A mandrel for a non-carbon steel pipe bender

Abstract

This invention discloses a mandrel for a non-carbon steel pipe bending machine, comprising a mandrel rod and a mandrel head structure. The mandrel rod has a mandrel head structure connected to its end. The invention also includes an assembly structure for quick connection of the mandrel head structure and the mandrel rod, comprising a locking connector and a fastening bolt. The locking connector has a first ball joint groove at one end for inserting a universal ball joint and a threaded groove at the other end. The mandrel rod has an insertion groove at its end for inserting and fixing the locking connector. The fastening bolt engages with the threaded groove to fix the locking connector to the mandrel rod. The mandrel head structure includes two mandrel head mounting blocks. The movable mounting blocks can be moved axially relative to the fixed mounting blocks to adjust their position, thereby changing the thickness of the mandrel head. This invention provides a non-carbon steel pipe bending machine mandrel with two mounting blocks that can change the thickness of the mandrel head, thus adapting to a series of pipe bending requirements. Furthermore, by adjusting the mandrel head thickness, optimal bending quality can be achieved, facilitating improved product quality.

Description

Technical Field

[0001] This invention relates to the field of anti-wrinkle mandrels for pipe bending, specifically to a non-carbon steel pipe bending machine mandrel. Background Technology

[0002] With the widespread application of CNC pipe bending technology in air conditioning, automobiles, aviation, shipbuilding and other fields, pipe bending plays an increasingly important role in industrial development. Therefore, the quality and performance of pipe bending directly affect the structural performance of industrial products. However, many defects can occur during the pipe bending process, mainly including bending cracks, flattening, tearing and wrinkling.

[0003] Sand filling is a traditional method to solve the problem of pipe deformation. Now, the design and application of mandrels have reasonably solved the problems that arise in bending forming. The mandrel is an important component of CNC bending forming process, and its design and process parameters have a significant impact on the quality of the pipe.

[0004] When bending thin-walled or small-diameter pipes, the ball joints of a flexible mandrel can adapt to different bending diameter requirements, providing better support than rigid mandrels, but the manufacturing process is also more complex. For example, patent document CN 103056221 B discloses a flexible pipe bending mold with a ball-and-socket joint structure, characterized in that: one end of the mandrel body is connected to the pull rod of a CNC pipe bending machine, the front end of the inner ball joint is inserted into the mandrel body and the other end is fixedly connected to the mandrel body, the rear end of the inner ball joint has a spherical groove, the front end of the inner and outer ball joints are spherical protrusions and the rear end are spherical grooves, the outer ball joint is annularly fitted on the outer layer of the inner and outer ball joints, the front end of the outer ball is a spherical protrusion and the rear end is solid, the two inner and outer ball joints are interlocked, the spherical protrusion at the front end of the first inner and outer ball joint is movably connected by embedding into the spherical groove at the rear end of the inner ball joint, and the outer ball is movably connected by embedding into the rear end of the last inner and outer ball joint. This flexible pipe bending mold achieves the requirement of producing thin-walled stainless steel pipes using only a regular pipe bending machine, thanks to its flexible and movable structure. This saves a significant amount of equipment costs and shortens the trial production cycle.

[0005] However, its outer ball joint (mandrel) is a fixed structure, and its thickness 's' cannot be changed. Among the mandrel parameters, the mandrel thickness 's' has a significant impact on the formation of the pipe. When 's' is small, the connection between the mandrel and the next mandrel is unstable, affecting the overall forming performance of the mandrel. When 's' is large, the mandrel cannot provide sufficient support for the inner wall of the pipe. Therefore, adjusting the appropriate mandrel thickness is a key factor in achieving the desired bending effect when facing different bending angles. Secondly, during the bending process, strong sliding friction is generated between the mandrel and the inner wall of the pipe. The greater the friction, the greater the tensile stress on the outer wall of the bent pipe, making it very easy for the outer wall of the bent pipe to be stretched and cracked. Similarly, the side wall of the inner side of the bent pipe is subjected to compressive stress, causing the pipe wall to thicken. The sliding friction between the mandrel and the inner side can also easily cause uneven thickness increase during the formation of the inner side, thus causing wrinkles.

[0006] In view of the above, it is necessary to propose a non-carbon steel pipe bending mandrel to solve the above problems. Summary of the Invention

[0007] The purpose of this invention is to solve the above-mentioned technical problems by providing a non-carbon steel pipe bending mandrel.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: a non-carbon steel pipe bending machine mandrel, comprising a mandrel rod and a mandrel head structure, wherein the mandrel rod is connected to the end of the mandrel head structure, and further comprising an assembly structure for quick connection of the mandrel head structure and the mandrel rod, wherein the assembly structure comprises a locking connector and a fastening bolt, wherein one end of the locking connector is provided with a first ball joint groove for inserting a universal ball joint and the other end is provided with a threaded groove, wherein the end of the mandrel rod is provided with an insertion groove for inserting and fixing the locking connector, and the fastening bolt cooperates with the threaded groove to fix the locking connector on the mandrel rod, wherein the locking connector is formed by splicing two semi-cylindrical locking halves;

[0009] The core structure includes two core mounting blocks, one of which is a fixed mounting block and the other is a movable mounting block. The movable mounting block moves axially relative to the fixed mounting block to adjust its position, thereby changing the thickness of the core.

[0010] Furthermore, one end of the mandrel is provided with a pull rod connecting groove, and the pull rod connecting groove is provided with a pull rod connecting thread; the bottom of the pull rod connecting groove is provided with a bolt groove, and the bolt groove is axially connected to the insertion groove. The fastening bolt is inserted from the bolt groove side and threadedly connected to the locking connector in the insertion groove to fix it.

[0011] Furthermore, the core head structure includes a movable core head and an axis length adjustment part;

[0012] The shaft length adjustment part includes an external threaded bushing and a universal ball joint. One end of the external threaded bushing is provided with an internal threaded hole and the other end is provided with a second ball joint groove. The universal ball joint includes a threaded rod and a universal ball joint. One end of the threaded rod is fixedly provided with a universal ball joint. The threaded rod is threaded into the internal threaded hole. The second ball joint groove is used for connecting multiple core head structures end to end in sequence.

[0013] The movable core head includes two core head mounting blocks, which are disposed on the outer threaded bushing. The core head mounting block farther from the universal ball joint is a fixed mounting block, and the core head mounting block closer to the universal ball joint is a movable mounting block. The fixed mounting block is fixedly connected to one end of the outer threaded bushing where the second ball joint groove is located. The movable mounting block is slidably disposed on the outer threaded bushing. The outer wall of the outer threaded bushing is provided with multiple guide grooves along the axial direction. The movable mounting block is provided with a first sleeve hole at its center. A guide block is fixedly disposed in the first sleeve hole. The guide block is slidably placed in the guide groove. The movement of the movable mounting block is achieved by the cooperation of the guide block and the guide groove.

[0014] Furthermore, it also includes a positioning mechanism for the movable mounting block, which includes a first external thread on the outer wall of the outer threaded bushing, a second external thread on the outer wall of the guide block, and a locking nut; when the guide block is placed in the guide groove, the outer wall of the guide block and the outer wall of the outer threaded bushing are both arc-shaped outer walls and can be spliced ​​together to form a complete circle; when the guide block moves in the guide groove, the second external thread and the first external thread are spliced ​​together to form a complete thread for the locking nut to be screwed in.

[0015] Furthermore, the fixed mounting block has a second socket hole at its center, and a square countersunk groove on one side end face of the fixed mounting block. The external threaded bushing passes through the second socket hole, and a square positioning block is provided at one end of the external threaded bushing. The square positioning block cooperates with the square countersunk groove. The external threaded bushing also has a positioning ring groove, and a spring retainer is provided in the positioning ring groove. The spring retainer is fitted against the side wall of the fixed mounting block to limit its movement. The external threaded bushing is divided into two symmetrical half-shafts along the axial direction.

[0016] Furthermore, both the fixed mounting block and the movable mounting block have a disc-shaped structure, and wheel assembly mounting openings are evenly distributed around the perimeter. Each wheel assembly mounting opening is rotatably connected to a side wall roller, and the rotation axes of the side wall rollers on the same core mounting block are set on the same plane.

[0017] Furthermore, the core mounting block is provided with at least four side wall rollers, and the side wall rollers on the fixed mounting block and the movable mounting block are staggered with each other.

[0018] Furthermore, a core head structure is connected to the tail end of the core rod, and the universal ball head of the core head structure is inserted into the first ball head groove to form a spherical fit.

[0019] Furthermore, the tail end of the mandrel is connected to multiple mandrel head structures, and two mandrel head structures are connected by a universal ball joint inserted into a second ball joint groove to form a spherical fit.

[0020] Compared with the prior art, the beneficial effects of the present invention are:

[0021] 1. The present invention provides a non-carbon steel pipe bending machine mandrel with two mounting blocks that can change the thickness of the mandrel, thereby adapting to a series of pipe bending requirements with different requirements, and achieving the best bending quality by adjusting the thickness of the mandrel, which facilitates the improvement of product quality.

[0022] 2. By connecting the universal ball joint to the external threaded bushing, the axial length of the mandrel structure can be changed, thereby facilitating the adjustment of the distance between the two mandrel structures or between the mandrel rod and the first mandrel structure. By adjusting the two parameters, the center distance P and the thickness s of the mandrel, various pipe bending requirements can be met.

[0023] 3. The side rollers installed around the mandrel mounting block can change the sliding contact between the mandrel and the inner wall of the pipe to a rolling contact when bending the pipe, thereby greatly reducing frictional resistance and avoiding scratches on the inner wall of the pipe during bending, thus improving the quality of the inner wall of the pipe during bending. Attached Figure Description

[0024] Figure 1 An isometric view of a mandrel with a mandrel head structure for a non-carbon steel pipe bending machine according to the present invention;

[0025] Figure 2 In this invention Figure 1 A schematic diagram of the longitudinal section;

[0026] Figure 3 In this invention Figure 1 Exploded structural diagram;

[0027] Figure 4 This is a comparison diagram showing how the core head structure adjusts the position of the movable mounting block and the universal ball joint in this invention;

[0028] Figure 5 These are exploded views of the core head structure in this invention from two perspectives;

[0029] Figure 6 This is an isometric view of a non-carbon steel pipe bending machine mandrel with multiple mandrel head structures according to the present invention;

[0030] In the diagram: 1. Mandrel rod; 2. Mandrel head structure; 3. Locking connector; 4. Fastening bolt; 5. First ball joint groove; 6. Universal ball joint; 7. Threaded groove; 8. Insertion groove; 9. Locking half piece; 10. Fixed mounting block; 11. Moving mounting block; 12. Tie rod connecting groove; 13. Bolt groove; 14. External threaded bushing; 15. Universal ball joint; 16. Internal threaded hole; 17. Second ball joint groove; 18. Threaded rod; 19. Guide groove; 20. First socket hole; 21. Guide block; 22. First external thread; 23. Second external thread; 24. Locking nut; 25. Second socket hole; 26. Square countersunk groove; 27. Square positioning block; 28. Positioning ring groove; 29. ​​Spring retainer; 30. Half piece shaft; 31. Wheel assembly mounting port; 32. Side wall roller. Detailed Implementation

[0031] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0032] Example 1:

[0033] A non-carbon steel pipe bending mandrel, such as Figure 1 As shown, it includes a mandrel 1 and a mandrel head structure 2. The mandrel 1 is connected to the end of the mandrel head structure 2. In this embodiment... Figure 1 A core head structure 2 is connected and provided at the tail end of the core rod 1. In other embodiments, the core head structure 2 can also be added, such as... Figure 6 As shown, there are multiple core head structures 2, and the multiple core head structures 2 are connected end to end to form a flexible joint connection. Adjacent core head structures 2 can rotate in all directions, which facilitates the support of the inner wall of the pipe when bending the pipe.

[0034] In this embodiment, the core head structure 2 and the core rod 1 are designed for quick assembly and disassembly. Specifically, the core head structure 2 and the core rod 1 are connected via an assembly structure, such as... Figure 2 , 3 As shown, the assembly structure includes a locking connector 3 and a fastening bolt 4. The locking connector 3 has a first ball joint groove 5 at one end for inserting a universal ball joint 6 and a threaded groove 7 at the other end. The end of the mandrel rod 1 has an insertion groove 8 for inserting and fixing the locking connector 3. The fastening bolt 4 cooperates with the threaded groove 7 to fix the locking connector 3 on the mandrel rod 1. The locking connector 3 is formed by splicing two semi-cylindrical locking halves 9. One end of the mandrel rod 1 has a pull rod connecting groove 12, and the pull rod connecting groove 12 has a pull rod connecting thread. The bottom of the pull rod connecting groove 12 has a bolt groove 13, which is axially connected to the insertion groove 8. The fastening bolt 4 is inserted from the bolt groove 13 side and threadedly connected to the locking connector 3 in the insertion groove 8 to fix it.

[0035] like Figure 3 As shown, a universal ball head 6 for universal connection is provided at the end of the core structure 2. During connection, the universal ball head 6 is installed in the first ball head groove 5 to realize the universal ball movable connection between the core structure 2 and the locking connector 3. The locking connector 3 is then fixed in the core rod 1. Specifically, in this embodiment, the locking connector 3 is composed of two semi-cylindrical locking half pieces 9, which facilitates the insertion of the universal ball head 6 into the locking connector 3. After the universal ball head 6 is inserted, the two locking half pieces 9 are fastened together and then inserted into the insertion groove 8. The insertion groove 8 radially tightens and fixes the two locking half pieces 9. Then, the fastening bolt 4 is inserted into the bolt groove 13 from the pull rod connection groove 12. The locking bolt is screwed into the threaded groove 7 to fix the locking connector 3. This structure is simple and can realize quick installation and disassembly, and is easy to maintain.

[0036] Example 2:

[0037] The core head structure 2 includes two core head mounting blocks, one of which is a fixed mounting block 10 and the other is a movable mounting block 11. The movable mounting block 11 moves axially relative to the fixed mounting block 10 to adjust its position, thereby changing the thickness of the core head. In this embodiment, to change the thickness of the core head, the existing monolithic core head structure 2 is improved into two separate core head mounting blocks, such as... Figure 4 As shown, it is specifically divided into fixed mounting block 10 and movable mounting block 11, as follows: Figure 4 As shown, the upper image shows a wider spacing between the two mandrel mounting blocks, which is equivalent to increasing the thickness of the mandrel; the lower image shows a closer spacing between the two mandrel mounting blocks, which is equivalent to reducing the thickness of the mandrel. By changing the thickness of the mandrel, it can be applied to pipe bending forming for various requirements, and the results are good.

[0038] The core head structure 2 includes a movable core head and an axis length adjustment part; the movable core head is used to adjust the core head thickness, while the axis length adjustment part is used to adjust the core head center distance P;

[0039] The movable core head includes two core head mounting blocks, which are disposed on the outer threaded bushing 14. The core head mounting block farther from the universal ball head 6 is a fixed mounting block 10, and the core head mounting block closer to the universal ball head 6 is a movable mounting block 11. The fixed mounting block 10 is fixedly connected to one end of the outer threaded bushing 14 where the second ball head groove 17 is provided.

[0040] Specifically, such as Figure 4 , 5As shown, the external threaded bushing 14 has a cylindrical structure, with a square positioning block 27 at one end for engaging with a square recess 26 to secure the fixing block 10 to the external threaded bushing 14. The fixing block 10 has a second socket hole 25 at its center, through which the cylindrical end of the external threaded bushing 14 passes. A square recess 26 is provided on one side of the fixing block 10, and the square positioning block 27 mates with the square recess 26. The external threaded bushing 14 also has... There is a positioning ring groove 28. The position of the positioning ring groove 28 needs to be flush with the side of the fixed mounting block 10. A spring retainer 29 is installed in the positioning ring groove 28 so that the spring retainer 29 fits against the side wall of the fixed mounting block 10 to limit its movement. In actual use, after the outer threaded bushing 14 is inserted into the second sleeve hole 25, the contour positioning block is inserted into one side of the fixed mounting block 10, and the other side is secured in the positioning ring groove 28 by the spring retainer 29, so as to connect and fix the outer threaded bushing 14 to the fixed mounting block 10.

[0041] like Figure 4 , 5 As shown, the movable mounting block 11 is slidably disposed on the external threaded bushing 14. The outer wall of the external threaded bushing 14 is provided with multiple guide grooves 19 along the axial direction. In this embodiment, four guide grooves 19 are provided on the circumferential direction of the outer wall of the external threaded bushing 14. In actual use, the number of guide grooves 19 is not limited. The guide grooves 19 are used to guide the movable mounting block 11, limit its stroke, and fix its position. Specifically, the movable mounting block 11 is provided with a first sleeve hole 20 at its center. The movable mounting block 11 is sleeved on the external threaded bushing 14 through the first sleeve hole 20. A guide block 21 is fixedly disposed in the first sleeve hole 20. The position and number of guide blocks 21 are corresponding to the guide grooves 19. The guide blocks 21 are slidably disposed in the guide grooves 19. The movement of the movable mounting block 11 is achieved by the cooperation of the guide blocks 21 and the guide grooves 19. The cooperation between the guide groove 19 and the guide block 21 can guide the movable mounting block 11 and restrict the rotation of the movable mounting block 11, thereby maintaining the relative angle between the movable mounting block 11 and the fixed mounting block 10.

[0042] Furthermore, it also includes a positioning mechanism for the movable mounting block 11. The aforementioned structure can enable the movable mounting block 11 to move relative to the fixed mounting block 10, thereby changing the overall thickness of the core head. The positioning mechanism positions the movable mounting block 11, thereby ensuring that the position between the movable mounting block 11 and the fixed mounting block 10 will not change unexpectedly during use.

[0043] Specifically, such as Figure 5As shown, the positioning mechanism includes a first external thread 22 on the outer wall of the outer threaded bushing 14, a second external thread 23 on the outer wall of the guide block 21, and a locking nut 24. When the guide block 21 is placed in the guide groove 19, the outer wall of the guide block 21 and the outer wall of the outer threaded bushing 14 are both arc-shaped outer walls and can be spliced ​​together to form a complete circle. When the guide block 21 moves in the guide groove 19, the second external thread 23 and the first external thread 22 are spliced ​​together to form a complete thread for the locking nut 24 to be screwed into. In actual use, when it is necessary to change the position of the movable mounting block 11, first remove the locking nut 24. At this time, the position of the movable mounting block 11 can be moved freely. When it is moved to the predetermined position, screw the locking nut 24 in. At this time, it should be noted that the second external thread 23 should correspond to the thread teeth of the first external thread 22, so as to facilitate the screwing in of the locking nut 24 and simultaneously engage the first external thread 22 and the second external thread 23. Then continue to tighten the locking nut 24 and press it on the movable mounting block 11. In this way, the position of the movable mounting block 11 can be changed and locked, thereby changing the thickness of the core structure 2.

[0044] Since the core structure 2 of this device can be interconnected, as an improvement, the external threaded bushing 14 is axially divided into two symmetrical half-shafts 30; as shown... Figure 5 As shown, the two half-shafts 30 can be separated into two pieces when disassembled, so that the universal ball joints 6 in other mandrel structures 2 can be installed in the second ball joint groove 17 when separated. Then, the two half-shafts 30 are combined and inserted into the fixed mounting block 10, and then the spring retainer 29 is snapped in, thereby realizing the connection and extension of multiple mandrel structures 2. This embodiment can easily increase or decrease the number of mandrel structures 2, which is convenient to increase or decrease the number of mandrels according to the processing requirements in the actual pipe bending process.

[0045] Example 3:

[0046] The shaft length adjustment part includes an external threaded bushing 14 and a universal ball joint 15. One end of the external threaded bushing 14 has an internal threaded hole 16, and the other end has a second ball joint groove 17. The universal ball joint 15 includes a threaded rod 18 and a universal ball joint 6. One end of the threaded rod 18 is fixedly provided with the universal ball joint 6, and the threaded rod 18 is threaded into the internal threaded hole 16. The second ball joint groove 17 is used for sequentially connecting multiple core head structures 2 end to end. The shaft length adjustment part can change the axial length of the core head structure 2, thereby changing the spacing between two adjacent core head structures 2. Specifically, for example... Figure 4 , 5As shown, the universal ball joint 15 is screwed into the internal threaded hole 16 via the threaded rod 18. Since it is a threaded connection, the extension length of the universal ball joint 15 can be changed by rotation, thereby changing the distance between two adjacent core structures 2. In actual use, a locking structure for the universal ball joint 15 can also be added to prevent the extension or shortening caused by the automatic rotation of the universal ball joint 15 during use.

[0047] Example 4:

[0048] Both the fixed mounting block 10 and the movable mounting block 11 are disc-shaped structures with wheel mounting openings 31 evenly distributed around them. Each wheel mounting opening 31 is rotatably connected to a sidewall roller 32. The sidewall roller 32 has an oval shape with a large radius in the middle and gradually decreasing radii at both ends, so that its outer contour forms a circle with the outer contour of the mandrel mounting block. Furthermore, the outer contour of the sidewall roller 32 is slightly larger than that of the mandrel mounting block. Therefore, during use, the mandrel mounting block contacts the inner wall of the pipe through the sidewall roller 32, changing sliding friction into rolling friction. This effectively avoids scratches on the inner wall surface when the pipe is bent, improving product quality. As shown in the figure, the rotation axes of the sidewall rollers 32 on the same mandrel mounting block are set on the same plane. The mandrel mounting block is provided with at least four side wall rollers 32, and the side wall rollers 32 on the fixed mounting block 10 and the movable mounting block 11 are staggered with each other; the guide groove 19 and the guide block 21 are used to keep the side wall rollers 32 on the two mandrel mounting blocks staggered in position during the movement and change of spacing. The staggered position of the side wall rollers 32 on the two mandrel mounting blocks can form full rolling contact with the inner wall of the pipe surface, thereby effectively reducing frictional resistance and improving the forming effect.

[0049] Furthermore, a core head structure 2 is connected to the tail end of the core rod 1, and the universal ball head 6 of the core head structure 2 is inserted into the first ball head groove 5 to form a spherical fit. For example... Figure 1 When a core head structure 2 is set, the universal ball head 6 of the core head structure 2 is connected to the locking connector 3.

[0050] In other embodiments, the tail end of the mandrel 1 is connected to a plurality of mandrel head structures 2, such as... Figure 6 As shown, the two core head structures 2 are connected by a universal ball joint 6 inserted into the second ball joint groove 17 to form a spherical fit. The first core head structure 2 is connected in the locking connector 3, and the other core head structures 2 are connected end to end in sequence. The universal ball joint 6 of the next core head structure 2 is inserted into the second ball joint groove 17 of the previous core head structure 2, thereby realizing a structure in which multiple core head structures 2 are connected by universal ball joints.

[0051] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A mandrel for a non-carbon steel pipe bending machine, comprising a mandrel rod (1) and a mandrel head structure (2), wherein the mandrel rod (1) is provided with a mandrel head structure (2) at its end, characterized in that, It also includes an assembly structure for quick connection of the core head structure (2) and the core rod (1). The assembly structure includes a locking connector (3) and a fastening bolt (4). The locking connector (3) has a first ball head groove (5) at one end for the universal ball head (6) to be inserted and a threaded groove (7) at the other end. The core rod (1) has an insertion groove (8) at the end for the locking connector (3) to be inserted and fixed. The fastening bolt (4) and the threaded groove (7) cooperate to fix the locking connector (3) on the core rod (1). The locking connector (3) is formed by splicing two semi-cylindrical locking halves (9). The core structure (2) includes two core mounting blocks, one of which is a fixed mounting block (10) and the other is a movable mounting block (11). The movable mounting block (11) moves axially relative to the fixed mounting block (10) to adjust its position and thus change the thickness of the core. The core head structure (2) includes a movable core head and an axis length adjustment part; The shaft length adjustment part includes an external threaded bushing (14) and a universal ball joint (15). One end of the external threaded bushing (14) is provided with an internal threaded hole (16) and the other end is provided with a second ball head groove (17). The universal ball joint (15) includes a threaded rod (18) and a universal ball head (6). One end of the threaded rod (18) is fixedly provided with a universal ball head (6). The threaded rod (18) is threaded into the internal threaded hole (16). The second ball head groove (17) is used for multiple core head structures (2) to be connected end to end in sequence. The movable core head includes two core head mounting blocks, which are set on the outer threaded bushing (14). The core head mounting block away from the universal ball head (6) is a fixed mounting block (10), and the core head mounting block closer to the universal ball head (6) is a movable mounting block (11). The fixed mounting block (10) is fixedly connected to one end of the outer threaded bushing (14) where the second ball head groove (17) is provided. The movable mounting block (11) is slidably set on the outer threaded bushing (14). The outer wall of the outer threaded bushing (14) is provided with multiple guide grooves (19) along the axial direction. The center of the movable mounting block (11) is provided with a first sleeve hole (20). A guide block (21) is fixedly provided in the first sleeve hole (20). The guide block (21) is slidably placed in the guide groove (19). The movement of the movable mounting block (11) is achieved by the cooperation of the guide block (21) and the guide groove (19). It also includes a positioning mechanism for the movable mounting block (11), which includes a first external thread (22) on the outer wall of the outer threaded bushing (14), a second external thread (23) on the outer wall of the guide block (21), and a locking nut (24); when the guide block (21) is placed in the guide groove (19), the outer wall of the guide block (21) and the outer wall of the outer threaded bushing (14) are both arc-shaped outer walls and can be spliced ​​together to form a complete circle; when the guide block (21) moves in the guide groove (19), the second external thread (23) and the first external thread (22) are spliced ​​together to form a complete thread for the locking nut (24) to be screwed in; The fixed mounting block (10) has a second socket hole (25) at its center. A square groove (26) is provided on one side end face of the fixed mounting block (10). The external threaded bushing (14) is inserted through the second socket hole (25). A square positioning block (27) is provided at one end of the external threaded bushing (14). The square positioning block (27) cooperates with the square groove (26). The external threaded bushing (14) is also provided with a positioning ring groove (28). A spring retainer (29) is provided in the positioning ring groove (28). The spring retainer (29) is fitted to the side wall of the fixed mounting block (10) to limit its movement. The external threaded bushing (14) is divided into two symmetrical half-shafts (30) along the axial direction.

2. The mandrel for a non-carbon steel pipe bending machine according to claim 1, characterized in that, One end of the mandrel rod (1) is provided with a pull rod connecting groove (12), and the pull rod connecting groove (12) is provided with a pull rod connecting thread; the bottom of the pull rod connecting groove (12) is provided with a bolt groove (13), and the bolt groove (13) is axially connected to the insertion groove (8). The fastening bolt (4) is inserted from the bolt groove (13) side and threadedly connected to the locking connector (3) in the insertion groove (8) to fix it.

3. The mandrel for a non-carbon steel pipe bending machine according to claim 1, characterized in that, The fixed mounting block (10) and the movable mounting block (11) are both disc-shaped structures, and wheel assembly mounting ports (31) are evenly distributed around them. Each wheel assembly mounting port (31) is rotatably connected to a side wall roller (32), and the rotating shafts of the side wall rollers (32) on the same core mounting block are set on the same plane.

4. The mandrel for a non-carbon steel pipe bending machine according to claim 3, characterized in that, The core mounting block is provided with at least four side wall rollers (32), and the side wall rollers (32) on the fixed mounting block (10) and the movable mounting block (11) are staggered with each other.

5. The mandrel for a non-carbon steel pipe bending machine according to claim 1, characterized in that, The tail end of the mandrel (1) is connected to a core head structure (2), and the universal ball head (6) of the core head structure (2) is placed into the first ball head groove (5) to form a spherical fit.

6. The mandrel for a non-carbon steel pipe bending machine according to claim 1, characterized in that, The tail end of the mandrel (1) is connected to multiple mandrel structures (2), and two mandrel structures (2) are connected by a universal ball joint (6) inserted into the second ball joint groove (17) to form a spherical fit.

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