Countersunk head square neck bolt machining process

Abstract

The countersunk head square neck bolt machining technology comprises the following steps that S1, material cutting is conducted, specifically, a cylindrical metal raw material is cut into a specified length; s2, cold heading a thread part at the lower end of the workpiece; s3, the square neck part of the workpiece is subjected to cold heading, and the first transition taper between the square neck part and the countersunk head part at the top of the workpiece is set to be 40-60 degrees; s4, the countersunk head part of the workpiece is subjected to cold heading, and the second transition taper between the countersunk head part and the square neck part ranges from 80 degrees to 100 degrees; the die further comprises a bottom die used for cold heading of the countersunk head part and the square neck part, the bottom of the bottom die is a square section matched with the square neck part, and air holes are formed in the top corners of the square section in a penetrating mode. The countersunk head square neck bolt is subjected to cold heading for several times, different molds are adopted, different transition tapers are set, materials are uniform in stress, smooth in flowing and not prone to cracks or fractures, the air holes are formed in the four corners of the square neck of the bottom mold to release stress and exhaust air, and the risk of mold explosion of the bottom mold is avoided.

Description

Technical Field

[0001] The present application relates to the technical field of bolt processing, and in particular to a processing technology for countersunk square neck bolts. Background Art

[0002] Countersunk square neck bolt is a special type of bolt, often used in situations where connection and tightening are required and the bolt head does not protrude from the surface. The bolt head is countersunk, similar to a smooth round countersunk with a square neck below, which can be embedded in the corresponding groove to prevent the bolt from rotating. Conical or flat cylindrical, the bolt head can be completely embedded in the workpiece surface to ensure flatness after connection; there is a square neck below the countersunk head, which can be embedded in the corresponding groove to prevent the bolt from rotating.

[0003] In the prior art, countersunk bolts are usually processed and manufactured using cold heading technology to reduce production costs due to their relatively complex structure. However, the currently commonly used cold heading process directly processes countersunk square neck bolts in one go, which has the following defects: the four sides of the square neck of the bottom die are subjected to relatively large pressure at the entrance, so the bottom die is usually made of more expensive tungsten steel, but the hardness of tungsten steel material is too high and it is easy to explode the die. In addition, the four corners of the square neck and the transition between the square neck and the countersunk are prone to cracks or fractures during cold heading, causing damage to the workpiece.

[0004] Therefore, the inventor is necessary to design a new countersunk square neck bolt processing technology to overcome the above problems. Summary of the invention

[0005] The main purpose of the present application is to provide a countersunk square neck bolt processing technology to solve the problems of bottom die explosion and easy cracking of the workpiece during one-time cold heading of countersunk square neck bolts in the related art.

[0006] In order to achieve the above-mentioned purpose, the present application provides a countersunk square neck bolt processing process, comprising the following steps: S1, cutting, cutting the cylindrical metal raw material into a specified length; S2, cold heading the threaded portion at the lower end of the workpiece; S3, cold heading the square neck portion of the workpiece, and setting the first transition taper between the square neck portion and the countersunk head portion at the top of the workpiece to 40° to 60°; S4, cold heading the countersunk head portion of the workpiece, and setting the second transition taper range between the countersunk head portion and the square neck portion to 80° to 100°; and also comprising a bottom die for cold heading the countersunk head portion and the square neck portion, the bottom of the bottom die being a square section adapted to the square neck portion, and air holes being opened through the top corners of the square section.

[0007] Optionally, step S2 includes: the threaded portion includes a threaded shaft segment, a transition shaft segment and an optical axis segment, and an auxiliary conical surface is provided between the optical axis segment and the portion to be processed above the optical axis segment.

[0008] Optionally, the angle between the auxiliary conical surface and the top surface of the optical axis segment is 15°.

[0009] Optionally, the first transition taper in step S3 is 50°.

[0010] Optionally, in step S4, the second transition taper is 90°.

[0011] Optionally, the air holes on the bottom mold are arranged in a horizontal direction.

[0012] Optionally, the base mold is made of high-speed steel, and the hardness of the base mold is 60-62HRC.

[0013] Optionally, the portion to be processed is conical, and the cone angle of the portion to be processed ranges from 10° to 30°.

[0014] Optionally, it also includes a pier detachably connected to the bottom mold, the bottom mold is a truncated cone, and the pier is provided with a mounting groove adapted to the bottom mold.

[0015] The present invention provides a processing technology for countersunk square neck bolts, which has the following beneficial effects compared with the prior art:

[0016] By cold heading the countersunk square neck bolts in batches, using different dies and setting different transition tapers, the material is evenly stressed and flows smoothly during the cold heading process, so the workpiece is not prone to cracks or breakage. In addition, air holes are set at the four corners of the square neck of the bottom die to release stress and exhaust air, effectively avoiding the risk of bottom die explosion. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The drawings constituting a part of this application are used to provide a further understanding of this application, so that other features, purposes and advantages of this application become more obvious. The schematic embodiment drawings and their descriptions of this application are used to explain this application and do not constitute an improper limitation on this application. In the drawings:

[0018] Figure 1 It is the overall structural diagram of the present invention;

[0019] Figure 2 It is a structural diagram of the workpiece after step S1 of the present invention is completed;

[0020] Figure 3 It is a workpiece structure diagram after step S2 of the present invention is completed;

[0021] Figure 4 It is a workpiece structure diagram after step S3 of the present invention is completed;

[0022] Figure 5 It is a workpiece structure diagram after step S4 of the present invention is completed;

[0023] Figure 6 It is a structural diagram of the bottom mold and pier of the present invention.

[0024] Among them: 1. threaded part; 101. threaded shaft section; 102. transition shaft section; 103. smooth shaft section; 2. square neck; 3. countersunk head; 4. bottom mold; 5. air hole; 6. auxiliary cone surface; 7. pier; 8. installation groove. DETAILED DESCRIPTION

[0025] In order to enable those skilled in the art to better understand the solution of the present application, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present application.

[0026] It should be noted that the terms "first", "second", etc. in the specification of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequential order. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present application described here. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device comprising a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0027] In the present application, the terms "upper", "lower", "left", "right", "front", "back", "top", "bottom", "inner", "outer", "middle", "vertical", "horizontal", "lateral", "longitudinal" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings. These terms are mainly used to better describe the present application and its embodiments, and are not used to limit the indicated devices, elements or components to have a specific orientation, or to be constructed and operated in a specific orientation.

[0028] In addition, some of the above terms may be used to express other meanings in addition to indicating orientation or positional relationship. For example, the term "on" may also be used to express a certain dependency or connection relationship in some cases. For those of ordinary skill in the art, the specific meanings of these terms in this application can be understood according to specific circumstances.

[0029] In addition, the term "plurality" shall mean two or more.

[0030] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0031] like Figures 1 to 6 As shown, a processing technology for countersunk square neck bolts includes the following steps: S1, cutting, cutting cylindrical metal raw materials into specified lengths; S2, cold heading the threaded portion 1 at the lower end of the workpiece; S3, cold heading the square neck portion 2 of the workpiece, and setting the first transition taper between the square neck portion 2 and the countersunk portion 3 at the top of the workpiece to 40° to 60°; S4, cold heading the countersunk portion 3 of the workpiece, and setting the second transition taper between the countersunk portion 3 and the square neck portion 2 to 80° to 100°; and also includes a bottom die 4 for cold heading the countersunk portion 3 and the square neck portion 2, the bottom of the bottom die 4 being a square segment matched with the square neck portion 2, and air holes 5 are opened through the top corners of the square segment. Specifically, in this embodiment, the workpiece is cold headed in batches, and the threaded portion 1 at the lower end of the workpiece is first processed (the threaded portion 1 here is in the shape of a bare rod, and the screw is processed later). After the threaded portion 1 is processed, the square neck 2 and the countersunk head 3 are cold headed upward. Two different molds are required here. The mold for processing the square neck 2 processes the transition taper between the square neck 2 and the countersunk head 3 to 40° to 60° (the transition taper refers to the angle or slope of a conical structure used to achieve a gradual transition between two cross-sections in the design of molds or mechanical parts. It is a geometric feature, usually used to connect areas of different diameters or shapes to optimize the flow and stress distribution of the material). The transition taper here is only a preparatory step before the processing of step S4. Pre-processing the transition taper to 40° to 60° can make the material flow on the metal bolt workpiece smooth and the force even when cold heading the countersunk head 3, and it is not easy to crack or break. It should be noted that during cold heading, the stress at the four corners of the square neck 2 of the mold is too large. The design of the air hole 5 can facilitate the discharge of gas and reduce the influence of gas on the cold heading effect. Secondly, it can be used as a stress groove to release stress, so that the square neck 2 of the mold is not easy to crack due to excessive stress, that is, it is not easy to explode. In this embodiment, the countersunk square neck bolts are cold headed in batches, different molds are used, and different transition tapers are set, so that the workpiece is evenly stressed and flows smoothly during the cold heading process, so the workpiece is not easy to crack or break. In addition, air holes 5 are set at the four corners of the square neck of the bottom mold 4 to release stress and exhaust air, effectively avoiding the risk of explosion of the bottom mold 4.

[0032] Step S2 includes: the threaded portion 1 includes a threaded shaft section 101, a transition shaft section 102 and an optical shaft section 103, and an auxiliary conical surface 6 is provided between the optical shaft section 103 and the portion to be processed above the threaded portion 101. The angle between the auxiliary conical surface 6 and the top surface of the optical shaft section 103 is 15°. Specifically, the auxiliary conical surface 6 is a preparatory operation for step S3, and the lower end of the unprocessed portion of the workpiece is first processed into a cone, and the bottom surface is not cold-forged to a flat state, so that the bottom of the square neck 2 and the intersection of the optical shaft section 103 are not prone to cracks or fractures. When different molds are used in step S3, the pressure direction of cold forging is changed, thereby making the workpiece less prone to cracks.

[0033] The first transition taper in step S3 is 50°. Specifically, this is a more appropriate first transition taper. Under this taper, the material flow direction between the workpiece and the bottom mold 4 in step S4 is smooth, and the stress magnitude at each location is relatively uniform.

[0034] The second transition taper in step S4 is 90°. Specifically, this is the final transition taper between the countersunk head 3 and the square neck 2. Under this taper, the stress of the countersunk square neck bolt in actual use is more uniform, and the workpiece life is longer.

[0035] The air holes 5 on the bottom mold 4 are arranged in the horizontal direction. Specifically, according to the actual situation, the horizontal direction is convenient for processing, and other angles can also be processed, which will not be described here.

[0036] The bottom die 4 is made of high-speed steel, and the hardness of the bottom die 4 is 60-62HRC. Specifically, since the present embodiment adopts the processing technology of cold heading in stages, the hardness of the material of the bottom die 4 can be appropriately reduced, and the low-cost high-speed steel can meet the demand, and the risk of die explosion can also be reduced.

[0037] The part to be processed is conical, and the range of the cone angle of the part to be processed is 10° to 30°. Specifically, setting the part to be processed as a cone can make the material flow smooth during the subsequent cold heading of the part to be processed, and the stress at each location is uniform.

[0038] It also includes a pier 7 detachably connected to the bottom mold 4, the bottom mold 4 is a truncated cone, and the pier 7 is provided with a mounting groove 8 adapted to the bottom mold 4. Specifically, the bottom mold 4 needs to be replaced regularly due to the high number of working times, and the replacement is facilitated by a detachable manner.

[0039] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A process for processing countersunk square neck bolts, characterized in that: The following steps are involved: S1. Cutting: cutting cylindrical metal raw materials into specified lengths; S2, a threaded portion (1) at the lower end of the cold-forged workpiece; S3, cold heading the square neck portion (2) of the workpiece, and setting the first transition taper between the square neck portion (2) and the countersunk head portion (3) at the top of the workpiece to 40° to 60°; S4, cold heading the countersunk head portion (3) of the workpiece, and setting the second transition taper between the countersunk head portion (3) and the square neck portion (2) to a range of 80° to 100°; It also includes a bottom die (4) for cold heading the countersunk head portion (3) and the square neck portion (2); the bottom of the bottom die (4) is a square segment that matches the square neck portion (2); and air holes (5) are provided through the top corners of the square segment.

2. A process for processing countersunk square neck bolts as claimed in claim 1, characterized in that: Step S2 comprises: the threaded portion (1) comprises a threaded shaft segment (101), a transition shaft segment (102) and an optical shaft segment (103), and an auxiliary conical surface (6) is provided between the optical shaft segment (103) and the portion to be processed above it.

3. A process for processing countersunk square neck bolts as claimed in claim 3, characterized in that: The included angle between the auxiliary conical surface (6) and the top surface of the optical axis segment (103) is 15°.

4. A process for processing countersunk square neck bolts as claimed in claim 1, characterized in that: The first transition taper in step S3 is 50°.

5. A process for processing countersunk square neck bolts as claimed in claim 1, characterized in that: In step S4, the second transition taper is 90°.

6. A process for processing countersunk square neck bolts as claimed in claim 1, characterized in that: The air holes (5) on the bottom mold (4) are arranged in a horizontal direction.

7. A process for processing countersunk square neck bolts as claimed in claim 1, characterized in that: The material of the bottom mold (4) is high-speed steel, and the hardness of the bottom mold (4) is 60-62HRC.

8. A process for processing countersunk square neck bolts as claimed in claim 2, characterized in that: The portion to be processed is conical, and the cone angle of the portion to be processed ranges from 10° to 30°.

9. A process for processing countersunk square neck bolts as claimed in claim 1, characterized in that: It also comprises a pier (7) detachably connected to the bottom mold (4); the bottom mold (4) is a truncated cone; and the pier (7) is provided with a mounting groove (8) adapted to the bottom mold (4).

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