Threaded fastener

Abstract

The present application provides a threaded fastener comprising: a head; the screw rod is provided with an external thread section; the composite coating comprises a hot-dip galvanizing coating serving as a bottom layer and a non-electrolytic zinc sheet coating serving as a top layer and covering the hot-dip galvanizing coating, and the composite coating is fixed to the surface of the head and the surface of the screw through the hot-dip galvanizing coating. The threaded fastener has good corrosion resistance and good anti-collision performance, and the assembly process is simplified.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of fasteners, in particular to a threaded fastener. BACKGROUND

[0002] In order to ensure the reliability and durability of the connection, the threaded fastener usually needs to be surface treated, such as surface coating treatment. Although the surface coating can improve the corrosion resistance or wear resistance of the threaded fastener to a certain extent, there are still certain limitations in application, which may not be able to meet the multiple performance requirements of the threaded fastener.

[0003] It should be explained that the content introduced here is only to provide background information related to the present disclosure, and does not necessarily belong to the prior art. CONTENT OF THE UTILITY MODEL

[0004] The purpose of the present application is to provide an improved threaded fastener which has advantages in chemical properties and assembly process.

[0005] In addition, the present application also aims to solve or alleviate other technical problems existing in the prior art.

[0006] The threaded fastener according to the present application comprises:

[0007] a head;

[0008] a screw rod having an externally threaded section;

[0009] a composite coating comprising a hot-dip galvanized layer as a bottom layer and a non-electrolytic zinc flake coating as a top layer and covering the hot-dip galvanized layer, wherein the composite coating is fixed on the surface of the head and the screw rod with the hot-dip galvanized layer.

[0010] In the threaded fastener according to the present application, optionally, the composite coating is applied on the entire surface of the head and the screw rod.

[0011] In the threaded fastener according to the present application, optionally, the screw rod further has a rod section between the head and the externally threaded section and no thread is provided on the rod section.

[0012] In the threaded fastener according to the present application, optionally, a flange section is further integrally formed on the bottom surface of the head facing the screw rod, and the composite coating is provided on the surface of the flange section.

[0013] In the threaded fastener according to the present application, optionally, the threaded fastener further comprises a gasket for tightly abutting on the bottom surface of the head facing the screw rod, wherein the composite coating is provided on the surface of the gasket.

[0014] In the threaded fastener according to the present application, optionally, the threaded fastener further comprises a nut having an inner threaded section for mating with the outer threaded section, wherein the non-electrolytic zinc flake coating is provided on the surface of the inner threaded section and the composite coating is provided on the remaining area of the nut.

[0015] In the threaded fastener according to the present application, optionally, in the composite coating, the non-electrolytic zinc flake coating is applied on the sandblasted surface of the hot-dip zinc plating layer.

[0016] In the threaded fastener according to the present application, optionally, the thickness of the hot-dip zinc plating layer is 50-100 μm.

[0017] In the threaded fastener according to the present application, optionally, the thickness of the non-electrolytic zinc flake coating is 5-20 μm.

[0018] In the threaded fastener according to the present application, optionally, the threaded fastener is a hexagonal head bolt.

[0019] The threaded fastener according to the present application has at least the following advantages: on the one hand, it has good corrosion resistance and anti-impact performance, and on the other hand, it has a simplified assembly process and improved salt spray test performance. BRIEF DESCRIPTION OF DRAWINGS

[0020] The above and other features of the present application will become more apparent by describing in detail the embodiments thereof with reference to the attached drawings in which,

[0021] Figure 1 FIG. 1 shows one embodiment of the threaded fastener according to the present application;

[0022] Figure 2 FIG. 2 shows another embodiment of the threaded fastener according to the present application. DETAILED DESCRIPTION

[0023] The present application will be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments of the application are shown. The present application may, however, be embodied in different forms, and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the application to those skilled in the art.

[0024] In this specification, terms such as "comprise" and "include" indicate that the technical solution of the present application does not exclude the presence of other elements and steps not directly or explicitly stated in the specification and claims.

[0025] Unless otherwise specified, terms such as “first” and “second” do not indicate the order of units in terms of time, space, size, etc., but are merely used to distinguish between units.

[0026] It is recognized that threaded fasteners with a single coating have certain application limitations and may not be able to simultaneously meet the multiple performance requirements of threaded fasteners, such as the performance requirements of the fastener itself and the requirements of its fit with the connected parts. For threaded fasteners with hot-dip galvanized coatings, the thicker zinc layer provides better corrosion and impact resistance. However, because the hot-dip galvanized coating is relatively porous, the test results under salt spray are poor, and its surface is relatively rough, which is not conducive to assembly with the connected parts, requiring the application of lubricant during installation. Therefore, there is an urgent need to improve threaded fasteners to simultaneously meet their multiple performance requirements as much as possible.

[0027] Figure 1 A first embodiment of a threaded fastener according to this application is shown. The threaded fastener 100 generally includes a head 110 and a screw 120. The threaded fastener is screwed into or out of a connected component by screwing the head 110 with the aid of a tool. The screw 120 has an externally threaded section 121 and a shank section 122, wherein the externally threaded section mates with an internally threaded section of the connected component, and the shank section is located between the head 110 and the externally threaded section 121 and is not threaded thereon.

[0028] Specifically, in Figure 1 In this embodiment, the threaded fastener is a partially threaded (e.g., half-threaded) hexagonal head bolt, with a hexagonal head 110 and an external threaded section 121 extending axially through a portion of the length of the screw 120. Alternatively, the external threaded section 121 can extend axially through the entire length of the screw; in other words, the screw 120 has external threads on all surfaces, i.e., a fully threaded hexagonal head bolt. An analogy can be found by referring to... Figure 2 .

[0029] Furthermore, the threaded fastener 100 is formed with a composite coating by surface treatment, which is applied to the outer surface of the head 110 and the shank 120, in particular to the entire outer surface thereof. Here, it is not excluded that the composite coating is applied only on partial areas of the threaded fastener, for example only on the shank, or only on partial areas of the shank and the head, for example on partial areas close to the shank. The composite coating comprises a hot-dip zinc plating layer and a non-electrolytic zinc flake coating layer, wherein the hot-dip zinc plating layer is applied as a base layer on the metal substrate of the threaded fastener, and the non-electrolytic zinc flake coating layer is applied as a top layer on the hot-dip zinc plating layer, i.e. the non-electrolytic zinc flake coating layer is further away from the metal substrate of the threaded fastener than the hot-dip zinc plating layer. Here, the metal substrate can refer to, but is not limited to, a carbon steel substrate or an alloy steel substrate.

[0030] The composite coating combines the respective advantages of the hot-dip zinc plating layer and the non-electrolytic zinc flake coating layer. On the one hand, the hot-dip zinc plating layer as a base layer achieves good corrosion resistance and anti-chipping performance, and on the other hand, the non-electrolytic zinc flake coating layer as a top layer improves the assembly process with the connected part and the salt spray test performance (for example, it can reach more than 1000 hours), wherein the non-electrolytic zinc flake coating layer has good appearance and does not need to be specially coated with lubricant during the assembly process.

[0031] The preparation method of the composite coating is described taking the threaded fastener according to the first embodiment as an example. In the hot-dip zinc stage, the threaded fastener after surface pretreatment (for example, rust removal, degreasing) is immersed in the heated and melted liquid zinc, the excess liquid zinc adhered to the surface is spun off by centrifugation, dried, and cooled to form a hot-dip zinc plating layer on the surface of the threaded fastener. In the non-electrolytic zinc flake coating stage, the threaded fastener after hot-dip zinc is surface pretreated (for example, oil removal, rust removal), immersed in a suspension of zinc-aluminum powder, spun, dried, and cooled to form a non-electrolytic zinc flake coating layer on the hot-dip zinc plating layer.

[0032] In another optional embodiment, the threaded fastener is subjected to sandblasting treatment after hot-dip zinc and before non-electrolytic zinc flake coating, i.e. the non-electrolytic zinc flake coating layer of the composite coating is applied on the sandblasted surface of the hot-dip zinc plating layer. Here, through the sandblasting treatment, the adhesion can be increased and the rust removal process in the non-electrolytic zinc flake coating stage can be omitted.

[0033] Exemplarily, it is feasible that the thickness of the hot-dip zinc plating layer of the composite coating is 50-100 μm. It is also feasible that the thickness of the non-electrolytic zinc flake coating layer of the composite coating is 5-20 μm.

[0034] In total, the total thickness of the composite coating can be at least 50 μm while meeting the thread fit requirements. Here, the size of the portion of the connected member for thread fit with the threaded fastener (e.g., the portion for the external thread section 121) or the portion for form fit (e.g., the portion for the shank section 122) can be increased accordingly to compensate for the dimensional deviation caused by the composite coating in order to meet the thread fit requirements.

[0035] Figure 2 A second embodiment of the threaded fastener according to the present application is shown, which is configured as a hexagonal head bolt, the external thread section 121 extending through the entire length of the shank 120 in the axial direction, i.e., a full thread hexagonal head bolt. A flange 123 is also integrally formed on the bottom surface of the head 110 of the threaded fastener 100 facing the shank 120, which can increase the contact area with the connected member, disperse the pressure, and reduce the damage to the surface of the connected member. The composite coating as described above is provided on the surface of the flange 123. Exemplarily, such a composite coating is provided on the entire area of the flange 123 directly contacting the external environment.

[0036] Instead of the full thread design shown in Figure 2 , the external thread section 121 can also only occupy a partial length of the shank 120 in the axial direction, e.g., a half thread hexagonal head flange bolt.

[0037] In an embodiment not shown, the threaded fastener 100 further comprises a washer clamped between the bottom surface of the head 110 facing the shank 120 and the connected member in the assembled state, wherein the composite coating as described above is provided on the surface of the washer. Exemplarily, such a composite coating is provided on the entire surface of the washer.

[0038] In another embodiment not shown, the threaded fastener 100 further comprises a nut having an internal thread section for mating with the external thread section 121. Here, only the internal thread section of the nut is provided with the non-electrolytic zinc flake coating, while the remaining area is provided with the composite coating as described above. Such a nut can be manufactured by first subjecting the threaded fastener to hot-dip galvanizing, subsequently forming the internal thread section, and finally subjecting the threaded fastener to non-electrolytic zinc flake coating.

[0039] In general, the threaded fastener according to the present application has good corrosion resistance and impact resistance by providing a composite coating, and the assembly process with the connected member is also simplified. In one embodiment according to the present application, the bonding force is improved and the production process is simplified by applying a non-electrolytic zinc sheet coating on the surface of a sandblasted hot-dip zinc plated layer. In another embodiment of the present application, the contact area of the threaded fastener with the connected member is increased and the damage to the surface thereof is reduced by the gasket or flange portion having a composite coating. In another embodiment of the present application, the threaded fastener is modified by the nut to ensure the threaded fit requirement in addition to the corrosion resistance and impact resistance.

[0040] The embodiments and examples set forth herein are presented to best explain the present application and its particular application. Those skilled in the art will however know that many apparent variations of the foregoing description are possible without departing from the scope of the present application.

Claims

1. A threaded fastener, characterized in that, It includes: head; The screw has an external thread section; A composite coating comprising a hot-dip galvanized layer as the bottom layer and an electroless zinc flake coating as the top layer covering the hot-dip galvanized layer, wherein the composite coating is fixed to the surfaces of the head and the screw by means of the hot-dip galvanized layer.

2. The threaded fastener according to claim 1, characterized in that, The composite coating is applied to the entire surface of the head and the screw.

3. The threaded fastener according to claim 2, characterized in that, The screw also has a shank section located between the head and the external thread section, and the shank section is not threaded.

4. The threaded fastener according to claim 2, characterized in that, A flange is integrally formed on the bottom surface of the head facing the screw, and the composite coating is provided on the surface of the flange.

5. The threaded fastener according to claim 1, characterized in that, The threaded fastener further includes a washer for fitting tightly against the bottom surface of the head facing the screw, wherein the composite coating is provided on the surface of the washer.

6. The threaded fastener according to claim 1, characterized in that, The threaded fastener further includes a nut having an internal thread section for mating with the external thread section, wherein a non-electrolytic zinc flake coating is provided on the surface of the internal thread section and the composite coating is provided on the remaining area of ​​the nut.

7. The threaded fastener according to claim 1, characterized in that, In the composite coating, the non-electrolytic zinc sheet coating is applied to the sandblasted surface of the hot-dip galvanized layer.

8. The threaded fastener according to claim 1, characterized in that, The thickness of the hot-dip zinc coating is 50-100 μm.

9. The threaded fastener according to claim 1, characterized in that, The thickness of the non-electrolytic zinc sheet coating is 5-20 μm.

10. The threaded fastener according to claim 1, characterized in that, The threaded fastener is a hexagonal head bolt.

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