A first open later closed long bar end upsetting forming die

Abstract

This utility model discloses a pre-opening and post-closing upsetting die for long bars, relating to the field of rebar upsetting technology, aiming to solve the problem of balancing head complexity and forming quality in existing technologies. The die includes a forming die and a clamping die arranged along the bar's axis, both being two-part split structures that form a continuous cavity when closed. The clamping die is not fully closed when closed to effectively clamp the bar, while the forming die is fully closed when closed to form a through-hole forming cavity for the bar portion. An annular boss is provided on the end face away from the clamping die. The upsetting head is arranged on the same axis as the forming die and can move along the axis. Its end near the forming die has a head forming cavity, consisting of a head forming section and a guide section. The annular boss of the forming die can enter and slide into the guide section. This utility model combines the advantages of open and closed die forging, enabling upsetting of complex head shapes, effectively constraining material accumulation, preventing bar bending and folding, improving forming quality, and facilitating operation.

Description

Technical Field

[0001] This utility model relates to the field of steel bar upsetting technology, and more specifically to an open-then-close type upsetting die for long bar ends, which is particularly suitable for upsetting irregularly shaped steel bar ends that have been sheared. Background Technology

[0002] In the processing of long bars (such as steel bars) heads, head upsetting or top upsetting to create a large head is a common local top upsetting die forging process. Currently, this process mainly uses flat forging, which is divided into two forms: closed die forging and open die forging.

[0003] Closed-die forging involves two closed dies forming a molding cavity, into which a punch (upsetting head) enters for top upsetting. (See attached diagram.) Figure 1 and attached Figure 2 As shown. Its advantage lies in the fact that by controlling the volume of material within the cavity and the minimal clearance between the punch and die, flash-free forging can be achieved, and a full head filling can be obtained regardless of the amount of material. However, closed-die forging also has significant limitations: First, since the punch (upsetting head) needs to enter the cavity, its outer ring must be flat, making it impossible to machine heads with a beveled outer ring. If a beveled outer ring is machined, the punch end face must be concave, resulting in an infinitely thin outer edge, as shown in the attached figure. Figure 3 As shown, this structure cannot guarantee strength during use and will quickly wear out and break. Secondly, in actual use, the outer ring of the upsetting head will develop rounded corners due to pressure wear, as shown in the attached diagram. Figure 4 As shown, this causes a dent at the product head, and the structural strength is difficult to guarantee, resulting in a short upsetting head lifespan.

[0004] In open-die forging, the head forming cavity is located inside the punch, and the outer ring of the head end face can have a slope, thus enabling more complex head designs, as shown in the attached figure. Figure 5 and attached Figure 6 As shown. However, open die forging also faces many problems: on the one hand, the material volume must be precisely controlled, otherwise the head will not be full or there will be lateral flash; on the other hand, during the upsetting process, the material accumulation is unrestrained, which makes it very easy to become unstable and cause the bar to bend and fold, especially for bars with beveled end faces, such as those with sloping end faces. Figure 7 As shown, this problem is even more pronounced, severely limiting its length-to-diameter ratio. Furthermore, open die forging requires extremely precise material volume to reduce flash, and it also suffers from instability leading to bar bending and folding.

[0005] In rebar end anchorage applications, the ideal head design is one where the head thickness decreases as the diameter increases, as shown in the attached figure. Figure 8As shown, this design allows for better load transmission from the reinforcing steel and saves material. However, due to the special properties of the reinforcing steel, existing technologies face many challenges in achieving this head shape:

[0006] First, the material volume of the steel bars cannot be precisely controlled. Even if the bar length is precisely controlled by pre-positioning, the volume of the steel bars themselves will vary greatly due to the large deviation in volume. This results in inconsistent product quality and makes it difficult to achieve a form without flash or with a full head.

[0007] Secondly, construction steel bars are generally cut by shearing, and the sheared end face is not perpendicular to the steel bar axis and has a large range of variation. Especially for steel bars that are not cut by a single branch, the angle between the vertical line of the sheared end face of the steel bar and the steel bar axis can reach 10 degrees. This means that when the length-to-diameter ratio is reduced to below 2.0, there will still be severe flash on one side of the head. However, the length-to-diameter ratio required for steel bar anchoring is generally above 2.6, making it difficult to achieve one-time upsetting.

[0008] Therefore, in order to achieve one-time hot forging of the anchor head of the steel bar, the existing technology can only adopt the closed die forging method, and the head shape, especially near the end face of the head, can only be a cylinder. This design not only wastes materials, but also increases the length-to-diameter ratio, making it difficult to meet the needs of practical applications. Utility Model Content

[0009] In view of this, the present invention provides a pre-opening and post-closing upsetting mold for the end of a long bar, which aims to solve the above-mentioned technical problems.

[0010] To achieve the above objectives, the present invention adopts the following technical solution:

[0011] A pre-opening and post-closing upsetting die for long bars includes:

[0012] A forming die and a clamping die are arranged along the axis of the bar stock. Both the forming die and the clamping die are two-part split structures, and when the molds are closed, they form a continuous through cavity. The clamping die is not completely closed when the molds are closed to ensure effective clamping of the bar stock. The forming die is completely closed when the molds are closed to form a through rod forming cavity. An annular boss is provided on the end face of the forming die away from the clamping die.

[0013] An upsetting head is arranged on the same axis as the forming mold. The upsetting head can move along the axial direction. The end of the upsetting head near the forming mold has a head forming cavity. The head forming cavity is composed of two sections. The bottom of the head forming cavity is the head forming section, which is used for head forming. The opening of the head forming cavity is the guide section. The annular boss of the forming mold can enter the guide section and slide inside it.

[0014] Through the above technical solution, this utility model achieves an upsetting head forming method that opens first and then closes by using the annular boss of the forming die to guide the forming cavity of the upsetting head. This combines the advantages of both open and closed die forging, meeting the design requirements of complex head shapes while effectively constraining material accumulation and preventing bending and folding of the rod. The clamping die is not completely closed when closed, effectively clamping the rod and ensuring its stability during upsetting; the forming die is completely closed when closed, forming the rod forming cavity, which helps improve the forming accuracy and quality of the rod. When the die is open, it forms a through channel, facilitating the insertion or removal of the rod, improving production efficiency and operational convenience.

[0015] Preferably, in the above-mentioned pre-opening and post-closing long bar end upsetting die, the inner diameter of the forming cavity of the rod is larger than the diameter of the bar, ensuring complete radial closure when the die is closed. A transition chamfer is provided on the end face of the forming die near the upsetting head. The inner diameter of the forming cavity being larger than the diameter of the bar ensures complete radial closure when the die is closed, effectively preventing material loss in the radial direction and improving forming quality. The transition chamfer on the end face of the forming die near the upsetting head reduces stress concentration in the transition section from the rod to the head, ensuring that the head strength is greater than the base material strength. It also reduces impact and wear on the die during upsetting, extending the die's service life.

[0016] Preferably, in the above-mentioned pre-opening and post-closing long bar end upsetting die, the inner diameter of the guide section of the head forming cavity of the upsetting head is larger than the outer diameter of the annular boss of the forming die. This ensures a constant small clearance fit between the annular boss of the forming die and the guide section of the head forming cavity of the upsetting head. The length of the guide section is equal to the length of the annular boss, and the outer root of the annular boss serves as a limiting end face. The upsetting head stops moving when it encounters the limiting end face. The constant small clearance fit between the inner diameter of the guide section of the head forming cavity and the outer diameter of the annular boss of the forming die ensures precise fit during upsetting, improving forming accuracy. The guide section length being equal to the annular boss length, and the outer root of the annular boss serving as a limiting end face, effectively controls the upsetting stroke and depth, ensuring the dimensional accuracy of the product.

[0017] Preferably, in the above-mentioned pre-opening and post-closing long bar end upsetting die, the small clearance fit is 0.1-0.2mm. Specifying a small clearance fit of 0.1-0.2mm ensures smooth sliding between the upsetting head and the forming die, effectively prevents excessive material extrusion in the gap, and further improves the forming quality.

[0018] Preferably, in the above-mentioned pre-opening and post-closing long bar end upsetting die, the clamping die has a two-part split structure, which is not fully closed when the die is closed, ensuring effective clamping of the bar. The clamping die is arranged against the forming die, and when the die is open, it forms a through channel for the bar to be inserted or removed. The two-part split structure of the clamping die, which is not fully closed when the die is closed, can better adapt to the shape and size differences of the bar, especially the reinforcing bars, ensuring effective clamping of the bar and improving the stability of the upsetting process. The arrangement of the clamping die against the forming die, which forms a through channel when the die is open, further improves the convenience of bar insertion and removal, and increases production efficiency.

[0019] Preferably, in the above-mentioned pre-opening and post-closing long bar end upsetting die, the bar stops when it passes through the open clamping die and the forming die and reaches the bottom of the head forming cavity of the upsetting head. That is, the distance between the upsetting head and the forming die determines the length of the upsetting material. By controlling the distance between the upsetting head and the forming die, the length of the upsetting material can be accurately determined, thereby ensuring the accuracy of the upsetting material volume and facilitating the production of upsetting products with precise dimensions and stable quality.

[0020] Preferably, in the above-mentioned open-then-close long bar end upsetting die, the upsetting head moves forward to begin upsetting. Before the annular boss of the forming die enters the guide section of the head forming cavity, it is open-die forging. After the annular boss of the forming die enters the guide section of the head forming cavity, the head forming cavity of the upsetting head and the end face of the annular boss form a completely closed chamber in both longitudinal and radial directions, i.e., closed-die forging. The volume of the chamber is variable and determined by the depth of the annular boss entering the guide section of the head forming cavity. The minimum volume of the chamber is when the end face of the upsetting head stops at the limiting end face of the forming die. During the process of the upsetting head moving forward to begin upsetting, it is initially open-die forging, and after the annular boss of the forming die enters the guide section of the head forming cavity, it transitions to closed-die forging. This open-then-close method fully leverages the advantages of both forging methods, enabling upsetting of complex head shapes while effectively constraining the material to prevent instability and flash, thus improving product quality and forming accuracy. The variable chamber volume, determined by the depth of the annular boss entering the guide section, is particularly important for reinforcing bars. Even for the same specification of reinforcing bars, differences in brand and batch can lead to variations in the shape and height of transverse and longitudinal ribs, resulting in inherently large volume tolerances. Precise control of the upsetting volume through bar length is impossible. Thanks to the variable volume of the closed chamber, as long as the material volume exceeds the minimum required volume (i.e., adjusting the upsetting head's receiving position) and combining this with adjustments to the upsetting force, a full head filling can be achieved regardless of the material quantity.

[0021] Preferably, in the above-mentioned pre-opening and post-closing long bar end upsetting die, the length of the upsetting material is equal to the volume of the upsetting material. The material volume and the upsetting pressure determine the depth to which the annular boss enters the head forming cavity, which is the final thickness of the bar forming head. This design achieves precise control of the head upsetting, improving the dimensional accuracy and quality stability of the product.

[0022] As can be seen from the above technical solution, compared with the prior art, this utility model discloses a pre-opening and post-closing end upsetting mold for long bars, which has the following beneficial effects:

[0023] 1. This technology ingeniously integrates the characteristics of open and closed die forging. Through a special combination of the forming die, clamping die, and upsetting head, it achieves an upsetting process that opens first and then closes, effectively solving the problem of balancing head complexity and forming quality in existing technologies. It provides a completely new technical solution for upsetting the ends of long bars. It resolves a series of head upsetting problems caused by large volume tolerances in reinforcing bars and is suitable for upsetting irregularly shaped reinforcing bar ends after shearing. It has broad practical application value and can improve the reliability of reinforcing bar anchorage and material utilization.

[0024] 2. Precise dimensional fit and motion control of each component, such as the matching of the inner diameter of the rod forming cavity with the diameter of the bar stock, and the small clearance fit between the head forming cavity and the annular boss, ensures reasonable material flow and precise filling during upsetting, improving the dimensional accuracy and surface quality of the product. This makes the shape and size of the upsetting head more in line with design requirements, reducing subsequent processing steps. The open-then-close upsetting method effectively avoids problems such as material instability, rod bending and folding, and lateral flash that are prone to occur in open die forging. It also overcomes the limitation of closed die forging in processing heads with a beveled outer ring, reducing the product defect rate and improving product quality stability.

[0025] 3. The partially closed design and two-part split structure of the clamping die facilitates rapid clamping and positioning of the bar stock, reducing auxiliary operation time and improving production efficiency. The structure of this die and the upsetting process are easily automated and can be integrated with automated production lines to further improve production efficiency and consistency, while reducing labor costs and labor intensity.

[0026] 4. The small clearance fit between the guide section of the forming cavity of the upsetting head and the annular boss of the forming die, as well as the transition chamfer on the end face of the forming die, effectively reduce the mutual friction and impact of the dies during the upsetting process, reduce the wear rate of the dies, extend the service life of the dies, and reduce production costs.

[0027] 5. The length of the upsetting material is the same as the material volume. By controlling the upsetting pressure and the depth of the annular boss entering the guide section, it can automatically adapt to problems such as the volume deviation of the bar stock. The requirements for precise control of the material volume are relatively broad, which improves the adaptability to different batches and specifications of bar stock and reduces the scrap rate in the production process.

[0028] 6. It enables flash-free or low-flash upsetting, reducing material waste, improving material utilization, and lowering raw material costs. It also helps save energy and reduce subsequent machining operations. A well-designed die structure and upsetting process reduce the force required during upsetting, lightening the equipment load, improving equipment operating efficiency and reliability, and reducing equipment maintenance costs. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0030] Figure 1 The attached diagram is a schematic diagram of an existing closed-die forging structure;

[0031] Figure 2 The attached diagram is a schematic diagram of the existing closed-die forged and upset steel bars;

[0032] Figure 3 The attached diagram is a schematic diagram of the concave end face structure of an existing closed-die forging upsetting head.

[0033] Figure 4 The attached diagram is a schematic diagram of the structure of the outer ring of the upsetting head in an existing closed-die forging, which has a rounded corner due to pressure wear.

[0034] Figure 5 The attached diagram is a schematic diagram of an existing open-die forging structure;

[0035] Figure 6 The attached diagram is a structural schematic of an existing open-die forged and upset steel bar.

[0036] Figure 7 The attached diagram is a schematic diagram of an existing shear reinforcement structure;

[0037] Figure 8 The attached diagram is a schematic diagram of the ideal state of existing steel reinforcement pier (product) structures;

[0038] Figure 9 The attached figure is a structural schematic diagram of the pre-opening and post-closing long bar end upsetting mold provided by this utility model;

[0039] Figure 10 The attached figure shows the invention provided by this utility model. Figure 9 Cross-sectional view of AA;

[0040] Figure 11 The attached figure shows the invention provided by this utility model. Figure 9 Cross-sectional view of BB;

[0041] Figure 12 The attached figure is a schematic diagram of the open forging stage of the pre-opening and post-closing long bar end upsetting die provided by this utility model.

[0042] Figure 13 The attached figure is a schematic diagram of the critical transition stage of the pre-opening and post-closing long bar end upsetting mold provided by this utility model.

[0043] Figure 14 The attached figure is a schematic diagram of the closed-die forging stage of the pre-opening and post-closing long bar end upsetting die provided by this utility model.

[0044] Figure 15 The attached figure is a structural schematic diagram of the upset forging endpoint state of the pre-opening and post-closing long bar end upset forming die provided by this utility model.

[0045] Figure 16 The attached figure is a schematic diagram of the structure of the pre-opening and post-closing long bar end upsetting mold provided by this utility model, which opens the mold and removes the part after the upsetting is completed.

[0046] in:

[0047] 1-Upsetting head;

[0048] 11-Head forming section; 12-Guide section;

[0049] 2- Molding mold;

[0050] 21-Shaped cavity for rod forming; 22-Annular boss; 23-Transition chamfer; 24-Limiting end face;

[0051] 3-Clamping mold;

[0052] 4-Bar stock. Detailed Implementation

[0053] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0054] See appendix Figure 9 To be continued Figure 11 This utility model discloses a pre-opening and post-closing upsetting die for the end of a long bar, comprising:

[0055] The forming mold 2 and clamping mold 3 are arranged along the axis of the bar stock 4. Both the forming mold 2 and the clamping mold 3 are two-half split structures, and when the molds are closed, they form a continuous through cavity. When the clamping mold 3 is closed, it does not completely close to ensure effective clamping of the bar stock 4. When the forming mold 2 is closed, it completely closes to form a through rod forming cavity 21. The end face of the forming mold 2 away from the clamping mold 3 is provided with an annular boss 22.

[0056] The upsetting head 1 is arranged on the same axis as the forming mold 2. The upsetting head 1 can move along the axial direction. The end of the upsetting head 1 near the forming mold 2 has a head forming cavity. The head forming cavity consists of two sections. The bottom of the head forming cavity is the head forming section 11, which is used for head forming. The opening of the head forming cavity is the guide section 12. The annular boss 22 of the forming mold 2 can enter the guide section 12 and slide inside it.

[0057] To further optimize the above technical solution, the inner diameter of the forming cavity 21 of the rod is larger than the diameter of the rod 4, ensuring that the radial direction is completely closed when the mold is closed, and a transition chamfer 23 is provided on the end face of the forming mold 2 near the upsetting head 1.

[0058] To further optimize the above technical solution, the inner diameter of the guide section 12 of the head forming cavity of the upsetting head 1 is larger than the outer diameter of the annular boss 22 of the forming mold 2, so that the annular boss 22 of the forming mold 2 and the guide section 12 of the head forming cavity of the upsetting head 1 have a constant small clearance fit. The length of the guide section 12 is equal to the length of the annular boss 22. The root of the outer edge of the annular boss 22 is a limiting end face 24. When the end face of the upsetting head 1 advances and touches the limiting end face 24, it stops moving.

[0059] In this embodiment, the small clearance fit is 0.1-0.2mm.

[0060] To further optimize the above technical solution, the clamping mold 3 has a two-part split structure, which is not completely closed when the mold is closed, ensuring effective clamping of the bar stock 4; the clamping mold 3 is arranged against the forming mold 2, and when the mold is opened, it forms a through channel for the bar stock 4 to be inserted or removed, as shown in the attached figure. Figure 16 As shown.

[0061] To further optimize the above technical solution, the bar stock 4 passes through the open clamping die 3 and forming die 2 and stops at the bottom of the forming cavity of the head forming cavity of the upsetting head 1. That is, the distance between the upsetting head 1 and the forming die 2 determines the length of the upsetting material.

[0062] In this embodiment, the upsetting head 1 moves forward to begin upsetting. Before the annular boss 22 of the forming die 2 enters the guide section 12 of the head forming cavity, it is an open die forging process, as shown in the attached figure. Figure 12 As shown; after the annular boss 22 of the forming die 2 enters the guide section 12 of the head forming cavity, the head forming cavity of the upsetting head 1 and the end face of the annular boss 22 form a completely closed chamber in both longitudinal and radial directions, i.e., closed die forging, as shown in the attached figure. Figure 12 and attached Figure 13 As shown, the volume of the chamber is variable and determined by the depth of the guide section 12 of the annular boss 22 entering the head forming cavity. The minimum volume of the chamber is when the end face of the upsetting head 1 stops at the limiting end face 24 of the forming mold 2, as shown in the attached figure. Figure 15 As shown.

[0063] To further optimize the above technical solution, the length of the upsetting material is the same as the volume of the upsetting material. The material volume and the upsetting pressure determine the depth of the annular boss 22 entering the head forming cavity, which is the final thickness of the bar stock 4 forming head.

[0064] The structure shown in the figure of this embodiment is a circular head. In other embodiments, it is not limited to a circular head. Other shapes, such as a square head, can also be achieved by the cooperation of the guide section 12 of the head forming cavity of the upsetting head 1 and the boss of the forming mold 2.

[0065] The function of the forming mold 2 is to change the shape of the rod. In this embodiment, it is to chamfer. In other embodiments, more rod shapes can be achieved, such as square cross-sections, which can be achieved simply by using different forming mold cavities.

[0066] The processing steps in this embodiment are as follows:

[0067] 1. Preparation stage:

[0068] The bar stock 4 is heated to a plastic state in order to perform upsetting.

[0069] The heated bar stock 4 is placed in the mold, so that the bar stock 4 passes through the open clamping mold 3 and forming mold 2 and reaches the bottom of the forming cavity of the head forming cavity of the upsetting head 1. At this time, the placement of the bar stock 4 should ensure that it can be formed smoothly during the upsetting process.

[0070] 2. Initial stage (open die forging):

[0071] The clamping die 3 is closed to effectively clamp the bar stock 4, but the clamping die 3 is not completely closed when it is closed to ensure that the bar stock maintains a stable position during the upsetting process.

[0072] When the molding mold 2 is closed, it completely closes to form a through rod forming cavity 21, ensuring the forming accuracy of the rod part.

[0073] The upsetting head 1 moves forward and begins upsetting the end of the bar stock. At this time, the annular boss 22 of the forming die 2 has not yet entered the guide section 12 of the forming cavity at the head of the upsetting head 1, which is the open die forging stage. In this stage, the material has a certain amount of free flow space during the upsetting process, which is beneficial for initial forming.

[0074] 3. Transition Phase:

[0075] As the upsetting head 1 continues to move forward, the annular boss 22 of the forming die 2 gradually enters the guide section 12 of the forming cavity at the head of the upsetting head 1. As the annular boss 22 goes deeper, the constraint on the upsetting material gradually increases, and the process begins to transition from open die forging to closed die forging.

[0076] 4. Key Stage (Closed-Die Forging):

[0077] When the annular boss 22 of the forming die 2 is fully inserted into the guide section 12 of the forming cavity of the head of the upsetting head 1, the head forming cavity of the upsetting head 1 and the end face of the annular boss 22 form a completely closed chamber in both the longitudinal and radial directions, entering the closed die forging stage. In this stage, the material is constrained in all directions within the closed chamber, ensuring the shape and dimensional accuracy of the upsetting forging.

[0078] The volume of the chamber can be adjusted according to the depth of the annular boss 22 entering the guide section 12, thereby adapting to different upsetting requirements and achieving precise forming of the end of the bar stock.

[0079] 5. Final Stage:

[0080] When the end face of the upsetting head 1 touches the limiting end face 24 of the forming die 2, the upsetting head stops moving, completing the upsetting process. At this time, the end of the bar stock has been upset, and the final thickness of the forming head is determined by the material volume and the upsetting pressure.

[0081] Open the forming mold 2 and clamping mold 3, remove the end of the upsetting bar, and complete one upsetting work cycle.

[0082] All parts of the mold are returned to their original positions, ready for the next upsetting operation.

[0083] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0084] The above description of the disclosed embodiments enables those skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A pre-opening and post-closing end upsetting mold for long bars, characterized in that, include: A forming mold (2) and a clamping mold (3) are arranged along the axis of the bar stock (4). Both the forming mold (2) and the clamping mold (3) are two-half split structures, and a continuous through cavity is formed when the mold is closed. The clamping mold (3) is not completely closed when the mold is closed to ensure effective clamping of the bar stock (4). The forming mold (2) is completely closed when the mold is closed to form a through rod forming cavity (21). An annular boss (22) is provided on the end face of the forming mold (2) away from the clamping mold (3). An upsetting head (1) is arranged on the same axis as the forming mold (2). The upsetting head (1) can move along the axial direction. The end of the upsetting head (1) near the forming mold (2) has a head forming cavity. The head forming cavity is composed of two sections. The bottom of the head forming cavity is a head forming section (11) for head forming. The opening of the head forming cavity is a guide section (12). The annular boss (22) of the forming mold (2) can enter the guide section (12) and slide inside it.

2. The pre-opening and post-closing end upsetting mold for long bars according to claim 1, characterized in that, The inner diameter of the forming cavity (21) of the rod is larger than the diameter of the bar (4) to ensure that the radial direction is completely closed when the mold is closed. The forming mold (2) is provided with a transition chamfer (23) on the end face near the upsetting head (1).

3. The pre-opening and post-closing end upsetting mold for long bars according to claim 1, characterized in that, The inner diameter of the guide section (12) of the head forming cavity of the upsetting head (1) is larger than the outer diameter of the annular boss (22) of the forming mold (2), so that the annular boss (22) of the forming mold (2) and the guide section (12) of the head forming cavity of the upsetting head (1) are in a constant small clearance fit. The length of the guide section (12) is equal to the length of the annular boss (22). The outer root of the annular boss (22) is a limiting end face (24). When the end face of the upsetting head (1) touches the limiting end face (24), it stops moving.

4. The pre-opening and post-closing end upsetting mold for long bars according to claim 3, characterized in that, The small clearance fit is 0.1-0.2mm.

5. The pre-opening and post-closing end upsetting mold for long bars according to claim 1, characterized in that, The clamping mold (3) has a two-part split structure and is not completely closed when the mold is closed, which ensures effective clamping of the bar stock (4); the clamping mold (3) is arranged against the forming mold (2), and when the mold is opened, it forms a through channel for the bar stock (4) to be inserted or removed.

6. The pre-opening and post-closing end upsetting mold for long bars according to claim 1, characterized in that, The bar stock (4) stops at the bottom of the head forming cavity of the upsetting head (1) when it passes through the open clamping die (3) and the forming die (2). That is, the distance between the upsetting head (1) and the forming die (2) determines the length of the upsetting material.

7. The pre-opening and post-closing end upsetting mold for long bars according to claim 3, characterized in that, The upsetting head (1) moves forward to begin upsetting. Before the annular boss (22) of the forming die (2) enters the guide section (12) of the head forming cavity, it is an open die forging. After the annular boss (22) of the forming die (2) enters the guide section (12) of the head forming cavity, the head forming cavity of the upsetting head (1) and the end face of the annular boss (22) form a completely closed chamber in the longitudinal and radial directions, i.e., closed die forging. The volume of the chamber is variable and determined by the depth of the annular boss (22) entering the guide section (12) of the head forming cavity. The minimum volume of the chamber is when the end face of the upsetting head (1) stops when it touches the limiting end face (24) of the forming die (2).

8. The pre-opening and post-closing end upsetting mold for long bars according to claim 1, characterized in that, The length of the upsetting material is the same as the volume of the upsetting material. The volume of the material and the upsetting pressure determine the depth of the annular boss (22) entering the head forming cavity, which is the final thickness of the bar stock (4) forming head.

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