Stainless steel surface treatment machining process

Abstract

The invention discloses a stainless steel surface treatment processing technology. Comprising the following steps: a) degreasing treatment: degreasing the stainless steel surface by adopting a chemical degreasing or electrochemical degreasing method so as to thoroughly remove oil stains and impurities on the surface; the method comprises the following steps: (a) degreasing stainless steel, (b) dipping the stainless steel, namely dipping the degreased stainless steel into a specific dipping solution, (c) polishing, namely polishing the dipped stainless steel by adopting at least one method of mechanical polishing, electrolytic polishing or chemical polishing, so as to improve the glossiness and flatness of the surface of the stainless steel; and d) activating treatment: activating the polished stainless steel, activating the surface of the stainless steel through a chemical or physical method, enhancing the surface activity of the stainless steel, and facilitating the subsequent processes of coating, welding and the like. The stainless steel surface treatment process has the remarkable beneficial effects of improving the product quality, enhancing the product performance, prolonging the service life, widening the application field and the like.

Description

Technical Field

[0001] The invention relates to the technical field of stainless steel, and in particular to a stainless steel surface treatment process and a preparation method thereof. Background Art

[0002] Stainless steel is widely used in the fields of construction, home appliances, automobile decoration, petrochemical industry, medical machinery and food machinery due to its excellent corrosion resistance. In order to give the surface of stainless steel parts some special physical and chemical properties, it is often electroplated with a certain metal coating to meet the requirements. The electroplated stainless steel not only improves corrosion resistance and wear resistance, but also has bright colors, giving people a sense of magnificence. It is a practical high-end decoration.

[0003] Stainless steel is the abbreviation of stainless acid-resistant steel. Steels that are resistant to weak corrosive media such as air, steam, and water or have stainless properties are called stainless steels; and steels that are resistant to chemical corrosive media (acids, alkalis, salts, etc.) are called acid-resistant steels. Due to the difference in chemical composition between the two, their corrosion resistance is different. Ordinary stainless steel is generally not resistant to chemical media corrosion, while acid-resistant steel is generally rust-resistant. The term "stainless steel" does not simply refer to one type of stainless steel, but refers to more than one hundred types of industrial stainless steel. Each type of stainless steel developed has good performance in its specific application field.

[0004] Austenitic stainless steel (containing 17-25% Cr; 8-25% Ni) has a matrix structure of austenite, is non-magnetic, and cannot be heat treated. The steel grades in the United States and Japan are 300 series, and the typical steel grade is 304, often called 18-8 steel. This series also includes Ni-saving 200 series steel. Due to its good processing performance, mechanical properties, corrosion resistance and welding performance, austenitic stainless steel is the most important type of stainless steel. Its production and use account for about 70% of the total production and use of stainless steel, and the steel grade is also the largest. However, due to its characteristics of being very sensitive to cold work hardening and local corrosion, its scope of use is limited. Electroplating is often required to improve its corrosion resistance and wear resistance, but the current electroplating layer has poor effect, and there is a lack of a surface treatment process that can improve the electroplating effect. A surface corrosion-resistant stainless steel process is provided to address this problem. Summary of the invention

[0005] The purpose of the embodiments of the present application is to provide a stainless steel surface treatment process and a preparation method thereof to solve the problems existing in the related art.

[0006] In order to achieve the above-mentioned object, the present invention provides a stainless steel surface treatment process and a preparation method thereof:

[0007] A stainless steel surface treatment process, characterized in that it comprises the following steps in sequence:

[0008] a) Degreasing: Use chemical degreasing or electrochemical degreasing methods to degrease the stainless steel surface to completely remove the oil and impurities on the surface;

[0009] This scheme adopts electrochemical degreasing, and its components and proportions are as follows: formula sodium hydroxide 30-50g / L, sodium phosphate 20-30g / L, sodium carbonate 20-30g / L, water glass 3-5g / L, current density 3-10A / dm 2 , temperature 60-80℃, cathode 2-6min, anode 2-4min, electrode material is steel plate or nickel-plated steel plate.

[0010] b) Stainless steel immersion process: The degreased stainless steel is immersed in a specific immersion solution, which includes three pickling steps to achieve pickling:

[0011] Loosening oxide scale treatment: loosening the oxide scale on the surface of stainless steel by chemical or physical methods for subsequent treatment;

[0012] Etching treatment: Use mixed acid etching to remove black skin, inclusions and part of the oxide layer on the surface of stainless steel;

[0013] Deashing: Treat in a solution containing a strong oxidant or electrolyze in an alkaline solution to completely remove the gray film remaining on the surface of the stainless steel and improve the surface gloss;

[0014] The stainless steel immersion process of this scheme is convenient for subsequent surface treatment procedures, and must be cleaned before electroplating. In order to effectively remove this oxide film, it also reduces the corrosion of the base metal.

[0015] b) Polishing: Polishing the stainless steel after immersion, using at least one of mechanical polishing, electrolytic polishing or chemical polishing to improve the gloss and flatness of the stainless steel surface;

[0016] d) Activation treatment: The polished stainless steel is activated by chemical or physical methods to activate the stainless steel surface and enhance its surface activity to facilitate subsequent painting, welding and other processes.

[0017] In step b), in the step of loosening the oxide scale, the treatment solution formula is as follows: hydrochloric acid, hydrogen peroxide, phosphoric acid and a surfactant.

[0018] In step b), in the etching step, acid etching is used to remove the film.

[0019] c) Polishing treatment uses electrochemical polishing, the reaction is as follows:

[0020] ① The metal atom loses electrons and turns into metal ions and enters the solution M-2e=M2+;

[0021] ② Formation of oxide film: M+H20-2e=MO+2H+;

[0022] ③Oxygen is released as 2H2O-4e=O2+4H+.

[0023] The polishing liquid formula is: containing the following components and their weight percentages:

[0024] Sulfuric acid: 40%-75%

[0025] Gluten: 3%-60%

[0026] Water: Balance

[0027] The following steps are involved:

[0028] Raw material preparation: Accurately weigh sulfuric acid, gluten and water according to the above weight percentages.

[0029] Mixed dissolution: Slowly add sulfuric acid into water and keep stirring until it is completely dissolved. Then, gradually add gluten under stirring and continue stirring until the gluten is completely dispersed and dissolved in the aqueous sulfuric acid solution.

[0030] d) Activation treatment of zinc plating The activation process is: plating in the zinc plating tank for 1 to 2 minutes, no more than 10 minutes, de-zincifying in 500ml / L hydrochloric acid or sulfuric acid, and then re-galvanizing. The zinc plating adopts cyanide-free zinc plating. The process formula is: zinc oxide 14g / L, sodium hydroxide 130mL / L, cylinder opening agent 17mL / L, brightener

[0031] 1.3mL / L, purifier 2mL / L, cathode current density 2.5A / dm 2 , temperature 26-34℃, time 20-24min.

[0032] The above technical solution has the following beneficial effects:

[0033] By thoroughly removing surface impurities and oxide scale, and forming a denser and more uniform surface layer, the corrosion resistance of stainless steel is significantly improved and the service life of the product is extended.

[0034] The glossiness and flatness of the stainless steel surface are significantly improved after polishing, making the product appearance more beautiful and high-end, and improving the overall quality of the product.

[0035] Activation treatment enhances the activity of the stainless steel surface, making the coating layer more solid and uniform, which is an important step to ensure sufficient adhesion of the electroplating layer.

[0036] Since this process can significantly improve the corrosion resistance, aesthetics and coating of stainless steel products, it can broaden the application areas of stainless steel products and meet the needs of more high-end and precision fields.

[0037] In summary, this stainless steel surface treatment process has significant beneficial effects in improving product quality, enhancing product performance, extending service life, and broadening application areas.

[0038] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, a brief introduction will be given below to what is needed in the embodiments or the description of the prior art. Obviously, the following description is only some embodiments of the present invention. DETAILED DESCRIPTION

[0039] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0040] A stainless steel surface treatment process, characterized in that it includes the following steps in sequence: a) degreasing treatment: using chemical degreasing or electrochemical degreasing method to degrease the stainless steel surface to thoroughly remove the oil and impurities on the surface; this scheme adopts electrochemical degreasing, and its components and proportions are as follows: formula sodium hydroxide 30-50g / L, sodium phosphate 20-30g / L, sodium carbonate 20-30g / L, water glass 3-5g / L, current density 3-10A / dm 2 , temperature 60-80℃, cathode 2-6min, anode 2-4min, electrode material is steel plate or nickel-plated steel plate. To solve the problem that metal is easily contaminated by oil during processing and storage, especially during machining. Some workpieces must be coated with anti-rust oil or anti-rust grease to prevent rust during storage. It is always difficult to avoid organic pollutants such as lubricating oil and grease on the surface of stainless steel products during production and processing. Their presence not only brings disadvantages to heat treatment, but also interferes with subsequent treatments such as pickling and purification.

[0041] b) Stainless steel immersion process: The degreased stainless steel is immersed in a specific immersion solution, which includes three pickling steps to achieve pickling:

[0042] Loosening oxide scale treatment: chemical or physical methods are used to loosen the oxide scale on the surface of stainless steel for subsequent treatment; the pickling is mainly to remove the black skin, inclusions and part of the oxide scale on the surface. Its components and proportions are as follows: hydrochloric acid 300ml / L, hydrogen peroxide 120ml / L, stabilizer 80ml / L, phosphoric acid 60ml / L, surfactant 2ml / L, room temperature treatment time 2-6min. This scheme adopts chemical treatment. It can also be removed by electrochemical method, but the safety requirements are higher.

[0043] Etching treatment: Use mixed acid etching to remove black skin, inclusions and part of the oxide layer on the surface of stainless steel;

[0044] Formula 1: sulfuric acid (mL / L) 230-300, hydrochloric acid (mL / L) 120-15050-70, rhodamine (g / L) 0.3-0.8, temperature t (℃) 42-60, time (min) 25-60.

[0045] The formula is sulfuric acid-hydrochloric acid type: this solution has simple ingredients, good etching effect, and low corrosion to the substrate, but it requires heating, and a layer of black film remains on the surface of the parts after etching. This type is suitable for etching general stainless steel parts.

[0046] Formula 2: hydrochloric acid (mL / L) 50-70, hydrofluoric acid (mL / L) 90-100, nitric acid (mL / L) 170-210, temperature t (℃) 20-30, time t (min) 6-14.

[0047] Formula 2 is nitric acid-sulfuric acid-hydrofluoric acid type: This solution is suitable for etching of precision nickel-chromium stainless steel parts. It has a strong dissolving and loosening effect on the oxide scale, and there is less residue on the surface of the parts after etching. The disadvantage is that it contains toxic hydrofluoric acid, so it must be worked under good ventilation conditions. In addition, the etching solution also has a corrosive effect on the base metal, so the etching time should be strictly controlled.

[0048] Deashing: Treat in a solution containing a strong oxidant or electrolyze in an alkaline solution to completely remove the gray film remaining on the surface of the stainless steel and improve the surface gloss;

[0049] c) Polishing: Polishing the impregnated stainless steel by using at least one of mechanical polishing, electrolytic polishing or chemical polishing to improve the gloss and flatness of the stainless steel surface;

[0050] The above-mentioned etching treatment may not be able to completely remove the oxide film, and a layer of gray film (floating dust) may still adhere to the surface, which has poor gloss and needs to be removed in a solution containing a strong oxidant, or electrolyzed in an alkaline solution to remove this layer of gray film on the surface and ultimately achieve a nearly mirror-like finish.

[0051] c) Polishing treatment uses electrochemical polishing, the reaction is as follows:

[0052] ① The metal atom loses electrons and turns into metal ions and enters the solution M-2e=M2+;

[0053] ② Formation of oxide film: M+H20-2e=MO+2H+;

[0054] ③Oxygen is released as 2H2O-4e=O2+4H+.

[0055] The polishing liquid formula is: containing the following components and their weight percentages:

[0056] Sulfuric acid: 40%-75%

[0057] Gluten: 3%-60%

[0058] Water: Balance

[0059] The following steps are involved:

[0060] Raw material preparation: Accurately weigh sulfuric acid, gluten and water according to the above weight percentages.

[0061] Mixed dissolution: Slowly add sulfuric acid into water and keep stirring until it is completely dissolved. Then, gradually add gluten under stirring and continue stirring until the gluten is completely dispersed and dissolved in the aqueous sulfuric acid solution.

[0062] The above formulas do not contain chromic anhydride and phosphoric acid, successfully solving the problems of wastewater pollution and high cost. It is a new type of pollution-free and environmentally friendly chemical polishing process, and the polishing process conditions adopted are basically unchanged. The electrical conductivity of this scheme is relatively high. The stainless steel products treated with this polishing liquid can greatly improve their surface glossiness. It can be fully mass-produced industrially. The processing cost is very low, and there is no odor during the processing process, which is less harmful and greatly improves the working environment.

[0063] Sulfuric acid: Sulfuric acid is a strong electrolyte, mainly for conducting electricity, which can promote the rapid dissolution of the anode. When it is in a certain proportion with phosphoric acid, it is the main material for polishing. When the content of sulfuric acid is low, the polishing speed is slow and the brightness is poor; when the content is high, the polishing speed is fast, and the brightness is too high, which will make the surface rough.

[0064] When the stainless steel surface is activated by electrolytic polishing, it should be immersed in concentrated hydrochloric acid for film removal and the last process before pre-plating is weak etching. When the surface is stripped and black ash is left, it must be brushed off with a steel brush. The weak etching film removal process formula before stainless steel pre-plating is: sulfuric acid (mL / L) 80-110, temperature t (℃) 40-70, time t (min) 10-45.

[0065] d) Activation treatment: The polished stainless steel is activated by chemical or physical methods to activate the stainless steel surface and enhance its surface activity to facilitate subsequent painting, welding and other processes.

[0066] The galvanizing activation treatment is to plate a thin layer of metallic zinc on the stainless steel and then immerse it in reducing acid.

[0067] Due to the different electrode potentials between zinc and stainless steel, a microbattery is formed in the medium, causing the zinc layer to corrode and dissolve.

[0068] The stainless steel substrate acts as the cathode, and the hydrogen released reduces and activates the oxide film on its surface.

[0069] Thereby improving the bonding strength of the coating. First, a thin layer of zinc is plated on the stainless steel, and then the zinc is removed in an acidic solution. When the zinc layer is dissolved, the hydrogen released reduces and activates the oxide film on the surface of the stainless steel. The process formula is: zinc oxide 14g / L, sodium hydroxide 130mL / L, cylinder opening agent 17mL / L, brightener 1.3mL / L, purifier 2mL / L, cathode current density 2.5A / dm 2 , temperature 26-34℃, time 20-24min.

[0070] The process is as follows: degreasing → etching → galvanizing (1 to 2 minutes, not more than 10 minutes) →

[0071] Zinc stripping layer (immerse in HCl or H2SO4 for a few seconds) → zinc plating → zinc stripping layer → plating the required coating → dehydrogenation treatment.

[0072] Those skilled in the art will readily appreciate other embodiments of the present application after considering the description and practicing the contents disclosed herein. The present application is intended to cover any modification, use or adaptation of the present application, which follows the general principles of the present application and includes common knowledge or customary techniques in the art that are not disclosed in the present application. The description and examples are intended to be exemplary only, and the true scope and spirit of the present application are indicated by the claims.

[0073] It should be understood that the present application is not limited to the precise structures that have been described and shown above, and that various modifications and changes may be made without departing from the scope thereof. The scope of the present application is limited only by the appended claims.

Claims

1. A stainless steel surface treatment process, characterized in that: The following steps are included in sequence: a) Degreasing: Use chemical degreasing or electrochemical degreasing methods to degrease the stainless steel surface to completely remove the oil and impurities on the surface; b) Stainless steel immersion process: The degreased stainless steel is immersed in a specific immersion solution, which includes three pickling steps to achieve pickling: Loosening oxide scale treatment: loosening the oxide scale on the surface of stainless steel by chemical or physical methods for subsequent treatment; Etching treatment: Use mixed acid etching to remove black skin, inclusions and part of the oxide layer on the surface of stainless steel; Deashing: Treat in a solution containing a strong oxidant or electrolyze in an alkaline solution to completely remove the gray film remaining on the surface of the stainless steel and improve the surface gloss; c) Polishing: Polishing the impregnated stainless steel by using at least one of mechanical polishing, electrolytic polishing or chemical polishing to improve the gloss and flatness of the stainless steel surface; d) Activation treatment: The polished stainless steel is activated by chemical or physical methods to activate the stainless steel surface and enhance its surface activity to facilitate subsequent painting, welding and other processes.

2. A stainless steel surface treatment process according to claim 1, characterized in that: In step b), in the step of loosening the oxide scale, the treatment solution formula is as follows: hydrochloric acid, hydrogen peroxide, phosphoric acid and a surfactant.

3. A stainless steel surface treatment process according to claim 1 or 2, characterized in that: In step b), in the etching step, acid etching is used to remove the film.

4. A stainless steel surface treatment process according to claim 1 or 2, characterized in that: c) Polishing treatment uses electrochemical polishing, the reaction is as follows: ① The metal atom loses electrons and turns into metal ions and enters the solution M-2e=M2+; ② Formation of oxide film: M+H20-2e=MO+2H+; ③Oxygen is released as 2H2O-4e=O2+4H+.

5. A stainless steel surface treatment process according to claim 4, characterized in that: The polishing liquid formula is: containing the following components and their weight percentages: Sulfuric acid: 40%-75% Gluten: 3%-60% Water: Balance The following steps are involved: Raw material preparation: Accurately weigh sulfuric acid, gluten and water according to the above weight percentages. Mixed dissolution: Slowly add sulfuric acid into water and keep stirring until it is completely dissolved. Then, gradually add gluten under stirring and continue stirring until the gluten is completely dispersed and dissolved in the aqueous sulfuric acid solution.

6. A stainless steel surface treatment process according to claim 1, characterized in that: d) Activation treatment The activation process of zinc plating is: plating in the zinc plating tank for 1 to 2 minutes, no more than 10 minutes, dezincifying in 500ml / L hydrochloric acid or sulfuric acid, and then re-galvanizing. The zinc plating adopts cyanide-free zinc plating. The process formula is: zinc oxide 14g / L, sodium hydroxide 130mL / L, cylinder opening agent 17mL / L, brightener 1.3mL / L, purifier 2mL / L, cathode current density 2.5A / dm 2 , temperature 26-34℃, time 20-24min.