A type of hexagonal cylindrical head screw with corrosion-resistant connection.

Abstract

This utility model discloses a hexagonal cylindrical head screw with corrosion-resistant joints, relating to the technical field of hexagonal cylindrical head screws. The screw includes a cylindrical smooth section and a threaded section. The surface of the threaded section is sequentially covered from the inside out with a bottom chemical conversion film, an intermediate alloy plating layer, and an outer polymer sealing layer. The thickness of the bottom chemical conversion film, intermediate alloy plating layer, and outer polymer sealing layer is greater at the thread crest than at the thread root, forming a stepped protective structure. This utility model significantly improves the screw's corrosion resistance, connection reliability, and the safety and convenience of installation by setting a stepped protective structure and microgrooves filled with solid corrosion inhibitor on the threaded surface, combined with the hexagonal hole and anti-slip texture design at the top of the cylindrical section.

Description

Technical Field

[0001] This utility model relates to the technical field of hexagonal cylindrical head screws, and in particular to a hexagonal cylindrical head screw with corrosion resistance at the connection point. Background Technology

[0002] In existing fastener technology, hexagonal head screws are widely used in machinery manufacturing, construction engineering, transportation, and other fields. Especially in highly corrosive environments such as marine environments, chemical equipment, and bridge structures, higher requirements are placed on the corrosion resistance of these screws. Traditional hexagonal head screws typically rely on only a single plating or coating for corrosion protection, which has limited protective capabilities. Particularly in humid, salt spray, or chemically corrosive environments, problems such as plating peeling, localized corrosion, and connection failure can easily occur, affecting the screw's service life and connection reliability.

[0003] Furthermore, conventional screws lack effective barriers against the intrusion of corrosive media in their structural design and fail to consider the sealing of the connection interface, allowing corrosive liquids to easily seep into the joint gaps and accelerate the oxidation and damage of the metal substrate. Simultaneously, during installation, due to unreasonable head structure design, slippage and uneven force application occur, reducing operational safety and efficiency.

[0004] Therefore, there is an urgent need for a hexagonal cylindrical head screw with a reasonable structure, multiple protective layers, and multiple anti-corrosion functions to meet the high-strength and long-life connection requirements under complex working conditions. Utility Model Content

[0005] This application aims to at least address the problems of insufficient corrosion resistance, poor sealing performance, and inconvenient installation and operation of traditional hexagonal head screws in highly corrosive environments. Therefore, this application proposes a hexagonal head screw with corrosion-resistant joints.

[0006] This utility model provides a hexagonal cylindrical head screw with corrosion resistance at the connection point, including a cylindrical smooth section and a threaded section. The surface of the threaded section is covered from the inside out with a bottom chemical conversion film, an intermediate alloy plating layer and an outer polymer sealing layer. The thickness of the bottom chemical conversion film, the intermediate alloy plating layer and the outer polymer sealing layer at the crest of the thread is greater than that at the root of the thread, forming a stepped protective structure.

[0007] Preferably, the threaded portion has microgrooves on its tooth flanks, and the microgrooves are filled with a solid corrosion inhibitor.

[0008] Preferably, the pressure-bearing surface of the cylindrical part is provided with an annular sealing groove, and an elastic sealing ring is embedded in the groove.

[0009] Preferably, the surface of the smooth rod section is provided with a spiral guide groove, the depth of which is 0.1-0.3mm.

[0010] Preferably, the underlying chemical conversion film is a zirconium-based passivation film with a thickness of 0.5-2 μm and a surface with nanoscale pores.

[0011] Preferably, the intermediate alloy coating is a zinc-nickel alloy layer with a nickel content of 12-15 wt% and a thickness of 8-15 μm.

[0012] Preferably, the outer polymer sealing layer is a composite material of fluorinated resin and nano-ceramic particles, with a thickness of 3-8 μm.

[0013] Preferably, the microgrooves are 10-30 μm deep and are distributed in a spiral shape on the side of the thread.

[0014] Preferably, the solid corrosion inhibitor is composed of benzotriazole and silicate.

[0015] Preferably, the top of the cylindrical part is provided with a hexagonal hole for accommodating a screwdriver, and the cylindrical part is uniformly distributed with raised anti-slip textures along the circumference.

[0016] This utility model provides a hexagonal cylindrical head screw with corrosion resistance at the connection point, which, compared with the prior art:

[0017] 1. This utility model effectively improves the corrosion resistance of the threaded portion by sequentially forming a bottom chemical conversion film, an intermediate alloy plating layer, and an outer polymer sealing layer on the threaded surface from the inside out, and employing a stepped protective structure where the thickness at the crest of the thread is greater than that at the root of the thread. Simultaneously, microgrooves filled with solid corrosion inhibitors are formed on the thread flanks, further enhancing local protection capabilities and delaying the erosion of the metal substrate by corrosive media in complex environments, significantly improving the screw's service life and connection reliability. Furthermore, the hexagonal hole at the top of the cylindrical portion, combined with circumferential anti-slip textures, not only facilitates tool application but also effectively prevents slippage, improving installation efficiency and operational safety.

[0018] 2. This invention, by setting spiral guide grooves on the surface of the smooth rod section, helps to guide water to drain quickly in humid or corrosive environments, avoiding localized corrosion caused by liquid retention. The annular sealing groove and embedded elastic sealing ring on the bearing surface of the cylindrical section achieve a sealing function between the connecting surfaces, preventing external corrosive media from seeping into the connection gaps, thus forming a multi-level, three-dimensional anti-corrosion system. The various functional structures work together to meet both the requirements of high-strength connections and the stability of long-term use, making it particularly suitable for highly corrosive industrial fields such as marine, chemical, and bridge manufacturing, and possessing good application prospects and promotional value. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of this utility model, the drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this utility model and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained from these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the overall structure of an embodiment of the present utility model;

[0021] Figure 2 This is a top view of the overall structure of an embodiment of the present utility model;

[0022] Figure 3 This is a side view of the overall structure of an embodiment of the present utility model;

[0023] Figure 4 The following is an embodiment of this utility model Figure 3 A structural cross-sectional view of AA;

[0024] Figure 5 This is an embodiment of the present utility model. Figure 4 A schematic diagram of the structure at point A;

[0025] Figure 6 This is a side view of the cylindrical part structure according to an embodiment of the present utility model;

[0026] Figure 7 The following is an embodiment of this utility model Figure 6 Schematic diagram of the structure at BB.

[0027] Figure label:

[0028] 1. Cylindrical section; 2. Smooth section; 3. Threaded section; 4. Microgroove; 5. Solid corrosion inhibitor; 6. Flow channel; 7. Hexagonal hole; 8. Anti-slip texture; 9. Outer polymer sealing layer; 10. Intermediate alloy plating layer; 11. Bottom chemical conversion film; 12. Sealing ring. Detailed Implementation

[0029] The following detailed description, in conjunction with the accompanying drawings, outlines some embodiments of the present invention. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0030] Please refer to Figures 1-7 This utility model provides a hexagonal cylindrical head screw with corrosion-resistant connection, comprising a cylindrical part 1, a smooth shank section 2 and a threaded part 3 connected in sequence. The overall structure is reasonably designed and suitable for fastening connections in highly corrosive environments.

[0031] The surface of the threaded portion 3 is sequentially provided with a bottom chemical conversion film 11, an intermediate alloy plating layer 10, and an outer polymer sealing layer 9 from the inside out. The bottom chemical conversion film 11 is preferably a zirconium-based passivation film with a thickness controlled within the range of 0.5–2 μm and a surface with nanoscale pores, which is beneficial for improving the adhesion of subsequent plating layers. The intermediate alloy plating layer 10 is a zinc-nickel alloy layer with a nickel content of 12–15 wt% and a thickness ranging from 8–15 μm, exhibiting good corrosion resistance and machinability.

[0032] The outer polymer sealing layer 9 is a dense coating composed of fluorinated resin and nano-ceramic particles, with a thickness of 3–8 μm, exhibiting excellent sealing performance and wear resistance. The total thickness of the above three layers at the thread crest is greater than that at the thread root, forming a stepped protective structure that effectively enhances the corrosion resistance of critical thread components.

[0033] Furthermore, microgrooves 4 are provided on the thread flank, and the microgrooves 4 are spirally distributed on the thread flank with a depth of 10-30 μm. The microgrooves 4 are filled with a solid corrosion inhibitor 5, which is composed of benzotriazole and silicate. It can be slowly released during use to continuously protect the metal surface and improve the long-term corrosion resistance of the screw in humid or salt spray environments.

[0034] In terms of structural design, the top of the cylindrical part 1 is provided with a hexagonal hole 7 for use with a screwdriver to achieve tightening or disassembly operations. Simultaneously, the cylindrical part 1 is uniformly provided with raised anti-slip grooves 8 along its circumference to increase friction during force application, prevent tool slippage, and improve installation efficiency and operational safety. Furthermore, the pressure-bearing surface of the cylindrical part 1 is provided with an annular sealing groove, in which an elastic sealing ring 12 is embedded. This provides a sealing function at the connection interface after the screw is tightened, preventing corrosive media from seeping in through the connection gap.

[0035] To further improve drainage and corrosion resistance, the outer surface of the bare rod section 2 is provided with a spiral guide groove 6 with a depth of 0.1 to 0.3 mm, which helps to guide external water to drain quickly along the spiral direction and avoid liquid accumulation leading to local corrosion.

[0036] In summary, the working principle of the hexagonal cylindrical head screw with corrosion-resistant connection in this embodiment of the present invention is as follows: A bottom chemical conversion film 11, an intermediate alloy plating layer 10, and an outer polymer sealing layer 9 are sequentially formed from the inside to the outside on the surface of the thread portion 3. A stepped protective structure with a thickness greater at the crest of the thread than at the root of the thread is adopted to form a multi-level anti-corrosion system, which enhances the adhesion of the plating while improving the corrosion resistance of key parts. The thread facets are provided with spirally distributed microgrooves 4, filled with a solid corrosion inhibitor 5 composed of benzotriazole and silicate, which can be slowly released during use. The design enhances the long-term protection of the metal substrate. The hexagonal hole 7 at the top of the cylindrical part 1, combined with the circumferential anti-slip texture 8, improves the operational stability and efficiency during installation. The annular sealing groove of the elastic sealing ring 12 is embedded on the pressure-bearing surface, which achieves the sealing function of the connection interface after the screw is tightened, preventing the infiltration of corrosive media. The spiral guide groove 6 set on the surface of the smooth rod section 2 helps the external moisture to drain quickly, avoiding liquid retention that could cause local corrosion. The overall structure, through the synergistic effect of multiple protection mechanisms, significantly improves the service life, connection reliability, and sealing performance of the screw in highly corrosive environments.

[0037] The above are merely preferred embodiments of this utility model and are not intended to limit the scope of this utility model. Various modifications and variations can be made to this utility model by those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of this utility model should be included within the protection scope of this utility model.

Claims

1. A hexagonal cylindrical head screw having corrosion resistance at a joint, characterized by: It includes a cylindrical part (1), a smooth rod section (2) and a threaded part (3). The surface of the threaded part (3) is covered from the inside to the outside with a bottom chemical conversion film (11), an intermediate alloy plating layer (10) and an outer polymer sealing layer (9). The thickness of the bottom chemical conversion film (11), the intermediate alloy plating layer (10) and the outer polymer sealing layer (9) at the top of the thread is greater than that at the bottom of the thread, forming a stepped protective structure.

2. The corrosion resistant connection of a hexagonal cylindrical head screw according to claim 1, characterized in that: The threaded portion (3) has microgrooves (4) on its tooth surface, and the microgrooves (4) are filled with solid corrosion inhibitors (5).

3. The corrosion resistant connection of a hexagonal cylinder head screw according to claim 2, characterized in that: The cylindrical part (1) has an annular sealing groove on its pressure-bearing surface, and an elastic sealing ring (12) is embedded in the groove.

4. The hexagonal head screw with corrosion resistance at the connection point according to claim 3, characterized in that: The surface of the smooth rod section (2) is provided with a spiral guide groove (6), the guide groove (6) being 0.1-0.3mm deep.

5. The hexagonal head screw with corrosion resistance at the connection point according to claim 1, characterized in that: The underlying chemical conversion film (11) is a zirconium-based passivation film with a thickness of 0.5-2 μm and nanoscale pores on its surface.

6. The hexagonal head screw with corrosion resistance at the connection point according to claim 5, characterized in that: The intermediate alloy coating (10) is a zinc-nickel alloy layer with a nickel content of 12-15wt% and a thickness of 8-15μm.

7. The hexagonal head screw with corrosion resistance at the connection point as described in claim 6, characterized in that: The outer polymer sealing layer (9) is a composite material of fluorinated resin and nano-ceramic particles, with a thickness of 3-8 μm.

8. The hexagonal head screw with corrosion resistance at the connection point according to claim 2, characterized in that: The microgrooves (4) are 10-30 μm deep and are distributed in a spiral shape on the side of the thread.

9. The hexagonal head screw with corrosion resistance at the connection point as described in claim 8, characterized in that: The solid corrosion inhibitor (5) is composed of benzotriazole and silicate.

10. The hexagonal head screw with corrosion resistance at the connection point according to claim 1, characterized in that: The cylindrical part (1) has a hexagonal hole (7) at the top for accommodating a screwdriver, and the cylindrical part (1) has raised anti-slip textures (8) evenly distributed around its circumference.

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