A method for preparing an irregularly shaped externally grooved cross-shaped copper tube

Abstract

This invention discloses a method for preparing a non-grooved cross-shaped copper tube, comprising: Step S1: casting, rolling, and drawing copper molten metal into a tube blank; Step S2: flattening the tube head of the tube blank, inserting a floating mandrel into the flattened portion of the tube blank, and then shaping the flattened portion of the tube blank to limit the floating mandrel to the shaped portion of the tube blank; Step S3: passing the shaped portion of the tube blank sequentially through a pre-elliptical module and a cross-grooved module to prepare a cross-shaped copper tube. When the tube blank passes through the pre-elliptical module, it is drawn in the air to form an elliptical copper tube. When the elliptical copper tube passes through the cross-grooved module, it is stretched and uses the floating mandrel. The inner wall of the cross-grooved module has several protruding teeth. After stretching, a cross-shaped copper tube is formed, and several grooves are formed on the outer wall of the cross-shaped copper tube. This invention provides a method for preparing a non-grooved cross-shaped copper tube and enables continuous operation, significantly improving the yield, shortening the processing time, and increasing the degree of production automation.

Description

Technical Field

[0001] This invention relates to the technical field of irregular tube processing, and in particular to a method for preparing an irregular external grooved cross copper tube. Background Technology

[0002] Shaped copper tubes are seamless copper tubes with an appearance different from the conventional round shape, designed to meet the heat exchange requirements of special fields. In the gas sanitary ware industry, various shapes of shaped tubes have been developed to improve heat transfer efficiency. Due to their unique shape compared to round tubes, their manufacturing process also differs somewhat from that of conventional round tubes.

[0003] The traditional process for drawing shaped tubes is as follows: horizontal continuous casting—milling and drawing—coil drawing—coil drawing billet straightening and sawing—heading each tube—making internal convex teeth or internal grooves on each shaped tube—drawing each shaped tube into a shape—deburring, cleaning inner and outer surfaces—packaging. This process has the following problems: 1. Because this process involves making teeth or grooves first, and then stretching and deforming the tube into a shaped material, it cannot produce shaped tubes with external convex teeth and external grooves. Making teeth or grooves first and then stretching and deforming will inevitably damage the tooth structure. 2. This process involves drawing each tube individually, resulting in low labor intensity and production efficiency. Furthermore, the waste at each head and tail increases, leading to a low yield. Also, because the drawing operation relies on a mandrel to fix the head and coordinate with the external mold, continuous production is limited by the length of the mandrel. Summary of the Invention

[0004] To address the aforementioned problems in existing special-shaped tube processing, this paper aims to provide a method for preparing special-shaped external grooved cross copper tubes, enabling continuous operation of external grooved cross copper tubes, significantly improving the yield, shortening processing time, and increasing the degree of production automation.

[0005] The specific technical solution is as follows:

[0006] A method for preparing an irregularly shaped externally grooved cross-shaped copper tube includes:

[0007] Step S1: Molten copper is melted, cast, rolled, and drawn into tube blanks.

[0008] Step S2: Flatten the tube end of the tube blank, insert the floating mandrel into the flattened part of the tube blank, and perform head-making treatment on the flattened part of the tube blank so that the floating mandrel is limited to the head-making part of the tube blank.

[0009] Step S3: The tube blank passes through the pre-elliptical module and the cross groove module in sequence to prepare a cross copper tube. When the tube blank passes through the pre-elliptical module, it is stretched to form an elliptical copper tube. When the elliptical copper tube passes through the cross groove module, it is stretched and used in conjunction with the floating mandrel. The inner wall of the cross groove module is provided with several protruding teeth. After stretching, the cross copper tube is formed, and several grooves are formed on the outer wall of the cross copper tube.

[0010] The above-mentioned method for preparing irregularly shaped external grooved cross copper tube, wherein step S2 includes:

[0011] Step S2.1: At least one recess is made on the side wall of the tube head of the tube blank;

[0012] Step S2.2: After the tube blank is flattened, lubricating oil is added to the flattened part of the tube blank, and the floating mandrel is inserted into the flattened part of the tube blank so that the floating mandrel is positioned in the recess.

[0013] Step S2.3: After the flattened part of the tube blank is headed, the floating mandrel is positioned between the recess and the headed part of the tube blank.

[0014] In the above-mentioned method for preparing the irregular external groove cross copper tube, in step S3, the pre-elliptical module has a first guide cavity and a first forming cavity that are interconnected. The first guide cavity is a first cone shape, the first forming cavity is elliptical, the end of the first guide cavity near the first forming cavity is elliptical, and the end of the first guide cavity away from the first forming cavity is circular.

[0015] In step S3, the cross groove module has a second guide cavity and a second forming cavity that are interconnected. The second guide cavity is in the shape of a second cone, and the second forming cavity is in the shape of a cross. The end of the second guide cavity near the second forming cavity is in the shape of a cross, and the end of the second guide cavity away from the second forming cavity is in the shape of an ellipse. A plurality of protruding teeth are provided on the inner wall of the second forming cavity.

[0016] In step S3, the tube blank is sequentially drawn through the first guide cavity and the first forming cavity to form the elliptical copper tube;

[0017] In step S3, the elliptical copper tube passes through the second guide cavity and the second forming cavity in sequence, and the floating core head passes through the second guide cavity and the second forming cavity, forming the cross copper tube with the groove on the outer wall after stretching.

[0018] In the above-mentioned method for preparing the irregular external grooved cross copper tube, the first guide cavity, the first forming cavity, the second guide cavity, and the second forming cavity are coaxially arranged.

[0019] The long axis of the first guide cavity is directly opposite to the long axis of the first molding cavity, the long axis of the first molding cavity is directly opposite to the long axis of the second guide cavity, and the long axis of the second guide cavity is directly opposite to the long axis of the second molding cavity.

[0020] The above-mentioned method for preparing a non-grooved cross copper tube, wherein in step S3, the pre-elliptical module includes: a first outer mold and an elliptical inner mold, the elliptical inner mold being installed inside the first outer mold, and the elliptical inner mold having the first guide cavity and the first forming cavity;

[0021] In step S3, the cross groove module includes a second outer mold and a cross groove inner mold. The cross groove inner mold is installed inside the second outer mold, and the cross groove inner mold has a second guide cavity and a second forming cavity.

[0022] In the above-mentioned method for preparing the irregular external grooved cross copper tube, in step S3, the moving core head includes a support part, a guide part, and an extrusion part connected in sequence. The support part is elliptical, the guide part is a third cone, the extrusion part is cross-shaped, the end of the guide part near the extrusion part is cross-shaped, the end of the guide part near the support part is elliptical, the guide part cooperates with the second guide cavity, and the extrusion part cooperates with the second forming cavity.

[0023] In the above-mentioned method for preparing the irregular external grooved cross copper tube, the major axis cone angle β1 of the second guide cavity is 20° to 36°, the minor axis cone angle γ1 of the second guide cavity is 20° to 36°, the major axis cone angle β2 of the guide portion is 20° to 36°, the minor axis cone angle γ2 of the guide portion is 20° to 36°, the major axis cone angle β2 of the guide portion is 2 to 4° smaller than the major axis cone angle β1 of the second guide cavity, and the minor axis cone angle γ2 of the guide portion is 2 to 3° smaller than the minor axis cone angle γ1 of the second guide cavity;

[0024] The major axis dimension D1 of the second molding cavity is 10-28mm, the minor axis dimension d1 of the second molding cavity is 10-25mm, and the thickness dimension H1 of the second molding cavity is 3-6mm.

[0025] The major axis cone angle β of the first guide cavity is 20°~35°, the minor axis cone angle γ of the first guide cavity is 18°~35°, the major axis dimension D of the first forming cavity is 10~30mm, the minor axis dimension d of the first forming cavity is 10~25mm, and the thickness dimension H0 of the first forming cavity is 3~8mm.

[0026] The major axis dimension D2 of the support part is 10-28mm, the minor axis dimension d2 of the support part is 8-23mm, the major axis dimension D3 of the extrusion part is 8-25mm, and the minor axis dimension d3 of the extrusion part is 5-20mm;

[0027] The number of protruding teeth is 30 to 80, the tooth height H of the protruding teeth is 0.01 to 0.20 mm, and the tooth tip angle α of the protruding teeth is 10 to 60°.

[0028] In the above-mentioned method for preparing the irregular external grooved cross copper tube, the major axis D of the first forming cavity and the major axis D1 of the second forming cavity have a first reduction rate, the first reduction rate being 12-18%, and the minor axis d of the first forming cavity and the minor axis d1 of the second forming cavity have a second reduction rate, the second reduction rate being 12-18%, and the second reduction rate being 2% smaller than the first reduction rate.

[0029] In the above-mentioned method for preparing irregularly shaped external grooved cross copper tubes, the processing rate of the tube blank processed by the pre-elliptical module is 15-25%; the processing rate of the elliptical copper tube processed by the cross groove module is 10-20%.

[0030] The above-mentioned method for preparing a non-grooved cross-shaped copper tube, wherein the inner wall of the second forming cavity has two first long-axis U-shaped walls and two first short-axis U-shaped walls spaced apart, and the first long-axis U-shaped walls and the first short-axis U-shaped walls are transitioned by a first arc-shaped wall;

[0031] The outer wall of the extrusion section has two second long axis U-shaped walls and two second short axis U-shaped walls spaced apart, and the second long axis U-shaped walls and the second short axis U-shaped walls are transitioned by a second arc-shaped wall;

[0032] The difference between the radius R1 of the first arc-shaped wall and the radius R2 of the second arc-shaped wall is used to set the wall thickness of the cross-shaped copper tube;

[0033] Several of the aforementioned protruding teeth are respectively disposed on the two first long axis U-shaped walls, the two first short axis U-shaped walls, and the four first arc-shaped walls;

[0034] The plurality of protruding teeth include: a plurality of first protruding teeth and a plurality of second protruding teeth, wherein the plurality of first protruding teeth are disposed on two first long axis U-shaped walls and two first short axis U-shaped walls, and the plurality of second protruding teeth are disposed on four first arc-shaped walls. The plurality of first protruding teeth on the first long axis U-shaped walls are arranged at equal intervals, the plurality of first protruding teeth on the first short axis U-shaped walls are arranged at equal intervals, and the plurality of second protruding teeth on the first arc-shaped walls are arranged at equal intervals.

[0035] The bottom of the first short-axis U-shaped wall has a short-axis arc-shaped wall, and the bottom of the first long-axis U-shaped wall has a long-axis arc-shaped wall. The radius R3 of the short-axis arc-shaped wall is 10 to 25% larger than the radius R4 of the long-axis arc-shaped wall.

[0036] The positive effects of the above technical solution compared with the existing technology are:

[0037] This invention creates several grooves on the outer wall of a cross-shaped copper tube, increasing the outer surface area of ​​the copper tube and enhancing its heat transfer capacity. Compared with ordinary smooth cross-shaped tubes, the heat transfer coefficient is increased by more than 8%. The number of teeth on the outer surface of the copper tube cross section is 30 to 80, the tooth tip angle is 10 to 60°, the tooth height is 0.01 to 0.20 mm, the outer diameter of the long axis of the cross is 10 to 28 mm, the outer diameter of the short axis is 10 to 25 mm, and the wall thickness is 0.5 to 2.0 mm.

[0038] This invention produces external grooved cross-shaped copper tubes through a one-time machining process of tooth making and cross deformation, and achieves continuous operation, which greatly improves the yield, shortens the processing time, and increases the degree of production automation. Attached Figure Description

[0039] Figure 1 This is a schematic diagram of the stretching process of a method for preparing a non-grooved cross copper tube according to the present invention.

[0040] Figure 2 This invention relates to a method for preparing a non-grooved cross-shaped copper tube. Figure 1 A-direction diagram in the diagram;

[0041] Figure 3 This invention relates to a method for preparing a non-grooved cross-shaped copper tube. Figure 1 Enlarged view at point B in the middle;

[0042] Figure 4 This invention relates to a method for preparing a non-grooved cross-shaped copper tube. Figure 1 Enlarged view at point C;

[0043] Figure 5 This is a cross-sectional view along the major axis of the pre-elliptical module in the method for preparing a non-grooved cross copper tube according to the present invention.

[0044] Figure 6 This is a cross-sectional view along the minor axis of the pre-elliptical module of the method for preparing an irregularly shaped external grooved cross copper tube according to the present invention.

[0045] Figure 7 This is an axial schematic diagram of the pre-elliptical module in the method for preparing a non-grooved cross copper tube according to the present invention.

[0046] Figure 8This is a cross-sectional view along the long axis of the cross-grooved module of the method for preparing an irregularly shaped external grooved cross copper tube according to the present invention.

[0047] Figure 9 This is a cross-sectional view along the short axis of a cross-grooved module in the method for preparing an irregularly shaped external grooved cross copper tube according to the present invention.

[0048] Figure 10 This is an axial schematic diagram of the cross-groove module in the method for preparing a non-standard external grooved cross copper tube according to the present invention.

[0049] Figure 11 This invention relates to a method for preparing a non-grooved cross-shaped copper tube. Figure 9 Enlarged view at point D;

[0050] Figure 12 This is a side view along the long axis of the moving core of the method for preparing a non-grooved cross copper tube according to the present invention.

[0051] Figure 13 This is a side view of the moving core in the short axis direction of a method for preparing an irregularly shaped external grooved cross copper tube according to the present invention.

[0052] Figure 14 This is an axial schematic diagram of the moving core of the method for preparing a non-grooved cross copper tube according to the present invention.

[0053] Figure 15 This is a schematic diagram of the cross-shaped copper tube used in the preparation method of the irregular external groove cross-shaped copper tube of the present invention.

[0054] Figure 16 This invention relates to a method for preparing a non-grooved cross-shaped copper tube. Figure 15 Enlarged view at point E in the middle;

[0055] Figure 17 This is a schematic diagram of the tube blank after the indentation is made, which is a method for preparing a non-grooved cross copper tube according to the present invention.

[0056] Figure 18 This is a schematic diagram of the tube blank after vertical flattening in the preparation method of the irregular external groove cross copper tube of the present invention;

[0057] Figure 19 This is a schematic diagram of the tube blank after the tube head is formed, according to the method for preparing a non-grooved cross copper tube of the present invention.

[0058] Figure 20 This is a schematic diagram of the moving core of the method for preparing a non-grooved cross copper tube according to the present invention;

[0059] Figure 21 This is a schematic diagram of the cross-groove module in the method for preparing a non-standard external grooved cross copper tube according to the present invention.

[0060] In the attached diagram: 1. Pre-elliptical module; 2. Cross-grooved module; 3. Floating core head; 4. Tube blank; 5. Elliptical copper tube; 6. Cross-shaped copper tube; 7. Convex tooth; 8. Groove;

[0061] 11. First guide cavity; 12. First forming cavity; 13. First outer mold; 14. Pre-elliptical inner mold;

[0062] 21. Second guide cavity; 22. Second forming cavity; 23. Second outer mold; 24. Cross groove inner mold;

[0063] 31. Support section; 32. Guide section; 33. Extrusion section;

[0064] 41. First long axis U-shaped wall; 42. First short axis U-shaped wall; 43. First arc-shaped wall; 411. Long axis arc-shaped wall; 421. Short axis arc-shaped wall;

[0065] 51. Second long axis U-shaped wall; 52. Second short axis U-shaped wall; 53. Second arc-shaped wall;

[0066] 61. First U-shaped segment; 62. Second U-shaped segment; 63. Circular arc segment;

[0067] 71. First convex tooth; 72. Second convex tooth;

[0068] 81. First trench; 82. Second trench;

[0069] 91. Dent; 92. Flattened area; 93. Heading area. Detailed Implementation

[0070] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but this is not intended to limit the scope of the invention.

[0071] Figure 1 This is a schematic diagram of the stretching process of a method for preparing a non-grooved cross copper tube according to the present invention.

[0072] Figure 2 This invention relates to a method for preparing a non-grooved cross-shaped copper tube. Figure 1 A-direction diagram in the diagram;

[0073] Figure 3 This invention relates to a method for preparing a non-grooved cross-shaped copper tube. Figure 1 Enlarged view at point B in the middle;

[0074] Figure 4 This invention relates to a method for preparing a non-grooved cross-shaped copper tube. Figure 1 Enlarged view at point C;

[0075] Figure 5This is a cross-sectional view along the major axis of the pre-elliptical module in the method for preparing a non-grooved cross copper tube according to the present invention.

[0076] Figure 6 This is a cross-sectional view along the minor axis of the pre-elliptical module of the method for preparing an irregularly shaped external grooved cross copper tube according to the present invention.

[0077] Figure 7 This is an axial schematic diagram of the pre-elliptical module in the method for preparing a non-grooved cross copper tube according to the present invention.

[0078] Figure 8 This is a cross-sectional view along the long axis of the cross-grooved module of the method for preparing an irregularly shaped external grooved cross copper tube according to the present invention.

[0079] Figure 9 This is a cross-sectional view along the short axis of a cross-grooved module in the method for preparing an irregularly shaped external grooved cross copper tube according to the present invention.

[0080] Figure 10 This is an axial schematic diagram of the cross-groove module in the method for preparing a non-standard external grooved cross copper tube according to the present invention.

[0081] Figure 11 This invention relates to a method for preparing a non-grooved cross-shaped copper tube. Figure 9 Enlarged view at point D;

[0082] Figure 12 This is a side view along the long axis of the moving core of the method for preparing a non-grooved cross copper tube according to the present invention.

[0083] Figure 13 This is a side view of the moving core in the short axis direction of a method for preparing an irregularly shaped external grooved cross copper tube according to the present invention.

[0084] Figure 14 This is an axial schematic diagram of the moving core of the method for preparing a non-grooved cross copper tube according to the present invention.

[0085] Figure 15 This is a schematic diagram of the cross-shaped copper tube used in the preparation method of the irregular external groove cross-shaped copper tube of the present invention.

[0086] Figure 16 This invention relates to a method for preparing a non-grooved cross-shaped copper tube. Figure 15 Enlarged view at point E in the middle;

[0087] Figure 17 This is a schematic diagram of the tube blank after the indentation is made, which is a method for preparing a non-grooved cross copper tube according to the present invention.

[0088] Figure 18 This is a schematic diagram of the tube blank after vertical flattening in the preparation method of the irregular external groove cross copper tube of the present invention;

[0089] Figure 19 This is a schematic diagram of the tube blank after the tube head is formed, according to the method for preparing a non-grooved cross copper tube of the present invention.

[0090] Figure 20 This is a schematic diagram of the moving core of the method for preparing a non-grooved cross copper tube according to the present invention;

[0091] Figure 21 This is a schematic diagram of the cross-groove module in the method for preparing a non-standard external grooved cross copper tube according to the present invention.

[0092] like Figures 1 to 21 The diagram illustrates a preferred embodiment of a method for preparing a non-grooved cross-shaped copper tube, comprising:

[0093] Step S1: The molten copper is melted, cast, rolled, and drawn into tube blanks 4:

[0094] Step S2: Flatten the tube end of the tube blank 4, insert the floating mandrel 3 into the flattened part of the tube blank 4, and perform head-making treatment on the flattened part 92 of the tube blank 4 so that the floating mandrel 3 is limited to the head-making part 93 of the tube blank 4.

[0095] Step S3: The tube blank 4 passes through the pre-elliptical module 1 and the cross groove module 2 in sequence to prepare the cross copper tube 6. When the tube blank 4 passes through the pre-elliptical module 1, it is stretched to form an elliptical copper tube 5. When the elliptical copper tube 5 passes through the cross groove module 2, it is stretched and used in conjunction with the floating mandrel 3. The inner wall of the cross groove module 2 is provided with several protruding teeth 7. After stretching, the cross copper tube 6 is formed, and several grooves 8 are formed on the outer wall of the cross copper tube 6.

[0096] Furthermore, in a preferred embodiment, step S2 includes:

[0097] Step S2.1: Make at least one recess 91 on the side wall of the tube head of the tube blank 4;

[0098] Step S2.2: After the tube head of the tube blank 4 is flattened, lubricating oil is added through the flattened part 92 of the tube blank 4, and the floating mandrel 3 is inserted through the flattened part 92 of the tube blank 4 so that the floating mandrel 3 is limited to the recess 91.

[0099] Step S2.3: After the flattened portion 92 of the tube blank 4 is headed, the floating mandrel 3 is positioned between the recess 91 and the headed portion 93 of the tube blank 4.

[0100] Preferably, in step S1, molten copper is continuously cast into a horizontal continuous casting tube blank by a traction rod. The horizontal continuous casting tube blank has an outer diameter of φ92mm and a wall thickness of 25mm. The horizontal continuous casting tube blank is rolled into a soft rolled tube blank with an outer diameter of φ35~55mm and a wall thickness of 2.5~4.0mm by a rolling mill. The soft rolled tube blank is then drawn into a hard tube blank with an outer diameter of φ10~30mm and a wall thickness of 0.5~2.0mm.

[0101] Preferably, in step S2, at least one recess 91 is made at a distance of 300mm from the side wall of the tube head of the tube blank 4, a floating mandrel 3 is placed inside the tube head of the tube blank 4, 220ml of "KN-140" type inner film oil is added, the end of the tube head of the tube blank 4 is vertically flattened at a distance of 200-280mm, and a head-making operation is performed on the flattened part 92, and the floating mandrel 3 is limited to the recess 91 and the head-making part 93 of the tube blank 4.

[0102] Furthermore, as a preferred embodiment, in step S3, the pre-elliptical module 1 has a first guide cavity 11 and a first molding cavity 12 that are interconnected. The first guide cavity 11 is a first cone shape, and the first molding cavity 12 is an ellipse shape. The end of the first guide cavity 11 near the first molding cavity 12 is elliptical, and the end of the first guide cavity 11 away from the first molding cavity 12 is circular.

[0103] Furthermore, as a preferred embodiment, in step S3, the cross groove module has a second guide cavity 21 and a second forming cavity 22 that are interconnected. The second guide cavity 21 is in the shape of a second cone, and the second forming cavity 22 is in the shape of a cross. The end of the second guide cavity 21 near the second forming cavity 22 is in the shape of a cross, and the end of the second guide cavity 21 away from the second forming cavity 22 is in the shape of an ellipse. Several protruding teeth 7 are provided on the inner wall of the second forming cavity 22.

[0104] Furthermore, as a preferred embodiment, in step S3, the tube blank 4 is sequentially drawn through the first guide cavity 11 and the first forming cavity 12 to form an elliptical copper tube 5.

[0105] Furthermore, as a preferred embodiment, in step S3, the elliptical copper tube 5 passes through the second guide cavity 21 and the second forming cavity 22 in sequence, and the floating core head 3 passes through the second guide cavity 21 and the second forming cavity 22, and after stretching, forms a cross copper tube 6 with grooves 8 on the outer wall.

[0106] Furthermore, in a preferred embodiment, the first guide cavity 11, the first molding cavity 12, the second guide cavity 21, and the second molding cavity 22 are coaxially arranged.

[0107] Furthermore, in a preferred embodiment, the long axis of the first guide cavity 11 is directly opposite to the long axis of the first molding cavity 12, the long axis of the first molding cavity 12 is directly opposite to the long axis of the second guide cavity 21, and the long axis of the second guide cavity 21 is directly opposite to the long axis of the second molding cavity 22.

[0108] The above are merely preferred embodiments of the present invention and are not intended to limit the implementation methods and protection scope of the present invention.

[0109] In addition to the above, the present invention also has the following embodiments:

[0110] In further embodiments of the present invention, please continue to refer to Figures 1 to 21 As shown, in step S3, the pre-elliptical module 1 includes: a first outer mold 13 and an elliptical inner mold 14. The elliptical inner mold 14 is installed inside the first outer mold 13, and the elliptical inner mold 14 has a first guide cavity 11 and a first forming cavity 12.

[0111] In a further embodiment of the present invention, in step S3, the cross groove module 2 includes: a second outer mold 23 and a cross groove inner mold 24, the cross groove inner mold 25 is installed inside the second outer mold 23, and the cross groove inner mold 24 has a second guide cavity 21 and a second forming cavity 22.

[0112] In a further embodiment of the present invention, in step S3, the floating core head 3 includes a support portion 31, a guide portion 32, and a pressing portion 33 connected in sequence. The support portion 31 is elliptical, the guide portion 32 is a third cone, and the pressing portion 33 is cross-shaped. The end of the guide portion 32 near the pressing portion 33 is cross-shaped, and the end of the guide portion 32 near the support portion 31 is elliptical. The guide portion 32 cooperates with the second guide cavity 21, and the pressing portion 33 cooperates with the second forming cavity 22.

[0113] In a further embodiment of the present invention, the major axis dimension D2 of the support portion 31 of the floating mandrel 3 is smaller than the major axis dimension D of the pre-elliptical outer mold, and the major axis dimension D2 of the support portion 31 of the floating mandrel 3 is ≤ the major axis dimension of the first forming cavity 12 - the wall thickness of the tube blank 4 * 2 - the allowance (0.20~0.30mm), the minor axis dimension d2 of the support portion 31 of the floating mandrel 3 is smaller than the minor axis dimension d of the first forming cavity 12, and the minor axis dimension d3 of the extrusion portion 33 is ≤ the minor axis dimension d of the first forming cavity 12 - the wall thickness of the tube blank 4 * 2 - the allowance (0.20~0.30mm). During the stretching process, the cross-shaped floating mandrel is ensured to pass smoothly through the pre-elliptical outer mold and cooperate with the cross-groove inner mold for stretching and forming.

[0114] In a further embodiment of the present invention, the major axis cone angle β1 of the second guide cavity 21 is 20° to 36°, the minor axis cone angle γ1 of the second guide cavity 21 is 20° to 36°, the major axis cone angle β2 of the guide portion 32 is 20° to 36°, the minor axis cone angle γ2 of the guide portion 32 is 20° to 36°, the major axis cone angle β2 of the guide portion 32 is 2 to 4° smaller than the major axis cone angle β1 of the second guide cavity 21, and the minor axis cone angle γ2 of the guide portion 32 is 2 to 3° smaller than the minor axis cone angle γ1 of the second guide cavity 21. With the cone angle of the guide portion 32 being smaller than that of the second guide cavity 21, during stretching and forming, the floating mandrel 3 is stretched and moves forward. The inner wall of the copper tube and the guide portion 32 of the floating mandrel 3, and the outer wall of the copper tube and the second guide cavity 21 respectively form a micro-space. Lubricating oil can be stored in this space, so that the copper tube is fully lubricated during deformation, and the deformation of the tube is smooth. The angle difference between the cone angle of the guide section 32 and the cone angle of the second guide cavity 21 is less than the range value, and the axial adjustment capability of the floating mandrel 3 is limited. Once the floating mandrel 3 becomes unstable, it is easy to find that the tube is cut off at the cone angle by the cross groove inner mold 24 and the floating mandrel 3. The angle difference between the cone angle of the guide section 32 and the cone angle of the second guide cavity 21 is greater than the range value, and the copper tube wall thickness cannot meet the requirements.

[0115] Preferably, the major axis dimension D1 of the second molding cavity 22 is 10-28 mm, the minor axis dimension d1 of the second molding cavity 22 is 10-25 mm, and the thickness dimension H1 of the second molding cavity 22 is 3-6 mm.

[0116] Preferably, the major axis cone angle β of the first guide cavity 11 is 20°~35°, the minor axis cone angle γ of the first guide cavity 11 is 18°~35°, the major axis dimension D of the first forming cavity 12 is 10~30mm, the minor axis dimension d of the first forming cavity 12 is 10~25mm, and the thickness dimension H0 of the first forming cavity 12 is 3~8mm. This is controlled according to the size and ovality of the mother tube being drawn from the round tube to avoid surface scratches caused by the small feed opening of the mold during the empty drawing process.

[0117] Preferably, the major axis dimension D2 of the support part 31 is 10-28mm, the minor axis dimension d2 of the support part 31 is 8-23mm, the major axis dimension D3 of the extrusion part 33 is 8-25mm, and the minor axis dimension d3 of the extrusion part 33 is 5-20mm.

[0118] In a further embodiment of the present invention, there is a first reduction ratio between the long axis D of the first forming cavity 12 and the long axis D1 of the second forming cavity 22. The first reduction ratio is 12 to 18%. If the outer diameter reduction ratio is too small, it will lead to poor forming of the stretch forming teeth, that is, the tooth size is not qualified. If the outer diameter reduction ratio is too large, it will cause the tube to break during continuous stretching operation due to excessive stretching resistance.

[0119] In a further embodiment of the present invention, there is a second reduction rate between the minor axis d of the first forming cavity 12 and the minor axis d1 of the second forming cavity 22. The second reduction rate is 12-18%, which is 2% smaller than the first reduction rate. This can ensure that the copper tube wall thickness is uniform. If the reduction rate is not controlled within the range, uneven wall thickness will occur in different parts of the finished product.

[0120] In a further embodiment of the present invention, the processing rate of the tube blank 4 after processing by the pre-elliptical module 1 is 15-25%. If the processing rate is greater than 25%, the tube will have an increased wall thickness after pre-elliptical air stretching. The increased wall thickness will lead to an increased processing rate during the stretching cross forming process, resulting in tube breakage, interruption of processing, and the need to remake the head and pierce the mold, causing product scrap and other problems.

[0121] In a further embodiment of the present invention, the processing rate of the elliptical copper tube 5 after processing by the cross groove module 2 is 10-20%. Because the pre-elliptical empty drawing section and the cross groove forming section are drawn in series, the forming of its outer cross groove requires the support of the floating core head 3, resulting in a large stretching resistance. If the processing rate is greater than the range, it will lead to tube breakage and make continuous stretching impossible. If the processing rate is less than the range, it will lead to difficulty in stretching and forming teeth, unqualified tooth size, or even a smooth surface structure.

[0122] In a further embodiment of the present invention, the number of protruding teeth 7 is 30 to 80, the tooth height H of the protruding teeth 7 is 0.01 to 0.20 mm, and the strength of the pipe is guaranteed while ensuring the heat transfer efficiency of the pipe 4. The tooth tip angle α of the protruding teeth 7 is 10 to 60°.

[0123] In a further embodiment of the present invention, the inner wall of the second molding cavity 22 has two first long axis U-shaped walls 41 and two first short axis U-shaped walls 42 spaced apart, and the first long axis U-shaped walls 41 and the first short axis U-shaped walls 42 are connected by a first arc-shaped wall 43.

[0124] In a further embodiment of the present invention, the outer wall of the extrusion part 33 has two second long axis U-shaped walls 51 and two second short axis U-shaped walls 52 spaced apart, and the second long axis U-shaped walls 51 and the second short axis U-shaped walls 52 are transitioned by a second arc-shaped wall 53.

[0125] In a further embodiment of the present invention, the difference between the radius R1 of the first arc-shaped wall 43 and the radius R2 of the second arc-shaped wall 53 is used to set the wall thickness of the cross-shaped copper tube 6. This ensures that the wall thickness of the arc-shaped section and the wall thickness of the planar section of the outer groove cross-shaped copper tube 6 are consistent.

[0126] In a further embodiment of the present invention, a plurality of protruding teeth 7 are respectively disposed on two first long axis U-shaped walls 41, two first short axis U-shaped walls 42 and four first arc-shaped walls 43.

[0127] In a further embodiment of the present invention, the plurality of protruding teeth 7 includes: a plurality of first protruding teeth 71 and a plurality of second protruding teeth 72. The plurality of first protruding teeth 71 are disposed on two first long axis U-shaped walls 41 and two first short axis U-shaped walls 42, and the plurality of second protruding teeth 72 are disposed on four first arc-shaped walls 43. The plurality of first protruding teeth 71 on the first long axis U-shaped walls 41 are arranged at equal intervals, the plurality of first protruding teeth 72 on the first short axis U-shaped walls 42 are arranged at equal intervals, and the plurality of second protruding teeth 72 on the first arc-shaped walls 43 are arranged at equal intervals.

[0128] In a further embodiment of the present invention, the bottom of the first short-axis U-shaped wall 42 has a short-axis arc-shaped wall 421, and the bottom of the first long-axis U-shaped wall 41 has a long-axis arc-shaped wall 411. The radius R3 of the short-axis arc-shaped wall 421 is 10-25% larger than the radius R4 of the long-axis arc-shaped wall 411, so as to achieve a smooth transition and appropriately reduce the processing rate between the pre-ellipse and cross-forming. The tube is less likely to break during the stretching operation to ensure continuous stretching operation.

[0129] Preferably, the discharge port of the first forming cavity 12 has a cone angle of 60°, and the discharge port of the second forming cavity 22 has a cone angle of 60°.

[0130] The present invention forms several grooves 8 on the outer wall of the cross copper tube 6, thereby increasing the outer surface area of ​​the copper tube and enhancing the heat transfer capacity.

[0131] The finished product after processing according to the present invention is a cross-shaped copper tube 6 with grooves 8, and the cross-shaped copper tube 6 has a cross-shaped cross section.

[0132] The cross section of the cross-shaped copper tube 6 includes two first U-shaped segments 61 and two second U-shaped segments 62 that are spaced apart from each other, and the first U-shaped segments 61 and the second U-shaped segments 62 are respectively connected by arc segments 63.

[0133] Preferably, the wall thickness of the first U-shaped segment 61, the wall thickness of the second U-shaped segment 62, and the wall thickness of the arc segment 63 are the same.

[0134] Preferably, the outer walls of the first U-shaped segment 61, the second U-shaped segment 62, and the arc segment 63 are all provided with a plurality of grooves 8.

[0135] Preferably, the plurality of grooves 8 include a plurality of first grooves 81 and a plurality of second grooves 82. The plurality of first grooves 81 are respectively disposed on two first U-shaped segments 61 and two second U-shaped segments 62, and the plurality of second grooves 82 are respectively disposed on four circular arc segments 63. The plurality of first grooves 81 on each first U-shaped segment 61 are distributed at equal intervals, the plurality of first grooves 81 on each second U-shaped segment 62 are distributed at equal intervals, and the plurality of second grooves 82 on each circular arc segment 63 are disposed at equal intervals.

[0136] A first spacing is formed between two adjacent first grooves 81 on the first U-shaped segment 61, a second spacing is formed between two adjacent first grooves 81 on the second U-shaped segment 62, and a third spacing is formed between two adjacent second grooves 82 on the arc segment 63. The first spacing is equal to the second spacing, and the third spacing is greater than the first spacing.

[0137] This invention enables continuous operation of external grooved cross copper tubes, significantly improving the yield rate while shortening processing time and increasing the degree of production automation.

[0138] Example 1: Fabrication of a material with dimensions φ20.80(D1)*13.00(d1)*0.85(wall thickness)*0.11(H)*50(α)+70(number of protrusions)*6000(length)

[0139] Example 2: Fabrication of a material with dimensions φ24.80(D1)*14.90(d1)*0.90(wall thickness)*0.15(H)*45(α)+60(number of protrusions)*5800(length)

[0140] Example 3: Fabrication of a material with dimensions φ22.80(D1)*13.68(d1)*1.0(wall thickness)*0.145(H)*42(α)+55(number of protrusions)*6000(length)

[0141] The preparation method of the present invention includes the following steps:

[0142] A1: Melting and casting: The copper liquid is horizontally continuously cast into tube blanks. The detailed dimensions of the tube blanks are shown in Table 1.

[0143] A2: Milling: Remove oxide scale from the surface of the horizontal continuous casting billet, with a single-sided milling amount of 0.3 to 0.8 mm;

[0144] A3: Rolling: The milled tube blank is rolled by a rolling mill. The detailed dimensions of the rolled tube blank are shown in Table 1.

[0145] A4: Coil drawing: The rolled tube blank is continuously stretched multiple times on a coil drawing machine. The dimensions of the tube blank after coil drawing are shown in Table 1.

[0146] A5: Control Head:

[0147] Step 1: Make a recess 300mm from the end of the mother tube blank;

[0148] Step 2: Vertically flatten the tube blank at 200-280mm from the end, add 220ml of "KN-140" type inner film oil, and simultaneously insert the floating mandrel into the tube (see Table 5 for detailed dimensions of the floating mandrel), fixing it to the flattened end of the mother tube blank to prevent it from passing through.

[0149] Step 3: Perform head-making operation on the first 200mm of the mother tube blank until it is almost solid and can easily pass through the pre-elliptical module and cross groove module.

[0150] A6: Stretch forming: After the tube has been headed, it is passed sequentially through a pre-elliptical module (detailed dimensions in Table 3) and a cross-grooved module (detailed dimensions in Table 4) fixed on the machine base. Then, it is stretched and sawed by a clamp in a continuous cycle. This involves the processing rate of each stretching section (detailed parameters in Table 2) and the various dimensional parameters of the finished product after stretching (detailed parameters in Table 6).

[0151] Deburring: Deburring and blowing are performed on both ends of the copper tube after stretching and sawing.

[0152] Packaging: Packaging and warehousing according to customer requirements.

[0153] Table 1. Dimensions of semi-finished products at each stage of the embodiment.

[0154]

[0155] Table 2 Processing Rate Parameters of Examples

[0156] serial number Pan-pulling - Pre-elliptical segment Pre-elliptical segment - finished segment Finished product stretching speed Example 1 19.50％ 12.48％ 46m / min Example 2 20.65％ 14.46％ 46m / min Example 3 20.77％ 12.83％ 46m / min

[0157] Table 3 Parameters of the Preelliptic Module in the Embodiments

[0158]

[0159] Table 4 Parameters of the Cross Groove Module in the Embodiments

[0160]

[0161] Table 5. Cross-shaped spiral parameters in the embodiment.

[0162]

[0163] Table 6. Finished Product Dimensions (Unit: mm)

[0164] serial number outer diameter of major axis Short shaft outer diameter Wall thickness Tooth height Tooth tip angle Number of teeth length Example 1 20.80 13.00 0.84～0.87 0.11 53 70 6000 Example 2 24.80 14.90 0.88～0.93 0.15 45 60 5800 Example 3 22.80 13.68 0.98～1.01 0.145 42 55 6000

[0165] Table 7. Yield of materials in the examples

[0166]

[0167] Table 8. Time taken for each step in the embodiment.

[0168]

[0169]

[0170] Comparative example implementation details: (Currently, there is no stretch forming method for producing externally grooved profiled tubes)

[0171] Comparative Example 1: A comparison is made with the existing manufacturing method of straight pipes with diameters of φ39mm × 1.2mm × 6000mm (outer diameter × wall thickness × length). (This comparative example is a production method for stretching circular straight pipes one by one. The main drawback of this process is that it involves many processing steps and requires multiple stretching operations in the pipe-drawing process, making continuous operation impossible.)

[0172] B1: Melting and casting: The copper liquid is horizontally continuously cast into a tube blank with an outer diameter of 92mm and a wall thickness of 25mm;

[0173] B2: Milling: Remove oxide scale from the surface of the horizontally continuously cast tube blank, with a single-sided milling amount of 0.3–0.8 mm;

[0174] B3: Rolling: Rolling the milled casting billet into a tube blank with an outer diameter of 50mm and a wall thickness of 3.0mm;

[0175] B4: Sawing: Sawing the rolled tube blank into single tube blanks with a length of 2070mm;

[0176] B5: Head forming: Press one end of each sawn tube blank into a solid state with a length of 150mm to ensure that the head forming end can pass through the outer mold;

[0177] B6: Straight drawing: The tube blank after head making is subjected to the first straight tube drawing. The fixed mandrel is inserted into the tube blank, and the tube blank is drawn one by one to an outer diameter of φ46mm and a wall thickness of 2.1mm through the cooperation of the outer membrane and the fixed mandrel.

[0178] B7: Straight drawing: The tube blank is stretched a second time. The fixed mandrel is inserted into the φ46mm×2.1mm tube blank, and the tube blank is stretched one by one to an outer diameter of φ42mm and a wall thickness of 1.6mm through the cooperation of the outer membrane and the fixed mandrel.

[0179] B8: Straight drawing: The tube blank is stretched for the third time. The fixed mandrel is inserted into the φ42mm×1.6mm tube blank. Through the cooperation of the outer membrane and the fixed mandrel, the tube blanks are stretched one by one to an outer diameter of φ39mm and a wall thickness of 1.2mm.

[0180] B9: Cut to length: Cut the stretched copper tube into straight tubes with a length of 6000mm;

[0181] B10: Deburring and purging: Deburring and purging are performed on both ends of the copper tubes mentioned above.

[0182] B11: Packaging and Warehousing: Packaging and warehousing finished products.

[0183] Table 9. Process parameters for each step in the comparative example.

[0184]

[0185] Table 10 Comparative Example 1: Yield

[0186]

[0187] Table 11 Time taken for each step in the comparative example

[0188]

[0189] Compared with the comparative example, the embodiment achieves continuous stretching by processing the teeth and cross-shaped deformation in one step, replacing the previous method of stretching each piece multiple times. The yield rate reaches more than 89.30%, and the production efficiency is increased by more than 20%.

[0190] The above description is merely a preferred embodiment of the present invention and does not limit the implementation and protection scope of the present invention. Those skilled in the art should realize that any equivalent substitutions and obvious changes made based on the description and illustrations of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a non-grooved cross-shaped copper tube, characterized in that, include: Step S1: Molten copper is melted, cast, rolled, and drawn into tube blanks. Step S2: Flatten the tube end of the tube blank, insert the floating mandrel into the flattened part of the tube blank, and perform head-making treatment on the flattened part of the tube blank so that the floating mandrel is limited to the head-making part of the tube blank. Step S3: The tube blank passes through the pre-ellipse module and the cross groove module in sequence to prepare a cross copper tube. When the tube blank passes through the pre-ellipse module, it is stretched to form an elliptical copper tube. When the elliptical copper tube passes through the cross groove module, it is stretched and used in conjunction with the floating mandrel. The inner wall of the cross groove module is provided with several protruding teeth. After stretching, the cross copper tube is formed, and several grooves are formed on the outer wall of the cross copper tube. In step S3, the pre-elliptical module has a first guide cavity and a first forming cavity that are interconnected. The first guide cavity is a first cone shape, and the first forming cavity is an ellipse shape. The end of the first guide cavity near the first forming cavity is elliptical, and the end of the first guide cavity away from the first forming cavity is circular. In step S3, the cross groove module has a second guide cavity and a second forming cavity that are interconnected. The second guide cavity is in the shape of a second cone, and the second forming cavity is in the shape of a cross. The end of the second guide cavity near the second forming cavity is in the shape of a cross, and the end of the second guide cavity away from the second forming cavity is in the shape of an ellipse. A plurality of protruding teeth are provided on the inner wall of the second forming cavity. In step S3, the tube blank is sequentially drawn through the first guide cavity and the first forming cavity to form the elliptical copper tube; In step S3, the elliptical copper tube passes through the second guide cavity and the second forming cavity in sequence, and the floating core head passes through the second guide cavity and the second forming cavity. After stretching, it forms the cross copper tube with the groove on the outer wall. In step S3, the moving core head includes a support part, a guide part, and an extrusion part connected in sequence. The support part is elliptical, the guide part is a third cone, the extrusion part is cross-shaped, the end of the guide part near the extrusion part is cross-shaped, and the end of the guide part near the support part is elliptical. The guide part cooperates with the second guide cavity, and the extrusion part cooperates with the second forming cavity.

2. The method for preparing the irregularly shaped external grooved cross copper tube according to claim 1, characterized in that, Step S2 includes: Step S2.1: At least one recess is made on the side wall of the tube head of the tube blank; Step S2.2: After the tube blank is flattened, lubricating oil is added to the flattened part of the tube blank, and the floating mandrel is inserted into the flattened part of the tube blank so that the floating mandrel is positioned in the recess. Step S2.3: After the flattened part of the tube blank is headed, the floating mandrel is positioned between the recess and the headed part of the tube blank.

3. The method for preparing the irregularly shaped external grooved cross copper tube according to claim 1, characterized in that, The first guide cavity, the first molding cavity, the second guide cavity, and the second molding cavity are coaxially arranged; The long axis of the first guide cavity is directly opposite to the long axis of the first molding cavity, the long axis of the first molding cavity is directly opposite to the long axis of the second guide cavity, and the long axis of the second guide cavity is directly opposite to the long axis of the second molding cavity.

4. The method for preparing the irregularly shaped external grooved cross copper tube according to claim 1, characterized in that, In step S3, the pre-elliptical module includes: a first outer mold and an elliptical inner mold, the elliptical inner mold being installed inside the first outer mold, and the elliptical inner mold having the first guide cavity and the first forming cavity; In step S3, the cross groove module includes a second outer mold and a cross groove inner mold. The cross groove inner mold is installed inside the second outer mold, and the cross groove inner mold has a second guide cavity and a second forming cavity.

5. The method for preparing the irregularly shaped external grooved cross copper tube according to claim 1, characterized in that, The major axis cone angle β1 of the second guide cavity is 20°~36°, the minor axis cone angle γ1 of the second guide cavity is 20°~36°, the major axis cone angle β2 of the guide part is 20°~36°, the minor axis cone angle γ2 of the guide part is 20°~36°, the major axis cone angle β2 of the guide part is 2~4° smaller than the major axis cone angle β1 of the second guide cavity, and the minor axis cone angle γ2 of the guide part is 2~3° smaller than the minor axis cone angle γ1 of the second guide cavity; The major axis dimension D1 of the second molding cavity is 10~28mm, the minor axis dimension d1 of the second molding cavity is 10~25mm, and the thickness dimension H1 of the second molding cavity is 3~6mm; The major axis cone angle β of the first guide cavity is 20°~35°, the minor axis cone angle γ of the first guide cavity is 18°~35°, the major axis dimension D of the first forming cavity is 10~30mm, the minor axis dimension d of the first forming cavity is 10~25mm, and the thickness dimension H0 of the first forming cavity is 3~8mm. The major axis dimension D2 of the support part is 10~28mm, the minor axis dimension d2 of the support part is 8~23mm, the major axis dimension D3 of the extrusion part is 8~25mm, and the minor axis dimension d3 of the extrusion part is 5~20mm; The number of protruding teeth is 30 to 80, the tooth height H of the protruding teeth is 0.01 to 0.20 mm, and the tooth tip angle α of the protruding teeth is 10 to 60°.

6. The method for preparing the irregularly shaped external grooved cross copper tube according to claim 5, characterized in that, The first molding cavity has a first reduction ratio between its major axis D and the second molding cavity's major axis D1, which is 12-18%. The second molding cavity has a second reduction ratio between its minor axis d and the second molding cavity's minor axis d1, which is 12-18%. The second reduction ratio is 2% smaller than the first reduction ratio.

7. The method for preparing the irregularly shaped external grooved cross copper tube according to claim 6, characterized in that, The processing rate of the tube blank processed by the pre-elliptical module is 15-25%; the processing rate of the elliptical copper tube processed by the cross groove module is 10-20%.

8. The method for preparing the irregularly shaped external grooved cross copper tube according to claim 7, characterized in that, The inner wall of the second molding cavity has two first long axis U-shaped walls and two first short axis U-shaped walls spaced apart, and the first long axis U-shaped walls and the first short axis U-shaped walls are connected by a first arc-shaped wall. The outer wall of the extrusion section has two second long axis U-shaped walls and two second short axis U-shaped walls spaced apart, and the second long axis U-shaped walls and the second short axis U-shaped walls are transitioned by a second arc-shaped wall; The difference between the radius R1 of the first arc-shaped wall and the radius R2 of the second arc-shaped wall is used to set the wall thickness of the cross-shaped copper tube; Several of the aforementioned protruding teeth are respectively disposed on the two first long axis U-shaped walls, the two first short axis U-shaped walls, and the four first arc-shaped walls; The plurality of protruding teeth include: a plurality of first protruding teeth and a plurality of second protruding teeth, wherein the plurality of first protruding teeth are disposed on two first long axis U-shaped walls and two first short axis U-shaped walls, and the plurality of second protruding teeth are disposed on four first arc-shaped walls. The plurality of first protruding teeth on the first long axis U-shaped walls are arranged at equal intervals, the plurality of first protruding teeth on the first short axis U-shaped walls are arranged at equal intervals, and the plurality of second protruding teeth on the first arc-shaped walls are arranged at equal intervals. The bottom of the first short-axis U-shaped wall has a short-axis arc-shaped wall, and the bottom of the first long-axis U-shaped wall has a long-axis arc-shaped wall. The radius R3 of the short-axis arc-shaped wall is 10-25% larger than the radius R4 of the long-axis arc-shaped wall.

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