Steel pipe stretching structure for steel pipe cold drawing machine

Abstract

The utility model provides a steel pipe drawing structure for a steel pipe cold drawing machine, which comprises a core shaft, an inner ring body, an outer ring body, a power device and a synchronous drawing device, the core shaft, the inner ring body and the outer ring body are coaxially arranged, the core shaft penetrates through the inner side of the inner ring body, the outer ring body is sleeved outside the inner ring body, and the inner side surface of the outer ring body is matched with the outer side surface of the inner ring body in an abutting way; the steel pipe penetrates through the inner side of the inner ring body, the steel pipe and the mandrel are coaxially arranged, the mandrel penetrates through an inner cavity of the steel pipe, a circle of extrusion ring structure is arranged on the inner side face of the inner ring body, the extrusion ring structure enables the inner ring body to be provided with a circle of inner diameter reduction part, the inner diameter of the inner diameter reduction part is smaller than the outer diameter of the steel pipe, and then the steel pipe is extruded at the inner diameter reduction part. The friction strength between the inner ring body and the outer surface of the steel pipe can be effectively reduced, the service life of the inner ring body is greatly prolonged, and meanwhile, the steel pipe stretching quality defect caused by heating deformation of the inner ring body can be effectively prevented.

Description

Technical Field

[0001] This utility model belongs to the technical field of cold drawing machine devices, specifically relating to a steel pipe stretching structure for a steel pipe cold drawing machine. Background Technology

[0002] Cold drawing is a common metalworking technique that changes the shape and size of a metal material by applying tensile force at room temperature. Compared to hot working, cold working can improve the strength, hardness, and wear resistance of materials while maintaining a better surface finish. During cold drawing, the grain size of the material changes, leading to a significant improvement in its mechanical properties, particularly strength and ductility.

[0003] In this process, cold drawing machines for steel pipes are mainly used to adjust the outer diameter and wall thickness of steel pipes, as well as improve their mechanical properties. Existing cold drawing machines generally employ a mandrel inserted inside the steel pipe, with an extrusion ring (with an inner diameter smaller than the outer diameter) placed outside as the pipe's stretching structure. By moving the extrusion ring along the pipe's axial direction, a thicker pipe is forcibly extruded into a thinner, longer pipe. Simultaneously, the presence of the mandrel prevents the pipe from bending. However, existing cold drawing machines generate significant friction with the steel pipe during extrusion. Even with lubrication, the extrusion ring gradually wears down over time. Furthermore, the extrusion ring is bulky, heavy, inconvenient to replace, and costly. In addition, this type of cold drawing machine's stretching structure is only compatible with one type of steel pipe; when the wall thickness of the stretched pipe needs to be changed, the entire stretching structure must be replaced, resulting in high costs.

[0004] Therefore, a new steel pipe stretching structure needs to be designed to solve the problems of high wear and low adaptability of the current steel pipe stretching structure of cold drawing machines. Utility Model Content

[0005] Based on the technical problems mentioned in the background art, this utility model proposes a steel pipe stretching structure for a steel pipe cold drawing machine.

[0006] The present invention adopts the following technical solution:

[0007] A steel pipe stretching structure for a cold drawing machine includes a mandrel, an inner ring body, an outer ring body, a power unit, and a synchronous traction device. The mandrel, inner ring body, and outer ring body are coaxially arranged. The mandrel passes through the inner side of the inner ring body, and the outer ring body is fitted around the outer side of the inner ring body with its inner side abutting against the outer side of the inner ring body. The steel pipe passes through the inner side of the inner ring body and is coaxially arranged with the mandrel. The mandrel passes through the inner cavity of the steel pipe. A compression ring structure is provided on the inner side of the inner ring body, which gives the inner ring body a certain... The inner diameter of the inner ring is smaller than the outer diameter of the steel pipe, which causes the steel pipe to be squeezed in the inner diameter reduction section. The inner side of the steel pipe at the inner diameter reduction section abuts against the mandrel, and the outer side abuts against the extrusion ring structure. The synchronous puller connects the inner ring body and the outer ring body at the same time, so that the inner ring body and the outer ring body are positioned and connected. The power device is connected to the outer ring body or the synchronous puller. The power device is used to pull the inner ring body and the outer ring body to move axially synchronously, thereby changing the position of the inner diameter reduction section on the steel pipe.

[0008] To optimize the technical solution, the following further measures will be taken:

[0009] The outer surface of the aforementioned inner ring body is provided with several inner ring guide pulley units. The inner ring guide pulley units are arranged with equal arc around the outer surface of the inner ring body. The inner ring guide pulley unit includes an inner ring pulley shaft and an inner ring guide pulley. The inner ring pulley shaft is fixed on the outer surface of the inner ring body, and the inner ring guide pulley is rotatably mounted on the inner ring pulley shaft. The inner ring guide pulley abuts against the inner surface of the outer ring body. When the outer ring body moves axially, the inner ring guide pulley rolls on the inner surface of the outer ring body, so that the inner ring body and the outer ring body can produce axial relative movement.

[0010] The outer surface of the aforementioned inner ring body is provided with several axially extending inner ring slide rails, and the inner surface of the outer ring body is provided with several outer ring guide pulley units. Each outer ring guide pulley unit includes an outer ring pulley shaft and an outer ring guide pulley. The outer ring pulley shaft is fixed on the inner surface of the outer ring body, and the outer ring guide pulley is rotatably mounted on the outer ring pulley shaft. The outer ring guide pulley is limited in the inner ring slide rails and can roll in the inner ring slide rails.

[0011] The extrusion ring structure described above consists of several extrusion wheel units. The extrusion wheel units are arranged with equal arc around the inner inner ring body. Each extrusion wheel unit includes an extrusion wheel shaft and an extrusion wheel. The extrusion wheel shaft is fixed on the inner inner surface of the inner ring body, and the extrusion wheel is rotatably mounted on the extrusion wheel shaft. All the extrusion wheels together form an annular cavity. The diameter of the annular cavity is smaller than the outer diameter of the steel pipe. The steel pipe passes through the annular cavity. The extrusion wheels extrude the outer surface of the steel pipe, causing the steel pipe wall to move and deform inward. When the inner ring body moves axially, the extrusion wheel and the outer surface of the steel pipe roll together.

[0012] The surface of the extrusion wheel described above is an arc-shaped surface with a concave center, which is adapted to the curvature of the outer contour of the deformed steel pipe.

[0013] The aforementioned power unit includes a motor, a centrifugal impeller, a connecting rod, and an outer ring connecting column. A centrifugal column is fixed at the non-axial position of the impeller surface. The outer ring connecting column is fixed to the outer surface of the outer ring. The motor is connected to the centrifugal impeller via a transmission. One end of the connecting rod is hinged to the centrifugal column, and the other end is hinged to the outer ring connecting column. The outer ring is slidably mounted on a base. The motor can drive the centrifugal impeller to rotate, thereby causing the centrifugal column to drive the outer ring to periodically reciprocate along the axial direction of the base via the connecting rod.

[0014] The lower end of the outer ring body is fixed on a sliding seat, which is axially slidably mounted on the base, which is placed on the ground.

[0015] The centrifugal impeller described above is mounted on the power unit base via a bracket. The bracket is fixed on the power unit base, and the centrifugal impeller and the bracket are rotatably coupled. The power unit base is fixedly mounted on the base or placed on the ground.

[0016] The aforementioned synchronous traction device includes a main traction rod, an inner ring traction rod, and an outer ring traction rod. The lower end of the main traction rod is hinged to the base. One end of the inner ring traction rod is hinged to one end of the inner ring, and the other end is hinged to the middle of the main traction rod. One end of the outer ring traction rod is hinged to one end of the outer ring, and the other end is hinged to the top of the main traction rod. When the outer ring moves axially, the outer ring traction rod pulls the main traction rod, causing the main traction rod to rotate about its lower end as an axis, which in turn drives the inner ring traction rod to pull the inner ring, causing the outer ring and inner ring to move in the same direction.

[0017] The aforementioned mandrel is a steel shaft.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] This utility model discloses a steel pipe stretching structure for a cold-drawing machine, comprising an inner ring and an outer ring. A synchronous puller synchronizes the movement of both rings. The inner ring stretches the steel pipe, while the outer ring restricts its axial movement. The inner and outer rings are connected by rolling rollers, allowing for disassembly. To change the wall thickness of the stretched steel pipe, simply remove the hinge point between the inner ring and the synchronous puller, pull the inner ring out of the outer ring, and replace it with a new outer ring. This allows the steel pipe stretching structure to adapt to different steel pipe stretching requirements in a cost-effective manner.

[0020] This invention utilizes an inner ring body to compress a steel pipe using extrusion wheel units. The extrusion wheel surface is a concave arc-shaped surface in the center, which conforms to the outer contour curvature of the deformed steel pipe. All extrusion wheels together form an annular cavity. When the steel pipe passes through this cavity, the extrusion wheels compress the outer surface of the pipe, causing the pipe wall to deform inwards. When the inner ring body moves axially, the extrusion wheels and the outer surface of the steel pipe engage in a rolling contact. Therefore, the contact between the extrusion wheels and the steel pipe is a rolling contact, not a friction contact. By compressing the steel pipe with the extrusion wheels, the friction intensity between the inner ring body and the outer surface of the steel pipe is effectively reduced, greatly improving the service life of the inner ring body. Simultaneously, it effectively prevents tensile quality defects in the steel pipe caused by the thermal deformation of the inner ring body. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the external structure of the inner ring of this utility model;

[0022] Figure 2 for Figure 1 AA section view;

[0023] Figure 3 for Figure 2 BB section view;

[0024] Figure 4 A schematic diagram of the outer ring body and the synchronous traction device;

[0025] Figure 5 for Figure 4 CC section view;

[0026] Figure 6 This is a diagram of the internal structure of the outer ring.

[0027] Figure 7 This is a top view of the structure of this utility model;

[0028] Figure 8 This is a diagram showing the working state of this utility model;

[0029] Figure 9 for Figure 8 DD sectional view.

[0030] The attached diagram is labeled as follows: mandrel 1, inner ring body 2, extrusion ring structure 21, inner ring pulley shaft 22, inner ring guide pulley 23, inner ring slide rail 24, extrusion wheel shaft 25, extrusion wheel 26, outer ring body 3, outer ring pulley shaft 31, outer ring guide pulley 32, sliding seat 33, power unit 4, motor 41, centrifugal wheel 42, connecting rod 43, outer ring body connecting column 44, centrifugal column 45, bracket 46, power unit seat 47, synchronous puller 5, main pull rod 51, inner ring body pull rod 52, outer ring body pull rod 53, steel pipe 6, base 7. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of this application clearer, the application is described and illustrated below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application. All other embodiments obtained by those skilled in the art based on the embodiments provided in this application without inventive effort are within the scope of protection of this application.

[0032] Obviously, the accompanying drawings described below are merely some examples or embodiments of this application. Those skilled in the art can apply this application to other similar scenarios based on these drawings without any inventive effort. Furthermore, it is understood that although the efforts made in this development process may be complex and lengthy, for those skilled in the art related to the content disclosed in this application, any changes to design, manufacturing, or production based on the technical content disclosed in this application are merely conventional technical means and should not be construed as insufficient disclosure of the content of this application.

[0033] In this application, the reference to "embodiment" means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment that is mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described in this application may be combined with other embodiments without conflict.

[0034] Unless otherwise defined, the technical or scientific terms used in this application shall have the ordinary meaning understood by one of ordinary skill in the art to which this application pertains. The terms “a,” “an,” “an,” “the,” and similar words used in this application do not indicate quantity limitation and may indicate singular or plural. The terms “comprising,” “including,” “having,” and any variations thereof used in this application are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or device that includes a series of steps or units (elements) is not limited to the listed steps or units, but may also include steps or units not listed, or may include other steps or units inherent to these processes, methods, products, or devices. The terms “connected,” “linked,” “coupled,” and similar words used in this application are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. The terms “multiple” / “several” used in this application refer to two or more. “And / or” describes the relationship between related objects, indicating that three relationships may exist; for example, “A and / or B” can indicate: A alone, A and B simultaneously, or B alone. The character " / " generally indicates that the preceding and following objects are in an "or" relationship. The terms "first," "second," and "third" used in this application are merely to distinguish similar objects and do not represent a specific ordering of the objects.

[0035] This utility model discloses a steel pipe stretching structure for a steel pipe cold drawing machine. The main structure includes a mandrel 1, an inner ring 2, an outer ring 3, a power unit 4, a synchronous traction device 5, and a base 7.

[0036] like Figure 1-3 As shown, the inner ring body 2 mainly includes a compression ring structure 21, an inner ring pulley shaft 22, an inner ring guide pulley 23, and an inner ring slide rail 24. The number of compression ring structures 21 is five, each including a compression wheel shaft 25 and a compression wheel 26. Figure 2 It can be clearly seen that the surface of the extrusion wheel 26 is an arc-shaped surface with a concave center. This arc-shaped surface conforms to the outer contour curvature of the deformed steel pipe 6. A portion of the extrusion ring structure 21 intrudes into the inner ring of the inner ring body 2, giving the inner ring body 2 a ring with a narrowed inner diameter. The normal inner diameter of the inner ring body 2 is larger than the outer diameter of the steel pipe 6, while the inner diameter of the narrowed inner diameter section is smaller than the outer diameter of the steel pipe 6. This causes the steel pipe 6 to be inevitably squeezed and deformed by the narrowed inner diameter section when it passes through the inner ring body 2. Figure 2It can also be seen that the cross-section of the inner diameter reduction section is not a complete circle, which means that the steel pipe 6 is not compressed all around. In actual operation, the two ends of the steel pipe 6 are fixed by a fixing device. The fixing device pushes the steel pipe 6 forward and rotates the steel pipe 6 at a certain angle every certain period of time. During the time period when the fixing device moves and rotates the steel pipe 6, it is exactly the time when the inner ring body 2 moves backward and the inner diameter reduction section is separated from the incompletely compressed steel pipe section. When the inner ring body 2 moves forward again, the steel pipe 6 is already fixed and has completed the rotation. At this time, the steel pipe section that was not originally compressed by the inner diameter reduction section is rotated to the position aligned with the extrusion ring structure 21, and is thus compressed by the inner diameter reduction section. Through the continuous movement and rotation of the steel pipe 6, all positions of the steel pipe 6 passing through the inner ring body 2 will be compressed by the inner diameter reduction section. The diameter of the steel pipe 6 after exiting the inner ring body 2 is reduced to the predetermined value.

[0037] like Figure 1-6 As shown in Figures 8 and 9, in order to facilitate low-cost replacement of the inner ring body 2, the structure of the inner ring body 2 can be made thinner to reduce costs. To ensure the structural strength of the inner ring body 2, an outer ring body 3 is fitted around the outer side of the inner ring body 2. Five inner ring guide pulley units are provided on the outer surface of the inner ring body 2. The inner ring guide pulley units are arranged with equal arc around the outer surface of the inner ring body 2. The inner ring guide pulley unit includes an inner ring pulley shaft 22 and an inner ring guide pulley 23. The inner ring pulley shaft 22 is fixed on the outer surface of the inner ring body 2. The inner ring guide pulley 23 is rotatably mounted on the inner ring pulley shaft 22. The inner ring guide pulley 23 abuts against the inner surface of the outer ring body 3. When the outer ring body 3 moves axially, the inner ring guide pulley 23 rolls on the inner surface of the outer ring body 3, so that the inner ring body 2 and the outer ring body 3 can generate axial relative movement. The outer surface of the inner ring body 2 is provided with five axially extending inner ring slide rails 24, and the inner surface of the outer ring body 3 is provided with five outer ring guide pulley units. Each outer ring guide pulley unit includes an outer ring pulley shaft 31 and an outer ring guide pulley 32. The outer ring pulley shaft 31 is fixed to the inner surface of the outer ring body 3, and the outer ring guide pulley 32 is rotatably mounted on the outer ring pulley shaft 31. The outer ring guide pulley 32 is confined within the inner ring slide rails 24 and can roll within them. Through a total of ten guide wheels (inner and outer ring guide pulley units), close contact between the inner ring body 2 and the outer ring body 3 is achieved. The outer ring body 3 can exert a certain axial pressure on the inner ring body 2, resulting in better structural stability of the inner ring body 2 when extruding the steel pipe 6. Simultaneously, the outer ring body 3 and the inner ring body 2 can also move axially relative to each other, facilitating the removal and replacement of the inner ring body 2 from the outer ring body 3. The lower end of the outer ring body 3 is fixed on a sliding seat 33. The sliding seat 33 is axially slidably mounted on the base 7. The base 7 is placed on the ground. The sliding seat 33 can restrict the outer ring body 3 so that the outer ring body 3 can only move axially. The inner ring body 2 is inside the outer ring body 3. Therefore, the outer ring body 3 can also restrict the inner ring body 2 so that the inner ring body 2 maintains its direction and does not sway left and right.

[0038] The structure of the synchronous traction device 5 is as follows: Figure 4 and 6 As shown, the system includes a main traction rod 51, an inner ring traction rod 52, and an outer ring traction rod 53. The lower end of the main traction rod 51 is hinged to the base 7. One end of the inner ring traction rod 52 is hinged to one end of the inner ring 2, and the other end is hinged to the middle of the main traction rod 51. One end of the outer ring traction rod 53 is hinged to one end of the outer ring 3, and the other end is hinged to the top of the main traction rod 51. When the outer ring 3 moves axially, the outer ring traction rod 53 pulls the main traction rod 51, causing the main traction rod 51 to rotate about its lower end as an axis, which in turn drives the inner ring traction rod 52 to pull the inner ring 2, causing the outer ring 3 and the inner ring 2 to move in the same direction.

[0039] The power unit 4 includes a motor 41, a centrifugal impeller 42, a connecting rod 43, an outer ring connecting column 44, a bracket 46, and a power unit base 47. The centrifugal impeller 42 is mounted on the power unit base 47 via the bracket 46, and the bracket 46 is fixed on the power unit base 47. The centrifugal impeller 42 and the bracket 46 are rotatably coupled. The power unit base 47 is fixedly mounted on the base 7. A centrifugal column 45 is fixed at the non-axial position of the wheel surface of the centrifugal impeller 42. The outer ring connecting column 44 is fixed on the outer surface of the outer ring 3. The motor 41 is connected to the centrifugal impeller 42 for transmission. One end of the connecting rod 43 is hinged to the centrifugal column 45, and the other end is hinged to the outer ring connecting column 44. The outer ring 3 is slidably mounted on the base 7. The motor 41 can drive the centrifugal impeller 42 to rotate, thereby causing the centrifugal column 45 to drive the outer ring 3 to periodically reciprocate along the axial direction of the base 7 via the connecting rod 43. The outer ring 3 drives the outer ring pull rod 53 to move back and forth. The outer ring pull rod 53 pulls the main pull rod 51, causing the main pull rod 51 to rotate around its lower end as an axis. This, in turn, drives the inner ring pull rod 52 to pull the inner ring 2, causing the outer ring 3 and the inner ring 2 to move in the same direction.

[0040] When using the steel pipe stretching structure of the cold drawing machine of this utility model, the state is as follows: Figure 7-9 As shown in the attached diagram, with the left side of the diagram as the front and the right side as the rear, the process of stretching steel pipe 6 is explained.

[0041] Step 1: Insert the rear end of the steel pipe 6 into the inner ring 2, while the steel pipe 6 is also threaded onto the mandrel 1, fix the front end of the steel pipe 6, and start the motor 41.

[0042] Step 2: The centrifugal rotor 42 drives the outer ring 3 forward via the connecting rod 43. The outer ring 3 drives the inner ring 2 forward via the synchronous puller 5. The extrusion ring structure 21 extrudes the outer surface of the rear end of the steel pipe 6, while the mandrel 1 shapes the inner surface of the steel pipe 6. The diameter of the rear end of the steel pipe 6 decreases and becomes thinner.

[0043] Step 3: The centrifugal impeller 42 continues to rotate, and the centrifugal impeller 42 drives the outer ring 3 and the inner ring 2 to move backward, the steel pipe 6 moves backward by one end, and then rotates 36°;

[0044] By repeatedly performing steps 2 and 3, the steel pipe 6 will continue to move backward, and the steel pipe 6 that has moved out from the rear end of the inner ring body 2 will have been squeezed and stretched.

[0045] The above are merely preferred embodiments of this utility model. The protection scope of this utility model is not limited to the above embodiments. All technical solutions falling within the scope of this utility model's concept are within its protection scope. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principle of this utility model should be considered within its protection scope.

Claims

1. A steel pipe stretching structure for a cold drawing machine, characterized in that: The device includes a mandrel (1), an inner ring body (2), an outer ring body (3), a power unit (4), and a synchronous puller (5). The mandrel (1), inner ring body (2), and outer ring body (3) are coaxially arranged. The mandrel (1) passes through the inner side of the inner ring body (2), and the outer ring body (3) is fitted around the outer side of the inner ring body (2), with the inner side of the outer ring body (3) abutting against the outer side of the inner ring body (2). A steel pipe (6) passes through the inner side of the inner ring body (2) and is coaxially arranged with the mandrel (1). The mandrel (1) passes through the inner cavity of the steel pipe (6). The inner side of the inner ring body (2) is provided with a compression ring structure (21), which gives the inner ring body (2) a certain shape. There is an inner diameter reduction section, the inner diameter of which is smaller than the outer diameter of the steel pipe (6), so that the steel pipe (6) is squeezed in the inner diameter reduction section. The inner side of the steel pipe (6) at the inner diameter reduction section abuts against the mandrel (1), and the outer side abuts against the extrusion ring structure (21). The synchronous puller (5) connects the inner ring body (2) and the outer ring body (3) at the same time, so that the inner ring body (2) and the outer ring body (3) are positioned and connected. The power device (4) is connected to the outer ring body (3) or the synchronous puller (5). The power device (4) is used to pull the inner ring body (2) and the outer ring body (3) to move axially synchronously, so as to change the position of the inner diameter reduction section on the steel pipe (6).

2. The steel pipe stretching structure for a cold drawing machine according to claim 1, characterized in that: The outer surface of the inner ring body (2) is provided with a plurality of inner ring guide pulley units. The inner ring guide pulley units are arranged with equal arc around the outer surface of the inner ring body (2). The inner ring guide pulley unit includes an inner ring pulley shaft (22) and an inner ring guide pulley (23). The inner ring pulley shaft (22) is fixed on the outer surface of the inner ring body (2). The inner ring guide pulley (23) is rotatably mounted on the inner ring pulley shaft (22). The inner ring guide pulley (23) abuts against the inner surface of the outer ring body (3). When the outer ring body (3) moves axially, the inner ring guide pulley (23) rolls on the inner surface of the outer ring body (3), so that the inner ring body (2) and the outer ring body (3) can generate axial relative movement.

3. The steel pipe stretching structure for a cold drawing machine according to claim 2, characterized in that: The outer side of the inner ring body (2) is provided with a plurality of axially extending inner ring slide rails (24), and the inner side of the outer ring body (3) is provided with a plurality of outer ring guide pulley units. The outer ring guide pulley unit includes an outer ring pulley shaft (31) and an outer ring guide pulley (32). The outer ring pulley shaft (31) is fixed on the inner surface of the outer ring body (3), and the outer ring guide pulley (32) is rotatably mounted on the outer ring pulley shaft (31). The outer ring guide pulley (32) is limited in the inner ring slide rail (24), and the outer ring guide pulley (32) can roll in the inner ring slide rail (24).

4. The steel pipe stretching structure for a cold drawing machine according to claim 3, characterized in that: The extrusion ring structure (21) consists of several extrusion wheel units. The extrusion wheel units are arranged in equal arcs around the inner side of the inner ring body (2). Each extrusion wheel unit includes an extrusion wheel shaft (25) and an extrusion wheel (26). The extrusion wheel shaft (25) is fixed on the inner surface of the inner ring body (2). The extrusion wheel (26) is rotatably mounted on the extrusion wheel shaft (25). All extrusion wheels (26) together form an annular cavity. The diameter of the annular cavity is smaller than the outer diameter of the steel pipe (6). The steel pipe (6) passes through the annular cavity. The extrusion wheel (26) extrudes the outer side of the steel pipe (6), causing the pipe wall of the steel pipe (6) to move inward and deform. When the inner ring body (2) moves axially, the extrusion wheel (26) rolls with the outer surface of the steel pipe (6).

5. The steel pipe stretching structure for a cold drawing machine according to claim 4, characterized in that: The surface of the extrusion wheel (26) is an arc-shaped surface with a concave center, which is adapted to the outer contour curvature of the deformed steel pipe (6).

6. The steel pipe stretching structure for a cold drawing machine according to claim 5, characterized in that: The power unit (4) includes a motor (41), a centrifugal wheel (42), a connecting rod (43), and an outer ring body connecting column (44). A centrifugal column (45) is fixed at the non-axial part of the wheel surface of the centrifugal wheel (42). The outer ring body connecting column (44) is fixed on the outer surface of the outer ring body (3). The motor (41) is connected to the centrifugal wheel (42) for transmission. One end of the connecting rod (43) is hinged to the centrifugal column (45), and the other end is hinged to the outer ring body connecting column (44). The outer ring body (3) is slidably mounted on a base (7). The motor (41) can drive the centrifugal wheel (42) to rotate, thereby causing the centrifugal column (45) to drive the outer ring body (3) to periodically reciprocate along the axial direction of the base (7) through the connecting rod (43).

7. The steel pipe stretching structure for a cold drawing machine according to claim 6, characterized in that: The lower end of the outer ring body (3) is fixed on a sliding seat (33), which is axially slidably mounted on the base (7), which is placed on the ground.

8. The steel pipe stretching structure for a cold drawing machine according to claim 7, characterized in that: The centrifugal rotor (42) is mounted on the power unit base (47) via a bracket (46). The bracket (46) is fixed on the power unit base (47). The centrifugal rotor (42) and the bracket (46) are rotatably coupled. The power unit base (47) is fixedly mounted on the base (7) or placed on the ground.

9. The steel pipe stretching structure for a cold drawing machine according to claim 8, characterized in that: The synchronous puller (5) includes a main pull rod (51), an inner ring pull rod (52), and an outer ring pull rod (53). The lower end of the main pull rod (51) is hinged to the base (7). One end of the inner ring pull rod (52) is hinged to one end of the inner ring (2), and the other end is hinged to the middle of the main pull rod (51). One end of the outer ring pull rod (53) is hinged to one end of the outer ring (3), and the other end is hinged to the top of the main pull rod (51). When the outer ring (3) moves axially, the outer ring pull rod (53) pulls the main pull rod (51), causing the main pull rod (51) to rotate about its lower end as an axis, thereby driving the inner ring pull rod (52) to pull the inner ring (2), so that the outer ring (3) and the inner ring (2) move in the same direction.

10. The steel pipe stretching structure for a cold drawing machine according to claim 1, characterized in that: The mandrel (1) is a steel shaft.

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