A die for reducing the cross-sectional circumference of a pipe blank and a method of machining a pipe blank

Abstract

The present application relates to a kind of mould for reducing the section perimeter of pipe blank and the method for processing pipe blank, including upper die and lower die, the section of upper die includes upper die body and upper die cavity, the section of upper die cavity is arc-shaped curve, the span of curve is equal to the width of upper die body, the section of lower die includes lower die body and lower die cavity, the section of lower die cavity is U-shaped structure, U-shaped structure includes lower die upper mouth and lower die bottom, the two sides of lower die upper mouth are parallel line segment, and lower die bottom is arc-shaped curve A, the span of arc-shaped curve A is equal to the pitch of lower die upper mouth, and equal to the span of curve, the present application also provides the method for processing using the mould.The present application provides a kind of new mould and corresponding processing method, without high-temperature heat treatment, can be processed to pipe blank material and obtain the same metallographic structure.

Description

Technical Field

[0001] This invention relates to a mold for reducing the perimeter of a tube blank cross section and a method for processing tube blanks, belonging to the field of tube blank processing technology. Background Technology

[0002] Tube blanks can fully utilize the rigidity of materials, possessing better bending resistance and safety performance, and are widely used in mechanical structures. Generally, the required cross-sectional perimeter of a tube blank varies at different locations. Currently, several technologies can achieve variations in the cross-sectional perimeter of parts. For example, patent application number 202110664990.9 proposes a method for locally shortening a tube blank. Its drawback is the need for rigid supports inside the tube blank, making it impractical for parts exceeding 1 meter in length, and impossible to implement for parts with curved axes where rigid supports cannot be inserted or removed. Another application, number 202210195399.8, proposes a method for reducing perimeter during heating, but high temperatures significantly impact mold life and operator comfort. Therefore, those skilled in the art have been seeking a method suitable for rapidly reducing the perimeter of tube blanks at room temperature. Summary of the Invention

[0003] This application provides a mold for reducing the perimeter of a tube blank and a method for processing the tube blank; the purpose is to enable the tube blank to be processed to shorten its perimeter at room temperature and without filling the tube blank with support.

[0004] The present invention solves the above-mentioned technical problems through the following technical solution: a mold for reducing the perimeter of a tube blank cross section, comprising an upper mold and a lower mold, wherein the cross section of the upper mold includes an upper mold body and an upper mold cavity, the cross section of the upper mold cavity is an arc-shaped curve, and the span of the curve is equal to the width of the upper mold body; the cross section of the lower mold includes a lower mold body and a lower mold cavity, the cross section of the lower mold cavity is a U-shaped structure, the U-shaped structure includes a lower mold upper opening and a lower mold bottom, the two sides of the lower mold upper opening are parallel line segments, and the lower mold bottom is an arc-shaped curve A, the span of the arc-shaped curve A is equal to the distance between the upper openings of the lower mold and is equal to the span of the curve.

[0005] Based on the above technical solution, this application makes the following improvements and enhancements to the above technical solution: Furthermore, the tangents at both ends of the curve and the arc curve A are parallel to the line segment at the upper opening of the lower mold.

[0006] Furthermore, the span of the curve is not less than the diameter of the tube blank to be processed.

[0007] Furthermore, the mold can be provided with multiple upper mold cavities and / or lower mold cavities with different circumferences along the axial direction.

[0008] The method for machining tube blanks by reducing the cross-sectional perimeter of the tube blank using the mold of the present invention includes the following steps: Step 1: Initial blank selection. Determine the perimeter of each section of the finished part, find the largest perimeter, select the blank based on the largest perimeter, and calculate the radius R of the blank, as well as the thickness t of the blank. Step 2, mold selection: Based on the perimeter L of each part of the finished product, determine the perimeter L0 of the mold cavity section when the upper and lower mold cavities are joined together, where L0 is greater than L; the span of the upper mold cavity is equal to 2R, the span of the lower mold cavity is 2R, the distance between the upper openings of the lower mold cavity is 2R, and the span of the arc curve A at the bottom of the lower mold is 2R. Step 3: Install the upper and lower dies onto the press, and place the tube blank into the lower die cavity; Step 4: Mold closing and extrusion molding.

[0009] The advantage of this application lies in the fact that, through the design of the mold cavity structure, the force on the tube blank during the extrusion operation of the upper and lower molds can be controlled, ensuring that the tube blank fits snugly against the mold cavity after being subjected to force, and that the circumference of each part reaches the designed length. The mold of this application shortens the circumference of the tube blank without internal support and heating, which facilitates engineering implementation. Attached Figure Description

[0010] Figure 1 A three-dimensional structural diagram of a mold used to reduce the perimeter of a tube blank cross section; Figure 2 for Figure 1 A schematic diagram of the cross-sectional structure of the mold cavity shown; Figure 3 A schematic diagram showing the forces acting on a circular tube blank placed inside a mold cavity; Figure 4 This is a schematic diagram of the segmented stress during the tube blank forming process; Figure 5 A schematic diagram showing multiple cross-sections with different perimeters inside the mold cavity; Figure 6 The metallographic structure of the tube blank material processed using the mold of Example 1; Figure 7 for Figure 6 Metallographic structure of tube blank material before processing.

[0011] The markings are as follows: Upper mold -1, upper mold body -1.1, upper mold cavity -1.2, curve -1.21; Lower mold -2, lower mold body -2.1, lower mold bottom -2.22, line segment -2.23; Curved segment S-101, straight segment A-102, straight segment B-103, curved segment G-104. Detailed Implementation

[0012] The following embodiments, in conjunction with the figures, are only for illustrating the technical solutions described in the claims and are not intended to limit the scope of protection of the claims.

[0013] Example 1 Combination Figure 1-2 A mold for reducing the perimeter of a tube blank cross-section includes an upper mold 1 and a lower mold 2. The upper mold 1 has a cross-section comprising an upper mold body 1.1 and an upper mold cavity 1.2. The cross-section of the upper mold cavity 1.2 is an arc-shaped curve 1.21, and the span of the curve 1.21 is equal to the width of the upper mold body 1.1. The lower mold 2 has a cross-section comprising a lower mold body 2.1 and a lower mold cavity 2.2. The cross-section of the lower mold cavity 2.2 is a U-shaped structure, comprising an upper opening 2.21 and a lower mold bottom 2.22. The two sides of the upper opening 2.21 are parallel line segments 2.23. The lower mold bottom 2.22 is an arc-shaped curve A. The span of the arc-shaped curve A is equal to the spacing of the upper opening 2.21 and equal to the span of the curve 1.21. The tangents at the two endpoints of the curve 1.21 and the arc-shaped curve A are parallel to the line segments of the upper opening 2.21. The span of the curve 1.21 is the diameter of the tube blank to be processed.

[0014] The mold can be configured with multiple upper and / or lower cavities with different circumferences along the axial direction to accommodate variations in the axial circumference of the finished product.

[0015] The above-mentioned mold achieves the reduction of the tube blank circumference through the following steps: Step 1: Initial blank selection. Determine the perimeter of each section of the finished part, find the largest perimeter, select the blank based on the largest perimeter, and calculate the radius R of the blank, as well as the thickness t of the blank. Step 2, mold selection: Based on the perimeter L of each section of the finished part, determine the perimeter L0 of the mold cavity section when the upper mold cavity 1.2 and lower mold cavity 2.2 are joined, and L0 is greater than L; the span of the upper mold cavity 1.2 is equal to 2R, the span of the lower mold cavity 2.2 is 2R, the upper opening distance of the lower mold cavity 2.2 is 2R, and the bottom of the lower mold 2.22 is an arc curve A with a span of 2R; Step 3: Install the upper mold 1 and the lower mold 2 onto the press, and place the tube blank into the lower mold cavity 2.2; Step 4: Mold closing and extrusion molding.

[0016] Example 2 Combination Figure 1-5 The implementation process is illustrated using a tube blank as an example.

[0017] Initial blank selection: The perimeter of the blank is determined based on the maximum cross-sectional perimeter of the finished product; the cross-section of the blank is circular with a radius of R and a cross-sectional perimeter of L0; the finished product here refers to the final product to be processed from the blank, such as the B-pillar of a car.

[0018] Combination Figure 1 Mold selection: The mold used to reduce the perimeter of the tube blank cross section consists of two parts: upper mold 1 and lower mold 2. The cross section of the inner surface of upper mold 1 is an arc curve with a span of 2R and a width W of 2R. The cross section of the inner surface of lower mold 2 includes the arc curve A at the bottom and the line segments 2.23 on both sides. The connecting ends of arc curve A and the line segments 2.23 on both sides are connected to form a U-shaped inner surface. Upper mold 1 and lower mold 2 are in contact. Arc curve 1.21, arc curve A, and line segments 2.23 on both sides constitute the entire mold cavity. The curvature centers of curve 1.21 and arc curve A must be located inside the mold cavity, that is, the curves curve outward from the mold cavity. The tangents at the endpoints of curve 1.21 and arc curve A must be parallel to line segment 2.23.

[0019] The two line segments 2.23 are parallel, with a distance of 2R between them. Line segment 2.23 is parallel to the mold closing direction, ensuring that it can move along the mold closing direction within the lower mold cavity. When the end of the arc-shaped curve connects to the upper endpoint of line segment 2.23, the perimeter of the mold cavity cross section formed is greater than L0. The key is to ensure that the billet is always wrapped inside the mold cavity during the perimeter reduction process. When the end of the arc-shaped curve connects to the lower endpoints of the two line segments 2.23, the perimeter of the mold cavity cross section formed is less than L0.

[0020] Combination Figures 2-4 Taking a 1 / 2 tube blank as an example, the mechanical principle of cross-sectional perimeter compression is explained: The upper mold 1 moves downward along the mold closing direction and contacts the tube blank, forming a downward force F1 on the tube blank. At the same time, the lower mold 2 forms an upward force F2 on the tube blank. F1 and F2 widen the tube blank, which in turn causes the side wall of the lower mold 2 (i.e., line segment 2.23) to form a force F3 pointing into the mold cavity on the tube blank. Under the action of forces F1 and F3, the upper arc of the tube blank gradually conforms to curve 1.21 and side wall line segment 2.23. Under the action of forces F2 and F3, the lower part of the tube blank gradually conforms to the curve of the bottom of the lower mold 2.22, and the side of the tube blank conforms to line segment 2.23.

[0021] See Figure 3 and Figure 4The tube is shaped into a tube blank, whose cross-section can be divided into four characteristic parts: curved segment S101, curved segment G104, and straight segments A102 and B103. During compression, the lengths of straight segments A102 and B103 are controlled to be less than 10t0, where t0 is the tube blank wall thickness. When straight segments A102 and B103 are ≤ 10t0, their inherent stiffness ensures that they do not buckle or wrinkle under pressure parallel to their length, thus preventing upsetting and shortening during compression. Because the tangents at the endpoints of straight segments A102 and B103 are parallel to straight segment A102, after complete mold application, the tangents of curved segments S101 and G104 are parallel to straight segment A102. Therefore, the pressure F4 on straight segment A102 is parallel to straight segment A102, allowing for smooth upsetting and shortening during compression. Furthermore, because curved segments S101 and G104 curve outwards from the mold cavity, the reaction force F5 of straight segment A102 on curved segments S101 and G104 pushes the curved segments against the mold cavity, preventing them from leaving it. Under these two conditions, as the upper mold 2 continues to close along the mold closing direction, the tube blank remains close to the mold cavity, and its circumference is successfully shortened, forming the tube blank.

[0022] Multiple cavities of different circumferences can be arranged along the axis of the mold cavity (i.e., the axis of the tube blank), allowing for the reduction of circumferences of different cross-sections in a single mold closing operation. The axial direction of the mold cavity can also be curved. The advantage of this process is that it eliminates the need for additional supports inside the tube blank, greatly simplifying the operation and improving the feasibility of the process.

[0023] like Figure 6 The metallographic structure of the tube blank material processed using the mold and processing method of this application is shown. Figure 7 The image shows the metallographic structure of the tube blank material before processing. It can be seen that before and after using the mold and processing method of this invention, the microstructure remains unchanged, consisting of a large amount of equiaxed ferrite and a small amount of pearlite. This is extremely important for parts requiring subsequent heat treatment, because in practical applications, some areas of the part need to have their perimeter reduced, while other areas do not. If the microstructures of these two areas are inconsistent, corresponding heat treatment parameters need to be formulated separately in subsequent heat treatment processes (such as quenching), which will cause many problems in actual production. Therefore, this invention provides a new mold and corresponding processing method that allows tube blank materials to be processed to obtain the same metallographic structure without high-temperature heat treatment.

[0024] 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, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for machining a tube blank using a mold for reducing the perimeter of the tube blank cross-section, characterized in that, Includes the following steps: Step 1: Initial blank selection. Determine the perimeter of each section of the finished part, find the largest perimeter, select the blank based on the largest perimeter, and calculate the radius R of the blank, as well as the thickness t of the blank. Step 2, mold selection: Based on the perimeter L of each part of the finished product, determine the upper mold cavity (1.2) and lower mold cavity (2.2) of the mold. The perimeter L0 of the mold cavity section when they are joined is greater than L. The span of the upper mold cavity (1.2) is equal to 2R, the span of the lower mold cavity (2.2) is 2R, the upper opening distance of the lower mold cavity (2.2) is 2R, and the bottom of the lower mold (2.22) is an arc curve A with a span of 2R. Step 3: Install the upper die (1) and lower die (2) onto the extruder and place the tube blank into the lower die cavity (2.2); Step 4: Mold closing and extrusion molding; The mold includes an upper mold (1) and a lower mold (2). The upper mold (1) has a cross-section including an upper mold body (1.1) and an upper mold cavity (1.2). The cross-section of the upper mold cavity (1.2) is an arc-shaped curve (1.21), and the span of the curve (1.21) is equal to the width of the upper mold body (1.1). The lower mold (2) has a cross-section including a lower mold body (2.1) and a lower mold cavity (2.2). The cross-section of the lower mold cavity (2.2) is a U-shaped structure. The U-shaped structure includes an upper opening (2.21) and a lower bottom (2.22). The two sides of the upper opening (2.21) are parallel line segments. The lower bottom (2.22) is an arc-shaped curve A. The span of the arc-shaped curve A is equal to the spacing of the upper opening (2.21) and equal to the span of the curve (1.21). The tangents at the two endpoints of the curve (1.21) and the arc curve A are parallel to the line segment of the upper opening (2.21) of the lower mold; The span of the curve (1.21) is not less than the diameter of the tube blank to be processed; The mold can be provided with multiple upper mold cavities and / or lower mold cavities with different circumferences along the axial direction; Based on the perimeter L of each section of the finished part, determine the perimeter L0 of the mold cavity section when the upper mold cavity (1.2) and lower mold cavity (2.2) are connected, where L0 is greater than L; the span of the upper mold cavity (1.2) is equal to 2R, the span of the lower mold cavity (2.2) is 2R, the upper opening distance of the lower mold cavity (2.2) is 2R, and the bottom of the lower mold (2.22) is an arc curve A with a span of 2R.

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