Surface treatment method for improving corrosion resistance of 304 copper-containing antibacterial stainless steel

Abstract

The invention discloses a surface treatment method for improving corrosion resistance of 304 copper-containing antibacterial stainless steel. The surface treatment method comprises the steps that 1, the surface of a 304 copper-containing antibacterial stainless steel plate to be treated is polished, cleaned and dried; 2, the surface of the plate is subjected to sand blasting treatment, and vibration cleaning is conducted after sand blasting is completed; 3, high-speed static friction treatment is conducted on the surface of the plate; 4, top-layer oxide skin in a static friction influence area on the surface of the stainless steel plate is removed, and light grinding and polishing are conducted; step 5, carrying out final surface cleaning and drying treatment on the 304 copper-containing antibacterial stainless steel plate subjected to surface treatment; according to the method for conducting sand blasting and static friction treatment on the surface of the commercial 304 copper-containing stainless steel, the grain size of the surface of the stainless steel is reduced, the structure uniformity of the stainless steel is improved, the service life of the stainless steel in a corrosive environment is prolonged, the surface treatment method is simple in process, efficient and free of pollution, and the corrosion resistance of the material is obviously improved.

Description

Technical Field

[0001] The invention relates to the technical field of metal surface treatment, and more particularly to a surface treatment method for improving the corrosion resistance of 304 copper-containing antibacterial stainless steel. Background Art

[0002] In the fields of life and engineering, 304 stainless steel is a widely used metal material with advantages such as high strength, easy processing, and corrosion resistance. However, it is prone to microbial corrosion in the relatively humid environment of the ocean and the south, so many researchers have added copper, a broad-spectrum antibacterial element, to 304 stainless steel and developed 304 copper-containing (304-Cu) antibacterial stainless steel materials to kill bacteria and microbial erosion encountered by stainless steel materials in different application scenarios. However, after adding copper, due to the dispersion and precipitation of large-sized copper-rich phases, the mechanical and corrosion resistance of 304-Cu stainless steel will drop sharply. Summary of the invention

[0003] The present invention is to solve one of the above technical problems and provide a surface treatment method for improving the corrosion resistance of 304 copper-containing antibacterial stainless steel, overcoming the problems of coarse grain size, uneven organizational composition, agglomeration of dispersed precipitate phases, and poor corrosion resistance of existing 30 copper-containing antibacterial stainless steel. By sandblasting and static friction treatment on the surface of commercial 304 copper-containing stainless steel, the grain size of the stainless steel surface is reduced, the organizational uniformity of the stainless steel and its service life in a corrosive environment are improved. This surface treatment method is simple in process, highly efficient and pollution-free, and the corrosion resistance of the material is significantly improved.

[0004] The technical solution adopted by the present invention to solve its technical problem is: A surface treatment method for improving the corrosion resistance of 304 copper-containing antibacterial stainless steel comprises the following steps: Step 1, polishing, cleaning and drying the surface of the 304 copper-containing antibacterial stainless steel plate to be treated; Step 2, sandblasting the surface of the plate, and vibrating and cleaning it after sandblasting; Step 3, performing high-speed static friction treatment on the surface of the plate; Step 4, remove the top oxide scale in the area affected by static friction on the surface of the stainless steel plate, and lightly grind and polish; Step 5, performing final surface cleaning and drying treatment on the surface treated 304 copper-containing antibacterial stainless steel sheet.

[0005] The above technical solution uses the method of surface sandblasting and static friction processing to realize the non-directional physical migration of elements on the surface of 304-Cu antibacterial stainless steel, and makes the organization of 304-Cu stainless steel uniform and the grains ultra-fine without changing the chemical composition of the material, thereby significantly improving the corrosion resistance of commercial 304-Cu antibacterial stainless steel. The surface treatment method proposed in the present invention is mainly divided into two steps: first, through a certain degree of sandblasting, the stainless steel surface is cleaned, the roughness of the stainless steel surface is increased, and the friction between the stirring head and the stainless steel during the static friction process is increased; second, the 304-Cu stainless steel surface is subjected to static friction treatment by a high-strength tool, the size of the 304-Cu stainless steel grains and dispersed precipitate phases is refined, and the corrosion resistance of the stainless steel is improved. The 304-Cu stainless steel surface treatment method of the present invention has the following main advantages: (1) The surface treatment process is a process of reshaping the surface structure of the stainless steel itself, and there is no problem of coating shedding and environmental pollution; (2) The sandblasting and static friction treatment process is highly controllable, and the thickness of the material surface deformation layer can be freely adjusted according to different application environments, which is simple and economical; (3) Compared with long-term homogenization annealing treatment, the 304-Cu antibacterial stainless steel treated by sandblasting and static friction has a more uniform surface structure, finer grains, and better corrosion resistance. (4) Sandblasting and static friction treatment do not have high requirements on the substrate, and can achieve surface optimization treatment of a full range of stainless steels, which is suitable for various application scenarios.

[0006] Preferably, in step 1, the plate is cut from a stainless steel substrate by low-speed wire cutting, and after being polished by a machine tool, the roughness of the plate processing surface is controlled within Ra0.3, thereby shortening the polishing time of subsequent large-size plates on the machine tool and saving energy.

[0007] Preferably, after the plate is polished in step 1, it can also be cleaned and dried.

[0008] Preferably, the abrasive for sandblasting in step 2 is Al2O3 particles with a particle size of 50 to 200 meshes, the sandblasting pressure is 0.2 to 0.5Mpa, the sandblasting jet is 90°, the distance between the nozzle and the surface of the plate is 2 to 5cm, and the sandblasting time is 5 to 20min. Al2O3 particles have a high hardness, and the sandblasting effect is poor if the particle size is small. Excessive particle size may cause tiny cracks on the surface of the plate, so the particle size needs to be controlled at 50 to 200 meshes, and the sandblasting pressure is controlled at a pressure range of 0.2 to 0.5Mpa. Favorable compressive stress and uniform roughness can be formed on the surface of the plate; the sandblasting jet angle is a vertical angle of 90° to avoid deformation of the plate surface or formation of a textured organization; the distance between the nozzle and the surface of the plate is 2 to 5cm, and this distance range can enable the abrasive to obtain more efficient kinetic energy, and the sandblasting time should not be too long or too short, and it is best to control it at 5 to 20min.

[0009] Preferably, in step 3, high-strength, high-temperature resistant tungsten carbide rods are used as additive tools to perform high-speed static friction treatment on the surface of the plate, the rod speed is 300-500rpm, and the diameter of the tungsten carbide rod is 10-15mm. The rod speed is set according to the temperature rise and flow capacity of the plate surface during the friction of the stirring rod, and the present invention is set to 300-500rpm; the selection of tungsten carbide rods should avoid inefficiency caused by too thin rods, and also avoid difficulties in starting the machine tool caused by too thick rods. It is more appropriate to control the diameter to 10-15mm.

[0010] Preferably, the final pressing depth of the rod is 0.15-1.00 mm, the pressing speed is 0.03-0.05 mm / min, and the static friction time is 5-20 min. Since the surface treatment method designed by the present invention does not have the problem of coating shedding, the pressing depth of the rod does not need to be too deep, which can save energy and improve efficiency. In addition, the pressing speed and friction time of the rod will seriously affect the organizational structure and homogenization level of the surface layer. If the static friction time is too short, the flow of the material elements will be uneven, and if the time is too long, holes may be formed on the surface of the material.

[0011] Preferably, in step 4, the method of removing the oxide scale on the surface of the stainless steel plate is shallow grinding and micro-polishing to ensure the retention of the surface treatment layer.

[0012] Preferably, in step five, the cleaning method is ultrasonic cleaning, and the drying method is air drying in a vacuum drying oven and packaging.

[0013] The technical solution provided by the present invention has the following beneficial effects.

[0014] The present invention provides a surface treatment method for improving the corrosion resistance of 304 copper-containing antibacterial stainless steel. Through simple two-step surface treatment of sandblasting and static friction, a thickness-controllable fine grain and uniform area can be prepared on the surface of the commonly used 304-Cu antibacterial stainless steel, solving the problem of poor corrosion resistance of commercial 304-Cu antibacterial stainless steel. Sandblasting pretreatment can clean the metallurgical surface of stainless steel and increase the friction between the stainless steel substrate and the stirring rod. The static friction method can promote the homogenization of elements on the surface of 304-Cu stainless steel through physical migration, avoid long-term high-temperature homogenization annealing of the material, reduce time cost, and significantly improve the corrosion resistance of 304-Cu stainless steel. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is the microstructure characteristics of commercial 304 copper-containing antibacterial stainless steel before and after surface treatment in the embodiment of the present invention, wherein: Figure 1 (a) is the microstructure of commercial 304 copper-containing antibacterial stainless steel. Figure 1(b) is the microstructure of 304 copper-containing stainless steel after surface treatment.

[0017] Figure 2 It is the potentiodynamic polarization curve of the commercial 304 copper-containing antibacterial stainless steel before and after the surface treatment in the embodiment of the present invention in 3.5 wt.% NaCl aqueous solution.

[0018] Figure 3 is the corrosion morphology of commercial 304 copper-containing antibacterial stainless steel before and after surface treatment in Example 1, wherein Figure 3 (a) is the surface corrosion morphology of commercial 304 copper-containing antibacterial stainless steel. Figure 3 (b) is the surface corrosion morphology of 304 copper-containing stainless steel after surface treatment. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical solutions and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with specific embodiments; it should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. For those skilled in the art, other systems, methods and / or features of the present embodiment will become apparent after reviewing the following detailed description. It is intended that all such additional systems, methods, features and advantages are included in this specification, are included within the scope of the present invention, and are protected by the appended claims. Additional features of the disclosed embodiments are described in detail below, and these features will be apparent from the following detailed description.

[0021] The following is a detailed description of a surface treatment method for improving the corrosion resistance of 304 copper-containing antibacterial stainless steel according to the present invention through a specific implementation method.

[0022] Example 1

[0023] A surface treatment method for improving the corrosion resistance of 304 copper-containing antibacterial stainless steel in Example 1 includes the following steps: Step 1: Cut the commercial 304-Cu antibacterial stainless steel sheet into 3 cm × 10 cm sheets by wire cutting. The components of the 304-Cu stainless steel used in this embodiment include iron, chromium, nickel, copper, manganese, silicon, and carbon, and their mass percentages are approximately: 69.66: 17.01: 7.85: 4.08: 0.99: 0.40: 0.01; in other embodiments, it can be cut into sheets of other sizes, and 304 copper-containing stainless steel with other components can also be used, which does not affect the implementation of the surface treatment method of the present invention.

[0024] Step 2: Use a grinding and polishing machine to roughly grind the cut stainless steel substrate surface to a surface roughness of R0.2, and then clean and dry it. In other embodiments, the surface roughness can also be other values, preferably within the range of R0.3 for better results.

[0025] Step 3: Sandblast the surface of the substrate, select Al2O3 particles with a particle size of 100 mesh, spray angle of 90°, nozzle 3 cm away from the substrate surface, sandblasting pressure 0.3 MPa, sandblasting time 8 min. After sandblasting, put the substrate into clean water for vibration cleaning, and then clamp it on a flat machine tool; Step 4: Clamp a tungsten carbide rod with a length of 40 mm and a diameter of 15 mm on a motor-controlled fixture, and move the fixture to the area above the 304-Cu stainless steel where surface static friction treatment is required; Step 5: Turn on the motor for static friction treatment, set the rotation speed of the tungsten carbide rod to 400 rpm, the rotation friction time to 10 min, the pressing speed to 0.03 mm / min, and the final pressing depth to 0.3 mm; Step 6: After surface treatment, remove the 304-Cu stainless steel and perform shallow grinding and micro-polishing on the treated surface to remove the oxide scale.

[0026] Step 7: Ultrasonic cleaning is performed on the final material, and the material is dried in a vacuum drying oven and packaged for later use.

[0027] In order to verify the optimization effect of the surface treatment method of the present invention on 304-Cu stainless steel, this example conducted a test on the uniformity of the structure and the corrosion resistance of 304-Cu stainless steel before and after the surface treatment; Experiment 1: Cut the 304-Cu stainless steel material before and after surface treatment into small samples of 5 mm × 5 mm × 5 mm. Use 800~3000 mesh SiC sandpaper to water-grind the surface of the sample for a short time step by step, and then use 1.5 μm diamond polishing paste to polish the sample to remove scratches. Put the mechanically polished sample into an argon ion polisher and polish the 1mm × 1 mm area on its surface. First, use a higher voltage to remove the stress layer on the surface of the 304-Cu stainless steel, and then switch to a low voltage for surface finishing. Use the electron backscatter diffraction system in the scanning electron microscope to calibrate and observe the surface of the sample before and after surface treatment. Figure 1 It can be seen that the grain size of commercial 304-Cu antibacterial stainless steel is relatively large, and there is a small amount of coarse twin structure inside the large grains. After surface treatment, the grain boundaries on the stainless steel surface increase sharply and the grain size decreases significantly.

[0028] Experiment 2: The 304-Cu stainless steel before and after surface treatment was cut into standard electrochemical samples of 10 mm × 10 mm × 3 mm, and the corrosion resistance was tested in a 3.5% mass fraction NaCl aqueous solution. The potentiodynamic polarization test adopted a three-electrode system, with a platinum electrode as the counter electrode, a saturated calomel electrode as the reference electrode, and the polished surface of the 304-Cu stainless steel before and after surface treatment as the working electrode. The preparation method of the electrochemical sample is as follows: the back of the stainless steel sample is bonded to the wire using epoxy conductive glue, and after the bonding is firm, the sample is encapsulated with epoxy resin, and an area of ​​10 mm × 10 mm on the surface of the sample is exposed as the test area. The sample was clamped and fixed in a 3.5% NaCl aqueous solution, and an open circuit potential test was performed until the potential was stable, and then a potentiodynamic polarization curve test was performed with a scanning range of -0.4 V~0.32 V and a scanning speed of 0.33 mV / s. The polarization curve obtained in the test is as follows Figure 2 As shown. It can be seen that the passivation zone of the original 304-Cu antibacterial stainless steel is narrow, the self-corrosion potential is low, the corrosion current density is high, and the corrosion rate of the material is fast. After surface treatment, the passivation zone of the sample is significantly widened, the pitting breakdown potential is increased from -44.1 mV to 67.3 mV, and the corrosion current density is reduced from 0.214 μA·cm-2 to 0.048 μA·cm-2. The experimental results show that the corrosion resistance of 304-Cu antibacterial stainless steel is significantly improved after sandblasting and static friction treatment.

[0029] Experiment 3: After completing the potentiodynamic polarization curve test, the 304-Cu antibacterial stainless steel samples before and after surface treatment were removed, cleaned with acetone and anhydrous ethanol ultrasonic vibration, and then dried, and the corrosion morphology was observed using a scanning electron microscope. Figure 3 As shown, it can be clearly observed that there are many irregular corrosion holes on the surface of the original 304-Cu stainless steel sample, showing clear small-sized round holes and large-sized pits. After surface treatment, the surface of the 304-Cu stainless steel sample is relatively smooth, with only a small number of small-sized metastable pitting pits. It can be seen that the surface treatment method proposed in the present invention significantly improves the corrosion resistance of 304-Cu antibacterial stainless steel.

[0030] Example 2

[0031] A surface treatment method for improving the corrosion resistance of 304 copper-containing antibacterial stainless steel in this embodiment 2 comprises the following steps: Step 1: Cut the commercial 304-Cu antibacterial stainless steel sheet into 5 cm × 5 cm sheets by wire cutting. The composition of the 304-Cu stainless steel used in this embodiment includes iron, chromium, nickel, copper, manganese, silicon, and carbon, and their mass percentages are approximately: 68.2: 16.9: 7.9: 5.5: 0.99: 0.50: 0.01; Step 2: Use a grinding and polishing machine to roughly grind the surface of the cut stainless steel substrate to a surface roughness of R0.1, then clean and dry it.

[0032] Step 3: Sandblast the surface of the substrate, select Al2O3 particles with a particle size of 200 mesh, spray angle of 90°, nozzle 5 cm away from the substrate surface, sandblasting pressure 0.2 MPa, sandblasting time 5 min. After sandblasting, put the substrate into clean water for vibration cleaning, and then clamp it on a flat machine tool; Step 4: Clamp a tungsten carbide rod with a length of 40 mm and a diameter of 10 mm on a motor-controlled fixture, and move the fixture to the area above the 304-Cu stainless steel where surface static friction treatment is required; Step 5: Turn on the motor for static friction treatment, set the rotation speed of the tungsten carbide rod to 500 rpm, the rotation friction time to 20 min, the pressing speed to 0.03 mm / min, and the final pressing depth to 0.15 mm; Step 6: After surface treatment, remove the 304-Cu stainless steel and perform shallow grinding and micro-polishing on the treated surface to remove the oxide scale.

[0033] Step 7: Ultrasonic cleaning is performed on the final material, and the material is dried in a vacuum drying oven and packaged for later use.

[0034] Example 3

[0035] A surface treatment method for improving the corrosion resistance of 304 copper-containing antibacterial stainless steel in this embodiment 3 comprises the following steps: Step 1: Cut the commercial 304-Cu antibacterial stainless steel sheet into 2 cm × 6 cm sheets by wire cutting. The composition of the 304-Cu stainless steel used in this embodiment includes iron, chromium, nickel, copper, manganese, silicon, and carbon, and their mass percentages are approximately: 69.66: 17.01: 7.85: 4.08: 0.99: 0.40: 0.01.

[0036] Step 2: Use a grinding and polishing machine to roughly grind the surface of the cut stainless steel substrate to a surface roughness of R0.3, then clean and dry it.

[0037] Step 3: Sandblast the substrate surface, select Al2O3 particles with a particle size of 50 mesh, spray angle of 90°, nozzle 2 cm away from the substrate surface, sandblasting pressure of 0.5 MPa, and sandblasting time of 20 minutes. After sandblasting, put the substrate into clean water for vibration cleaning, and then clamp it on a flat machine tool; Step 4: Clamp a tungsten carbide rod with a length of 40 mm and a diameter of 10 mm on a motor-controlled fixture, and move the fixture to the area above the 304-Cu stainless steel where surface static friction treatment is required; Step 5: Turn on the motor for static friction treatment, set the rotation speed of the tungsten carbide rod to 300 rpm, the rotation friction time to 20 min, the pressing speed to 0.05 mm / min, and the final pressing depth to 1 mm; Step 6: After surface treatment, remove the 304-Cu stainless steel and perform shallow grinding and micro-polishing on the treated surface to remove the oxide scale.

[0038] Step 7: Ultrasonic cleaning is performed on the final material, and the material is dried in a vacuum drying oven and packaged for later use.

[0039] In summary, the present invention provides a surface treatment method for improving the corrosion resistance of 304 copper-containing antibacterial stainless steel. First, the sandblasting treatment on the surface of the material can improve the cleanliness of the substrate surface, increase the surface roughness of the 304-Cu stainless steel, and increase the friction between the 304-Cu stainless steel and the tungsten carbide rod in the subsequent static friction process, so that the static friction effect is better. The principle of static friction treatment is to drive the high-strength tungsten carbide rod and the substrate to perform high-speed friction through a motor, causing strong plastic deformation on the surface of the substrate. During the friction process, the substrate is subjected to high temperature and plastic deformation force, which promotes the full flow of elements on the surface of the material, so that the material shows the refinement of grains and dispersed phases, and has the advantages of small deformation, high strength, and controllable thickness of the deformation layer. The surface sandblasting combined with static friction surface treatment method, on the one hand, does not change the original elemental composition of the material, so the composition can maintain the antibacterial properties of antibacterial stainless steel; on the other hand, static friction can make the stainless steel surface grains more refined and the composition more uniform. Compared with the long-term high-temperature annealing commonly used for stainless steel homogenization, static friction can complete the processing of specific parts of the stainless steel surface in a very short time, solving the problem of poor corrosion resistance of copper-containing stainless steel. In addition, sandblasting and static friction treatment do not have high requirements on the substrate, and can achieve surface optimization treatment of the entire series of stainless steel, suitable for various application scenarios.

[0040] The above embodiments should be understood to be only used to illustrate the present invention and not to limit the protection scope of the present invention. After reading the contents of the present invention, technicians can make various changes or modifications to the present invention, and these equivalent changes and modifications also fall within the scope defined by the claims of the present invention.

Claims

1. A surface treatment method for improving the corrosion resistance of 304 copper-containing antibacterial stainless steel, characterized in that: The steps include: Step 1, polishing the surface of the 304 copper-containing antibacterial stainless steel plate to be treated; Step 2, sandblasting the surface of the plate, and vibrating and cleaning it after sandblasting; Step 3, performing high-speed static friction treatment on the surface of the plate; Step 4, remove the top oxide scale in the area affected by static friction on the surface of the stainless steel plate, and lightly grind and polish; Step 5, performing final surface cleaning and drying treatment on the surface treated 304 copper-containing antibacterial stainless steel sheet.

2. A surface treatment method according to claim 1, characterized in that: In step 1, the plate is cut from a stainless steel substrate by low-speed wire cutting. After being polished by a machine tool, the roughness of the plate processing surface is controlled within Ra0.

3.

3. A surface treatment method according to claim 1, characterized in that: After the board is polished in step 1, it can also be cleaned and dried.

4. A surface treatment method according to claim 1, characterized in that: The abrasive for sandblasting in step 2 is Al2O3 particles with a particle size of 50-200 mesh, the sandblasting pressure is 0.2-0.5 MPa, the sandblasting jet is 90°, the distance between the nozzle and the plate surface is 2-5 cm, and the sandblasting time is 5-20 min.

5. A surface treatment method according to claim 1, characterized in that: In step 3, a high-strength, high-temperature resistant tungsten carbide rod is used as an additive tool to perform high-speed static friction treatment on the surface of the plate. The rod rotation speed is 300-500 rpm, and the diameter of the tungsten carbide rod is 10-15 mm.

6. A surface treatment method according to claim 5, characterized in that: The final pressing depth of the rod is 0.15~1.00mm, the pressing speed is 0.03-0.05 mm / min, and the static friction time is 5~20min.

7. A surface treatment method according to claim 1, characterized in that: In step 4, the method of removing the oxide scale on the surface of the stainless steel plate is shallow grinding and micro-polishing.

8. A surface treatment method according to claim 1, characterized in that: In step 5, the cleaning method is ultrasonic cleaning, and the drying method is air drying in a vacuum drying oven and packaging.

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