Built-in floating punching device for variable cross-section chain link

Abstract

The utility model is applicable to the technical field of chain link processing, and particularly relates to a built-in floating punching device for a variable cross-section chain link, which comprises a lower die holder, an upper die holder is arranged above the lower die holder, a punching cylinder is mounted on the upper surface of the upper die holder, one end of the punching cylinder is provided with a positioning pressing block, and the other end of the punching cylinder is provided with a floating block. A base plate is arranged on the lower surface of the upper die base, a female die base is installed on the surface of the base plate, and a first through hole is formed in the side face of the female die base. According to the built-in floating punching device, the mode that punching is conducted from the inner side of the chain link to the outer side of the chain link through the punching nails is adopted, the inclined limiting structure and the elastic buffering assembly are combined, and on the premise that the integrity of the inner arc structure of the chain link is not damaged, accurate punching of a small end area is achieved.

Description

TECHNICAL FIELD

[0001] The utility model relates to chain link processing technical field, and specifically is a built-in floating punching device for variable cross section chain link. BACKGROUND

[0002] In the chain link manufacturing process, the small end punching as an important link of structure processing, its hole position precision, hole wall smoothness and hole roundness are directly related to the pin shaft assembly accuracy and chain performance. In the traditional process, the punching is usually operated from the outside to the inside of the chain link. Due to the closed U-shaped structure, it is impossible to set a complete concave die or support surface, resulting in unstable support and concentrated punching force in the punching process, and problems such as hole position deviation, punching step and hole deformation often occur. In addition, the punching area is usually the stress concentration area of the chain link. Once the hole type quality is poor, fatigue cracking and early failure in use are easily caused, which seriously affects the stable operation and service life of the chain.

[0003] To solve the above problems, some improvement methods try to improve the punching precision by strengthening the die rigidity and optimizing the punching sequence. However, under the premise of limited inner arc structure of the chain link, it is still difficult to achieve overall support and accurate control of the hole position in the narrow space. Especially in the double-hole chain link structure, it is difficult to quickly and accurately position the workpiece during the second punching, which further affects the punching consistency and efficiency. Therefore, the existing punching device still has the problems of structural limitation and limited application range in adapting to complex U-shaped chain link structure. SUMMARY

[0004] The purpose of the embodiment of the utility model is to provide a built-in floating punching device for variable cross section chain link, aiming at solving the technical problems mentioned in the background art.

[0005] To achieve the above purpose, the utility model provides the following technical scheme:

[0006] A built-in floating punching device for variable cross section chain link, comprising a lower die seat, and an upper die seat is arranged above the lower die seat, a punching cylinder is installed on the upper surface of the upper die seat, and a positioning and pressing block is arranged at one end of the punching cylinder, a backing plate is arranged on the lower surface of the upper die seat, a concave die seat is installed on the surface of the backing plate, and a first through hole is formed in the side surface of the concave die seat;

[0007] A slanting limiting block and a pressing block are arranged on the surface of the lower die seat, a floating punch seat is connected to the outer side of the pressing block, an elastic ring is installed at one end of the floating punch seat, a slanting pushing block is arranged on the side surface of the elastic ring, a punch is installed on the side surface of the slanting pushing block, and a first inclined surface and a second inclined surface are respectively formed in the side surfaces corresponding to the slanting limiting block and the slanting pushing block, and the inclination angles of the first inclined surface and the second inclined surface are the same.

[0008] Further, the first through hole is internally provided with a punching female die, and the surface of the punching female die is provided with a through hole, and the punching pin and the through hole are on the same axis.

[0009] Further, the surface of the female die seat is provided with a second through hole away from the side of the first through hole, and the second through hole is internally provided with a spring, and the inside of the spring is provided with a positioning pin, and the positioning pin and the through hole are on the same axis.

[0010] Further, the surface of the inclined limit block is provided with a third inclined surface.

[0011] Further, the surface of the punching pin is provided with a titanium layer, the elastic ring is made of polyurethane material, and the punching female die is made of hard alloy material.

[0012] Further, the lower surface of the lower die seat is provided with a spring top seat, and the surface of the spring top seat is provided with a top rod, and one end of the top rod away from the spring top seat is connected with one end of the floating punching pin seat.

[0013] A built-in floating punching device for a variable cross-section chain link, the lower surface of the lower die seat is provided with a spring top seat, and the surface of the spring top seat is provided with a top rod, and one end of the top rod away from the spring top seat is connected with one end of the floating punching pin seat.

[0014] A forming process of a variable cross-section chain link, the forming process specifically comprises the following steps:

[0015] S1: punching out a chain link shape and its large end pin shaft hole on a steel plate material to obtain an initial shape chain link material;

[0016] S2: sequentially performing π type cold bending and U type cold bending forming on the initial shape chain link material to make it into an equal cross-section U type bent chain link;

[0017] S3: inductively heating the small end region of the equal cross-section U type bent chain link, and axially hot extruding it in a die to make the thickness of the small end region be 5mm in the punching area, and gradually transition from the region to the same thickness 4.3mm of the large end of the chain link with a slope of 2.7°;

[0018] S4: after the hot extrusion is completed, using the die to keep the U type bent chain link in a hot state to heat shape the U type bent chain link, so that the 90° bending angle arc of the U type part is as small as possible to close to R0, improve the fit of the small end inner circle and the pin shaft and the meshing degree of the outer circle and the sprocket, and ensure that the length of the straight line segment in the width direction of the U type bent chain link is not less than 95%, to obtain a variable cross-section chain link;

[0019] S5: using a built-in floating punching device punching from the inside to the outside to punch the small end region of the variable cross-section chain link.

[0020] Further, the temperature maintained by the mold in the hot shaping process is 450-650 DEG C.

[0021] Further, after the step S5 is completed, the steps of heat treatment, shot blasting treatment and rust-proof treatment on the variable cross-section chain link are further included.

[0022] The built-in floating punching device for the variable cross-section chain link has the following beneficial effects:

[0023] The built-in floating punching device punches the hole from the inside to the outside of the chain link by using the punch, and realizes the accurate punching of the small end region in combination with the inclined limit structure and the elastic buffer assembly without damaging the integrity of the inner arc structure of the chain link. The device can provide complete support for the punching position, effectively prevent the hole wall from collapsing, deviation or punching deviation, and is especially suitable for the machining scene of the chain link workpiece with a closed structure or a deep curved inner cavity. At the same time, the floating punch has self-resetting capability, is suitable for continuous high-frequency operation, has good mold stability and high punching consistency, and improves the overall forming quality and the service life of the mold. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 It is a structural schematic view of a built-in floating punching device for a variable cross-section chain link.

[0025] Figure 2 It is a structural schematic view of a built-in floating punching device for a variable cross-section chain link. Figure 1 It is an enlarged view of A of the built-in floating punching device.

[0026] Figure 3 It is a structural schematic view of a variable cross-section chain link.

[0027] Figure 4 It is a structural schematic view of the variable cross-section chain link and the pin shaft after assembly.

[0028] In the figure: 1, lower die seat; 2, inclined limit block; 3, floating punch seat; 4, backing plate; 5, punching cylinder; 6, upper die seat; 7, concave die seat; 8, chain link workpiece; 9, pressing block; 10, ejector rod; 11, elastic seat; 12, positioning pressing block; 13, inclined limit driving block; 14, spring; 15, positioning pin; 16, punch; 17, elastic ring; 18, punching concave die. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical scheme and advantages of the utility model more clear and obvious, the utility model is further described in detail below by combining with the drawings and examples. It should be understood that the specific examples described here are only used to explain the utility model, and are not used to limit the utility model.

[0030] The specific implementation of this utility model will be described in detail below with reference to specific embodiments.

[0031] like Figures 1-2 As shown in the figure, the present invention provides a built-in floating punching device for variable cross-section chain links, including a lower die base 1, and an upper die base 6 is provided above the lower die base 1. A punching cylinder 5 is installed on the upper surface of the upper die base 6, and a positioning and clamping block 12 is provided at one end of the punching cylinder 5. A pad 4 is provided on the lower surface of the upper die base 6, and a die cavity 7 is installed on the surface of the pad 4. A first through hole is opened on the side of the die cavity 7.

[0032] The surface of the lower die base 1 is provided with a slant limiting block 2 and a clamping block 9, and a floating punch seat 3 is connected to the outer side of the clamping block 9. An elastic ring 17 is installed at one end of the floating punch seat 3, and a slant pushing block 13 is provided on the side of the elastic ring 17. A punch 16 is installed on the side of the slant pushing block 13. The corresponding sides of the slant limiting block 2 and the slant pushing block 13 are respectively provided with a first inclined surface and a second inclined surface, and the inclination angles of the first inclined surface and the second inclined surface are the same. A punching die 18 is installed inside the first through hole, and a through hole is provided on the surface of the punching die 18. The punch 16 and the through hole are on the same axis.

[0033] In one embodiment of this invention, during the axial hot extrusion process, a die extrusion method is used to apply axial pressure to the small end region of the chain link at high temperature to form a predetermined variable cross-sectional thickness structure.

[0034] The built-in floating punching device for variable cross-section chain links, in specific use, realizes the positioning, clamping and punching operations of the chain link workpiece 8 through the cooperation between the lower die base 1 and the upper die base 6.

[0035] Before punching, the chain link workpiece 8 is placed in a preset position between the inclined limit block 2 and the floating punch seat 3, so that the small end area of ​​the chain link workpiece 8 is in contact with the side of the inclined limit block 2 and the floating punch seat 3, and is consistent with the impact direction of the punch 16; at this time, the first inclined surface and the second inclined surface of the inclined push block 13 are in contact with each other, forming an inclined wedge engagement mechanism for changing the impact direction.

[0036] Subsequently, the driving punching cylinder 5 is activated, causing the positioning clamping block 12 connected to one end of it to move downward, so that the chain link workpiece 8 is clamped and fixed to prevent slippage or displacement during the punching process; at the same time, the pad plate 4 located on the lower surface of the upper die base 6 and the die base 7 connected thereto descend, so that the punching die 18 on the die base 7 surrounds the outside of the chain link workpiece 8, forming a complete support structure. The through hole in the punching die 18 is used to provide reverse support force and a chip channel for the punch 16.

[0037] After the chain link workpiece 8 is completely positioned and compressed, the punching cylinder 5 continues to drive the positioning and compressing block 12 to further act, so that the inclined slope pushing block 13 slides downward along the second inclined surface, since the inclined slope pushing block 13 is installed on the floating punch seat 3 through the elastic ring 17, and is elastically compressed after being subjected to the pushing force, and at the same time, the punch 16 is driven to penetrate along the preset axis direction from the inside to the outside of the chain link workpiece 8, and the punching operation is completed through the through hole.

[0038] After the punching is completed, the action force of the punching cylinder 5 is released, the elastic ring 17 is elastically recovered, the inclined slope pushing block 13 and the punch 16 are reset, the floating punch seat 3 returns to the initial position under the action of the ejection structure or the elastic element of the die, and one punching cycle is completed.

[0039] The device sets the built-in punch structure, so that the punch punches from the inside to the outside of the chain link workpiece 8, effectively avoids the defects such as hole wall collapse, punching deviation and step caused by the fact that the inner arc area of the small end of the chain link cannot be supported in the traditional outward punching process, the inclined slope limiting block 2 and the inclined surface matching structure of the inclined slope pushing block 13 are adopted to convert the vertical pressing force into the axial impact force, so that the punching operation in the space structure is realized, the structure is compact, and the force transmission is clear; the floating punch seat 3 and the matched elastic ring 17 can provide flexible recovery capability, so that the punch has the resilience, is suitable for continuous punching operation, improves the punching rhythm and the die life.

[0040] Through the punching device in the embodiment of the utility model, the small end area of the chain link workpiece 8 can obtain complete inner wall support, the punch and the through hole are good in centration, the hole position is high in accuracy, the hole wall is smooth, the hole roundness is improved, and the fitting quality of the hole and the pin shaft is obviously improved, so as to improve the meshing performance and the operation reliability of the whole chain assembly, prolong the chain life and reduce the early failure probability.

[0041] In the embodiment, the concave die seat 7 is provided with a second through hole on the side away from the first through hole, and a spring 14 is installed in the second through hole, and a positioning pin 15 is arranged in the spring 14, and the positioning pin 15 is on the same axis as the through hole.

[0042] Specifically, after the first hole punching operation of the small end area of the chain link workpiece 8 is completed, when the second hole punching of the other side of the same chain link workpiece 8 is prepared, the operator re-clamps the chain link workpiece 8 in the opposite direction, so that the first hole of the chain link workpiece 8 faces the concave die seat 7, and the positioning pin 15 is pushed out along the direction of the second through hole under the elastic force of the spring 14, and the front end is automatically inserted into the first hole of the chain link workpiece 8, so that the rapid hole positioning of the chain link workpiece 8 is completed, the punching position of the second hole is kept coaxial with the first hole, and left-right deviation or spacing error is avoided.

[0043] Through the positioning structure, the process of clamping the chain link workpiece 8 again after turning over can be simplified, the second hole punching deviation problem caused by manual positioning error can be eliminated, the consistency and fitting precision of multi-hole punching can be improved, and the high-quality symmetrical hole punching operation can be completed by cooperating with the built-in floating punching device, thereby further improving the size consistency and assembly performance of the chain link finished product.

[0044] In the embodiment, a third inclined surface is arranged on the surface of the inclined limit block 2. The third inclined surface is used to support the inner wall of the large end of the chain link workpiece 8, so as to enhance the stability of the chain link workpiece 8 in the punching process.

[0045] Specifically, when the chain link workpiece 8 is placed in the punching device, the small end region of the chain link workpiece 8 is matched with the inclined wedge matching structure formed by the first inclined surface and the second inclined surface, and the large end region of the chain link workpiece 8 is matched with the third inclined surface of the inclined limit block 2. Since the inner wall of the large end of the chain link workpiece 8 is usually an arc surface structure, by arranging the third inclined surface matched with the contour, the curved surface matching between the chain link workpiece 8 and the inclined limit block 2 can be realized, so as to provide a supporting and positioning effect for the chain link workpiece 8 in three-dimensional direction.

[0046] The arrangement of the third inclined surface further reduces the overall shaking or tilting of the chain link workpiece 8 when subjected to the punching force, which helps to maintain the stable posture of the workpiece and the accurate punching path, and improves the punching precision, hole position coaxiality and hole wall quality, and is especially suitable for processing chain link structural parts with complex variable cross-section structure and asymmetric shape at both ends.

[0047] In the embodiment, in order to further improve the service life and punching precision of the built-in floating punching device, a titanium layer is arranged on the surface of the punch 16. The titanium layer has high surface hardness and good wear resistance, which can significantly reduce the wear and adhesion of the punch during high-frequency impact, thereby prolonging the service life of the punch and maintaining the sharpness of the punching edge, and improving the hole forming quality.

[0048] The elastic ring 17 is made of polyurethane material. The polyurethane material has excellent elastic recovery performance and fatigue resistance, which can provide effective buffering and rebound support after the punch is stressed, and maintain stable elastic response under high-frequency operation conditions, which helps the punch to accurately return after punching is completed, and ensures the beat consistency of continuous punching process and the reset stability of the die mechanism.

[0049] The punching concave die 18 is made of hard alloy material. The material has very high compressive strength and excellent wear resistance, and is especially suitable for bearing high-strength impact load from the punch. The material can maintain the precision and smoothness of the through hole during long-term use, and prevent problems such as hole position deviation and punch jamming caused by wear of the concave die.

[0050] The reasonable arrangement of the plurality of materials makes the built-in floating punching device have high punching precision and long service life under the working condition of high strength and continuous operation, and effectively improves the machining consistency of the small-end hole of the variable cross-section chain link and the overall assembly quality of the chain assembly.

[0051] In the embodiment, the lower surface of the lower die seat 1 is provided with a spring top seat 11, and the surface of the spring top seat 11 is mounted with a top rod 10, one end of the top rod 10 away from the spring top seat 11 is connected with one end of the floating punch seat 3, so that after the punching is completed, the floating punch seat 3 is reset by floating up through the elastic mechanism.

[0052] The spring top seat 11 can be integrated with a spring assembly or an elastic pin structure inside, when the floating punch seat 3 is pressed and moves downward during the punching process, the top rod 10 compresses the elastic element inside the spring top seat 11 downward, after the stamping force is released, the spring top seat 11 lifts the top rod 10 upward through the elastic release action, so as to drive the floating punch seat 3 to return to the initial position and complete the reset.

[0053] In the embodiment of the utility model, the spring top seat 11 can adopt the die spring top mechanism, the standard spring ejection seat, the pre-press reset cylinder or the spring limiting module structure in the prior art, for example, the guide column type spring ejection structure or the die reset assembly commonly used in industry, which has the characteristics of compact structure, stable action, timely response and the like, is easy to maintain and replace, and is suitable for long-term operation under the continuous stamping scene.

[0054] Through the connection structure of the spring top seat 11 and the top rod 10, the floating punch seat 3 can be bounced to the upper position in time after the punch reset, and auxiliary ejection function can be provided during part replacement or mold removal, so as to improve the operation efficiency and structural coordination of the overall die system.

[0055] As shown in Figure 3 and Figure 4 In one embodiment of the utility model, a forming process of a variable cross-section chain link includes the following steps:

[0056] S1: punching out the chain link shape and its large-end pin hole on the steel plate material to obtain an initial-shaped chain link material;

[0057] S2: sequentially performing π type cold bending and U type cold bending forming on the initial-shaped chain link material to make it into an equal cross-section U type bent chain link;

[0058] S3: performing induction heating on the small-end region of the equal cross-section U type bent chain link, and performing axial hot extrusion on it in a die, so that the thickness of the small-end region in the punching area is 5mm, and the thickness gradually transitions to the same thickness 4.3mm of the large end of the chain link from the region at an inclination of 2.7°;

[0059] S4: After hot extrusion, the U-shaped bend chain link is hot-shaped using the hot holding state of the die, so that the 90° bend arc of the U-shaped part is reduced as much as possible to close to R0, improving the fit between the inner circle of the small end and the pin and the meshing between the outer circle and the sprocket, ensuring that the straight section length in the width direction of the U-shaped bend chain link is not less than 95%, and obtaining a variable cross section chain link. The temperature of the die maintained during the hot forming process is 450℃ to 650℃.

[0060] S5: The small end region of the variable cross-section chain link is punched using a built-in floating punching device that punches from the inside to the outside.

[0061] In one embodiment of this utility model, according to Figure 3 and Figure 4 The structural features shown involve variable cross-section control, thermoforming optimization, and improved punching quality around the small end region of the chain links, aiming to enhance the overall strength, wear resistance, and service life of the chain. This forming process specifically includes the following five steps, with a reasonable operational sequence and tight coordination. Each step is interconnected in terms of shape control, material organization, and precision assurance, ensuring that the final formed chain links meet the requirements of high precision, high strength, and high durability.

[0062] In step S1, the outline of the chain link and its large-end pin hole are first punched into the steel plate material to obtain the preliminary chain link material. This step uses a blanking die to precisely cut the raw material, ensuring the consistency of the chain link outline and hole size, providing a stable geometric basis for subsequent forming. Pre-machining the large-end pin hole size can improve the process cycle and maintain the concentricity of the hole during cold bending and hot extrusion, avoiding deformation.

[0063] In step S2, the initial link material is sequentially subjected to π-shaped and U-shaped cold bending to form a U-shaped bent link with a uniform cross-section. This step uses a cold bending die for staged forming, allowing the U-shaped bent link to gradually take shape, controlling springback, and maintaining consistent geometric dimensions. The link material exhibits a significant hardening trend during cold bending, providing structural stability for subsequent thermoforming. The uniform cross-section structure facilitates control of the bending path and initial strength state, creating conditions for subsequent localized variable cross-section treatment in the small-end region.

[0064] In step S3, the small end region of the U-shaped bend link with uniform cross-section is induction heated and then axially hot-extruded in a die, so that the thickness of the small end region in the punching area is 5mm, and gradually transitions outward from this region at a 2.7° angle to the same thickness of 4.3mm as the large end of the link. This step softens the material through local heating, reducing the forming load. At the same time, by controlling the thickness transition area through the die, a continuous variable cross-section structure is formed, which not only improves the tensile strength and fatigue strength of the small end region, but also provides reinforced support for the punching area, so that the punching area is no longer a weak point in the structure.

[0065] In step S4, after the hot extrusion is completed, the U-shaped bent link is heat shaped by using the die heat holding state, so that the 90° bending angle of the U-shaped part is reduced as close to R0 as possible, the fitting degree of the small end inner circle and the pin shaft and the meshing degree of the outer circle and the sprocket are improved, the length of the straight section in the width direction of the U-shaped bent link is ensured to be not less than 95%, and thus the variable cross-section link is obtained. The temperature maintained by the die in the shaping process is controlled between 450 DEG C and 650 DEG C, which helps to release the internal stress after cold bending and hot extrusion, improves the size stability and circular arc consistency after forming, ensures the assembly precision and cooperation strength of the link structure, the pin shaft and the sprocket, and improves the meshing efficiency.

[0066] In step S5, the small end region of the variable cross-section link is punched by using an internal floating punching device which punches from the inside to the outside. This step realizes the punching path design of the punch pin penetrating from the inside to the outside of the link by setting the punch pin structure located at the inside of the link, combining the inclined limit structure and the elastic buffer mechanism, and completely solves the problems of insufficient support of the die, incomplete hole wall, punching deviation and step defects in the traditional punching from the outside to the inside. The floating punch pin seat provides stable support for the inner wall during the punching process and automatically resets after punching, so as to ensure that the punching position of each link is consistent and the shape is accurate. Finally, the hole roundness is improved, the hole wall quality is enhanced, and the fitting degree of the hole and the pin shaft is significantly improved, so that the early failure of the link caused by poor contact is avoided.

[0067] Through the implementation of the forming process, the overall strength and size precision of the small end structure of the link are improved, and the punching quality and cooperation effect are significantly improved. Experiments show that the tensile strength of the link treated by the process is increased by at least 20%, the fatigue life is increased by more than 3 times, the initial wear elongation rate of the link is reduced from 0.2% of the traditional one to 0.1%, and the service period is significantly prolonged. The process is suitable for mass production and high-precision chain production, and has significant application value for improving the running stability of the chain assembly, prolonging the maintenance period and reducing the maintenance cost.

[0068] In the embodiment, after step S5 is completed, the variable cross-section link is further subjected to heat treatment, shot blasting treatment and rust prevention treatment. The strength and surface hardness of the link are improved, the internal stress is eliminated, the fatigue resistance and corrosion resistance are enhanced, and thus the service life and running stability of the chain are significantly prolonged.

[0069] The above only describes the preferred embodiments of the utility model and does not limit the utility model, and any modification, equivalent replacement and improvement made within the spirit and principle of the utility model should be included in the protection scope of the utility model.

Claims

1. A built-in floating punching device for variable cross-section chain links, comprising a lower die seat (1), and an upper die seat (6) arranged above the lower die seat (1), a punching cylinder (5) is mounted on the upper surface of the upper die seat (6), and a positioning and pressing block (12) is arranged at one end of the punching cylinder (5), and a backing plate (4) is arranged on the lower surface of the upper die seat (6), characterized in that, The surface of the base plate (4) is provided with a concave die seat (7), and the side surface of the concave die seat (7) is provided with a first through hole; The surface of the lower die seat (1) is provided with an inclined limiting block (2) and a pressing block (9), the outer side of the pressing block (9) is connected with a floating punch seat (3), one end of the floating punch seat (3) is provided with an elastic ring (17), the side surface of the elastic ring (17) is provided with an inclined pushing block (13), the side surface of the inclined pushing block (13) is provided with a punch (16), the side surfaces of the inclined limiting block (2) and the inclined pushing block (13) are respectively provided with a first inclined surface and a second inclined surface, and the inclination angles of the first inclined surface and the second inclined surface are the same.

2. A built-in floating piercing device for a variable cross-section chain link according to claim 1, characterized in that, The inside of the first through hole is provided with a punching concave die (18), and the surface of the punching concave die (18) is provided with a through hole, and the punch (16) and the through hole are on the same axis.

3. A built-in floating piercing device for a variable cross-section chain link according to claim 2, characterized in that, The side surface of the concave die seat (7) away from the first through hole is provided with a second through hole, and the inside of the second through hole is provided with a spring (14), the inside of the spring (14) is provided with a positioning pin (15), and the positioning pin (15) and the through hole are on the same axis.

4. A built-in floating piercing device for a variable cross-section chain link according to claim 1, characterized in that, The surface of the inclined limiting block (2) is provided with a third inclined surface.

5. A built-in floating piercing device for a variable cross-section chain link according to claim 2, characterized in that, The surface of the punch (16) is provided with a titanium layer, the elastic ring (17) is made of polyurethane material, and the punching concave die (18) is made of hard alloy material.

6. A built-in floating piercing device for a variable cross-section chain link according to claim 1, characterized in that, The lower surface of the lower die seat (1) is provided with a spring seat (11), and the surface of the spring seat (11) is provided with a top rod (10), and one end of the top rod (10) away from the spring seat (11) is connected with one end of the floating punch seat (3).

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