High lock nut structure and method of manufacturing same

Abstract

The application provides a high lock nut structure and a manufacturing method thereof. The high lock nut structure comprises that an inner thread angle of the high lock nut is 15-25 DEG, and a bottom end surface of the inner thread is provided in a circular arc structure, and the high lock nut is made of an aluminum alloy. The high lock nut structure and the manufacturing method thereof introduce residual compressive stress in the transverse and longitudinal directions, effectively improve fatigue strength and stress corrosion resistance of the nut, plastic deformation occurs in inner and outer walls of the nut during the manufacturing process, residual compressive stress is generated in the middle part of the wall thickness, mechanical properties of the nut are significantly enhanced during service, and the nut is suitable for various engineering applications such as high stress and high load; meanwhile, the reduction of the thread angle increases the self-locking ability of the nut to a certain extent, and the purpose of preventing loosening is achieved.

Description

Technical Field

[0001] This application belongs to the field of nut manufacturing and processing technology, and in particular relates to a high-locking nut structure and its manufacturing method. Background Technology

[0002] Traditional high-strength nuts are prone to fatigue failure and stress corrosion cracking under high stress conditions, limiting their use in some important applications. According to current theory, the fatigue crack initiation stage accounts for more than 70% of the fatigue life. Therefore, preventing or delaying the initiation of fatigue cracks is a key factor in improving the fatigue strength and fatigue life of products. Increasing the compressive stress at the fastener thread can effectively improve fatigue strength.

[0003] In addition, among the three conditions for stress corrosion, external tensile stress is the most important factor. By increasing the pre-compression stress, it can be offset by the external tensile stress, thereby improving the stress corrosion resistance to a certain extent.

[0004] Currently, only bolt products have corresponding processes to increase compressive stress, such as rolling and shot peening, which can improve the stress state of bolts and increase compressive stress. However, there is no method to increase the compressive stress of nuts. Summary of the Invention

[0005] In view of this, this application aims to propose a high-lock nut structure and its manufacturing method to solve the problem that traditional high-lock nuts are prone to fatigue failure and stress corrosion failure under high stress conditions, which limits their use.

[0006] To achieve the above objectives, the technical solution of this application is implemented as follows:

[0007] In a first aspect, this application provides a high-locking nut structure, comprising:

[0008] The internal thread helix angle of the high-lock nut is 15° to 25°, and the bottom end face of the internal thread is set with an arc-shaped structure.

[0009] Furthermore, the high-lock nut is made of aluminum alloy.

[0010] Secondly, based on the same inventive concept, this application also provides a method for manufacturing a high-locking nut structure as described in the first aspect, the method comprising:

[0011] For material selection, aluminum alloy was chosen as the raw material for manufacturing high-lock nuts;

[0012] Preforming involves machining raw materials into the shape of a standard nut using CNC turning or upsetting processes.

[0013] Pre-made threads are pre-made according to the tapping method of ordinary nuts, wherein the helix angle of the pre-made threads of ordinary nuts is 30°;

[0014] Lateral pre-stress is applied by grinding the tip of the thread tap into an arc shape, and then screwing it into the pre-made nut so that it completely covers all the nut threads; on the outer wall of the nut, an elastic sleeve is used to form a transition fit with the nut, and lateral compressive stress is applied to the elastic sleeve by external extrusion, causing the nut column to undergo plastic deformation, so that the bottom end face of the nut's internal thread is in an arc shape.

[0015] Longitudinal pre-stress is applied to the nut after it has been prepared by applying transverse compressive stress. The nut is then placed between two parallel pressure surfaces. Longitudinal compressive stress is applied in the plastic deformation range of the nut to cause plastic deformation in the longitudinal direction, so as to ensure that the internal thread helix angle of the nut meets the requirement of 15°~25°.

[0016] For finished product inspection, an X-ray residual stress tester is used to test the residual stress at the midpoint of the line connecting the two closing points of the nut and the residual stress at the closing point.

[0017] Furthermore, during the material selection stage, the selected aluminum alloy material is 7075 aluminum alloy, and the elastic sleeve is made of stainless steel.

[0018] Furthermore, in response to the lateral compressive stress applied to the nut, an elastic washer is provided between the elastic sleeve and the nut. The elastic sleeve is subjected to lateral compressive stress for compression. The nut tap deforms under the external compressive force, generating a reaction force. The outer wall of the nut column is compressed by the elastic sleeve, resulting in inward plastic deformation. The inner wall of the nut undergoes outward plastic deformation due to the compression of the nut tap. During the plastic deformation process, the threaded part of the nut accumulates compressive stress due to the compression deformation. When the preset deformation degree is reached, the external compressive force is removed, the elastic sleeve is reset and separated from the nut column, and then the nut tap is unscrewed, so that the bottom end face of the nut's internal thread is in an arc shape.

[0019] Furthermore, the lateral compressive stress applied to the elastic sleeve ranges from 300 to 500 MPa.

[0020] Furthermore, the elastic gasket is made of 302 or 304 stainless steel and has a strength rating of 700-900 MPa.

[0021] Furthermore, during the longitudinal pre-stressing stage, the applied longitudinal compressive stress is 200–300 MPa.

[0022] Compared with the prior art, the high-locking nut structure and its manufacturing method described in this application have the following advantages:

[0023] The high-locking nut structure and manufacturing method described in this application effectively improve the fatigue strength and stress corrosion resistance of the nut by introducing residual compressive stress in both the transverse and longitudinal directions. During the manufacturing process, the inner and outer walls of the nut undergo plastic deformation, thereby generating residual compressive stress in the middle of the wall thickness. This significantly enhances the mechanical properties of the nut during service and makes it suitable for various engineering applications with high stress and high load. At the same time, the reduction of the thread helix angle increases the self-locking ability of the nut to a certain extent, achieving the purpose of preventing loosening. Attached Figure Description

[0024] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

[0025] Figure 1 This is a schematic diagram of a high-lock nut structure according to an embodiment of this application;

[0026] Figure 2 This is a flowchart illustrating a manufacturing method for a high-lock nut structure as described in an embodiment of this application. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with specific embodiments and the accompanying drawings.

[0028] It should be noted that, unless otherwise defined, the technical or scientific terms used in the embodiments of this application should have the ordinary meaning understood by one of ordinary skill in the art to which this application pertains. The terms "first," "second," and similar terms used in the embodiments of this application do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed after the word and their equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are only used to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0029] Please see Figure 1 As shown, this embodiment provides a high-locking nut structure, including:

[0030] The internal thread helix angle of the high-lock nut is 15° to 25°, and the bottom end face of the internal thread is set with a rounded structure. The high-lock nut is made of aluminum alloy of type 7075.

[0031] Specifically, in this embodiment, the high-lock nut adopts a nut structure with an internal thread helix angle of 15° to 25° and an arc-shaped bottom end face of the internal thread. Compared with the traditional high-lock nut, reducing the internal thread helix angle from 30° to 15° to 25° can improve the self-locking and anti-loosening properties of the high-lock nut. At the same time, setting the bottom of the internal thread to an arc shape can reduce stress concentration at the root of the thread and increase the fatigue strength of the thread.

[0032] The high-strength locking nut structure described in this embodiment has high fatigue strength and resistance to stress corrosion, making it suitable for engineering applications under high stress, high load, and stress corrosion environments.

[0033] Based on the same inventive concept, such as Figure 2 As shown, this embodiment also provides a method for manufacturing a high-locking nut structure, the method comprising:

[0034] Step S101: Material selection. Aluminum alloy material is selected as the raw material for manufacturing high-lock nuts.

[0035] Specifically, in the material selection stage, high-strength and corrosion-resistant aluminum alloy is selected as the raw material for the high-locking nut, such as 7075 aluminum alloy. At the same time, a stainless steel elastic sleeve is selected to apply lateral pre-compression stress to the nut.

[0036] Step S102: Pre-forming, the raw material is processed into the shape of a common nut by CNC turning or upsetting.

[0037] Step S103: Pre-fabricate the thread. Pre-fabricate the thread according to the tapping method of a regular nut, wherein the helix angle of the pre-fabricated thread of a regular nut is 30°.

[0038] Step S104: Apply transverse pre-compression stress. Grind the tip of the thread tap into an arc shape and then screw it into the pre-made nut so that it completely covers all the nut threads. On the outer wall of the nut, use the elastic sleeve to form a transition fit with the nut. Apply transverse compressive stress to the elastic sleeve by external extrusion. The nut column will undergo plastic deformation, so that the bottom end face of the nut's internal thread will be arc-shaped.

[0039] Specifically, the tip of a thread tap (of the same specification and model as the tap used for prefabricated threads) is ground into an arc shape, and then slowly screwed into the prefabricated nut so that it completely covers all the nut threads. An elastic sleeve is used on the outer wall of the nut to create a transition fit between the sleeve and the nut. The elastic deformation range of the sleeve is set so that after being deformed by compression, it can still return to its original shape in a short time, thus achieving the purpose of disassembly and repeated use. By applying external pressure (the lateral compressive stress applied to the elastic sleeve ranges from 300 to 500 MPa), pressure is applied to the elastic sleeve, causing plastic deformation of the nut cylinder it encloses. Due to the fit between the internal thread and the tap, during the extrusion process, the nut tap generates a reaction force against the external pressure. At this time, the nut cylinder will be subjected to pressure in two directions, resulting in plastic deformation. The outer wall of the nut is compressed inward by the elastic sleeve, while the inner wall of the nut (i.e., the thread) undergoes outward plastic deformation due to the compression of the tap. During the plastic deformation process, compressive stress accumulates in the threaded part of the nut due to the extrusion deformation. When the specified deformation degree is reached, the external extrusion pressure is released, the elastic sleeve returns to its original shape and separates from the nut cylinder, and then the tap is slowly unscrewed. Since the tap tip has been ground flat, the bottom of the nut thread will also have an arc shape. During this process, a suitable mold should be set around the outer wall of the nut to ensure the nut's geometry during the extrusion process.

[0040] Step S105: Apply longitudinal pre-compressive stress. Place the nut prepared by applying transverse compressive stress between two parallel pressure surfaces. Apply longitudinal compressive stress in the plastic deformation range of the nut to cause plastic deformation in the longitudinal direction, so as to ensure that the internal thread helix angle of the nut meets the requirement of 15°~25°.

[0041] Specifically, the nut prepared in step S104 is further processed by placing it between two parallel pressure surfaces and applying longitudinal compressive stress (200-300 MPa) to the plastic deformation range of the nut, causing slight plastic deformation in the longitudinal direction. The degree of deformation can be selected according to the requirements of the locking torque, and it is recommended to use 1% to 10% to ensure that the helix angle of the internal thread meets 15° to 25°.

[0042] Step S106: Finished product inspection. Use an X-ray residual stress tester to test the residual stress at the midpoint of the line connecting the two closing points of the nut and the residual stress at the closing point.

[0043] High-strength lock nuts that meet the requirements after inspection will proceed to the next step, while those that do not meet the preset standards will be transferred to the scrap area for further centralized processing.

[0044] In some implementations, when applying lateral prestress to the nut, an elastic washer is required between the elastic sleeve and the nut. The elastic washer is made of 302 or 304 stainless steel and has a strength rating of 700 to 900 MPa to meet the requirements of compressing the nut.

[0045] It should be noted that by using the interference screw-in extrusion molding method, pre-compression stress is introduced into the internal thread area of ​​the nut. This method can be controlled by the operator by setting a set of process parameters in advance or by setting them based on work experience, so as to ensure that the internal thread part of the nut is uniformly compressed without compromising its functionality.

[0046] Meanwhile, during the extrusion process, the outer wall of the nut is fixed by the mold to ensure that both the inner and outer walls undergo plastic deformation during the extrusion process, thereby generating residual compressive stress in the middle part of the wall thickness.

[0047] Nuts manufactured using the above methods incorporate residual compressive stress in both the transverse and longitudinal directions to improve their fatigue strength and resistance to stress corrosion. During manufacturing, both the inner and outer walls undergo plastic deformation, resulting in residual compressive stress in the middle of the wall thickness. This significantly enhances the mechanical properties of the nut during service, making it suitable for various engineering applications involving high stress and high loads. Simultaneously, the reduction in the thread helix angle increases the nut's self-locking capability to a certain extent, achieving the purpose of preventing loosening.

[0048] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered within the scope of the claims and specification of the present invention.

[0049] The embodiments of this application are intended to cover all such substitutions, modifications, and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the embodiments of this application should be included within the protection scope of this application.

Claims

1. A method for manufacturing a high-locking nut structure, characterized in that, The internal thread helix angle of the high-lock nut is 15°~25°, and the bottom end face of the internal thread is set with an arc-shaped structure. The method includes: For material selection, aluminum alloy was chosen as the raw material for manufacturing high-lock nuts; Preforming involves machining raw materials into the shape of a standard nut using CNC turning or upsetting processes. Pre-made threads are pre-made according to the tapping method of ordinary nuts, wherein the helix angle of the pre-made threads of ordinary nuts is 30°; Lateral pre-stress is applied by grinding the tip of the thread tap into an arc shape, and then screwing it into the pre-made nut so that it completely covers all the nut threads; on the outer wall of the nut, an elastic sleeve is used to form a transition fit with the nut, and lateral compressive stress is applied to the elastic sleeve by external extrusion, causing the nut column to undergo plastic deformation, so that the bottom end face of the nut's internal thread is in an arc shape. Longitudinal pre-stress is applied to the nut after it has been prepared by applying transverse compressive stress. The nut is then placed between two parallel pressure surfaces. Longitudinal compressive stress is applied in the plastic deformation range of the nut to cause plastic deformation in the longitudinal direction, so as to ensure that the internal thread helix angle of the nut meets the requirement of 15°~25°. For finished product inspection, an X-ray residual stress tester is used to test the residual stress at the midpoint of the line connecting the two closing points of the nut and the residual stress at the closing point.

2. The manufacturing method of a high-locking nut structure according to claim 1, characterized in that: The high-lock nut is made of aluminum alloy.

3. The manufacturing method of a high-locking nut structure according to claim 1, characterized in that: During the material selection phase, the selected aluminum alloy material was 7075 aluminum alloy, and the elastic sleeve was made of stainless steel.

4. The manufacturing method of a high-locking nut structure according to claim 1, characterized in that: In response to the lateral compressive stress applied to the nut, an elastic washer is placed between the elastic sleeve and the nut. The elastic sleeve is subjected to lateral compressive stress, and the nut tap deforms under the external compressive force, generating a reaction force. The outer wall of the nut column is compressed by the elastic sleeve, resulting in inward plastic deformation. The inner wall of the nut undergoes outward plastic deformation due to the compression of the nut tap. During the plastic deformation process, the threaded part of the nut accumulates compressive stress due to the compression deformation. When the preset deformation degree is reached, the external compressive force is released, the elastic sleeve is reset and separated from the nut column, and then the nut tap is unscrewed, so that the bottom end face of the nut's internal thread is arc-shaped.

5. The manufacturing method of a high-locking nut structure according to claim 4, characterized in that: The lateral compressive stress applied to the elastic sleeve ranges from 300 to 500 MPa.

6. The manufacturing method of a high-locking nut structure according to claim 4, characterized in that: The elastic gasket is made of 302 or 304 stainless steel and has a strength rating of 700-900 MPa.

7. The manufacturing method of a high-locking nut structure according to claim 1, characterized in that: During the longitudinal pre-stressing stage, the applied longitudinal compressive stress is 200~300 MPa.

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