Manufacturing method of heating device with spiral structure

Abstract

The invention discloses a manufacturing method of a heating device of a spiral structure. The manufacturing method comprises the steps of casing pipe blanking, casing pipe cleaning and drying, resistance wire machining, resistance wire welding, casing pipe powder filling, pipe rolling, annealing, head cutting, pipe opening sand blasting, pipe bending, sealing and inspection. According to the manufacturing method, the structure and the material of the heating device are improved, the heating efficiency and the transmission efficiency can be improved, the diversified requirements of the heating media can be met, the requirements of efficient heating, rapid heat transmission, diversified heating media and the like of the heating device are met, and therefore the application scene of the heating device can be expanded; and the use requirements are met.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of resistance wire heating device, and particularly relates to a manufacturing method of a spiral structure heating device. BACKGROUND

[0002] The resistance wire heater is used for converting electric energy into heat energy to heat objects by Joule effect of electric current, and is generally divided into direct resistance heating and indirect resistance heating. In the former, the power voltage is directly added to the heated object, and the heated object itself is heated when the current flows. In the indirect resistance heating, the heating element is made of special alloy materials or non-metallic materials, and the heat energy is generated by the heating element and is transmitted to the heated object by radiation, convection and conduction. Since the heated object and the heating element are divided into two parts, the types of the heated object are generally not limited, and the operation is simple.

[0003] At present, the main body structure of the commonly used heating device is mainly made of steel, and the resistance wire is built-in. The resistance wire is made of Cr20Ni30 material, and the heating device is mostly made in U-shaped structure due to its shape structure. The heating device manufactured by the existing method has the following problems: Firstly, the main body structure is made of steel, and the material has poor ductility. When the heating device is rolled and bent, it is easy to break and fracture, resulting in failure of the main body function, and accompanied by the risk of electric leakage.

[0004] Secondly, the main body structure made of steel is easy to rust, has a short service life, and also limits the heating medium.

[0005] Thirdly, the resistance wire is made of Cr20Ni30 material. Since the maximum working temperature of the material is about 800 DEG C, the application in high temperature environment is limited by temperature.

[0006] Fourthly, the resistance wire made of Cr20Ni30 material has poor corrosion resistance and high temperature strength due to the nickel content of about 30%.

[0007] Fifthly, the U-shaped structure heating device has poor heating efficiency and low transmission efficiency, which limits the application scene and cannot meet the use demand.

[0008] In summary, in view of the problems of low heating efficiency and transmission efficiency and single heating medium of the existing heating device, in order to meet the use demand, it is necessary to improve the existing structure, so as to provide a manufacturing method of a spiral structure heating device, which is very necessary. SUMMARY

[0009] The technical problem solved by the present application is to solve the problems in the background art, in order to improve the heating efficiency and transmission efficiency of the existing heating device, and to solve the problem of single heating medium, thereby providing a manufacturing method of a spiral structure heating device which can improve the heating efficiency and transmission efficiency, and can realize various heating media, so as to realize high efficiency of the heating device, rapid heat transfer, and various heating media, and specifically, a manufacturing method of a spiral structure heating device.

[0010] To solve the above technical problems, the technical scheme adopted by the present application is as follows: a manufacturing method of a spiral structure heating device, the manufacturing method comprising the steps of sleeve blanking, sleeve cleaning and drying, resistance wire processing, resistance wire welding, sleeve powder filling, pipe rolling, annealing, head cutting, pipe mouth sandblasting, pipe bending, sealing and inspection, and the specific steps are as follows: S1. Sleeve blanking: select the material for the sleeve in advance, then calculate the total length and diameter of the sleeve according to the required spiral unrolling length and product pipe diameter, and finally perform blanking; S2. Sleeve cleaning and drying: first clean the inside and outside surfaces of the sleeve with gasoline, then place it in a heating furnace for drying until the inside and outside of the sleeve are completely dry; S3. Resistance wire processing: select the material for the resistance wire in advance, calculate the resistance wire blanking resistance length according to the voltage and power used by the resistance wire, then select the resistance wire diameter specification according to the number of spiral turns and the pitch coefficient, and confirm the required processing inner diameter size, to ensure that after the resistance wire is spirally wound and formed, it is stretched, and the pitch after stretching should meet 2-3mm; S4. Resistance wire welding: the resistance wire obtained in step S3 is welded with the conductive rod by gas welding, and the conductive rod needs to be processed in advance before welding; S5. Sleeve powder filling: the sleeve needs to be filled with metal powder with high thermal conductivity and insulation, and the filling needs to be compacted while filling until the powder filling is completed; S6. Pipe rolling: after the sleeve powder filling is completed, the sleeve is cold-rolled to meet the required spiral unrolling length and outer diameter size of the finished product, and the cold rolling needs to be performed multiple times until the specification size is reached; S7. Annealing: annealing treatment is needed after pipe rolling to reduce the hardness of the pipe cold rolling, which facilitates subsequent bending forming, and at the same time, the annealing treatment can promote the hardening of the metal powder filled in the pipe; S8. Head cutting: the workpiece needs to be straightened after annealing, and then the two end heads are cut, requiring the final total length of the workpiece to be less than 68-72mm of the total length of the rolled pipe, and the total length of the pipe mouth to be less than 58-62mm of the final total length of the workpiece; S9. Pipe mouth sandblasting: the workpiece obtained after head cutting needs to be sandblasted at both ends to remove the metal powder to a depth of 5-8mm at both ends, which facilitates subsequent glue filling and sealing; S10. Bending pipe: according to the spiral structure parameters, the workpiece is bent to form and meet the design requirements; S11. Sealing: epoxy resin is poured into the recessed part of the sleeve at both ends of the workpiece, and then the insulator is installed and fixed at the end face to realize the sealing insulation of the metal powder in the workpiece; S12. Inspection: after the workpiece is processed, the pressure resistance value detection, insulation resistance detection and direct current resistance detection are needed to ensure that the workpiece meets the use requirements.

[0011] Further, in the sleeve blanking process of the step S1 of the manufacturing method of the spiral structure heating device, the material of the sleeve is selected to be stainless steel 1Cr18Ni9Ti material, and the specific way of calculating the total length of the sleeve blanking and the pipe diameter of the sleeve according to the required spiral unfolding length of the product and the pipe diameter size of the product is: The sleeve blanking length = the total length of the product unfolding ÷ (1+12%); The sleeve pipe diameter = the product pipe diameter × (1+15%).

[0012] Further, in the sleeve cleaning and drying process of the step S2 of the manufacturing method of the spiral structure heating device, the specific operation way is: The inside and outside surfaces of the sleeve are cleaned with gasoline, and the cleaning frequency is not less than 3 times; The cleaned sleeve is placed in a heating furnace, the temperature in the heating furnace is increased to 150℃, and the baking time is not less than 3h; When the baking is finished, a dust-free cloth is used to pull out the sleeve hole to clean the residual impurities on the inner wall of the pipe to ensure that the pipe is clean.

[0013] Further, in the resistance wire processing process of the step S3 of the manufacturing method of the spiral structure heating device, the material of the resistance wire is selected to be nickel-chromium alloy Cr15Ni60 material; The resistance wire blanking resistance is calculated according to the product use voltage and power, and the specific formula is: ; In the formula, R is the blanking resistance, V is the voltage, and P is the power; According to the number of spiral turns and the pitch coefficient, the resistance wire diameter specification is selected, and the required processing inner diameter size is confirmed, and the specific formula is: The number of spiral turns = (unit: kilo turns); In the formula, R is the blanking resistance, the coefficient value (check the table), D is the resistance wire diameter, and Φ is the resistance wire processing inner hole value; Meanwhile, the pitch = (the sleeve blanking length - the electrically conductive rod length * 2) ÷ the spiral turns; The pitch coefficient = the pitch ÷ the resistance diameter; The pitch coefficient should generally be 2-3mm; Meanwhile, the winding mandrel needs to be prepared, and the mandrel diameter is equal to the resistance wire inner hole value to be processed, and the specific winding mode is: The resistance wire is wound on the mandrel to form a spiral, and after winding, the resistance wire is stretched, and the stretching pitch should be 2-3mm.

[0014] Further, in the resistance wire welding process of the step S4 of the manufacturing method of the spiral structure heating device, the specific requirements for the electrically conductive rod are: A process boss is needed to be processed on one end of the electrically conductive rod, the outer diameter size of the process boss should be the same as the resistance wire winding inner hole size, and the length is 4.5-5.5mm, so as to facilitate the insertion of the process boss into the resistance wire inner hole; When welding, copper welding wire is selected for welding, so as to improve the electrically conductive performance of the resistance wire and reduce the welding seam porosity and slag inclusion welding defects.

[0015] Further, in the sleeve powder filling process of the step S5 of the manufacturing method of the spiral structure heating device, the metal powder is high-temperature magnesium powder, and when filling the powder, the high-temperature magnesium powder weight needs to be calculated, and the specific calculation formula of the high-temperature magnesium powder weight is: m = ρv, In the formula, m is the high-temperature magnesium powder weight, v is the sleeve inner hole volume, and ρ is the high-temperature magnesium powder density; In the powder filling process, the specific powder filling mode is: filling and tamping at the same time until the powder filling is completed; First, seal the lower end of the sleeve with a rubber plug to prevent the high-temperature magnesium powder from leaking during filling; Then use the centering guide rod to penetrate the resistance wire to ensure that the resistance wire is located on the sleeve center axis; When filling the high-temperature magnesium powder into the sleeve, the centering guide rod needs to be used for tamping while filling, and the sleeve needs to be vibrated to ensure that the high-temperature magnesium powder is evenly filled without gaps; Then seal the upper end of the sleeve with a rubber plug to prevent the high-temperature magnesium powder from leaking; Then detect the pressure resistance value to ensure that the pressure resistance is qualified after powder filling; Finally, detect the resistance value to ensure that the resistance wire does not appear short circuit and open circuit during powder filling.

[0016] Further, in the pipe rolling process of the step S6, one-time cold rolling forming cannot be adopted to avoid pipe cracking failure, and repeated cold rolling needs to be performed, and after pipe rolling is completed, the pressure resistance value needs to be detected to ensure that the product after pipe rolling is qualified in pressure resistance, and the direct current resistance value needs to be detected to confirm that the resistance meets the use requirement, wherein the specific formula of the direct current resistance value detection is: ; In the formula, R is the direct current resistance, V is the voltage, and P is the power.

[0017] Further, in the annealing process of the step S7, the specific annealing process condition is that: When the temperature in the heating furnace rises to 300 DEG C, the workpiece is kept in the furnace for 60 min; When the temperature in the heating furnace rises to 550 DEG C, the workpiece is kept in the furnace for 60 min; When the temperature in the heating furnace rises to 800 DEG C, the workpiece is kept in the furnace for 60 min; When the temperature in the heating furnace rises to 1050 DEG C, the workpiece is kept in the furnace for 60 min; Finally, the heating in the furnace is stopped, the workpiece is air-cooled to 250 DEG C in the furnace, and then the workpiece is taken out.

[0018] Further, in the pipe cutting process of the step S8, the specific operation method is that the workpiece needs to be straightened first, and then the two end heads are cut, and the final total length of the workpiece is required to be less than 70 mm of the total length of the pipe, and the total length of the pipe mouth is required to be less than 60 mm of the final total length of the workpiece. In the pipe mouth sandblasting process of the step S9, the specific operation method is that the whole surface of the workpiece is blown with fine sand to remove the impurity oxide skin generated by annealing, and then the two end pipes of the workpiece are blown with fine sand to remove the end surface metal powder, so that the end surface metal powder is ensured to be less than 5-8 mm in depth, and the subsequent glue sealing is facilitated.

[0019] In the pipe bending process of the step S10, the specific operation method is that the workpiece is bent according to the product spiral parameters; then the resistance is detected to confirm that the workpiece is not broken and short-circuited during pipe bending; and finally the pressure resistance value is detected to ensure that the product after bending is qualified in pressure resistance, so as to meet the design requirement.

[0020] Further, in the pipe cutting process of the step S8, the specific operation method is that the workpiece needs to be straightened first, and then the two end heads are cut, and the final total length of the workpiece is required to be less than 70 mm of the total length of the pipe, and the total length of the pipe mouth is required to be less than 60 mm of the final total length of the workpiece. Firstly, the workpiece is placed in the oven for drying, the drying temperature is 200 DEG C, and the drying time is not less than 3 h; Second, the workpiece insulation resistance needs to be detected to be greater than or equal to 100MΩ; Third, the epoxy resin is filled into the recessed sleeve of the end face of the heating pipe, and the insulator is installed and fixed on the end face; Fourth, the product is placed in an oven to dry and cure the epoxy resin, the curing temperature is 180 DEG C, and the curing time is 1h; Fifth, after taking out the product, it is placed in the room, and the natural placement time is not less than 24h, and finally the insulation resistance needs to be detected to be greater than or equal to 50MΩ, that is, the product is qualified; And for the step S12 inspection process, the specific detection requirements include the following aspects: First, the withstand voltage value of the finished product is detected, the high voltage withstand voltage value should be greater than or equal to 2000V, and the low voltage withstand voltage value should be greater than or equal to 1500V; Second, the insulation resistance value should be greater than or equal to 50MΩ; Third, the direct current resistance is detected: .

[0021] Compared with the prior art, the manufacturing method of the spiral structure heating device has the beneficial effects that: the main structure of the heating device is made of stainless steel 1Cr18Ni9Ti material, which has high ductility and plasticity, good rust resistance, and various heating media; at the same time, the built-in resistance wire is made of nickel-chromium alloy Cr15Ni60, which has a maximum working temperature of 1000 DEG C, and the material contains 60% of nickel, which has high corrosion resistance and high temperature resistance; in addition, the main structure of the heating device adopts a spiral structure, which can greatly improve the heating efficiency and transmission efficiency compared with the conventional U-shaped structure, and has the advantages of high heating efficiency and fast heat transfer.

[0022] As described above, by improving the structure and material of the heating device, the manufacturing method can improve the heating efficiency and transmission efficiency, and realize the diversification of the heating medium, realize the high efficiency of the heating device, the rapid heat transfer, and the diversification of the heating medium, so as to expand the application scene of the heating device, and meet the use demand. BRIEF DESCRIPTION OF DRAWINGS

[0023] The application will be described in further detail below with reference to the drawings.

[0024] Figure 1 The manufacturing process flowchart of the application is shown in the figure. DETAILED DESCRIPTION

[0025] The embodiments of the application will be described below by specific examples, and those skilled in the art can easily understand other advantages and effects of the application from the disclosed content.

[0026] It is to be understood that the terms "including", "comprising", or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but can also include other elements not expressly listed or inherent to such process, method, article, or apparatus.

[0027] As shown in Figure 1 The manufacturing method of the spiral structure heating device provided by the embodiment comprises the following steps: sleeve blanking, sleeve cleaning and drying, resistance wire processing, resistance wire welding, sleeve powder loading, pipe rolling, annealing, head cutting, pipe mouth sandblasting, pipe bending, sealing, and inspection. S1. Sleeve blanking: the sleeve material is selected from stainless steel; the total length and the pipe diameter of the sleeve are calculated according to the required spiral unfolding length and the pipe diameter of the product, and the calculation includes the following aspects: First, the sleeve material is selected from stainless steel 1Cr18Ni9Ti, which has high ductility and plasticity, providing a reliable material for spiral structure processing. In addition, the corrosion resistance of the material makes it suitable for various application environments. Second, the total length and the pipe diameter of the sleeve are calculated according to the required spiral unfolding length and the pipe diameter of the product.

[0028] (1) Sleeve blanking length = product unfolding total length ÷ (1 + 12%); (2) Sleeve pipe diameter = product pipe diameter × (1 + 15%); S2. Sleeve cleaning and drying: the inside and outside surfaces of the sleeve are cleaned with gasoline, and then dried in an oven, which includes the following aspects: First, the inside and outside surfaces of the sleeve are cleaned with gasoline, and the cleaning is performed at least 3 times. Second, the cleaned sleeve is placed in an oven, and the temperature in the oven is heated to 150°C for at least 3 hours. Third, when taking out the sleeve after drying, a dust-free cloth is inserted into the hole of the sleeve and pulled out to clean the residual impurities on the inner wall of the sleeve, ensuring that the inside of the sleeve is clean and dry.

[0029] S3. Resistance wire processing: the resistance wire material is selected from nickel-chromium alloy material; the resistance wire blanking resistance is calculated according to the product voltage and power, and then the resistance wire diameter specification is selected according to the number of spiral turns and the pitch coefficient, and the required processing inner diameter size is confirmed. After the resistance wire is spirally wound and formed, it is stretched, and the pitch after stretching should be 2-3 mm, which includes the following aspects: First, the resistance wire material is selected from nickel-chromium alloy Cr15Ni60 material, which contains 60% nickel. Due to its high corrosion resistance and high temperature resistance, it can greatly improve the heating efficiency and service life. Second, according to the product voltage and power calculation resistance wire blanking resistance; ; In the formula: R - blanking resistance, V - voltage, P - power; Third, according to the number of turns and pitch coefficient to select the resistance wire diameter specification and confirm the required processing inner diameter size; (1) the number of turns = (thousand turns); In the formula: R - blanking resistance, coefficient value (check table), D - resistance wire diameter, Φ - resistance wire processing inner hole value; (2) pitch = (sleeve blanking length - conductive rod length x 2) ÷ the number of turns; (3) pitch coefficient = pitch ÷ resistance diameter; Note: pitch coefficient should generally be in line with 2 ~ 3 mm.

[0030] Fourth, prepare winding mandrel, mandrel diameter equal to the resistance wire processing inner hole value; Five resistance wire winding mandrel spiral winding forming, after winding stretch, stretch pitch should be in line with 2 ~ 3 mm.

[0031] S4. resistance wire welding: resistance wire and conductive rod using gas welding, before welding, the conductive rod one end needs to be processed a process boss forming, the process boss outer diameter size should be equal to the resistance wire winding inner hole size, that is, the same, and its length is about 5 mm or so, so that the process boss inserted into the resistance wire inner hole welding forming, in the welding process, including the following several aspects of the content: One is to process the conductive rod, the total length of the conductive rod is about 180 mm or so, the conductive rod one end of the process boss, the process boss outer diameter size is equal to the resistance wire winding inner hole size, the length is about 5 mm, which is convenient for the process boss inserted into the resistance wire inner hole welding forming; Two is to use gas welding to form resistance wire and conductive rod, select copper welding wire welding, improve the conductivity and reduce the welding defects such as porosity, slag inclusion.

[0032] S5. sleeve powder filling: sleeve is filled with high temperature magnesium powder, because of the high temperature magnesium powder has high thermal conductivity and insulation, high safety in use, and need to fill in the powder while ramming until the powder filling is completed, including the following several aspects of the content: One is to calculate the filling high temperature magnesium powder weight, high temperature magnesium powder has high thermal conductivity and insulation, high safety in use; the specific calculation formula of high temperature magnesium powder weight is: m = ρv, In the formula, m - high temperature magnesium powder weight, v - sleeve inner hole volume, ρ - high temperature magnesium powder density; Second, the rubber plug seals the lower end of the sleeve to prevent magnesium powder from leaking during filling; Third, the guide rod is used to pass through the resistance wire to ensure that the resistance wire is located on the central axis of the sleeve; Fourth, high-temperature magnesium powder is filled into the sleeve. When filling the high-temperature magnesium powder, the centering guide rod is used for tamping, and the sleeve is vibrated to ensure uniform filling of the high-temperature magnesium powder without gaps; Fifth, the rubber plug seals the upper end of the sleeve to prevent magnesium powder from leaking; Sixth, the pressure resistance value is detected to ensure that the product after filling is pressure-resistant; Seventh, the resistance value is detected to confirm that the resistance wire is not short-circuited or open-circuited during powder filling.

[0033] S6. Pipe rolling: the sleeve is cold-rolled to achieve the required spiral unwinding length and outer diameter size of the product. Cold rolling is performed multiple times until the specified size is reached. One-time cold rolling is not allowed to avoid pipe cracking and failure. The specific contents include the following aspects: First, the sleeve is rolled after powder filling to achieve the required spiral unwinding length and outer diameter size of the product. Multiple cold rolling is required to avoid tearing of the sleeve, which may lead to failure of the device; Second, the pressure resistance value is detected to ensure that the product after rolling is pressure-resistant; Third, the direct current resistance value is detected to confirm that the resistance meets the use requirements. The specific formula for detecting the direct current resistance value is: ; Where R is the direct current resistance, V is the voltage, and P is the power.

[0034] S7. Annealing: annealing after pipe rolling to reduce the hardness of the pipe after cold rolling, which facilitates subsequent bending and shaping, and also promotes the hardening of the magnesium powder in the pipe. The specific contents include the following aspects: First, the product is annealed after pipe rolling to reduce the hardness of the pipe after cold rolling, which facilitates subsequent bending and shaping, and also promotes the hardening of the magnesium powder in the pipe, thereby improving the service life of the heating device.

[0035] (1) The temperature in the heating furnace rises to 300℃, and the workpiece is kept in the furnace for 60 minutes; (2) The temperature in the heating furnace rises to 550℃, and the workpiece is kept in the furnace for 60 minutes; (3) The temperature in the heating furnace rises to 800℃, and the workpiece is kept in the furnace for 60 minutes; (4) The temperature in the heating furnace rises to 1050℃, and the workpiece is kept in the furnace for 60 minutes; (5) Stop heating in the furnace, and the workpiece is air-cooled in the furnace to 250℃ before being taken out.

[0036] S8. Cutting head: the workpiece needs to be straightened after annealing, and then the two end heads are cut, which includes the following aspects: First, the workpiece is straightened; Second, cut the two end heads of the workpiece to ensure that the final total length of the workpiece is less than 70mm of the total length of the pipe, and the total length of the pipe end is less than 60mm of the final total length of the workpiece; S9. Sandblasting of pipe end: sandblasting of both ends of the workpiece to remove high-temperature magnesium powder at both ends of the pipe, which includes the following aspects: First, sandblasting the entire surface of the workpiece to remove impurities and scale generated during annealing; Second, sandblasting the end of the workpiece to remove high-temperature magnesium powder, ensuring that the high-temperature magnesium powder is 5-8mm deep, which facilitates subsequent glue sealing.

[0037] S10. Bending pipe: bending the workpiece according to the spiral structure parameters, which includes the following aspects: First, bend the workpiece according to the product spiral parameters; Second, detect the resistance to confirm that the workpiece is not broken or short-circuited when bending; Third, detect the pressure value to ensure that the product is pressure-resistant after bending; S11. Sealing: epoxy resin is poured into the end face sleeve of the workpiece, and the insulator is installed and fixed at the end face to seal and insulate the magnesium powder inside the workpiece, which includes the following aspects: First, dry the workpiece in an oven with a drying temperature of 200℃ for not less than 3h; Second, detect the insulation resistance of the workpiece, which should be greater than or equal to 100MΩ; Third, pour epoxy resin into the end face sleeve of the heated pipe, and install and fix the insulator at the end face; Fourth, place the product in an oven to dry and cure the epoxy resin, with a curing temperature of 180℃ and a curing time of 1h; Fifth, take out the product and place it in a room for natural placement for not less than 24h, and detect the insulation resistance, which should be greater than or equal to 50MΩ, indicating that the product is qualified.

[0038] S12. Inspection: after the workpiece is processed, the pressure resistance, insulation resistance and direct current resistance are detected to ensure that the workpiece meets the use requirements, which includes the following aspects: First, test the pressure resistance of the finished product, which should be greater than or equal to 2000V for high pressure and greater than or equal to 1500 for low pressure; Second, the insulation resistance should be greater than or equal to 50MΩ; Third, detect the direct current resistance: .

[0039] It can be seen that, by using the manufacturing method, the main body structure of the heating device is made of stainless steel 1Cr18Ni9Ti material, which has high ductility and plasticity, good rust resistance, and various heating media; at the same time, the built-in resistance wire is made of nickel-chromium alloy Cr15Ni60, which has a maximum working temperature of 1000 DEG C, and the material contains 60% of nickel, which has high corrosion resistance and high temperature resistance; in addition, the main body structure of the heating device adopts a spiral structure, which can greatly improve the heating efficiency and transmission efficiency compared with the conventional U-shaped structure, and has the advantages of high heating efficiency and fast heat transfer.

[0040] In summary, by using the manufacturing method, the structure and material of the heating device are improved, which can not only improve the heating efficiency and transmission efficiency, but also realize the diversification of the heating medium, realize the high efficiency of the heating device, the fast heat transfer, and the diversification of the heating medium, so as to expand the application scene of the heating device, and meet the use demand.

[0041] The other details of the present application are well known to those skilled in the art.

[0042] The protection scope of the present application is not limited to the technical solutions disclosed in the specific embodiments, and the above description is only the preferred embodiment of the present application, and does not limit the present application, any slight modification, equivalent replacement and improvement according to the technical solutions of the present application should be included in the protection scope of the technical solutions of the present application.

Claims

1. A method for manufacturing a spiral heating device, characterized in that, The manufacturing method includes the following steps: sleeve blanking, sleeve cleaning and drying, resistance wire processing, resistance wire welding, sleeve powder loading, tube rolling, annealing, head cutting, tube end sandblasting, tube bending, sealing, and inspection. The specific steps are as follows: S1. Sleeve cutting: Select the material for the sleeve in advance, and then calculate the total length and diameter of the sleeve according to the required spiral unfolding length and the diameter of the product. Finally, cut the sleeve. S2. Casing cleaning and drying: First, use gasoline to clean the inner and outer surfaces of the casing, then place it in a heating furnace to dry until the casing is completely dry inside and out; S3. Resistance wire processing: Select the material for the resistance wire in advance, calculate the resistance length of the resistance wire according to the voltage and power of the resistance wire, and then select the diameter specification of the resistance wire according to the number of spiral turns and pitch coefficient, and confirm the required inner diameter size to ensure that after the resistance wire is spirally wound and stretched, the pitch after stretching should be 2-3mm. S4. Resistance wire welding: The resistance wire obtained in step S3 is welded to the conductive rod using gas welding. Before welding, the conductive rod needs to be pre-formed. S5. Bushing Powder Filling: The bushing must be filled with metal powder with high thermal conductivity and insulation. During the filling process, the powder must be compacted while filling until the filling is completed. S6. Rolling: After the sleeve is loaded with powder, it is cold rolled to achieve the required spiral unfolding length and outer diameter of the finished product. During cold rolling, multiple cold rolling processes are required until the specified dimensions are achieved. S7. Annealing: After rolling, the tube needs to be annealed to reduce the cold rolling hardness of the tube, making it easier to bend and form later. At the same time, annealing can promote the solid hardening of the metal powder filling the tube. S8. Head cutting: After annealing, the workpiece needs to be straightened and then the two ends are cut off. The final total length of the workpiece is required to be 68-72mm less than the total length of the rolled tube, and the total length of the tube opening is required to be 58-62mm less than the final total length of the workpiece. S9. Sandblasting at the pipe ends: The workpiece obtained after the head is cut needs to have the pipe ends sandblasted to remove metal powder at both ends down to a depth of 5-8mm, which will facilitate subsequent glue filling and sealing. S10. Pipe bending: Bending the workpiece according to the spiral structure parameters to make it meet the design requirements; S11. Sealing: Epoxy resin is injected into the recessed parts of the end face sleeves at both ends of the workpiece, and then the insulator is installed and fixed at the end face to achieve sealing and insulation of the metal powder inside the workpiece. S12. Inspection: After the workpiece is processed, it is necessary to perform withstand voltage test, insulation resistance test and DC resistance test to ensure that the workpiece meets the usage requirements.

2. The manufacturing method according to claim 1, characterized in that: In step S1, during the sleeve cutting process, the sleeve material is selected as stainless steel 1Cr18Ni9Ti. The specific method for calculating the total cutting length and sleeve diameter based on the required spiral unfolding length and product diameter is as follows: Sleeve blanking length = Total unfolded product length ÷ (1 + 12%); The casing diameter = product diameter × (1 + 15%).

3. The manufacturing method according to claim 1, characterized in that: The specific operation method for the sleeve cleaning and drying process in step S2 is as follows: Clean the inner and outer surfaces of the bushing with gasoline, repeating the cleaning process at least three times. Place the cleaned sleeve into the heating furnace, raise the temperature of the heating furnace to 150℃, and bake for no less than 3 hours; When removing the tube after baking, use a lint-free cloth to pull it out through the inner hole of the tube to clean any remaining impurities on the inner wall of the tube and ensure that the inside of the tube is clean.

4. The manufacturing method according to claim 1, characterized in that: In the resistance wire processing step S3, the material of the resistance wire is selected as nickel-chromium alloy Cr15Ni60. The resistance of the resistance wire is calculated based on the product's operating voltage and power. The specific formula is as follows: ； In the formula, R is the feeding resistance; V is the voltage; and P is the power. Based on the number of spiral turns and the pitch coefficient, the diameter of the resistance wire is selected, and the required inner diameter is determined. The specific formula is as follows: Number of spiral turns = (Unit: thousands of revolutions); In the formula, R -- feeding resistance, --Coefficient value, D--resistance wire diameter, Φ--resistance wire machining inner hole value; Meanwhile, the pitch = (sleeve blanking length - conductive rod length × 2) ÷ number of spiral turns; Pitch factor = Pitch ÷ Resistor diameter; The pitch coefficient should generally be 2-3 mm; At the same time, a mandrel needs to be prepared. The diameter of the mandrel is equal to the inner hole value that the resistance wire needs to be machined. The specific winding method is as follows: The resistance wire is wound into a spiral shape around a mandrel. After winding, it is stretched, and the stretching pitch should be 2-3 mm.

5. The manufacturing method according to claim 1, characterized in that: The specific requirements for the forming of the conductive rod during the resistance wire welding process in step S4 are as follows: A process boss needs to be machined at one end of the conductive rod. The outer diameter of the process boss should be the same as the inner diameter of the resistance wire winding, and the length should be 4.5 to 5.5 mm, so that the process boss can be inserted into the inner hole of the resistance wire. During welding, copper welding wire is used to improve the conductivity of the resistance wire and reduce weld defects such as porosity and slag inclusions.

6. The manufacturing method according to claim 1, characterized in that: In step S5, during the sleeve filling process, the metal powder is filled with high-temperature magnesium powder. When filling the sleeve, the weight of the high-temperature magnesium powder needs to be calculated. The specific formula for calculating the weight of the high-temperature magnesium powder is as follows: m=ρv, In the formula, m -- weight of high-temperature magnesium powder, v -- volume of the inner hole of the casing, ρ -- density of high-temperature magnesium powder; During the powder filling process, the specific method is as follows: the powder needs to be filled and compacted simultaneously until the powder filling is completed; First, use a rubber stopper to seal the lower end of the sleeve to prevent leakage during the filling of high-temperature magnesium powder; Then, use a centering guide rod to insert the resistance wire to ensure that the resistance wire is located on the central axis of the sleeve. When filling the sleeve with high-temperature magnesium powder, it is necessary to use a centering guide rod to compact it while filling, and the sleeve must be vibrated continuously to ensure that the high-temperature magnesium powder is filled evenly and without gaps. Then, use a rubber stopper to seal the upper end of the sleeve to prevent the loss of high-temperature magnesium powder; Then test the pressure resistance value to ensure that the pressure resistance is qualified after powder filling; Finally, the resistance value is checked to confirm that there are no short circuits or open circuits when the resistance wire is filled with powder.

7. The manufacturing method according to claim 1, characterized in that: In step S6 of the tube rolling process, cold rolling cannot be performed in a single step to avoid tube cracking and failure. Multiple cold rolling cycles are required. After rolling, firstly, the withstand voltage value needs to be tested to ensure the product meets pressure resistance requirements; secondly, the DC resistance value needs to be tested to confirm that the resistance meets usage requirements. The specific formula for testing the DC resistance value is as follows: ； In the formula, R is the DC resistance, V is the voltage, and P is the power.

8. The manufacturing method according to claim 1, characterized in that: For the annealing process in step S7, the specific annealing process conditions are as follows: When the temperature inside the heating furnace rises to 300℃, the workpiece is held in the furnace for 60 minutes. When the temperature inside the heating furnace rises to 550℃, the workpiece is held in the furnace for 60 minutes. When the temperature inside the heating furnace rises to 800℃, the workpiece is held at that temperature for 60 minutes. When the temperature inside the heating furnace rises to 1050℃, the workpiece is held in the furnace for 60 minutes. Finally, stop heating in the furnace, allow the workpiece to air cool inside the furnace to a furnace temperature of 250°C, and then remove it.

9. The manufacturing method according to claim 1, characterized in that: The specific operation method for the head cutting process in step S8 is as follows: First, the workpiece needs to be straightened, and then the two ends are cut off. The final total length of the workpiece is required to be less than the total length of the rolled tube by 70mm, and the total length of the tube opening is less than the final total length of the workpiece by 60mm. For the step S9 pipe opening sand blowing process, the specific operation method is as follows: first, blow fine sand on the entire surface of the workpiece to remove the impurities and oxide scale generated by the annealing of the workpiece surface; then blow fine sand on the pipe openings at both ends of the workpiece to remove the end face metal powder, ensuring that the end face metal powder is lowered to a depth of 5-8mm, which is convenient for subsequent glue filling and sealing. As for the bending process in step S10, the specific operation method is as follows: first, bend the workpiece into shape according to the product's spiral parameters; then, check the resistance to confirm that there is no open circuit or short circuit when bending the workpiece; finally, check the withstand voltage value to ensure that the product's compressive strength is qualified after bending, so that it meets the design requirements.

10. The manufacturing method according to claim 1, characterized in that: The specific operation method for the sealing process in step S11 includes the following aspects: First, the workpiece is placed in an oven to dry at a temperature of 200℃ for a duration of not less than 3 hours. Secondly, the insulation resistance of the workpiece must be ≥100MΩ. Third, epoxy resin is poured into the recessed sleeves at both ends of the heating tube, and the insulators are installed and fixed to the end faces. Fourth, place the product in an oven to dry and cure the epoxy resin at a temperature of 180℃ for 1 hour. Fifth, after removing the product, place it indoors and let it sit naturally for no less than 24 hours. Finally, the insulation resistance needs to be tested to be ≥50MΩ, which means the product is qualified. The specific testing requirements for step S12 include the following aspects: First, inspect the withstand voltage of the finished product. The high voltage withstand voltage should be ≥2000V, and the low voltage withstand voltage should be ≥1500V. Secondly, the insulation resistance value should be ≥50MΩ; Third, test the DC resistance: .

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