Tungsten alloy wire, preparation method therefor and use thereof, and tungsten carbide alloy filament

Abstract

A tungsten alloy wire, a preparation method therefor and a use thereof, and a tungsten carbide alloy filament. The tungsten alloy wire comprises the following components: 0.0005-0.3 wt% of a carbon element, 0.25-2.6 wt% of an M element, 0.05-0.5 wt% of an oxygen element and the balance being a tungsten element and inevitable impurities, and does not comprise a thorium element; and the initial recrystallization temperature of the tungsten alloy wire ranges from 48 %Fc to 56 %Fc, and / or the average size of 80 %Fc recrystallization grains is 1-15 μm. The tungsten alloy wire does not comprise the thorium element, does not cause radioactive contamination, has the initial recrystallization temperature ranging from 48 %Fc to 56 %Fc, and has the processing performance greatly improved compared with that of a thorium-containing tungsten wire; compared with a thorium-containing tungsten wire, the tungsten alloy wire has less flaw detection crack points, when the tungsten alloy wire is used as a substrate of a tungsten carbide alloy filament, grains of the carbonized substrate are fine, the filament is not easy to break in the production and use of a magnetron coil, and the production yield and quality are improved.

Description

Tungsten alloy wire, preparation method and use thereof, tungsten carbide alloy filament Technical Field

[0001] The present invention relates to the technical field of filament cathode materials, and in particular to a tungsten alloy wire, a preparation method and application thereof, and a tungsten carbide alloy filament. Background Art

[0002] 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:

[0003] 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.

[0004] 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.

[0005] In summary, traditional tungsten-thorium filaments are radioactive, not only polluting the environment but also potentially adversely affecting the health of those exposed to them. Furthermore, existing tungsten-thorium filaments suffer from a low recrystallization temperature, resulting in numerous cracks within a 100-meter length. The magnetron coils experience abnormal recrystallization growth during the carbonization process, leading to frequent breakage during production, use, and handling. This results in low product yields and poor quality. Solving these problems is a challenge that those skilled in the art are dedicated to overcoming.

[0006] Summary of the Invention

[0007] 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. Furthermore, the tungsten matrix of the existing thoriated tungsten filaments after carburization forms a fully recrystallized structure with coarse grains, which makes the filament prone to breakage during magnetron production and use. Furthermore, thoriated tungsten materials also suffer from poor processing performance and numerous wire defects. The present invention provides a tungsten alloy filament and a preparation method, the specific technical solutions of which are as follows:

[0008] The present invention provides a method for preparing tungsten alloy wire, and its technical solution is as follows:

[0009] The tungsten alloy comprises the following components: 0.005-0.3 wt% carbon, 0.25-2.6 wt% M element, 0.05-0.5 wt% oxygen element, and the balance is tungsten element and unavoidable impurities, and the composition does not contain thorium element; 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;

[0010] The preparation process of the tungsten alloy wire sequentially includes the steps of doping and powdering, powder pressing, sintering, and pressure processing; in the pressure processing step, the sintered tungsten alloy billet obtained after sintering is refined into an intermediate-gauge wire with a diameter of 1.5 to 3.5 mm; the intermediate-gauge wire is then subjected to oxidation annealing at (1200 to 1500)° C. at an annealing speed of (3 to 10) m / min; after oxidation annealing, the intermediate-gauge wire is further processed to the desired wire diameter to obtain the tungsten alloy wire;

[0011] The initial recrystallization temperature of the tungsten alloy wire is 48%Fc to 56%Fc, and / or the average size of the 80%Fc recrystallized grains is (1 to 15) μm.

[0012] In one embodiment, a high-temperature sintering method is adopted in the sintering step to obtain a tungsten alloy sintered billet; the temperature rising curve of the high-temperature sintering is: heating from room temperature to A1 at a certain rate, and keeping at A1 for a certain time; heating from A1 to A2, the heating time is H3; keeping at A2 for H4 hours; wherein, A1 is (950-1250)°C, H3 is (1.5-2.5)h, A2 is (1300-1500)°C, and H4 is (2.5-4.5); heating from A2 to A3 at a certain rate, A3 is (1700-1900)°C; keeping at A3 for a certain time; heating from A3 to A4 at a certain rate, A4 is (2050-2250)°C; keeping at A4 for a certain time; naturally cooling from A4, and the result is obtained.

[0013] In one embodiment, the heating curve of the high temperature sintering is as follows: from room temperature to A1, the heating time H1 is (5-8) h, A1 is (950-1250) ° C; keeping at A1 for H2 hours, H2 is (1-3); heating from A1 to A2, the heating time is H3, H3 is (1.5-2.5) h, A2 is (1300-1500) ° C; keeping 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); cooling naturally from A4, the result is obtained.

[0014] In some embodiments, the M element exists in the form of oxide, and the average size of the oxide particles in the tungsten alloy wire is (100-500) nm.

[0015] In some embodiments, the density of the tungsten alloy sintered billet is 17.5-18.3 g / cm 3 ; The average size of the oxide particles of the sintered tungsten alloy billet is less than 2.0 μm.

[0016] The present invention provides a tungsten alloy wire, comprising the following components: 0.0005-0.3wt% of carbon, 0.25-2.6wt% of the M element, 0.05-0.5wt% of oxygen, and the balance being tungsten and inevitable impurities, and the components do not contain thorium; wherein 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; the tungsten alloy wire has an initial recrystallization temperature of 48%Fc to 56%Fc, and / or an average recrystallized grain size at 80%Fc of the tungsten alloy wire is (1-15) μm.

[0017] In some embodiments, the M element exists in the form of oxide, and the average size of the oxide particles in the tungsten alloy wire is (100-500) nm.

[0018] In one embodiment, the M element exists in the form of an oxide, and the carbon element 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 one embodiment, the wire diameter of the tungsten alloy wire is 800 μm or less, and the number of crack points detected by flaw detection is less than 5 per 100 meters.

[0020] In one embodiment, the components of the tungsten alloy wire further include a T element; the T element is a metal element, and the T is selected from at least one of K, Re, Mo, Fe, and Co; and the mass content of Re in the tungsten alloy wire is less than 1000 ppm.

[0021] The present invention also provides a use of the tungsten alloy wire as described above. After the tungsten alloy filament is carbonized, it is used as a cathode alloy wire for a microwave heating device.

[0022] The present invention also provides a tungsten carbide alloy filament, which is obtained by carbonizing the above tungsten alloy wire.

[0023] Based on the above, compared with the prior art, the present invention has the following advantages:

[0024] The tungsten alloy wire of the present invention does not contain thorium and does not have the radioactive pollution problem of traditional thorium tungsten filaments;

[0025] The tungsten alloy wire of the present invention has a recrystallization temperature of 48%Fc to 56%Fc, and its processing performance is greatly improved compared with thoriated tungsten materials. Compared with thoriated tungsten materials, the wire provided by the present invention has fewer crack points during flaw detection. Moreover, the wire is applied as a substrate for tungsten carbide alloy filaments. After carburization, the tungsten substrate has fine grains, and the filament is not easily broken during the production and use of magnetron coils (i.e., filaments), thereby improving the production qualification rate and quality.

[0026] Other features and beneficial effects of the present invention will be described in the following description, and in part will become apparent from the description, or will be understood by practicing the present invention. The objectives and other beneficial effects of the present invention can be achieved and obtained by the structures particularly pointed out in the description, claims and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following is a brief introduction 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 invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0028] FIG1 is a schematic diagram of a partial structure of a carburized tungsten alloy filament provided by the present invention;

[0029] FIG2 is a schematic structural diagram of a cross section of a carburized tungsten alloy filament provided by the present invention;

[0030] FIG3 is a schematic structural diagram of a longitudinal section of a carburized tungsten alloy filament provided by the present invention;

[0031] Figure 4 is an enlarged view of point A in Figure 2;

[0032] FIG5 is a partial structural schematic diagram of a cross section of a carburized tungsten alloy filament provided by the present invention;

[0033] FIG6 is a metallographic image of Comparative Example 1 provided by the present invention at 44% FC;

[0034] FIG7 is a metallographic image of Comparative Example 1 provided by the present invention at 46% FC;

[0035] FIG8 is a metallographic image of Comparative Example 1 provided by the present invention at 48% FC;

[0036] FIG9 is a metallographic image of Comparative Example 1 provided by the present invention at 50% FC;

[0037] FIG10 is a metallographic image of Example 1 provided by the present invention at 48% FC;

[0038] FIG11 is a metallographic image of Example 1 provided by the present invention at 50% FC;

[0039] FIG12 is a metallographic image of Example 1 provided by the present invention at 52% FC;

[0040] FIG13 is a schematic diagram of the crystal structure of Comparative Example 1 provided by the present invention;

[0041] FIG14 is a schematic diagram of the crystal structure of Example 1 provided by the present invention;

[0042] FIG15 is a diagram illustrating the channel distribution in a cross section of Example 1 provided by the present invention;

[0043] FIG16 is a diagram illustrating the channel distribution in a longitudinal section of Example 1 provided by the present invention;

[0044] FIG17 is a diagram illustrating the channel distribution in the cross section of Comparative Example 1 provided by the present invention;

[0045] FIG18 is a schematic diagram of a process flow for preparing a heating device from a tungsten alloy wire according to the present invention;

[0046] FIG19 is a graph showing the conversion relationship between FC% and degrees Celsius;

[0047] FIG20 is a schematic diagram showing the principle of the high-temperature sintering process.

[0048] Reference Signs: 100 Base body 200 Carbonized layer 210 Channel 220 Filament outer edge 211 First channel 212 Second channel DETAILED DESCRIPTION

[0049] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments; the technical features designed in different implementation modes of the present invention described below can be combined with each other as long as they do not conflict with each other; based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0050] In the description of the present invention, it should be noted that all terms used in the present invention (including technical terms and scientific terms) have the same meanings as those generally understood by ordinary technicians in the field to which the present invention belongs, and should not be understood as limiting the present invention; it should be further understood that the terms used in the present invention should be understood to have meanings consistent with the meanings of these terms in the context of this specification and in the relevant fields, and should not be understood in an idealized or overly formal sense, unless explicitly defined as such in the present invention.

[0051] The present invention provides a tungsten alloy wire, and its technical solution is as follows:

[0052] The tungsten alloy comprises the following components: 0.0005-0.3 wt% of carbon, 0.25-2.6 wt% of the M element, 0.05-0.5 wt% of oxygen, and the balance being tungsten and unavoidable impurities, and does not contain thorium; wherein 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; 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.

[0053] The initial recrystallization temperature of the tungsten alloy wire is 48%Fc to 56%Fc, and / or the average size of the 80%Fc recrystallized grains is (1 to 15) μm.

[0054] For component composition:

[0055] The present invention adds one or more oxides of M and carbon elements. Since the oxides of M and carbides in the tungsten matrix react at high temperatures (the operating temperature of the tungsten carbide alloy filament is a high temperature condition), 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.

[0056] In summary, compared to thoriated tungsten filaments, the present invention combines M oxide with carbon (carbide or carbon element), which can achieve the same or even higher electron emission capability as thoriated tungsten at a lower operating voltage (excitation temperature). It also makes it easier to ensure the balance between rare earth atom loss and migration replenishment in the filament carbide layer, thereby ensuring the stability of electron emission from the filament.

[0057] For the onset recrystallization temperature characteristics:

[0058] The initial recrystallization temperature of the tungsten alloy wire provided by the present invention is higher than that of the thoriated tungsten wire, which is 48%Fc to 56%Fc in the present application, while the recrystallization temperature of thoriated tungsten is around 46%FC (2020°C).

[0059] The average size of the 80% Fc recrystallized grains of the tungsten alloy wire provided by the present invention is finer than that of the thoriated tungsten wire. The average size of the 80% Fc recrystallized grains of the tungsten alloy wire of 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.

[0060] The above characteristics of high 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 invention finer than that of thorium tungsten filament after carburization in the magnetron;

[0061] There is a carbonization process in the process of preparing tungsten alloy wire into carbonized layer filament. The carbonization temperature is 2000-2500℃. The original thoriated tungsten filament is carbonized at this temperature (analysis shows that the reason is that its initial recrystallization temperature is too low). The grain structure will show recrystallization phenomenon, and the grains are coarse. As a result, the filament is brittle and has poor seismic performance after carbonization. It is very easy to break the wire during the assembly, production, transportation and subsequent use of the microwave oven of the magnetron.

[0062] Compared with thoriated tungsten filaments, the filament material produced by the present invention has a higher initial recrystallization temperature than the original thoriated tungsten filament, and the average size of 80% Fc recrystallized grains is smaller than that of the original thoriated tungsten filament. After carbonization, the tungsten alloy filament of the present invention still has a fine-grained structure, and is less brittle than the traditional thoriated tungsten filament material. The tungsten alloy filament with a fine-grained structure has better seismic resistance than the thoriated tungsten filament. The filament breakage rate of the magnetron produced by the present invention is much lower than that of the magnetron produced by traditional thoriated tungsten.

[0063] 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.

[0064] 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.

[0065] Regarding 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.

[0066] The average size of the oxide particles of the tungsten alloy wire of the present application is (100-500) nm.

[0067] The reason for controlling the oxide particle size of the tungsten alloy wire within the specified range is that the oxide particle size of the tungsten alloy wire determines the oxide particle size of the filament after carbonization. If the oxide particles of the wire material are too coarse relative to the specified range, it will be more difficult for the oxide particles of M to migrate to the filament surface during magnetron operation. This will make 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.

[0068] 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.

[0069] The present invention also provides a preferred embodiment of a method for preparing tungsten alloy wire that achieves the above parameters of the recrystallization temperature range and the average size range of oxide particles:

[0070] It includes the following steps:

[0071] 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;

[0072] 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;

[0073] Step 3: High temperature sintering: Use high temperature sintering or vertical melting sintering to obtain a density of 17.5-18.3g / cm 3 Sintering the billet to obtain the tungsten alloy material in billet form;

[0074] The heating curve of the high temperature sintering is:

[0075] From room temperature to A1, the heating time H1 is (5-8) h, and A1 is (950-1250) °C;

[0076] 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.;

[0077] Keep warm at A1 for H2 hours, H2 is (1~3);

[0078] For example, H2 is (1-2)h, (2-3)h, etc., and another example is 1.5h, 2.5h, etc.;

[0079] From A1 to A2, the heating time is H3, H3 is (1.5~2.5)h, A2 is (1300~1500)℃;

[0080] 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 (1300-1400)℃, (1400-1500)℃, etc., and another example is 1350℃, 1500℃, etc.;

[0081] Keep warm at A2 for H4 hours, H4 is (2.5~4.5);

[0082] For example, H4 is (2.5-3.0)h, (3.0-4.0)h, etc., and another example is 2.8h, 3.5h, etc.;

[0083] From A2 to A3, the heating time is H5, H5 is (1-3) h, and A3 is (1700-1900) °C;

[0084] 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.;

[0085] Keep warm at A3 for H6 hours, H6 is (1~3);

[0086] For example, H6 is (1-2)h, (2-3)h, etc., and another example is 1.5h, 2.5h, etc.;

[0087] From A3 to A4, the heating time is H7, H7 is (1-3)h, A4 is (2050-2250)℃;

[0088] 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.;

[0089] Keep warm under A4 for H8 hours, H8 is (5-10);

[0090] For example, H8 is (5-7)h, (7-10)h, etc., and another example is 6h, 8h, etc.;

[0091] It is obtained by natural cooling from A4.

[0092] Step 4: Pressure processing:

[0093] 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;

[0094] 4.2 The intermediate gauge wire is then subjected to oxidation annealing at (1200-1500)°C, with an annealing speed of (3-10) m / min; 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 is (1200-1350)°C, (1350-1500)°C, etc., and another example is 1250°C, 1400°C, etc.;

[0095] 4.3 After oxidation annealing, the intermediate wire is processed to the required wire diameter to obtain tungsten alloy wire (also known as black wire). The thinning process is carried out by multiple rotary forging and drawing. The oxidation annealing process is carried out in the oxidation annealing equipment. The annealing speed refers to the speed at which the wire passes through the annealing tank, which represents the length of the wire passing through the annealing tank per unit time.

[0096] Step 5: Cleaning the white wire: Use electrolytic cleaning to clean the tungsten alloy wire into a tungsten alloy white wire that can be processed into the filament of a microwave heating device.

[0097] Step 6. Winding: Wind the white wire into a spring-shaped filament structure for heating devices to obtain tungsten alloy wire.

[0098] Important control points for the preferred embodiment of the preparation method:

[0099] (1) Oxidation annealing treatment of intermediate specification products:

[0100] 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.

[0101] (2) By controlling the time from A1 to A2 and the sintering time at A2 (1300-1500°C) during the sintering process:

[0102] During the high-temperature sintering stage of the tungsten blank, the present invention 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 blank is allowed to grow rapidly, closing the pores and preventing oxide particles in the pores from being squeezed into another pore from the unsealed connecting channel during the shrinkage of the sintering cavity of the billet. 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.

[0103] 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.

[0104] 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. Further refined tungsten alloy wires also have a relatively coarse average oxide particle size (approximately 500-900 nm).

[0105] The mechanism by which the sintering process affects the size of oxides in the billet, tungsten alloy wire, and carbonized filament, as well as the effect of the size of oxides in the tungsten alloy wire and carbonized filament on the filament performance is as follows:

[0106] The reason for controlling oxide particle size within a narrow range is that the oxide particle size of the billet directly determines the oxide size of the tungsten alloy wire or filament after carbonization. If the wire oxide particles are coarser, it will be more difficult for the particles to migrate to the filament surface during magnetron operation. This will make it easier to disrupt the balance between rare earth element loss and replenishment on the filament surface, resulting in more unstable magnetron electron emission.

[0107] Adjustment of the sintering process affects the speed of sintering neck growth and pore closure of the tungsten billet. The sintering process provided can reduce the possibility of oxide particle aggregation, thereby reducing the oxide particle size of the sintered billet. As shown in Figure 20, the specific principle of the high-temperature sintering process is explained as follows:

[0108] The isostatically pressed green compact is a dense accumulation of powder with a porosity of about 35-45%. We can simply imagine these pores as holes with multiple channels connecting them, and the oxide particles are evenly distributed on the inner surface of the holes.

[0109] During high-temperature sintering, the bonded tungsten particles form "sintering necks." As the sintering temperature increases, the sintering necks continue to grow and block the channels connecting the cavities, resulting in isolated cavities. These isolated cavities gradually become rounded, reducing the internal surface area of ​​the cavities. This in turn causes similarly sized small oxide particles to aggregate together to form larger oxide particles. As high-temperature sintering progresses, the cavities further shrink through diffusion, forcing the oxide particles distributed on the inner surface of the cavities to further aggregate, forming one or several larger oxide particles.

[0110] 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.

[0111] 1. Preferred component characteristics for tungsten alloy wire:

[0112] (1) Preferably, the tungsten alloy wire is composed of 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 remainder is tungsten element and inevitable impurities.

[0113] 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.

[0114] (2) 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 carbon element is present in the tungsten alloy material in the form of carbide or carbon element, and 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.

[0115] Preferably, the components of the tungsten alloy material further include T, wherein T is a solid solution metal element or a dispersed metal element, and the 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.

[0116] It should be noted that:

[0117] “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.

[0118] 2. Preferred structural features of the above tungsten alloy wire:

[0119] (1) The diameter of the above-mentioned tungsten alloy wire can be up to 800 μm:

[0120] In the pressure processing process, the tungsten alloy wire provided by the present invention has good processing performance and can be processed into wires with fine wire diameter specifications (i.e., fine wire diameter tungsten alloy wire), and the wire diameter tolerance can be controlled within a very small range.

[0121] Furthermore, the wire diameter of tungsten alloy wire can reach 600μm or less, 550μm or less, or even 500μm or less. The wire diameter of tungsten alloy wire can be 450-550μm, such as 470μm, 490μm, 500μm, 520μm, etc., or 700-800μm, such as 750μm, 760μm, 780μm, etc.

[0122] (2) The number of crack points detected by flaw detection of the tungsten alloy wire is less than 5 (per 100 meters). Furthermore, 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, etc.

[0123] Tungsten alloy wire has fewer crack points during inspection, a high filament yield rate, and is not prone to wire breakage.

[0124] 3. After carbonization treatment, tungsten alloy wire can be obtained as tungsten carbide alloy filament. The present invention also provides the following preferred embodiments of the method for preparing tungsten carbide alloy filament:

[0125] Step 1, cathode assembly: assemble the spring-shaped filament structure with components, ceramics, lead pieces and other parts into a cathode structure through heat treatment;

[0126] Step 2, welding: weld the filament structure in the cathode structure and the component end cap together;

[0127] Step 3, carbonization: placing the cathode structure in a carbonization tank for carbonization, introducing carbon-containing hydrocarbon gas after exhausting, and passing a direct current of a certain current value through the cathode structure for heating, so that the filament structure is carbonized in the hydrocarbon gas. After the filament structure is carbonized, the tungsten alloy filament is formed;

[0128] Step 4, white ball assembly: Assemble the cathode structure, anode cylinder, antenna end cap and other components together;

[0129] Step 5: Blackening treatment: exhaust the white ball, evacuate the ball, and perform high-temperature aging to complete the black ball manufacturing and activation of the emission performance;

[0130] Step 6: Assemble the heating device: Assemble the black ball, heat sink, magnet, tube shell, etc. to finally obtain the heating device component containing the above-mentioned tungsten alloy filament. In this way, the obtained heating device component can be installed in the equipment (such as a microwave oven) for use.

[0131] The tungsten alloy filament carbonized by the present invention is shown in FIG1-5 : it includes a substrate 100 and a carbonized layer 200 covering the outer periphery of the substrate 100; channels 210 are distributed on the carbonized layer 200, and the channels include a first channel 211 and a second channel 212;

[0132] At least some of the first channels 211 are distributed radially along the cross section of the filament; and / or at least some of the first channels 211 are directed toward the center of the cross section of the filament. The second channels 212 divide the carbonized layer 200 into a radially stacked layer structure, and the first channels 211 intersecting the second channels 212 divide the carbonized layer 200 into a block structure, forming a block-like structure.

[0133] It should be noted that:

[0134] 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 pointing toward the center of the cross section of the filament" are used herein. Regarding the radial distribution and pointing toward the center of the circle, this means that the endpoint of the first channel 211 near the substrate 100 and the endpoint near the filament edge are connected to form a first straight line, 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.

[0135] As shown in FIG5 , the “circumferential distribution along the cross section of the tungsten alloy filament” mentioned herein refers to connecting the endpoints of the second channel 212 to form a second straight line, where the angle between the second straight line and the straight line where the filament is radially located is (-45 to +45) degrees.

[0136] In the present invention, the first channel 211 is quasi-vertical and quasi-radially distributed to the outer edge 220 of the filament (i.e., the outer edge of the carbonized layer 200), but this 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).

[0137] In the present invention, 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 as to divide the carbonized layer 200 into a layered structure stacked in the radial direction.

[0138] The present invention also provides the following embodiments and comparative examples:

[0139] The weight formula of the raw material components and the element ratio of the prepared filament materials of the embodiments and comparative examples provided by the present invention are shown in Table 1 below:

[0140] Table 1

[0141] 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:

[0142] Example 1

[0143] 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.

[0144] 2. Evacuate the doping pot and heat it with water (heating temperature 80°C, vacuum degree -0.025MPa), stirring while heating;

[0145] 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;

[0146] 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;

[0147] 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;

[0148] 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.

[0149] 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:

[0150] From room temperature to A1, the heating time H1 is 6h, and A1 is 1100℃; keep warm at A1 for H2 hours, H2 is 2; heat up from A1 to A2, the heating time is H3, H3 is 2h, and A2 is 1400℃; keep warm at A2 for H4 hours, H4 is 3.5; heat up from A2 to A3, the heating time is H5, H5 is 2h, and A3 is 1800℃; keep warm at A3 for H6 hours, H6 is 2; heat up from A3 to A4, the heating time is H7, H7 is 2h, and A4 is 2100℃; keep warm at A4 for H8 hours, H8 is 6; cool naturally from A4, and you're done.

[0151] Among them, by controlling the medium frequency sintering time, the pore closing and shrinking speed of the billet is controlled, so as to obtain the oxide particle size <2.0μm and density 18.0g / cm 3 sintered billets.

[0152] 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 machine 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.

[0153] 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.

[0154] 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;

[0155] 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;

[0156] 11. Assemble the filament, components, ceramics, lead pieces and other parts into the cathode structure through heat treatment at a temperature of 600°C.

[0157] 12. Weld the filament in the cathode structure to the end cap of the assembly.

[0158] 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.

[0159] 14. White ball assembly: Assemble the cathode structure, anode cylinder, antenna end cap and other components together.

[0160] 15. The white ball is evacuated and aged at high temperature to complete the production of the black ball and activate its launch performance.

[0161] 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.

[0162] Example 2

[0163] 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.

[0164] 2. Evacuate the doping pot and heat it with water (heating temperature 80°C, vacuum degree -0.025MPa), stirring while heating;

[0165] 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;

[0166] 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℃;

[0167] 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;

[0168] 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.

[0169] 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:

[0170] From room temperature to A1, the heating time H1 is 5h, A1 is 950℃; keep warm at A1 for H2 hours, H2 is 3; from A1 to A2, the heating time is H3, H3 is 1.5h, A2 is 1300℃;

[0171] Keep warm at A2 for H4 hours, H4 is 4.5; heat up from A2 to A3, the heating time is H5, H5 is 1h, A3 is 1700℃; keep warm at A3 for H6 hours, H6 is 3; heat up from A3 to A4, the heating time is H7, H7 is 1h, A4 is 2050℃; keep warm at A4 for H8 hours, H8 is 10; cool naturally from A4, and you have it.

[0172] 8. The 17 mm diameter sintered billet was processed into a 2.0 mm wire using multiple passes of rotary forging and drawing, and then subjected to oxidation annealing on an oxidation annealing device 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.

[0173] 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;

[0174] 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;

[0175] 11. Assemble the filament, components, ceramics, lead pieces and other parts into the cathode structure through heat treatment at a temperature of 600°C.

[0176] 12. Weld the filament in the cathode structure to the end cap of the assembly.

[0177] 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.

[0178] 14. White ball assembly: Assemble the cathode structure, anode cylinder, antenna end cap and other components together.

[0179] 15. The white ball is evacuated and aged at high temperature to complete the production of the black ball and activate its launch performance.

[0180] 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.

[0181] Example 3

[0182] 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.

[0183] 2. Evacuate the doping pot and heat it with water (heating temperature 80°C, vacuum degree -0.025MPa), stirring while heating;

[0184] 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;

[0185] 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℃;

[0186] 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;

[0187] 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.

[0188] 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:

[0189] From room temperature to A1, the heating time H1 is 8h, A1 is 1250℃; keep warm at A1 for H2 hours, H2 is 1; from A1 to A2, the heating time is H3, H3 is 2.5h, A2 is 1500℃;

[0190] 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.

[0191] 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 machine 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.

[0192] 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.

[0193] 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;

[0194] 11. Assemble the filament, components, ceramics, lead pieces and other parts into the cathode structure through heat treatment at a temperature of 600°C.

[0195] 12. Weld the filament in the cathode structure to the end cap of the assembly.

[0196] 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.

[0197] 14. White ball assembly: Assemble the cathode structure, anode cylinder, antenna end cap and other components together.

[0198] 15. The white ball is evacuated and aged at high temperature to complete the production of the black ball and activate its launch performance.

[0199] 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.

[0200] Example 4

[0201] 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.

[0202] 2. Evacuate the doping pot and heat it with water (heating temperature 80°C, vacuum degree -0.025MPa), stirring while heating;

[0203] 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.

[0204] 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;

[0205] 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;

[0206] 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.

[0207] 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;

[0208] 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;

[0209] 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;

[0210] 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;

[0211] 11. Assemble the filament, components, ceramics, lead pieces and other parts into the cathode structure through heat treatment at a temperature of 600°C.

[0212] 12. Weld the filament in the cathode structure to the end cap of the assembly.

[0213] 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.

[0214] 14. White ball assembly: Assemble the cathode structure, anode cylinder, antenna end cap and other components together.

[0215] 15. The white ball is evacuated and aged at high temperature to complete the production of the black ball and activate its launch performance.

[0216] 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.

[0217] Example 5

[0218] 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.

[0219] 2. Evacuate the doping pot and heat it with water (heating temperature 80°C, vacuum degree -0.025MPa), stirring while heating;

[0220] 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.

[0221] 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;

[0222] 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;

[0223] 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.

[0224] 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;

[0225] 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;

[0226] 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;

[0227] 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;

[0228] 11. Assemble the filament, components, ceramics, lead pieces and other parts into the cathode structure through heat treatment at a temperature of 600°C.

[0229] 12. Weld the filament in the cathode structure to the end cap of the assembly.

[0230] 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.

[0231] 14. White ball assembly: Assemble the cathode structure, anode cylinder, antenna end cap and other components together.

[0232] 15. The white ball is evacuated and aged at high temperature to complete the production of the black ball and activate its launch performance.

[0233] 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.

[0234] Example 6

[0235] 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.

[0236] 2. Evacuate the doping pot and heat it with water (heating temperature 80°C, vacuum degree -0.025MPa), stirring while heating;

[0237] 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.

[0238] 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;

[0239] 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;

[0240] 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.

[0241] 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;

[0242] 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;

[0243] 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;

[0244] 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;

[0245] 11. Assemble the filament, components, ceramics, lead pieces and other parts into the cathode structure through heat treatment at a temperature of 600°C.

[0246] 12. Weld the filament in the cathode structure to the end cap of the assembly.

[0247] 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.

[0248] 14. White ball assembly: Assemble the cathode structure, anode cylinder, antenna end cap and other components together.

[0249] 15. The white ball is evacuated and aged at high temperature to complete the production of the black ball and activate its launch performance.

[0250] 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.

[0251] Example 7

[0252] 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.

[0253] 2. Evacuate the doping pot and heat it with water (heating temperature 80°C, vacuum degree -0.025MPa), stirring while heating;

[0254] 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;

[0255] 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;

[0256] 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.

[0257] 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;

[0258] 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;

[0259] 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.

[0260] 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;

[0261] 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;

[0262] 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;

[0263] 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;

[0264] 13. Assemble the filament, components, ceramics, lead pieces and other parts into a cathode structure through heat treatment at a temperature of 600°C.

[0265] 14. Weld the filament in the cathode structure to the end cap of the assembly.

[0266] 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.

[0267] 16. White ball assembly: Assemble the cathode structure, anode cylinder, antenna end cap and other components together.

[0268] 17. The white ball is evacuated and aged at high temperature to complete the production of the black ball and activate its launch performance.

[0269] 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.

[0270] Comparative Example 1:

[0271] 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.

[0272] 2. Evacuate the doping pot and heat it with water (heating temperature 80°C, vacuum degree -0.025MPa), stirring while heating;

[0273] 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;

[0274] 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;

[0275] 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.

[0276] 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.

[0277] 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;

[0278] 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;

[0279] 98. Use electrolytic cleaning to clean 0.52mm black wire into 0.50mm±0.005mm thoriated tungsten alloy white wire that can be processed into microwave oven heating device filament;

[0280] 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;

[0281] 11. Assemble the filament, components, ceramics, lead pieces and other parts into the cathode structure through heat treatment at a temperature of 600°C.

[0282] 12. Weld the filament in the cathode structure to the end cap of the assembly.

[0283] 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.

[0284] 14. White ball assembly: Assemble the cathode structure, anode cylinder, antenna end cap and other components together.

[0285] 15. The white ball is evacuated and aged at high temperature to complete the production of the black ball and activate its launch performance.

[0286] 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.

[0287] Comparative Example 2:

[0288] 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 in the doping pot and stir. The ratio of lanthanum nitrate-yttrium nitrate solution to ammonia NH3·H2O solution is 5:1.

[0289] 2. Evacuate the doping pot and heat it with water (heating temperature 80°C, vacuum degree -0.025MPa), stirring while heating;

[0290] 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;

[0291] 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;

[0292] 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;

[0293] 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.

[0294] 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;

[0295] 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;

[0296] 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;

[0297] 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;

[0298] 11. Assemble the filament, components, ceramics, lead pieces and other parts into the cathode structure through heat treatment at a temperature of 600°C.

[0299] 12. Weld the filament in the cathode structure to the end cap of the assembly.

[0300] 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.

[0301] 14. White ball assembly: Assemble the cathode structure, anode cylinder, antenna end cap and other components together.

[0302] 15. The white ball is evacuated and aged at high temperature to complete the production of the black ball and activate its launch performance.

[0303] 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.

[0304] Comparative Example 3:

[0305] 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.

[0306] 2. Evacuate the doping pot and heat it with water (heating temperature 80°C, vacuum degree -0.025MPa), stirring while heating;

[0307] 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.

[0308] 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;

[0309] 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;

[0310] 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.

[0311] 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;

[0312] 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;

[0313] 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;

[0314] 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;

[0315] 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.

[0316] 12. Weld the filament in the cathode structure to the end cap of the assembly.

[0317] 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.

[0318] 14. White ball assembly: Assemble the cathode structure, anode cylinder, antenna end cap and other components together.

[0319] 15. The white ball is evacuated and aged at high temperature to complete the production of the black ball and activate its launch performance.

[0320] 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.

[0321] Comparative Example 4

[0322] 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.

[0323] 2. Evacuate the doping pot and heat it with water (heating temperature 80°C, vacuum degree -0.025MPa), stirring while heating;

[0324] 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;

[0325] 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;

[0326] 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.

[0327] 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;

[0328] 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;

[0329] 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.

[0330] 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;

[0331] 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;

[0332] 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;

[0333] 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;

[0334] 13. Assemble the filament, components, ceramics, lead pieces and other parts into a cathode structure through heat treatment at a temperature of 600°C.

[0335] 14. Weld the filament in the cathode structure to the end cap of the assembly.

[0336] 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.

[0337] 16. White ball assembly: Assemble the cathode structure, anode cylinder, antenna end cap and other components together.

[0338] 17. The white ball is evacuated and aged at high temperature to complete the production of the black ball and activate its launch performance.

[0339] 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.

[0340] Comparative Example 5

[0341] The difference between this comparative example and Example 1 is only that:

[0342] In this comparative example, a 17 mm diameter sintered billet was directly processed into a 0.52 mm ± 0.005 mm diameter tungsten-lanthanum-tungsten alloy black wire in multiple swaging and drawing steps. Intermediate wire diameters were not subjected to the oxidation annealing step. Other processes and process conditions were consistent with those in Example 1.

[0343] Comparative Example 6

[0344] The difference between this comparative example and Example 1 is only that:

[0345] In this comparative example, the high-temperature sintering temperature curve is as follows: from room temperature to A1, the heating time H1 is 6 hours, and A1 is 1100°C; holding at A1 for H2 hours, H2 for 2 hours; heating from A1 to A2, the heating time H3, H3 for 3 hours, and A2 for 1400°C; holding at A2 for H4 hours, H4 for 2 hours; heating from A2 to A3, the heating time H5, H5 for 2 hours, and A3 for 1800°C; holding at A3 for H6 hours, H6 for 2 hours; heating from A3 to A4, the heating time H7, H7 for 2 hours, and A4 for 2100°C; holding at A4 for H8 hours, H8 for 6 hours; and natural cooling from A4. The other processes and process conditions are the same as those in Example 1.

[0346] 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 Tables 2-7 below:

[0347] Table 2

[0348] Table 3

[0349] Note: The yield rate statistics refer to the yield rate from billet to finished filament.

[0350] Table 4

[0351] Table 5 Data comparison table of Example 1, Comparative Example 1 (Thorium Tungsten) and Comparative Examples 5-6

[0352] Table 6 Comparison of the results of Example 1 and Comparative Example 6

[0353] Table 7 Comparison of the results of Example 1 and Comparative Example 7

[0354] In Table 2-7, 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 19, Article 4.3.2.2 of the high-temperature performance test method of GB / T23272-2009 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 18.

[0355] 1. Comparing Example 1 and Comparative Example 1, the thoriated tungsten filament in Comparative Example 1 has an initial recrystallization temperature lower than the specified range of this application:

[0356] Figures 6-12 show the metallographic structures of Example 1 and Comparative Example 1 at different fusing currents. It is apparent 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 invention is higher than that of the existing thoriated tungsten filament.

[0357] 1.1. The influence of the recrystallization starting temperature on the grain width of the carbide layer 200

[0358] The grain size of the filament after carbonization in Example 1 and Comparative Example 1 is shown in Figures 13-14: Figure 14 shows that the filament structure after carbonization in Example 1 is still fine-grained, while Figure 13 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, while that of Comparative Example 1 is 9.81 μm.

[0359] 1.2. The initial recrystallization temperature affects the grain width of the tungsten alloy filament, thereby affecting the channel distribution of the carbide layer 200, and thus affecting the emission performance:

[0360] The distribution of channels 210 of the carbonized filaments in Example 1 and Comparative Example 1 is shown in Figures 15-17. Figure 15 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 16 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 17 shows that the number of first channels 211 that are perpendicular to the filament edge distributed in the cross-section of the carbonized layer 200 of the filament in Comparative Example 1 is significantly reduced, and a 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.

[0361] In Example 1 of the present invention, 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.

[0362] 1.3. The initial recrystallization temperature affects the grain width of the tungsten carbide alloy filament, thus affecting the wire breakage rate, etc.:

[0363] The recrystallization temperature of a thoriated tungsten filament is relatively low. After carbonization, the recrystallized grains of the tungsten matrix in the filament become coarse, making the filament brittle. This results in poor seismic performance of the magnetron and makes the filament more prone to breakage, which can cause the magnetron to malfunction. The data from Comparative Example 1 clearly shows that the breakage rate and operating performance of the thoriated tungsten filament are significantly worse than those of Example 1.

[0364] Similarly, when the recrystallization temperature of the tungsten alloy wire of the present application is lower than the specified range of the present application (48%Fc~56%Fc), the recrystallized grains of the tungsten matrix of the filament will be coarser after the filament is carburized, and the filament will be brittle, resulting in poor seismic performance of the magnetron, more likely to break the filament, and the breakage rate will be worse than that of the embodiment.

[0365] 2. Comparison of Example 2 and Comparative Example 2, Example 4 and Comparative Example 3:

[0366] 2.1 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; comparing the results of the two, it can be seen that: compared with Example 2, the recrystallization temperature of Comparative 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.

[0367] 2.2 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.

[0368] Analysis of its mechanism is that: in the embodiment of the present invention, by adding one or more M oxides and carbides or carbon elements, the M oxides and carbides in the tungsten matrix will react at high temperature, and the generated M metal atoms are much smaller than the particles of M oxides. The migration and diffusion speed of M metal atoms in the tungsten matrix will increase. 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 materials are added to comparative examples 2-3, the above effect cannot be achieved, and its electron emission performance deteriorates.

[0369] 4. Comparative Example 7 and Comparative Example 4:

[0370] The difference between Example 7 and Comparative Example 4 is that the Re content in Comparative Example 4 exceeds the specified range of this application. A comparison of the two results shows that the operating temperature of Comparative Example 4 is higher and the service life is shorter. The inventors analyze that rhenium has the functions 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 seen in the wire flaw detection data: Example 7 has a crack count of 0.8-1.5 per 100 meters, while Comparative Example 5 has a crack count of 6-10 per 100 meters.

[0371] 5. Comparative Example 1 and Comparative Examples 5-6:

[0372] 5.1. Compared to Example 1, the onset recrystallization temperature of Comparative Example 5 is higher than the specified range of this application: Compared to Example 1, Comparative Example 5 did not use oxidative annealing to control the onset recrystallization temperature of the tungsten alloy wire within a certain range. As a result, the onset recrystallization temperature of Comparative Example 5 was higher (higher than the specified range of this application), the number of crack points per 100 meters increased, and the yield rate decreased. This shows that simply increasing the onset recrystallization temperature does not necessarily lead to better results; exceeding the specified range of this application can also have adverse effects.

[0373] 5.2. Comparing Example 1 and Comparative Example 6, the average size of the oxide particles in Comparative Example 6 exceeds the range specified in this application: Compared with Example 1, the average size of the oxide particles in the billet in Comparative Example 6 becomes larger, and the average size of the oxide particles in the 0.5 mm wire cross section becomes larger. The size of the oxide particles will affect the processing performance, that is, the processing yield and the level of flaw detection. Therefore, the number of crack points per 100 meters of the wire produced in this comparative example increases, and the yield decreases.

[0374] In summary, it can be clearly concluded from the test results of the embodiments and comparative examples that:

[0375] 1. 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, which makes the filament very easy to break after carbonization. If the vibration in the production process is slightly larger, the wire will break (the wire breakage rate is about 20,000-30,000 ppm).

[0376] 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 invention 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 invention is significantly smaller than that of the comparative example). The fine-grained filament is less susceptible to breakage.

[0377] 2. Observation of the cross-sectional structure, longitudinal cross-sectional structure, and the carbonized layer 200 of the longitudinal planed cross-sectional structure revealed that the recrystallization temperature of the tungsten alloy wire of the present invention is controlled within a certain range, and its initial recrystallization temperature is higher than that of the original thoriated tungsten wire. After carbonization, the filament structure remains fine-grained.

[0378] Compared to thoriated tungsten filaments, the carbide layer 200 of the thoriated tungsten-free lanthanum filament of the present invention 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 the present invention. The carbide layer 200 at different locations in the filament provided by the present invention has an organization similar to the intersection 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 filament of the present invention has stable emission performance comparable to that of traditional thoriated tungsten filaments. It can be seen that the tungsten carbide alloy material of the present invention 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, it can also achieve the stable emission capability of traditional thorium-free tungsten filaments, solving the problem of poor stable emission capability of existing tungsten filaments without thorium, and does not have the radioactive pollution problem of traditional thorium-free tungsten filaments.

[0379] 3. The test results clearly show that the filament material of the present invention has better processing performance than the existing thoriated tungsten, with fewer cracks during flaw detection (less than 2 cracks per 100 meters for a filament diameter of 500 μm), a higher processing yield, and a less prone to wire breakage, thereby improving production efficiency. Furthermore, the fewer cracks in the wire material, the less likely the filament will break during carbonization.

[0380] 4. The electron emission performance parameters in the test results clearly indicate that the DC emission capability of the heater device made from the filament of the present invention is nearly double that of the thoriated tungsten filament (Comparative Example 1), enabling the heater device made from the filament of the present invention to excite electrons at a lower voltage (Note: Based on the usage of heater devices in this field, the starting voltage of the thoriated tungsten heater device must be at least 2.0V. To ensure starting voltage, the operating voltage is set at 3.3V. In Example 1, the starting voltage is 1.4V, and the operating voltage can be in the range of 1.6 to 1.8V).

[0381] The operating temperature of the heating device of the present invention can be reduced from 1500-1600°C to 1100-1500°C, such as 1200-1300°C, while the operating temperature of the traditional thoriated tungsten filament is 1600-1900°C. Therefore, the energy consumption and life of the heating device provided by the present invention are improved.

[0382] In summary, the technical solution provided by the present invention includes at least the following working principles or mechanisms and beneficial effects:

[0383] (1) The present invention dopes the tungsten matrix powder with oxides and carbides of M and controls the initial recrystallization temperature of the material so that extremely fine grains can be obtained at the same carburization temperature as that of thoriated tungsten. This improves the processing performance of the material, reduces the filament breakage rate during the production and use of the material, and reduces the electronic work function of the material. This can not only reduce the filament breakage rate and increase the yield rate to reduce production and transportation costs, but also effectively increase the service life of the filament, making its service life reach and far exceed the service life of the existing thoriated tungsten filament.

[0384] (2) The initial recrystallization temperature of the filament material provided by the present invention 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 substrate 100 are relatively fine. The brittleness of the carburized filament is less than that of traditional thoriated tungsten filament materials, which will reduce the filament breakage rate during production and use.

[0385] (3) Analysis of the influence of the average size of oxide particles: By controlling the average size of the oxide particles of the tungsten alloy wire within the range specified in this application, it is beneficial to further improve the processing yield and flaw detection level of the wire. (4) The processing performance of the filament material of the present invention is better than that of the existing thoriated tungsten, with fewer flaw detection crack points (when the filament diameter can reach 500μm, the number of flaw detection crack points of the filament is less than 2 / 100 meters), the processing yield is high, and the wound filament is not easy to break, which improves production efficiency. In addition, the wire material has fewer crack points, and the proportion of carbonized broken filaments in the produced filament is also low.

[0386] (5) In the filament material provided by the present invention, 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. When 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 particle string; the types of rare earth oxides added by the present invention and the changes in morphological structure during the refinement process make the filament material have good processing performance. When preparing the wire material for winding the filament, the wire diameter of the filament material can be refined to 500μm or less, and the number of crack points in the flaw detection is effectively reduced, thereby improving the yield rate.

[0387] (6) The operating temperature of the heating device made of the tungsten alloy filament provided by the present invention (i.e., the operating temperature of the filament) can be reduced from 1500°C to 1600°C to 1100°C to 1500°C, such as within the range of 1200°C to 1300°C, while still maintaining 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 by the present invention and the heating device made therefrom will be improved.

[0388] In summary:

[0389] The filament provided by the present invention is formed 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 materials in the matrix 100. Compared with thoriated tungsten filaments, it can achieve the same or even higher electron emission capability at a lower operating voltage (excitation temperature).

[0390] The present invention dopes M oxides and carbides into tungsten matrix powder and controls the initial recrystallization temperature of the material so that extremely fine grains can be obtained at the same carburization temperature as thoriated tungsten. This improves the processing performance of the material, reduces the filament breakage rate during the production and use of the material, and reduces the electronic work function of the material. This reduces the filament breakage rate and improves the yield rate to reduce production and transportation costs, and effectively increases the service life of the filament, making the service life reach and far exceed the service life of existing thoriated tungsten filaments.

[0391] The filament provided by the present invention 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.

[0392] It should be noted that:

[0393] In this article, “~” is used to indicate a numerical range, and the range of this expression includes both endpoint values;

[0394] In summary, the specific parameters or some commonly used reagents or raw materials in the above embodiments are specific embodiments or preferred embodiments of the present invention, rather than limiting thereof; those skilled in the art can make adaptive adjustments within the scope of the present invention. In addition, unless otherwise specified, the raw materials used can also be conventional commercial products in the art, or prepared by conventional methods in the art.

[0395] 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 invention 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 any content not mentioned in a claim should not be construed as limiting the claim.

[0396] Although terms such as the initial recrystallization temperature and the average oxide size 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 the present invention; interpreting them as any additional limitation is contrary to the spirit of the present invention.

Claims

1. A method for preparing tungsten alloy wire, characterized in that: The tungsten alloy comprises the following components: 0.0005-0.3wt% carbon element, 0.25-2.6wt% M element, 0.05-0.5wt% oxygen element, the remainder being tungsten element and inevitable impurities, and the components do not contain thorium element; 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; The preparation process of the tungsten alloy wire includes the steps of doping powder making, powder pressing, sintering, and pressure processing in sequence; In the pressure processing step, the sintered tungsten alloy billet obtained after sintering is refined into an intermediate specification wire with a diameter of 1.5 to 3.5 mm; then the intermediate specification wire is subjected to oxidation annealing at (1200 to 1500)°C, and the annealing speed is (3 to 10) m / min; after oxidation annealing, the intermediate specification wire is further processed to the required wire diameter specification, so as to obtain tungsten alloy wire; Wherein, the initial recrystallization temperature of the tungsten alloy wire is 48%Fc-56%Fc, and / or the average size of the 80%Fc recrystallized grains is (1-15) μm.

2. The method for preparing tungsten alloy wire according to claim 1, characterized in that: The sintering step adopts a high temperature sintering method to obtain a tungsten alloy sintered billet; The heating curve of the high temperature sintering is: Raise the temperature from room temperature to A1 at a certain rate, and keep it at A1 for a certain period of time; Heat up from A1 to A2, the heating time is H3; keep warm at A2 for H4 hours; where A1 is (950~1250)℃, H3 is (1.5~2.5)h, A2 is (1300~1500)℃, and H4 is (2.5~4.5); Raise the temperature from A2 to A3 at a certain rate, A3 is (1700~1900)℃; keep the temperature at A3 for a certain period of time; Heat from A3 to A4 at a certain rate, A4 is (2050~2250)℃; keep warm at A4 for a certain time; It is obtained by natural cooling from A4.

3. The method for preparing tungsten alloy wire according to claim 2, characterized in that: The heating curve of the high temperature sintering is: From room temperature to A1, the heating time H1 is (5-8) h, and 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)℃; Keep warm at A2 for H4 hours, H4 is (2.5~4.5); From A2 to A3, the heating time is H5, H5 is (1-3) h, A3 is (1700-1900) °C; Keep warm at A3 for H6 hours, H6 is (1-3); From A3 to A4, the heating time is H7, H7 is (1-3) h, A4 is (2050-2250) °C; Keep warm at A4 for H8 hours, H8 is (5-10); It is obtained by natural cooling from A4.

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

5. A tungsten alloy wire, characterized in that: The invention 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 is tungsten element and inevitable impurities, and the components do not contain thorium element; Wherein, 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; The initial recrystallization temperature of the tungsten alloy wire is 48%Fc-56%Fc, and / or the average size of the 80%Fc recrystallized grains is (1-15) μm.

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

7. The tungsten alloy wire according to any one of claims 5-6, characterized in that: 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.

8. The tungsten alloy wire according to claim 5, characterized in that: The wire diameter is 800μm or less, and the number of flaw detection points is less than 5 / 100 meters; And / or, its components further include T element; the T element is a metal element, and the T is selected from at least one of K, Re, Mo, Fe, and Co; wherein the mass content of the Re is less than 1000 ppm.

9. A use of tungsten alloy wire, characterized in that: After the tungsten alloy filament is carbonized, it is used as a cathode alloy wire for a microwave heating device; Wherein, the tungsten alloy wire is the tungsten alloy filament as described in any one of claims 5-8, or the tungsten alloy wire is prepared by the preparation method as described in any one of claims 1-4.

10. A tungsten carbide alloy filament, characterized in that: It is obtained by carbonizing tungsten alloy wire; Wherein, the tungsten alloy wire is the tungsten alloy filament as described in any one of claims 5-8, or the tungsten alloy wire is prepared by the preparation method as described in any one of claims 1-4.

Images