Stainless steel surface treatment process and application

Abstract

The invention relates to a stainless steel surface treatment process and application, and relates to the technical field of metal surface treatment. The method comprises the following steps in sequence. Ultrasonic degreasing, first-time duplex washing, pickling activation, second-time duplex washing, micro-etching, third-time duplex washing, first-time ultrasonic washing, chemical etching, fourth-time duplex washing, second-time ultrasonic washing, fifth-time duplex washing, surface protection treatment, sixth-time duplex washing, hot water washing and baking solidification performing chemical treatment; wherein a mixed solution containing persulfate and organic acid is adopted for micro-etching, the etching depth is controlled to be 0.5-2 microns, and the two times of ultrasonic washing are symmetrically arranged before and after chemical etching respectively. Furthermore, the pickling activation solution is a composite solution of 10-15% nitric acid and 3-5% hydrofluoric acid, the treatment temperature is 30-40 DEG C, and the treatment time is 30-60 seconds. The surface area is greatly increased, the interface bonding strength of a subsequent protective film or a nano injection molding material is improved, and the problem of insufficient bonding force caused by traditional sand blasting or acid pickling is solved.

Description

Technical Field

[0001] This application relates to the technical field of metal surface treatment, and in particular to a treatment process and application for the surface of stainless steel. Background Art

[0002] Stainless steels (such as 304, 316, etc.) are widely used in fields such as precision electronics, medical devices, automotive parts, and high-end decoration due to their excellent corrosion resistance, high strength, and good processing performance. However, during the processing and storage of untreated stainless steel surfaces, an oxide film is easily formed on the stainless steel surface, and pollutants such as grease and dust are adsorbed, affecting the bonding force of subsequent processing (such as etching, coating, welding, or nano-injection molding). The surface adhesion of stainless steel itself is poor, and when spraying, plating, or plastic inlaying is directly carried out, problems such as coating peeling and insufficient bonding force are likely to occur. Therefore, the surface of stainless steel needs to be treated to meet the requirements of high-end manufacturing.

[0003] The existing Chinese patent with the publication number CN105220161A discloses a surface treatment process for stainless steel. S1. Polish the surface of the stainless steel product; S2. Sandblast the surface of the stainless steel product to make the surface roughness of the stainless steel product Ra0.5 - Ra1.5; S3. Clean the stainless steel product; S4. Send the stainless steel product to a magnetron sputtering device for deposition treatment so that an aluminum layer is deposited and covered on the surface of the stainless steel product; S5. Take out the stainless steel product and perform anodic oxidation treatment; S6. Dye the anodized stainless steel product; S7. The surface treatment is completed.

[0004] In related technologies, traditional sandblasting or mechanical polishing can only provide macroscopic roughness and cannot form a micron / nanometer-level controllable structure, making it difficult to adapt to high-precision etching or nano-injection molding processes.

[0005] Therefore, it is urgent to develop a treatment process for the surface of stainless steel to meet the high standards of high-end manufacturing. Summary of the Invention

[0006] The technical problem to be solved by the present invention is: to provide a treatment process and application for the surface of stainless steel, which solves the technical problem that traditional sandblasting or mechanical polishing can only provide macroscopic roughness and cannot form a micron / nanometer-level controllable structure, making it difficult to adapt to high-precision etching or nano-injection molding processes.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] A treatment process for the surface of stainless steel successively includes the following steps:

[0009] Ultrasonic degreasing → First two-stage water washing → Pickling activation → Second two-stage water washing → Micro-etching → Third two-stage water washing → First ultrasonic water washing → Chemical etching → Fourth two-stage water washing → Second ultrasonic water washing → Fifth two-stage water washing → Surface protection treatment → Sixth two-stage water washing → Hot water washing → Baking and curing; among them, the micro-etching uses a mixed solution containing persulfate and organic acid, the etching depth is controlled at 0.5 - 2 μm, and the two ultrasonic water washings are symmetrically arranged before and after the chemical etching respectively.

[0010] Furthermore, the pickling activation solution is a composite solution of 10 - 15% nitric acid and 3 - 5% hydrofluoric acid, the treatment temperature is 30 - 40 °C, and the time is 30 - 60 seconds.

[0011] Furthermore, the micro-etching adopts a dynamic spraying process, the solution pressure is 0.2 - 0.5 MPa, and it is combined with the mechanical vibration frequency of the stainless steel surface of 50 - 100 Hz to enhance the uniformity of micro-roughness.

[0012] Furthermore, the chemical etching solution contains: 100 - 150 g / L of ferric chloride, 30 - 50 mL / L of hydrochloric acid, 0.5 - 1 g / L of corrosion inhibitor (benzotriazole), the etching temperature is 45 - 55 °C, and the time is controlled at 1 - 5 minutes according to the target pattern accuracy.

[0013] Furthermore, the protection treatment uses a composite film solution containing silane coupling agent and nano-silica, the film-forming thickness is 50 - 100 nm, the baking temperature is 80 - 120 °C, and the time is 20 - 30 minutes.

[0014] Furthermore, all water washing steps adopt real-time monitoring of conductivity. When the conductivity > 50 μS / cm, it is automatically switched to the next-stage water washing tank, and the resistivity of the final ultrasonic water washing is ≥ 1 MΩ·cm.

[0015] Furthermore, the hot water washing adopts gradient heating: the first stage is rinsing at 40 - 50 °C for 1 minute, the second stage is rinsing at 60 - 70 °C for 30 seconds, and the third stage is instantaneous spraying at 80 °C for 5 seconds.

[0016] A stainless steel surface prepared by any of the above processes has a composite structure of periodic micron-scale pits (diameter 5 - 20 μm) and nano-scale oxide layer (thickness 10 - 30 nm) on the surface, and the water contact angle ≥ 110°.

[0017] A continuous production line for implementing the above process includes:

[0018] 14 series-connected tank bodies with modular processing, among which the water washing tanks are equipped with an overflow recovery system;

[0019] Automatic compensation device for the liquid level and concentration of the chemical tank;

[0020] The robotic arm transfer system has a workpiece transfer time of ≤ 10 seconds per station.

[0021] Application of any of the above-mentioned stainless steel surface treatment processes in CCD vision printing and metal nano-injection molding.

[0022] In summary, this application includes at least one of the following treatment processes and application beneficial technical effects on the stainless steel surface:

[0023] 1. Through the synergistic effect of dynamic micro-etching and chemical etching, a composite structure of periodic micron-scale pits and nano-scale oxide layers is formed on the premise of avoiding over-corrosion. The surface area is greatly increased, and the interfacial bonding strength of the subsequent protective film or nano-injection molding material is increased to ≥ 15 MPa, solving the problem of insufficient bonding force caused by traditional sandblasting or pickling;

[0024] 2. Use a micro-etching solution without hydrofluoric acid and a low-toxic corrosion inhibitor to reduce the environmental pollution problem of traditional strong acid processes. Through multi-stage water washing conductivity monitoring and ultrasonic water washing symmetric design, the pollutant residue is reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Schematic diagram of the nanopore size and depth structure mainly provided by this application Figure 1 ;

[0026] Figure 2 Schematic diagram of the nanopore size and depth structure mainly provided by this application Figure 2 ;

[0027] Figure 3 Schematic diagram of the brief process flow mainly provided by this application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0028] In order to make the technical means, creative features, achieved purposes and effects of the present invention easy to understand, the present invention will be further described below with reference to specific embodiments.

[0029] The following is a further detailed description of this application in combination with the attached Figures 1-3 Drawings.

[0030] The embodiment of this application discloses a treatment process and application of the stainless steel surface.

[0031] Embodiment 1

[0032] The pretreatment stage includes ultrasonic degreasing, the first two-stage water washing, pickling activation, and the second two-stage water washing.

[0033] Ultrasonic degreasing: Place the stainless steel workpiece to be processed into an alkaline degreasing solution (30 g / L NaOH, 20 g / L Na2CO3, 5 g / L surfactant). Use 40 kHz ultrasonic waves to clean for 5 minutes at a temperature of 50 °C to remove surface oil stains and particulate contaminants.

[0034] First two-stage water wash:

[0035] First water wash: Spray and rinse with tap water at room temperature for 30 seconds.

[0036] Second water wash: Immerse and rinse in deionized water (conductivity ≤ 10 μS / cm) for 1 minute.

[0037] Pickling and activation

[0038] Use a mixed solution of 10% nitric acid + 3% hydrofluoric acid, at a temperature of 30 °C, soak for 30 seconds to remove the surface oxide layer and activate the metal surface.

[0039] Second two-stage water wash

[0040] First water wash: Spray and rinse with tap water at room temperature for 30 seconds.

[0041] Second water wash: Immerse and rinse in deionized water (conductivity ≤ 10 μS / cm) for 1 minute to ensure complete removal of the acid solution.

[0042] Micro-etching stage, including micro-etching, third two-stage water wash, and first ultrasonic water wash.

[0043] Micro-etching: Use a mixed solution of ammonium persulfate (50 g / L) + citric acid (20 g / L), adopt a dynamic spraying process, with a solution pressure of 0.2 MPa, in conjunction with workpiece vibration (frequency 50 Hz).

[0044] The treatment time is 60 seconds, and the etching depth is about 0.5 μm to form a uniform micro-roughness.

[0045] Third two-stage water wash:

[0046] First water wash: Spray and rinse with tap water at room temperature for 30 seconds.

[0047] Second water wash: Immerse and rinse in deionized water (conductivity ≤ 10 μS / cm) for 1 minute to ensure no residual particles on the surface.

[0048] First ultrasonic water wash: Use 60 kHz ultrasonic waves + deionized water to clean for 3 minutes to ensure no residual particles on the surface.

[0049] Chemical etching stage, including chemical etching, fourth two-stage water wash, second ultrasonic water wash, and fifth two-stage water wash.

[0050] Chemical etching: Etching solution formula:

[0051] Ferric chloride (FeCl3) 100 g / L;

[0052] Hydrochloric acid (HCl) 30 mL / L;

[0053] Benzotriazole (BTA) 0.5 g / L (corrosion inhibitor);

[0054] At a temperature of 45 °C, soak for 1 minute, and etch to form a pattern.

[0055] Fourth two-stage water wash:

[0056] First-stage water wash: Spray-rinse with tap water at room temperature for 30 seconds.

[0057] Second-stage water wash: Soak and rinse in deionized water (conductivity ≤ 10 μS / cm) for 1 minute to remove the residual etching solution.

[0058] Second ultrasonic water wash:

[0059] Clean with 60 kHz ultrasonic waves + deionized water for 3 minutes to ensure a clean surface after etching.

[0060] Fifth two-stage water wash:

[0061] First-stage water wash: Spray-rinse with tap water at room temperature for 30 seconds.

[0062] Second-stage water wash: Rinse with ultrapure water (resistivity ≥ 1 MΩ·cm) to ensure no ion residue.

[0063] Surface protection stage, including surface protection treatment, sixth two-stage water wash, heat treatment, and baking and curing.

[0064] Surface protection treatment:

[0065] Use a composite solution of silane coupling agent (KH-550) + nano-silica (20 nm, 5 wt%), impregnate and coat for 1 minute to form a 50 nm thick protective film.

[0066] Sixth two-stage water wash:

[0067] Slightly rinse to remove the uncured protective liquid.

[0068] Heat treatment:

[0069] Gradient temperature rise cleaning, first stage: Spray at 45 °C for 1 minute, second stage: Rinse at 65 °C for 30 seconds, third stage: Instant spray at 80 °C for 5 seconds, for removing surface moisture.

[0070] Baking and curing:

[0071] Baking temperature 80 °C, time 20 minutes, to completely cure the protective film.

[0072] Example 2

[0073] The pretreatment stage includes ultrasonic degreasing, the first two-stage water washing, pickling activation, and the second two-stage water washing.

[0074] Ultrasonic degreasing: Put the stainless steel workpiece to be processed into an alkaline degreasing solution (NaOH 30g / L, Na2CO3 20g / L, surfactant 5g / L). Use 40kHz ultrasonic wave to clean for 5 minutes at a temperature of 50°C to remove the surface oil and particulate contaminants.

[0075] The first two-stage water washing:

[0076] The first water wash: Spray and rinse with tap water at room temperature for 30 seconds.

[0077] The second water wash: Immerse and rinse in deionized water (conductivity ≤ 10 μS / cm) for 1 minute.

[0078] Pickling activation

[0079] Use a mixed solution of 12% nitric acid + 4% hydrofluoric acid, at a temperature of 35°C, soak for 45 seconds to remove the surface oxide layer and activate the metal surface.

[0080] The second two-stage water washing

[0081] The first water wash: Spray and rinse with tap water at room temperature for 30 seconds.

[0082] The second water wash: Immerse and rinse in deionized water (conductivity ≤ 10 μS / cm) for 1 minute to ensure complete removal of the acid solution.

[0083] The micro-etching stage includes micro-etching, the third two-stage water washing, and the first ultrasonic water washing.

[0084] Micro-etching: Use an ammonium persulfate (50g / L) + citric acid (20g / L) mixed solution, adopt a dynamic spraying process, the solution pressure is 0.3MPa, and cooperate with workpiece vibration (frequency 80Hz).

[0085] The treatment time is 60 seconds, and the etching depth is about 1.2μm to form a uniform micro-roughness.

[0086] The third two-stage water washing:

[0087] The first water wash: Spray and rinse with tap water at room temperature for 30 seconds.

[0088] The second water wash: Immerse and rinse in deionized water (conductivity ≤ 10 μS / cm) for 1 minute to ensure no residual particles on the surface.

[0089] First ultrasonic water wash: Use 60 kHz ultrasonic waves + deionized water to wash for 3 minutes to ensure no residual particles on the surface.

[0090] Chemical etching stage, including chemical etching, the fourth two-stage water wash, the second ultrasonic water wash, and the fifth two-stage water wash.

[0091] Chemical etching: Etching solution formula:

[0092] Ferric chloride (FeCl3) 120 g / L;

[0093] Hydrochloric acid (HCl) 40 mL / L;

[0094] Benzotriazole (BTA) 0.8 g / L (corrosion inhibitor);

[0095] Temperature 50 °C, soak for 3 minutes, and etch to form a pattern.

[0096] Fourth two-stage water wash:

[0097] First water wash: Spray and rinse with tap water at room temperature for 30 seconds.

[0098] Second water wash: Soak and rinse with deionized water (conductivity ≤ 10 μS / cm) for 1 minute to remove residual etching solution.

[0099] Second ultrasonic water wash:

[0100] Use 60 kHz ultrasonic waves + deionized water to wash for 3 minutes to ensure the surface is clean after etching.

[0101] Fifth two-stage water wash:

[0102] First water wash: Spray and rinse with tap water at room temperature for 30 seconds.

[0103] Second water wash: Rinse with ultrapure water (resistivity ≥ 1 MΩ·cm) to ensure no ion residue.

[0104] Surface protection stage, including surface protection treatment, the sixth two-stage water wash, heat treatment, and baking and curing.

[0105] Surface protection treatment:

[0106] Use a composite solution of silane coupling agent (KH-550) + nano-silica (20 nm, 5 wt%) to impregnate and coat for 1 minute to form an 80 nm thick protective film.

[0107] Sixth two-stage water wash:

[0108] Slightly rinse to remove the uncured protective liquid.

[0109] Heat treatment:

[0110] Gradient temperature rise cleaning, first stage: spray at 45°C for 1 minute, second stage: rinse at 65°C for 30 seconds, third stage: instant spray at 80°C for 5 seconds, used to remove surface moisture.

[0111] Baking and curing:

[0112] Baking temperature is 100°C, time is 25 minutes, to fully cure the protective film.

[0113] Example 3

[0114] The pretreatment stage includes ultrasonic degreasing, the first two-stage water wash, pickling activation, and the second two-stage water wash.

[0115] Ultrasonic degreasing: Put the stainless steel workpiece to be processed into an alkaline degreasing solution (NaOH 30g / L, Na2CO3 20g / L, surfactant 5g / L). Use 40kHz ultrasonic cleaning for 5 minutes, temperature 50°C, to remove surface oil stains and particulate contaminants.

[0116] The first two-stage water wash:

[0117] The first water wash: Spray and rinse with tap water at room temperature for 30 seconds.

[0118] The second water wash: Immerse and rinse in deionized water (conductivity ≤ 10 μS / cm) for 1 minute.

[0119] Pickling activation

[0120] Use a mixed solution of 15% nitric acid + 5% hydrofluoric acid, temperature 40°C, soak for 60 seconds, to remove the surface oxide layer and activate the metal surface.

[0121] The second two-stage water wash

[0122] The first water wash: Spray and rinse with tap water at room temperature for 30 seconds.

[0123] The second water wash: Immerse and rinse in deionized water (conductivity ≤ 10 μS / cm) for 1 minute to ensure complete removal of the acid solution.

[0124] The micro-etching stage includes micro-etching, the third two-stage water wash, and the first ultrasonic water wash.

[0125] Micro-etching: Use an ammonium persulfate (50g / L) + citric acid (20g / L) mixed solution, adopt a dynamic spraying process, solution pressure 0.5MPa, combined with workpiece vibration (frequency 100Hz).

[0126] Processing time is 60 seconds, etching depth is about 2μm, to form a uniform micro-roughness.

[0127] The third two-stage water wash:

[0128] First water wash: Spray and rinse with tap water at room temperature for 30 seconds.

[0129] Second water wash: Immerse and rinse in deionized water (conductivity ≤ 10 μS / cm) for 1 minute to ensure no residual particles on the surface.

[0130] First ultrasonic water wash: Clean with 60 kHz ultrasonic wave + deionized water for 3 minutes to ensure no residual particles on the surface.

[0131] Chemical etching stage, including chemical etching, fourth two-stage water wash, second ultrasonic water wash, and fifth two-stage water wash.

[0132] Chemical etching: Etching solution formula:

[0133] Ferric chloride (FeCl3) 150 g / L;

[0134] Hydrochloric acid (HCl) 50 mL / L;

[0135] Benzotriazole (BTA) 1 g / L (corrosion inhibitor);

[0136] Temperature 55 °C, soak for 5 minutes to etch and form a pattern.

[0137] Fourth two-stage water wash:

[0138] First water wash: Spray and rinse with tap water at room temperature for 30 seconds.

[0139] Second water wash: Immerse and rinse in deionized water (conductivity ≤ 10 μS / cm) for 1 minute to remove residual etching solution.

[0140] Second ultrasonic water wash:

[0141] Clean with 60 kHz ultrasonic wave + deionized water for 3 minutes to ensure the surface is clean after etching.

[0142] Fifth two-stage water wash:

[0143] First water wash: Spray and rinse with tap water at room temperature for 30 seconds.

[0144] Second water wash: Rinse with ultrapure water (resistivity ≥ 1 MΩ·cm) to ensure no ion residue.

[0145] Surface protection stage, including surface protection treatment, sixth two-stage water wash, heat treatment, and baking and curing.

[0146] Surface protection treatment:

[0147] Use a composite solution of silane coupling agent (KH-550) + nano-silica (20 nm, 5 wt%) for dip coating for 1 minute to form a 100 nm thick protective film.

[0148] The sixth two-stage water wash:

[0149] Slightly rinse to remove the uncured protective liquid.

[0150] Heat treatment:

[0151] Gradient temperature rise cleaning, the first stage: spray at 45°C for 1 minute, the second stage: rinse at 65°C for 30 seconds, the third stage: instant spray at 80°C for 5 seconds, for removing surface moisture.

[0152] Baking and curing:

[0153] The baking temperature is 120°C and the time is 30 minutes to completely cure the protective film.

[0154] A stainless steel surface after the above treatment process, the surface has a composite structure of periodic micron-scale pits and nano-scale oxide layers, and the water contact angle ≥ 110°. Further, the pit diameter is 5 - 20μm, and the thickness of the nano-scale oxide layer is 10 - 30nm.

[0155] A continuous production line implementing the above process, including:

[0156] 14 series-connected tank bodies with modular processing, and the water wash tank is equipped with an overflow recovery system;

[0157] Automatic compensation device for the liquid level and concentration of the chemical tank;

[0158] Robotic arm transfer system, the workpiece transfer time ≤ 10 seconds / station

[0159] Application of a stainless steel surface treatment process in CCD vision printing and metal nano-injection molding

[0160] Pre-treatment for CCD vision positioning: For the stainless steel surface treated according to Claim 1, the roughness Ra formed by micro-etching is 0.1 - 0.3μm, and the contrast with the chemical etching pattern ≥ 80%, and the positioning error recognized by the CCD camera ≤ ±5μm.

[0161] Enhanced bonding of the nano-injection molding layer: Nano-injection molding is carried out on the stainless steel surface after protective treatment, the injection molding material is PPS or PA6T containing glass fiber, the melting temperature is 280 - 320°C, the injection molding pressure is 80 - 120MPa, and the interfacial bonding strength ≥ 15MPa.

[0162] On-line quality inspection: Use an infrared spectrometer to monitor the chemical bonding peaks (Si-O-Metal characteristic peaks at a wavenumber of 1020 - 1100cm -1 at) of the interface between the injection molding layer and the stainless steel in real time, and combine X-ray detection to check that the porosity of the injection molding layer ≤ 0.5%

[0163] The above are all preferred embodiments of the present application, and do not limit the protection scope of the present application. Therefore, any equivalent changes made according to the structure, shape, and principle of the present application shall be covered within the protection scope of the present application.

Claims

1. A treatment process for the surface of stainless steel, characterized in that, The following steps are included in sequence: Ultrasonic degreasing → first two-step water washing → acid washing and activation → second two-step water washing → micro-etching → third two-step water washing → first ultrasonic water washing → chemical etching → fourth two-step water washing → second ultrasonic water washing → fifth two-step water washing → surface protection treatment → sixth two-step water washing → hot water washing → baking and curing; The micro-etching uses a mixed solution containing persulfate and organic acid, the etching depth is controlled at 0.5-2 μm, and two ultrasonic water washings are symmetrically arranged before and after the chemical etching.

2. The surface treatment process of stainless steel according to claim 1, characterized in that, The pickling activation solution is a composite solution of 10-15% nitric acid and 3-5% hydrofluoric acid, with a treatment temperature of 30-40° C. and a treatment time of 30-60 seconds.

3. The surface treatment process of stainless steel according to claim 1, wherein, The micro-etching adopts a dynamic spraying process with a solution pressure of 0.2-0.5 MPa and a mechanical vibration frequency of 50-100 Hz on the stainless steel surface to enhance the uniformity of microscopic roughness.

4. A surface treatment process for stainless steel according to claim 1, characterized in that, The chemical etching solution comprises: Ferric chloride 100-150g / L, hydrochloric acid 30-50mL / L, corrosion inhibitor (benzotriazole) 0.5-1g / L, etching temperature 45-55°C, time controlled within 1-5 minutes according to the target pattern accuracy.

5. A surface treatment process for stainless steel according to claim 1, characterized in that, The protection treatment uses a composite film liquid containing a silane coupling agent and nano-silicon dioxide, with a film thickness of 50-100nm, a baking temperature of 80-120°C, and a baking time of 20-30 minutes.

6. The surface treatment process of stainless steel according to claim 1, characterized in that, All washing steps are monitored by conductivity in real time. When the conductivity is greater than 50 μS / cm, the system automatically switches to the next washing tank, and the final ultrasonic washing resistivity is ≥1 MΩ·cm.

7. A surface treatment process for stainless steel according to claim 1, characterized in that, The hot water washing adopts a gradient temperature increase: the first stage is 40-50°C for rinsing for 1 minute, the second stage is 60-70°C for rinsing for 30 seconds, and the third stage is 80°C for instant spraying for 5 seconds.

8. A stainless steel surface prepared by any of the processes according to claims 1-7, characterized in that, The surface has a composite structure of periodic micron-scale pits (diameter 5-20 μm) and nano-scale oxide layer (thickness 10-30 nm), and the water contact angle is ≥110°.

9. A continuous production line for implementing the process of claims 1-7, characterized in that, include: 14 series-connected tanks for modular processing, including a wash tank equipped with an overflow recovery system; Chemical tank liquid level and concentration automatic compensation device; Robotic arm transfer system, workpiece transfer time ≤ 10 seconds / station.

10. Application of a stainless steel surface treatment process according to any one of claims 1 to 7 in CCD visual printing and metal nano-injection molding.

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