High temperature resistant black ceramic coated armored electric heating wire

Abstract

This invention discloses a high-temperature resistant black ceramic-coated armored electric heating wire, relating to the field of industrial electric heating element technology. The heating wire comprises a stainless steel sheath, a magnesium oxide inorganic insulation layer, and a nickel-chromium alloy heating wire. The outer surface of the sheath is coated with a black silicon oxide-based high-temperature resistant ceramic coating. The composite ceramic powder uses nano-SiO2 as a matrix, compounded with multi-element metal oxides and Ce. 0.7 Y 0.3 PO4, 2B2O3·V2O5, K2Ti6O 13 Three types of synergistic modifying components. Its preparation includes armored wire prefabrication, sheath pretreatment, composite ceramic powder preparation, plasma thermal spraying, and vacuum gradient heat treatment. This invention, through the synergistic effect of these three components, enhances the coating's high-temperature oxidation resistance, infrared radiation resistance, salt spray corrosion resistance, and resistance to thermal cycling spalling, extending the high-temperature service life of the armored electric heating wire, making it suitable for high-temperature infrared radiation heating conditions.

Description

Technical Field

[0001] This invention relates to the field of industrial electric heating element technology, and in particular to a high-temperature resistant black ceramic-coated armored electric heating wire. Background Technology

[0002] Armored heating wires are integrated heating elements that encapsulate an electric heating alloy wire within a metal sheath and fill it with a dense insulating oxide layer. Due to their excellent shock resistance, mechanical strength, and insulation properties, they are widely used in industrial high-temperature furnaces, aerospace anti-icing, nuclear power equipment heating, and commercial kitchen appliances. Existing armored heating wires typically consist of an inner heating wire, an outer metal armor tube, and an insulating filler layer between them. During long-term use in high-temperature oxidizing atmospheres, the outer metal tube is prone to high-temperature oxidation and peeling, leading to short circuits or burnout of the heating wire, severely affecting its service life and safety.

[0003] To improve oxidation resistance, existing technologies typically employ pre-oxidation treatment or surface coating with ordinary anti-oxidation coatings. However, these ordinary coatings have weak adhesion to the metal substrate and are prone to peeling under frequent thermal expansion and contraction conditions. Simultaneously, the low thermal emissivity of existing coatings leads to low heating efficiency and high energy consumption. While black ceramic coatings have attracted attention in the heating field due to their high thermal emissivity, existing black ceramic coatings are prone to phase transformation or mismatch with the thermal expansion coefficient of the substrate during long-term use at temperatures above 800℃, resulting in coating cracking, powdering, and failure. Furthermore, they cannot simultaneously meet the multiple requirements of high-temperature colorfastness, high-stability infrared radiation, thermal shock resistance, salt spray resistance, and compatibility with pre-finished armored heating wires for mass production.

[0004] It is evident that developing a high-temperature resistant black ceramic-coated armored electric heating wire with excellent high-temperature performance, high thermal efficiency, high infrared radiation, and corrosion resistance is a pressing problem that needs to be solved in the industry. Summary of the Invention

[0005] To overcome the shortcomings of the above-mentioned technologies, this invention provides a high-temperature resistant black ceramic-coated armored electric heating wire. Through the rational design of the coating formula and the use of processes such as water-cooled temperature-controlled plasma spraying and segmented gradient vacuum heat treatment, the comprehensive performance of the coating in terms of high temperature resistance, infrared radiation, thermal shock resistance, and corrosion resistance is effectively improved. This breaks through the 600℃ operating temperature bottleneck of traditional stainless steel armored heating wires and significantly improves its upper limit of use and thermal efficiency in high-temperature air environments.

[0006] To achieve the above objectives, the technical solution adopted by this invention is: a high-temperature resistant black ceramic-coated armored electric heating wire, comprising an armored electric heating wire body, wherein the armored electric heating wire body is composed of a stainless steel sheath, a magnesium oxide inorganic insulation layer filled within the sheath, and a nickel-chromium alloy heating wire embedded in the insulation layer; a black silicon oxide-based high-temperature resistant ceramic coating is sprayed onto the outer surface of the stainless steel sheath; the black silicon oxide-based high-temperature resistant ceramic coating is formed by thermal spraying and vacuum heat treatment of composite ceramic powder; the composite ceramic powder uses nano-SiO2 as the matrix, and is composited with Fe2O3, MnO2, CuO, and Co2O3 multi-metal oxides, and also contains three types of synergistic modifying components: Ce 0.7 Y 0.3 PO4, 2B2O3·V2O5, K2Ti6O 13 .

[0007] Preferably, the composite ceramic powder has the following composition by mass percentage: Fe2O3 6wt%–10wt%, MnO2 4wt%–7wt%, CuO 3wt%–6wt%, Co2O3 2wt%–5wt%, Ce 0.7 Y 0.3 PO4 1.5wt%~3.5wt%, 2B2O3·V2O5 2.0wt%~4.0wt%, K2Ti6O 13 1.0wt%~2.5wt%, with the balance being nano-SiO2.

[0008] Another object of the present invention is to provide a method for preparing the high-temperature resistant black ceramic-coated armored electric heating wire, comprising the following steps: Step S1: Pre-fabrication of armored electric heating wire body: 304 stainless steel seamless tube is selected as the sheath base material. Nickel-chromium alloy heating wire is coaxially inserted into the stainless steel sheath. High-purity magnesium oxide insulating powder is filled into the annular gap between the sheath and the heating wire. The magnesium oxide inorganic insulation layer is compacted by multiple radial tube shrinking to ensure that the heating wire is centered and the insulating filler is dense and without gaps. The two ends of the tube are sealed at high temperature. After completion, the insulation resistance and rated power are tested by powering on. Finished armored electric heating wires with qualified electrical performance are selected for use. Step S2, Surface pretreatment of stainless steel sheath: Degrease, dry and sandblast roughen the outer surface of the finished armored electric heating wire sheath to obtain a clean and rough surface; Step S3, Preparation of composite ceramic powder: First, weigh each raw material according to the ratio, mix them in a high-energy ball mill for 2.8-3.2 hours, dry and remove impurities, sinter them in air at 1245-1255℃ for 1.8-2.2 hours, cool and crush them, dry ball mill them and pass them through a 300-mesh sieve to obtain composite ceramic powder; Step S4, Ceramic Coating Spraying: Using plasma thermal spraying technology, composite ceramic powder is sprayed onto the surface of the sheath, and layered spraying is used to form a coating with a total thickness of 0.15 to 0.4 mm. During the spraying process, the workpiece is water-cooled and the temperature of the outer wall of the sheath is controlled to ≤280℃. Step S5, Vacuum Post-treatment of Coating: The sprayed semi-finished product is sent into a vacuum furnace and subjected to segmented gradient heating vacuum heat treatment to obtain a high-temperature resistant black ceramic-coated armored electric heating wire.

[0009] Preferably, the oil removal in step S2 involves ultrasonic degreasing with anhydrous ethanol for 14-16 minutes, with the ultrasonic equipment operating at a frequency of 38-42 kHz and an ultrasonic power density of 0.38-0.42 W / cm³. 2 .

[0010] Preferably, the drying in step S2 is carried out in a forced-air constant temperature oven at a temperature of 118-122°C for a drying time of 28-32 minutes.

[0011] Preferably, the sandblasting roughening in step S2 uses 80# white corundum abrasive, and the working pressure is stably controlled at 0.45~0.6MPa.

[0012] Preferably, the plasma thermal spraying process in step S4 specifically involves: feeding composite ceramic powder at a uniform speed, using an arc current of 618-622A, an argon main gas flow rate of 41-43L / min, a hydrogen auxiliary gas flow rate of 6-8L / min, and a spray gun moving speed of 170-190mm / min.

[0013] Preferably, the vacuum degree of the segmented gradient heating vacuum heat treatment in step S5 is ≤8×10⁻⁶. -3 Pa.

[0014] Preferably, the segmented gradient heating vacuum heat treatment in step S5 specifically involves: heating the room temperature at a uniform rate of 3-5℃ / min to 795-805℃ and holding it for 0.5-1h to release the residual mechanical stress on the sprayed surface layer, then continuing to heat the temperature to 950℃-1100℃ and holding it for 1-4 hours; after the holding period, slowly cooling the furnace under vacuum to 200℃ before removing it from the furnace.

[0015] Due to the application of the above technical solution, the present invention has the following beneficial effects: (1) The high-temperature resistant black ceramic-coated armored electric heating wire disclosed in this invention optimizes the multi-component ratio of silicon oxide-based composite ceramic powder, combines it with a multi-metal oxide and three types of special modified components, and adopts an integrated preparation process of water-cooled temperature-controlled plasma spraying and segmented gradient vacuum heat treatment. This effectively solves the industry pain points of poor coating adhesion, high-temperature phase transformation cracking, low thermal emissivity and insufficient corrosion resistance of traditional coatings, breaks through the 600℃ operating temperature bottleneck of traditional stainless steel armored heating wires, and greatly improves the upper limit of high-temperature service and the overall service life of the product.

[0016] (2) The high-temperature resistant black ceramic-coated armored electric heating wire disclosed in this invention, through the synergistic effect of the compound of Fe2O3, MnO2, CuO and Co2O3 multi-metal oxides, and relying on the energy level transition characteristics of multiple transition metal oxides, significantly improves the infrared thermal radiation performance of the coating. Compared with ordinary anti-oxidation coatings, it significantly improves the electrothermal conversion efficiency and reduces equipment energy consumption. At the same time, the mutual doping of multi-metal oxides can refine the ceramic coating grains, suppress the coarsening of coating grains and loosening of structure at high temperature, consolidate the high-temperature stability of the coating, and avoid the defects of high-temperature failure and fading of single oxide coatings.

[0017] (3) The high-temperature resistant black ceramic-coated armored electric heating wire disclosed in this invention, through the precise synergistic effect of three types of modified components, relies on Ce 0.7 Y 0.3 The rare-earth doping stabilizing effect of PO4 effectively regulates the coating's crystal structure, alleviates the thermal expansion coefficient mismatch between the coating and the stainless steel substrate, and suppresses crack initiation and propagation under high-temperature thermal shock conditions. The fluxing and densifying effect of 2B2O3·V2O5 fills the micropores within the coating, improving the coating density and bonding strength with the substrate, thus preventing coating peeling caused by frequent thermal expansion and contraction. Furthermore, K2Ti6O... 13 The whisker toughening and corrosion resistance properties further enhance the coating's resistance to thermal shock and salt spray corrosion, enabling it to operate at temperatures above 800℃ for extended periods without powdering, cracking, or fading.

[0018] (4) The high-temperature resistant black ceramic-coated armored electric heating wire disclosed in this invention adopts a complete process of precise pretreatment of the sheath, water-cooled temperature-controlled plasma layer spraying, and low-vacuum segmented gradient heating heat treatment to precisely control the coating forming quality and internal stress state. This avoids the problems of high-temperature damage to the substrate and stress concentration in the coating during the spraying process, and completely releases the residual mechanical stress of the coating, ensuring that the synergistic performance of each component of the composite ceramic is fully utilized. Finally, an armored electric heating wire with high high temperature resistance, high infrared radiation efficiency, strong thermal shock resistance and excellent corrosion resistance is prepared, which is suitable for the batch application needs of harsh high-temperature working conditions such as industrial high-temperature furnaces and aerospace. Detailed Implementation

[0019] The following description is intended to disclose the invention and enable those skilled in the art to implement it. The preferred embodiments described below are merely examples, and other obvious variations will occur to those skilled in the art.

[0020] Example 1

[0021] A high-temperature resistant black ceramic-coated armored electric heating wire includes an armored electric heating wire body, which is composed of a stainless steel sheath, a magnesium oxide inorganic insulation layer filled within the sheath, and a nickel-chromium alloy heating wire embedded in the insulation layer. A black silicon oxide-based high-temperature resistant ceramic coating is sprayed onto the outer surface of the stainless steel sheath. This black silicon oxide-based high-temperature resistant ceramic coating is formed by thermal spraying and vacuum heat treatment of composite ceramic powder. The composite ceramic powder uses nano-SiO2 as a matrix, and is composited with Fe2O3, MnO2, CuO, and Co2O3 multi-metal oxides, and also contains three types of synergistic modifying components: Ce... 0.7 Y 0.3 PO4, 2B2O3·V2O5, K2Ti6O 13 .

[0022] The composite ceramic powder has the following composition by mass percentage: Fe2O3 6wt%, MnO2 4wt%, CuO 3wt%, Co2O3 2wt%, Ce 0.7 Y 0.3 PO4 1.5wt%, 2B2O3·V2O5 2.0wt%, K2Ti6O 13 1.0 wt%, balance is nano-SiO2.

[0023] A method for preparing the high-temperature resistant black ceramic-coated armored electric heating wire includes the following steps: Step S1: Pre-fabrication of armored electric heating wire body: 304 stainless steel seamless tube is selected as the sheath base material. Nickel-chromium alloy heating wire is coaxially inserted into the stainless steel sheath. High-purity magnesium oxide insulating powder is filled into the annular gap between the sheath and the heating wire. The magnesium oxide inorganic insulation layer is compacted by multiple radial tube shrinking to ensure that the heating wire is centered and the insulating filler is dense and without gaps. The two ends of the tube are sealed at high temperature. After completion, the insulation resistance and rated power are tested by powering on. Finished armored electric heating wires with qualified electrical performance are selected for use. Step S2, Surface pretreatment of stainless steel sheath: Degrease, dry and sandblast roughen the outer surface of the finished armored electric heating wire sheath to obtain a clean and rough surface; Step S3, Preparation of composite ceramic powder: First, weigh each raw material according to the ratio, mix them in a high-energy ball mill for 2.8 h, dry and remove the residue, sinter them in air at 1245℃ for 1.8 h, cool and crush them, dry ball mill them and pass them through a 300-mesh sieve to obtain composite ceramic powder; Step S4, Ceramic Coating Spraying: Using plasma thermal spraying technology, composite ceramic powder is sprayed onto the surface of the sheath, and layered spraying is used to form a coating with a total thickness of 0.15mm. During the spraying process, the outer wall of the sheath is kept at ≤280℃ by water cooling and temperature control. Step S5, Vacuum Post-treatment of Coating: The sprayed semi-finished product is sent into a vacuum furnace and subjected to segmented gradient heating vacuum heat treatment to obtain a high-temperature resistant black ceramic-coated armored electric heating wire.

[0024] In step S2, the oil removal process involves ultrasonic degreasing with anhydrous ethanol for 14 minutes. The ultrasonic equipment operates at a frequency of 38 kHz and a power density of 0.38 W / cm². 2 The drying process described in step S2 is carried out in a forced-air constant temperature oven at a temperature of 118°C for 28 minutes. The sandblasting roughening process described in step S2 uses 80# white corundum abrasive and the working pressure is stably controlled at 0.45 MPa.

[0025] The plasma thermal spraying process described in step S4 specifically involves: feeding the composite ceramic powder at a uniform speed, using an arc current of 618A, an argon main gas flow rate of 41L / min, a hydrogen auxiliary gas flow rate of 6L / min, and a spray gun moving speed of 170mm / min; the vacuum degree of the segmented gradient heating vacuum heat treatment described in step S5 is ≤8×10⁻⁶. -3 Pa; The segmented gradient heating vacuum heat treatment in step S5 is as follows: the room temperature is uniformly heated to 795℃ at a rate of 3℃ / min and held for 0.5h to release the residual mechanical stress on the sprayed surface, and then the temperature is further increased to 950℃ and held for 1 hour; after the holding period, the temperature is slowly cooled to 200℃ under vacuum in the furnace and then removed from the furnace.

[0026] Example 2

[0027] A high-temperature resistant black ceramic-coated armored electric heating wire includes an armored electric heating wire body, which is composed of a stainless steel sheath, a magnesium oxide inorganic insulation layer filled within the sheath, and a nickel-chromium alloy heating wire embedded in the insulation layer. A black silicon oxide-based high-temperature resistant ceramic coating is sprayed onto the outer surface of the stainless steel sheath. This black silicon oxide-based high-temperature resistant ceramic coating is formed by thermal spraying and vacuum heat treatment of composite ceramic powder. The composite ceramic powder uses nano-SiO2 as a matrix, and is composited with Fe2O3, MnO2, CuO, and Co2O3 multi-metal oxides, and also contains three types of synergistic modifying components: Ce... 0.7 Y 0.3 PO4, 2B2O3·V2O5, K2Ti6O 13 .

[0028] The composite ceramic powder has the following composition by mass percentage: Fe2O3 7wt%, MnO2 5wt%, CuO 4wt%, Co2O3 3wt%, Ce 0.7 Y 0.3 PO4 2wt%, 2B2O3·V2O5 2.5wt%, K2Ti6O 13 1.5wt%, with the balance being nano-SiO2.

[0029] A method for preparing the high-temperature resistant black ceramic-coated armored electric heating wire includes the following steps: Step S1: Pre-fabrication of armored electric heating wire body: 304 stainless steel seamless tube is selected as the sheath base material. Nickel-chromium alloy heating wire is coaxially inserted into the stainless steel sheath. High-purity magnesium oxide insulating powder is filled into the annular gap between the sheath and the heating wire. The magnesium oxide inorganic insulation layer is compacted by multiple radial tube shrinking to ensure that the heating wire is centered and the insulating filler is dense and without gaps. The two ends of the tube are sealed at high temperature. After completion, the insulation resistance and rated power are tested by powering on. Finished armored electric heating wires with qualified electrical performance are selected for use. Step S2, Surface pretreatment of stainless steel sheath: Degrease, dry and sandblast roughen the outer surface of the finished armored electric heating wire sheath to obtain a clean and rough surface; Step S3, Preparation of composite ceramic powder: First, weigh each raw material according to the ratio, mix them in a high-energy ball mill for 2.9 h, dry and remove impurities, sinter them in air at 1248℃ for 1.9 h, cool and crush them, dry ball mill them and pass them through a 300-mesh sieve to obtain composite ceramic powder; Step S4, Ceramic Coating Spraying: Using plasma thermal spraying technology, composite ceramic powder is sprayed onto the surface of the sheath, and layered spraying is used to form a coating with a total thickness of 0.2mm. During the spraying process, the outer wall of the sheath is kept at ≤280℃ by water cooling and temperature control. Step S5, Vacuum Post-treatment of Coating: The sprayed semi-finished product is sent into a vacuum furnace and subjected to segmented gradient heating vacuum heat treatment to obtain a high-temperature resistant black ceramic-coated armored electric heating wire.

[0030] In step S2, the oil removal process involves ultrasonic degreasing with anhydrous ethanol for 14.5 minutes. The ultrasonic equipment operates at a frequency of 39 kHz and a power density of 0.39 W / cm³. 2 The drying process described in step S2 is carried out in a forced-air constant temperature oven at a temperature of 119°C for 29 minutes. The sandblasting roughening process described in step S2 uses 80# white corundum abrasive, and the working pressure is stably controlled at 0.48 MPa.

[0031] The plasma thermal spraying process described in step S4 specifically involves: feeding the composite ceramic powder at a uniform speed, using an arc current of 619A, an argon main gas flow rate of 41.5L / min, a hydrogen auxiliary gas flow rate of 6.5L / min, and a spray gun moving speed of 175mm / min; the vacuum degree of the segmented gradient heating vacuum heat treatment described in step S5 is ≤8×10 -3 Pa; The segmented gradient heating vacuum heat treatment in step S5 is as follows: the room temperature is uniformly heated to 798℃ at a rate of 3.5℃ / min and held for 0.7h to release the residual mechanical stress on the sprayed surface, and then the temperature is further increased to 970℃ and held for 2 hours; after the holding period, the temperature is slowly cooled to 200℃ under vacuum in the furnace and then removed from the furnace.

[0032] Example 3

[0033] A high-temperature resistant black ceramic-coated armored electric heating wire includes an armored electric heating wire body, which is composed of a stainless steel sheath, a magnesium oxide inorganic insulation layer filled within the sheath, and a nickel-chromium alloy heating wire embedded in the insulation layer. A black silicon oxide-based high-temperature resistant ceramic coating is sprayed onto the outer surface of the stainless steel sheath. This black silicon oxide-based high-temperature resistant ceramic coating is formed by thermal spraying and vacuum heat treatment of composite ceramic powder. The composite ceramic powder uses nano-SiO2 as a matrix, and is composited with Fe2O3, MnO2, CuO, and Co2O3 multi-metal oxides, and also contains three types of synergistic modifying components: Ce... 0.7 Y 0.3 PO4, 2B2O3·V2O5, K2Ti6O 13 .

[0034] The composite ceramic powder has the following composition by mass percentage: Fe2O3 8wt%, MnO2 5.5wt%, CuO 4.5wt%, Co2O3 3.5wt%, Ce 0.7 Y 0.3 PO4 2.5wt%, 2B2O3·V2O5 3.0wt%, K2Ti6O 13 1.8 wt%, with the balance being nano-SiO2.

[0035] A method for preparing the high-temperature resistant black ceramic-coated armored electric heating wire includes the following steps: Step S1: Pre-fabrication of armored electric heating wire body: 304 stainless steel seamless tube is selected as the sheath base material. Nickel-chromium alloy heating wire is coaxially inserted into the stainless steel sheath. High-purity magnesium oxide insulating powder is filled into the annular gap between the sheath and the heating wire. The magnesium oxide inorganic insulation layer is compacted by multiple radial tube shrinking to ensure that the heating wire is centered and the insulating filler is dense and without gaps. The two ends of the tube are sealed at high temperature. After completion, the insulation resistance and rated power are tested by powering on. Finished armored electric heating wires with qualified electrical performance are selected for use. Step S2, Surface pretreatment of stainless steel sheath: Degrease, dry and sandblast roughen the outer surface of the finished armored electric heating wire sheath to obtain a clean and rough surface; Step S3, Preparation of composite ceramic powder: First, weigh each raw material according to the ratio, mix them in a high-energy ball mill for 3 hours, dry and remove the residue, sinter them in air at 1250℃ for 2 hours, cool and crush them, dry ball mill them and pass them through a 300-mesh sieve to obtain composite ceramic powder. Step S4, Ceramic Coating Spraying: Using plasma thermal spraying technology, composite ceramic powder is sprayed onto the surface of the sheath, and layered spraying is used to form a coating with a total thickness of 0.3mm. During the spraying process, the outer wall of the sheath is kept at ≤280℃ by water cooling and temperature control. Step S5, Vacuum Post-treatment of Coating: The sprayed semi-finished product is sent into a vacuum furnace and subjected to segmented gradient heating vacuum heat treatment to obtain a high-temperature resistant black ceramic-coated armored electric heating wire.

[0036] In step S2, the oil removal process involves ultrasonic degreasing with anhydrous ethanol for 15 minutes. The ultrasonic equipment operates at a frequency of 40 kHz and a power density of 0.4 W / cm³. 2 The drying process described in step S2 is carried out in a forced-air constant temperature oven at a temperature of 120°C for 30 minutes. The sandblasting roughening process described in step S2 uses 80# white corundum abrasive, and the working pressure is stably controlled at 0.53 MPa.

[0037] The plasma thermal spraying process described in step S4 specifically involves: feeding the composite ceramic powder at a uniform speed, using an arc current of 620A, an argon main gas flow rate of 42L / min, a hydrogen auxiliary gas flow rate of 7L / min, and a spray gun moving speed of 180mm / min; the vacuum degree of the segmented gradient heating vacuum heat treatment described in step S5 is ≤8×10 -3 Pa; The segmented gradient heating vacuum heat treatment in step S5 is as follows: the room temperature is uniformly heated to 800℃ at a rate of 4℃ / min and held for 0.8h to release the residual mechanical stress on the sprayed surface, and then the temperature is further increased to 1040℃ and held for 3 hours; after the holding period, the temperature is slowly cooled to 200℃ under vacuum in the furnace and then removed from the furnace.

[0038] Example 4

[0039] A high-temperature resistant black ceramic-coated armored electric heating wire includes an armored electric heating wire body, which is composed of a stainless steel sheath, a magnesium oxide inorganic insulation layer filled within the sheath, and a nickel-chromium alloy heating wire embedded in the insulation layer. A black silicon oxide-based high-temperature resistant ceramic coating is sprayed onto the outer surface of the stainless steel sheath. This black silicon oxide-based high-temperature resistant ceramic coating is formed by thermal spraying and vacuum heat treatment of composite ceramic powder. The composite ceramic powder uses nano-SiO2 as a matrix, and is composited with Fe2O3, MnO2, CuO, and Co2O3 multi-metal oxides, and also contains three types of synergistic modifying components: Ce... 0.7 Y 0.3 PO4, 2B2O3·V2O5, K2Ti6O 13 .

[0040] The composite ceramic powder has the following composition by mass percentage: Fe2O3 9.5wt%, MnO2 6.5wt%, CuO 5.5wt%, Co2O3 4.5wt%, Ce 0.7 Y 0.3 PO4 3wt%, 2B2O3·V2O5 3.5wt%, K2Ti6O 132.3 wt%, with the balance being nano-SiO2.

[0041] A method for preparing the high-temperature resistant black ceramic-coated armored electric heating wire includes the following steps: Step S1: Pre-fabrication of armored electric heating wire body: 304 stainless steel seamless tube is selected as the sheath base material. Nickel-chromium alloy heating wire is coaxially inserted into the stainless steel sheath. High-purity magnesium oxide insulating powder is filled into the annular gap between the sheath and the heating wire. The magnesium oxide inorganic insulation layer is compacted by multiple radial tube shrinking to ensure that the heating wire is centered and the insulating filler is dense and without gaps. The two ends of the tube are sealed at high temperature. After completion, the insulation resistance and rated power are tested by powering on. Finished armored electric heating wires with qualified electrical performance are selected for use. Step S2, Surface pretreatment of stainless steel sheath: Degrease, dry and sandblast roughen the outer surface of the finished armored electric heating wire sheath to obtain a clean and rough surface; Step S3, Preparation of composite ceramic powder: First, weigh each raw material according to the ratio, mix them by high-energy ball milling for 3.1 h, dry and remove impurities, sinter them in air atmosphere at 1253℃ for 2.1 h, cool and crush them, dry ball mill them and pass them through a 300-mesh sieve to obtain composite ceramic powder; Step S4, Ceramic Coating Spraying: Using plasma thermal spraying technology, composite ceramic powder is sprayed onto the surface of the sheath, and layered spraying is used to form a coating with a total thickness of 0.35mm. During the spraying process, the outer wall of the sheath is kept at ≤280℃ by water cooling and temperature control. Step S5, Vacuum Post-treatment of Coating: The sprayed semi-finished product is sent into a vacuum furnace and subjected to segmented gradient heating vacuum heat treatment to obtain a high-temperature resistant black ceramic-coated armored electric heating wire.

[0042] In step S2, the oil removal process involves ultrasonic degreasing with anhydrous ethanol for 15.5 minutes. The ultrasonic equipment operates at a frequency of 41 kHz and a power density of 0.41 W / cm². 2 The drying process described in step S2 is carried out in a forced-air constant temperature oven at a temperature of 121°C for 31 minutes. The sandblasting roughening process described in step S2 uses 80# white corundum abrasive and the working pressure is stably controlled at 0.58 MPa.

[0043] The plasma thermal spraying process described in step S4 specifically involves: feeding the composite ceramic powder at a uniform speed, using an arc current of 621A, an argon main gas flow rate of 42.5L / min, a hydrogen auxiliary gas flow rate of 7.5L / min, and a spray gun moving speed of 185mm / min; the vacuum degree of the segmented gradient heating vacuum heat treatment described in step S5 is ≤8×10 -3Pa; The segmented gradient heating vacuum heat treatment in step S5 is as follows: the room temperature is uniformly heated to 803℃ at a rate of 4.5℃ / min and held for 0.9h to release the residual mechanical stress on the sprayed surface, and then the temperature is further increased to 1070℃ and held for 3.5h; after the holding period, the temperature is slowly cooled to 200℃ under vacuum in the furnace and then removed from the furnace.

[0044] Example 5

[0045] A high-temperature resistant black ceramic-coated armored electric heating wire includes an armored electric heating wire body, which is composed of a stainless steel sheath, a magnesium oxide inorganic insulation layer filled within the sheath, and a nickel-chromium alloy heating wire embedded in the insulation layer. A black silicon oxide-based high-temperature resistant ceramic coating is sprayed onto the outer surface of the stainless steel sheath. This black silicon oxide-based high-temperature resistant ceramic coating is formed by thermal spraying and vacuum heat treatment of composite ceramic powder. The composite ceramic powder uses nano-SiO2 as a matrix, and is composited with Fe2O3, MnO2, CuO, and Co2O3 multi-metal oxides, and also contains three types of synergistic modifying components: Ce... 0.7 Y 0.3 PO4, 2B2O3·V2O5, K2Ti6O 13 .

[0046] The composite ceramic powder has the following composition by mass percentage: Fe2O3 10wt%, MnO2 7wt%, CuO 6wt%, Co2O3 5wt%, Ce 0.7 Y 0.3 PO4 3.5wt%, 2B2O3·V2O5 4.0wt%, K2Ti6O 13 2.5 wt%, with the balance being nano-SiO2.

[0047] A method for preparing the high-temperature resistant black ceramic-coated armored electric heating wire includes the following steps: Step S1: Pre-fabrication of armored electric heating wire body: 304 stainless steel seamless tube is selected as the sheath base material. Nickel-chromium alloy heating wire is coaxially inserted into the stainless steel sheath. High-purity magnesium oxide insulating powder is filled into the annular gap between the sheath and the heating wire. The magnesium oxide inorganic insulation layer is compacted by multiple radial tube shrinking to ensure that the heating wire is centered and the insulating filler is dense and without gaps. The two ends of the tube are sealed at high temperature. After completion, the insulation resistance and rated power are tested by powering on. Finished armored electric heating wires with qualified electrical performance are selected for use. Step S2, Surface pretreatment of stainless steel sheath: Degrease, dry and sandblast roughen the outer surface of the finished armored electric heating wire sheath to obtain a clean and rough surface; Step S3, Preparation of composite ceramic powder: First, weigh each raw material according to the ratio, mix them by high-energy ball milling for 3.2 h, dry and remove impurities, sinter them in air atmosphere at 1255℃ for 2.2 h, cool and crush them, dry ball mill them and pass them through a 300-mesh sieve to obtain composite ceramic powder; Step S4, Ceramic Coating Spraying: Using plasma thermal spraying technology, composite ceramic powder is sprayed onto the surface of the sheath, and layered spraying is used to form a coating with a total thickness of 0.4mm. During the spraying process, the outer wall of the sheath is kept at ≤280℃ by water cooling and temperature control. Step S5, Vacuum Post-treatment of Coating: The sprayed semi-finished product is sent into a vacuum furnace and subjected to segmented gradient heating vacuum heat treatment to obtain a high-temperature resistant black ceramic-coated armored electric heating wire.

[0048] In step S2, the oil removal process involves ultrasonic degreasing with anhydrous ethanol for 16 minutes. The ultrasonic equipment operates at a frequency of 42 kHz and a power density of 0.42 W / cm². 2 The drying process described in step S2 is carried out in a forced-air constant temperature oven at a temperature of 122°C for 32 minutes. The sandblasting roughening process described in step S2 uses 80# white corundum abrasive and the working pressure is stably controlled at 0.6 MPa.

[0049] The plasma thermal spraying process described in step S4 specifically involves: feeding the composite ceramic powder at a uniform speed, using an arc current of 622A, an argon main gas flow rate of 43L / min, a hydrogen auxiliary gas flow rate of 8L / min, and a spray gun moving speed of 190mm / min; the vacuum degree of the segmented gradient heating vacuum heat treatment described in step S5 is ≤8×10⁻⁶. -3 Pa; The segmented gradient heating vacuum heat treatment in step S5 is as follows: the room temperature is uniformly heated to 805℃ at a rate of 5℃ / min and held for 1 hour to release the residual mechanical stress on the sprayed surface, and then the temperature is further increased to 1100℃ and held for 4 hours; after the holding period, the temperature is slowly cooled to 200℃ under vacuum in the furnace and then removed from the furnace.

[0050] Comparative Example 1 A high-temperature resistant black ceramic-coated armored electric heating wire is basically the same as in Example 5, except that it uses an equal amount of Ce. 0.7 Y 0.3 PO4 replaces 2B2O3·V2O5.

[0051] Comparative Example 2 A high-temperature resistant black ceramic-coated armored electric heating wire is basically the same as in Example 5, except that an equal amount of 2B₂O₃·V₂O₅ is used instead of Ce. 0.7 Y 0.3 PO4.

[0052] Comparative Example 3 A high-temperature resistant black ceramic-coated armored electric heating wire is basically the same as in Example 5, except that it uses an equal amount of K2Ti6O. 13 Replace Ce 0.7 Y 0.3 PO4.

[0053] Comparative Example 4 A high-temperature resistant black ceramic-coated armored electric heating wire is basically the same as in Example 5, except that it uses an equal amount of Ce. 0.7 Y 0.3 PO4 replacing K2Ti6O 13 .

[0054] To further illustrate the unexpected positive technical effects achieved by the high-temperature resistant black ceramic-coated armored electric heating wire involved in the embodiments of the present invention, relevant performance tests were conducted on the products involved in Example 5 and Comparative Examples 1-4. The test results are shown in Table 1, and the test methods are as follows: (1) Continuous high temperature durability test in air at 1000℃: constant temperature air muffle furnace, air inside the furnace is circulated at normal pressure, constant temperature is set at 1000℃; the sample is simultaneously powered on at full power and continuously heated for 100h; after 100h, the sheath is dissected and the oxidation corrosion, magnesium oxide insulation layer, and nickel-chromium heating wire integrity are observed. If there is no oxide layer on the inner wall of the stainless steel sheath after dissection, and the magnesium oxide insulation and nickel-chromium heating wire are intact, the high temperature durability is qualified; otherwise, it is unqualified.

[0055] (2) Thermal radiation efficiency test: Standard windless constant temperature test chamber, ambient temperature controlled at 20℃; 2.2kW of rated power is supplied to the sample, and after the sample temperature is stabilized at 800℃, the electric-infrared radiation conversion efficiency of the sample is calculated by blackbody radiation calorimetry.

[0056] (3) Neutral salt spray corrosion resistance test: Refer to GB / T 10125-2021, 5% NaCl continuous spray, continuous salt spray test for 500h, observe the corrosion on the sheath surface and the coating bulging and peeling. If there is no corrosion on the sheath surface and no coating bulging and peeling, the neutral salt spray corrosion resistance is qualified; otherwise, it is unqualified.

[0057] (4) Cold and heat alternating cycle coating anti-peeling test: The test is carried out in accordance with GB / T 7287.5. Cycling conditions: room temperature ↔ 900℃, single heating and cooling cycle 30min, continuous cycle 300 times; observe whether there are cracks or peeling in the coating after 300 cycles. If there are no through cracks or peeling, and the coating is continuous and intact, the cold and heat alternating performance is qualified; otherwise, it is unqualified.

[0058] Table 1

[0059] As can be seen from the test results in Table 1, Example 5 simultaneously combined with Ce0.7 Y 0.3 PO4, 2B2O3·V2O5, K2Ti6O 13 The three modified components passed the high-temperature durability test after 1000℃ for 100h, with an electro-infrared radiation conversion efficiency of 83.1%. After 500h of neutral salt spray testing, the coating showed no blistering or peeling. After 300 cycles of temperature cycling from room temperature to 900℃, the coating showed no through cracks or peeling. However, in Comparative Examples 1-4, the absence of one of the modified components resulted in varying degrees of decrease in the oxygen barrier capacity, infrared radiation performance, corrosion resistance, and thermal shock stability of the coating. This demonstrates that only a synergistic combination of all three components can achieve the comprehensive technical effects of high-temperature oxidation resistance, high infrared radiation, corrosion resistance, and thermal shock resistance. Retaining only two of the modified components cannot achieve the expected comprehensive performance of this invention.

[0060] The above embodiments are only for illustrating the technical concept and features of the present invention. Their purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be used to limit the scope of protection of the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A high-temperature resistant black ceramic-coated armored electric heating wire, characterized in that, The device includes an armored electric heating wire body, which consists of a stainless steel sheath, a magnesium oxide inorganic insulation layer filled in the sheath, and a nickel-chromium alloy heating wire embedded in the insulation layer; a black silicon oxide-based high-temperature resistant ceramic coating is sprayed onto the outer surface of the stainless steel sheath. The black silica-based high-temperature resistant ceramic coating is formed by thermal spraying and vacuum heat treatment of composite ceramic powder; the composite ceramic powder uses nano-SiO2 as the matrix, and is composed of Fe2O3, MnO2, CuO, and Co2O3 multi-metal oxides, and also contains three types of synergistic modifying components: Ce 0.7 Y 0.3 PO4, 2B2O3·V2O5, K2Ti6O 13 .

2. The high-temperature resistant black ceramic-coated armored electric heating wire according to claim 1, characterized in that, The composite ceramic powder has the following composition by mass percentage: Fe2O3 6wt%~10wt%, MnO2 4wt%~7wt%, CuO 3wt%~6wt%, Co2O3 2wt%~5wt%, Ce 0.7 Y 0.3 PO4 1.5wt%~3.5wt%, 2B2O3·V2O5 2.0wt%~4.0wt%, K2Ti6O 13 1.0wt%~2.5wt%, with the balance being nano-SiO2.

3. A method for preparing a high-temperature resistant black ceramic-coated armored electric heating wire according to any one of claims 1-2, characterized in that, The steps include the following: Step S1: Pre-fabrication of armored electric heating wire body: 304 stainless steel seamless tube is selected as the sheath base material. Nickel-chromium alloy heating wire is coaxially inserted into the stainless steel sheath. High-purity magnesium oxide insulating powder is filled into the annular gap between the sheath and the heating wire. The magnesium oxide inorganic insulation layer is compacted by multiple radial tube shrinking to ensure that the heating wire is centered and the insulating filler is dense and without gaps. The two ends of the tube are sealed at high temperature. After completion, the insulation resistance and rated power are tested by powering on. Finished armored electric heating wires with qualified electrical performance are selected for use. Step S2, Surface pretreatment of stainless steel sheath: Degrease, dry and sandblast roughen the outer surface of the finished armored electric heating wire sheath to obtain a clean and rough surface; Step S3, Preparation of composite ceramic powder: First, weigh each raw material according to the ratio, mix them in a high-energy ball mill for 2.8-3.2 hours, dry and remove impurities, sinter them in air at 1245-1255℃ for 1.8-2.2 hours, cool and crush them, dry ball mill them and pass them through a 300-mesh sieve to obtain composite ceramic powder; Step S4, Ceramic Coating Spraying: Using plasma thermal spraying technology, composite ceramic powder is sprayed onto the surface of the sheath, and layered spraying is used to form a coating with a total thickness of 0.15 to 0.4 mm. During the spraying process, the workpiece is water-cooled and the temperature of the outer wall of the sheath is controlled to ≤280℃. Step S5, Vacuum Post-treatment of Coating: The sprayed semi-finished product is sent into a vacuum furnace and subjected to segmented gradient heating vacuum heat treatment to obtain a high-temperature resistant black ceramic-coated armored electric heating wire.

4. The method for preparing the high-temperature resistant black ceramic-coated armored electric heating wire according to claim 3, characterized in that, In step S2, the oil removal process involves ultrasonic degreasing with anhydrous ethanol for 14-16 minutes. The ultrasonic equipment operates at a frequency of 38-42 kHz and a power density of 0.38-0.42 W / cm³. 2 .

5. The method for preparing the high-temperature resistant black ceramic-coated armored electric heating wire according to claim 3, characterized in that, The drying process described in step S2 is carried out in a forced-air constant-temperature oven at a temperature of 118-122°C for 28-32 minutes.

6. The method for preparing the high-temperature resistant black ceramic-coated armored electric heating wire according to claim 3, characterized in that, In step S2, the sandblasting roughening process uses 80# white corundum abrasive, and the working pressure is stably controlled at 0.45-0.6MPa.

7. The method for preparing the high-temperature resistant black ceramic-coated armored electric heating wire according to claim 3, characterized in that, The plasma thermal spraying process described in step S4 is as follows: the composite ceramic powder is fed at a uniform speed, the arc current is 618-622A, the argon main gas flow rate is 41-43L / min, the hydrogen auxiliary gas flow rate is 6-8L / min, and the spray gun moving speed is 170-190mm / min.

8. The method for preparing the high-temperature resistant black ceramic-coated armored electric heating wire according to claim 3, characterized in that, The vacuum degree of the segmented gradient heating vacuum heat treatment in step S5 is ≤8×10⁻⁶. -3 Pa.

9. The method for preparing the high-temperature resistant black ceramic-coated armored electric heating wire according to claim 3, characterized in that, The segmented gradient heating vacuum heat treatment described in step S5 is as follows: the room temperature is uniformly heated to 795-805℃ at a rate of 3-5℃ / min and held for 0.5-1h to release the residual mechanical stress on the sprayed surface layer, and then the temperature is further increased to 950℃-1100℃ and held for 1-4 hours; after the holding period, the temperature is slowly cooled to 200℃ under vacuum in the furnace and then removed from the furnace.

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