Extrusion die for forming single finned tube

Abstract

The utility model discloses an extrusion die for forming a single finned tube, which comprises an extrusion cylinder, a die holder, a die middle pad and a die tail pad which are assembled in sequence, and a core rod is arranged in the extrusion cylinder in a sliding manner; an extrusion die and a die support are fixedly arranged in the die holder; the core rod comprises a core rod working section and a core rod matrix, and the core rod working section is in threaded connection with the front end of the core rod matrix; the central point of the extrusion die is close to the fin, the position, corresponding to the center of the round tube of the formed single-finned tube, of an extrusion die cavity is far away from the fin, the core rod parent body, the extrusion die and the die support are coaxial, and the axis is a D axis; the positions of the core rod working section and the extrusion die cavity corresponding to the circular tube of the single finned tube are coaxial with the position of the die supporting cavity corresponding to the circular tube of the single finned tube, and the axis is an E axis; and the area of the upper cavity and the area of the lower cavity enclosed by the core rod matrix and the extrusion die are matched with each other. According to the utility model, the quantity of blanks in the upper cavity and the lower cavity at the extrusion end can be ensured to be similar, so that the flow velocity of the blanks is balanced, the straightness of a single-fin formed pipe is improved, and the device is suitable for the extrusion forming industry.

Description

Technical Field

[0001] The utility model belongs to the field of hot extrusion forming, in particular to an extrusion die for forming a single fin tube. Background Art

[0002] Finned tube is a heat exchange element, that is, fins are added to the surface of a circular heat exchange tube to increase the outer surface area or inner surface area of ​​the heat exchange tube, thereby improving the heat exchange efficiency. At present, the production of finned tubes mostly adopts hot extrusion process. The extrusion principle is: the metal billet in a high temperature state flows through a specific cavity composed of a mold under the action of three-dimensional compressive stress to form. This process gives full play to the plasticity of the material, which is conducive to the production of difficult-to-deform alloy tubes. The mold structure is simple, the production process is short, the product surface quality is good, and the dimensional accuracy is high.

[0003] The traditional hot extrusion die structure is as follows: Figure 1 As shown, it includes an extrusion barrel 8, which includes an inner liner 803, a middle liner 802 and an outer shell 801 assembled in an interference fit manner. An extrusion rod 13 is slidably arranged at the center line of the extrusion barrel 8, an extrusion gasket 9 is arranged at the front end of the extrusion rod 13, and a core rod 12 is slidably arranged at the center line of the extrusion rod 13. The core rod 12 is used to size the center hole of the blank, and the rear end of the core rod 12 is threadedly connected to the core rod support rod 11; a die base 1, a die middle pad 2 and a die tail pad 3 are fixed to the front end of the extrusion barrel 8 in sequence, and an extrusion die 4 is arranged inside the die base 1 (see the specific structure) Figure 2 (a)) and mold support 6 (for specific structure, see Figure 2 (b)), an extrusion cavity 5 is formed between the core rod 12 and the inner liner 803 of the extrusion cylinder 8, and a lubricating glass pad is placed at one end of the extrusion die 4 close to the extrusion cavity 5. Figure 1 The glass pad is not shown. The extrusion principle of the die is as follows: a solid metal blank is heated and placed in the extrusion cavity 5, the core rod support rod 11 is pushed forward so that the core rod 12 pierces the solid metal blank, and after the piercing, the extrusion rod 13 is pushed forward again, and the extrusion gasket 9 is pushed by the extrusion rod 13 to apply force to the blank to deform it, and finally the required pipe is extruded from the front end.

[0004] Since the center of the core rod 12, the center of the extrusion die 4, and the center of the die support 6 in the hot extrusion forming die are all located on the center line of the extrusion barrel 8, it is suitable for producing a biaxially symmetrical long-axis fin tube with equal cross-section (also called a double-fin tube 10). Figure 3 (a) is one of the double-finned tubes 10. A rectangular block is provided at the top and bottom of the outer circumference of the hollow circular tube in the longitudinal section. The length of the rectangular block is the same as the length of the circular tube. Equal cross-section means that the shape and area of ​​the longitudinal section at any position of the tube are the same. Biaxial symmetry means that the tube has two symmetry axes, horizontal and vertical, so that the tube is symmetrical up and down and left and right. When forming this type of tube, the upper cavity area S1 and the lower cavity area S2 surrounded by the core rod 12 and the extrusion die 4 are also symmetrical up and down, see Figure 3 (b), so that the amount of billet flowing through S1 and S2 during the extrusion process is the same, so that under the action of the extrusion gasket 9, the flow speed of the metal billet is balanced everywhere, and the surface quality of the final formed pipe is good.

[0005] However, for the uniaxial symmetrical long-axis finned tube (also called single-finned tube 15), its structure is as follows Figure 4 As shown in (a), from the longitudinal section, there is only one rectangular block set on the outer periphery of the circular tube, so the tube has only one vertical symmetry axis and is bilaterally symmetrical about the symmetry axis. Figure 1 When extruding the die in the mold, the shape of the extrusion die 4 needs to be adjusted to the shape of a single fin tube, but if Figure 4 As shown in (b), at this time, the upper cavity area S1' surrounded by the core rod 12 and the extrusion die 4 is larger than the lower cavity area S2', and the position of the billet in the cavity is fixed. Then, during extrusion, the lower cavity area S2' is small, but the corresponding billet amount is too much, which is prone to material blockage; in addition, the cavity corresponding to S2' has a large amount of billet and a high extrusion flow rate, while the cavity corresponding to S1' has a slow billet extrusion flow rate, which makes the produced pipe easy to bend and has poor surface quality. Utility Model Content

[0006] In order to solve the above deficiencies in the prior art, the utility model aims to provide an extrusion die for forming a single-fin tube, so as to achieve the purpose of balancing the flow rate of the blank in various parts of the cavity when the single-fin tube is extruded and formed, thereby ensuring the straightness of the formed tube.

[0007] In order to achieve the above purpose, the technical solution adopted by the utility model is as follows:

[0008] An extrusion die for forming a single-fin tube comprises an extrusion barrel, an extrusion rod is slidably arranged at the center line of the extrusion barrel, an extrusion gasket is arranged at the front end of the extrusion rod, a core rod is slidably arranged at the center line of the extrusion rod, the extrusion gasket is sleeved on the outer diameter of the core rod, and the rear end of the core rod is threadedly connected with a core rod support rod; a die seat, a die middle pad and a die tail pad are fixedly arranged at the front end of the extrusion barrel in sequence, an extrusion die and a die support are fixedly arranged inside the die seat, the extrusion die is hollow inside to form an extrusion die cavity, a glass pad is arranged at the extrusion end of the extrusion die, the die support is hollow inside to form a die support cavity, the shape of the extrusion die cavity is adapted to the shape of the die support cavity, and the shape and size of the extrusion die cavity are adapted to the outer periphery of the single-fin tube;

[0009] The mandrel comprises a mandrel working section and a mandrel matrix which are fixedly connected. The mandrel matrix is ​​threadedly connected to the mandrel support rod. The mandrel working section is fixedly arranged at the front end of the mandrel matrix. The outer diameter of the mandrel working section is adapted to the inner diameter of the single fin tube.

[0010] The center point of the extrusion die is arranged close to the fin, the core rod matrix, the extrusion die and the die support are coaxial, and the axis is the D axis; the position corresponding to the center of the single-fin tube on the extrusion die cavity is arranged away from the fin, the position of the core rod working section and the extrusion die cavity corresponding to the single-fin tube is coaxial with the position of the die support cavity corresponding to the single-fin tube, and the axis is the E axis, the D axis is parallel to the E axis, and the horizontal plane where the D axis is located is used as the dividing line, and the upper cavity area and the lower cavity area surrounded by the core rod matrix and the extrusion die are adapted to each other.

[0011] As a limitation of the present utility model, the diameter of the mandrel working section is smaller than the diameter of the mandrel body, the lower edge of the mandrel working section and the lower edge of the mandrel body are on the same horizontal line, a smooth transition portion is provided between the mandrel working section and the mandrel body, the maximum diameter of the smooth transition portion is equal to the diameter of the mandrel body, the minimum diameter is equal to the diameter of the needle tip working section, and the top surface of the smooth transition portion is an arc-shaped surface.

[0012] As another limitation of the present invention, the extrusion die cavity includes an arc area corresponding to the round tube portion of the single-fin tube, and a fin area corresponding to the fin portion of the single-fin tube, and the shape of the die support cavity is the same as the shape of the extrusion die cavity; the extrusion end of the extrusion die is provided with a platform for placing a glass pad; the arc area of ​​the extrusion die cavity, the core rod working section and the arc area of ​​the die support cavity are coaxial.

[0013] As a further limitation of the utility model, the axial thickness of the extrusion die is 100 mm to 120 mm, the angle β at the inlet is 110° to 135°, and the angle α at the assembly of the extrusion die and the extrusion barrel is 60° to 62°.

[0014] As another limitation of the present invention, the mold support is arranged inside the mold base and the mold pad, and the mold support and the mold base, and the mold support and the mold pad are fixedly connected.

[0015] As a further limitation of the present utility model, the mold support includes a first working section and a second working section which are coaxial and fixedly connected, the first working section is a cylindrical structure and is fixedly connected to the mold base, the second working section is a conical structure and is fixedly connected to the mold pad, the smallest diameter end of the second working section is arranged away from the mold base, and the largest diameter end is fixedly connected to the first working section; the interior of the mold pad is a cone that is adapted to the shape of the second working section.

[0016] As a further limitation of the present invention, the diameter of the second working section near the first working section is larger than the diameter of the first working section, and a slot for engaging with the mold base is formed between the first working section and the second working section.

[0017] As a further limitation of the present invention, the taper angle γ at the inlet of the mold pad is 20° to 45°.

[0018] Due to the adoption of the above technical solution, the utility model has the following beneficial effects compared with the prior art:

[0019] The utility model is an improvement on the extrusion die in the prior art, and the specific improvement lies in adjusting the structures of the core rod, the extrusion die and the die support, and moving the position of the center of the single-fin tube on the extrusion die cavity body toward the direction away from the fin (that is, moving the extrusion die cavity body as a whole downward) by a certain distance (from point e to point g), so that the upper cavity area S1' and the lower cavity area S2' surrounded by the core rod mother body and the extrusion die with the horizontal plane where the D axis is located as the dividing line are nearly equal; correspondingly, the center of the core rod working section and the position of the center of the single-fin tube on the extrusion die cavity body are also moved downward by a certain distance, ensuring that the position of the core rod working section and the extrusion die cavity body corresponding to the single-fin tube are coaxial with the position of the die support cavity body corresponding to the single-fin tube; when extruding with the mold, the amount of blanks located in the upper cavity and the lower cavity is the same, which solves the problem of material suffocation or bending of the formed single-fin tube due to the small area of ​​the lower cavity but a large amount of blanks in the prior art.

[0020] In summary, when the single-fin tube is extruded, the utility model can ensure that the amount of blank in the upper cavity and the lower cavity surrounded by the core rod matrix at the extrusion end and the extrusion die is similar, so that the flow rate of the blank is balanced and the straightness of the formed tube is improved; the utility model is suitable for the extrusion forming industry and is used for forming uniaxially symmetrical long-axis fin tubes with equal cross-sections. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The present invention is described in further detail below in conjunction with the accompanying drawings and specific embodiments.

[0022] Figure 1 It is a structural schematic diagram of an extrusion forming die in the prior art;

[0023] Figure 2 (a) is a schematic longitudinal section diagram of an extrusion die in the prior art, and (b) is a schematic longitudinal section diagram of a die support in the prior art;

[0024] Figure 3 (a) is a schematic diagram of a longitudinal section of a double-fin tube to be formed, and (b) is a schematic diagram of the structure of a forming cavity surrounded by an extrusion die and a core rod when extruding the double-fin tube;

[0025] Figure 4 (a) is a schematic diagram of a longitudinal section of a single-fin tube to be formed, and (b) is a schematic diagram of the structure of a forming cavity surrounded by an extrusion die and a core rod when extruding a single-fin tube;

[0026] Figure 5 It is a schematic diagram of the structure of an embodiment of the utility model;

[0027] Figure 6It is a schematic diagram of the structure of the extrusion die cavity before and after it moves downward in the embodiment of the utility model;

[0028] Figure 7 It is a schematic structural diagram of a molding cavity surrounded by an extrusion die and a core rod matrix in an embodiment of the utility model;

[0029] Figure 8 (a) is a schematic diagram of the structure of the extrusion die in the embodiment of the utility model, (b) is a cross-sectional view along the AA line in (a), and (c) is a schematic diagram of the three-dimensional structure of the extrusion die in the embodiment of the utility model;

[0030] Fig. 9 (a) is a schematic diagram of the main structure of the mold support in the embodiment of the utility model, (b) is a cross-sectional view along the BB direction in (a), and (c) is a schematic diagram of the three-dimensional structure of the mold support in the embodiment of the utility model;

[0031] Fig.10 (a) is a schematic diagram of the main structure of the core rod in the embodiment of the utility model, and (b) is a cross-sectional view along the CC direction in (a);

[0032] Fig.11 This is a schematic diagram of the three-dimensional structure of the core rod in the embodiment of the utility model;

[0033] Fig.12 (a) is a schematic longitudinal section diagram of the mold-in-pad in an embodiment of the utility model, and (b) is a schematic three-dimensional structure diagram of the mold-in-pad;

[0034] Fig.13 (a) is a schematic longitudinal section view of a mold base in an embodiment of the present utility model, and (b) is a schematic three-dimensional structure view of a mold base in an embodiment of the present utility model;

[0035] Fig.14 This is a schematic diagram of the structure of the single fin tube finally formed in the embodiment of the utility model;

[0036] Fig.15 It is a schematic diagram of the coaxial structure of the core rod working section, the arc area of ​​the extrusion die cavity and the arc area of ​​the die support cavity.

[0037] In the figure: 1-die base, 2-middle die pad, 3-die tail pad;

[0038] 4-extrusion die, 401-extrusion die cavity, 4011-arc area, 4012-fin area, 402-platform, 403-groove;

[0039] 5-Extrusion cavity;

[0040] 6-mold support, 601-mold support cavity, 602-first working section, 603-second working section;

[0041] 7- Glass mat;

[0042] 8-extrusion cylinder, 801-shell, 802-middle lining, 803-inner lining;

[0043] 9-extrusion gasket, 10-double fin tube, 11-mandrel support rod;

[0044] 12-mandrel, 121-mandrel working section, 122-mandrel body, 123-mandrel body outer thread section, 124-smooth transition section;

[0045] 13-extruded rod, 14-blank, 15-single fin tube, 16-horizontal plane where D axis is located. DETAILED DESCRIPTION

[0046] The preferred embodiment of the utility model is described below in conjunction with the accompanying drawings. It should be understood that the extrusion die for forming a single fin tube described herein is a preferred embodiment, which is only used to illustrate and explain the utility model and does not constitute a limitation of the utility model.

[0047] The directional terms or positional relationships such as "upper", "lower", "front", and "back" described in the embodiments are based on the drawings in the specification of the utility model. Figure 1 The orientation relationship is only for the convenience of describing the present invention and simplifying the description. It does not indicate or imply that the device or element must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be understood as a limitation on the content protected by the present invention.

[0048] This embodiment includes an extrusion cylinder 8, an extrusion rod 13 is slidably arranged at the center line of the extrusion cylinder 8, an extrusion gasket 9 is arranged at the front end of the extrusion rod 13, a core rod 12 is slidably arranged at the center line of the extrusion rod 13, the extrusion gasket 9 is sleeved on the outer diameter of the core rod 12, and the rear end of the core rod 12 is threadedly connected to the core rod support rod 11; a die base 1, a die center pad 2 and a die tail pad 3 are fixedly arranged at the front end of the extrusion cylinder 8 in sequence, an extrusion die 4 and a die support 6 are fixedly arranged inside the die base 1, the extrusion die 4 is hollow inside to form an extrusion die cavity 401, a glass pad 7 is arranged at the extrusion end of the extrusion die 4, the die support 6 is hollow inside to form a die support cavity 601, the shape of the extrusion die cavity 401 is adapted to the shape of the die support cavity 601, and the shape and size of the extrusion die cavity 401 are adapted to the outer periphery of the formed pipe, where the outer periphery is the outer contour, and this part of the content is the prior art.

[0049] This embodiment finally forms a single fin tube 15, see Figure 4 (a) Fig.14 , the single fin is located above the circular tube, such as Figure 4As shown in (b), the C axis is the horizontal symmetry axis of the extrusion die 4, and the C axis is the dividing line. Since fins are added to the upper cavity, the upper cavity area S1' is larger than the lower cavity area S2', and the amount of billet flowing through the upper cavity and the lower cavity is similar. Then, there is too much billet 14 in the lower cavity with a smaller area, and the flow rate is fast, resulting in bending of the formed tube.

[0050] This embodiment improves the structure of the extrusion die 4 by moving the extrusion die cavity 401 downward by a certain distance S. Figure 6 , Figure 6 The middle dotted line represents the position of the extrusion die cavity 401 before the downward movement. The S value is calculated based on the center of gravity of the single fin tube cavity. In this embodiment, S=15mm. After the downward movement, in the cavity surrounded by the core rod matrix 122 and the extrusion die 4, the horizontal plane 16 where the D axis is located is used as the dividing interface. The upper cavity area S1' and the lower cavity area S2' are adapted. Here, the adaptation means that S1' and S2' are nearly equal, see Figure 7 , then the amount of billet flowing through the upper cavity and the lower cavity is similar, the flow rate of the billet 14 is balanced during extrusion, and the straightness of the final formed tube is high. At the same time, in order to ensure normal extrusion, this embodiment also improves the structure of the mandrel 12 and the die support 6, which can ensure that the position of the mandrel working section 121 and the corresponding single fin tube 15 on the extrusion die cavity 401 is coaxial with the position of the corresponding single fin tube 15 on the die support cavity 601.

[0051] The specific improvements of the core rod 12, the extrusion die 4, and the die support 6 are as follows:

[0052] 1. Mandrel 12;

[0053] like Figure 5 , Fig.10 , Fig.11 As shown, the mandrel 12 includes an integrally formed mandrel working section 121, a mandrel body 122 and a mandrel body outer thread section 123. The mandrel body outer thread section 123 is threadedly connected to the mandrel support rod 11, the mandrel body 122 is a cylindrical structure, the mandrel working section 121 is arranged at the front end of the mandrel body 122, and the mandrel working section 121 determines the internal profile of the single fin tube 15. In other words, the outer diameter of the mandrel working section 121 is adapted to the inner diameter of the single fin tube 15, and the adaptation here means that the outer diameter of the mandrel working section 121 is equal to the inner diameter of the single fin tube 15. In this embodiment, the length of the mandrel working section 121 is 300 mm.

[0054] like Fig.10 , Fig.11As shown, the diameter of the mandrel working section 121 is smaller than the diameter of the mandrel matrix 122, and the lower edge of the mandrel working section 121 is on the same horizontal line as the lower edge of the mandrel matrix 122. In order to ensure that the blank 14 flows more smoothly from the mandrel matrix 122 to the mandrel working section 121, a smooth transition portion 124 is provided between the mandrel working section 121 and the mandrel matrix 122 in this embodiment. Fig.10 As shown in (a), the smooth transition portion 124 is triangular in shape, and the vertex is located on the lower edge of the core rod working section 121. The right end of the smooth transition portion 124 is the maximum diameter end, and the maximum diameter is equal to the diameter of the core rod mother body 122, and the left end is the minimum diameter end, and the minimum diameter is equal to the diameter of the core rod working section 121; the top surface of the smooth transition portion 124 is an arc surface, and in this embodiment, the arc surface is concave downward and the opening is upward.

[0055] like Fig.10 As shown, the central axis of the mandrel working section 121 is the E axis, which is lower than the central axis D axis of the mandrel matrix 122, and the distance between the two is S=15mm. During extrusion, the mandrel working section 121 is used to perforate the blank 14, and the inner diameter of the round tube portion of the formed single-fin tube 15 is equal to the outer diameter of the mandrel working section 121.

[0056] 2. Extrusion die 4;

[0057] like Figure 5 , Figure 8 As shown, the shape and size of the extrusion die cavity 401 are matched with the outer periphery of the single fin tube 15. Matching here means that the shape and size of the extrusion die cavity 401 are consistent with the outer contour of the single fin tube 15; the axial thickness of the extrusion die 4 in this embodiment is 100mm-120mm, which can be selected as 100mm, 110mm or 120mm, and is 100mm in this embodiment. Figure 8 As shown in (b), in this embodiment, the angle β at the entrance of the extrusion die 4 is 110°~135°, and 110°, 120°, and 135° can be selected. In this embodiment, β is 115°. The angle α at the assembly of the extrusion die 4 and the extrusion cylinder 8 is 60°~62°, and 60°, 61°, and 62° can be selected. In this embodiment, α is 60°.

[0058] like Figure 8 As shown in (a) and 8 (c), the interior of the extrusion die 4 is hollow to form an extrusion die cavity 401, and the extrusion die cavity 401 includes an arc area 4011 corresponding to the round tube part of the single-fin tube 15, and a fin area 4012 corresponding to the fin part of the single-fin tube 15. The arc area 4011 of the extrusion die cavity 401 is coaxial with the core rod working section 121, and the central axis is the E axis, while the central axis of the extrusion die 4 is the D axis.

[0059] like Figure 6 , Figure 8As shown, the extrusion mold cavity 401 is located at the dotted line position before moving downward, the center point of the arc area 4011 is point e, and the center point of the arc area 4011 is point g after moving downward, and the downward distance is S=15mm. Figure 7 As shown, with the horizontal plane 16 where the D axis is located as the interface, after moving downward, the upper cavity area S1' and the lower cavity area S2' formed by the core rod matrix 122 and the extrusion die 4 are nearly equal, so the amount of billet flowing through the upper cavity and the lower cavity is similar, which can achieve a balanced flow rate of the billet 14 during extrusion. It should be supplemented that Figure 7 The figure shows the cavity formed by the core rod matrix 122 and the extrusion die 4. The core rod 12 is an eccentric structure. The center of the core rod working section 121 and the center of the core rod matrix 122 are not on the same straight line, so they cannot pass through Figure 7 It is determined that the wall thickness of the circular tube portion of the finally formed single-fin tube 15 is uneven.

[0060] like Figure 8 As shown in FIGS. 8(a) and 8(c), the extrusion end of the extrusion die 4 is provided with a platform 402. The extrusion end here refers to the end of the extrusion die 4 that first contacts the billet 14 when the billet 14 is extruded, that is, Figure 8 (b) The right end of the extrusion die 4. The platform 402 is used to place the glass pad 7, and the extrusion die 4 supports the glass pad 7. Otherwise, the glass pad 7 has no support surface and is prone to fall due to impact during extrusion. In addition, in order to facilitate the processing of the platform 402, a groove 403 is also provided on the extrusion die 4. In this embodiment, the groove 403 is close to the position of the fin area 4012. In this embodiment, the width of the platform 402 at the bottom entrance of the extrusion die 4 is L, and the width L' at the top entrance of the groove 403 is greater than 8 mm, which is convenient for the glass pad 7 to fit better.

[0061] Similar to the extrusion die 4 in the prior art, the extrusion die 4 is also provided with an inlet transition zone, an intermediate sizing zone and an outlet anti-conical zone. The shape of the intermediate sizing zone is consistent with the outer contour of the single-fin tube 15. In this embodiment, the arc radius of the inlet transition zone is 5mm to 16mm, and the length of the intermediate sizing zone is 8mm to 20mm. Otherwise, if the length of the intermediate sizing zone is too short, the mold will be deformed after several extrusions; if the length of the intermediate sizing zone is too long, the friction is large, which is not conducive to metal flow; preferably, the arc radius of the inlet transition zone is 15mm, and the length of the intermediate sizing zone is 16mm.

[0062] 3. Mould support 6;

[0063] like Figure 5 , Fig. 9As shown, the die support 6 is arranged inside the die base 1 and the die pad 2. The die support 6 and the die base 1, and the die support 6 and the die pad 2 are fixedly connected, so that the die support 6 is fixed more firmly. The die support 6 includes a first working section 602 and a second working section 603 that are coaxial and fixedly connected. The first working section 602 is a cylindrical structure and is fixedly connected to the die base 1; the second working section 603 is a conical structure, and its smallest diameter end is arranged away from the die base 1, and the largest diameter end is fixedly connected to the first working section 602. The connection between the extrusion die 4 and the die support 6 is the prior art. It should be noted that the taper between the die support 6 and the die pad 2 is matched to form a more solid structure, which can withstand greater extrusion force during extrusion, avoid mold cracking, and improve the stability of the mold. Correspondingly, the inside of the die pad 2 is a cone that matches the shape of the second working section 603, see Fig.12 The cone angle γ at the entrance of the mold pad 2 is 20° to 45°, and can be 20°, 30° or 45°. In this embodiment, γ is 30°.

[0064] It should be noted that if Fig. 9 As shown in (b), the diameter of the second working section 603 near the first working section 602 is larger than the diameter of the first working section 602. A slot for engaging with the mold base 1 is formed between the first working section 602 and the second working section 603. The slot is similar to a step and is used for engaging with the mold base 1, so that the connection between the two is more secure. Figure 5 , the structure of mold base 1 participates Fig.13 .

[0065] The interior of the die support 6 is hollow to form a die support cavity 601, and the contour shape of the die support cavity 601 is adapted to the extrusion die cavity 401. Adaptation here means that the two have the same shape, but the size of the die support cavity 601 is 6mm to 15mm larger than the extrusion die cavity 401, preferably, 12mm larger, to prevent the single-fin tube 15 from being scratched when passing through the die support 6 after being extruded from the extrusion die 4.

[0066] It should be noted that the extrusion die 4 is described in detail as a representative: Figure 6 , 7As shown, the center point of the extrusion die 4 is point e, and the center point of the arc area 4031 on the extrusion die cavity 401 is point g. Point g is lower than point e, and the spacing is S=15mm. The "lower than" here only represents the orientation relationship of this embodiment. If the fin is located below, then point g should be 15mm higher than point e. As long as the center point of the extrusion die 4 is close to the fin and the center point of the arc area 4031 on the extrusion die cavity 401 is far away from the fin, the upper cavity area S1' and the lower cavity area S2' surrounded by the core rod mother 122 and the extrusion die 4 with the horizontal plane 16 where the D axis is located are used as the dividing line are approximately equal. In this way, it can be ensured that the amount of billet flowing through the upper cavity and the lower cavity is similar, the flow rate of the billet 14 is balanced during extrusion, and the straightness of the final formed pipe is high. At the same time, the improved mandrel working section 121, the position of the extrusion die cavity 401 corresponding to the single fin tube 15 (i.e., the arc area 4011 of the extrusion die cavity 401) and the position of the die support cavity 601 corresponding to the single fin tube 15 (i.e., the arc area of ​​the die support cavity 601) are coaxial, and the axis is the E axis, which ensures the accuracy of the perforation position, and the mandrel mother body 122, the extrusion die 4 and the die support 6 are coaxial, and the axis is the D axis, which is parallel to the E axis, and the E axis is lower than the D axis by S=15mm, see Fig.15 .

[0067] When using this embodiment, the solid metal blank 14 is heated to a corresponding temperature (for example, 1100°C-1190°C), coated with glass powder lubricant, and loaded into the extrusion cylinder 8. The core rod support rod 11 is pushed forward so that the core rod working section 121 perforates the solid metal blank 14. After perforation, extrusion is performed, and the extrusion rod 13 is used to push the extrusion gasket 9 and the blank 14 forward to the front end of the extrusion die 4. After the blank 14 contacts the glass pad 7 close to the front end of the extrusion die 4, the extrusion rod 13 continues to push forward and applies pressure to the blank 14 through the extrusion gasket 9, first causing the blank 14 to undergo filling deformation and eliminating the gap between the outer circle of the blank 14 and the inner wall of the extrusion cylinder 8. Then the blank 14 is extruded into the cavity formed by the extrusion die 4 and the core rod working section 121. Since the upper cavity area S1' is almost equal to the lower cavity area S2', the amount of blank in the upper cavity is similar to that in the lower cavity, and the flow rate of the blank 14 is balanced, so that the required single-fin tube 15 with uniform wall thickness and high straightness is extruded.

[0068] It should be noted that the above is only a preferred embodiment of the utility model and is not intended to limit the utility model. Although the utility model is described in detail with reference to the above embodiment, those skilled in the art can still modify the technical solutions recorded in the above embodiment or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the utility model shall be included in the protection scope of the utility model.

Claims

1. An extrusion die for forming a single-fin tube, comprising an extrusion barrel, an extrusion rod is slidably arranged at the center line of the extrusion barrel, an extrusion gasket is arranged at the front end of the extrusion rod, a core rod is slidably arranged at the center line of the extrusion rod, the extrusion gasket is sleeved on the outer diameter of the core rod, and the rear end of the core rod is threadedly connected with a core rod support rod; a die seat, a die middle pad and a die tail pad are fixedly arranged at the front end of the extrusion barrel in sequence, an extrusion die and a die support are fixedly arranged inside the die seat, the extrusion die is hollow inside to form an extrusion die cavity, a glass pad is arranged at the extrusion end of the extrusion die, the die support is hollow inside to form a die support cavity, the shape of the extrusion die cavity is adapted to the shape of the die support cavity, and the characteristics are as follows: The shape and size of the extrusion die cavity are adapted to the outer circumference of the single-fin tube; The mandrel comprises a mandrel working section and a mandrel matrix which are fixedly connected. The mandrel matrix is ​​threadedly connected to the mandrel support rod. The mandrel working section is fixedly arranged at the front end of the mandrel matrix. The outer diameter of the mandrel working section is adapted to the inner diameter of the single fin tube. The center point of the extrusion die is arranged close to the fin, the core rod matrix, the extrusion die and the die support are coaxial, and the axis is the D axis; the position corresponding to the center of the single-fin tube on the extrusion die cavity is arranged away from the fin, the position of the core rod working section and the extrusion die cavity corresponding to the single-fin tube is coaxial with the position of the die support cavity corresponding to the single-fin tube, and the axis is the E axis, the D axis is parallel to the E axis, and the horizontal plane where the D axis is located is used as the dividing line, and the upper cavity area and the lower cavity area surrounded by the core rod matrix and the extrusion die are adapted to each other.

2. The extrusion die for forming a single-fin tube according to claim 1, characterized in that: The diameter of the mandrel working section is smaller than the diameter of the mandrel body, the lower edge of the mandrel working section and the lower edge of the mandrel body are on the same horizontal line, a smooth transition portion is provided between the mandrel working section and the mandrel body, the maximum diameter of the smooth transition portion is equal to the diameter of the mandrel body, the minimum diameter is equal to the diameter of the needle tip working section, and the top surface of the smooth transition portion is an arc surface.

3. The extrusion die for forming a single-fin tube according to claim 1 or 2, characterized in that: The extrusion die cavity includes an arc area corresponding to the round tube part of the single-fin tube, and a fin area corresponding to the fin part of the single-fin tube. The shape of the die support cavity is the same as that of the extrusion die cavity. The extrusion end of the extrusion die is provided with a platform for placing a glass pad. The arc area of ​​the extrusion die cavity, the core rod working section and the arc area of ​​the die support cavity are coaxial.

4. The extrusion die for forming a single-fin tube according to claim 3, characterized in that: The axial thickness of the extrusion die is 100 mm to 120 mm, the angle β at the entrance is 110° to 135°, and the angle α at the assembly of the extrusion die and the extrusion barrel is 60° to 62°.

5. The extrusion die for forming a single-fin tube according to any one of claims 1, 2 and 4, characterized in that: The mold support is arranged inside the mold base and the mold center pad, and the mold support and the mold base, as well as the mold support and the mold center pad are all fixedly connected.

6. The extrusion die for forming a single-fin tube according to claim 5, characterized in that: The mold support includes a first working section and a second working section which are coaxial and fixedly connected. The first working section is a cylindrical structure and is fixedly connected to the mold base, and the second working section is a conical structure and is fixedly connected to the mold pad. The smallest diameter end of the second working section is arranged away from the mold base, and the largest diameter end is fixedly connected to the first working section; the interior of the mold pad is a cone that matches the shape of the second working section.

7. The extrusion die for forming a single-fin tube according to claim 6, characterized in that: The diameter of the second working section near the first working section is larger than the diameter of the first working section, and a slot for engaging with the mold base is formed between the first working section and the second working section.

8. The extrusion die for forming a single-fin tube according to claim 6 or 7, characterized in that: The taper angle γ at the inlet of the mold pad is 20° to 45°.

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