A multi-element alloy modified double-mesh heating wire and its preparation method

Abstract

This invention discloses a multi-element alloy modified double-mesh heating wire and its preparation method, which relates to the technical field of resistance heating elements and special electrothermal alloy materials. The heating wire adopts an integrated double-layer mesh structure with inner and outer layers. The inner and outer layers are completely interwoven and bonded by vacuum in-situ diffusion welding. The inner layer is a high-resistivity dense heating mesh, which is prepared by modifying a nickel-chromium-aluminum-yttrium-molybdenum five-element multi-element alloy. The outer layer is a low-resistivity loose uniform heat dissipation mesh, which is prepared by modifying an iron-chromium-aluminum-cerium-titanium five-element multi-element alloy. This invention uses differentiated five-element rare earth alloys in the inner and outer layers to adapt to heating and uniform temperature conditions respectively. Relying on the differences in electrothermal and thermal conductivity of different alloy materials, the heating wire can achieve autonomous zone heating, effectively improve the heating rate and temperature uniformity, alleviate high-temperature alternating thermal stress, and improve the heating wire's resistance to fatigue fracture and high-temperature oxidation.

Description

Technical Field

[0001] This invention belongs to the technical field of resistance heating elements and special heating alloy materials, and particularly relates to a multi-element alloy modified double mesh heating wire and its preparation method. Background Technology

[0002] Existing dual-mesh heating wires generally employ a two-layer homogeneous mesh structure design, with identical wire diameter, porosity, and base alloy material for both layers. They rely solely on the superposition of the two meshes to increase heating power, lacking interlayer functional zoning and resistance gradient design. Furthermore, conventional heating wires on the market only use binary or ternary nickel-chromium / iron-chromium-aluminum base alloys, without undergoing multi-element modification with rare earth elements and refractory metals, resulting in numerous inherent defects. 1. Temperature control defects: The dual-layer synchronous heating has no division of labor, resulting in slow heating speed, dense local hot spots on the surface of the heating wire, and a surface temperature difference of up to ±12℃, which cannot meet the uniform temperature requirements of precision heating scenarios. 2. Material heat resistance defects: Conventional alloys have poor high-temperature creep resistance. After long-term alternating hot and cold cycles, thermal stress continues to accumulate, and the mesh is prone to fatigue cracking and wire breakage. 3. Antioxidation defects: A single base alloy cannot form a dense and stable protective oxide film at high temperatures. Under high temperature conditions above 1000℃, the surface layer oxidizes rapidly, peels off, and the heating power continues to decrease, resulting in a significant reduction in the service life of components. 4. Structural defects: Traditional double-layer mesh uses adhesive bonding and spot welding splicing processes, which makes the interface prone to delamination and peeling at high temperatures, resulting in poor overall structural mechanical stability. Summary of the Invention

[0003] This invention employs differentiated pentagonal rare earth alloys for inner and outer layers to adapt to heating and temperature uniformity conditions. Leveraging the inherent differences in electrothermal and thermal conductivity of the different alloy materials, it achieves autonomous zoned heating of the heating wire, effectively improving heating speed and temperature uniformity, alleviating high-temperature alternating thermal stress, and enhancing the heating wire's resistance to fatigue fracture and high-temperature oxidation. Furthermore, this invention introduces differentiated nano-ceramic particles for composite modification, further strengthening the alloy's high-temperature mechanical stability and extending the heating wire's high-temperature service life, thus solving the problems of uneven temperature control, easy oxidation and cracking, and easy interface peeling inherent in traditional double-layer heating wires.

[0004] To achieve the above objectives, the present invention provides the following technical solution: A multi-element alloy modified double mesh heating wire is provided. The heating wire adopts an integrated double-layer mesh structure with inner and outer nesting. The inner and outer layers are completely interwoven and bonded by vacuum in-situ diffusion welding. The inner layer is a high-resistance dense heating mesh, which is prepared by modifying a nickel-chromium-aluminum-yttrium-molybdenum five-element multi-element alloy. The outer layer is a low-resistance loose uniform heat dissipation mesh, which is prepared by modifying an iron-chromium-aluminum-cerium-titanium five-element multi-element alloy.

[0005] The inner high-resistivity dense heating mesh substrate is a nickel-chromium high-temperature electric heating alloy, which is modified by three trace elements: aluminum, yttrium, and molybdenum. The functions of each component are as follows: Nickel and chromium: Construct a high resistivity matrix to ensure the basic heating power of the inner layer and adapt to the need for rapid heating; Aluminum: An aluminum oxide base protective layer is formed in situ at high temperatures, which blocks oxygen corrosion; Rare earth yttrium: a core grain refinement and modification element that breaks down coarse grains during alloy casting and wire drawing, eliminates microscopic defects inside the alloy, reduces microscopic thermal stress during the thermal cycling of the wire, and inhibits crack initiation at the material level. Refractory metal molybdenum: Improves the high-temperature creep resistance of the alloy, prevents the heating wire from undergoing plastic deformation due to long-term heating under high-temperature conditions of 1250℃, and maintains the dimensional stability of the mesh structure.

[0006] The resistivity of the modified inner alloy is significantly improved, which is compatible with the dense mesh structure and enables rapid heating in 3 seconds after power-on, meeting the instantaneous high-power heating requirements.

[0007] The outer low-resistivity, loosely structured, heat-dissipating mesh substrate is made of a low-cost, high-thermal-conductivity iron-chromium-aluminum alloy. Through multi-element modification with cerium and titanium trace elements, its thermal conductivity and high-temperature oxidation resistance are enhanced. The functions of each component are as follows: Iron, chromium, and aluminum: a high thermal conductivity matrix, with a 35% increase in thermal conductivity compared to conventional nickel-chromium alloys, which can quickly dissipate the concentrated heat in the inner layer; Rare earth cerium: a core element for surface modification, guiding the alloy to undergo high-temperature oxidation to form a continuous, dense, and non-porous alumina composite protective film, completely blocking oxygen from penetrating into the mesh and eliminating the problems of high-temperature oxidation peeling and flaking. Titanium: Strengthens the bonding force at the alloy interface, improves the fatigue resistance of the outer mesh, and, in conjunction with the thermal deformation of the inner layer, buffers the interfacial thermal stress between the two mesh layers.

[0008] Preferably, the inner high-resistivity dense heating mesh is distributed as follows by mass percentage: nickel 68%–72%, chromium 18%–22%, aluminum 3%–5%, yttrium 1%–3%, and molybdenum 3%–5%.

[0009] Preferably, the outer low-resistivity, loose, uniform heat dissipation mesh is distributed as follows by mass percentage: iron 63%–67%, chromium 16%–20%, aluminum 8%–12%, cerium 2%–4%, and titanium 3%–5%.

[0010] Preferably, the inner dense heating mesh has a wire diameter of 0.35 mm and a mesh porosity of 32%, and the resistance of the inner dense heating mesh is 3.2 times that of the outer low-resistance loose uniform heat dissipation mesh.

[0011] The inner high-resistivity dense heating mesh adopts a fine-pore, high-wire-diameter, and high-density weaving process, with a mesh porosity of 32% and a wire diameter of 0.35mm. Relying on the high resistivity characteristics of nickel-chromium-based pentagonal alloy, the overall resistance value is 3.2 times that of the outer mesh, which concentrates more than 80% of the heating power, forming a core high-temperature heating zone, and achieving rapid heating of the entire area within 3 seconds after power-on.

[0012] Preferably, the outer layer of loose, heat-dissipating mesh has a wire diameter of 0.20 mm and a mesh porosity of 68%.

[0013] The outer loose heat dissipation mesh adopts a large-aperture, fine-wire, low-density weaving process with a mesh porosity of 68% and a wire diameter of 0.20mm. Relying on the high thermal conductivity and low resistivity characteristics of the iron-chromium-aluminum pentagonal alloy, it does not generate excess heat sources and only serves as a heat conduction carrier to quickly disperse the hot spots in the inner layer and form a low-temperature uniform temperature buffer zone.

[0014] The two-layer mesh is mechanically interlocked and woven with completely staggered mesh openings and no directly opposite through holes. This avoids direct heat loss and increases the contact area between the two layers. No organic or inorganic adhesives are added throughout the process, thus avoiding the problem of adhesive carbonization failure at high temperatures.

[0015] Based on the original pentagonal alloy matrix, this invention further introduces in-situ self-generated nano-ceramic particles for second-phase composite modification, and adopts a differentiated ceramic doping scheme for inner and outer layers: the inner layer is matched with nano-zirconia and the outer layer is matched with nano-alumina. The two complement each other in function, further suppressing the initiation of microcracks under extreme thermal cycling and further reducing interfacial thermal mismatch stress.

[0016] As a preferred embodiment of the present invention, the inner high-resistivity dense heating mesh also contains 1.2% nano-zirconia ceramic particles.

[0017] In this invention, 1.2% by mass of tetragonal phase nano-zirconia particles are added to the original nickel-chromium-aluminum-yttrium-molybdenum pentagonal alloy matrix in the inner layer. The particle size is controlled between 30nm and 50nm. By utilizing the toughening mechanism of zirconia phase transformation, combined with the grain refinement effect of rare earth yttrium, the alloy grain boundaries are double-pinned, completely blocking the propagation path of microcracks under high temperature thermal stress. This further improves the thermal fatigue resistance and high temperature creep resistance of the inner layer heating mesh, and solves the grain boundary slip failure problem under long-term service at ultra-high temperature of 1250℃.

[0018] As a preferred embodiment of the present invention, the outer low-resistivity loose heat dissipation mesh is further supplemented with 1.0% nano-alumina particles.

[0019] In this invention, 1.0% by mass of in-situ nano-alumina particles are added to the original iron-chromium-aluminum-cerium-titanium pentagonal alloy matrix of the outer layer. The nano-alumina can serve as the nucleation core for oxide film growth, and together with rare earth cerium, make the outer surface protective film denser and more uniform in thickness. At the same time, it further improves the thermal conductivity of the outer alloy, reduces the difference in thermal expansion coefficient between the two dissimilar alloys, alleviates the thermal mismatch stress at the interface of the two layers, and eliminates the problem of interface delamination during long-term high-temperature service.

[0020] This invention also provides a method for preparing a multi-element alloy modified double-mesh heating wire, which includes the following steps: S1. Vacuum arc melting and homogenization annealing: Weigh the alloy powder according to the above-mentioned mass percentage range, melt the inner layer of nickel-chromium-aluminum-yttrium-molybdenum pentagonal alloy and the outer layer of iron-chromium-aluminum-cerium-titanium pentagonal alloy, with a melting vacuum degree ≤5×10Pa, and repeat the melting 4 times to ensure uniform composition; then hold at 1050℃ for 2h for homogenization annealing to eliminate the internal stress of alloy casting. S2, Micro-drawing and surface passivation: Two alloy billets are drawn to the target wire diameter, and then nanoscale surface passivation pretreatment is performed to pre-form an ultra-thin oxide protective layer on the surface of the wire. S3, Gradient Double-Net Synchronous Weaving: Using a double-head synchronous weaving device, a double-layer mesh blank with a dense inner layer and a sparse outer layer is woven in one piece, directly completing the double-layer interlocking and seamless bonding; S4. Vacuum in-situ diffusion welding composite: The double-mesh billet is placed in a vacuum diffusion welding furnace with a vacuum degree ≤3×10Pa and held at 850℃ for 40min to achieve atomic diffusion metallurgical bonding of the interface of the double-layer dissimilar alloy. S5. Post-processing and shaping: The double-mesh blank after diffusion welding is subjected to a low-temperature oxidation coating treatment at 700℃, followed by electrode terminal welding and high-temperature insulating encapsulation to obtain the finished product.

[0021] As a preferred embodiment of the present invention, the following steps are included: S1. Take nano-zirconia powder and nano-alumina powder respectively, place them in an oven, and dry them at 120℃ for 2 hours to completely remove the adsorbed water vapor from the powder; then add a trace amount of anhydrous ethanol as a dispersant and perform ultrasonic dispersion treatment with an ultrasonic power of 300W and a dispersion time of 40min. S2. Prepare inner layer alloy powder and outer layer alloy powder separately. The inner layer pentagonal alloy powder and the pretreated nano-zirconia powder are fed into a planetary ball mill according to the specified ratio. The outer layer pentagonal alloy powder and the pretreated nano-alumina powder are fed separately. The grinding media are hard alloy grinding balls with a ball-to-material ratio of 3:1. The ball milling speed is 350 r / min and the dry grinding and mixing time is 2.5 h. S3. The uniformly mixed composite powder is loaded into molds and cold-pressed at room temperature and 25MPa pressure to prepare inner composite alloy preforms and outer composite alloy preforms. S4. Place the two alloy preforms into a vacuum arc melting furnace with a melting vacuum of ≤5×10Pa and melt them repeatedly 4 times to ensure uniform composition. Then, hold at 1050℃ for 2 hours for homogenization annealing to eliminate the internal stress of alloy casting. S5. Micro-drawing and surface passivation: Two alloy billets are drawn to the target wire diameter, and then nano-level surface passivation pretreatment is performed to pre-form an ultra-thin oxide protective layer on the surface of the wire. S6. Gradient Double-Net Synchronous Weaving: Using a double-head synchronous weaving device, a double-layer mesh blank with a dense inner layer and a sparse outer layer is woven in one piece, directly completing the double-layer interlocking and seamless bonding. S7. Vacuum in-situ diffusion welding composite: The double-mesh billet is placed in a vacuum diffusion welding furnace with a vacuum degree ≤3×10Pa and held at 850℃ for 40min to achieve atomic diffusion metallurgical bonding of the interface of the double-layer dissimilar alloy. S8. Post-processing and shaping: The double-mesh blank after diffusion welding is subjected to a low-temperature oxidation coating treatment at 700℃, followed by electrode terminal welding and high-temperature insulating encapsulation to obtain the finished product.

[0022] In summary, the beneficial technical effects of the present invention are as follows: 1. Relying on the thermal conductivity and resistance gradient matching of the double-layer differentiated multi-element alloy, the surface temperature difference of the heating wire is reduced from ±12℃ in the traditional double-mesh system to ±2.5℃, with no local hot spots, making it suitable for precision heating scenarios.

[0023] 2. The inner layer of yttrium rare earth grain refinement modification combined with the outer layer of titanium element interface buffer modification reduces the micro and macro thermal stress of the material in two ways. The service life of the cold and hot cycle is increased by 4 times compared with the conventional double mesh heating wire, and the problem of mesh wire cracking and breakage under high temperature cycling is completely solved.

[0024] 3. The outer layer of cerium rare earth induces the formation of a dense alumina protective film, which can withstand continuous operation at 1250℃ without oxidation peeling or flaking, and the heating power does not decrease over a long period of time.

[0025] 4. The nickel-chromium-based pentagonal high-resistivity alloy combined with a dense mesh structure can reach the rated operating temperature in 3 seconds after being powered on, solving the problem of delayed heating of traditional heating wires.

[0026] 5. Vacuum in-situ diffusion welding achieves double-layer metallurgical bonding, which can withstand repeated impacts from high and low temperatures and will not cause double-layer delamination or delamination failures, thus improving the overall structural mechanical strength by 60%. Detailed Implementation

[0027] The present invention will now be described in further detail.

[0028] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] The invention adopts an integrated double-layer mesh structure with inner and outer nesting. The inner and outer layers are completely interwoven and woven together by vacuum in-situ diffusion welding. The inner layer is a high-resistivity dense heating mesh, which is prepared by modifying a nickel-chromium-aluminum-yttrium-molybdenum five-element multi-element alloy. The outer layer is a low-resistivity loose uniform heat dissipation mesh, which is prepared by modifying an iron-chromium-aluminum-cerium-titanium five-element multi-element alloy.

[0030] The inner high-resistivity dense heating mesh is distributed as follows by weight percentage: nickel 68%–72%, chromium 18%–22%, aluminum 3%–5%, yttrium 1%–3%, and molybdenum 3%–5%.

[0031] The outer layer of low-resistivity, loose, heat-dissipating mesh is distributed as follows by mass percentage: iron 63%–67%, chromium 16%–20%, aluminum 8%–12%, cerium 2%–4%, and titanium 3%–5%.

[0032] The inner layer of dense heating mesh has a wire diameter of 0.35mm and a mesh porosity of 32%. The resistance of the inner layer of dense heating mesh is 3.2 times that of the outer layer of low-resistance, loose, and uniform heat dissipation mesh.

[0033] The outer layer has a loose, heat-dissipating mesh with a wire diameter of 0.20 mm and a mesh porosity of 68%.

[0034] Prepare the finished heating mesh according to the following steps: S1. Vacuum arc melting and homogenization annealing: Weigh the alloy powder according to the above-mentioned mass percentage range, melt the inner layer of nickel-chromium-aluminum-yttrium-molybdenum pentagonal alloy and the outer layer of iron-chromium-aluminum-cerium-titanium pentagonal alloy, with a melting vacuum degree ≤5×10Pa, and repeat the melting 4 times to ensure uniform composition; then hold at 1050℃ for 2h for homogenization annealing to eliminate the internal stress of alloy casting. S2, Micro-drawing and surface passivation: Two alloy billets are drawn to the target wire diameter, and then nanoscale surface passivation pretreatment is performed to pre-form an ultra-thin oxide protective layer on the surface of the wire. S3, Gradient Double-Net Synchronous Weaving: Using a double-head synchronous weaving device, a double-layer mesh blank with a dense inner layer and a sparse outer layer is woven in one piece, directly completing the double-layer interlocking and seamless bonding; S4. Vacuum in-situ diffusion welding composite: The double-mesh billet is placed in a vacuum diffusion welding furnace with a vacuum degree ≤3×10Pa and held at 850℃ for 40min to achieve atomic diffusion metallurgical bonding of the interface of the double-layer dissimilar alloy. S5. Post-processing and shaping: The double-mesh blank after diffusion welding is subjected to a low-temperature oxidation coating treatment at 700℃, followed by electrode terminal welding and high-temperature insulating encapsulation to obtain the finished product.

[0035] Furthermore, the inner high-resistivity dense heating mesh also contains 1.2% nano-zirconia ceramic particles; the outer low-resistivity loose uniform heat dissipation mesh also contains 1.0% nano-alumina particles.

[0036] Prepare the finished heating mesh according to the following steps: S1. Take nano-zirconia powder and nano-alumina powder respectively, place them in an oven, and dry them at 120℃ for 2 hours to completely remove the adsorbed water vapor from the powder; then add a trace amount of anhydrous ethanol as a dispersant and perform ultrasonic dispersion treatment with an ultrasonic power of 300W and a dispersion time of 40min. S2. Prepare inner layer alloy powder and outer layer alloy powder separately. The inner layer pentagonal alloy powder and the pretreated nano-zirconia powder are fed into a planetary ball mill according to the specified ratio. The outer layer pentagonal alloy powder and the pretreated nano-alumina powder are fed separately. The grinding media are hard alloy grinding balls with a ball-to-material ratio of 3:1. The ball milling speed is 350 r / min and the dry grinding and mixing time is 2.5 h. S3. The uniformly mixed composite powder is loaded into molds and cold-pressed at room temperature and 25MPa pressure to prepare inner composite alloy preforms and outer composite alloy preforms. S4. Place the two alloy preforms into a vacuum arc melting furnace with a melting vacuum of ≤5×10Pa and melt them repeatedly 4 times to ensure uniform composition. Then, hold at 1050℃ for 2 hours for homogenization annealing to eliminate the internal stress of alloy casting. S5. Micro-drawing and surface passivation: Two alloy billets are drawn to the target wire diameter, and then nano-level surface passivation pretreatment is performed to pre-form an ultra-thin oxide protective layer on the surface of the wire. S6. Gradient Double-Net Synchronous Weaving: Using a double-head synchronous weaving device, a double-layer mesh blank with a dense inner layer and a sparse outer layer is woven in one piece, directly completing the double-layer interlocking and seamless bonding. S7. Vacuum in-situ diffusion welding composite: The double-mesh billet is placed in a vacuum diffusion welding furnace with a vacuum degree ≤3×10Pa and held at 850℃ for 40min to achieve atomic diffusion metallurgical bonding of the interface of the double-layer dissimilar alloy. S8. Post-processing and shaping: The double-mesh blank after diffusion welding is subjected to a low-temperature oxidation coating treatment at 700℃, followed by electrode terminal welding and high-temperature insulating encapsulation to obtain the finished product.

[0037] The following specific examples and comparative examples are provided. Example 1 Inner layer high-resistivity dense heating mesh: nickel 70%, chromium 20%, aluminum 4%, yttrium 2%, molybdenum 4%; outer layer low-resistivity loose uniform heat dissipation mesh: iron 65%, chromium 18%, aluminum 10%, cerium 3%, titanium 4%; inner layer wire diameter 0.35mm, porosity 32%; outer layer low-resistivity loose uniform heat dissipation mesh wire diameter 0.20mm, porosity 68%; diffusion welding vacuum degree 2×10 -3 Hold at 850℃ for 40 minutes.

[0038] Preparation method: S1, Vacuum arc melting and homogenization annealing: Weigh the alloy powder according to the above mass percentage range, melt the inner layer of nickel-chromium-aluminum-yttrium-molybdenum pentagonal alloy and the outer layer of iron-chromium-aluminum-cerium-titanium pentagonal alloy, the melting vacuum degree is ≤5×10Pa, and the melting is repeated 4 times to ensure uniform composition; then, perform homogenization annealing at 1050℃ for 2h to eliminate the internal stress of alloy casting; S2, Micro-drawing and surface passivation: Two alloy billets are drawn to the target wire diameter, and then nanoscale surface passivation pretreatment is performed to pre-form an ultra-thin oxide protective layer on the surface of the wire. S3, Gradient Double-Net Synchronous Weaving: Using a double-head synchronous weaving device, a double-layer mesh blank with a dense inner layer and a sparse outer layer is woven in one piece, directly completing the double-layer interlocking and seamless bonding; S4. Vacuum in-situ diffusion welding composite: The double-mesh billet is placed in a vacuum diffusion welding furnace with a vacuum degree ≤3×10Pa and held at 850℃ for 40min to achieve atomic diffusion metallurgical bonding of the interface of the double-layer dissimilar alloy. S5. Post-processing and shaping: The double-mesh blank after diffusion welding is subjected to a low-temperature oxidation coating treatment at 700℃, followed by electrode terminal welding and high-temperature insulating encapsulation to obtain the finished product.

[0039] Example 2 The inner high-resistivity dense heating mesh consists of 68% nickel, 22% chromium, 3% aluminum, 1% yttrium, and 6% molybdenum; the outer low-resistivity loose uniform heat dissipation mesh consists of 63% iron, 20% chromium, 8% aluminum, 2% cerium, and 5% titanium. The structural and process parameters are completely consistent with those of Example 1.

[0040] Example 3 The inner high-resistivity dense heating mesh consists of 72% nickel, 18% chromium, 5% aluminum, 3% yttrium, and 2% molybdenum; the outer low-resistivity loose uniform heat dissipation mesh consists of 67% iron, 16% chromium, 12% aluminum, 4% cerium, and 3% titanium. The structural and process parameters are completely consistent with those of Example 1.

[0041] Example 4 Based on the five-element alloy ratio of Example 1, the inner layer is doped with 1.2% nano-zirconia ceramic particles and the outer layer is doped with 1.0% nano-alumina ceramic particles.

[0042] Preparation method: S1. Take nano-zirconia powder and nano-alumina powder respectively, place them in an oven, and dry them at 120℃ for 2 hours to completely remove the adsorbed water vapor from the powder; then add a trace amount of anhydrous ethanol as a dispersant and perform ultrasonic dispersion treatment with an ultrasonic power of 300W and a dispersion time of 40min. S2. Prepare inner layer alloy powder and outer layer alloy powder separately. The inner layer pentagonal alloy powder and the pretreated nano-zirconia powder are fed into a planetary ball mill according to the specified ratio. The outer layer pentagonal alloy powder and the pretreated nano-alumina powder are fed separately. The grinding media are hard alloy grinding balls with a ball-to-material ratio of 3:1. The ball milling speed is 350 r / min and the dry grinding and mixing time is 2.5 h. S3. The uniformly mixed composite powder is loaded into molds and cold-pressed at room temperature and 25MPa pressure to prepare inner composite alloy preforms and outer composite alloy preforms. S4. Place the two alloy preforms into a vacuum arc melting furnace with a melting vacuum of ≤5×10Pa and melt them repeatedly 4 times to ensure uniform composition. Then, hold at 1050℃ for 2 hours for homogenization annealing to eliminate the internal stress of alloy casting. S5. Micro-drawing and surface passivation: Two alloy billets are drawn to the target wire diameter, and then nano-level surface passivation pretreatment is performed to pre-form an ultra-thin oxide protective layer on the surface of the wire. S6. Gradient Double-Net Synchronous Weaving: Using a double-head synchronous weaving device, a double-layer mesh blank with a dense inner layer and a sparse outer layer is woven in one piece, directly completing the double-layer interlocking and seamless bonding. S7. Vacuum in-situ diffusion welding composite: The double-mesh billet is placed in a vacuum diffusion welding furnace with a vacuum degree ≤3×10Pa and held at 850℃ for 40min to achieve atomic diffusion metallurgical bonding of the interface of the double-layer dissimilar alloy. S8. Post-processing and shaping: The double-mesh blank after diffusion welding is subjected to a low-temperature oxidation coating treatment at 700℃, followed by electrode terminal welding and high-temperature insulating encapsulation to obtain the finished product.

[0043] Comparative Example 1 The double-layer mesh is made of a conventional electrothermal alloy of 80% nickel, 20% chromium, and 0% aluminum. The wire diameter and porosity of the two layers are completely consistent, with no resistance gradient. The two layers are spot-welded composites without any rare earth or refractory metal modification.

[0044] Comparative Example 2 The invention retains the inner dense and outer sparse gradient double-network structure and vacuum diffusion welding process, but both layers use conventional electrothermal alloys, without adding trace elements such as yttrium, molybdenum, cerium, and titanium, and without multi-element alloy modification.

[0045] The tests were conducted under the following conditions and parameters: room temperature 25℃, normal air pressure, rated operating voltage 220V, rated operating temperature 1250℃; thermal cycling condition: 1250℃ for 10 min → air cooling to room temperature, 20 min per cycle; oxidation weight loss test: 1250℃ continuous constant temperature for 1000 h; all test samples used uniform specifications and dimensions to eliminate test errors caused by external dimensions: overall sample length 100mm, overall width 50mm, total thickness of double-layer mesh 1.2mm, and the weaving width, length, and assembly dimensions of the double-layer mesh were completely consistent; the test indicators included four core parameters: power-on heating time, maximum surface temperature difference, number of thermal cycling fracture failures, and oxidation weight loss rate at 1250℃ for 1000 h, and the data obtained are shown in the table below:

[0046] Compared to the two comparative examples, the five-element multi-element alloy of this invention, combined with an interlayer resistance gradient structure, increases the heating rate by 41.5% to 67.4%. The inner molybdenum element enhances the alloy resistivity, and combined with a dense high-resistivity mesh, it achieves rapid heating within 3 seconds. After the advanced modification with nano-ceramics, the conductive and thermally conductive structure of the matrix is ​​further optimized, and the heating rate is slightly improved again. The surface temperature difference is compressed from the traditional ±12.1℃ to ±2.3℃ to ±2.9℃, a temperature difference reduction of over 80%. The nano-ceramics can further compress the temperature difference to ±1.8℃, and the uniformity of temperature across the entire range is further improved. Comparative example 2, which relies solely on the structural gradient without alloy modification, still has obvious hot spots, proving that the multiple synergistic effects of the outer cerium modification to improve thermal conductivity, the inner heating zone, and the enhancement of the second phase of nano-ceramics are irreplaceable.

[0047] Meanwhile, rare earth yttrium refines the inner grains and titanium buffers the interfacial stress, improving the basic pentagonal alloy solution's thermal cycle life by more than 4 times; after being combined with nano-zirconia phase transformation toughening, crack propagation is effectively blocked, further improving the thermal cycle life by more than 30%, solving the problem of wire breakage under ultra-high temperature extreme conditions. Rare earth cerium induces the formation of a dense alumina film, reducing the oxidation weight loss rate of the basic solution by 91.2%; the outer nano-alumina acts as a nucleation core, further increasing the density of the protective film and reducing the oxidation weight loss rate. No oxidation peeling or interface delamination occurs during long-term continuous service at 1250℃.

[0048] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0049] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A multi-element alloy modified double-mesh heating wire, characterized in that, The heating wire adopts an integrated double-layer mesh structure with inner and outer nesting. The inner and outer layers are completely interwoven and bonded together by vacuum in-situ diffusion welding. The inner layer is a high-resistance dense heating mesh, which is prepared by modifying a nickel-chromium-aluminum-yttrium-molybdenum five-element multi-element alloy. The outer layer is a low-resistance loose uniform heat dissipation mesh, which is prepared by modifying an iron-chromium-aluminum-cerium-titanium five-element multi-element alloy.

2. The multi-alloy modified double-mesh heating wire according to claim 1, characterized in that, The inner high-resistivity dense heating mesh is distributed as follows by weight percentage: nickel 68%–72%, chromium 18%–22%, aluminum 3%–5%, yttrium 1%–3%, and molybdenum 3%–5%.

3. The multi-alloy modified double-mesh heating wire according to claim 1, characterized in that, The outer low-resistivity, loose, uniform heat dissipation mesh is distributed as follows by mass percentage: iron 63%–67%, chromium 16%–20%, aluminum 8%–12%, cerium 2%–4%, and titanium 3%–5%.

4. The multi-alloy modified double-mesh heating wire according to claim 1, characterized in that, The inner layer of dense heating mesh has a wire diameter of 0.35 mm and a mesh porosity of 32%. The resistance of the inner layer of dense heating mesh is 3.2 times that of the outer layer of low-resistance, loose, and uniformly heated heat dissipation mesh.

5. The multi-alloy modified double-mesh heating wire according to claim 1, characterized in that, The outer layer of loose, heat-dissipating mesh has a wire diameter of 0.20 mm and a mesh porosity of 68%.

6. The multi-alloy modified double-mesh heating wire according to claim 1, characterized in that, The inner high-resistivity dense heating mesh also contains 1.2% nano-zirconia ceramic particles.

7. The multi-alloy modified double-mesh heating wire according to claim 1, characterized in that, The outer low-resistivity, loose, heat-dissipating mesh also contains 1.0% nano-alumina particles.

8. A method for preparing a multi-element alloy modified double-mesh heating wire, based on the multi-element alloy modified double-mesh heating wire of claim 1, characterized in that, Includes the following steps: S1. Vacuum arc melting and homogenization annealing: Weigh the alloy powder according to the above-mentioned mass percentage range, melt the inner layer of nickel-chromium-aluminum-yttrium-molybdenum pentagonal alloy and the outer layer of iron-chromium-aluminum-cerium-titanium pentagonal alloy, with a melting vacuum degree ≤5×10Pa, and repeat the melting 4 times to ensure uniform composition; then hold at 1050℃ for 2h for homogenization annealing to eliminate the internal stress of alloy casting. S2, Micro-drawing and surface passivation: Two alloy billets are drawn to the target wire diameter, and then nanoscale surface passivation pretreatment is performed to pre-form an ultra-thin oxide protective layer on the surface of the wire. S3, Gradient Double-Net Synchronous Weaving: Using a double-head synchronous weaving device, a double-layer mesh blank with a dense inner layer and a sparse outer layer is woven in one piece, directly completing the double-layer interlocking and seamless bonding; S4. Vacuum in-situ diffusion welding composite: The double-mesh billet is placed in a vacuum diffusion welding furnace with a vacuum degree ≤3×10Pa and held at 850℃ for 40min to achieve atomic diffusion metallurgical bonding of the interface of the double-layer dissimilar alloy. S5. Post-processing and shaping: The double-mesh blank after diffusion welding is subjected to a low-temperature oxidation coating treatment at 700℃, followed by electrode terminal welding and high-temperature insulating encapsulation to obtain the finished product.

9. The method for preparing a multi-element alloy modified double-mesh heating wire according to claim 8, characterized in that, Includes the following steps: S1. Take nano-zirconia powder and nano-alumina powder respectively, place them in an oven, and dry them at 120℃ for 2 hours to completely remove the adsorbed water vapor from the powder; then add a trace amount of anhydrous ethanol as a dispersant and perform ultrasonic dispersion treatment with an ultrasonic power of 300W and a dispersion time of 40min. S2. Prepare inner layer alloy powder and outer layer alloy powder separately. The inner layer pentagonal alloy powder and the pretreated nano-zirconia powder are fed into a planetary ball mill according to the specified ratio. The outer layer pentagonal alloy powder and the pretreated nano-alumina powder are fed separately. The grinding media are hard alloy grinding balls with a ball-to-material ratio of 3:

1. The ball milling speed is 350 r / min and the dry grinding and mixing time is 2.5 h. S3. The uniformly mixed composite powder is loaded into molds and cold-pressed at room temperature and 25MPa pressure to prepare inner composite alloy preforms and outer composite alloy preforms. S4. Place the two alloy preforms into a vacuum arc melting furnace with a melting vacuum of ≤5×10Pa and melt them repeatedly 4 times to ensure uniform composition. Then, hold at 1050℃ for 2 hours for homogenization annealing to eliminate the internal stress of alloy casting. S5. Micro-drawing and surface passivation: Two alloy billets are drawn to the target wire diameter, and then nano-level surface passivation pretreatment is performed to pre-form an ultra-thin oxide protective layer on the surface of the wire. S6. Gradient Double-Net Synchronous Weaving: Using a double-head synchronous weaving device, a double-layer mesh blank with a dense inner layer and a sparse outer layer is woven in one piece, directly completing the double-layer interlocking and seamless bonding. S7. Vacuum in-situ diffusion welding composite: The double-mesh billet is placed in a vacuum diffusion welding furnace with a vacuum degree ≤3×10Pa and held at 850℃ for 40min to achieve atomic diffusion metallurgical bonding of the interface of the double-layer dissimilar alloy. S8. Post-processing and shaping: The double-mesh blank after diffusion welding is subjected to a low-temperature oxidation coating treatment at 700℃, followed by electrode terminal welding and high-temperature insulating encapsulation to obtain the finished product.

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