Manufacturing method of high-precision reducing seamless heat transfer tube with internal tooth structure

Abstract

The invention discloses a manufacturing method of a high-precision reducing seamless heat transfer tube with an internal tooth structure. The manufacturing method comprises the following steps: a, manufacturing a high-precision light tube intermediate product of the heat transfer tube; b, the intermediate product is subjected to first-time cold machining, so that an internal tooth structure of the whole pipe is formed, the tooth shape size is slightly higher and slightly narrower than the final tooth shape, and the intermediate product with teeth is obtained; c, one end of the toothed intermediate product is subjected to secondary cold machining, diameter and wall reduction is conducted, the wall reduction amount is S1, at the moment, the tooth-shaped structure of the inner mold is the final tooth-shaped size, and a small-diameter section is obtained; and d, the other end of the intermediate product with the teeth is subjected to third-time cold machining from the cold machining stopping position of the small-diameter section, the diameter and the wall of the intermediate product are reduced, the wall reduction amount is S2, S2 is smaller than S1, at the moment, the tooth-shaped structure of the inner mold is the final tooth-shaped size, and a large-diameter section is obtained. The seamless heat transfer pipe manufactured through the method has the advantages of being high in size precision, special in inner surface structure, variable in outer diameter, smooth in transition and excellent in pipe body straightness, and the functions of heat transfer and medium flow channel providing can be achieved at the same time.

Description

Technical Field

[0001] The present invention belongs to the technical field of heat transfer tubes for high-end equipment and new energy systems, and in particular relates to a method for manufacturing a high-precision variable-diameter seamless heat transfer tube with an internal tooth structure. Background Art

[0002] With the development of high-end equipment industry and new nuclear energy system industry, equipment miniaturization, modularization and high efficiency are inevitable development trends. Especially for new nuclear energy systems, they require high power generation, small size, and improved safety and reliability. Therefore, optimizing the reactor structure design, improving heat transfer efficiency, and reducing the risk and weak links of material use are the key to improving the competitiveness of this technology.

[0003] Heat transfer tubes are core components of the reactor. Their function is to transfer the heat generated by the core of the nuclear reactor to the outside of the core for secondary power generation. The inner surface of the heat transfer tube of the new nuclear energy system needs to be designed with a medium flow channel; the outer surface is mainly divided into two parts: the outer surface at one end of the core is a plain tube, and the end outside the core is designed with a finned structure to enhance heat dissipation by increasing the outer surface area of ​​the tube.

[0004] In order to improve the overall performance consistency of the pipe and reduce welding and internal weak links, the above-mentioned complex structure should be formed in one piece as much as possible, which puts forward new requirements for the manufacturing process.

[0005] Usually, the heat transfer tube is a conventional structural steel tube. In order to enhance heat dissipation, a certain number of fins are processed in a certain area on the outer surface of the steel tube. The inner wall of the tube is generally a plain tube structure, and then other materials such as mesh and sleeve are added to the tube to construct the medium flow channel. However, there are several problems in such conventional products and manufacturing technologies: (1) Most steel pipes are welded steel pipes. The weld area is the weak link of the material and a potential high-risk area. During long-term operation, failure is likely to occur in this area, affecting system operation.

[0006] (2) After the fins are processed, the remaining wall thickness of the tube in the fin area is inconsistent with the wall thickness of the unprocessed fin. The fin area is thinner. During long-term operation, the thin-walled area is more likely to have a risk of failure. In addition, the excessive thickness of the tube wall of the unprocessed fin is not conducive to heat transfer in the tube and has low efficiency.

[0007] (3) The medium flow channel constructed by adding other materials such as mesh and sleeve in the tube is unstable and prone to blockage and interface adhesion. In addition, due to the additional materials, the overall structure is uneven and the heat transfer efficiency between different tubes is inconsistent. Summary of the invention

[0008] The purpose of the present invention is to provide a method for manufacturing a high-precision variable diameter seamless heat transfer tube with an internal tooth structure, in which the internal tooth groove structure and the outer diameter variable diameter structure are integrated on a pipe material to achieve manufacturing, and the heat transfer tube obtained has the functions of heat transfer and providing a medium flow channel.

[0009] In order to achieve the above object, the present invention adopts the following technical scheme: A method for manufacturing a high-precision variable-diameter seamless heat transfer tube with an internal tooth structure, wherein the inner wall of the seamless heat transfer tube has longitudinal toothed grooves, and the outer diameter includes a small diameter section and a large diameter section connected in one piece; the method is characterized in that the method comprises the following steps: a. Process the tube blank to obtain a high-precision heat transfer tube intermediate product; b. Use the toothed inner die to perform the first cold working on the intermediate product, so that the internal tooth structure of the entire pipe is formed; the tooth shape is slightly higher and narrower than the final tooth shape, and the toothed intermediate product is obtained; c. Perform a second cold working on one end of the toothed intermediate product to reduce the diameter and wall; the wall reduction amount is S1. At this time, the inner die tooth profile structure is the final tooth profile size, and a small diameter section is obtained; d. The other end of the intermediate toothed product is subjected to a third cold working from the point where the cold working of the small diameter section stops, so as to reduce the diameter and wall. The wall reduction amount is S2, S2<S1. At this time, the tooth profile structure of the inner die is the final tooth profile size, and the large diameter section is obtained.

[0010] Since the inner wall of the seamless heat transfer tube in the present invention has longitudinal tooth-shaped grooves and the outer surface also has a variable diameter structure, the structure is complex. The processing process involves not only diameter reduction and wall reduction, but also the forming process of the special-shaped inner wall. If the inner wall forming and diameter reduction and wall reduction are simply carried out at the same time, the wall reduction amount of the pipe in a single pass is too large, and the precision rolling of the pipe of this specification cannot be guaranteed. Therefore, considering the needs of both internal tooth forming and variable diameter forming, three cold processing links are determined. In addition, the tooth shape of the intermediate product is slightly higher and narrower than the final tooth shape, which can ensure that the inner teeth of the intermediate product are aligned with the inner mold during the second and third cold processing to ensure dimensional accuracy. If the minimum distance between the tooth vertices on the inner surface of the intermediate product is too large, it may cause the inner mold teeth of the later pass to be misaligned with the teeth of the intermediate product. In the subsequent process of the variable diameter pipe, the inner teeth will be flattened, and it is impossible to achieve both internal teeth and variable diameter processing.

[0011] It is further characterized in that: the final tooth profile height of the inner wall of the seamless heat transfer tube is h, the final tooth top width is c1, and the bottom width is c2; the tooth height of each inner tooth of the first cold-processed toothed intermediate product in step b is controlled to be 1.2~1.5h, and a single tooth forms a nearly trapezoidal shape with rounded chamfers, the tooth top width is controlled to be 0.5~0.8c1, and the bottom width is 0.5~0.8c2. The parameter setting of the first cold-processed toothed intermediate product can ensure that the inner mold during the second and third cold processing can be smoothly installed in the pipe for subsequent processing.

[0012] Furthermore: the wall thickness of the small diameter section is 0.4 to 0.95 times the wall thickness of the large diameter section.

[0013] Preferably, the second cold working in step c and the third cold working in step d adopt the same inner mold.

[0014] A combination of cold working methods: when the deformation in the third cold working process exceeds 30%, or the wall reduction in the third cold working process exceeds 0.5 mm, the three cold working processes are all cold rolling.

[0015] Another combination of cold working: when the deformation of the third cold working process does not exceed 30%, and the wall reduction of the third cold working process does not exceed 0.5mm, the first and second cold working processes are both cold rolling, and the third cold working process is cold drawing.

[0016] Preferably, the fins with a spiral structure can be processed on the outer surface of the large-diameter tube body by rolling or cutting to prepare a fin tube with an internal tooth structure.

[0017] The present invention has the following beneficial effects: The variable diameter seamless heat transfer tube with internal tooth structure prepared by the method of the present invention is manufactured by integrating the internal tooth groove structure and the outer diameter variable diameter structure on a pipe material. The product has high dimensional accuracy, special inner surface structure, smooth outer diameter change and transition, and excellent pipe body straightness, and can simultaneously realize the functions of heat transfer and providing medium flow channel. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the structure of a high-precision variable-diameter seamless heat transfer tube with an internal tooth structure.

[0019] Figure 2 It is a cross-sectional view of the tooth groove structure.

[0020] Figure 3 It is a forming principle diagram of embodiment 1.

[0021] Figure 4 It is a structural schematic diagram of an internal tooth structure fin tube.

[0022] In the figure, 1-toothed groove, 2-small diameter section, 3-transition section, 4-large diameter section, 40-fin heat dissipation structure, 41-light pipe section, 42-heat dissipation section, 43-light pipe section at the tube end. DETAILED DESCRIPTION

[0023] The following is a further detailed description in conjunction with the embodiments of the present invention and the accompanying drawings. Embodiment 1

[0024] like Figure 1As shown, a high-precision variable diameter seamless heat transfer tube with an internal tooth structure includes a tooth-shaped groove 1 uniformly distributed longitudinally on the inner surface, and an outer surface divided into a small diameter section 2, a transition section 3 and a large diameter section 4 according to the size of the outer diameter; the small diameter section 2 and the large diameter section 4 are connected by the transition section 3; the specific dimensions are as follows: (1) The total length of the tube is 5150 mm; (2) The number of tooth grooves on the inner surface of the whole tube is 1: 20. Each tooth is 0.5 mm high, the width of the top of the tooth is about 0.3 mm, and the width of the bottom is 0.6 mm. A single tooth forms a nearly trapezoidal shape with rounded chamfers. The cross-sectional view of the tooth groove structure is as follows: Figure 2 As shown; (3) The outer diameter of the small diameter section 2 is Φ20 mm, the outer diameter deviation is ±0.05 mm, the wall thickness is 1 mm, and the length is 2500 mm;.

[0025] (4) The outer diameter of the large diameter section 4 is Φ22 mm, the wall thickness is 2 mm, and the length is 2500 mm; (5) The difference in wall thickness between the large diameter section 4 and the small diameter section 2 is 1 mm; (6) The transition section 3 tube body is 150 mm long, with a toothed structure inside that is consistent with the small diameter section and the large diameter section, and an inclined structure outside.

[0026] like Figure 3 As shown, a method for manufacturing a high-precision variable-diameter seamless heat transfer tube with an internal tooth structure includes the following steps: a. Choose appropriate Φ130mm round steel for perforation, and then make Φ38mm×3mm high-precision heat transfer tube intermediate product through multiple cold rolling deformation and heat treatment.

[0027] b. The intermediate product is subjected to the first cold working. After cold rolling, the outer diameter is Φ24mm and the nominal wall thickness is 2.5mm. At the same time, the internal tooth structure of the entire pipe is formed. The size of each internal tooth is 0.6mm in height. A single tooth forms a nearly trapezoidal shape with rounded chamfers. The width of the top of the tooth is about 0.2mm and the width of the bottom is 0.4mm. The tooth shape is slightly higher and narrower than the final tooth shape, thus obtaining a toothed intermediate product.

[0028] c. Perform a second cold working on one end of the toothed intermediate product to reduce the diameter and wall. The diameter reduction is 24-20=4mm, and the wall reduction is 2.5-1=1.5mm. At this time, the inner die tooth profile structure has a final tooth profile size of 0.5mm tooth height, about 0.3mm tooth top width, and 0.6mm bottom width. At the same time, a small diameter section with an outer diameter of Φ20mm and a nominal wall thickness of 1mm is obtained. The second cold rolling stops at 2500mm, leaving a cone as a transition section.

[0029] d. The other end of the toothed intermediate product is subjected to a third cold working from the point where the cold working of the small diameter section stops, so as to reduce the diameter and wall. The diameter reduction is 24-22=2mm, and the wall reduction is 2.5-2=0.5mm. At this time, the inner die is consistent with the inner die size of the second cold working, and the tooth profile structure is the final tooth profile size, so as to obtain a large diameter section with an outer diameter of Φ22mm and a nominal wall thickness of 2mm. The third cold rolling can be rolled over 2500mm, ensuring that the length of the pipe meets the final size requirements while leaving a length margin for subsequent processing at the end.

[0030] In the above manufacturing method, the tooth shape of the intermediate product is specially designed so that the minimum distance between the tooth vertices on the inner surface of the intermediate product is 17.8mm, which is just smaller than the maximum diameter value of the inner die of 18mm during the second and third cold working (the inner diameter and tooth height of the intermediate product are designed so that the minimum distance between the tooth vertices on the inner surface of the intermediate product is 10%~15% smaller than the maximum diameter value of the inner die during the second and third cold working), ensuring that the inner teeth of the intermediate product can be aligned with the inner die during the second and third cold working to ensure dimensional accuracy. At the same time, the width of the top and bottom of the teeth of the intermediate product is slightly narrower (designed to be 0.5~0.8 times the final size), and the nominal inner diameter is 19mm, which is larger than the maximum diameter value of the inner die of 18mm (ensuring that the gap between the inner diameter of the feed material and the inner die of the subsequent pass is reserved for more than 0.5mm), so that the inner die during the second and third cold working can be smoothly loaded into the pipe for subsequent processing.

[0031] After the second cold working, due to the large diameter and wall reduction of the small diameter section, the outer diameter of the pipe is smaller than the inner diameter of the outer die of the third cold working, and the material can be smoothly loaded and continued to be processed.

[0032] The second and third cold working can be done in one line or in two stages. The inner die size remains the same, so the tooth structure of the inner surface of the tube after final processing can be ensured to be consistent. The third cold working can be done by cold rolling or cold drawing. When cold drawing is selected, the size of the cold drawing inner die is consistent with the size structure of the cold rolling inner die.

[0033] During the second and third cold working, the diameter reduction and wall reduction can be performed once or in multiple times, and the amount of each diameter reduction and wall reduction can be adjusted until the diameter reduction and wall reduction meet the design requirements. This is easy to understand for those skilled in the art. Embodiment 2

[0034] The variable diameter seamless heat transfer tube prepared in Example 1 is further processed to produce a finned tube with an internal tooth structure.

[0035] like Figure 4As shown, a fin tube with an internal tooth structure includes tooth-shaped grooves 1 uniformly distributed longitudinally on the inner surface, and the outer surface is divided into a small diameter section 2, a transition section 3 and a large diameter section 4 according to the size of the outer diameter. The small diameter section 2 is connected to the large diameter section 4 through the transition section 3; the large diameter section 4 includes a light tube section 41 connected to the transition section 3, a heat dissipation section 42 provided with a fin heat dissipation structure 40, and a tube end light tube section 43.

[0036] The fin heat dissipation structure 40 is a spiral structure on the outer surface of the heat dissipation section 42 and is an integral spiral structure with the heat dissipation section 42 . The pitch is 1 mm and the thickness of the fin is 0.3 times the pitch.

[0037] The specific dimensions of a fin tube with an internal tooth structure are as follows: (1) The total length of the tube is 5150 mm; (2) The inner surface of the whole tube is evenly distributed with tooth-shaped grooves 1, which are 20 longitudinal groove teeth. Each tooth is 0.5 mm high, the top width of the tooth is about 0.3 mm, and the bottom width is 0.6 mm. A single tooth forms a nearly trapezoidal shape with rounded chamfers. The cross-sectional diagram of the tooth groove structure is shown in the figure. Figure 2 As shown; (3) The outer diameter of the small diameter section 2 is Φ20 mm, the outer diameter deviation is ±0.05 mm, the wall thickness is 1 mm, and the length is 2500 mm; (4) The outer diameter of the large diameter section 4 is Φ22 mm, the wall thickness is 2 mm, and the length is 2500 mm; (4) The difference in wall thickness between the large diameter section 4 and the small diameter section 2 is 1 mm; (6) The transition section 3 tube body is 150 mm long, with a toothed structure inside that is consistent with the small diameter section and the large diameter section, and an inclined surface structure outside; (7) The light pipe section 41 connected to the transition section 3 has an outer diameter of Φ22 mm and a length of 200 mm; (8) heat dissipation section 42, length 2000 mm; (9) The other end of the light tube section 43 has an outer diameter of Φ22 mm and a length of 300 mm; (10) After processing, the height of the fin 40 is ≥1.0 mm, and the remaining thickness is ≥1.0 mm.

[0038] The preparation method of the above-mentioned fin tube with internal tooth structure is as follows: S1, the product prepared by using Example 1; S2. A spiral structure is machined on the outer surface of the large-diameter heat dissipation section by rolling or cutting, with a pitch of 1 mm and a fin thickness of 0.3 times the pitch. The two ends of the large-diameter section outer surface where the spiral structure is not machined, i.e., the light pipe 41 connected to the transition section 3 and the other end light pipe section 43, retain a light pipe structure with an outer diameter of Φ22 mm.

[0039] S3. Heat-treat the tube body at a temperature of 1020°C for 10 minutes; after the heat-treating, cool the tube body to below 100°C at a cooling rate of ≥150°C / min; and obtain the product.

Claims

1. A method for manufacturing a high-precision variable-diameter seamless heat transfer tube with an internal tooth structure, wherein the inner wall of the seamless heat transfer tube has a longitudinal toothed groove, and the outer diameter includes a small diameter section and a large diameter section connected in one piece; characterized in that The following steps are involved: a. Process the tube blank to obtain a high-precision heat transfer tube intermediate product; b. Use the toothed inner die to perform the first cold working on the intermediate product, so that the internal tooth structure of the entire pipe is formed; the tooth shape is slightly higher and narrower than the final tooth shape, and a toothed intermediate product is obtained; c. Perform a second cold working on one end of the toothed intermediate product to reduce the diameter and wall; the wall reduction amount is S1, at which point the inner die tooth profile structure is the final tooth profile size, and a small diameter section is obtained; d. The other end of the toothed intermediate product is subjected to a third cold working from the point where the cold working of the small diameter section stops, so as to reduce the diameter and wall. The wall reduction amount is S2, S2<S1. At this time, the inner die tooth profile structure is the final tooth profile size, and the large diameter section is obtained.

2. The method for manufacturing a high-precision seamless heat transfer tube with internal teeth structure as claimed in claim 1, characterized in that: The final tooth profile height of the inner wall of the seamless heat transfer tube is h, the final tooth top width is c1, and the bottom width is c2; the tooth height of each inner tooth of the toothed intermediate product subjected to the first cold working in step b is controlled to be 1.2-1.5h, a single tooth is formed into a nearly trapezoidal shape, the chamfer is rounded, the tooth top width is controlled to be 0.5-0.8c1, and the bottom width is 0.5-0.8c2.

3. The method for manufacturing a high-precision seamless heat transfer tube with internal teeth structure as claimed in claim 2, characterized in that: The wall thickness of the small diameter section is 0.4 to 0.95 times the wall thickness of the large diameter section.

4. A method for manufacturing a high-precision variable-diameter seamless heat transfer tube with an internal tooth structure as claimed in any one of claims 1 to 3, characterized in that: The second cold working in step c and the third cold working in step d adopt the same inner mold.

5. The method for manufacturing a high-precision variable-diameter seamless heat transfer tube with an internal tooth structure according to any one of claims 1 to 3, characterized in that: The three cold working processes are all cold rolling.

6. A method for manufacturing a high-precision variable-diameter seamless heat transfer tube with an internal tooth structure as claimed in any one of claims 1 to 3, characterized in that: The first and second cold working processes are cold rolling, and the third cold working process is cold drawing.

7. A method for manufacturing a high-precision variable-diameter seamless heat transfer tube with an internal tooth structure as claimed in any one of claims 1 to 3, characterized in that: The spirally structured fins are processed on the outer surface of the large-diameter tube body by rolling or cutting to prepare a fin tube with an internal tooth structure.

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