

[0153] 4. The electron emission performance parameters in the test results clearly showed that the DC emission capability of the heating device manufactured with the filament of the present invention was approximately one time higher than that of the thorium-tungsten filament (Comparative Example 1). This allows the heating device manufactured with the filament of the present invention to excite electrons at a lower voltage. (Note: According to the application of heating devices in this field, the starting voltage of a thorium-tungsten heating device must be at least 2.0 V or higher. To ensure starting, the operating voltage is set to 3.3 V, but the starting voltage of Example 1 can be 1.4 V, and the operating voltage can be in the range of 1.6 to 1.8 V.)

[0154] The operating temperature of the heating device of the present application can be reduced from 1500-1600° C. to 1100-1500° C., for example, in the range of 1200-1300° C., while the operating temperature of a conventional thorium-tungsten filament is 1600-1900° C. Therefore, both the energy consumption and the lifespan of the heating device of the present application are improved.

[0155] As described above, in the present embodiment, the control of the crystal grain size of the carbonized layer 200 is combined with the M element contained in the carbonized layer 200, thereby replenishing the rare earth element evaporated from the surface layer by the stable migration of the rare earth to the outside, thereby improving the emission stability of the material. The stable emission capability of conventional thorium-tungsten filaments can be achieved without adding thorium, solving the problem of the low stable emission capability of existing thorium-free tungsten filaments, and is more environmentally friendly as it does not have the problem of radioactive contamination associated with conventional thorium-tungsten filaments.

[0156] In the present application, by doping the tungsten matrix powder with M oxides and carbides, the recrystallization start temperature of the material can be significantly increased, resulting in extremely fine grains even at the same carbonization temperature as thoriated tungsten. This improves the material's processability, reduces the breakage rate during production and use, and reduces the material's electronic work function. Not only does this reduce the breakage rate and improve yield, thereby reducing production and transportation costs, but it also effectively extends the filament's service life, reaching or even exceeding that of existing thoriated tungsten filaments.

[0157] In summary, the above technical solutions of the present application include at least the following working principles or mechanisms and beneficial effects:

[0158] (1) The grain width in the carbonized layer 200 of the present filament is controlled within a small, fixed size range, ranging from 1.0 to 15.0 μm. The grain size of the carbonized layer 200 in the thorium-free filament is smaller than that of a thorium-tungsten filament, and the grain width is slightly narrower than that of a thorium-tungsten filament. The carbonized layer 200 of the present invention has a larger number of channels 210. The structure of the carbonized layer 200 at various positions within the filament of the present invention resembles a laminated lattice structure in which first channels 211 and second channels 212 intersect. The first channels 211 are distributed approximately perpendicular to the filament edge and are connected to the interior of the matrix 100, the second channels 212, and the filament edge. This is beneficial for rare earth atoms to migrate outward and replenish the rare earth elements evaporated from the surface in a timely manner, thereby improving the substance release stability.

[0159] (2) The recrystallization start 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 are relatively fine, and the filament after carbonization is less brittle than conventional thorium-tungsten filament materials, reducing the breakage rate during production and use.

[0160] (3) The processability of the filament material of the present application is superior to that of existing thorium-tungsten, with fewer flaw detection cracks (when the filament wire diameter is 500 μm, the number of flaw detection cracks in the filament is less than 2 per 100 meters), the processing yield is high, the wound filament is less likely to break, production efficiency is improved, there are fewer cracks in the wire material, and the rate of breakage due to carbonization in the manufactured filament is also low.

[0161] In the filament material of the present invention, the oxide of M (e.g., lanthanum oxide particles) has good plasticity. As pressure processing progresses, the oxide particles of M become elongated and exist in a linear or near-linear shape. In contrast, the thorium oxide in conventional thorium-tungsten materials has low plasticity, and when thorium-tungsten is processed to a certain extent, the thorium oxide breaks down. As processing progresses further, the thorium oxide appears as a row of particles. Due to the type of rare earth oxide added in the present invention and the change in morphology during the refinement process, the filament material has excellent processability. When manufacturing wire material for winding the filament, the wire diameter of the filament material can be reduced to 500 μm or less, effectively reducing the number of cracks detected during inspection and thereby improving yield.

[0162] (4) The thickness of the carbonized layer 200 of the filament of the present invention is preferably controlled to 30 to 90 μm.

[0163] The thickness of the carbide layer 200 of a conventional thorium-tungsten filament is typically 35 to 45 μm. The thicker the carbide layer 200, the longer the service life of the heating device. The carbide layer 200 of a conventional thorium-tungsten filament must not be too thick, because if it is too thick, the recrystallized grains of the tungsten matrix 100 after carbonization will become large and coarse, making the carbonized filament very brittle. This can lead to a filament breakage rate of 10,000 to 30,000 ppm in heating devices during production and use.

[0164] Currently, the thickness of the carbonized layer 200 of the filament in the embodiments of the present application is also basically 35 to 50 μm. Unlike thoriated tungsten filaments, the present application allows for the thickness of the carbonized layer to be increased, which is advantageous for extending the service life. The recrystallization start temperature of the present application is relatively high, and the structure of the tungsten matrix 100 after carbonization remains a fine-grained structure, resulting in an extremely low filament breakage rate. In this way, the present application allows for the thicker carbonized layer 200 to extend the service life while maintaining a low filament breakage rate.

[0165] (5) The operating temperature of the heating device according to the present invention (i.e., the operating temperature of the filament) can be reduced from 1500-1600°C to 1100-1500°C, for example, 1200-1300°C, while maintaining good operating conditions. In contrast, the operating temperature of a conventional thorium-tungsten filament is 1600-1900°C. Therefore, the energy consumption and lifespan of the filament according to the present invention and the heating device manufactured therewith are both improved.

[0166] As described above, in the filament of the present invention, by adding one or more oxides and carbides or elemental carbon of M to the tungsten matrix 100, the combination of oxides and carbides or elemental carbon can accelerate the diffusion rate of materials within the matrix 100. Compared to thorium-tungsten filaments, the filament of the present invention can achieve the same or better electron emission capacity at a lower operating voltage (excitation temperature). Furthermore, the grain size of the carbide layer 200 is controlled within a small range, and the structure of the channels 210 formed on the surface of the carbide layer 200 of the filament gives the carbide layer 200 a layered lattice structure. The first channels 211 are distributed approximately perpendicular to the second channels 212 and the filament edge. This is beneficial for the outward migration of rare earth atoms to timely replenish the rare earth elements evaporated from the surface, thereby improving the emission stability of the material. The tungsten alloy filament material of the present invention can replace existing thorium-tungsten filament cathodes and has a lifespan equal to or longer than that of thorium-tungsten. In this application, by doping tungsten matrix 100 powder with M oxides and carbides or elemental carbon, the recrystallization start temperature of the material can be significantly lowered, the material's workability improved, the material's electronic work function reduced, and the filament's crystal grain structure refined. This not only reduces the rate of wire breakage and cuts production and transportation costs, but also effectively extends the service life of the filament, reaching or far exceeding that of existing thorium-tungsten filaments.

[0167] The filament of the present invention can achieve an extremely high recrystallization temperature and can obtain extremely fine grains even at the same carbonization temperature as thorium-tungsten. This material has excellent vibration resistance, which reduces the risk of filament breakage and failure during production, transportation, and use.

[0168] In this specification, "~" is used to represent a range of values, and the range represented by this expression includes two endpoints.

[0169] Therefore, the specific parameters or some commonly used reagents or raw materials in the above examples are specific or preferred examples within the concept of the present application, and are not intended to limit the scope thereof, and those skilled in the art can make adaptive adjustments within the concept and scope of protection of the present application.

[0170] It should be noted that the specific parameters or commonly used reagents in the above examples are specific or preferred examples based on the concept of the present application, and are not intended to limit the scope thereof, and those skilled in the art can make adaptive adjustments within the concept and scope of protection of the present application.

[0171] Furthermore, unless otherwise specified, the raw materials used may be products commonly available in the art or may be prepared by methods commonly known in the art.

[0172] Furthermore, those skilled in the art should understand that although there are many problems in the prior art, each embodiment or technical solution of the present application does not necessarily solve all of the technical problems described in the prior art or background art at the same time, but can improve only one or several aspects. Those skilled in the art should understand that the content not described in a claim should not be considered a limitation on that claim.

[0173] In this specification, terms such as carbonized layer, matrix, and channel are frequently used, but the use of other terms is not excluded. These terms are used only to more conveniently explain and interpret the essence of this application. Interpreting them as any additional limitations would be contrary to the spirit of this application.

[0174] It should be noted that the above embodiments are only used to explain the technical solutions of the present application, and are not intended to limit the same. Although the present application has been described in detail with reference to the above embodiments, those skilled in the art may still modify the technical solutions described in the above embodiments or replace some or all of the technical features with equivalents, and such modifications or replacements shall not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application. [Explanation of symbols]

[0175] 100 Matrix 200 carbonized layer 210 channels 220 outer edge of filament 211 Channel 1 212 Second Channel

Claims

1. A tungsten carbide alloy filament, a matrix and a carbonized layer attached to an outer surface of the matrix; The carbonized layer has a crystal grain width of 1.0 μm to 15.0 μm, the components of both the matrix and the carbide layer include tungsten, carbon, oxygen, and M elements; the M element is one or a combination of two or more selected from La, Y, Sc, Nd, Sm, Lu, Ce, Gd, Tb, Dy, Ho, Pr, Er, Tm, Yb, Eu, Hf, and Zr; A tungsten carbide alloy filament characterized in that the components of the tungsten carbide alloy filament do not contain thoriated tungsten element.

2. The tungsten carbide alloy filament of claim 1, characterized in that the M element in the carbonized layer exists in the form of oxide, the particle size of the M oxide particle is 10nm to 1000nm, and the carbon element in the carbonized layer exists in the form of carbide.

3. a number of second channels are distributed in the carbonized layer, thereby forming a layered structure stacked radially in a cross section of the alloy filament; 2. The tungsten carbide alloy filament of claim 1, wherein a number of first channels are distributed in the carbide layer, and at least a portion of the first channels are arranged crossing the second channels, thereby dividing the layered structure into a number of block-like structures.

4. A number of first channels are distributed in the carbonized layer, and at least some of the first channels are distributed in the radial direction of the cross section of the alloy filament, and / or at least some of the first channels point to the center of the cross section of the alloy filament; 2. The tungsten carbide alloy filament of claim 1, wherein the carbonized layer has a number of second channels distributed therein, at least some of the second channels being distributed in the circumferential direction of the cross section of the tungsten carbide alloy filament, and at least some of the second channels being arranged crosswise with the first channels.

5. The carbonized layer contains W. 2 C and WC, 2 2. The tungsten carbide alloy filament according to claim 1, wherein the weight ratio of C to WC is (60-100):(0-40).

6. 2. The tungsten carbide alloy filament according to claim 1, wherein the M element is present in the form of an oxide in the matrix, and the carbon element is present in the form of a carbide or elemental carbon.

7. The tungsten carbide alloy filament of claim 1, characterized in that said matrix comprises: carbon element 0.0005~0.3wt%, said M element 0.25~2.6wt%, oxygen element 0.05~0.5wt%, and the remaining amount of said tungsten element and inevitable impurities.

8. Among the components of the matrix, the M element exists in the form of an oxide, and the carbon element exists in the form of a carbide or elemental carbon, the oxide of M is one or a combination of two 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; 8. The tungsten carbide alloy filament according to claim 7, characterized in that the carbide is selected from the group consisting of lanthanum carbide, zirconium carbide, yttrium carbide, hafnium carbide, and tungsten carbide, or a combination of multiple types.

9. The tungsten carbide alloy filament of claim 7, characterized in that the matrix component further comprises a metal element T element, and said T is at least one selected from K, Re, Mo, Fe, Co.

10. 10. The tungsten carbide alloy filament according to claim 9, wherein the mass content of Re is less than 1000 ppm.

11. 2. The tungsten carbide alloy filament according to claim 1, wherein the diameter of the tungsten carbide alloy filament is 800 μm or less.

12. 2. The tungsten carbide alloy filament of claim 1, wherein the operating temperature of the tungsten carbide alloy filament is 1100°C to 1500°C.

13. 2. The tungsten carbide alloy filament according to claim 1, characterized in that the tungsten carbide alloy filament has a helical structure, with the thickness of the carbide layer of at least one helical coil reaching 30 μm to 90 μm.

14. A method for producing the tungsten carbide alloy filament according to any one of claims 1 to 13, Doping and powder production: A step of producing a finished powder raw material product in the order of a doping process (solid-liquid doping or solid-solid doping), a reduction process, and a powder production process; Powder pressing: by isostatic pressing, the powder raw material finished product is pressed into a powder compact, and the powder compact is pre-sintered at a low temperature in a hydrogen atmosphere to obtain a pre-sintered billet; High-temperature sintering: sintering the pre-sintered billet at a high temperature by a high-temperature sintering method to obtain a sintered billet; Pressure processing: reducing the sintered billet to a tungsten alloy wire of a certain diameter, wherein an oxidation annealing treatment is performed during the reduction; Cleaning: cleaning the tungsten alloy wire into a tungsten alloy white wire; Winding: winding the tungsten alloy white wire into a spring-like filament structure; Assembling the cathode: assembling the spring-like filament structure together with the assembly, ceramics, and tab members into a cathode structure by heat treatment; Welding: welding a filament structure within the cathode structure to a cap of the assembly; carbonization: carbonizing the welded cathode structure.

15. The temperature rise curve of the high-temperature sintering step is as follows: The temperature is raised from room temperature to A1, the temperature rise time H1 is (5 to 8) hours, A1 is (950 to 1250) ° C, the temperature is kept at A1 for H2 hours, H2 is (1 to 3), the temperature is raised from A1 to A2, the temperature rise time is H3, H3 is (1.5 to 2.5) hours, A2 is (1300 to 1500) ° C, the temperature is kept at A2 for H4 hours, H4 is (2.5 to 4.5), the temperature is raised from A2 to A3, The temperature rise time is H5, H5 is (1 to 3) hours, A3 is (1700 to 1900) ° C., the temperature is maintained at A3 for H6 hours, H6 is (1 to 3), the temperature is raised from A3 to A4, the temperature rise time is H7, H7 is (1 to 3) hours, A4 is (2050 to 2250) ° C., the temperature is maintained at A4 for H8 hours, H8 is (5 to 10), and natural cooling is performed from A4 to obtain a sintered billet, The process of the pressure processing step is as follows: The manufacturing method of claim 14, characterized in that described sintered billet is thinned into the intermediate wire rod of diameter 1.5~3.5mm, and then described intermediate wire rod is oxidized and annealed at (1200~1500) ℃ and annealing speed (3~10)m / min to obtain described tungstenalloy wire.

16. 1. A heating device comprising: A heating device comprising a tungsten carbide alloy filament according to any one of claims 1 to 13.

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