Surface treatment method for rivet assembly

Abstract

The application provides a surface treatment method of a pull rivet assembly, which comprises the following steps: forming a zinc-aluminum coating on a pull rivet and a sleeve ring through a multiple film forming mode; wherein the material of the pull rivet is medium-carbon alloy structural steel, the material of the sleeve ring is low-carbon steel, the zinc content in the zinc-aluminum coating is 85%-95%, and the aluminum content in the zinc-aluminum coating is 5%-15%; and the zinc-aluminum coating is subjected to heat diffusion treatment to form an iron-zinc-aluminum alloy protective layer on the surface of the pull rivet and the sleeve ring. In the technical scheme, the zinc-aluminum coating is formed on the pull rivet and the sleeve ring through the multiple film forming mode, and the heat diffusion treatment mode is adopted, so that the zinc diffuses into the pull rivet and the sleeve ring, and the iron of the pull rivet and the sleeve ring diffuses into the zinc-aluminum coating, thereby forming the iron-zinc-aluminum alloy protective layer, improving the structural strength of the protective layer on the outer side of the pull rivet and the sleeve ring, improving the corrosion resistance, and improving the use effect of the pull rivet and the sleeve ring.

Description

Technical Field

[0001] This application relates to the field of fastener technology, and more particularly to a surface treatment method for a rivet assembly. Background Technology

[0002] Rivets are widely used in the riveting structures of aircraft and railway transportation equipment to replace the original hot rivets. They have the advantages of large clamping force and are not easy to loosen.

[0003] A rivet consists of a rivet body and a collar. During use, pulling the rivet body deforms the collar, thus securing the two mating parts together. The rivet body is made of medium-carbon alloy structural steel through cold heading, thread rolling, and heat treatment and tempering. The collar is made of low-carbon steel through cold heading and annealing. Depending on the application, existing technologies employ different surface treatment processes for the rivet body and collar assembly, such as blackening, electroplating, and Dacromet coating. The purpose of these surface treatments is to form a physical coating on the rivet surface. However, this coating is not resistant to impact, compression, or abrasion. During the installation and use of rivets, a special rivet gun is required for tightening and compression, inevitably causing damage to the rivet and collar surfaces. This damage disrupts the integrity of the rivet's surface coating, reducing the rust and corrosion resistance of the rivet and the riveted workpiece, and failing to meet the requirement of no red rust after 168 hours of neutral salt spray testing. Especially when applied to aluminum alloy vehicle bodies, there is a large potential difference corrosion between the rivets, collars and the aluminum alloy vehicle body, making it even more difficult to meet the technical requirement of no red rust on the surface of the rivets after the aluminum alloy parts are riveted and after a neutral salt spray test of 168 hours. Summary of the Invention

[0004] This application provides a surface treatment method for rivet assemblies, which improves the corrosion resistance of rivets and collars.

[0005] This application provides a surface treatment method for a rivet assembly, the method comprising the following steps: A zinc-aluminum coating is formed on rivets and collars through multiple film-forming processes; wherein the rivets are made of medium-carbon alloy structural steel, the collars are made of low-carbon steel, the zinc content in the zinc-aluminum coating is 85%~95%, and the aluminum content in the zinc-aluminum coating is 5%~15%; A heat diffusion treatment is applied to the zinc-aluminum coating to form an iron-zinc-aluminum alloy protective layer on the surface of the rivets and collars.

[0006] In the above technical solution, a zinc-aluminum coating is formed on the rivet and collar through multiple film-forming processes. Then, a thermal diffusion surface treatment is used to diffuse zinc and aluminum into the rivet core and collar body. During this process, iron elements from the rivet and collar body can also diffuse into the zinc-aluminum coating, forming an iron-zinc-aluminum alloy protective layer. This improves the structural strength of the protective layer on the outside of the rivet and collar. Moreover, the iron-zinc-aluminum alloy protective layer is mutually penetrating and bonded with the body, adapting to the inevitable deformation of the rivet during installation and use, maintaining the integrity of the iron-zinc-aluminum alloy protective layer, avoiding damage to the surface of the rivet and collar caused by tightening and squeezing operations during installation, resisting impact, squeezing, and wear, adapting to the deformation of the rivet, and its surface coating remains continuous and intact with the deformation of the body, always maintaining the rust-proof and corrosion-proof performance of the rivet and the riveted workpiece, thus improving the performance of the rivet and collar.

[0007] In a specific feasible embodiment, a zinc-aluminum coating is formed on rivets and collars through a multiple film-forming process; specifically including: A paste-like coating solution is formed by mixing zinc powder, aluminum powder and ethylene glycol; Immerse the rivets and collars in the paste-like coating liquid and remove them; the paste-like coating liquid adheres to the rivets and collars. The rivets and collars are baked, and the paste coating liquid adhering to the rivets and collars is sintered into a film; Cool the rivets and collars, and after cooling, repeatedly immerse the rivets and collars in the paste-like coating liquid and sinter them into a film multiple times.

[0008] In a specific feasible embodiment, the thickness of the zinc-aluminum coating formed by each sintering is between 3μm and 5μm; The thickness of the zinc-aluminum coating formed after multiple film formations is between 8μm and 10μm.

[0009] In one specific implementable embodiment, the baking of the rivets and collars, and the sintering of the paste-like coating liquid adhering to the rivets and collars into a film, specifically includes: Within 30 minutes, place the rivets and collars into the baking oven for pre-baking at a temperature of 120±10℃ for 10-15 minutes. The pre-baked rivets and collars are sintered and cured at a high temperature of 280℃~350℃ for 20 minutes to 40 minutes.

[0010] In a specific feasible implementation, it also includes: degreasing, washing, drying and shot peening the rivets and collars before multiple film formation processes.

[0011] In one specific implementable embodiment, the thermal diffusion treatment of the zinc-aluminum coating to form an iron-zinc-aluminum alloy protective layer on the surface of the rivet and collar specifically includes: The rivets, collars, and heat diffusion treatment additives are placed in a rotary furnace for heat diffusion treatment. The heat diffusion temperature is 480℃~500℃, and the rotation speed of the rotary furnace is between 8~10 r / min. After the heat diffusion is complete, the rotation speed of the rotary furnace is maintained until the temperature of the rivets and collars cools down to below 100°C.

[0012] In one specific implementable embodiment, the aid for the thermal diffusion treatment comprises the following components: It contains 15% zinc chloride, 10%~15% zinc powder, and 70%~75% silicon dioxide.

[0013] In one specific implementable embodiment, the zinc chloride has a mesh size of 150-300 mesh; the zinc powder has a mesh size of 250-300 mesh; and the silicon dioxide has a mesh size of 80-120 mesh.

[0014] In a specific feasible implementation, the duration of the thermal diffusion treatment is between 1.5 and 2 hours.

[0015] In one specific implementable embodiment, the heat diffusion treatment of the zinc-aluminum coating to form an iron-zinc-aluminum alloy protective layer on the surface of the rivet and collar further includes: The thickness of the zinc-aluminum coating was measured before the thermal diffusion treatment. Attached Figure Description

[0016] Figure 1 A flowchart illustrating the surface treatment method for a rivet assembly provided in this application embodiment. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of this application clearer, the application will now be described in further detail with reference to the accompanying drawings.

[0018] It should be noted that, unless otherwise defined, the technical or scientific terms used in one or more embodiments of this specification should have the ordinary meaning understood by one of ordinary skill in the art to which this disclosure pertains. The terms "first," "second," and similar words used in one or more embodiments of this specification 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 following 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 used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0019] To facilitate understanding of the surface treatment method for rivet assemblies provided in this application embodiment, its application scenario is first described. The surface treatment method for rivet assemblies provided in this application embodiment is applied during the processing of rivets and collars. In the processing of rivets and collars, existing technologies often apply conventional anti-corrosion coatings to the surfaces of rivets and collars. However, during use, the tightening and compression of rivets and collars damage their surfaces, disrupting the continuity of the surface coating and thus affecting the rust and corrosion resistance of the rivets, collars, and riveted workpieces. Therefore, this application embodiment provides a surface treatment method for rivet assemblies to improve the corrosion resistance of rivet assemblies (rivets and collars). The following detailed description, in conjunction with specific drawings and embodiments, further clarifies this method.

[0020] refer to Figure 1 , Figure 1 This invention provides a surface treatment method for a rivet assembly according to an embodiment of the present application. The method includes the following steps: Step 001: Form a zinc-aluminum coating on the rivets and collars through multiple film-forming processes; Specifically, when forming a zinc-aluminum coating on a rivet assembly (rivet and collar) using a multiple film-forming method, the rivet is made of medium-carbon alloy structural steel, the collar is made of low-carbon steel, the zinc content in the zinc-aluminum coating is 85%~95%, and the aluminum content in the zinc-aluminum coating is 5%~15%. In this step, the following steps can be taken: Step 01: Mix zinc powder, aluminum powder and ethylene glycol to form a paste-like coating solution; Specifically, zinc powder, aluminum powder, and ethylene glycol are first mixed to form a paste-like coating solution. This coating solution is then applied to rivets and collars to form a film. The main components of the film are zinc powder and aluminum powder, while ethylene glycol acts as a carrier liquid to mix the zinc and aluminum powders, forming the paste structure. In the film, the zinc content is 85%–95%, and the aluminum content is 5%–15%. For example, the zinc and aluminum composition in the film can be as follows: zinc content can be 85%, 87%, 90%, 92%, 95%, etc., and correspondingly, aluminum content can be 15%, 13%, 10%, 8%, 5%, etc.

[0021] It should be understood that the density, pH value, viscosity, temperature, and flow conditions of the coating solution directly affect the coating effect of the rivet assembly and thus the various properties of the coating. Therefore, the relationship between temperature, coating solution parameters, and centrifuge speed during dip coating must be properly adjusted during the coating process. The above data can be determined through multiple experiments based on actual production, and will not be elaborated further in this application.

[0022] Step 02: Immerse the rivets and collars in the paste-like coating liquid and remove them. The paste-like coating liquid will adhere to the rivets and collars. Specifically, when coating rivets and collars with the coating solution, the rivets and collars are immersed in the coating solution to ensure that the coating solution can coat the rivets and collars. In addition, before immersing the rivets and collars in the coating solution, they need to be pre-treated to remove impurities. Specifically, the rivets and collars are degreased, washed, dried, and shot-peened.

[0023] In one alternative, the cleaned rivet assembly, after being degreased and derusted, must be surface coated as soon as possible by dip coating to ensure the coating effect.

[0024] Step 03: Bake the rivets and collars, and sinter the paste coating liquid adhering to the rivets and collars into a film; Specifically, it includes the following steps: Step a: Preheat the rivets and collars; Specifically, the rivets and collars are placed in the baking oven for pre-baking within 30 minutes at a temperature of 120±10℃ for 10-15 minutes. When using this pre-baking method, placing the rivets and collars in the oven for a shorter period (30 minutes) allows the moisture in the coating solution to evaporate and level evenly, ensuring a uniform film thickness.

[0025] Step b: Sintering to form a film; Specifically, the pre-baked rivets and collars are sintered and cured at a high temperature of 280℃~350℃ for 20 to 40 minutes. During the sintering process, the pre-dried coating material is sintered to form a zinc-aluminum coating. The thickness of the sintered zinc-aluminum coating is between 3μm and 5μm.

[0026] Step 04: Cool the rivets and collars, and after cooling, repeatedly immerse the rivets and collars in the paste coating liquid and sinter them into a film multiple times.

[0027] Specifically, after the rivets and collars are sintered and cured, they are cooled by an air-cooling system. After sufficient cooling, steps 02-04 are repeated, thereby forming a multi-layer zinc-aluminum coating on the surface of the rivets and collars through multiple coating applications and sintering. The zinc-aluminum coating formed by multiple sinterings forms an integral structure. The thickness of the zinc-aluminum coating formed after multiple film formations is between 8μm and 10μm to ensure sufficient thickness to guarantee structural strength.

[0028] Step 002: Perform heat diffusion treatment on the zinc-aluminum coating to form an iron-zinc-aluminum alloy protective layer on the surface of the rivets and collars.

[0029] Specifically, it includes the following steps: Step 1: Place the rivets, collars, and heat diffusion treatment additives into a rotary furnace for heat diffusion treatment; Specifically, during the heat diffusion process, the iron in the rivets and collars can diffuse into the zinc-aluminum coating, and the zinc in the zinc-aluminum coating can diffuse into the rivets and collars, thereby forming an iron-zinc-aluminum coating on the surface of the rivets and collars.

[0030] In this embodiment, the heat diffusion treatment aid includes the following components: 15% zinc chloride, 10%~15% zinc powder, and 70%~75% silica. For example, the proportions of the above components can be: 15% zinc chloride, 10% zinc powder, and 75% silica; or 15% zinc chloride, 12% zinc powder, and 77% silica; or 15% zinc chloride, 15% zinc powder, and 70% silica. In the above schemes, the composition of the heat diffusion treatment aid differs significantly from other commercially available diffusion agents. Since the surfaces of the rivets and collars are already coated with an 8-10 micrometer zinc-aluminum coating, the zinc content of the aid used in this embodiment only needs to be about one-third of the total aid content, eliminating the need for a large proportion of zinc. In addition, because zinc accounts for a relatively low proportion in this additive, and silicon dioxide is used in a larger proportion, the additive is less prone to clumping or agglomeration during use, has good dispersibility, and has a repeatable service life that is 1-2 times longer.

[0031] Furthermore, the particle sizes of the various components of the heat diffusion treatment aid can be as follows: zinc chloride 150-300 mesh; zinc powder 250-300 mesh; silica 80-120 mesh. For example, zinc chloride can be 150, 180, 200, 230, 270, or 300 mesh; zinc powder 250, 260, 270, 280, 290, or 300 mesh; and silica 80, 90, 100, 110, or 120 mesh. Using these particle sizes makes it easier to mix the components evenly, and also facilitates zinc diffusion during use.

[0032] During the heat diffusion treatment, the rivets and collars are first placed in a sealed, circular rotary furnace. The temperature for heat diffusion is controlled at 480℃~500℃, and the rotation speed of the furnace is between 8~10 r / min. The duration of the heat diffusion treatment is between 1.5~2 hours. Under these conditions, the iron and zinc can be fully diffused, ensuring the structural strength of the resulting iron-zinc-aluminum alloy protective layer.

[0033] Step 2: After the heat diffusion is complete, continue to maintain the rotation speed of the rotary furnace until the temperature of the rivets and collars cools down to below 100°C.

[0034] Step 002 may further include the following step: Before performing the heat diffusion treatment, the thickness of the zinc-aluminum coating is checked. Specifically, a thickness measuring device is used to check whether the thickness of the zinc-aluminum coating on the rivets and collars is between 8 μm and 10 μm. If the thickness of the zinc-aluminum coating meets the requirements, step 002 is performed; if the thickness does not meet the requirements, the rivets are scrapped, or another layer of zinc-aluminum coating is sintered.

[0035] As can be seen from the above description, the surface treatment method for the rivet assembly provided in this application forms a zinc-aluminum coating on the rivet and collar through multiple film formation processes. Then, a thermal diffusion surface treatment method is used to diffuse zinc and aluminum into the rivet core and collar body. During this process, iron elements in the rivet and collar body can also diffuse into the zinc-aluminum coating to form an iron-zinc-aluminum alloy protective layer. This improves the structural strength of the protective layer on the outside of the rivet and collar. Moreover, the iron-zinc-aluminum alloy protective layer is mutually penetrating and bonded with the body, adapting to the inevitable deformation of the rivet during installation and use, maintaining the integrity of the iron-zinc-aluminum alloy protective layer, avoiding damage to the surface of the rivet and collar caused by tightening and squeezing operations during installation, resisting impact, squeezing, and wear, adapting to the deformation of the rivet, and its surface coating remains continuous and intact with the deformation of the body, always maintaining the rust-proof and corrosion-proof performance of the rivet and the riveted workpiece, and improving the performance of the rivet and collar.

[0036] One or more embodiments of this specification 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 one or more embodiments of this specification should be included within the scope of protection of this disclosure.

[0037] The above are merely specific embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A surface treatment method for a rivet assembly, characterized in that, Includes the following steps: A zinc-aluminum coating is formed on rivets and collars through multiple film-forming processes; wherein the rivets are made of medium-carbon alloy structural steel, the collars are made of low-carbon steel, the zinc content in the zinc-aluminum coating is 85%~95%, and the aluminum content in the zinc-aluminum coating is 5%~15%; A heat diffusion treatment is applied to the zinc-aluminum coating to form an iron-zinc-aluminum alloy protective layer on the surface of the rivets and collars.

2. The surface treatment method for the rivet assembly according to claim 1, characterized in that, A zinc-aluminum coating is formed on rivets and collars through multiple film-forming processes; specifically including: A paste-like coating solution is formed by mixing zinc powder, aluminum powder and ethylene glycol; Immerse the rivets and collars in the paste-like coating liquid and remove them; the paste-like coating liquid adheres to the rivets and collars. The rivets and collars are baked, and the paste coating liquid adhering to the rivets and collars is sintered into a film; Cool the rivets and collars, and after cooling, repeatedly immerse the rivets and collars in the paste-like coating liquid and sinter them into a film multiple times.

3. The surface treatment method for the rivet assembly according to claim 2, characterized in that, The thickness of the zinc-aluminum coating formed by each sintering is between 3μm and 5μm; The thickness of the zinc-aluminum coating formed after multiple film formations is between 8μm and 10μm.

4. The surface treatment method for the rivet assembly according to claim 3, characterized in that, The process of baking the rivets and collars, and sintering the paste-like coating liquid adhering to the rivets and collars into a film, specifically includes: Within 30 minutes, place the rivets and collars into the baking oven for pre-baking at a temperature of 120±10℃ for 10-15 minutes. The pre-baked rivets and collars are sintered and cured at a high temperature of 280℃~350℃ for 20 minutes to 40 minutes.

5. The surface treatment method for the rivet assembly according to claim 1, characterized in that, Also includes: Before multiple film formation processes, the rivets and collars are degreased, washed, dried, and shot peened.

6. The surface treatment method for a rivet assembly according to any one of claims 1 to 5, characterized in that, The process of heat diffusion treatment on the zinc-aluminum coating to form an iron-zinc-aluminum alloy protective layer on the surface of the rivets and collars specifically includes: The rivets, collars, and heat diffusion treatment additives are placed in a rotary furnace for heat diffusion treatment. The heat diffusion temperature is 480℃~500℃, and the rotation speed of the rotary furnace is between 8~10 r / min. After the heat diffusion is complete, the rotation speed of the rotary furnace is maintained until the temperature of the rivets and collars cools down to below 100°C.

7. The surface treatment method for the rivet assembly according to claim 6, characterized in that, The heat diffusion treatment aid contains the following components: It contains 15% zinc chloride, 10%~15% zinc powder, and 70%~75% silicon dioxide.

8. The surface treatment method for the rivet assembly according to claim 7, characterized in that, The zinc chloride has a mesh size of 150-300 mesh; the zinc powder has a mesh size of 250-300 mesh; and the silicon dioxide has a mesh size of 80-120 mesh.

9. The surface treatment method for the rivet assembly according to claim 6, characterized in that, During the thermal diffusion treatment, the duration of the thermal diffusion treatment is between 1.5 and 2 hours.

10. The surface treatment method for the rivet assembly according to claim 6, characterized in that, The process of heat-diffusion treatment of the zinc-aluminum coating to form an iron-zinc-aluminum alloy protective layer on the surface of the rivets and collars also includes: The thickness of the zinc-aluminum coating was measured before the thermal diffusion treatment.

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