Insulation hot wire preparation method and insulation hot wire preparation device

Abstract

The invention discloses a preparation method of an insulating hot wire and a preparation device of the insulating hot wire, and the preparation method of the insulating hot wire comprises the following steps: S1, coating the outer surface of the hot wire which is wound into a required shape with an insulating layer blank; and S2, electrifying the hot wire processed in the step S1, and directly heating the hot wire and the insulating layer blank coated on the hot wire by utilizing the heat effect of the current, so that the insulating layer blank is sintered and attached to the hot wire, and the insulating hot wire is further prepared. The insulating layer of the insulating hot wire prepared by the preparation method is not easy to fall off, the service life of the product is longer, the heating power is greatly reduced, the energy consumption is low, the process time is short, the requirement on equipment is lower, the insulating hot wire is easy to obtain, the test is convenient, the cost is low, and the yield is high.

Description

Technical Field

[0001] The invention relates to the technical field of electric vacuum element manufacturing, and in particular to a method for preparing an insulating hot wire and a device for preparing the insulating hot wire. Background Art

[0002] In active electric vacuum devices, the surface-insulated hot wire is a key component. It provides a stable heat source for the hot cathode to emit electrons, and also prevents the hot wire from short-circuiting with itself or other components. For hot wire elements that provide heat or light sources, surface insulation treatment is an important application form of hot wire. With the promotion of miniaturization, high reliability and long life of vacuum devices, the industry has higher and higher requirements for the insulation layer of insulated hot wires in terms of bonding strength, reliability and functionality.

[0003] At present, the preparation methods of the hot wire insulation layer include artificial coating, electrophoretic deposition or vapor deposition. Due to the large limitations of the vapor deposition method and the low reliability of its surface insulation, the preparation methods of the hot wire insulation layer are basically based on artificial coating or electrophoretic deposition. After the filament coated with the insulation layer is initially prepared by artificial coating or electrophoretic deposition, the insulating hot wire is further obtained by high-temperature sintering in a hydrogen furnace or vacuum furnace. For example, a method for preparing an insulating hot wire for electric vacuum published in a Chinese invention patent application with application publication number CN109518258A and application publication date 2019.03.26 involves a specific application of initially preparing a coated insulation layer by electrophoretic deposition, and then a conventional high-temperature hydrogen furnace is used to sinter the insulation layer, and the sintering temperature is 1200-1600°C. For example, the method for preparing a high-power and long-life cathode thermal sub-assembly disclosed in the Chinese invention patent application with application publication number CN107768210A and application publication date 2018.03.06 involves the winding structure of the cathode thermal sub-assembly, the ratio of ceramic fillers in the insulating layer, etc., and then a conventional high-temperature sintering furnace is used to complete the sintering preparation of the insulating layer. The sintering temperature is 1200℃~1300℃ and the sintering time is 2~4min.

[0004] The existing preparation methods of insulating hot wires mainly focus on improving the hot wire structure, the ratio of insulating medium components, the front end of the insulating hot wire (the hot wire and the insulating layer are initially prepared to obtain a coated insulating layer blank), etc., but rarely touch on the sintering process at the back end, and the sintering temperature is relatively low.

[0005] The conventional key process in the later stage of insulating hot wire preparation is to send the hot wire coated with the insulating layer obtained in the previous process into a high-temperature hydrogen furnace or a high-temperature vacuum furnace for sintering. The hot wire surface insulating layer blank itself is vitrified and attached to the hot wire base metal surface by indirect heating through high-temperature furnace baking. However, the existing sintering process often has the following three disadvantages:

[0006] 1) The sintering equipment limits the increase of the sintering process temperature. The relatively low temperature leads to insufficient porcelainization and softening of the insulating blank. There is no obvious liquid phase distribution between the hot wire base metal and the insulating layer ceramic. The bonding of the two materials is a solid phase process with low bonding strength and is easy to fall off and defect. Among them, the insulating layer of the insulating hot wire for electric vacuum is generally an inorganic oxide ceramic with a high melting point, and its melting point is mostly above 2000℃. Taking the common 95 alumina ceramic as an example, its firing temperature is generally 1620℃~1700℃, and the heat preservation is 4h. The firing temperature of high-purity alumina ceramic is even higher. Therefore, during the conventional sintering of the hot wire coated with the insulating layer blank, due to the low temperature, short time and loose blank, the insulating layer obtained after sintering is prone to stress defects and the insulating layer and the hot wire base metal are prone to fall off.

[0007] 2) The hot wire is heated gently and the temperature is uniform everywhere, so the residual stress inside the insulated hot wire is small, but this is not the case when the hot wire is working. Due to the cold end effect, the center temperature of the hot wire is usually the highest when it is working, and the temperature at the end is significantly lower. Therefore, the uneven temperature of the hot wire during actual operation leads to a large accumulation of thermal stress between the hot wire and the insulation layer, resulting in a lower thermal shock resistance of the hot wire and a shorter lifespan.

[0008] 3) Since sintering is an indirect heating and requires a special high-temperature sintering furnace, the equipment requirements are high, the process time is long, the energy consumption is high, and the adhesion of the obtained hot wire insulation layer is average.

[0009] Therefore, it is necessary to improve the prior art to overcome the defects in the prior art. Summary of the invention

[0010] The purpose of the present invention is to provide a method and device for preparing an insulating hot wire, so as to solve the problem that the insulating layer is easy to fall off and has a short service life in the existing high-temperature sintering process in the furnace, and the method has low energy consumption and flexible process control.

[0011] The technical solution adopted by the present invention to solve the technical problem is: a method for preparing an insulating hot wire, comprising the following steps:

[0012] S1, covering the outer surface of the heating wire wound into a desired shape with an insulating layer embryo;

[0013] S2, passing electric current through the hot wire obtained by S1, and using the thermal effect of the electric current to directly heat the hot wire and the insulating layer blank coated thereon, so that the insulating layer blank is sintered and attached to the hot wire, thereby obtaining an insulating hot wire.

[0014] As a further improvement of the present invention, in S2, the current magnitude and the power-on time are controlled according to a given power-on curve so as to heat the hot wire and the insulating layer blank coated thereon in stages.

[0015] As a further improvement of the present invention, the power-on curve includes the following stages:

[0016] In the heating stage, the current gradually increases from the first current value to the second current value within the third power-on time, so as to heat the heating wire to the second temperature value;

[0017] In the temperature peak stage, the current is instantaneously increased from the second current value to the third current value, so as to heat the hot wire to a third temperature value, i.e., a maximum temperature, and is maintained for a fifth power-on time, so that the insulating layer embryo is fully vitrified and softened, and the insulating layer embryo and the hot wire can be fully infiltrated and bonded;

[0018] In the rapid cooling stage, after the fifth power-on time ends, the current is instantly reduced from the third current value to the fourth current value and maintained for the sixth power-on time, and the temperature of the hot wire decreases to the fourth temperature value as the current decreases;

[0019] The third temperature value is higher than the porcelainization temperature and softening temperature of the insulating layer embryo, and lower than the melting point of the hot wire.

[0020] As a further improvement of the present invention, the power-on curve further includes the following stages:

[0021] A preheating stage, which is before the temperature rising stage, in which the current gradually increases from zero to the first current value within a first power-on time, so as to heat the hot wire to a first temperature value and maintain the second power-on time;

[0022] The cooling stage is located after the sudden cooling stage, and the current gradually decreases from the fourth current value to zero within the seventh power-on time.

[0023] As a further improvement of the present invention, the third temperature value is 1500°C to 2200°C; the fourth temperature value is 1100°C to 1400°C.

[0024] As a further improvement of the present invention, the heating wire is made of a refractory metal wire with a diameter of 0.1 mm to 2.4 mm and is wound in a desired shape.

[0025] As a further improvement of the present invention, the insulating layer embryo is coated on the outer surface of the hot wire by any one of slurry pulling, coating and electrophoretic deposition processes, and the thickness of the insulating layer embryo is 0.05 mm to 0.08 mm.

[0026] As a further improvement of the present invention, in S1, the portion where the insulating layer embryo covers the hot wire does not include the two ends of the hot wire; in S2, the hot wire covered with the insulating layer embryo is placed in a vacuum environment or an inert gas-filled environment and powered to prepare the insulated hot wire.

[0027] As a further improvement of the present invention, the control power source for energizing the hot wire is a pulse current source or a direct current source.

[0028] The present invention also provides an insulated hot wire preparation device, comprising: a sintering device with a vacuum environment or an inert gas environment, two electrical connectors placed in the sintering device for electrically connecting the two ends of the hot wire, and a control power supply electrically connected to the two electrical connectors through a wire; the preparation method of the insulated hot wire preparation device is:

[0029] The outer surface of the hot wire wound into a desired shape is covered with an insulating layer blank, and the hot wire is placed in the sintering device and electrically connected to the two electrical connectors. Current is passed through the hot wire through the control power supply, and the hot wire and the insulating layer blank coated thereon are directly heated by the thermal effect of the current, so that the insulating layer blank is sintered and attached to the hot wire, thereby obtaining an insulating hot wire.

[0030] The beneficial effects of the present invention are:

[0031] 1) The present invention provides a method and device for preparing an insulating hot wire, wherein the outer surface of a hot wire wound into a desired shape is covered with an insulating layer body and an electric current is passed through the body, and the hot wire and the insulating layer body covered thereon are directly heated by the thermal effect of the electric current, so that the insulating layer body is sintered and attached to the hot wire, thereby preparing the insulating hot wire. The process can easily achieve a higher heating temperature of the hot wire, with the highest temperature reaching above 2000°C, and can easily increase the sintering temperature to a temperature close to or exceeding the melting point of the insulating layer body, so that the insulating layer body can be fully vitrified and softened, with higher activity, and fully infiltrated and bonded with the slightly oxidized hot wire, thereby enhancing the bonding strength, and the sintered insulating layer is not easy to fall off, and the product has a longer service life;

[0032] 2) The present invention adopts direct sintering method, which greatly reduces heating power, has low energy consumption, short process time, low equipment requirements, easy acquisition, convenient testing, low cost, and the yield rate of insulating hot wire is increased from 60% of the traditional process to more than 90%;

[0033] 3) The present invention utilizes the thermal effect of electric current to directly heat the hot wire for sintering. Although the temperature of the hot wire is not consistent (the temperature in the middle is high and the temperature at both ends is low), it is similar to the actual work. Therefore, the thermal stress of the hot wire is small when it is working, which improves the heat shock resistance of the hot wire and further increases the service life.

[0034] 4) The present invention controls the current size and power-on time according to a given power-on curve to heat the hot wire and the insulating layer blank coated thereon in stages, thereby being able to accurately and flexibly control the direct sintering temperature of the hot wire, facilitating the application of fine technology;

[0035] 5) The temperature peak stage of the power-on curve of the present invention can quickly heat the insulating layer embryo to a state close to melting, so that the insulating layer embryo can be fully vitrified and softened, and the activity is higher, so that the insulating layer embryo and the slightly oxidized hot wire are better infiltrated, the effect is more sufficient, and the bonding is more reliable; at the same time, the sudden cooling stage of the power-on curve can slowly release the internal stress between the sintered insulating layer and the hot wire, further enhance the adhesion and thermal shock resistance of the hot wire and the insulating layer, and also play a quenching role on the hot wire, which can enhance the strength of the hot wire. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 A flowchart of the steps of the method for preparing the insulating hot wire of the present invention;

[0037] Figure 2 This is a power-on curve diagram of the present invention using a pulse current source;

[0038] Figure 3 This is a power-on curve diagram of the present invention using a direct current source;

[0039] Figure 4 It is a structural schematic diagram of the insulating hot wire preparation device of the present invention;

[0040] Figure 5 It is a schematic diagram of the structure of the hot wire of the present invention.

[0041] Combined with the accompanying drawings, the following description is given:

[0042] 1. Sintering device; 2. Hot wire; 3. Electrical connector; 4. Control power supply. DETAILED DESCRIPTION

[0043] The exemplary embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings. If there are several embodiments, the features of these embodiments can be combined with each other without conflict. When the description refers to the drawings, unless otherwise specified, the same numbers in different drawings represent the same or similar elements. The contents described in the following exemplary embodiments do not represent all embodiments consistent with the present invention; on the contrary, they are only examples of devices, products and / or methods consistent with some aspects of the present invention as recorded in the claims of the present invention.

[0044] The terms used in the present invention are only for the purpose of describing specific embodiments, and are not intended to limit the scope of protection of the present invention. The singular forms "a", "said" or "the" used in the specification and claims of the present invention are also intended to include plural forms, unless the context clearly indicates other meanings.

[0045] It should be understood that the words used in the specification and claims of the present invention, such as "first", "second" and similar words, do not indicate any order, quantity or importance, but are only used to distinguish the names of features. Similarly, words such as "one" or "a" and similar words do not indicate a quantitative limitation, but indicate the existence of at least one. Unless otherwise specified, words such as "front", "rear", "upper", "lower" and similar words appearing in the present invention are only for the convenience of explanation and are not limited to a specific position or a spatial orientation. Words such as "include" or "comprise" are an open-ended expression, meaning that the elements appearing before "include" or "comprise" include the elements appearing after "include" or "comprise" and their equivalents, which does not exclude that the elements appearing before "include" or "comprise" may also include other elements. If "several" or "multiple" appears in the present invention, its meaning refers to two and more than two.

[0046] See also Figure 1 The present invention provides a method for preparing an insulating hot wire, comprising steps S1 and S2, wherein S1: coating the outer surface of the hot wire wound into a desired shape with an insulating layer blank; S2: passing an electric current through the hot wire obtained by S1, and utilizing the thermal effect of the electric current to directly heat the hot wire and the insulating layer blank coated thereon, so that the insulating layer blank is sintered and attached to the hot wire, thereby obtaining the insulating hot wire.

[0047] The present invention utilizes the heat concentration characteristic of the hot wire itself. By applying electricity at both ends of the hot wire that covers the insulating layer blank, it is easy to achieve a higher hot wire heating temperature, and it is easy to increase the sintering temperature to close to or exceed the melting point of the insulating layer blank, so that the insulating layer blank can be fully vitrified and softened, and the activity is higher. It is fully infiltrated and bonded with the micro-oxidized hot wire to enhance the bonding strength. The sintered insulating layer is not easy to fall off, and the product has a longer service life. At the same time, since the present invention adopts a direct sintering method, the heating power is greatly reduced, the energy consumption is low, and the process time is short, the equipment requirements are low, it is easy to obtain, the test is convenient, and the cost is low. In addition, the present invention utilizes the thermal effect of electric current to directly heat the hot wire for sintering. Although the temperature of the hot wire is inconsistent (the middle temperature is high and the two ends are low), it is just similar to the actual work. Therefore, the thermal stress of the hot wire is small when it is working, the heat shock resistance of the hot wire is improved, and the service life is further increased.

[0048] The heating wire is made of refractory metal wire with a diameter of 0.1 mm to 2.4 mm and is wound in a desired shape. The heating wire is made of commonly used heating wire materials in the art, such as Mo, MoLa, W, WRe and other alloys based on Mo and W.

[0049] As an embodiment of the present invention, the insulating heating wire prepared by the present invention can be used in an electric vacuum device.

[0050] Optional, such as Figure 5 As shown, the shape of the hot wire after winding is a multi-turn spiral structure, and the two ends of the hot wire are led out from the two ends of the spiral structure along the axis toward each other.

[0051] In S1, the insulating layer embryo body can be coated on the outer surface of the hot wire by any of the conventional processes such as slurry pulling, coating and electrophoretic deposition, and the part where the insulating layer embryo body coats the hot wire does not include the two ends of the hot wire. The length of the part without the insulating layer embryo body at the two ends of the hot wire is ≥10mm so as to be electrically connected to the control circuit.

[0052] The thickness of the insulating layer embryo body is 0.05 mm to 0.08 mm.

[0053] Furthermore, in S2, the hot wire and the insulating layer blank coated thereon are heated in stages by controlling the current size and the power-on time according to a given power-on curve, so that the direct sintering temperature of the hot wire can be accurately and flexibly controlled, which is convenient for the application of fine technology.

[0054] like Figure 2 and Figure 3 As shown, the power-on curve specifically includes a preheating stage, a temperature rise stage, a temperature peak stage, a sudden cooling stage and a cooling stage which are sequentially connected along the horizontal axis direction.

[0055] Preheating stage: before the heating stage, the current gradually increases from zero to the first current value during the first power-on time to heat the hot wire to the first temperature value and maintain the second power-on time. The first temperature value is much lower than the maximum temperature and can usually be controlled at 400℃~800℃, and this first temperature value is higher than the volatilization temperature of the adhesive doped in the insulating layer embryo. The preheating stage can fully volatilize the adhesive.

[0056] Heating stage: The current gradually increases from the first current value to the second current value during the third power-on time to heat the hot wire to the second temperature value, so that the temperature of the hot wire gradually rises to a higher temperature. The second temperature value is roughly equivalent to the actual working temperature of the hot wire, which can usually be controlled at 1250±150℃, and is maintained for the fourth power-on time to ensure that the temperature of the hot wire is uniform.

[0057] Temperature peak stage: the current is instantaneously increased from the second current value to the third current value to heat the hot wire to the third temperature value, i.e., the highest temperature, and maintained for the fifth power-on time. Among them, the third temperature value is higher than the porcelain temperature and softening temperature of the insulating layer embryo, and lower than the melting point of the hot wire, so that the insulating layer embryo can be fully porcelainized and softened, and the activity is higher, so that the insulating layer embryo and the micro-oxidized hot wire are better infiltrated, more fully acted, and more reliably bonded. In this temperature peak stage, the instantaneous increase of the current to the third current value can quickly heat the insulating layer embryo to a state close to the melting state, and enter the rapid cooling stage after maintaining a relatively short fifth power-on time, so as to avoid the slow increase in temperature and the prolonged heating time, which may cause the insulating layer embryo to flow too much or even drip, resulting in unevenness.

[0058] The third temperature value is 1500° C. to 2200° C. According to the selection of the hot wire material, the power-on curve can be adjusted to control the maximum temperature.

[0059] Sudden cooling stage: After the fifth power-on time, the current is instantly reduced from the third current value to the fourth current value and maintained for the sixth power-on time. As the current decreases, the temperature of the hot wire drops sharply to the fourth temperature value, so as to slowly release the internal stress between the sintered insulating layer and the hot wire, further enhance the adhesion between the hot wire and the insulating layer and the ability to resist thermal shock, and at the same time, quench the hot wire to enhance the strength of the hot wire.

[0060] Among them, the fourth temperature value is 1100°C to 1400°C.

[0061] Cooling stage: located after the sudden cooling stage, the current gradually decreases from the fourth current value to zero during the seventh power-on time, and the temperature of the hot wire gradually decreases as the current decreases, and finally cools to room temperature.

[0062] It is worth mentioning that in S2, the hot wire coated with the insulating layer embryo is placed in a vacuum environment or an inert gas filled environment and powered on to prepare the insulated hot wire. The vacuum degree is ≤1E-2Pa; the inert gas can be hydrogen, argon, nitrogen, etc.

[0063] Among them, the control power supply for energizing the hot wire is a pulse current source or a DC current source, preferably a pulse current source. The peak value of the pulse current is relatively large. Under the pulse peak current, it can instantly heat the temperature to a temperature close to the melting point of the insulating layer blank, and then immediately cool it down. In this way, heating is performed according to the repetition frequency of the pulse current, so that the insulating layer and the hot wire are better combined, and the insulating layer will not soften and flow excessively to cause unevenness.

[0064] See also Figure 4The present invention also provides an insulating hot wire preparation device, comprising: a sintering device 1 with a vacuum environment or an inert gas filled environment inside, two electrical connectors 3 placed in the sintering device 1 for electrically connecting the two ends of the hot wire 2, and a control power supply 4 electrically connected to the two electrical connectors 3 through wires. The sintering device 1 includes a base and a sealing cover. The sealing cover is arranged on the base, and a carrier is arranged on the base. The sintering device 1 is connected to an external vacuum generating device or an inert gas filling device. The insulating hot wire preparation device of the present invention prepares the insulating hot wire by adopting the above-mentioned preparation method.

[0065] Taking the hot wire 2 with a single spiral structure wound by tungsten-rhenium wire with a diameter of 0.6 mm and a length of 950 mm as an example, the number of winding turns is 31, the pitch is 1.7 mm, and the cold resistance is 250 mΩ. Combined with the insulating hot wire preparation device and preparation method of the present invention, the preparation process of the insulating hot wire is described in detail.

[0066] First, an aluminum oxide coating is sprayed on the hot wire 2 by a conventional spraying method to obtain a hot wire 2 with an insulating layer coating thickness of 0.06 mm.

[0067] Next, the hot wire 2 is placed on a carrier of the sintering device 1 , and two electrical connectors 3 are clamped on the two ends of the hot wire 2 green body not covered with the insulating layer.

[0068] Optionally, the electrical connector 3 is a high temperature resistant bare metal wire clamp or a high temperature resistant metal connector, and the preferred material of the electrical connector 3 is a high temperature resistant metal such as molybdenum and nickel.

[0069] Next, the sealing cover is placed on the base, and the sintering device 1 is evacuated by an external vacuum generating device.

[0070] Afterwards, when the vacuum degree reaches 1E-2Pa, a pulse current source is used according to Figure 2 The power-up curve shown or a conventional DC current source is used according to Figure 3 The power-on curve shown passes current through the hot wire 2, and uses the thermal effect of the current to directly heat the hot wire 2 and the insulating layer blank coated thereon, so that the aluminum oxide insulating layer is fully softened or even melted, and the fluidity and activity are increased so that it can fully interact with the slightly oxidized surface of the hot wire 2 substrate to produce adhesion, so as to achieve sintering and attachment of the insulating layer blank to the hot wire 2, thereby producing an insulating hot wire.

[0071] Among them, the temperature values ​​corresponding to the power-on curves of the pulse current source and the DC current source are as follows:

[0072] Table 1

[0073] Time / s Pulse current / A Current / A Temperature / ℃ 0 0 0 25 60 120 6 600 90 120 6 600 150 220 11 1400 180 220 11 1400 180 310 15.5 2000 210 310 15.5 2000 210 180 9 1200 360 180 9 1200 480 0 0 300

[0074] When a pulse current source is used, the pulse width is set to 60μs and the repetition frequency is 1000Hz. The corresponding first power-on time, second power-on time, third power-on time, fourth power-on time, fifth power-on time, sixth power-on time and seventh power-on time are 60s, 30s, 60s, 30s, 30s, 150s and 120s respectively; the corresponding first current value, second current value, third current value and fourth current value are 120A, 220A, 310A and 180A respectively; the corresponding first temperature value, second temperature value, third temperature value and fourth temperature value are 600℃, 1400℃, 2000℃ and 1200℃ respectively.

[0075] When a direct current source is used, the corresponding first power-on time, second power-on time, third power-on time, fourth power-on time, fifth power-on time, sixth power-on time, and seventh power-on time are 60s, 30s, 60s, 30s, 30s, 150s, and 120s respectively; the corresponding first current value, second current value, third current value, and fourth current value are 6A, 11A, 15.5A, and 9A respectively; the corresponding first temperature value, second temperature value, third temperature value, and fourth temperature value are 600°C, 1400°C, 2000°C, and 1200°C respectively.

[0076] Then, turn off the vacuum generating equipment and continue to cool naturally for 20 minutes before inflating and removing the insulating hot wire.

[0077] Finally, the insulating hot wire was tested and observed under a microscope, with no cracks or holes and a smooth surface. The insulating hot wire was dropped freely from a height of 500 mm onto a marble platform for multiple times, with no defects, peeling or cracking in the insulating layer.

[0078] It can be seen that the preparation method and the preparation device of the insulating hot wire of the present invention, by coating the outer surface of the hot wire wound into the desired shape with an insulating layer embryo and passing an electric current, using the thermal effect of the electric current to directly heat the hot wire and the insulating layer embryo coated thereon, so as to achieve sintering and attachment of the insulating layer embryo to the hot wire, thereby obtaining the insulating hot wire, the process can easily achieve a higher heating temperature of the hot wire, the highest temperature reaches above 2000°C, and it is easy to increase the sintering temperature to close to or exceed the melting point of the insulating layer embryo, so that the insulating layer embryo can be fully vitrified and softened, with higher activity, and fully infiltrated and bonded with the micro-oxidized hot wire, and the bonding force is enhanced, the sintered insulating layer is not easy to fall off, and the product service life is longer. The present invention adopts a direct sintering method, which greatly reduces the heating power, has low energy consumption, and has a short process time, low equipment requirements, is easy to obtain, convenient to test, and low cost. The yield rate of the insulating hot wire is increased from 60% of the traditional process to more than 90%. The present invention utilizes the thermal effect of electric current to directly heat the hot wire for sintering. Although the temperature of the hot wire is not consistent (the temperature in the middle is high and the temperature at both ends is low), it is similar to the actual work. Therefore, the thermal stress of the hot wire is small when it is working, which improves the heat shock resistance of the hot wire and further increases the service life. The present invention controls the current size and power-on time according to a given power-on curve to heat the hot wire and the insulating layer blank coated thereon in stages, thereby being able to accurately and flexibly regulate the direct sintering temperature of the hot wire, which is convenient for the application of fine technology. The temperature peak stage of the power-on curve of the present invention can quickly heat the insulating layer blank to a state close to the melting state, so that the insulating layer blank can be fully vitrified and softened, and the activity is higher, so that the insulating layer blank and the slightly oxidized hot wire are better infiltrated, more fully acted, and more reliably bonded; at the same time, the sudden cooling stage of the power-on curve can slowly release the internal stress between the sintered insulating layer and the hot wire, further enhancing the adhesion and heat shock resistance of the hot wire and the insulating layer, and also plays a quenching role on the hot wire, which can enhance the strength of the hot wire.

[0079] Many specific details are described in the above description to facilitate a full understanding of the present invention. However, the above description is only a preferred embodiment of the present invention. The present invention can be implemented in many other ways different from those described herein, so the present invention is not limited to the specific implementation disclosed above. At the same time, any person familiar with the art can make many possible changes and modifications to the technical solution of the present invention using the methods and technical contents disclosed above without departing from the scope of the technical solution of the present invention, or modify it into an equivalent embodiment of equivalent changes. Any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention still falls within the scope of protection of the technical solution of the present invention.

Claims

1. A method for preparing an insulating hot wire, characterized in that: The following steps are involved: S1, covering the outer surface of the heating wire wound into a desired shape with an insulating layer embryo; S2, passing electric current through the hot wire obtained by S1, and using the thermal effect of the electric current to directly heat the hot wire and the insulating layer blank coated thereon, so that the insulating layer blank is sintered and attached to the hot wire, thereby obtaining an insulating hot wire.

2. The method for preparing the insulating hot wire according to claim 1, characterized in that: In S2, the current magnitude and the power-on time are controlled according to a given power-on curve so as to heat the hot wire and the insulating layer blank coated thereon in stages.

3. The method for preparing the insulating hot wire according to claim 2, characterized in that: The power-up profile includes the following phases: In the heating stage, the current gradually increases from the first current value to the second current value within the third power-on time, so as to heat the heating wire to the second temperature value; In the temperature peak stage, the current is instantaneously increased from the second current value to the third current value, so as to heat the hot wire to a third temperature value, i.e., a maximum temperature, and is maintained for a fifth power-on time, so that the insulating layer embryo is fully vitrified and softened, and the insulating layer embryo and the hot wire can be fully infiltrated and bonded; In the rapid cooling stage, after the fifth power-on time ends, the current is instantly reduced from the third current value to the fourth current value and maintained for the sixth power-on time, and the temperature of the hot wire decreases to the fourth temperature value as the current decreases; The third temperature value is higher than the porcelainization temperature and softening temperature of the insulating layer embryo, and lower than the melting point of the hot wire.

4. The method for preparing the insulating hot wire according to claim 3, characterized in that: The power-up profile also includes the following phases: A preheating stage, which is before the temperature rising stage, in which the current gradually increases from zero to the first current value within a first power-on time, so as to heat the hot wire to a first temperature value and maintain the second power-on time; The cooling stage is located after the sudden cooling stage, and the current gradually decreases from the fourth current value to zero within the seventh power-on time.

5. The method for preparing the insulating hot wire according to claim 3, characterized in that: The third temperature value is 1500°C to 2200°C; the fourth temperature value is 1100°C to 1400°C.

6. The method for preparing the insulating hot wire according to claim 1, characterized in that: The hot wire is made of a refractory metal wire with a diameter of 0.1 mm to 2.4 mm and is wound in a required shape.

7. The method for preparing the insulating hot wire according to claim 1, characterized in that: The insulating layer embryo is coated on the outer surface of the hot wire by any one of slurry pulling, coating and electrophoretic deposition processes, and the thickness of the insulating layer embryo is 0.05 mm to 0.08 mm.

8. The method for preparing the insulating hot wire according to claim 1, characterized in that: In S1, the portion where the insulating layer embryo covers the hot wire does not include both ends of the hot wire; in S2, the hot wire covered with the insulating layer embryo is placed in a vacuum environment or an inert gas-filled environment and powered to prepare the insulated hot wire.

9. The method for preparing the insulating hot wire according to claim 1, characterized in that: The control power source for energizing the hot wire is a pulse current source or a direct current source.

10. An insulating hot wire preparation device, characterized in that: include: A sintering device (1) having a vacuum environment or an inert gas environment, two electrical connectors (3) placed in the sintering device (1) for electrically connecting two ends of a hot wire (2), and a control power supply (4) electrically connected to the two electrical connectors (3) via a wire; a method for preparing the insulating hot wire preparation device is as follows: The outer surface of the hot wire (2) wound into a desired shape is coated with an insulating layer blank, and the hot wire (2) is placed in the sintering device (1) and electrically connected to the two electrical connectors (3). An electric current is passed through the hot wire (2) through the control power supply (4), and the hot wire (2) and the insulating layer blank coated thereon are directly heated by the thermal effect of the current, so that the insulating layer blank is sintered and attached to the hot wire (2), thereby obtaining an insulating hot wire.

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