Small-caliber centrifugal nodular cast iron pipe production system and use method thereof

Abstract

The invention relates to a small-caliber centrifugal nodular cast iron pipe production system and a using method thereof, and the small-caliber centrifugal nodular cast iron pipe production system comprises a centrifugal casting system which comprises a pipe die which is a die for forming a nodular cast iron pipe by rotating and centrifuging molten iron to the inner wall and solidifying the molten iron; a driven riding wheel; a driving riding wheel; the more than two pipe dies are arranged side by side, and every two adjacent pipe dies are driven by the same group of driving riding wheels to rotate; the tube drawing system comprises a tube drawing wrench; the tube drawing system further comprises a floating assembly, and the floating assembly comprises a base and a tube drawing head, a slide rail; and the fixing seat is fixedly connected with the pipe drawing pliers and is in sliding connection with the sliding rail, so that the other end, extending into the nodular cast iron pipe, of the pipe drawing pliers obtains the degree of freedom of transverse left-right swing. Automatic correction is achieved when the axis of the formed nodular cast iron pipe deviates, and the pipe drawing success rate is increased.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of centrifugal cast ductile iron pipe production process equipment, and particularly relates to a small-diameter centrifugal cast ductile iron pipe production system and a use method thereof BACKGROUND

[0002] Centrifugal casting is a technology and method for injecting liquid metal into a high-speed rotating mold, making the liquid metal do centrifugal motion to fill the mold and form a casting. Centrifugal motion can make liquid metal fill the mold well in the radial direction and form a casting. The production of ductile iron pipes includes the process of forming a ductile iron pipe with a socket joint by using the centrifugal casting process.

[0003] The inventor found in the prior art that small-diameter (generally referring to ductile iron pipes with a nominal diameter less than DN350) products are generally produced in a single-station production mode during the production process, which is the same as the production of large-diameter pipes. The applicant plans to develop a multi-station side-by-side production organization, such as two centrifuges arranged in parallel, synchronous centrifugal casting, and synchronous use of two pipe pulling mechanisms after molding to achieve efficient multi-station production. In one production technology, two parallel arranged pipe molds share a set of driving idlers, and the idlers inevitably rub against the pipe molds during use, and the degree of friction is uncontrollable. The above problems can cause the position of the pipe mold axis to deviate, especially when using two or more pipe pulling mechanisms, due to the deviation of the pipe mold position, the axes of the two ductile iron pipes after molding may not be consistent in the horizontal direction or include the vertical direction. However, the pipe pulling mechanism is designed without considering wear and tear, so it can extend into the inside of the cast pipe to complete the pipe pulling operation, but the deviation of the position can increase the failure rate. The inventor found during research that if there is a position deviation of about 2mm, when ten groups of cast pipes are pulled, at least one group will have a situation where one of the metal pipes is not successful, and the 10% failure rate is fatal to mass production. This multi-station production actually reduces production efficiency and is not conducive to efficient operation.

[0004] Therefore, there is an urgent need for a device that can adapt to the position deviation of the pipe mold wear and improve the pipe pulling success rate. SUMMARY

[0005] To address the problems in existing technologies, the inventors provided a degree of freedom to the pipe-pulling mechanism at the ends of multiple sets of pipe-pulling wrenches, allowing for offset. This offset occurs after the pipe-pulling wrench ends are in contact with the inner wall of the ductile iron pipe, causing the ends to open and align with the pipe, thus forming a coaxial alignment. However, due to the change in the position of the pipe mold, bending moments are generated at both ends of the pipe-pulling wrench, which reduces the success rate of pipe pulling. The inventors employed a transverse track perpendicular to the axis of the ductile iron pipe, allowing the tail of the pipe-pulling wrench to correct its position during the pulling process. This ensures that the pipe-pulling wrench aligns with the axis of the formed ductile iron pipe during the pulling process, improving the success rate of pipe pulling. The technical solution adopted in this invention is: a small-diameter centrifugal ductile iron pipe production system, comprising: Centrifugal casting system, including: A pipe mold is a mold used to centrifuge molten iron to the inner wall through rotation, which solidifies and forms the ductile iron pipe described above. Two or more driven support rollers support the rotation of the tube mold; Two or more active support rollers drive and support the rotation of the tube mold; Two or more of the aforementioned tube molds are arranged side by side, and two adjacent tube molds are driven to rotate by the same set of the aforementioned active support rollers; And, a tube-pulling system, which is a system for pulling the ductile iron pipe out of the mold after the molten iron has solidified, comprising: A pipe puller is used, with one end inserted into the inside of the ductile iron pipe and the other end spread out and abutting against the inner wall of the ductile iron pipe. The ductile iron pipe is pulled out of the pipe mold by means of friction. The number of tube pullers is the same as the number of tube molds, and they are arranged coaxially. The tube removal system also includes: Floating component, the floating component includes: Base; The slide rail is a track fixed to the base and perpendicular to the axis of the tube mold; The fixed base is fixedly connected to the pipe puller and slidably connected to the slide rail, so that the pipe puller has the freedom to swing laterally left and right relative to the other end that extends into the ductile iron pipe.

[0006] Furthermore, the tube removal system also includes: The positioning arm is a rigid protrusion extending from the fixed base; The positioning clamp is a clamp-shaped component that is fixed to the base and can be controlled to close. A portion of the positioning arm extends into the space where the positioning clamp can close; When the positioning jaw is closed, the positioning arm guides the pipe puller fixed on the fixed base toward or near the axis of the pipe mold.

[0007] Further, The positioning clamp mouth is a pneumatic clamp.

[0008] Further, The slide rail is a plurality of parallel arrangements on the base.

[0009] Further, it also includes: The hanging system provides a degree of freedom in the vertical direction of the pipe pulling forceps, and the hanging system includes: A bracket; A top plate, which is a support body located on the upper side of the pipe pulling system and is fixed by the bracket; A sliding block, which is a component that can move along the movement direction of the pipe pulling forceps and is slidingly connected to the top plate; A sling; The base is suspended below the top plate by means of the sling.

[0010] Further, The number of pipe molds is two, and the two fixing seats are a group of slidingly connected to one base and cooperate with the pipe mold.

[0011] A small-bore centrifugal cast iron pipe production system use method, characterized in that it comprises: The small-bore centrifugal cast iron pipe production system as described above, and the following method: The molten iron enters the pipe mold and is formed by centrifugal force; The pipe pulling system is close to the pipe mold; The positioning clamp mouth is closed, and the positioning arm drives the pipe pulling forceps to move laterally; When the positioning clamp mouth is fully closed, the pipe pulling forceps are located at a position that can be inserted into the pipe mold; The positioning clamp mouth is opened, and the pipe pulling forceps are inserted into the pipe mold; When the positions of adjacent pipe molds are inconsistent, the pipe pulling forceps are opened at the end and abut against the ductile iron pipe, which drives the fixing seat to slide laterally, so that the pulling direction is located on the axis of the ductile iron pipe; Avoiding the pipe pulling forceps deviating from the axis of the ductile iron pipe due to the change of the position of the pipe mold, causing the pipe pulling to fail; The pipe pulling system moves away from the pipe mold; Under the action of the pipe pulling forceps, the ductile iron pipe is pulled out of the pipe mold.

[0012] A small-bore centrifugal cast iron pipe production system use method, characterized in that it comprises: Small caliber centrifugal cast-iron pipe production system and method as described above: The molten iron enters the pipe mold and is cast into a shape by centrifugal force; The pipe pulling system is close to the pipe mold; The pipe pulling tongs are located in a position that can extend into the pipe mold; The pipe pulling tongs enter the pipe mold; The sling is relaxed, so that the base can be inclined when the vertical position of the adjacent pipe mold is inconsistent; The pipe pulling tongs are adjusted to be located on the axis of the ductile iron pipe by means of the inclination of the base and the slide rail; The pipe pulling system moves away from the pipe mold; The ductile iron pipe is pulled out of the pipe mold under the action of the pipe pulling tongs.

[0013] The beneficial effects of the present application relative to the prior art are: 1) the use of a slide rail perpendicular to the axis of the pipe mold provides the pipe pulling tongs with a degree of freedom that can be offset laterally, so that automatic correction can be achieved when the axis of the molded ductile iron pipe is offset, and the success rate of pipe pulling is improved; 2) the use of the positioning arm and the positioning clamp mouth in cooperation can achieve the reset function, so that the pipe pulling tongs cannot enter the inside of the ductile iron pipe; 3) the flexible design of the sling provides a certain degree of freedom in the vertical direction, so that the decrease in the success rate of pipe pulling caused by the offset in the vertical direction is avoided; 4) the use method of the system is proposed. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 The present application is a specific embodiment of the application; Figure 2 The present application is a specific embodiment of the application; Figure 3 The present application is a specific embodiment of the application; Figure 4 The present application is a specific embodiment of the application; Figure 5 The present application is a specific embodiment of the application; Among them, the mark represents: 100-centrifugal casting system; 110-driven idler; 120-driven idler; 130-pipe mold; 200-pipe pulling system; 210-pipe pulling tongs; 220-floating assembly; 221-base; 222-slide rail; 223-fixed seat; 224-positioning arm; 225-positioning clamp mouth; 300-hanging system; 310-bracket; 320-top plate; 330-slide block; 340-sling. DETAILED DESCRIPTION

[0015] The technical solutions in the embodiments are described clearly and completely. Apparently, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. In the description of the present application, it should be understood that the terms "upper", "lower", "front", "back", "left", "right", "top", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship shown in the drawings based on the orientation or positional relationship shown in the drawings, and are only used to facilitate the description of the present application and simplify the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation of the present application.

[0016] To solve the problems in the prior art, the inventors provide freedom of degree to the pipe pulling mechanism at the ends of the multiple sets of pipe pulling tongs 210, allowing the pipe pulling tongs 210 to deviate after the ends of the pipe pulling tongs 210 are attached to the inner wall of the ductile cast iron pipe. The deviation causes the ends of the pipe pulling tongs 210 to be spread apart, which promotes the pipe pulling tongs 210 to form the same axis as the ductile cast iron pipe. However, due to the change in the position of the pipe mold 130, a bending moment is formed at the two ends of the pipe pulling tongs 210, which reduces the success rate of pipe pulling. The inventors use a transverse track perpendicular to the axis of the ductile cast iron pipe, so that the tail of the pipe pulling tongs 210 can be corrected in position during pipe pulling, and the pipe pulling tongs 210 can be aligned with the axis of the formed ductile cast pipe during pipe pulling, thereby improving the success rate of pipe pulling. Please refer to Figures 1 to 5 The present application specifically provides a small-diameter centrifugal ductile cast iron pipe production system, which comprises: A centrifugal casting system 100, the centrifugal casting system 100 described in the present embodiment is a horizontal centrifugal casting commonly used in the industry, which comprises: A pipe mold 130, which is a mold for forming the ductile cast iron pipe by rotating and centrifuging molten iron to the inner wall and solidifying; A driven carrier 110, which is used to support the rotation of the pipe mold 130; A driving carrier 120, which is used to drive and support the rotation of the pipe mold 130; Two or more pipe molds 130 are arranged side by side, and adjacent two pipe molds 130 are driven to rotate by the same set of driving carriers 120; please refer to Figure 1, three groups of supporting wheel structures, the middle group is the driving supporting wheel 120, which realizes the sharing of the two pipe molds 130. It should be noted that, because it is a production process of small-diameter nodular cast iron pipe, the pipe molds 130 are arranged densely, and it is impossible to separately set a group of master and slave supporting wheel groups. Of course, in some embodiments, the diameter of the supporting wheel can be reduced to achieve this purpose. Although the arrangement of the supporting wheel group is limited in this embodiment, if the pipe molds 130 are arranged in parallel, the driving structure of the supporting wheel will have a position offset problem, which is common, and should also belong to the technical solution range described in this embodiment.

[0017] In addition, the pipe pulling system 200 is used to pull out the nodular cast iron pipe from the pipe mold 130 after the molten iron solidifies, which comprises: The pipe pulling tongs 210 enter the inside of the nodular cast iron pipe at one end, the end is expanded and abuts against the inner wall of the nodular cast iron pipe, and the nodular cast iron pipe is pulled out from the pipe mold 130 by means of friction. It should be noted that the structure, driving mode and displacement mode of the pipe pulling tongs 210 belong to the conventional technology in the art, which is not included in the inventive concept, for example, a quick-change core breaking device for pipe pulling tongs CN202121666931.7, pipe pulling tongs for a centrifugal casting machine CN201220377132.2, and a pipe pulling vehicle for a centrifugal casting machine CN201220673855.7. The applicant has developed many structures and forms of pipe pulling tongs 210, which will not be described in detail in this embodiment.

[0018] The pipe pulling tongs 210 are coaxially arranged with the pipe mold 130; The pipe pulling system 200, please refer to Figure 2 Further comprising: The floating assembly 220 comprises: The base 221; The slide rail 222 is fixed to the base 221 and perpendicular to the axis of the pipe mold 130. The number of slide rails 222 can be one or several, which is to meet the horizontal position of the fixing seat 223 and also to provide a limit for the pipe pulling action.

[0019] The fixing seat 223 is fixedly connected with the pipe pulling tongs 210 and slidably connected with the slide rail 222, so that the pipe pulling tongs 210 can swing left and right relative to the other end inserted into the inside of the nodular cast iron pipe.

[0020] In other embodiments, in order to ensure that the pipe pulling tongs 210 can smoothly enter the inner wall of the nodular cast iron pipe, preferably, the pipe pulling system 200 further comprises: The positioning arm 224 is a rigid protrusion extending from the fixing seat 223; The positioning clamp 225 is a clamp-shaped component that is fixed to the base 221 and can be controlled to close. A portion of the positioning arm 224 extends into the space where the positioning clamp 225 can be closed; When the positioning jaw 225 is closed, the positioning arm 224 guides the pipe puller 210, which is fixed on the fixing base 223, toward or near the axis of the pipe mold 130. This embodiment designs a component that achieves positioning through clamping. When the clamping position is preset, the pipe puller 210 is thrust into the inside of the ductile iron pipe.

[0021] In some embodiments, preferably, the positioning gripper 225 is a pneumatic gripper.

[0022] In other embodiments, in order to improve the limiting rigidity of the tube pulling action, Multiple slide rails 222 are arranged in parallel on the base 221. (See also...) Figure 2 In this embodiment, there are two slide rails. The slide rail 222 can also be understood as a linear guide rail.

[0023] In other embodiments, to increase the degree of freedom in the vertical direction, the following additional features are included: The hanging system 300 is a component that provides a degree of freedom in the vertical direction for the tube puller 210, and the hanging system 300 includes: Bracket 310; The top plate 320 is a support located on the upper side of the tube pulling system 200 and fixed by the bracket 310; The slider 330 is a component that is slidably connected to the top plate 320 and can move along the direction of movement of the tube puller 210; Sling 340; The base 221 is suspended from the top plate 320 by the sling 340. It should be noted that in this embodiment, a rotation axis is provided between the base 221 and the drive mechanism (not shown) at the position of the inclined axis of the base 221 to ensure that the base 221 can rotate. This rotation axis is not described in the accompanying drawings, but those skilled in the art can implement it using the description of this embodiment.

[0024] In some embodiments, preferably There are two tube molds 130, and the two fixing seats 223 are slidably connected to one base 221 and cooperate with the tube mold 130. Please refer to [link / reference]. Figure 5Under the concept of the present application, the number of pipe molds 130 can be multiple groups, which can meet the setting of the horizontal degree of freedom and improve the success rate of pipe pulling. However, it should be noted that if it is the vertical degree of freedom, the number of settings needs to be small, or multiple groups are segmented, which can meet the use purpose.

[0025] A small-caliber centrifugal cast ductile iron pipe production system and a method of using the same are provided. A small-caliber centrifugal cast ductile iron pipe production system and a method of using the same are provided. The molten iron enters the pipe mold 130 and is formed by centrifugal casting; The pipe pulling system 200 is close to the pipe mold 130; The positioning clamp 225 is closed to clamp the positioning arm 224 to drive the pipe pulling forceps 210 to move laterally; When the positioning clamp 225 is fully closed, the pipe pulling forceps 210 are located at a position where they can be inserted into the pipe mold 130; The positioning clamp 225 is opened, and the pipe pulling forceps 210 are inserted into the pipe mold 130; When the positions of adjacent pipe molds 130 are inconsistent, the pipe pulling forceps 210 are opened at the end to abut against the ductile iron pipe, which drives the fixed seat 223 to slide laterally, so that the pulling direction is located on the axis of the ductile iron pipe; The pipe pulling forceps 210 are prevented from deviating from the axis of the ductile iron pipe due to the change in the position of the pipe mold 130, which causes the pipe pulling to fail; The pipe pulling system 200 moves away from the pipe mold 130; The ductile iron pipe is pulled out of the pipe mold 130 under the action of the pipe pulling forceps 210.

[0026] A method of using a small-caliber centrifugal cast ductile iron pipe production system is provided. A small-caliber centrifugal cast ductile iron pipe production system and a method of using the same are provided. The molten iron enters the pipe mold 130 and is formed by centrifugal casting; The pipe pulling system 200 is close to the pipe mold 130; The pipe pulling forceps 210 are located at a position where they can be inserted into the pipe mold 130; The pipe pulling forceps 210 are inserted into the pipe mold 130; The sling 340 is loosened, so that the base 221 can be inclined when the positions of adjacent pipe molds 130 are inconsistent in the vertical direction. The pipe pulling forceps 210 are adjusted to be on the axis of the ductile cast iron pipe by the inclination of the base 221 and the slide rail 222; The pipe pulling system 200 moves away from the pipe mold 130; The ductile cast iron pipe is pulled out of the pipe mold 130 under the driving of the pipe pulling forceps 210.

[0027] In specific operation: the centrifugal casting system 100 centrifugally casts the ductile cast iron pipe, which needs to be pulled out of the pipe mold 130. The pipe pulling system 200 is driven to make the pipe pulling forceps 210 close to the end of the spout side of the ductile cast iron pipe. In order to ensure smooth entry, the positioning clamp mouth 225 is first closed to drive the fixed seat 223 to slide on the slide rail 222, and the pipe pulling system 200 is continuously driven to make the pipe pulling forceps 210 enter the inside of the ductile cast iron pipe. The end of the pipe pulling forceps 210 is expanded and abuts against the inner wall of the ductile cast iron pipe. If the center positions of the two pipe molds 130, i.e. the axial positions of the two ductile cast iron pipes, are not on the same horizontal plane, the end of the pipe pulling forceps 210 will tend to be on the same axis as the ductile cast iron pipe in the abutting process. At this time, because the fixed seat 223 is on the slide rail 222, it has the freedom to move horizontally, so the pipe pulling forceps 210 can achieve the purpose of being on the same axis as the ductile cast iron pipe by the abutting force. The pipe pulling system 200 moves away from the pipe mold 130 to pull the ductile cast iron pipe out of the pipe mold 130. In other embodiments or the same embodiment containing the hanging system 300, the base 221 can be deflected, and the slack of the sling 340 no longer limits the position of the base 221. In the abutting process of the end of the pipe pulling forceps 210, the end of the pipe pulling forceps 210 will also have a tendency to adjust the position to achieve the purpose of being on the same axis as the ductile cast iron pipe. In the case of being on the same axis, the success rate of pipe pulling can be improved, and the problem of pipe bending caused by torque or even successful pipe pulling can be avoided.

[0028] The above merely describes the preferred embodiments of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art can make equivalent replacements or changes to the technical solutions and the inventive concept of the present application within the technical scope disclosed by the present application, which should be covered by the protection scope of the present application.

Claims

1. A small-bore centrifugally cast ductile iron pipe production system, characterized by, Comprise: A centrifugal casting system (100), comprising: Pipe molds (130) as molds for forming said ductile cast iron pipes by centrifuging molten iron to inner walls and solidifying; Driven idlers (110) for supporting rotation of said pipe molds (130); Driving idlers (120) for driving and supporting rotation of said pipe molds (130); Two or more of said pipe molds (130) are arranged side by side, and two adjacent said pipe molds (130) are driven to rotate by the same set of said driving idlers (120); And a pipe pulling system (200) for pulling out said ductile cast iron pipes from said pipe molds (130) after solidification of said molten iron, comprising: Pipe pulling tongs (210) for entering into the interior of said ductile cast iron pipes, and for supporting and abutting against the inner walls of said ductile cast iron pipes at the end portions thereof, and for pulling out said ductile cast iron pipes from said pipe molds (130) by means of friction; The number of said pipe pulling tongs (210) is consistent with that of said pipe molds (130), and said pipe pulling tongs (210) are coaxially arranged; Said pipe pulling system (200) further comprises: A floating assembly (220), said floating assembly (220) comprising: A base (221); A slide rail (222) as a track fixed to said base (221) and perpendicular to the axis of said pipe molds (130); A fixing seat (223) fixedly connected with said pipe pulling tongs (210) and slidably connected with said slide rail (222), so that said pipe pulling tongs (210) have a freedom degree of swinging left and right relative to the other end portion extending into the interior of said ductile cast iron pipes.

2. The small diameter centrifugally cast ductile iron pipe production system according to claim 1, characterized in that, Said pipe pulling system (200) further comprises: A positioning arm (224) as a rigid protrusion extending from said fixing seat (223); A positioning clamp (225) as a clamp-shaped assembly fixed to said base (221) and capable of being controlled to be closed; A part of said positioning arm (224) extends into the space capable of being closed by said positioning clamp (225); When said positioning clamp (225) is closed, said pipe pulling tongs (210) fixed to said fixing seat (223) are guided by means of said positioning arm (224) to be directed to or adjacent to the position of the axis of said pipe molds (130).

3. The small-diameter centrifugal ductile cast iron pipe production system according to claim 1, wherein: Said positioning clamp (225) is a pneumatic clamp.

4. The small-diameter centrifugal ductile cast iron pipe production system according to claim 1, wherein: Said slide rail (222) is in multiple and arranged in parallel on said base (221).

5. The small diameter centrifugally cast ductile iron pipe production system according to claim 1, wherein, Further comprising: A hanging system (300) for providing a freedom degree in the vertical direction of said pipe pulling tongs (210), said hanging system (300) comprising: A support (310); A top plate (320) as a support body fixed by said support (310) and located on the upper side of said pipe pulling system (200); A sliding block (330) as a component slidably connected to said top plate (320) and capable of moving along the movement direction of said pipe pulling tongs (210); A sling (340); Said base (221) is hung below said top plate (320) of said top plate (320) by means of said sling (340).

6. The production system of small-bore centrifugal cast-iron pipe according to claim 1, wherein the number of pipe molds (130) is two, and two fixed seats (223) are a group of slidingly connected to one base (221) and matched with the pipe molds (130). The method comprises:

7. A method of using a small bore centrifugally cast ductile iron pipe production system, characterized by, The molten iron enters the pipe molds (130) and is formed by centrifugal casting; The pipe pulling system (200) is close to the pipe molds (130); The positioning clamping jaws (225) are closed to clamp the positioning arms (224) to drive the pipe pulling tongs (210) to move laterally; When the positioning clamping jaws (225) are fully closed, the pipe pulling tongs (210) are located at a position capable of extending into the pipe molds (130); The positioning clamping jaws (225) are opened, and the pipe pulling tongs (210) extend into the pipe molds (130); When the positions of adjacent pipe molds (130) are inconsistent, the pipe pulling tongs (210) are opened at the end to abut against the ductile cast-iron pipe, which drives the fixed seats (223) to slide laterally so that the pulling direction is on the axis of the ductile cast-iron pipe; The pipe pulling tongs (210) are prevented from deviating from the axis of the ductile cast-iron pipe due to the change in the positions of the pipe molds (130), which causes the pipe pulling to fail; The pipe pulling system (200) moves away from the pipe molds (130); The ductile cast-iron pipe is pulled out of the pipe molds (130) under the driving of the pipe pulling tongs (210). The method comprises: The production system of small-bore centrifugal cast-iron pipe according to claim 5, wherein the method comprises:

8. A method of using a small bore centrifugally cast ductile iron pipe production system, characterized by, The molten iron enters the pipe molds (130) and is formed by centrifugal casting; The pipe pulling system (200) is close to the pipe molds (130); The pipe pulling tongs (210) are located at a position capable of extending into the pipe molds (130); The pipe pulling tongs (210) extend into the pipe molds (130); The lifting ropes (340) are loosened, so that the base (221) can be inclined when the positions of adjacent pipe molds (130) are inconsistent in the vertical direction; The pipe pulling tongs (210) are adjusted to be on the axis of the ductile cast-iron pipe by means of the inclination of the base (221) and the sliding rails (222); The pipe pulling system (200) moves away from the pipe molds (130); The ductile cast-iron pipe is pulled out of the pipe molds (130) under the driving of the pipe pulling tongs (210). ​ ​

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