A method of curing a surface treatment of a hardware

Abstract

The application discloses a kind of hardware surface treatment solidification method, belong to metal surface coating solidification technical field.The method is heated and solidified to hardware after powder spraying by tunnel type continuous solidification furnace, and core process parameters are as follows: furnace chain running speed 1.6m / min, constant temperature solidification section temperature 130 DEG C, workpiece constant temperature solidification time 30min, corresponding constant temperature heating section effective length is 48m;Solidification furnace is sequentially set preheating section, constant temperature solidification section, cooling section along the direction of conveyance, and the temperature uniformity of constant temperature section is controlled ≤±3 DEG C by the hot air circulation of lower inlet and upper outlet, and workpiece surface coating thickness is controlled at 60~90 μm.The application realizes the continuous uniform solidification of hardware coating by accurate matching of furnace speed, solidification temperature and furnace body length, and the crosslinking degree of coating after solidification is ≥95%, grid adhesion reaches 0 grade, pencil hardness is ≥2H, production efficiency is stable, unit energy consumption is low, and it is suitable for the scale powder spraying solidification production of various hardware stamping parts, die castings and copper bars.

Description

Technical Field

[0001] This invention relates to the field of hardware surface treatment technology, and more specifically to a curing method for surface treatment of hardware parts. Background Technology

[0002] In the powder coating process for hardware parts, coating curing is the core step that determines the final protective and decorative performance. Thermosetting powder coatings require sufficient time at a specific temperature to allow the resin and curing agent to undergo a full cross-linking reaction, forming a dense and continuous high-performance coating. Insufficient curing temperature or time will lead to incomplete cross-linking, resulting in poor coating adhesion, low hardness, and substandard corrosion resistance. Conversely, excessively high curing temperature or time will cause over-curing, leading to defects such as loss of gloss, embrittlement, and cracking, while also wasting energy.

[0003] The existing powder coating and curing production of hardware parts mainly suffers from the following problems: First, intermittent box furnaces are mostly used, which are time-consuming to load and unload, have low production efficiency, large temperature differences between the top and bottom of the furnace, and uneven curing quality of workpieces in the same batch; Second, some continuous curing furnaces have unreasonable parameter matching, with the furnace chain speed being out of sync with the furnace length and temperature, making it impossible to stably guarantee a constant temperature curing time of 30 minutes, resulting in poor product performance consistency; Third, the hot air circulation design is lacking, resulting in poor furnace temperature uniformity, large differences in the curing degree of edges, corners, cavities and planes of complex workpieces, frequent occurrences of local under-curing or over-curing, and low finished product qualification rate.

[0004] Therefore, developing a hardware curing process with precise parameter matching, uniform and stable furnace temperature, and continuous large-scale operation is a key requirement for improving the quality of coated products, increasing production efficiency, and reducing production costs. Summary of the Invention

[0005] In view of this, the purpose of this application is to provide a curing method for surface treatment of hardware parts, so as to solve the problems of unstable furnace temperature and difficulty in continuous large-scale operation in the prior art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A curing method for surface treatment of hardware parts, which uses a tunnel-type continuous curing oven to heat and cure the powder-coated hardware parts, and the specific implementation steps are as follows: Preset parameters: The furnace chain speed is set to 1.6 m / min, the working temperature of the constant temperature curing section is 130℃, and the effective holding time of the workpiece in the constant temperature curing section is 30 min. Based on the calculation of "effective furnace length = furnace speed × curing time", the effective heating length of the constant temperature curing section is set to 48 m, strictly ensuring that the workpiece is in a constant temperature environment of 130℃ throughout the process to ensure sufficient cross-linking reaction.

[0007] Feeding: The electrostatically powder-coated hardware parts are evenly suspended on the special racks for the furnace chain, ensuring that the workpiece spacing is ≥150mm, the layer spacing is ≥200mm, and the distance between the workpiece and the furnace wall is ≥100mm. This guarantees that hot air can fully flow over all surfaces of the workpieces and avoids curing dead zones. The racks enter the curing furnace at a uniform speed with the furnace chain.

[0008] Gradient heating: The workpiece first enters the preheating section and is gradually heated from room temperature to 130℃ at a rate of 8~10℃ / min to avoid poor coating leveling, pinholes or shrinkage cavities and other appearance defects caused by excessively rapid heating.

[0009] Constant temperature curing: The workpiece enters the constant temperature curing section with the furnace chain and is kept at 130℃ for 30 minutes for curing. The furnace adopts a bottom-in, top-out hot air circulation system with the air velocity controlled at 0.8~1.2m / s to ensure that the temperature uniformity of the constant temperature section is ≤±3℃ and the actual temperature deviation of the workpiece surface is ≤±2℃, ensuring that the cross-linking reaction of the coating on workpieces of different positions and shapes is uniform and sufficient.

[0010] Gradient cooling: After curing, the workpiece enters the cooling section, where it is first cooled slowly by natural cooling and then cooled by forced air cooling. The cooling air velocity is controlled at 1.0~1.5m / s to reduce the workpiece temperature to below 60℃, thus preventing the coating from cracking due to internal stress caused by a sudden drop in temperature after leaving the furnace.

[0011] Unloading: After cooling, the workpiece is sent out of the curing oven by the furnace chain and can then be transferred to the next process to complete the entire curing process.

[0012] Furthermore, the curing oven is divided into a preheating section, a constant temperature curing section, and a cooling section along the direction of the oven chain; wherein the length of the preheating section is 12~16m, the length of the constant temperature curing section is 48m, the length of the cooling section is 12~20m, and the total length of the curing oven is 72~84m.

[0013] Furthermore, the powder coating used is a thermosetting epoxy polyester blended powder coating, and the coating thickness on the workpiece surface is controlled at 60~90μm after spraying; after curing by this process, the crosslinking curing degree of the powder coating is ≥95%.

[0014] Furthermore, the cured hardware coating exhibits stable performance that meets the following requirements: cross-cut adhesion grade 0, pencil hardness ≥2H, impact strength ≥50kg·cm, 60° angle gloss ≥85%, and no blistering or rusting during neutral salt spray testing for ≥480h.

[0015] Furthermore, the curing oven hot air circulation system adopts closed-loop temperature control, and the circulating air volume is adjusted in real time according to the oven temperature; the small amount of organic waste gas generated during the curing process is collected and treated by an activated carbon adsorption device to meet the standards before being discharged, thus satisfying environmental protection requirements.

[0016] Compared with the prior art, the present invention has the following beneficial effects: 1. Precise parameter matching ensures stable curing quality. Through quantitative design of a furnace speed of 1.6m / min and a constant temperature range of 48m, the workpiece is strictly guaranteed to cure at 130℃ for exactly 30 minutes. The coating cross-links fully and with high consistency, completely avoiding problems of insufficient or over-curing, and improving the product performance qualification rate to over 99%.

[0017] 2. Excellent oven temperature uniformity and uniform workpiece curing. The bottom-in, top-out hot air circulation structure, combined with reasonable air speed control, ensures that the temperature uniformity in the constant temperature section is ≤±3℃, the surface temperature difference of the workpiece is ≤±2℃, and the corners, cavities and planes of complex-shaped workpieces are cured to a consistent degree with no local defects.

[0018] 3. Continuous production, high efficiency and low consumption. The tunnel-type continuous operation can process 96-meter-long hanging workpieces per hour, which is more than 3 times more efficient than the intermittent box furnace; the gradient temperature zone design and hot air circulation utilization reduce the energy consumption per unit product by about 20% compared with the traditional continuous furnace.

[0019] 4. Strong process adaptability and simple operation and maintenance. The core parameters are clearly defined, and the temperature and speed can be finely adjusted according to the workpiece material and powder type, making it suitable for powder coating and curing of various hardware stamping parts, die casting parts, copper busbars and other workpieces; the furnace body structure is mature and reliable, and daily operation and maintenance are convenient, making it suitable for large-scale industrial production.

[0020] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the preferred embodiments of this application are described in detail below with reference to the accompanying drawings.

[0021] The above and other objects, advantages and features of this application will become more apparent to those skilled in the art from the following detailed description of specific embodiments in conjunction with the accompanying drawings. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. In all drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, the elements or parts are not necessarily drawn to scale.

[0023] Figure 1 This is a schematic diagram of the structure of the present invention; Figure 2 This is a comparison table of test results for embodiments of the present invention. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. In the following description, specific details such as specific configurations and components are provided merely to help fully understand the embodiments of this application. Therefore, those skilled in the art should understand that various changes and modifications can be made to the embodiments described herein without departing from the scope and spirit of this application. In addition, for clarity and brevity, descriptions of known functions and structures are omitted in the embodiments.

[0025] Furthermore, reference numerals and / or letters may be repeated in different examples within this application. Such repetition is for the purpose of simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or settings discussed.

[0026] In this article, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can mean: A exists alone, B exists alone, and A and B exist simultaneously. The term " / and" in this article describes another type of relationship between related objects, indicating that two relationships can exist. For example, A / and B can mean: A exists alone, and A and B exist alone. In addition, the character " / " in this article generally indicates that the related objects before and after it are in an "or" relationship.

[0027] It should also be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion.

[0028] Please see Figure 1-2 This invention provides a technical solution for a curing method for surface treatment of hardware parts: Example 1: Curing of cold-rolled steel sheet stampings This embodiment deals with cold-rolled steel sheet stamped hardware parts, using epoxy-polyester hybrid powder coating with a coating thickness of 70~80μm. The curing process is as follows: A tunnel-type curing oven with a total length of 76m is adopted, including a 14m preheating section, a 48m constant temperature curing section, and a 14m cooling section; the furnace chain running speed is set at 1.6m / min, and the constant temperature curing section is set at 130℃.

[0029] The powder-coated stamped parts are suspended on the hanger with a workpiece spacing of 180mm and a layer spacing of 220mm, and then enter the curing oven at a uniform speed with the furnace chain.

[0030] The workpiece is gradually heated in the preheating section at a rate of about 9°C / min, and the surface temperature of the workpiece reaches 130°C when it enters the constant temperature section.

[0031] The workpiece passes through the constant temperature curing section at a uniform speed, with an effective heat preservation time of exactly 30 minutes; the hot air circulation speed inside the furnace is 1.0 m / s, the temperature uniformity of the constant temperature section is ±2℃, and the surface temperature deviation of the workpiece is ≤±1.5℃.

[0032] The workpiece enters the cooling section, where it is first cooled naturally and then forced to cool by air. The cooling air velocity is 1.2 m / s, and the workpiece exits the furnace at a temperature of 52℃.

[0033] The workpiece is conveyed out with the furnace chain and cured.

[0034] Performance test results: Coating crosslinking degree 96.2%, cross-cut adhesion grade 0, pencil hardness 2H, impact strength 55kg·cm, 60° gloss 88%, no blistering or rust in neutral salt spray test for 500h, fully meeting the coating quality requirements for hardware parts.

[0035] Example 2: Curing of Aluminum Alloy Die-cast Parts This embodiment treats aluminum alloy die-cast parts, using pure polyester powder coating with a coating thickness of 60~70μm. The curing process parameters are the same as in Example 1: constant temperature curing temperature of 130℃, holding time of 30min, and furnace speed of 1.6m / min.

[0036] Performance test results: Coating crosslinking degree 95.8%, adhesion grade 0, pencil hardness 2H, impact strength 50kg・cm, 60° gloss 86%, neutral salt spray test 480h passed, curing quality is stable.

[0037] Comparative Example 1: Insufficient curing time Using the same powder coating and thickness, a traditional continuous curing oven was used with a furnace speed of 2.0 m / min, a constant temperature section length of 36 m, a curing temperature of 130℃, and an actual constant temperature time of approximately 18 min. Test results showed: the coating crosslinking degree was only 82%, adhesion was grade 1, pencil hardness was HB, impact strength was 30 kg·cm, and rust appeared after 120 hours of salt spray testing. Insufficient curing resulted in substandard performance.

[0038] Comparative Example 2: Curing time was too long. The furnace speed was 1.0 m / min, the constant temperature section length was 48 m, and the curing time at 130℃ was 48 min. Test results: The coating showed signs of over-curing, significant loss of gloss (60° gloss was only 65%), embrittlement, and cracks appeared in the impact resistance test, failing to meet the requirements for appearance and mechanical properties.

[0039] As can be seen from the above embodiments and comparative examples, the present invention, through precise matching of furnace speed, temperature and furnace length, and strict control of curing temperature of 130℃ and curing time of 30min, can achieve high-quality curing of powder coating on hardware parts, with stable and excellent performance, and is suitable for industrial continuous production.

[0040] The above description is merely a preferred embodiment of the present invention and does not limit the scope of protection of the present invention. For those skilled in the art, the present invention can have various modifications and variations. Any changes, modifications, substitutions, integrations, and parameter alterations to these embodiments within the spirit and principles of the present invention, achieved through conventional substitutions or by achieving the same function without departing from the principles and spirit of the present invention, fall within the scope of protection of the present invention.

Claims

1. A curing method for surface treatment of hardware parts, characterized in that, The powder-coated metal parts are continuously heated and cured using a tunnel-type continuous curing oven, which includes the following steps: S1) Parameter preset: The furnace chain running speed of the curing oven is set to 1.6m / min, the working temperature of the constant temperature curing section inside the oven is 130℃, and the effective heat preservation time of the workpiece in the constant temperature curing section is 30min; the effective heating length of the constant temperature curing section is 48m, which is precisely matched with the furnace speed and curing time. S2) Feeding the upper part: The powder-coated hardware parts are evenly suspended on the furnace chain hanger and fed into the curing furnace at a uniform speed with the furnace chain; S3) Gradient heating: The workpiece first enters the preheating section and is gradually heated from room temperature to 130℃ at a rate of 8~10℃ / min; S4) Constant temperature curing: The workpiece enters the constant temperature curing section with the furnace chain and is kept at 130℃ for 30 minutes for curing; the hot air circulation speed in the furnace is controlled at 0.8~1.2m / s, and the temperature uniformity of the constant temperature section is ≤±3℃. S5) Gradient cooling: The cured workpiece enters the cooling section and is gradually cooled to below 60°C; S6) Unloading: The cooled workpiece is sent out of the curing oven by the furnace chain to complete the curing process.

2. The curing method for surface treatment of hardware parts according to claim 1, characterized in that, The curing oven is divided into a preheating section, a constant temperature curing section, and a cooling section along the direction of the oven chain; the preheating section is 12-16m long, the constant temperature curing section is 48m long, the cooling section is 12-20m long, and the total length of the curing oven is 72-84m.

3. The curing method for surface treatment of hardware parts according to claim 1, characterized in that, In step (2), the hanging distance of hardware parts on the hanger is ≥150mm, the layer spacing between upper and lower workpieces is ≥200mm, and the distance between the workpiece and the inner wall of the furnace is ≥100mm.

4. The curing method for surface treatment of hardware parts according to claim 1, characterized in that, The powder coating used is a thermosetting epoxy polyester blended powder coating. After spraying, the coating thickness on the workpiece surface is controlled at 60~90μm. After curing, the cross-linking curing degree of the powder coating is ≥95%.

5. The curing method for surface treatment of hardware parts according to claim 1, characterized in that, During the constant temperature curing process in step (4), the actual temperature deviation of the workpiece surface is ≤ ±2℃, and the cross-linking reaction of the coating is uniform and sufficient.

6. The curing method for surface treatment of hardware parts according to claim 1, characterized in that, The cooling section in step (5) adopts a combination of natural cooling and forced air cooling. The forced air cooling wind speed is 1.0~1.5m / s, and the workpiece exit temperature is ≤60℃.

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