Tungsten carbide alloy filament and preparation method therefor, and heating device

Abstract

The present invention relates to the technical field of filament cathode materials. Disclosed are a tungsten carbide alloy filament and a preparation method therefor, and a heating device. The tungsten carbide alloy filament comprises a base body (100) and a carbonization layer (200) attached to the outer surface of the base body (100), wherein the grain width of the carbonization layer (200) is 1.0-15.0 μm; the components of the base body (100) and the carbonization layer (200) both comprise tungsten, carbon, oxygen and an M element, the M element being selected from one or a combination of more of La, Y, Sc, Nd, Sm, Lu, Ce, Gd, Tb, Dy, Ho, Pr, Er, Tm, Yb, Eu, Hf and Zr; and the components of the tungsten carbide alloy filament do not contain thorium. The material improves the emission stability of the tungsten alloy filament, and can also reach stable emission capability of a traditional thorium-tungsten filament without adding thorium, thereby solving the problem of relatively poor stable emission capability of an existing thorium-free tungsten filament, and avoiding the radioactive contamination problem of a traditional thorium-tungsten filament.

Description

Tungsten carbide alloy filament, preparation method thereof, and heating device

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on October 25, 2023, with application number 2023113863234 and invention name “A tungsten carbide alloy filament, its preparation method, and heating device”, the entire contents of which are incorporated by reference into this application. Technical Field

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

[0003] The filament cathode, the electron emitter, is widely used in microwave oven magnetrons. Its performance significantly impacts the operating characteristics and lifespan of the magnetron and is considered the heart of the magnetron. Existing filament materials are primarily made of tungsten-thorium oxide or tungsten-rare earth oxides, such as:

[0004] The Chinese invention patent with application number CN201010299139 and publication date April 3, 2013, discloses a method for doping powder for magnetron coils. The process of the invention includes steps such as doping, stirring, and steam drying. The method is characterized in that a neutralizing additive, ammonia NH3·H2O solution, is added to a thorium nitrate solution, and the prepared mixed solution is evenly sprayed onto the surface of blue tungsten WO2.9 placed in a doping pot and stirred. The doping pot is evacuated and heated with water while stirring. Under vacuum, the powder is dried by steam heating, and finally a doped tungsten-thorium oxide powder with uniform doping and low impurity content is obtained.

[0005] This invention patent (application number CN201010299139) adds thorium oxide to pure tungsten, achieving a magnetron coil material life of more than 1,000 hours of continuous operation. However, the cathode product made of this composite material has a high brittle-ductile transition temperature and is difficult to process and form, which can easily cause the magnetron cathode to break during production and transportation. In addition, the recrystallization temperature is low, and the magnetron coil will undergo abnormal recrystallization growth during the carbonization process, often breaking during use and transportation, causing the magnetron to fail. At the same time, thorium is a radioactive element. Using thorium as the main added raw material pollutes the environment during smelting, production, transportation and use, and the final product also has potential adverse effects on the human health of those who come into contact with it.

[0006] A Chinese invention patent application, CN201410073749.9, published on June 11, 2014, discloses a non-radiative multi-element composite tungsten cathode material for microwave oven magnetrons and its preparation process. The tungsten cathode material contains lanthanum oxide, zirconium oxide, yttrium oxide, lutetium oxide, rhenium, and tungsten. Each rare earth oxide accounts for 0.5% to 1.5% of the tungsten electrode material by weight, the total rare earth oxide content is 2% to 3% of the tungsten electrode material by weight, rhenium as an alloying element accounts for 1% to 4% of the tungsten electrode material by weight, and the remainder is tungsten. The preparation method for this non-radiative multi-element composite rare earth tungsten alloy electrode material for microwave oven magnetrons includes solution preparation, drying, reduction, acid washing, cold isostatic pressing, sintering, vertical melting, medium-frequency induction annealing, press working, winding, and mechanical straightening.

[0007] Regarding this invention patent (application number CN201410073749.9), some peers added multi-element rare earth oxides to the tungsten matrix to avoid thorium radiation. This material has a strong instantaneous emission capability, but a weak stable emission capability. Its service life is far from the life standard of thoriated tungsten magnetron coils, and is generally only a few dozen hours. In addition, the use of metallic rhenium is expensive, which is not conducive to its promotion and use in the industry.

[0008] In summary, conventional tungsten-thorium filaments are radioactive, not only polluting the environment but also potentially adversely affecting the health of those exposed to them. Furthermore, existing filaments that don't incorporate thorium also suffer from poor emission stability. Solving these problems is a challenge that those skilled in the art are striving to overcome.

[0009] Summary of the Invention

[0010] To address the problems existing in the above-mentioned prior art: the radioactivity of conventional tungsten-thorium filaments not only pollutes the environment, but also potentially adversely affects the health of those exposed to the final product. In addition, existing filaments that do not use thorium addition have the disadvantage of poor stable emission capabilities. This application provides a tungsten carbide alloy filament. The specific technical solution is as follows:

[0011] The tungsten carbide alloy filament includes a substrate and a carbide layer attached to the outer surface of the substrate; the grain width of the carbide layer is 1.0 μm to 15.0 μm; the components of the substrate and the carbide layer both contain tungsten, carbon, oxygen and M; the M element is selected from one or more combinations of La, Y, Sc, Nd, Sm, Lu, Ce, Gd, Tb, Dy, Ho, Pr, Er, Tm, Yb, Eu, Hf and Zr; wherein the components of the tungsten carbide alloy filament do not contain thorium.

[0012] In some embodiments, the M element in the carbonized layer exists in the form of an oxide, the particle size of the M oxide particles is 10 nm to 1000 nm, and the carbon element exists in the form of a carbide.

[0013] In some embodiments, a plurality of second channels are distributed on the carbonized layer to form a radially stacked layered structure on the cross section of the filament; a plurality of first channels are distributed on the carbonized layer, and at least some of the first channels are cross-arranged with the second channels to divide the stacked layered structure into a plurality of block structures.

[0014] In some embodiments, a plurality of first channels are distributed on the carbide layer; at least part of the first channels are distributed radially along the cross section of the filament; and / or, at least part of the first channels point to the center of the cross section of the filament; a plurality of second channels are distributed on the carbide layer; at least part of the second channels are distributed circumferentially along the cross section of the tungsten alloy filament; wherein, at least part of the second channels are cross-arranged with the first channels.

[0015] In some embodiments, the carbonized layer comprises W2C and WC; the weight ratio of W2C to WC is (60-100):(0-40).

[0016] In some embodiments, 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 a single carbon substance.

[0017] In some embodiments, the matrix comprises the following components: 0.0005-0.3 wt % carbon element, 0.25-2.6 wt % M element, 0.05-0.5 wt % oxygen element, and the balance being tungsten element and unavoidable impurities.

[0018] In some embodiments, among the components of the matrix, the element M exists in the form of an oxide, and the element carbon exists in the form of a carbide or a carbon element; the oxide of M is selected from one or more combinations 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; the carbide is selected from one or more combinations of lanthanum carbide, zirconium carbide, yttrium carbide, hafnium carbide, and tungsten carbide.

[0019] In some embodiments, the components of the matrix further include a metal element T; T is selected from at least one of K, Re, Mo, Fe, and Co.

[0020] In some embodiments, the mass content of Re is less than 1000 ppm.

[0021] In some embodiments, the diameter of the tungsten carbide alloy filament is 800 μm or less.

[0022] In some embodiments, the operating temperature is 1100°C to 1500°C.

[0023] In some embodiments, the tungsten carbide alloy filament is a spiral structure with a pitch of 0.800 to 1.800 mm, a length of 10.00 to 16.00 mm, and an outer diameter of 3.00 to 6.00 mm.

[0024] In some embodiments, the tungsten carbide alloy filament has a spiral structure, and the thickness of the carbide layer of at least one spiral turn reaches 30 μm to 90 μm.

[0025] The present application provides a method for preparing the tungsten carbide alloy filament as described above, which comprises the following steps:

[0026] S1. Doping and powdering: preparing the finished powder raw material through the doping process, the reduction process and the powdering process in sequence; wherein the doping process is solid-liquid doping or solid-solid doping;

[0027] S2. Powder pressing: Using isostatic pressing, the finished powder raw material is pressed into a compact, and the compact is pre-sintered at a low temperature in a hydrogen atmosphere to obtain a pre-sintered billet;

[0028] S3. High temperature sintering: sintering the pre-sintered billet at high temperature to obtain a sintered billet;

[0029] S4, pressure processing: reducing the diameter of the sintered billet into a tungsten alloy wire of a certain diameter; wherein, oxidation annealing treatment is performed during the reducing process;

[0030] S5. Cleaning: Clean the tungsten alloy wire into white tungsten alloy wire;

[0031] S6. Winding: Winding the tungsten alloy white wire into a spring-shaped filament structure;

[0032] S7, cathode assembly: assembling the spring-shaped filament structure with components, ceramics, and lead parts into a cathode structure through heat treatment;

[0033] S8, welding: welding the filament structure in the cathode structure to the component end cap;

[0034] S9. Carbonization: Carbonize the welded cathode structure.

[0035] The present application also provides a heating device, which includes the above tungsten carbide alloy filament.

[0036] In some embodiments, the temperature rise curve of the high temperature sintering step is: from room temperature to A1, the heating time H1 is (5-8) h, A1 is (950-1250) ° C; keep warm at A1 for H2 hours, H2 is (1-3); from A1 to A2, the heating time is H3, H3 is (1.5-2.5) h, A2 is (1300-1500) ° C; keep warm at A2 for H4 hours, H4 is (2.5-4 .5); heating from A2 to A3, heating time is H5, H5 is (1-3) h, A3 is (1700-1900) ° C; keeping warm at A3 for H6 hours, H6 is (1-3); heating from A3 to A4, heating time is H7, H7 is (1-3) h, A4 is (2050-2250) ° C; keeping warm at A4 for H8 hours, H8 is (5-10); naturally cooling from A4 to obtain sintered billets.

[0037] In some embodiments, the process of the pressure processing step is: thinning the sintered billet into an intermediate-gauge wire with a diameter of 1.5 to 3.5 mm; then oxidizing and annealing the intermediate-gauge wire at (1200 to 1500)°C at an annealing speed of (3 to 10) m / min to obtain a tungsten alloy wire.

[0038] Based on the above, compared with the existing technology, this application has the following advantages:

[0039] The tungsten carbide alloy material of the present application achieves stable emission stability of the material by combining the carbide layer design with rare earth element components, so that rare earth atoms migrate outward stably to replenish the rare earth element evaporated from the surface. Without adding thorium, the material can achieve the stable emission capability of a traditional thorium tungsten filament, solving the problem of poor stable emission capability of existing thorium-free tungsten filaments, and does not have the radioactive pollution problem of traditional thorium tungsten filaments.

[0040] Other features and benefits of the present application will be described in the following description, and in part will become apparent from the description or be understood through practice of the present application. The objectives and other benefits of the present application can be achieved and obtained through the structures particularly pointed out in the description, claims, and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, a brief introduction will be given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0042] FIG1 is a schematic diagram of a partial structure of a tungsten alloy filament provided in this application;

[0043] FIG2 is a schematic structural diagram of a cross section of a tungsten alloy filament provided in the present application;

[0044] FIG3 is a schematic diagram of the longitudinal cross-section of a tungsten alloy filament provided in the present application;

[0045] FIG4 is an enlarged view of point A in FIG2 ;

[0046] FIG5 is a metallographic image of Comparative Example 1 provided in this application at 44% FC;

[0047] FIG6 is a metallographic image of Comparative Example 1 provided in this application at 46% FC;

[0048] FIG7 is a metallographic image of Comparative Example 1 provided in this application at 48% FC;

[0049] FIG8 is a metallographic image of Comparative Example 1 provided in this application at 50% FC;

[0050] FIG9 is a metallographic image of Example 1 provided in this application at 48% FC;

[0051] FIG10 is a metallographic image of Example 1 provided in this application at 50% FC;

[0052] FIG11 is a metallographic image of Example 1 provided in this application at 52% FC;

[0053] FIG12 is a schematic diagram of the crystal structure of Comparative Example 1 provided in this application;

[0054] FIG13 is a schematic diagram of the crystal structure of Example 1 provided in this application;

[0055] FIG14 is a diagram illustrating the channel distribution in a cross section of Example 1 provided in this application;

[0056] FIG15 is a diagram illustrating the channel distribution in a longitudinal section of Example 1 provided in this application;

[0057] FIG16 is a diagram illustrating the channel distribution of the cross section of Comparative Example 1 provided in this application;

[0058] FIG17 is a diagram illustrating the channel distribution in the cross section of Comparative Example 4 provided in this application;

[0059] FIG18 is a diagram illustrating the channel distribution in a longitudinal section of Comparative Example 4 provided in this application;

[0060] FIG19 is a schematic diagram of the overall structure of the tungsten alloy filament provided by the present application;

[0061] FIG20 is a schematic diagram of a process flow for preparing a heating device from a tungsten alloy wire provided in the present application;

[0062] FIG21 is a graph showing the conversion relationship between FC% and degrees Celsius;

[0063] FIG22 is a partial structural schematic diagram of a cross section of a tungsten alloy filament provided in the present application.

[0064] Reference Signs: 100 Base body 200 Carbonized layer 210 Channel 220 Filament outer edge 211 First channel 212 Second channel DETAILED DESCRIPTION

[0065] In order to make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments; the technical features designed in different implementation modes of the present application described below can be combined with each other as long as they do not conflict with each other; based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0066] In the description of this application, it should be noted that all terms used in this application (including technical terms and scientific terms) have the same meaning as those commonly understood by ordinary technicians in the field to which this application belongs, and should not be understood as limiting this application; it should be further understood that the terms used in this application should be understood to have the same meaning as these terms in the context of this specification and the relevant field, and should not be understood in an idealized or overly formal sense, unless explicitly defined as such in this application.

[0067] This application provides a tungsten carbide alloy material, and its technical solution is as follows:

[0068] The tungsten carbide alloy material includes a substrate and a carbide layer attached to the outer surface of the substrate; the grain width of the carbide layer is 1.0μm to 15.0μm; the components of the substrate and the carbide layer both contain tungsten, carbon, oxygen and M element, and the M element is selected from one or more combinations of La, Y, Sc, Nd, Sm, Lu, Ce, Gd, Tb, Dy, Ho, Pr, Er, Tm, Yb, Eu, Hf, and Zr; wherein the components of the tungsten carbide alloy filament do not contain thorium.

[0069] 1. Preferred structural features and phase composition features of the carbonized layer 200:

[0070] (1) The M element in the carbonized layer exists in the form of oxide, and the carbon element exists in the form of carbide. The particle size of the M oxide particles is 10nm to 1000nm.

[0071] (2) As shown in Figures 1-4, a plurality of first channels 211 are distributed on the carbonized layer 200; at least some of the first channels 211 are distributed along the radial direction of the filament cross section; and / or, at least some of the first channels 211 point to the center of the filament cross section.

[0072] (3) As shown in FIG4 and FIG22, a plurality of channels 210 are distributed on the carbide layer 200, and the channels 210 include a first channel 211 and a plurality of second channels 212; at least a portion of the first channels 211 are distributed radially along the cross section of the tungsten alloy filament; and / or, at least a portion of the first channels 211 point to the center of the cross section of the tungsten alloy filament; and at least a portion of the second channels 212 are distributed circumferentially along the cross section of the tungsten alloy filament, wherein at least a portion of the second channels 212 are cross-arranged with the first channels 211, so that the cross section of the carbide layer 200 is block-shaped.

[0073] Specifically, the present application controls the structure of the carbonized layer 200: its grain size is controlled within a certain small range (grain width is 1.0μm to 15.0μm) to form a large number of first channels 211 and second channels 212, thereby forming a layered block structure. In combination with the rare earth components in the tungsten alloy filament, the carbonized layer 200 achieves a stable emission effect. The specific mechanism is as follows:

[0074] As shown in FIG22 , the second channel 212 divides the carbonized layer 200 into a radially stacked layer structure, and then the first channel 211 designed to intersect with the carbonized layer 200 divides the carbonized layer 200 into a block structure, so that the carbonized layer 200 forms a layer block. Compared with other structural distributions, for example, the first channel 211 divides the carbide layer 200 into a block structure, the second channel 212 divides the carbide layer 200 into a radially stacked layer structure, the second channel 212 and the first channel 211 are not designed to intersect, and the carbide layer 200 forms two clearly divided areas, one area is a block structure, and the other area is a layered structure. The grain control of the carbide layer 200 of the present application makes its cross section a layered block design, which has the advantages of: the radial or quasi-vertical distribution design of the first channel 211 is conducive to the outward migration of rare earth atoms of the M element, and the layered structure in the carbide layer 200 separated by the second channel 212 is where the oxides of M are distributed. The second channel 212 is combined with the first channel 211 (vertical channel 210) to form a layered block of the carbide layer 200, which can effectively control the migration speed of the oxides of M to the filament surface (i.e., the outer surface of the carbide layer 200), thereby improving the stable emission capability of the tungsten carbide alloy.

[0075] It should be noted that:

[0076] As shown in the filament structure of FIG1 , the cross section of the filament of FIG2 , and the longitudinal section of the filament of FIG3 , the terms "radially distributed along the cross section of the filament" and "at least a portion of the first channels 211 are directed toward the center of the cross section of the filament" herein refer to the radial distribution and the direction toward the center of the cross section: a first straight line is formed connecting the end point of the first channel 211 near the substrate 100 and the end point near the filament edge, and the angle between the first straight line and the tangent line at the intersection of the outer edge 220 of the filament is (60-90) degrees.

[0077] As shown in FIG22 , regarding the “circumferential distribution along the cross section of the tungsten alloy filament” herein, the circumferential distribution method is as follows: the endpoints 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 where the filament is located is (-45 to +45) degrees.

[0078] In the present application, the first channel 211 and the outer edge 220 of the filament (i.e., the outer edge of the carbonized layer 200) are distributed in a quasi-vertical and quasi-radial manner. The radial or quasi-vertical distribution design of the first channel 211 is beneficial to the outward migration of the M element atoms, but it does not mean that the first channel 211 is a straight structure, nor does it mean that the two end points of the first channel 211 need to pass through to the outer edge of the substrate 100 and the carbonized layer 200 (i.e., the outer edge 220 of the filament).

[0079] In the present application, the second channel 212 is distributed along the annular direction or is cross-arranged with the first channel 211, which does not mean that the second channel 212 is a standard arc structure, nor does it mean that the second channel 212 is continuously connected to pass through the entire outer ring. It can be a quasi-annular distribution composed of multiple sections of second channels 212 separated from each other, or a cross-distribution of multiple sections of second channels 212 separated from each other and the first channel 211, so that the carbonized layer 200 is divided into a layered structure stacked along the radial direction.

[0080] (3) The tungsten carbide alloy filament has a spiral structure, and the thickness of the carbide layer of at least one spiral turn reaches 30 μm to 90 μm, preferably 35 to 45 μm, 50 to 90 μm, for example 60 μm, 70 μm, 80 μm.

[0081] (4) The carbonized layer 200 includes W2C and WC; the weight ratio of W2C to WC is (60-100):(0-40).

[0082] 2. Preferred component characteristics for tungsten carbide alloy materials:

[0083] (1) In the matrix, the M element exists in the form of oxide, and the carbon element exists in the form of carbide or carbon element.

[0084] The present application adds one or more oxides of M and carbides or carbon elements. Since the oxides of M and carbides in the tungsten matrix react 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 that of lanthanum oxide particles. In this way, the migration and diffusion speed of lanthanum atoms in the tungsten matrix will be very fast, thereby improving the diffusion speed of M metal atoms. In summary, the present application combines the oxides of M with carbides or carbon elements. Compared with thoriated tungsten filaments, it can achieve the same or even higher electron emission capability as thoriated tungsten at a lower operating voltage (excitation temperature), and it is easier to ensure the balance between the loss and migration replenishment of rare earth atoms in the carbide layer of the filament, thereby ensuring the stability of the electron emission of the filament.

[0085] (2) The matrix of the tungsten carbide alloy filament comprises the following components: 0.0005-0.3 wt% carbon, 0.25-2.6 wt% M, 0.05-0.5 wt% oxygen, and the balance is tungsten and unavoidable impurities. Preferably, the matrix of the tungsten carbide alloy filament comprises the following components: 0.0005-0.3 wt% carbon, 0.25-2.6 wt% M, 0.05-0.5 wt% oxygen, and the balance is tungsten and unavoidable impurities.

[0086] The M element can be 1.28-2.6 wt %. A tungsten alloy filament made with this composition ratio is preferably used in microwave ovens with power <800W. The M element can be 0.25-1.28 wt %. A tungsten alloy filament made with this composition ratio is preferably used in microwave ovens with power >800W. Furthermore, the M element can be 0.25-0.86 wt %. A tungsten alloy filament made with this composition ratio is preferably used in microwave ovens with power >1000W.

[0087] Preferably, M is present in the tungsten alloy material in the form of an oxide, wherein the oxide of M is selected from one or more combinations 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 is present in the tungsten alloy material in the form of a carbide or a single carbon element, wherein the carbide is selected from one or more combinations of lanthanum carbide, zirconium carbide, yttrium carbide, hafnium carbide, and tungsten carbide. For example, the oxide of M can be selected from lanthanum oxide, or a combination of lanthanum oxide and yttrium oxide, or a combination of lanthanum oxide and zirconium oxide, or a combination of lanthanum oxide and scandium oxide, or a combination of lanthanum oxide and hafnium oxide, etc.

[0088] Preferably, the matrix of the tungsten alloy material further comprises T, where T is a solid solution metal element or a dispersed metal element, and T is selected from at least one of K, Re, Mo, Fe, and Co. Further preferably, the mass content of Re is less than 1000 ppm.

[0089] It should be noted that:

[0090] “La, Y, Sc, Nd, Sm, Lu, Ce, Gd, Tb, Dy, Ho, Pr, Er, Tm, Yb, Eu, Hf, Zr” in the text are element symbols in the periodic table, representing the metal elements lanthanum, yttrium, scandium, neodymium, samarium, lutetium, cerium, gadolinium, terbium, dysprosium, holmium, praseodymium, erbium, thulium, ytterbium, europium, hafnium, and zirconium in the periodic table respectively; “K, Re, Mo, Fe, Co” in the text are element symbols in the periodic table, representing the metal elements potassium, rhenium, molybdenum, iron, and cobalt in the periodic table respectively; W is the symbol for tungsten in the periodic table; C is the symbol for carbon in the periodic table; in addition, “M” and “T” are only reference symbols and do not represent elements in the periodic table and are used for reference only.

[0091] 3. The wire diameter of tungsten carbide alloy filament can reach 800μm and below:

[0092] In the pressure processing process, the tungsten alloy material provided by the present application has good processing performance and can be processed into wires with fine wire diameter specifications (i.e., fine wire diameter tungsten alloy wires), and the wire diameter tolerance can be controlled within a very small range.

[0093] Furthermore, the wire diameter can be 600 μm or less, 550 μm or less, or even 500 μm or less. The wire diameter can be 450-550 μm, such as 470 μm, 490 μm, 500 μm, 520 μm, etc., or 700-800 μm, such as 750 μm, 760 μm, 780 μm, etc.

[0094] 4. Tungsten carbide alloy filament has a spiral structure in actual use. The preferred structural features of the spiral structure of the tungsten alloy filament are as follows:

[0095] 4.1 Turn number control: As shown in the structural schematic diagram of the tungsten alloy filament in FIG19 , the number of turns of the filament is preferably (9.5 to 13) turns, with a control tolerance of ±0.125 and a statistical CPK>1.33.

[0096] The number of turns of the filament is between 9.50 and 13.00 turns. The preferred number of turns can be between 9.70 and 10.70 turns, such as 9.90 turns, 10.00 turns, 10.28 turns, 10.5 turns, etc. It can also be between 10.70 and 11.70 turns, such as 11.00 turns, 11.20 turns, 11.5 turns, etc. It can also be between 11.80 and 13.00 turns, such as 12.00 turns, 12.20 turns, 12.5 turns, etc.

[0097] 4.2 Pitch Uniformity: The tolerance for the tungsten alloy filament pitch L1 is ±0.02, and the statistical CPK is >1.33. The tungsten alloy filament pitch L1 is shown in Figure 19, representing the distance between two adjacent spiral turns. During implementation, those skilled in the art may use specialized winding equipment to achieve uniform filament pitch, enabling more stable electron emission from the heating device.

[0098] It should be noted that the number of filament turns is related to the filament length L and the pitch L1, and the filament length L=(number of filament turns-1)*L1.

[0099] 4.3 Pitch size: The pitch L1 of the tungsten alloy filament is 0.800-1.800 mm. The preferred pitch L1 can be 1.000-1.150 mm, such as 1.018 mm, 1.044 mm, 1.135 mm, etc., or 1.230-1.330 mm, such as 1.240 mm, 1.290 mm, etc., or 1.400-1.600 mm, such as 1.470 mm, 1.500 mm, etc.

[0100] 3.4 Length: The length L of the filament is between 10.00 and 16.00 mm. The preferred length L can be between 10.50 and 12.00 mm, such as 11.00 mm, 11.20 mm, 11.70 mm, etc., or can be between 12.50 and 14.00 mm, such as 12.83 mm, 13.40 mm, 13.55 mm, etc.

[0101] The outer diameter Φ1 of the filament is 3.00-6.00 mm, preferably 3.50-4.50 mm, such as 3.70 mm, 3.80 mm, 3.90 mm, 3.92 mm, 4.00 mm, etc., or 5.00-6.00 mm, such as 5.20 mm, 5.48 mm, 5.60 mm, etc.

[0102] Among them, this application also provides the following preferred embodiments for preparing tungsten alloy wire (finished product before carbonization, steps 1-6), carbide tungsten alloy filament (steps 1-9), and prepare a heating device containing tungsten alloy filament (steps 1-12):

[0103] It includes the following steps:

[0104] Step 1: preparing a finished powder raw material through a doping process, a reduction process, and a powder making process in sequence; wherein the doping process is solid-liquid doping or solid-solid doping;

[0105] Step 2, powder pressing: using isostatic pressing to press powders of different particle sizes into green compacts, and pre-sintering the green compacts at low temperature in a hydrogen atmosphere to increase the green compact strength; wherein the powders are pressed at a pressure of 160-240 MPa into green compacts weighing 1.5-5.0 kg;

[0106] Step 3: High temperature sintering: Use high temperature sintering to obtain a density of 17.5-18.3 g / cm 3 Sintering the billet to obtain the tungsten alloy material in billet form;

[0107] The heating curve of the high temperature sintering method is:

[0108] Heating from room temperature to A1, heating time H1 is (5-8) h, A1 is (950-1250) °C;

[0109] For example, H1 is (5-7)h, (7-8)h, etc., and another example is 6h, 7.5h, etc.; A1 is (950-1050)℃, (1050-1250)℃, etc., and another example is 1000℃, 1100℃, etc.;

[0110] Keep warm at A1 for H2 hours, H2 is (1 to 3);

[0111] For example, H2 is (1-2)h, (2-3)h, etc., and another example is 1.5h, 2.5h, etc.;

[0112] From A1 to A2, the heating time is H3, H3 is (1.5-2.5) h, and A2 is (1300-1500) °C;

[0113] For example, H3 is (1.5-2.0)h, (2.0-2.5)h, etc., and another example is 1.5h, 2.0h, 2.4h, etc.; A2 is (1300-1400X)°C, (1400-1500)°C, etc., and another example is 1350°C, 150°C, etc.;

[0114] Keep warm at A2 for H4 hours, H4 is (2.5~4.5);

[0115] For example, H4 is (2.5-3.0)h, (3.0-4.0)h, etc., and another example is 2.8h, 3.5h, etc.;

[0116] From A2 to A3, the heating time is H5, H5 is (1-3) h, and A3 is (1700-1900) °C;

[0117] For example, H5 is (1-2)h, (2-3)h, etc., and another example is 1.6h, 2.0h, 2.5h, etc.; A3 is (1700-1800)℃, (1800-1900)℃, etc., and another example is 1750℃, 1850℃, etc.;

[0118] Keep warm at A3 for H6 hours, H6 is (1~3);

[0119] For example, H6 is (1-2)h, (2-3)h, etc., and another example is 1.5h, 2.5h, etc.;

[0120] From A3 to A4, the heating time is H7, H7 is (1-3)h, A4 is (2050-2250)℃;

[0121] For example, H7 is (1-2)h, (2-3)h, etc., and another example is 1.5h, 2.5h, etc.; A4 is (2050-2150)℃, (2150-2250)℃, etc., and another example is 2100℃, 2200℃, etc.;

[0122] Keep warm at A4 for H8 hours, H8 is (5-10);

[0123] For example, H8 is (5-7)h, (7-10)h, etc., and another example is 6h, 8h, etc.;

[0124] It is obtained by natural cooling from A4.

[0125] Step 4: Pressure processing:

[0126] 4.1 In the pressure processing step, the tungsten alloy sintered billet obtained after sintering is refined into an intermediate specification wire with a diameter of 1.5 to 3.5 mm;

[0127] 4.2 Then, the intermediate specification wire is subjected to oxidation annealing at (1200-1500)°C at an annealing speed of (3-10) m / min;

[0128] For example, the annealing speed is (3-7) m / min, (7-10) m / min, etc., and another example is 3 m / min, 5 m / min, 7 m / min, etc.; the oxidation annealing temperature is (1200-1350)°C, (1350-1500)°C, etc., and another example is 1250°C, 1400°C, etc.;

[0129] 4.3 After oxidation annealing, continue to process the intermediate specification wire to the required wire diameter specification to obtain tungsten alloy wire;

[0130] Among them, multi-pass rotary forging and drawing are used for diameter reduction processing; the oxidation annealing process is carried out in the oxidation annealing equipment, and the annealing speed refers to the speed at which the wire passes through the annealing tank, which indicates the length of the wire passing through the annealing tank per unit time.

[0131] Step 5: Cleaning the white wire: Use electrolytic cleaning to clean the black wire into tungsten alloy white wire that can be processed into microwave heating device filament;

[0132] Step 6: Winding: Wind the white wire into a spring-shaped filament structure for the heating device to obtain tungsten alloy wire;

[0133] Step 7, cathode assembly: assemble the spring-shaped filament structure with components, ceramics, lead pieces and other parts into a cathode structure through heat treatment;

[0134] Step 8, welding: weld the filament structure in the cathode structure to the component end cap;

[0135] Step 9: Carbonization: Carbonize the welded cathode structure to obtain a tungsten carbide alloy filament.

[0136] Step 10, white ball assembly: Assemble the cathode structure, anode cylinder, antenna end cap and other components together;

[0137] Step 11: exhaust the white ball, evacuate the air, and perform high-temperature aging to complete the production of the black ball and activate its emission performance;

[0138] Step 12: Assemble the black ball, heat sink, magnet, tube shell, etc. to finally obtain a heating device component containing the above-mentioned tungsten carbide alloy filament, and put it into a microwave oven for use.

[0139] 1. The preferred structural features of the tungsten alloy wire before carburization (i.e., the wire obtained after pressure processing) are as follows:

[0140] 1.1 Characteristics of the initial recrystallization temperature:

[0141] The initial recrystallization temperature of the tungsten alloy wire provided by the present application is higher than that of the thoriated tungsten wire, which is 48% Fc to 56% Fc in the present application, while the thoriated tungsten wire is around 46% FC (2020°C).

[0142] The average size of the 80% Fc recrystallized grains of the tungsten alloy wire provided in the present application is finer than that of the thoriated tungsten wire. The average size of the 80% Fc recrystallized grains of the tungsten alloy wire provided in the present application is (1-15) μm, and the average size of the 80% Fc recrystallized grains of the thoriated tungsten filament is (16-150) μm.

[0143] The above-mentioned characteristics of high initial recrystallization temperature and small average size of 80% Fc recrystallized grains make the tungsten matrix structure of the filament produced by the tungsten alloy wire of the present application finer than that of thorium tungsten filament after carburization in the magnetron, thereby making the grain width of the carburized layer of the tungsten alloy filament finer, so that the grain width of the carburized layer can be controlled within the desired range;

[0144] The process of preparing tungsten alloy wire into tungsten carbide alloy involves a carbonization step at a temperature of 2000-2500°C. The original thoriated tungsten filament carbonizes at this temperature (analysis shows that its initial recrystallization temperature is too low), causing recrystallization in the grain structure and coarse grains. This makes the carbonized filament brittle and has poor seismic performance. This makes it very easy for the filament to break during magnetron assembly, transportation, and subsequent microwave oven use. Compared with thoriated tungsten filaments, the filament material selected in this application has a higher initial recrystallization temperature than the original thoriated tungsten filament, and the average size of the 80% Fc recrystallized grains is smaller than that of the original thoriated tungsten filament. After carbonization, the tungsten alloy filament of this application still has a fine-grained structure, making it less brittle than traditional thoriated tungsten filament materials. The fine-grained tungsten alloy filament has better seismic performance than thoriated tungsten filaments. The filament breakage rate of the magnetron produced in this application is much lower than that of traditional thoriated tungsten filaments.

[0145] Optionally, the initial recrystallization temperature of the tungsten alloy wire may be 48% to 52% FC, such as 48% FC, 50% FC, 52% FC, and the like.

[0146] Optionally, the average size of 80% Fc recrystallized grains of the tungsten alloy wire can be (1-8) μm, (8-12)% μm, (12-15) μm, etc., for example, 4.0 μm, 8.5 μm, 13 μm, etc.

[0147] 1.2 The average size characteristics of the oxide particles in the tungsten alloy wire: The average size of the oxide particles in the tungsten alloy wire is (100-500) nm

[0148] The average size of the oxide particles of the tungsten alloy wire of this application is between 100 and 500 nm. The size of the tungsten alloy wire oxide particles determines the size of the oxide particles of the filament after carbonization. If the wire oxide particles are too coarse relative to the range specified in this application, resulting in coarse particles of the tungsten alloy filament after carbonization, it will be more difficult for the M oxide particles to migrate to the filament surface during the use of the magnetron. This will make it easier to disrupt the balance between rare earth element loss and replenishment on the filament surface, making the magnetron electron emission more unstable.

[0149] Optionally, the average size of the oxide particles may also be (100-300) nm, (300-500) nm, etc., for example, 200 nm, 300 nm, 450 nm, etc.

[0150] 1.3 For the above tungsten alloy wire crack detection characteristics:

[0151] The number of crack points detected by flaw detection of the tungsten alloy wire is less than 5 (per 100 meters). Further, the number of crack points detected by flaw detection of the tungsten alloy wire can be less than 2 per 100 meters, such as 0 per 100 meters, 0.5 per 100 meters, 1 per 100 meters, and the like.

[0152] Tungsten alloy wire has fewer crack points during inspection, a high filament yield rate, and is not prone to wire breakage.

[0153] 2. Important control points for the preferred embodiment of the method for preparing tungsten alloy wire before carburization:

[0154] The present application uses the preferred embodiment of the preparation method to obtain a tungsten alloy wire before carbide having the aforementioned characteristics of the initial recrystallization temperature and the average size of the oxide particles. Through the carbonization treatment of the tungsten alloy wire, a tungsten carbide alloy filament having the aforementioned characteristics of the carbide layer grain width, carbide layer oxide particle size, etc. can be obtained. The specific process control points for obtaining the tungsten alloy wire before carbide are as follows:

[0155] (1) Oxidation annealing treatment of intermediate specification products:

[0156] The present application provides a specific treatment method for the oxidation annealing in the above-mentioned pressure processing step to control the initial recrystallization temperature of the tungsten alloy within the above-mentioned required range (48%Fc to 56%Fc): a stress relief oxidation annealing at a temperature of 1200-1500°C is added at the middle of the wire with a specification of 1.5-3.5 mm, so that the initial recrystallization temperature of the tungsten alloy wire is effectively controlled within 48%Fc to 56%Fc; in this preparation process, if the oxidation annealing process is removed, the initial recrystallization temperature of the tungsten alloy wire will exceed 56%Fc. Excessively high initial recrystallization temperature will be detrimental to the electron emission performance of the tungsten carbide alloy filament under magnetron operating conditions.

[0157] (2) By controlling the time from A1 to A2 and the sintering time at A2 (1300-1500°C) during the sintering process:

[0158] During the high-temperature sintering stage of the tungsten billet, the present application provides a sintering process. By controlling the time for heating from A1 to A2 and the sintering time at A2 (1300-1500°C) during the sintering process, the sintering neck of the tungsten billet grows rapidly, closing the pores and preventing the oxide particles in the pores from being squeezed into another pore through the unclosed connecting channel during the shrinkage of the billet sintering cavity. While ensuring the density of the sintered billet, the size of the oxide particles in the sintered billet is controlled, thereby controlling the oxide size of the tungsten alloy wire or the filament after carbonization.

[0159] Among them, the oxide particle size distribution range of the tungsten alloy sintered billet obtained by the above sintering process is 100-2000nm, and the average size of the oxide particles is 600-1000nm. The average size of the oxide particles of the tungsten alloy wire is (100-500)nm; optionally, the average size of the oxide particles can also be (100-300)nm, (300-500)nm, etc., for example, 200nm, 300nm, 450nm, etc.

[0160] Without the aforementioned sintering process, the oxide particle size distribution of tungsten alloy sintered billets ranges from 400 to 5000 nm, with an average oxide particle size of 1200 to 2000 nm. The average oxide particle size of tungsten alloy wires after further refinement is also relatively coarse (approximately 500-900 nm).

[0161] The mechanism by which the sintering process affects the oxide size of the billet, tungsten alloy wire, and carbonized filament, as well as the effect of the oxide size of the tungsten alloy wire and carbonized filament on filament performance, is as follows: The reason for controlling the oxide particle size within a smaller range is that the oxide particle size of the billet directly determines the oxide size of the tungsten alloy wire or carbonized filament. Coarser oxide particles in the wire make it more difficult for these particles to migrate to the filament surface during magnetron operation. This makes it easier to disrupt the balance between rare earth element loss and replenishment on the filament surface, resulting in less stable electron emission from the magnetron.

[0162] Adjustment of the sintering process affects the speed of sintered neck growth and pore closure in tungsten billets. The sintering process provided can reduce the possibility of oxide particle aggregation, thereby reducing the oxide particle size of the sintered billet. The specific principle of the high temperature sintering process is explained as follows:

[0163] An isostatically pressed green compact is a dense accumulation of powder with a porosity of approximately 35-45%. These pores can be simply imagined as cavities with multiple interconnected channels, with oxide particles evenly distributed on the inner surface of the cavities. During high-temperature sintering, the bounded tungsten particles form "sintering necks." As the sintering temperature increases, these necks continue to grow and block the channels connecting the cavities, resulting in isolated cavities. These isolated cavities gradually become rounded, reducing their internal surface area. This in turn causes similarly sized small oxide particles to aggregate into larger particles. As high-temperature sintering proceeds, the cavities further shrink due to diffusion, forcing the oxide particles distributed on the inner surface of the cavities to aggregate further, forming one or more larger oxide particles.

[0164] Some smaller holes merge with adjacent large holes due to diffusion, or shrink before the connecting hole channels are closed. The oxide particles in these small holes will be pushed to the adjacent unclosed holes, making the oxide in the unclosed holes more than in other places, and then causing the oxide particle size to be coarser than in other places.

[0165] The present application also provides the following examples and comparative examples:

[0166] The weight formula of the raw material components and the element ratio of the prepared filament materials of the examples and comparative examples provided in this application are shown in Table 1 below:

[0167] Table 1

[0168] Specifically, according to the formulation in Table 1, the raw material components in the examples and comparative examples were used to prepare tungsten alloy filaments and heating devices according to the following preparation method:

[0169] Example 1

[0170] 1. According to the formula in Table 1, add 5L of deionized water to a certain amount of lanthanum nitrate solution. Stir for 10 minutes to fully dissolve it. Then add 1L of ammonia NH3·H2O solution and stir to neutralize it. Spray the prepared mixed solution evenly onto the blue tungsten placed in the doping pot and stir. The volume ratio of lanthanum nitrate solution to ammonia NH3·H2O solution is 5:1.

[0171] 2. Evacuate the doping pot and heat it with water (heating temperature 80°C, vacuum degree -0.025MPa), stirring while heating;

[0172] 3. Under vacuum conditions, the powder is dried by steam heating, with a steam pressure of 0.1-0.3 MPa and a vacuum degree in the pot of ≤-0.02 MPa, ultimately obtaining tungsten-lanthanum doped powder with uniform doping and low impurity content;

[0173] 4. Reduce the tungsten-lanthanum doped powder into tungsten-lanthanum powder of appropriate particle size in a reduction furnace with four temperature zones of 650°C, 750°C, 850°C and 900°C;

[0174] 5. The obtained tungsten-lanthanum powder and tungsten carbide are placed in a high-speed powder mixer for solid-solid mixing for 2 hours, and then sieved to obtain a mixed tungsten-lanthanum alloy powder;

[0175] 6. Use isostatic pressing to press the powder with a particle size of 1.5 μm into a green compact weighing 3.0 kg at a pressure of 180 MPa. The green compact is then pre-sintered at a low temperature in a hydrogen atmosphere to increase its strength.

[0176] 7. Use high temperature sintering method, and adopt the method of rapid heating and extended holding time at the intermediate holding point: the sintering temperature curve is:

[0177] Heating from room temperature to A1, heating time H1 is 6h, A1 is 1100℃; keeping at A1 for H2 hours, H2 is 2; heating from A1 to A2, heating time H3, H3 is 2h, A2 is 1400℃; keeping at A2 for H4 hours, H4 is 3.5; heating from A2 to A3, heating time H5, H5 is 2h, A3 is 1800℃; keeping at A3 for H6 hours, H6 is 2; heating from A3 to A4, heating time H7, H7 is 2h, A4 is 2100℃; keeping at A4 for H8 hours, H8 is 6; cooling naturally from A4, the product is obtained. Among them, by controlling the time of medium frequency sintering to control the closing and shrinking speed of the billet pores, the oxide particle size <2.0μm and the density 18.0g / cm 3 sintered billets.

[0178] 8. The 17mm diameter sintered billet was processed into 2.0mm wire using multiple passes of rotary forging and drawing. The wire was then oxidized and annealed on an oxidizing annealing device at 1400°C and a speed of 5m / min. After annealing, the wire was further processed into 0.52mm±0.005mm diameter rare earth tungsten alloy black wire.

[0179] Among them, the multi-pass rotary forging and drawing processing adopts the conventional drawing process, and the process parameters are multi-pass rotary forging to a wire diameter specification of 3.7mm, then drawing to 2.0mm, and then further processing to 0.52±0.005mm tungsten lanthanum alloy black wire after annealing.

[0180] 9. Use electrolytic cleaning to clean the 0.52mm black wire into 0.50mm±0.005mm tungsten-lanthanum alloy white wire that can be processed into microwave oven heating device filament;

[0181] 10. Wind 0.50mm tungsten-lanthanum alloy white wire into a spring-shaped cathode filament for the heating device, with 10 turns and a pitch of 1.29±0.03mm;

[0182] 11. Assemble the filament, components, ceramics, lead pieces and other parts into the cathode structure through heat treatment at a temperature of 600°C.

[0183] 12. Weld the filament in the cathode structure to the end cap of the assembly.

[0184] 13. Place the cathode structure in a carbonization tank for carbonization. After exhausting, introduce carbon-containing hydrocarbon gas (specifically methane) and apply direct current of a certain current value (current value is 16A) to the cathode for heating, so that the filament is carbonized in the hydrocarbon gas.

[0185] 14. White ball assembly: Assemble the cathode structure, anode cylinder, antenna end cap and other components together.

[0186] 15. The white ball is evacuated and aged at high temperature to complete the production of the black ball and activate its launch performance.

[0187] 16. Assemble the black ball, heat sink, magnet, tube shell, etc. to finally obtain the heating device component containing the above-mentioned filament, and install it in a microwave oven for use.

[0188] Example 2

[0189] 1. According to the formula in Table 1, add 5L of deionized water to a certain amount of lanthanum nitrate-yttrium nitrate solution. Stir for 10 minutes to fully dissolve. Then add 1L of ammonia NH3·H2O solution and stir to neutralize. Spray the prepared mixed solution evenly onto the blue tungsten placed in the doping pot and stir. The volume ratio of lanthanum nitrate-yttrium nitrate solution to ammonia NH3·H2O solution is 5:1.

[0190] 2. Evacuate the doping pot and heat it with water (heating temperature 80°C, vacuum degree -0.025MPa), stirring while heating;

[0191] 3. Under vacuum conditions, the powder is dried by steam heating, with a steam pressure of 0.1-0.3 MPa and a vacuum degree in the pot of ≤-0.02 MPa, ultimately obtaining tungsten, lanthanum, and yttrium doped powder with uniform doping and low impurity content;

[0192] 4. Reduce the tungsten lanthanum yttrium doped powder into tungsten lanthanum yttrium powder of appropriate particle size in a reduction furnace with four temperature zones of 650℃, 750℃, 850℃ and 900℃;

[0193] 5. The obtained tungsten lanthanum yttrium powder and tungsten carbide are placed in a high-speed powder mixer for solid-solid mixing for 2 hours, and then sieved to obtain a mixed tungsten lanthanum yttrium alloy powder;

[0194] 6. Use isostatic pressing to press the powder with a particle size of 1.5 μm into a green compact weighing 3.0 kg at a pressure of 180 MPa. The green compact is then pre-sintered at a low temperature in a hydrogen atmosphere to increase its strength.

[0195] 7. Use high temperature sintering method, and adopt the method of rapid heating and extended holding time at the intermediate holding point: the sintering temperature curve is:

[0196] Heat up from room temperature to A1, heating time H1 is 5h, A1 is 950℃; keep warm at A1 for H2 hours, H2 is 3; heat up from A1 to A2, heating time H3, H3 is 1.5h, A2 is 1300℃; keep warm at A2 for H4 hours, H4 is 4.5; heat up from A2 to A3, heating time H5, H5 is 1h, A3 is 1700℃; keep warm at A3 for H6 hours, H6 is 3; heat up from A3 to A4, heating time H7, H7 is 1h, A4 is 2050℃; keep warm at A4 for H8 hours, H8 is 10; cool naturally from A4, and you're done.

[0197] 8. The 17 mm diameter sintered billet was processed into a 2.0 mm wire using multiple swaging and drawing processes. The wire was then subjected to oxidation annealing on an oxidation annealing apparatus at a temperature of 1200°C and an annealing speed of 3 m / min. After annealing, the wire was further processed into a 0.52 mm ± 0.005 mm diameter tungsten lanthanum yttrium alloy black wire. Other conditions were the same as in Example 1.

[0198] 9. Use electrolytic cleaning to clean the 0.52mm black wire into 0.50mm±0.005mm tungsten lanthanum yttrium alloy white wire that can be processed into microwave oven heating device filament;

[0199] 10. Wind 0.50mm tungsten-lanthanum-yttrium alloy white wire into a spring-shaped cathode filament for the heating device; the number of turns is 10, and the pitch is 1.29±0.03mm;

[0200] 11. Assemble the filament, components, ceramics, lead pieces and other parts into the cathode structure through heat treatment at a temperature of 600°C.

[0201] 12. Weld the filament in the cathode structure to the end cap of the assembly.

[0202] 13. Place the cathode structure in a carbonization tank for carbonization. After exhausting, introduce carbon-containing hydrocarbon gas (specifically methane) and apply direct current of a certain current value (current value is 16A) to the cathode for heating, so that the filament is carbonized in the hydrocarbon gas.

[0203] 14. White ball assembly: Assemble the cathode structure, anode cylinder, antenna end cap and other components together.

[0204] 15. The white ball is evacuated and aged at high temperature to complete the production of the black ball and activate its launch performance.

[0205] 16. Assemble the black ball, heat sink, magnet, tube shell, etc. to finally obtain the heating device component containing the above-mentioned filament, and install it in a microwave oven for use.

[0206] Example 3

[0207] 1. According to the formula in Table 1, add 5L of deionized water to a certain amount of lanthanum nitrate-zirconium nitrate solution and stir for 10 minutes to fully dissolve. Then add 1L of ammonia NH3·H2O solution and stir to neutralize. Spray the prepared mixed solution evenly onto the blue tungsten in the doping pot and stir. The ratio of lanthanum nitrate-zirconium nitrate solution to ammonia NH3·H2O solution is 5:1.

[0208] 2. Evacuate the doping pot and heat it with water (heating temperature 80°C, vacuum degree -0.025MPa), stirring while heating;

[0209] 3. Under vacuum conditions, the powder is dried by steam heating, with a steam pressure of 0.1-0.3 MPa and a vacuum degree in the pot of ≤-0.02 MPa, ultimately obtaining tungsten, lanthanum, and zirconium doped powder with uniform doping and low impurity content;

[0210] 4. Reduce the tungsten lanthanum zirconium doped powder into tungsten lanthanum zirconium powder of appropriate particle size in a reduction furnace with four temperature zones of 650℃, 750℃, 850℃ and 900℃;

[0211] 5. The obtained tungsten lanthanum zirconium powder and tungsten carbide are placed in a high-speed powder mixer for solid-solid mixing for 2 hours, and then sieved to obtain a mixed tungsten lanthanum zirconium alloy powder;

[0212] 6. Use isostatic pressing to press the powder with a particle size of 1.5 μm into a green compact weighing 3.0 kg at a pressure of 180 MPa. The green compact is then pre-sintered at a low temperature in a hydrogen atmosphere to increase its strength.

[0213] 7. Use high temperature sintering method, and adopt the method of rapid heating and extended holding time at the intermediate holding point: the sintering temperature curve is:

[0214] Heating from room temperature to A1, heating time H1 is 8h, A1 is 1250℃; keeping at A1 for H2 hours, H2 is 1; heating from A1 to A2, heating time H3, H3 is 2.5h, A2 is 1500℃;

[0215] Keep warm at A2 for H4 hours, H4 is 2.5; heat up from A2 to A3, the heating time is H5, H5 is 3h, A3 is 1900℃; keep warm at A3 for H6 hours, H6 is 1; heat up from A3 to A4, the heating time is H7, H7 is 3h, A4 is 2250℃; keep warm at A4 for H8 hours, H8 is 5; cool naturally from A4, and you have it.

[0216] 8. Using multiple passes of rotary forging and drawing, the 17mm diameter sintered billet was processed into 2.0mm gauge wire. The wire was then oxidized and annealed on an oxidizing annealing device at 1500°C and a speed of 10 m / min. After annealing, the wire was further processed into 0.52mm±0.005mm diameter tungsten-lanthanum-zirconium alloy black wire.

[0217] 9. The 0.52 mm black wire was cleaned by electrolytic cleaning to become a 0.50 mm ± 0.005 mm tungsten lanthanum zirconium alloy white wire that can be processed into a microwave oven heating device filament; other conditions were the same as in Example 1.

[0218] 10. Wind 0.50mm tungsten lanthanum zirconium alloy white wire into a spring-shaped cathode filament for the heating device; the number of turns is 10, and the pitch is 1.29±0.03mm;

[0219] 11. Assemble the filament, components, ceramics, lead pieces and other parts into the cathode structure through heat treatment at a temperature of 600°C.

[0220] 12. Weld the filament in the cathode structure to the end cap of the assembly.

[0221] 13. Place the cathode structure in a carbonization tank for carbonization. After exhausting, introduce carbon-containing hydrocarbon gas (specifically methane) and apply direct current of a certain current value (current value is 16A) to the cathode for heating, so that the filament is carbonized in the hydrocarbon gas.

[0222] 14. White ball assembly: Assemble the cathode structure, anode cylinder, antenna end cap and other components together.

[0223] 15. The white ball is evacuated and aged at high temperature to complete the production of the black ball and activate its launch performance.

[0224] 16. Assemble the black ball, heat sink, magnet, tube shell, etc. to finally obtain the heating device component containing the above-mentioned filament, and install it in a microwave oven for use.

[0225] Example 4

[0226] 1. According to the formula in Table 1, add 5L of deionized water to a certain amount of lanthanum nitrate-scandium nitrate solution. Stir for 10 minutes to fully dissolve. Then add 1L of ammonia NH3·H2O solution and stir to neutralize. Spray the prepared mixed solution evenly onto the blue tungsten placed in the doping pot and stir. The ratio of lanthanum nitrate-scandium nitrate solution to ammonia NH3·H2O solution is 5:1.

[0227] 2. Evacuate the doping pot and heat it with water (heating temperature 80°C, vacuum degree -0.025MPa), stirring while heating;

[0228] 3. Dry the powder by steam heating under vacuum conditions, with a steam pressure of 0.1-0.3 MPa and a vacuum degree in the pot of ≤-0.02 MPa, to obtain tungsten, lanthanum, and scandium doped powder with uniform doping and low impurity content.

[0229] 4. In a reduction furnace with four temperature zones of 650°C, 750°C, 850°C and 900°C, the tungsten lanthanum scandium doped powder is reduced into tungsten lanthanum scandium powder of appropriate particle size;

[0230] 5. The obtained tungsten lanthanum scandium powder and tungsten carbide are placed in a high-speed powder mixer for solid-solid mixing for 2 hours, and then sieved to obtain a mixed tungsten lanthanum scandium alloy powder;

[0231] 6. Use isostatic pressing to press the powder with a particle size of 1.5 μm into a green compact weighing 3.0 kg at a pressure of 180 MPa. The green compact is then pre-sintered at a low temperature in a hydrogen atmosphere to increase its strength.

[0232] 7. Using high temperature sintering method, the oxide particles with particle size <2.0μm and density 18.0g / cm 3 wherein the process and conditions of this step are consistent with those of Example 1;

[0233] 8. Using multiple passes of rotary forging and drawing, the 17 mm diameter sintered billet was processed into a 0.52 mm ± 0.005 mm diameter tungsten lanthanum scandium alloy black wire; wherein the process and conditions of this step are the same as those in Example 1;

[0234] 9. Use electrolytic cleaning to clean the 0.52mm black wire into 0.50mm±0.005mm tungsten lanthanum scandium alloy white wire that can be processed into microwave oven heating device filament;

[0235] 10. Wind 0.50mm tungsten-lanthanum-scandium alloy white wire into a spring-shaped cathode filament for the heating device; the number of turns is 10, and the pitch is 1.29±0.03mm;

[0236] 11. Assemble the filament, components, ceramics, lead pieces and other parts into the cathode structure through heat treatment at a temperature of 600°C.

[0237] 12. Weld the filament in the cathode structure to the end cap of the assembly.

[0238] 13. Place the cathode structure in a carbonization tank for carbonization. After exhausting, introduce carbon-containing hydrocarbon gas (specifically methane) and apply direct current of a certain current value (current value is 16A) to the cathode for heating, so that the filament is carbonized in the hydrocarbon gas.

[0239] 14. White ball assembly: Assemble the cathode structure, anode cylinder, antenna end cap and other components together.

[0240] 15. The white ball is evacuated and aged at high temperature to complete the production of the black ball and activate its launch performance.

[0241] 16. Assemble the black ball, heat sink, magnet, tube shell, etc. to finally obtain the heating device component containing the above-mentioned filament, and install it in a microwave oven for use.

[0242] Example 5

[0243] 1. According to the formula in Table 1, add 5L of deionized water to a certain amount of lanthanum nitrate-hafnium nitrate solution and stir for 10 minutes to fully dissolve. Then, add 1L of ammonia NH3·H2O solution and stir to neutralize. Spray the prepared mixed solution evenly onto the blue tungsten in the doping pot and stir. The ratio of lanthanum nitrate-hafnium nitrate solution to ammonia NH3·H2O solution is 5:1.

[0244] 2. Evacuate the doping pot and heat it with water (heating temperature 80°C, vacuum degree -0.025MPa), stirring while heating;

[0245] 3. Dry the powder by steam heating under vacuum conditions, with a steam pressure of 0.1-0.3 MPa and a vacuum degree in the pot of ≤-0.02 MPa, to obtain tungsten, lanthanum, and hafnium doped powder with uniform doping and low impurity content.

[0246] 4. In a reduction furnace with four temperature zones of 650°C, 750°C, 850°C and 900°C, the tungsten lanthanum and hafnium doped powder is reduced into tungsten lanthanum and hafnium powder with a suitable particle size and a content of 0.3% La2O3 + 0.2% HfO2;

[0247] 5. The obtained tungsten lanthanum hafnium powder and tungsten carbide are placed in a high-speed powder mixer for solid-solid mixing for 2 hours, and sieved to obtain a mixed tungsten lanthanum hafnium alloy powder with a content of 0.3% La2O3+0.2% HfO2+0.5% WC;

[0248] 6. Use isostatic pressing to press the powder with a particle size of 1.5 μm into a green compact weighing 3.0 kg at a pressure of 180 MPa. The green compact is then pre-sintered at a low temperature in a hydrogen atmosphere to increase its strength.

[0249] 7. Use high temperature sintering to obtain oxide particles with a particle size of <2.0μm and a density of 18.0g / cm 3 wherein the process and conditions of this step are consistent with those of Example 1;

[0250] 8. Using multiple passes of rotary forging and drawing, the 17 mm diameter sintered billet was processed into a 0.52 mm ± 0.005 mm diameter tungsten lanthanum hafnium alloy black wire; wherein the process and conditions of this step are the same as those in Example 1;

[0251] 9. Use electrolytic cleaning to clean the 0.52mm black wire into 0.50mm±0.005mm tungsten lanthanum hafnium alloy white wire that can be processed into microwave oven heating device filament;

[0252] 10. Wind 0.50mm tungsten-lanthanum-hafnium alloy white wire into a spring-shaped cathode filament for the heating device; the number of turns is 10, and the pitch is 1.29±0.03mm;

[0253] 11. Assemble the filament, components, ceramics, lead pieces and other parts into the cathode structure through heat treatment at a temperature of 600°C.

[0254] 12. Weld the filament in the cathode structure to the end cap of the assembly.

[0255] 13. Place the cathode structure in a carbonization tank for carbonization. After exhausting, introduce carbon-containing hydrocarbon gas (specifically methane) and apply direct current of a certain current value (current value is 16A) to the cathode for heating, so that the filament is carbonized in the hydrocarbon gas.

[0256] 14. White ball assembly: Assemble the cathode structure, anode cylinder, antenna end cap and other components together.

[0257] 15. The white ball is evacuated and aged at high temperature to complete the production of the black ball and activate its launch performance.

[0258] 16. Assemble the black ball, heat sink, magnet, tube shell, etc. to finally obtain the heating device component containing the above-mentioned filament, and install it in a microwave oven for use.

[0259] Example 6

[0260] 1. According to the formula in Table 1, add 5L of deionized water to a certain amount of lanthanum nitrate-hafnium nitrate solution and stir for 10 minutes to fully dissolve. Then, add 1L of ammonia NH3·H2O solution and stir to neutralize. Spray the prepared mixed solution evenly onto the blue tungsten in the doping pot and stir. The ratio of lanthanum nitrate-hafnium nitrate solution to ammonia NH3·H2O solution is 5:1.

[0261] 2. Evacuate the doping pot and heat it with water (heating temperature 80°C, vacuum degree -0.025MPa), stirring while heating;

[0262] 3. Dry the powder by steam heating under vacuum conditions, with a steam pressure of 0.1-0.3 MPa and a vacuum degree in the pot of ≤-0.02 MPa, to obtain tungsten, lanthanum, and hafnium doped powder with uniform doping and low impurity content.

[0263] 4. In a reduction furnace with four temperature zones of 650°C, 750°C, 850°C and 900°C, the tungsten lanthanum and hafnium doped powder is reduced into tungsten lanthanum and hafnium powder with a suitable particle size and a content of 2.0% La2O3 + 1.0% HfO2;

[0264] 5. The obtained tungsten lanthanum hafnium powder and tungsten carbide were placed in a high-speed powder mixer for solid-solid mixing for 2 hours, and sieved to obtain a mixed tungsten lanthanum hafnium alloy powder with a content of 2.0% La2O3+1.0% HfO2+2.0% WC;

[0265] 6. Use isostatic pressing to press the powder with a particle size of 1.5 μm into a green compact weighing 3.0 kg at a pressure of 180 MPa. The green compact is then pre-sintered at a low temperature in a hydrogen atmosphere to increase its strength.

[0266] 7. Use high temperature sintering to obtain oxide particles with a particle size of <2.0μm and a density of 18.0g / cm 3 wherein the process and conditions of this step are consistent with those of Example 1;

[0267] 8. Using multiple passes of rotary forging and drawing, the 17 mm diameter sintered billet was processed into a 0.52 mm ± 0.005 mm diameter tungsten lanthanum hafnium alloy black wire; wherein the process and conditions of this step are the same as those in Example 1;

[0268] 9. Use electrolytic cleaning to clean the 0.52mm black wire into 0.50mm±0.005mm tungsten lanthanum hafnium alloy white wire that can be processed into microwave oven heating device filament;

[0269] 10. Wind 0.50mm tungsten-lanthanum-hafnium alloy white wire into a spring-shaped cathode filament for the heating device; the number of turns is 10, and the pitch is 1.29±0.03mm;

[0270] 11. Assemble the filament, components, ceramics, lead pieces and other parts into the cathode structure through heat treatment at a temperature of 600°C.

[0271] 12. Weld the filament in the cathode structure to the end cap of the assembly.

[0272] 13. Place the cathode structure in a carbonization tank for carbonization. After exhausting, introduce carbon-containing hydrocarbon gas (specifically methane gas) and apply direct current of a certain current value (current value is 16A) to the cathode for heating, so that the filament is carbonized in the hydrocarbon gas.

[0273] 14. White ball assembly: Assemble the cathode structure, anode cylinder, antenna end cap and other components together.

[0274] 15. The white ball is evacuated and aged at high temperature to complete the production of the black ball and activate its launch performance.

[0275] 16. Assemble the black ball, heat sink, magnet, tube shell, etc. to finally obtain the heating device component containing the above-mentioned filament, and install it in a microwave oven for use.

[0276] Example 7

[0277] 1. According to the formula in Table 1, add a certain amount of lanthanum nitrate to 5L of deionized water. Stir for 10 minutes to fully dissolve it. Then add 1L of ammonia NH3·H2O solution and stir to neutralize it. Spray the prepared mixed solution evenly onto the blue tungsten placed in the doping pot and stir. The volume ratio of lanthanum nitrate solution to ammonia NH3·H2O solution is 5:1.

[0278] 2. Evacuate the doping pot and heat it with water (heating temperature 80°C, vacuum degree -0.025MPa), stirring while heating;

[0279] 3. Under vacuum conditions, the powder is dried by steam heating, with a steam pressure of 0.1-0.3 MPa and a vacuum degree in the pot of ≤-0.02 MPa, ultimately obtaining tungsten-lanthanum doped powder with uniform doping and low impurity content;

[0280] 4. Reduce the tungsten-lanthanum doped powder into tungsten-lanthanum powder of appropriate particle size in a reduction furnace with four temperature zones of 650°C, 750°C, 850°C and 900°C;

[0281] 5. According to the formula in Table 1, add 5L of deionized water to the doping pot and heat it to 80°C. Then add a certain amount of ammonium rhenate and stir for 10 minutes to fully dissolve it. Then add a certain amount of tungsten lanthanum powder to the ammonium rhenate solution and stir for 30 minutes. Then, dry the powder by steam heating under vacuum conditions. The steam pressure is 0.1-0.3MPa and the vacuum degree in the pot is ≤-0.02MPa. Finally, rhenium-doped tungsten lanthanum powder with uniform doping and low impurity content is obtained.

[0282] 6. Reduce the rhenium-doped tungsten-lanthanum powder into tungsten-lanthanum-rhenium alloy powder with a particle size of 1.5 μm in a reduction furnace with four temperature zones of 650°C, 750°C, 850°C and 900°C;

[0283] 7. The obtained tungsten lanthanum rhenium alloy powder and tungsten carbide are placed in a high-speed powder mixer for solid-solid mixing for 2 hours, and then sieved to obtain the mixed tungsten lanthanum rhenium alloy powder;

[0284] 8. Use isostatic pressing to press the powder with a particle size of 1.5 μm into a green compact weighing 3.0 kg at a pressure of 180 MPa. The green compact is then pre-sintered at a low temperature in a hydrogen atmosphere to increase its strength.

[0285] 9. Using high temperature sintering method, the oxide particles with particle size <2.0μm and density 18.0g / cm 3wherein the process and conditions of this step are consistent with those of Example 1;

[0286] 10. Using multiple passes of rotary forging and drawing, the 17 mm diameter sintered billet was processed into a 0.52 mm ± 0.005 mm diameter tungsten lanthanum rhenium alloy black wire; wherein the process and conditions of this step are the same as those in Example 1;

[0287] 11. Use electrolytic cleaning to clean the 0.52mm black wire into 0.50mm±0.005mm tungsten lanthanum rhenium alloy white wire that can be processed into microwave oven heating device filament;

[0288] 12. Wind 0.50mm tungsten-lanthanum-rhenium alloy white wire into a spring-shaped cathode filament for the heating device, with 10 turns and a pitch of 1.29±0.03mm;

[0289] 13. Assemble the filament, components, ceramics, lead pieces and other parts into a cathode structure through heat treatment at a temperature of 600°C.

[0290] 14. Weld the filament in the cathode structure to the end cap of the assembly.

[0291] 15. Place the cathode structure in a carbonization tank for carbonization. After exhausting, introduce carbon-containing hydrocarbon gas (specifically methane) and apply direct current of a certain current value (current value is 16A) to the cathode for heating, so that the filament is carbonized in the hydrocarbon gas.

[0292] 16. White ball assembly: Assemble the cathode structure, anode cylinder, antenna end cap and other components together.

[0293] 17. The white ball is evacuated and aged at high temperature to complete the production of the black ball and activate its launch performance.

[0294] 18. Assemble the black ball, heat sink, magnet, tube shell, etc. to finally obtain a heating device component containing the above-mentioned filament, and install it in a microwave oven for use.

[0295] Comparative Example 1:

[0296] 1. According to the formula in Table 1, add 5L of deionized water to a certain amount of thorium nitrate solution. Stir for 10 minutes to fully dissolve it. Then add 1L of ammonia NH3·H2O solution and stir to neutralize it. Spray the prepared mixed solution evenly onto the blue tungsten placed in the doping pot and stir. The ratio of thorium nitrate solution to ammonia NH3·H2O solution is 5:1.

[0297] 2. Evacuate the doping pot and heat it with water (heating temperature 80°C, vacuum degree -0.025MPa), stirring while heating;

[0298] 3. Under vacuum conditions, the powder is dried by steam heating, with a steam pressure of 0.1-0.3 MPa and a vacuum degree in the pot of ≤-0.02 MPa, ultimately obtaining thorium-tungsten doped powder with uniform doping and low impurity content;

[0299] 4. Reduce the thoriated tungsten doped powder into thoriated tungsten powder with a particle size of 1.5 μm in a reduction furnace with four temperature zones of 650°C, 750°C, 850°C and 900°C;

[0300] 5. The obtained thoriated tungsten powder is placed in a V-type powder mixer and mixed for 2 hours. The mixed thoriated tungsten powder is then sieved to obtain the mixed thoriated tungsten powder.

[0301] 6. Use isostatic pressing to press 1.5μm thoriated tungsten powder into a green compact weighing 3.0kg at a pressure of 180MPa. The green compact is then pre-sintered at a low temperature in a hydrogen atmosphere to increase its strength.

[0302] 7. Using high temperature sintering method, thorium oxide particles with a particle size of <2.0μm and a density of 18.0g / cm 3 wherein the process and conditions of this step are consistent with those of Example 1;

[0303] 8. Using multiple passes of rotary forging and drawing, the 17 mm diameter sintered billet was processed into a 0.52 mm ± 0.005 mm diameter thoriated tungsten alloy black wire; wherein the process and conditions of this step are the same as those in Example 1;

[0304] 9. Use electrolytic cleaning to clean the 0.52mm black wire into 0.50mm±0.005mm thoriated tungsten alloy white wire that can be processed into microwave oven heating device filament;

[0305] 10. Wind 0.50mm thoriated tungsten white wire into a spring-shaped cathode filament for the heating device; the number of turns is 10, and the pitch is 1.29±0.03mm;

[0306] 11. Assemble the filament, components, ceramics, lead pieces and other parts into the cathode structure through heat treatment at a temperature of 600°C.

[0307] 12. Weld the filament in the cathode structure to the end cap of the assembly.

[0308] 13. Place the cathode structure in a carbonization tank for carbonization. After exhausting, introduce carbon-containing hydrocarbon gas (methane gas) and apply direct current of a certain current value (current value is 16A) to the cathode for heating, so that the filament is carbonized in the hydrocarbon gas.

[0309] 14. White ball assembly: Assemble the cathode structure, anode cylinder, antenna end cap and other components together.

[0310] 15. The white ball is evacuated and aged at high temperature to complete the production of the black ball and activate its launch performance.

[0311] 16. Assemble the black ball, heat sink, magnet, tube shell, etc. to finally obtain the heating device component containing the above-mentioned filament, and install it in a microwave oven for use.

[0312] Comparative Example 2:

[0313] 1. According to the formula in Table 1, add 5L of deionized water to a certain amount of lanthanum nitrate-yttrium nitrate solution. Stir for 10 minutes to fully dissolve it. Then add 1L of ammonia NH3·H2O solution and stir to neutralize it. Spray the prepared mixed solution evenly onto the blue tungsten placed in the doping pot and stir. The ratio of lanthanum nitrate-yttrium nitrate solution to ammonia NH3·H2O solution is 5:1.

[0314] 2. Evacuate the doping pot and heat it with water (heating temperature 80°C, vacuum degree -0.025MPa), stirring while heating;

[0315] 3. Under vacuum conditions, the powder is dried by steam heating, with a steam pressure of 0.1-0.3 MPa and a vacuum degree in the pot of ≤-0.02 MPa, ultimately obtaining tungsten, lanthanum, and yttrium doped powder with uniform doping and low impurity content;

[0316] 4. In a reduction furnace with four temperature zones of 650°C, 750°C, 850°C and 900°C, the tungsten lanthanum yttrium doped powder is reduced into tungsten lanthanum yttrium powder with a particle size of 1.5μm;

[0317] 5. The obtained tungsten lanthanum yttrium powder is placed in a V-type powder mixer and mixed for 2 hours, and then sieved to obtain a mixed tungsten lanthanum yttrium alloy powder;

[0318] 6. Using isostatic pressing, 1.5 μm tungsten-lanthanum-yttrium alloy powder was pressed at a pressure of 180 MPa into a compact weighing 3.0 kg. The compact was then pre-sintered at a low temperature in a hydrogen atmosphere to increase its strength.

[0319] 7. Use high temperature sintering to obtain oxide particles with a particle size of <2.0μm and a density of 18.0g / cm 3 wherein the process and conditions of this step are consistent with those of Example 1;

[0320] 8. Using multiple passes of rotary forging and drawing, the 17 mm diameter sintered billet was processed into a 0.52 mm ± 0.005 mm diameter tungsten-lanthanum-yttrium alloy black wire; wherein the process and conditions of this step are the same as those in Example 1;

[0321] 9. Use electrolytic cleaning to clean the 0.52mm black wire into 0.50mm±0.005mm tungsten lanthanum yttrium alloy white wire that can be processed into microwave oven heating device filament;

[0322] 10. Wind 0.50mm tungsten-lanthanum-yttrium alloy white wire into a spring-shaped cathode filament for the heating device; the number of turns is 10, and the pitch is 1.29±0.03mm;

[0323] 11. Assemble the filament, components, ceramics, lead pieces and other parts into the cathode structure through heat treatment at a temperature of 600°C.

[0324] 12. Weld the filament in the cathode structure to the end cap of the assembly.

[0325] 13. Place the cathode structure in a carbonization tank for carbonization. After exhausting, introduce carbon-containing hydrocarbon gas (specifically methane) and apply direct current of a certain current value (current value is 16A) to the cathode for heating, so that the filament is carbonized in the hydrocarbon gas.

[0326] 14. White ball assembly: Assemble the cathode structure, anode cylinder, antenna end cap and other components together.

[0327] 15. The white ball is evacuated and aged at high temperature to complete the production of the black ball and activate its launch performance.

[0328] 16. Assemble the black ball, heat sink, magnet, tube shell, etc. to finally obtain the heating device component containing the above-mentioned filament, and install it in a microwave oven for use.

[0329] Comparative Example 3:

[0330] 1. According to the formula in Table 1, add 5L of deionized water to a certain amount of lanthanum nitrate-scandium nitrate solution. Stir for 10 minutes to fully dissolve it. Then add 1L of ammonia NH3·H2O solution and stir to neutralize it. Spray the prepared mixed solution evenly onto the blue tungsten placed in the doping pot and stir. The ratio of lanthanum nitrate-scandium nitrate solution to ammonia NH3·H2O solution is 5:1.

[0331] 2. Evacuate the doping pot and heat it with water (heating temperature 80°C, vacuum degree -0.025MPa), stirring while heating;

[0332] 3. Dry the powder by steam heating under vacuum conditions, with a steam pressure of 0.1-0.3 MPa and a vacuum degree in the pot of ≤-0.02 MPa, to obtain tungsten, lanthanum, and scandium doped powder with uniform doping and low impurity content.

[0333] 4. In a reduction furnace with four temperature zones of 650°C, 750°C, 850°C and 900°C, the tungsten lanthanum scandium doped powder is reduced into tungsten lanthanum scandium powder with a particle size of 1.5 μm;

[0334] 5. The obtained tungsten lanthanum scandium powder is placed in a V-type powder mixer and mixed for 2 hours, and then sieved to obtain a mixed tungsten lanthanum scandium alloy powder;

[0335] 6. Use isostatic pressing to press the powder with a particle size of 1.5 μm into a green compact weighing 3.0 kg at a pressure of 180 MPa. The green compact is then pre-sintered at a low temperature in a hydrogen atmosphere to increase its strength.

[0336] 7. Use high temperature sintering to obtain oxide particles with a particle size of <2.0μm and a density of 18.0g / cm 3 wherein the process and conditions of this step are consistent with those of Example 1;

[0337] 8. Using multiple passes of rotary forging and drawing, the 17 mm diameter sintered billet was processed into a 0.52 mm ± 0.005 mm diameter tungsten lanthanum scandium alloy black wire; wherein the process and conditions of this step are the same as those in Example 1;

[0338] 9. Use electrolytic cleaning to clean the 0.52mm black wire into 0.50mm±0.005mm tungsten lanthanum scandium alloy white wire that can be processed into microwave oven heating device filament;

[0339] 10. Wind 0.50mm tungsten-lanthanum-scandium alloy white wire into a spring-shaped cathode filament for the heating device; the number of turns is 10, and the pitch is 1.29±0.03mm;

[0340] 11. Assemble the filament, components, ceramics, lead pieces and other parts into the cathode structure through heat treatment at a temperature of 600 degrees Celsius.

[0341] 12. Weld the filament in the cathode structure to the end cap of the assembly.

[0342] 13. Place the cathode structure in a carbonization tank for carbonization. After exhausting, introduce carbon-containing hydrocarbon gas (preferably methane gas) and apply direct current of a certain current value (preferably 16A) to the cathode for heating, so that the filament is carbonized in the hydrocarbon gas.

[0343] 14. White ball assembly: Assemble the cathode structure, anode cylinder, antenna end cap and other components together.

[0344] 15. The white ball is evacuated and aged at high temperature to complete the production of the black ball and activate its launch performance.

[0345] 16. Assemble the black ball, heat sink, magnet, tube shell, etc. to finally obtain a heating device component (i.e., heating device) containing the above-mentioned filament, and install it in a microwave oven for use.

[0346] Comparative Example 4:

[0347] The cathode filament of Example 1 is used, and the carbonization current in the carbonization process of Example 1 is increased by 2A, thereby increasing the grain size of the carbonized structure and increasing the grain width from 3-10 μm in Example 1 to 10-30 μm.

[0348] It should be noted that one of the means to control the grain size is to control the carbonization current. By adjusting the carbonization current, the grain size can be controlled within the required range. The design point of this application to achieve the desired effect is to control the grain size within the specified range of this application.

[0349] Comparative Example 5

[0350] 1. According to the formula in Table 1, add a certain amount of lanthanum nitrate to 5L of deionized water. Stir for 10 minutes to fully dissolve it. Then add 1L of ammonia NH3·H2O solution and stir to neutralize it. Spray the prepared mixed solution evenly onto the blue tungsten placed in the doping pot and stir. The volume ratio of lanthanum nitrate solution to ammonia NH3·H2O solution is 5:1.

[0351] 2. Evacuate the doping pot and heat it with water (heating temperature 80°C, vacuum degree -0.025MPa), stirring while heating;

[0352] 3. Under vacuum conditions, the powder is dried by steam heating, with a steam pressure of 0.1-0.3 MPa and a vacuum degree in the pot of ≤-0.02 MPa, ultimately obtaining tungsten-lanthanum doped powder with uniform doping and low impurity content;

[0353] 4. Reduce the tungsten-lanthanum doped powder into tungsten-lanthanum powder of appropriate particle size in a reduction furnace with four temperature zones of 650°C, 750°C, 850°C and 900°C;

[0354] 5. According to the formula in Table 1, add 5L of deionized water to the doping pot and heat it to 80°C. Then add a certain amount of ammonium rhenate and stir for 10 minutes to fully dissolve it. Then add a certain amount of tungsten lanthanum powder to the ammonium rhenate solution and stir for 30 minutes. Then, dry the powder by steam heating under vacuum conditions. The steam pressure is 0.1-0.3MPa and the vacuum degree in the pot is ≤-0.02MPa. Finally, rhenium-doped tungsten lanthanum powder with uniform doping and low impurity content is obtained.

[0355] 6. Reduce the rhenium-doped tungsten-lanthanum powder into tungsten-lanthanum-rhenium alloy powder with a particle size of 1.5 μm in a reduction furnace with four temperature zones of 650°C, 750°C, 850°C and 900°C;

[0356] 7. The obtained tungsten lanthanum rhenium alloy powder and tungsten carbide are placed in a high-speed powder mixer for solid-solid mixing for 2 hours, and then sieved to obtain the mixed tungsten lanthanum rhenium alloy powder;

[0357] 8. Use isostatic pressing to press the powder with a particle size of 1.5 μm into a green compact weighing 3.0 kg at a pressure of 180 MPa. The green compact is then pre-sintered at a low temperature in a hydrogen atmosphere to increase its strength.

[0358] 9. Using high temperature sintering method, the oxide particles with particle size <2.0μm and density 18.0g / cm 3 wherein the process and conditions of this step are consistent with those of Example 1;

[0359] 10. Using multiple passes of rotary forging and drawing, the 17 mm diameter sintered billet was processed into a 0.52 mm ± 0.005 mm diameter tungsten lanthanum rhenium alloy black wire; wherein the process and conditions of this step are the same as those in Example 1;

[0360] 11. Use electrolytic cleaning to clean the 0.52mm black wire into 0.50mm±0.005mm tungsten lanthanum rhenium alloy white wire that can be processed into microwave oven heating device filament;

[0361] 12. Wind 0.50mm tungsten-lanthanum-rhenium alloy white wire into a spring-shaped cathode filament for the heating device, with 10 turns and a pitch of 1.29±0.03mm;

[0362] 13. Assemble the filament, components, ceramics, lead pieces and other parts into a cathode structure through heat treatment at a temperature of 600°C.

[0363] 14. Weld the filament in the cathode structure to the end cap of the assembly.

[0364] 15. Place the cathode structure in a carbonization tank for carbonization. After exhausting, introduce carbon-containing hydrocarbon gas (specifically methane) and apply direct current of a certain current value (current value is 16A) to the cathode for heating, so that the filament is carbonized in the hydrocarbon gas.

[0365] 16. White ball assembly: Assemble the cathode structure, anode cylinder, antenna end cap and other components together.

[0366] 17. The white ball is evacuated and aged at high temperature to complete the production of the black ball and activate its launch performance.

[0367] 18. Assemble the black ball, heat sink, magnet, tube shell, etc. to finally obtain a heating device component containing the above-mentioned filament, and install it in a microwave oven for use.

[0368] The tungsten alloy wires, tungsten alloy filaments, and devices (microwave ovens) containing the filament components prepared in the above examples and comparative examples were tested for relevant performance indicators under the same test conditions. The test results are shown in the following table:

[0369] Table 2 Note: The yield rate statistics refer to the yield rate from billet to finished filament.

[0370] Table 3

[0371] In Table 2-3, the test standard for the recrystallization temperature range item is GB T 23272-2009 Tungsten filaments for lighting and electronic equipment; FC represents the size of the fusing current, and the conversion method of FC% and degrees Celsius is as follows: as shown in Figure 21, Article 4.3.2.2 of the high-temperature performance test method of GB / T 23272-2009 national standard for tungsten filaments for lighting and electronic equipment provides a reference correspondence between FC% and temperature, which can be used for conversion by reference to this correspondence; the electron work function is determined according to the Richardson linear method; the working life of the tungsten alloy filament is tested according to Article 6.5.2 of the life test method of GB / T 23152-2008 national standard for heating devices for household microwave ovens, where the standard requires continuous operation of heating devices for microwave ovens to be >500h; the preparation process of steps 10-14 in the embodiment and the test nodes for each test item are shown in Figure 20.

[0372] 1. Comparison of Example 1 and Comparative Example 1, where Comparative Example 1 is a thoriated tungsten filament:

[0373] The metallographic conditions of Example 1 and Comparative Example 1 at different fusing currents are shown in Figures 5-11. It can be clearly seen that the recrystallization temperature of Example 1 is 50% FC (approximately 2120°C), while the recrystallization temperature of Comparative Example 1 is 46% FC (approximately 2020°C). This indicates that the initial recrystallization temperature of the filament material of the present application is higher than that of the existing thoriated tungsten filament.

[0374] The grain size of the filament after carbonization in Example 1 and Comparative Example 1 is shown in Figures 12-13: Figure 13 shows that the filament structure after carbonization in Example 1 is still fine-grained, while Figure 12 shows that the grains of the filament structure after carbonization in Comparative Example 1 are significantly larger. From the data, the number of grains of the tungsten substrate 100 after carbonization in Example 1 is 4000 / mm 2 , Comparative Example 1 is 100 pieces / mm 2 The grain width of the carbonized layer 200 of Example 1 is 6.83 μm, and that of Comparative Example 1 is 9.81 μm.

[0375] The distribution of channels 210 of the carbonized filaments in Example 1 and Comparative Example 1 is shown in Figures 14-16. Figure 14 shows that the carbonized layer 200 of the cross-section of the carbonized filament in Example 1 is distributed with many first channels 211 that are perpendicular to the filament edge, and the second channels 212 intersect with the first channels to form a ring-like distribution, and the carbonized layer 200 forms a layer block. Figure 15 shows that the carbonized layer 200 of the longitudinal section of the carbonized filament in Example 1 is distributed with many first channels 211 that are perpendicular to the filament edge; while Figure 16 shows that the carbonized layer 200 of the cross-section of the filament in Comparative Example 1 has a significantly reduced number of first channels 211 that are perpendicular to the filament edge, and a very small number of parallel second channels 212 are distributed. The reason for this is that the grain width of the carbonized layer in Comparative Example 1 is larger, and the number of its channels 210 is related to the size of the grains, and the grain size affects the formation of the channels 210.

[0376] In Example 1 of the present application, the layered structure in the carbonized layer 200 separated by the second channel 212 is where the oxide of M is distributed. The first channel 211 is vertically distributed to the edge of the filament, connecting the interior of the substrate 100, the second channel 212 and the edge of the filament. The second channel 212 is combined with the first channel 211, which is conducive to the outward migration of rare earth atoms and timely replenishment of rare earth elements evaporated from the surface, thereby improving the stability of material emission.

[0377] 2. Comparing Example 1 and Comparative Example 4, the difference between Comparative Example 4 and Example 1 is that the grain size of the carbonized layer is significantly larger:

[0378] Figures 17-18 show the carbonized filament in Comparative Example 4, showing cross-sectional and longitudinal sections. The channels 210 distributed within the carbonized layer 200 are clearly parallel to the filament's outer edge 220, failing to form a layered, blocky structure. Furthermore, the data in Tables 2-3 demonstrate that while Example 1 exhibits stable emission performance after 30 minutes of operation, Comparative Example 4 experiences microwave extinction after less than 10 minutes of operation, resulting in unstable emission.

[0379] The analysis of its mechanism is:

[0380] Although a structure similar to the channel 210 appears inside the carbonized layer 200 of Comparative Example 4, this channel 210 is parallel to the edge of the filament, and the cross-section of the carbonized layer 200 forms a layered structure. The reason for this is that the grain size in the carbonized layer 200 is relatively large, at 23.12 μm, and the grain size affects the formation of the channel 210. It is difficult to form a large number of vertically distributed channels 210 in the carbonized layer 200. The layered structure of the carbonized layer 200 separates the interior of the substrate 100 from the edge of the filament. When rare earth atoms migrate from the inside to the outside, when they encounter the channel 210 parallel to the edge of the filament, their migration is hindered and they cannot diffuse further outward or the diffusion becomes more difficult, thereby reducing the emission performance.

[0381] In contrast, in Example 1 of the present application, the grain size in the carbonized layer 200 is small, only 6.83 μm, thereby forming a larger number of second channels 212 and a larger number of first channels 211 that are cross-distributed. The carbonized layer 200 forms a layer block. The layered structure in the carbonized layer 200 separated by the second channel 212 is where the oxide of M is distributed. The first channel 211 is vertically distributed to the edge of the filament, connecting the interior of the substrate 100 and the second channel 212 to the edge of the filament. The more the number of the above-mentioned channels 210, the more conducive it is to the migration of rare earth atoms. Example 1 combines the second channel 212 with the first channel 211, which is conducive to the outward migration of rare earth atoms and timely replenishment of rare earth elements evaporated from the surface, thereby improving the stability of material emission.

[0382] 3. Comparison of Example 2 and Comparative Example 2, Example 4 and Comparative Example 3:

[0383] 3.1 The difference between Example 2 and Comparative Example 2 is that: Comparative Example 2 does not add carbide raw materials, and its components do not contain carbon;

[0384] Comparing the two results, it can be seen that compared with Example 2, the recrystallization temperature of Example 2 is lower, the grain width of the carbonized layer is larger, and the carbonized layer 200 has a block structure, which is reflected in the performance: its emission performance stability deteriorates, the electron emission performance deteriorates, and the working life becomes shorter.

[0385] 3.2 The difference between Example 4 and Comparative Example 3 is that: Comparative Example 3 does not add carbide raw materials and its components do not contain carbon; comparing the results of the two, it can be seen that: compared with Example 4, the recrystallization temperature of Comparative Example 3 is lower, the grain width of the carbonized layer is larger, and the carbonized layer 200 has a block structure, which is reflected in the performance: its emission performance stability deteriorates, the electron emission performance deteriorates, and the working life becomes shorter.

[0386] The analysis of its mechanism is:

[0387] In the embodiments of the present application, by adding one or more oxides and carbides or carbon elements of M, the oxides and carbides of M in the tungsten matrix react at high temperatures, and the generated M metal atoms are much smaller than the particles of M oxides. The migration and diffusion speed of the M metal atoms in the tungsten matrix is ​​accelerated. Therefore, compared with the thoriated tungsten filament, it can achieve the same or even higher electron emission capability at a lower operating voltage (excitation temperature). However, since no carbon raw material is added in Comparative Examples 2-3, the above effect cannot be achieved, and its electron emission performance is deteriorated.

[0388] 4. Comparative Example 7 and Comparative Example 5:

[0389] The difference between Example 7 and Comparative Example 5 is that the Re content of Comparative Example 5 exceeds the specified range of this application;

[0390] Comparing the two results reveals that the operating temperature of Comparative Example 5 is higher and the service life is shorter. The inventors analyze that rhenium has the effects of purifying grain boundaries and strengthening the solid solution of rhenium and tungsten. However, the addition of rhenium beyond the specified range of this application results in excessive strengthening and work hardening, making the wire more susceptible to cracking. This is clearly evident in the wire flaw detection data: Example 7 shows 0.8-1.5 crack points per 100 meters, while Comparative Example 5 shows 6-10 crack points per 100 meters.

[0391] In summary, it can be clearly concluded from the test results of the embodiments and comparative examples that:

[0392] 1. By observing the cross-sectional structure, longitudinal section structure and the carbonized layer 200 part of the longitudinal section structure:

[0393] Compared to thoriated tungsten filaments, the carbide layer 200 of the thoriated tungsten lanthanum filament in this application has smaller grain size and slightly narrower grain width than thoriated tungsten filaments, resulting in a greater number of channels 210 in the carbide layer 200 of this application. The carbide layer 200 at different locations in the filament provided by this application has an organization similar to the cross-section of the first channel 211 and the second channel 212, forming a layered block structure. The first channel 211 is perpendicular to the edge of the filament, connecting the second channel 212, the interior of the substrate 100, and the edge of the filament. This facilitates the outward migration of rare earth atoms and timely replenishes rare earth elements evaporated from the surface, improving the stability of the material's emission. The emission performance stabilization time data in the test results clearly shows that there are differences in the emission performance of the filaments. The emission performance of the filament in this application is stable and comparable to that of traditional thoriated tungsten filaments.

[0394] It can be seen that the tungsten carbide alloy material of the present application replenishes the rare earth element evaporated from the surface through the stable outward migration of rare earth, thereby improving the stability of the material's emission. Without adding thorium elements, it can also achieve the stable emission capability of traditional thorium tungsten filaments, solving the problem of poor stable emission capability of existing thorium-free tungsten filaments, and does not have the radioactive pollution problem of traditional thorium tungsten filaments.

[0395] 2. There is a carbonization process in the preparation process of the filament. The carbonization temperature is 2000-2200℃. The original thoriated tungsten filament is carbonized at this temperature, and the grain structure will recrystallize. The grains are coarse, causing the filament to break easily after carbonization. If the vibration in the production process is slightly larger, the filament will break (the wire breakage rate is about 20,000-30,000 ppm).

[0396] The recrystallization temperatures measured in Examples 1-7 ranged from 48% FC (approximately 2070°C) to 52% FC (approximately 2180°C), while the recrystallization temperature of Comparative Example 1 was 46% FC (approximately 2020°C). The filament material produced by the present application has a higher initial recrystallization temperature than the existing thoriated tungsten filament, and the filament structure after carbonization remains fine-grained (the grain size of the examples of the present application is significantly smaller than that of the comparative example). The fine-grained filament is less susceptible to breakage.

[0397] 3. It can be clearly seen from the test results that the filament material of the present application has better processing performance than the original thoriated tungsten, with fewer crack points during flaw detection (when the filament diameter can reach 500 μm, the number of crack points during flaw detection of the filament is less than 2 per 100 meters), a higher processing yield rate, and the wound filament is not prone to breakage, thereby improving production efficiency. In addition, the wire material has fewer crack points, and the proportion of carbonized broken filaments produced is also low.

[0398] 4. It can be clearly seen from the electron emission performance parameters in the test results that the DC emission capacity of the heating device made of the filament of the present application is nearly twice that of the thoriated tungsten filament (Comparative Example 1), so that the heating device made of the filament provided by the present application can excite electrons at a lower voltage (Note: According to the usage of heating devices in this field, the starting voltage of the thoriated tungsten heating device must be at least 2.0V. In order to ensure starting, the operating voltage is set at 3.3V, while the starting voltage of Example 1 is 1.4V, and the operating voltage can be in the range of 1.6 to 1.8V).

[0399] The operating temperature of the heating device of the present application can be reduced from 1500-1600°C to 1100-1500°C, such as the range of 1200-1300°C, while the operating temperature of the traditional thorium tungsten filament is 1600-1900°C. Therefore, the energy consumption and life of the heating device provided by the present application will be improved.

[0400] In summary, the embodiments of the present application improve the emission stability of the material by controlling the grain size of the carbonized layer 200 and combining it with the M element component contained therein, thereby replenishing the rare earth element evaporated from the surface through the stable outward migration of rare earth elements. Without the addition of thorium, the embodiment can achieve the stable emission capability of a traditional thoriated tungsten filament, solving the problem of poor stable emission capability of existing thorium-free tungsten filaments. Furthermore, the embodiment does not have the radioactive contamination problem of traditional thoriated tungsten filaments, making it more environmentally friendly.

[0401] The embodiment of the present application can significantly increase the initial recrystallization temperature of the material by doping M oxides and carbides into the tungsten matrix powder, and can still obtain extremely fine grains at the same carburization temperature as that of thoriated tungsten. It can improve the processing performance of the material, reduce the wire breakage rate during the production and use of the material, and reduce the electronic work function of the material. It can not only reduce the wire breakage rate and improve the yield to reduce production and transportation costs, but also effectively increase the service life of the filament, so that its service life reaches and far exceeds the service life of existing thoriated tungsten filaments.

[0402] In summary, the above technical solutions provided by this application include at least the following working principles or mechanisms and beneficial effects:

[0403] (1) The grain width of the carbide layer 200 of the filament of the present application is controlled within a certain small size range, and the grain width of the carbide layer 200 is 1.0 to 15.0 μm. Compared with the thoriated tungsten filament, the grain size of the carbide layer 200 in the thorium-free filament of the present application is smaller than that of the thoriated tungsten filament, and the grain width is slightly narrower than that of the thoriated tungsten filament. The number of channels 210 in the carbide layer 200 of the present application is greater. The organization of the carbide layer 200 at different positions in the filament provided by the present application has a layered block structure organization similar to that formed by the intersection of the first channel 211 and the second channel 212. The first channel 211 is vertically distributed with the edge of the filament, connecting the interior of the substrate 100 and the second channel 212 with the edge of the filament, which is conducive to the outward migration of rare earth atoms and the timely replenishment of rare earth elements evaporated from the surface, thereby improving the stability of the material emission.

[0404] (2) The initial recrystallization temperature of the filament material provided in the present application is between 48% FC (about 2070°C) and 56% FC (about 2290°C). Therefore, after carburization at a temperature of 2000-2100°C, the grains of the tungsten matrix 100 are relatively small. The brittleness of the carburized filament is less than that of the traditional thoriated tungsten filament material, which will reduce the filament breakage rate of customers during production and use.

[0405] (3) The processing performance of the filament material of the present application is better than that of the original thoriated tungsten, the number of flaw detection cracks is less (when the filament wire diameter can reach 500 μm, the number of flaw detection cracks of the filament is less than 2 / 100 meters), the processing yield is high, the wound filament is not easy to break, and the production efficiency is improved. In addition, the wire material has fewer cracks, and the proportion of carbonized broken filaments in the manufactured filaments is also low.

[0406] In the filament material provided by the present application, the oxide of M (such as lanthanum oxide particles) has good plasticity. As the pressure processing proceeds, the oxide particles of M will become thin and long, and exist in a linear or linear-like shape; while the thorium oxide in the traditional thoriated tungsten material has poor plasticity. After the thoriated tungsten is processed to a certain extent, the thorium oxide will break. As the processing proceeds, the thorium oxide will appear as a string of particles; the types of rare earth oxides added in the present application and the changes in morphological structure during the refinement process make the filament material have good processing performance. When preparing wire materials for winding filaments, the wire diameter of the filament material can be refined to 500μm or less, and the number of crack points during flaw detection is effectively reduced, thereby improving the yield.

[0407] (4) The thickness of the carbonized layer 200 of the filament of the present application is preferably controlled to be 30-90 μm;

[0408] The thickness of the carbide layer 200 of a conventional thoriated tungsten filament is generally 35-45 μm. The thicker the carbide layer 200, the longer the service life of the heating device. However, the conventional thoriated tungsten carbide layer 200 cannot be made thicker because if it is too thick, the recrystallized grains of the tungsten substrate 100 after carbide will be greatly coarsened, making the carbide filament very brittle. During production and use, the filament breakage rate in the heating device can reach 10,000 to 30,000 ppm.

[0409] Currently, the thickness of the carbonized layer 200 of the filament in the embodiment of the present application is generally between 35 and 50 μm. Unlike thoriated tungsten filaments, the thickness of the carbonized layer in the present embodiment can be increased, which is beneficial for extending the lifespan. The initial recrystallization temperature of the present embodiment is relatively high, and the tungsten matrix 100 after carburization still has a fine-grained structure, resulting in a very low filament breakage rate. Thus, the present embodiment can increase the thickness to extend the service life while maintaining a low filament breakage rate, making it possible to thicken the carbonized layer 200.

[0410] (5) The operating temperature of the heating device provided in the present application (i.e., the operating temperature of the filament) can be reduced from 1500°C to 1600°C to 1100°C to 1500°C, such as within the range of 1200°C to 1300°C, and still maintain a good working condition; while the operating temperature of the traditional thoriated tungsten filament is 1600°C to 1900°C. Therefore, the energy consumption and life of the filament provided in the present application and the heating device made therefrom will be improved.

[0411] In summary:

[0412] The filament provided in the present application is prepared by adding one or more oxides and carbides or carbon elements of M to the tungsten matrix 100. The combination of the oxides and carbides or carbon elements can increase the diffusion rate of the material in the matrix 100. Compared with the thorium tungsten filament, it can achieve the same or even higher electron emission capability at a lower operating voltage (excitation temperature). At the same time, the grains of the carbide layer 200 are controlled within a certain small size range, and the channels 210 formed on the surface of the carbide layer 200 of the filament are organized to form a layered block. The first channel 211 and the second channel 212 and the edge of the filament are distributed in a quasi-vertical manner, which is conducive to the outward migration of rare earth atoms and the timely replenishment of rare earth elements evaporated from the surface, thereby improving the stability of the material emission. The tungsten alloy filament material provided by the present application replaces the existing thoriated tungsten filament cathode and has a lifespan comparable to or exceeding that of thoriated tungsten. The present application significantly reduces the initial recrystallization temperature of the material, improves the processing performance of the material, reduces the electron work function of the material, and refines the grain structure of the filament by doping M oxides and carbides or carbon element into the tungsten matrix 100 powder. This can reduce the filament breakage rate to reduce production and transportation costs, while effectively increasing the service life of the filament, so that its service life reaches and far exceeds the service life of existing thoriated tungsten filaments.

[0413] The filament provided in the present application can achieve an extremely high recrystallization temperature and can still obtain extremely fine grains at the same carburization temperature as thoriated tungsten. The material has excellent shock resistance and can reduce filament breakage and failure during production, transportation and use.

[0414] It should be noted that:

[0415] In this article, “~” is used to indicate a numerical range, and the range of this expression includes both endpoint values;

[0416] In summary, the specific parameters or some commonly used reagents or raw materials in the above embodiments are specific embodiments or preferred embodiments under the conception of this application, and are not intended to limit them; those skilled in the art can make adaptive adjustments within the conception and protection scope of this application.

[0417] It should be noted that the specific parameters or some commonly used reagents in the above embodiments are specific embodiments or preferred embodiments under the conception of this application, and are not intended to limit them; those skilled in the art may make adaptive adjustments within the conception and protection scope of this application.

[0418] In addition, unless otherwise specified, the raw materials used may also be conventional commercial products in the art, or may be prepared by conventional methods in the art.

[0419] In addition, 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 may be improved in only one or several aspects, without having to simultaneously solve all the technical problems listed in the prior art or background art. Those skilled in the art should understand that the absence of any content in a claim should not be construed as a limitation on that claim.

[0420] Although terms such as carbonized layer, matrix, and channel are frequently used herein, the possibility of using other terms is not excluded. These terms are used only to more conveniently describe and explain the essence of this application; interpreting them as any additional restrictions is contrary to the spirit of this application.

[0421] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A tungsten carbide alloy filament, characterized in that: It includes a substrate and a carbonized layer attached to the outer surface of the substrate; The grain width of the carbonized layer is between 1.0 μm and 15.0 μm; The components of the substrate and the carburized layer both contain tungsten, carbon, oxygen and M; The M element is selected from one or more combinations of La, Y, Sc, Nd, Sm, Lu, Ce, Gd, Tb, Dy, Ho, Pr, Er, Tm, Yb, Eu, Hf, and Zr; Wherein, the components of the tungsten carbide alloy filament do not contain thorium element.

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

3. The tungsten carbide alloy filament according to claim 1, characterized in that: A plurality of second channels are distributed on the carbonized layer, so that a layered structure stacked in a radial direction is formed on the cross section of the filament; A plurality of first channels are distributed on the carbonized layer, and at least part of the first channels are cross-arranged with the second channels, so that the layered structure is divided into a plurality of block structures.

4. The tungsten carbide alloy filament according to claim 1, characterized in that: A plurality of first channels are distributed on the carbonized layer; wherein at least part of the first channels are distributed along the radial direction of the cross section of the filament; and / or at least part of the first channels point to the center of the cross section of the filament; A plurality of second channels are distributed on the carbide layer; at least part of the second channels are distributed along the circumferential direction of the cross section of the tungsten alloy filament; wherein at least part of the second channels are cross-arranged with the first channels.

5. The tungsten carbide alloy filament according to claim 1, characterized in that: The carbonized layer comprises W2C and WC; the weight ratio of the W2C to the WC is (60-100):(0-40).

6. The tungsten carbide alloy filament according to claim 1, characterized in that: In the matrix, the M element exists in the form of oxide, and the carbon element exists in the form of carbide or carbon element.

7. The tungsten carbide alloy filament according to claim 1, characterized in that: The matrix comprises the following components: 0.0005-0.3 wt% of carbon element, 0.25-2.6 wt% of M element, 0.05-0.5 wt% of oxygen element, and the remainder is tungsten element and inevitable impurities.

8. The tungsten carbide alloy filament according to claim 7, characterized in that: 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 a single carbon substance; The oxide of M is selected from one or more combinations 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; The carbide is selected from one or more combinations of lanthanum carbide, zirconium carbide, yttrium carbide, hafnium carbide and tungsten carbide.

9. The tungsten carbide alloy filament according to claim 7, characterized in that: The components of the matrix further include a metal element T; the T is selected from at least one of K, Re, Mo, Fe, and Co.

10. The tungsten carbide alloy filament according to claim 9, characterized in that: The mass content of Re is less than 1000 ppm.

11. The tungsten carbide alloy filament according to claim 1, characterized in that: The wire diameter of the tungsten carbide alloy filament is 800 μm or less.

12. The tungsten carbide alloy filament according to claim 1, characterized in that: The working temperature of the tungsten carbide alloy filament is 1100°C to 1500°C.

13. The tungsten carbide alloy filament according to claim 1, characterized in that: The tungsten carbide alloy filament is a spiral structure, and the thickness of the carbide layer of at least one spiral turn reaches 30 μm to 90 μm.

14. A method for preparing a tungsten carbide alloy filament according to any one of claims 1 to 13, characterized in that: It includes the following steps: Doping and powder making: the finished powder raw material is obtained by sequentially performing the doping process, the reduction process and the powder making process; wherein the doping process is solid-liquid doping or solid-solid doping; Powder pressing: using isostatic pressing to press the finished powder raw material into a compact, and pre-sintering the compact at a low temperature in a hydrogen atmosphere to obtain a pre-sintered blank; High temperature sintering: sintering the pre-sintered billet at high temperature by a high temperature sintering method to obtain a sintered billet; Pressure processing: the sintered billet is processed into a tungsten alloy wire of a certain diameter; wherein, oxidation annealing treatment is performed during the thinning process; Cleaning: cleaning the tungsten alloy wire into tungsten alloy white wire; Winding: Winding the tungsten alloy white wire into a spring-shaped filament structure; Cathode assembly: assembling the spring-shaped filament structure and components, ceramics, and lead parts into a cathode structure through heat treatment; Welding: welding the filament structure in the cathode structure to the component end cap; Carbonization: Carbonizing the welded cathode structure.

15. The method for preparing a tungsten carbide alloy filament according to claim 14, characterized in that: The temperature rise curve of the high temperature sintering step is: From room temperature to A1, the heating time H1 is (5-8) h, A1 is (950-1250) °C; keep warm at A1 for H2 hours, H2 is (1-3); from A1 to A2, the heating time is H3, H3 is (1.5-2.5) h, A2 is (1300-1500) °C; keep warm at A2 for H4 hours, H4 is (2.5-4.5); from A2 to A3, heating time is H5, H5 is (1-3)h, A3 is (1700-1900)℃; keep warm at A3 for H6 hours, H6 is (1-3); heat from A3 to A4, heating time is H7, H7 is (1-3)h, A4 is (2050-2250)℃; keep warm at A4 for H8 hours, H8 is (5-10); cool naturally from A4 to obtain sintered billets; The process of the pressure processing step is: The sintered billet is refined to an intermediate specification wire with a diameter of 1.5 to 3.5 mm; and then the intermediate specification wire is oxidized and annealed at (1200 to 1500)° C. with an annealing speed of (3 to 10) m / min to obtain the tungsten alloy wire.

16. A heating device, characterized in that: It comprises the tungsten carbide alloy filament as described in any one of claims 1 to 13.

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