The variety of surface processing of stainless steel broadens its application field – different surface processing makes the surface of stainless steel different, making it unique in application.
Surface finishing of stainless steel pipe is important for many reasons in architectural applications.
Corrosive environments require smooth surfaces because smooth surfaces are not prone to fouling. The deposition of dirt will rust or even cause corrosion of stainless steel. In the spacious hall, stainless steel is the most commonly used material for elevator decorative panels. Although fingerprints on the surface can be wiped off, it affects the appearance, so it is best to choose a suitable surface to prevent fingerprints. Hygienic conditions are very important to many industries, such as food processing, catering, brewing, and chemical industry, etc. In these application areas, the surface must be easy to clean every day, and chemical cleaning agents are often used. Stainless steel is the best material for this. In public places, the surface of stainless steel is often scribbled on. However, one of its important properties is that it can be washed away. This is a remarkable feature of stainless steel over aluminum. Aluminum surfaces tend to leave marks that are often difficult to remove. When cleaning the surface of stainless steel, it should be cleaned along the lines of stainless steel, because some surface processing lines are unidirectional. Stainless steel is most suitable for hospitals or other areas where hygiene is critical, such as food processing, catering, brewing, and the chemical industry, not only because it is easy to clean every day, sometimes using chemical cleaning agents, but also because it is not easy to breed bacteria. Tests have shown that stainless steel performs the same as glass and ceramics in this respect.
1. The Natural Appearance of Stainless Steel has a natural solid look, with natural colors that softly reflect the colors of its surroundings.
2. Basic types of surface processing There are roughly five types of surface processing that can be used for stainless steel, and they can be used in combination to transform more final products. The five types are rolling surface processing, mechanical surface processing, chemical surface processing, textured surface processing, and color surface processing. There are also specialized finishes, but whichever one is specified, the following steps should be followed:
①Agreement with the manufacturer on the required surface processing, it is best to prepare a sample as a standard for future mass production.
② When used in a large area (such as composite panels, it must be ensured that the base coils or coils used are of the same batch.
③In many architectural applications, such as: inside the elevator, although the fingerprints can be wiped off, they are very unsightly. If you choose a textured surface, it is not so obvious. Mirror stainless steel must not be used in these sensitive places.
④ When selecting surface processing, the production process should be considered. For example, to remove the welding beads, the weld seam may be ground and the original surface processing must be restored. Checkered plates are difficult or even impossible to meet this requirement.
⑤ For some surface processing, grinding or polishing lines are directional, called unidirectional. If the texture is vertical instead of horizontal, the dirt will not easily adhere to it, and it will be easy to clean.
⑥ No matter what kind of finishing process is used, it needs to increase the process steps, so it will increase the cost. Therefore, be careful when choosing surface processing. Therefore, relevant personnel such as architects, designers, and manufacturers need to have an understanding of the surface processing of stainless steel. Through friendly cooperation and mutual communication between each other, the desired effect will be obtained.
⑦According to our experience, we do not recommend using aluminum oxide as an abrasive unless very careful during use. Preferably silicon carbide abrasives are used.
3. Standard Surface Finish Many kinds of surface finish have been represented by numbers or other classification methods, and they have been incorporated into relevant standards, such as: “British Standard BS1449″ and “American Iron and Steel Institute Stainless Steel Producers Committee Standard”.
4. Rolling Surface Finishes There are three basic rolled surface finishes for plate and strip, which are represented by the production process of the plate and strip village.
No.1: After hot rolling, annealing, pickling, and descaling. The surface of the treated steel plate is dull and somewhat rough.
No.2D: Better surface finish than N0.1, but also dull surface. After cold rolling, annealing, descaling, and finally light rolling with rough surface rollers.
No.2B: This is the most commonly used in architectural applications. Except for the last light cold rolling with polishing rolls after annealing and descaling, the other processes are the same as 2D. The surface is slightly shiny and can be polished.
No.2B Bright Annealed: This is a reflective finish that is polished roll rolled and finally annealed in a controlled atmosphere. Bright annealing still maintains its reflective surface and does not produce scale. Since no oxidation reaction occurs during the bright annealing process, no pickling and passivation treatment is required.
5. Polished surface processing
No.3: represented by 3A and 3B. ” 3A: The surface is evenly ground, and the abrasive particle size is 80~100. 3B: The rough surface is polished, and the surface has uniform straight lines. become.
No.4: Unidirectional surface finish, not very reflective, this finish is probably the most versatile in architectural applications. The process steps are firstly polished with coarse abrasives and finally ground with abrasives with a particle size of 180.
No.6: It is a further improvement on No.4, which is to polish No. with Tampico polishing brush in abrasive and oil medium. 4 surfaces. This surface finish is not included in “British Standard 1449″, but can be found in the American Standard. No.7: It is called bright polishing, which is to polish the surface that has been ground very finely but still has wear marks. Usually, 2A or 2B boards are used, with fiber or cloth polishing wheels and corresponding polishing pastes.
No.8: Mirror polished surface with high reflectivity, usually called mirror surface processing, because the reflected image is very clear. Continuous polishing of stainless steel with fine abrasives followed by very fine polishing pastes. In architectural applications, it should be noted that if this surface is used in a place with a large flow of people or where people often touch it, it will leave fingerprints. Of course, fingerprints can be wiped off, but sometimes it affects the appearance. Surface finishes described in “official” standards and literature are only general introductions, and samples are the most intuitive representation of the type of surface finish. Polishing or metal finishing manufacturers will provide samples of various surface finishes and users should discuss them with them.
6. Surface roughness The classification of rolling surface processing and polishing surface processing is to indicate the degree that can be achieved. Another effective way of expressing is to measure surface roughness. The standard method of measurement is called CLA (Center Line Average), where the gage is moved across the surface of the steel plate, recording the magnitude of the peaks and valleys. The lower the number of CLA, the smoother the surface. The results of the different grades can be seen from the surface finishes and CLA numbers in the table below.
7. Mechanical polishing
A word of caution: We should remember that grinding with sandpaper or belts in grinding operations is essentially a buff-cutting operation, leaving very fine lines on the surface of the steel plate. We have had trouble with alumina as an abrasive, partly because of pressure issues. Any grinding parts of the equipment, such as abrasive belts and grinding wheels, must not be used for other non-stainless steel materials before use. Because this will contaminate the stainless steel surface. To ensure the consistency of the surface finish, the new grinding wheel or abrasive belt should be tried on the scrap of the same composition first, so that the same sample can be compared.
8. Electropolishing This is a metal removal process in which stainless steel is used as an anode in an electrolytic solution and the metal is removed from the surface when an electric current is applied. The process is often used on components whose shapes are difficult to polish using traditional methods. This process is often used on the surface of cold-rolled steel sheets because the surface is smoother than that of hot-rolled steel sheets. However, electropolishing will make the surface impurities more obvious, especially titanium and niobium-stabilized materials will cause differences in the weld zone due to granular impurities. Small weld scars and sharp edges can be removed by this process. The process focuses on protruding parts of the surface, preferentially dissolving them. The electropolishing process involves immersing stainless steel in a heated liquid, and the ratio of the liquid involves many proprietary technologies and patented technologies. Electropolishing works well for austenitic stainless steel.
9. Textured surface processing many types of patterns can be used for stainless steel. The advantages of adding a pattern or textured surface to the steel plate are as follows:
①Reduce “oil canning”, a term used to describe the surface of bright materials, which is not flat from an optical point of view. For example large-area decorative panels, even after stretching or tension straightening, it is difficult to make the surface completely straight, so there will be shrinkage of metal roofing materials.
②The mesh pattern can reduce the glare emitted in the sun.
③ If the checkered plate has slight scratches and small area indentations, it is not obvious.
④ Increase the strength of the steel plate.
⑤ provide architects with a choice. Patented patterns include cloth (used for the Ed Building in London), mosaic, pearl, and leather. Moiré and linear patterns are also available. The textured surface is particularly suitable for interior decoration such as elevator panels, counters, wall panels, and entrances. When applying externally, it should be considered that the stainless steel can be cleaned with rainwater and manual washing, to avoid dead corners that are easy to accumulate dirt and airborne impurities, so as not to cause corrosion and affect the appearance.
10. rough surface processing
Rough surface processing is one of the most commonly used surface processing. It is polished or polished with a nylon abrasive belt or brush on the surface of a polished or bright annealed steel plate.
11. Spray glass ball or shot blast
For interior applications, such as elevator interiors, mixed surface finishes are popular. This hybrid process is to form a matte surface by spraying glass balls, and then cover it with a plastic film to form a polished surface, and finally form a polished and matte mixed surface. Stainless steel shot can also be used in a similar process. The glass spheres or pellets to be used must never have been previously used on other materials, especially not on carbon steel. Because the powder particles of carbon steel will be embedded in the surface of stainless steel, it is easy to cause corrosion. Ceramic balls can also be used as spray material.
12. Color stainless steel The stainless steel color process was successfully developed by the International Nickel Corporation (INCO) in the 1970s, and many companies have licenses to use this process. As explained earlier, the reason why stainless steel does not rust is because of the inert chromium oxide film on its surface. The color process is to use this layer of film to form a specified color. Since stainless steel takes advantage of this always-present film, it neither fades nor requires frequent maintenance like paint. Colored stainless steel can also be processed, even in sharp bends, it will not have any adverse effects on the color. Regarding the impact on corrosion resistance, the test shows that the corrosion resistance is enhanced after adopting this process. The process is closely related to the operation time, and the color will change with time. The order of color change is brown, gold, red, purple, and green. A special feature of this process is that its final appearance can reflect the original surface of the material, that is: a mirror or polished surface will produce a strong metallic luster, while the color of rough surface processing is matte. Process: This process is to immerse stainless steel in a solution tank. The solution preferably contains 250 grams of Cr2O3 per liter, and 490 grams of sulfuric acid per liter is also acceptable. The temperature range is 80~85 °C, and the soaking time depends on the required color. , no more than 25 minutes. After rinsing the steel plate with clean cold water, put it into a liquid with a concentration of 250 g/1 liter of chloric acid and 2.5 g/1 liter of phosphoric acid at room temperature for cathodic treatment. The time is about 10 minutes, and the current density is 0.2 ~0.4A/dm2. To prevent damage, harden immediately after coloring, rinse in hot water, and dry.
13. Mixed Surface Finishing Colored stainless steel can be patterned, the proprietary technology developed involves removing the “overhang” with a corundum abrasive belt, so that the result combines the natural beauty of the steel plate with the color of the colored pattern. This surface is not prone to fingerprints and is especially suitable for interior decoration. Polishing manufacturers can provide samples of surface processing.
14. Etching surface processing The pattern is marked on the surface of the steel plate through the coating process, and then the steel plate is immersed in ferric chloride acid solution (o grade) to etch away the uncoated part, forming a beautiful pattern on the surface of the stainless steel.
Post time: Jun-21-2023