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

Abstract

The invention is suitable for the technical field of chain link machining, and particularly relates to a built-in floating punching device for a variable cross-section chain link and a forming technology.The built-in floating punching device comprises a lower die base, an upper die base is arranged above the lower die base, a punching air cylinder is installed on the upper surface of the upper die base, and a positioning pressing block is arranged at one end of the punching air cylinder; 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. Through the variable cross-section hot extrusion and hot shaping process of the small end area, the tensile strength and fatigue strength of the small end of the chain link are remarkably improved, and the fitting degree and meshing precision of the chain link, a pin shaft and a chain wheel are improved; a punching mode from inside to outside is achieved through the built-in floating punching device, and the problems of hole position deviation, hole wall steps and early failure caused by insufficient supporting in the traditional punching process are solved.

Description

Technical Field

[0001] The invention relates to the technical field of chain link processing, in particular to a built-in floating punching device and a forming process for a variable-section chain link. Background Art

[0002] Existing chain link structures are widely used in agriculture, light industry, and material transportation. Chain links are meshed with sprockets through pins, and their structure is generally composed of a U-shaped chain link body and a connecting pin. In order to meet the strength requirements, the chain links are usually processed into U-shaped structures using a cold bending process, and pin holes are formed at both ends of the chain links by punching to achieve connection with the pins. Traditional punching methods are mostly punching from the outside to the inside. Due to structural limitations, a complete die support structure cannot be set on the inside of the chain link, resulting in insufficient support for the hole wall, easy deviation of the punching position, poor hole quality, low hole roundness, and in severe cases, hole steps will be formed, affecting the fit of the pin and reducing the transmission stability of the entire chain.

[0003] In addition, in the traditional forming process, the small end and the large end of the chain link are mostly designed with equal cross-sections. The small end is used as a punching site, which is more prone to fatigue damage under long-term stress. Since the small end area needs to simultaneously meet the structural functions of the pin connection and the sprocket meshing, its dimensional accuracy, arc transition and cross-sectional strength have a significant impact on the service life of the entire chain. However, the cold-formed chain links are subject to the hardness of the raw materials, bending rebound and mold constraints, resulting in unstable arcs after forming, large bending radius, high dimensional error, and low fit between the sprocket and the pin. The chain is prone to problems such as poor meshing, dead joints, and jumping during use. Summary of the invention

[0004] The purpose of the embodiments of the present invention is to provide a built-in floating punching device and a forming process for a variable-section chain link, aiming to solve the technical problems mentioned in the background technology.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] A built-in floating punching device for a variable cross-section chain link, comprising a lower die seat, 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 clamping block is arranged at one end of the punching cylinder, a pad is arranged on the lower surface of the upper die seat, a die seat is installed on the surface of the pad, and a first through hole is opened on the side of the die seat;

[0007] The surface of the lower die seat is provided with an inclined rebar limiting block and a clamping block, and the outer side of the clamping block is connected to a floating punch seat, one end of the floating punch seat is installed with an elastic ring, and the side of the elastic ring is provided with an inclined rebar pushing block, and the side of the inclined rebar pushing block is installed with a punch, and the corresponding sides of the inclined rebar limiting block and the inclined rebar pushing block 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.

[0008] Furthermore, a punching die is installed inside the first through hole, and a through hole is opened on the surface of the punching die, and the punch pin and the through hole are on the same axis.

[0009] Furthermore, a second through hole is formed on the side of the die seat away from the first through hole, and a spring is installed inside the second through hole. A positioning pin is arranged inside the spring, and the positioning pin and the through hole are on the same axis.

[0010] Furthermore, a third inclined surface is provided on the surface of the inclined reed limit block.

[0011] Furthermore, a titanium layer is provided on the surface of the punch, the elastic ring is made of polyurethane, and the punching die is made of cemented carbide.

[0012] Furthermore, a spring-loaded seat is disposed on the lower surface of the lower die seat, and a push rod is installed on the surface of the spring-loaded seat, and one end of the push rod away from the spring-loaded seat is connected to one end of the floating pin seat.

[0013] A built-in floating punching device for a variable cross-section chain link, wherein a spring-loaded seat is arranged on the lower surface of the lower die seat, and a push rod is installed on the surface of the spring-loaded seat, wherein one end of the push rod away from the spring-loaded seat is connected to one end of a floating rivet seat.

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

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

[0016] S2: The primary chain link material is subjected to π-shaped cold bending and U-shaped cold bending in sequence to form a U-shaped bent chain link with a uniform cross section;

[0017] S3: The small end area of ​​the equal-section U-bend chain link is induction heated and axially hot extruded in a die, so that the thickness of the small end area in the punching area is 5 mm, and gradually transitions outward from this area at a slope of 2.7° to the same thickness of 4.3 mm as the large end of the chain link;

[0018] S4: After the hot extrusion is completed, the U-shaped bent chain link is hot-shaped by keeping the mold hot, so that the 90° bend angle arc of the U-shaped part is reduced as close to R0 as possible, the fit between the inner circle of the small end and the pin shaft and the meshing degree between the outer circle and the sprocket are improved, and the length of the straight section in the width direction of the U-shaped bent chain link is ensured to be not less than 95%, so as to obtain a variable cross-section chain link;

[0019] S5: Punching the small end area of ​​the variable cross-section chain link using a built-in floating punching device that punches from the inside to the outside.

[0020] Furthermore, the temperature of the mold during the thermal shaping process is maintained at 450°C to 650°C.

[0021] Furthermore, after completing step S5, the method further includes the steps of heat treating, shot blasting and rust-proofing the variable cross-section chain links.

[0022] The invention provides a built-in floating punching device and a forming process for a variable cross-section chain link, which has the following beneficial effects:

[0023] Through the variable-section hot extrusion and hot shaping process in the small-end area, the tensile strength and fatigue strength of the small end of the chain link are significantly improved, and the fit and meshing accuracy of the chain link, pin shaft and sprocket are improved; the built-in floating punching device is used to realize the punching method from the inside to the outside, which solves the problems of hole position offset, hole wall steps and early failure caused by insufficient support in the traditional punching process; at the same time, the floating punch structure has elastic return ability, which is suitable for continuous production, with high punching quality and stable efficiency, further improving the reliability and service life of the chain operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The figure is a schematic diagram of the structure of a built-in floating punching device for a variable cross-section chain link.

[0025] Figure 2 A built-in floating punching device for variable cross-section chain links Figure 1 Enlarged view of point A.

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

[0027] Figure 4 It is a schematic diagram of the structure after the variable cross-section chain link and the pin are assembled.

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

[0029] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0030] The specific implementation of the present invention is described in detail below in conjunction with specific embodiments.

[0031] like Figure 1-Figure 2 As shown, an embodiment of the present invention provides a built-in floating punching device for a variable cross-section chain link, comprising a lower die base 1, and an upper die base 6 is arranged 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 arranged at one end of the punching cylinder 5, a pad 4 is arranged on the lower surface of the upper die base 6, a die base 7 is installed on the surface of the pad 4, and a first through hole is opened on the side of the die base 7;

[0032] The surface of the lower die seat 1 is provided with an inclined ridge limit block 2 and a clamping block 9, and the outer side of the clamping block 9 is connected to a floating rivet seat 3, an elastic ring 17 is installed at one end of the floating rivet seat 3, and an inclined ridge push block 13 is provided on the side of the elastic ring 17, and a rivet 16 is installed on the side of the inclined ridge push block 13, and the corresponding sides of the inclined ridge limit block 2 and the inclined ridge push 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, and the rivet 16 and the through hole are on the same axis.

[0033] In one embodiment of the present 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 a high temperature to form a predetermined variable cross-sectional thickness structure.

[0034] The built-in floating punching device for variable cross-section chain links, when in use, realizes the positioning, pressing 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 link workpiece 8 is placed at a preset position between the bevel stop block 2 and the floating pin seat 3, so that the small end area of ​​the link workpiece 8 fits against the side surfaces of the bevel stop block 2 and the floating pin seat 3, and is consistent with the impact direction of the pin 16; at this time, the first inclined surface and the second inclined surface of the bevel stop block 2 and the bevel push block 13 fit against each other, forming a bevel wedge matching mechanism for converting the impact direction.

[0036] Subsequently, the punching cylinder 5 is driven to move, driving the positioning and clamping block 12 connected to one end thereof to move downward, so that the chain link workpiece 8 is clamped and fixed to avoid slippage or displacement during the punching process; at the same time, the pad 4 located on the lower surface of the upper die seat 6 and the die seat 7 connected thereto are lowered accordingly, so that the punching die 18 on the die seat 7 surrounds the outer side of the chain link workpiece 8, forming a complete supporting structure. The through hole in the punching die 18 is used to provide reverse support force and a chip flushing channel for the punch pin 16.

[0037] After the chain link workpiece 8 is completely positioned and clamped, the punching cylinder 5 continues to be driven to further act on the positioning and clamping block 12, thereby driving the inclined rebar pushing block 13 to slide downward along the second inclined surface. Since the inclined rebar pushing block 13 is installed on the floating rivet seat 3 through the elastic ring 17, it is elastically compressed after receiving the pushing force, and at the same time drives the rivet 16 to penetrate from the inside to the outside of the chain link workpiece 8 along the preset axial direction, and completes the punching operation through the through hole.

[0038] After punching is completed, the force of the punching cylinder 5 is released, the elastic ring 17 recovers elastically, driving the inclined rod pushing block 13 and the punch 16 to return to their original positions, and the floating punch seat 3 returns to its initial position under the action of the ejection structure or the mold elastic element, completing a punching cycle.

[0039] The device is provided with a built-in punch structure so that the punch is used to punch holes from the inside to the outside of the chain link workpiece 8, effectively avoiding defects such as hole wall collapse, deviation, and step generation caused by the inability to support the inner arc area of ​​the small end of the chain link during the traditional outside-to-inside punching process; the inclined surface matching structure of the inclined ridge limit block 2 and the inclined ridge push block 13 is adopted to convert the vertical pressing force into an axial impact force, thereby realizing the punching operation in the spatial structure, with a compact structure and clear force transmission; the floating punch seat 3 and its matching elastic ring 17 can provide flexible recovery ability, so that the punch has a rebound ability, which is suitable for continuous stamping operations and improves the punching rhythm and mold life.

[0040] Through the punching device in the embodiment of the present invention, the small end area of ​​the chain link workpiece 8 can obtain complete inner wall support, the punch pin and the through hole have good alignment, the hole position accuracy is high, the hole wall is smooth, the hole roundness is improved, and the fitting quality between the hole and the pin shaft is significantly improved, thereby improving the overall meshing performance and operating reliability of the chain assembly, extending the chain life and reducing the probability of early failure.

[0041] In this embodiment, a second through hole is formed on the side of the die holder 7 away from the first through hole, and a spring 14 is installed inside the second through hole, and a positioning pin 15 is arranged inside the spring 14, and the positioning pin 15 is coaxial with the through hole, so as to accurately position the chain link workpiece 8 according to the position of the first hole when performing the second punching operation on the chain link workpiece 8.

[0042] Specifically, after the punching operation of the first hole in the small end area of ​​the chain link workpiece 8 is completed, when preparing to punch the second hole on the other side of the same chain link workpiece 8, the operator re-clamps the chain link workpiece 8 in the opposite direction so that its first hole faces the die seat 7, and pushes the positioning pin 15 outward along the direction of the second through hole under the elastic force of the spring 14, and its front end is automatically inserted into the first hole of the chain link workpiece 8, thereby completing the rapid hole positioning of the chain link workpiece 8, ensuring that the punching position of the second hole remains strictly coaxial with the first hole, avoiding left and right deviation or spacing errors.

[0043] Through this positioning structure, the process of re-clamping the chain link workpiece 8 after turning it over can be simplified, the problem of the second hole punching deviation caused by manual positioning error can be eliminated, the consistency and matching accuracy of multi-hole punching can be improved, and at the same time, the built-in floating punching device can be used to complete high-quality symmetrical hole punching operations, further improving the size consistency and assembly performance of the finished chain link.

[0044] In this embodiment, a third inclined surface is provided on the surface of the inclined stopper 2. The third inclined surface is used to support the inner wall of the large end of the chain link workpiece 8 to enhance the stability of the chain link workpiece 8 during the punching process.

[0045] Specifically, when the chain link workpiece 8 is placed in the punching device, its small end area fits into the inclined wedge matching structure formed by the first inclined surface and the second inclined surface, while its large end area fits into the third inclined surface of the inclined ridge limit block 2; since the inner wall of the large end of the chain link workpiece 8 is usually an arc surface structure, by setting a third inclined surface matching its contour, the curved surface fitting between the chain link workpiece 8 and the inclined ridge limit block 2 can be achieved, thereby providing support and positioning for the chain link workpiece 8 in the three-dimensional direction.

[0046] The setting of the third inclined surface further reduces the overall shaking or tilting of the chain link workpiece 8 when subjected to the punching force, helps to maintain the stability of the workpiece posture and the accuracy of the punching path, improves the punching accuracy, hole coaxiality and hole wall quality, and is particularly suitable for processing chain link structural parts with complex variable cross-section structures and asymmetric shapes at both ends.

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

[0048] The elastic ring 17 is made of polyurethane, which has excellent elastic recovery performance and fatigue resistance. It can provide effective buffering and rebound support after the punch is subjected to force, and maintain a stable elastic response under high-frequency operating conditions, which helps the punch to return to its position accurately after punching is completed, ensuring the rhythm consistency of the continuous stamping process and the reset stability of the mold mechanism.

[0049] The punching die 18 is made of cemented carbide, which has extremely high compressive strength and excellent wear resistance. It is particularly suitable for withstanding high-intensity impact loads from punches. It can maintain the accuracy and smoothness of the through holes during long-term use and prevent problems such as hole displacement and punch jamming caused by wear of the die.

[0050] The reasonable configuration of the above-mentioned various materials enables the built-in floating punching device provided by the present invention to maintain high punching accuracy and long service life under high-intensity and continuous operation conditions, effectively improving the processing consistency of the small end holes of the variable-section chain links and the overall assembly quality of the chain components.

[0051] In this embodiment, a spring-loaded seat 11 is provided on the lower surface of the lower die seat 1, and a push rod 10 is installed on the surface of the spring-loaded seat 11. One end of the push rod 10 away from the spring-loaded seat 11 is connected to one end of the floating rivet seat 3, so that after the punching is completed, the floating rivet seat 3 is floated and reset by the elastic mechanism.

[0052] A spring assembly or an elastic pin structure may be integrated inside the ejector seat 11. When the floating rivet seat 3 is pressed downward during the punching process, the ejector rod 10 compresses the elastic element inside the ejector seat 11 downward. After the punching force is released, the ejector seat 11 pushes the ejector rod 10 upward through the elastic release effect, thereby driving the floating rivet seat 3 back to the initial position and completing the reset.

[0053] In an embodiment of the present invention, the ejector seat 11 can adopt the mold ejector mechanism, standard spring ejector seat, pre-loaded reset cylinder or spring limit module structure in the prior art, such as the guide column spring ejector structure or mold reset assembly commonly used in industry, which has the characteristics of compact structure, stable movement, timely response, etc., is easy to maintain and replace, and is suitable for long-term operation in continuous stamping scenarios.

[0054] By providing a connection structure between the ejector seat 11 and the ejector rod 10, not only can the floating rivet seat 3 rebound to the upper position in time after the rivet is reset, but also an auxiliary ejection function can be provided when replacing parts or unloading the mold, thereby improving the operating efficiency and structural coordination of the overall mold system.

[0055] like Figure 3 and Figure 4 As shown, in one embodiment of the present invention, a molding process of a variable cross-section chain link, the molding process specifically includes the following steps:

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

[0057] S2: The primary chain link material is subjected to π-shaped cold bending and U-shaped cold bending in sequence to form a U-shaped bent chain link with a uniform cross section;

[0058] S3: The small end area of ​​the equal-section U-bend chain link is induction heated and axially hot extruded in a die, so that the thickness of the small end area in the punching area is 5 mm, and gradually transitions outward from this area at a slope of 2.7° to the same thickness of 4.3 mm as the large end of the chain link;

[0059] S4: After the hot extrusion is completed, the U-shaped bent chain link is heat-shaped by using the hot holding state of the mold to reduce the 90° bend angle arc of the U-shaped part to as close to R0 as possible, improve the fit between the inner circle of the small end and the pin shaft and the meshing degree between the outer circle and the sprocket, ensure that the length of the straight section in the width direction of the U-shaped bent chain link is not less than 95%, and obtain a variable cross-section chain link. The temperature maintained by the mold during the hot shaping process is 450℃ to 650℃;

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

[0061] In one embodiment of the present invention, according to Figure 3 and Figure 4 The structural features shown in the figure are to control the cross-section around the small end of the chain link, optimize the hot forming, and improve the punching quality, aiming to improve the overall strength, wear resistance and service life of the chain. The forming process specifically includes the following five steps, with a reasonable operation sequence and close coordination. The steps are linked in shape control, material organization and precision assurance, ensuring that the final formed chain link meets the requirements of high precision, high strength and high durability.

[0062] In step S1, the chain link shape and the large end pin hole are first punched out on the steel plate material to obtain the initial chain link material. This step uses the blanking die to accurately cut the raw material to ensure the consistency of the chain link profile and hole size, providing a stable geometric basis for subsequent forming. The large end pin hole size is pre-processed to improve the process cycle and maintain the hole concentricity during cold bending and hot extrusion to avoid deformation.

[0063] In step S2, the initial link material is subjected to π-shaped cold bending and U-shaped cold bending in sequence to form a U-shaped bent link with a constant cross section. This step uses a cold bending mold to form in stages, so that the U-shaped bent link is gradually formed, the springback is controlled, and the geometric dimensions are kept consistent. The link material has an obvious hardening trend during the cold bending process, which can provide structural stability for subsequent hot forming. The constant cross-section structure facilitates the control of the bending path and the initial strength state, creating conditions for the subsequent local variable cross-section processing of the small end area.

[0064] In step S3, the small end region of the equal-section U-bend link is induction heated and axially hot extruded in the mold, so that the thickness of the small end region in the punching area is 5 mm, and gradually transitions outward from this region at a slope of 2.7° to the same thickness of 4.3 mm as the large end of the link. This step softens the material through local heating to reduce the forming load, and at the same time controls the thickness transition zone through the mold to form a continuous variable cross-section structure, which not only improves the tensile strength and fatigue strength of the small end region, but also provides enhanced support for the punching area, so that the punching area is no longer a structural weak point.

[0065] In step S4, after the hot extrusion is completed, the U-shaped bent chain link is hot-shaped by using the hot-maintaining state of the mold, so that the 90° bend angle arc of the U-shaped part is reduced as close to R0 as possible, the fit between the inner circle of the small end and the pin and the meshing degree between the outer circle and the sprocket are improved, and the length of the straight section in the width direction of the U-shaped bent chain link is ensured to be not less than 95%, thereby obtaining a variable cross-section chain link. The temperature maintained by the mold during the shaping process is controlled between 450°C and 650°C, which helps to release the internal stress after cold bending and hot extrusion, improve the dimensional stability and arc consistency after forming, ensure the assembly accuracy and matching strength of the chain link structure with the pin and sprocket, and improve the meshing efficiency.

[0066] In step S5, the small end area of ​​the variable cross-section chain link is punched using a built-in floating punching device that punches from the inside to the outside. This step achieves a punching path design in which the punch penetrates from the inside of the chain link to the outside by setting a punching pin structure located on the inside of the chain link, combined with an inclined ridge limiting structure and an elastic buffer mechanism, which completely solves the problems of insufficient die support, incomplete hole wall, punching deviation and step defects in traditional punching from the outside to the inside. The floating punching pin seat provides stable support for the inner wall during the punching process and automatically resets after punching to ensure that the punching position and shape of each chain link are consistent. Ultimately, the roundness of the hole is improved, the quality of the hole wall is enhanced, and the fit between the hole and the pin shaft is significantly improved, avoiding early failure of the chain link due to poor contact.

[0067] Through the implementation of this forming process, not only the overall strength and dimensional accuracy of the small end structure of the chain link are improved, but also the punching quality and matching effect are significantly improved. Experiments show that the tensile strength of the chain link treated by this process is increased by at least 20%, the fatigue life is increased by more than 3 times, the initial wear elongation of the chain link is reduced from the traditional 0.2% to 0.1%, and the service life is significantly extended. This process is suitable for large-scale, high-precision chain production, and has significant application value in improving the operating stability of the chain assembly, delaying the maintenance cycle, and reducing maintenance costs.

[0068] In this embodiment, after completing step S5, the variable cross-section chain links are further subjected to heat treatment, shot blasting and rust prevention treatment to improve their strength and surface hardness, eliminate internal stress, and enhance fatigue resistance and corrosion resistance, thereby significantly extending the service life and operating stability of the chain.

[0069] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A built-in floating punching device for a variable cross-section chain link, comprising a lower die base (1), an upper die base (6) being arranged above the lower die base (1), a punching cylinder (5) being installed on the upper surface of the upper die base (6), and a positioning and clamping block (12) being arranged at one end of the punching cylinder (5), and a pad (4) being arranged on the lower surface of the upper die base (6), characterized in that: A die seat (7) is installed on the surface of the backing plate (4), and a first through hole is opened on the side surface of the die seat (7); The surface of the lower die seat (1) is provided with an inclined rebar limiting block (2) and a clamping block (9), and the outer side of the clamping block (9) is connected to a floating rivet seat (3), one end of the floating rivet seat (3) is installed with an elastic ring (17), and the side of the elastic ring (17) is provided with an inclined rebar pushing block (13), and the side of the inclined rebar pushing block (13) is installed with a rivet (16), and the corresponding side surfaces of the inclined rebar limiting block (2) and the inclined rebar 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 punching device for a variable cross-section chain link according to claim 1, characterized in that: A punching die (18) is installed inside the first through hole, and a through hole is opened on the surface of the punching die (18), and the punching pin (16) and the through hole are on the same axis.

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

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

5. The built-in floating punching device for variable cross-section chain links according to claim 1, characterized in that: The surface of the punch pin (16) is provided with a titanium layer, the elastic ring (17) is made of polyurethane material, and the punching die (18) is made of hard alloy material.

6. A built-in floating punching 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-loaded seat (11), and a push rod (10) is installed on the surface of the spring-loaded seat (11), and one end of the push rod (10) away from the spring-loaded seat (11) is connected to one end of the floating pin seat (3).

7. A forming process for a variable cross-section chain link, characterized in that: The molding process specifically comprises the following steps: S1: punching out the chain link shape and the large end pin hole on the steel plate material to obtain the initial chain link material; S2: The primary chain link material is subjected to π-shaped cold bending and U-shaped cold bending in sequence to form a U-shaped bent chain link with a uniform cross section; S3: The small end area of ​​the equal-section U-bend chain link is induction heated and axially hot extruded in a die, so that the thickness of the small end area in the punching area is 5 mm, and gradually transitions outward from this area at a slope of 2.7° to the same thickness of 4.3 mm as the large end of the chain link; S4: After the hot extrusion is completed, the U-shaped bent chain link is hot-shaped by keeping the mold hot, so that the 90° bend angle arc of the U-shaped part is reduced as close to R0 as possible, the fit between the inner circle of the small end and the pin shaft and the meshing degree between the outer circle and the sprocket are improved, and the length of the straight section in the width direction of the U-shaped bent chain link is ensured to be not less than 95%, so as to obtain a variable cross-section chain link; S5: Punching the small end area of ​​the variable cross-section chain link using a built-in floating punching device that punches from the inside to the outside.

8. The forming process of the variable cross-section chain link according to claim 7, characterized in that: In step S4, the temperature of the mold during the thermal shaping process is maintained at 450°C to 650°C.

9. The forming process of the variable cross-section chain link according to claim 7, characterized in that: After completing step S5, the method further includes the steps of heat treating, shot blasting and rust-proofing the variable cross-section chain links.

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