Metal surface processing is of great significance to metals. A variety of surface processing technologies broaden the application fields of metals. Different surface treatments give different surfaces to metal workpieces, making them unique in their applications. In addition to several traditional surface processing methods, Jinan Weir's metal surface processing equipment using Haokeneng technology can process various technical parts. It can achieve a metal mirror effect in one treatment, and the surface finish can be improved by more than 3 levels. The surface roughness value is below Ra0.1 and can reach as low as Ra0.0125.
The surface microhardness is increased by 20~50. The surface fatigue resistance is improved by more than 200.
There are many reasons why stainless steel surface processing is important in construction applications. Corrosive environments require smooth surfaces because smooth surfaces are not prone to fouling. The accumulation of dirt can cause stainless steel to rust and even cause corrosion. In spacious halls, stainless steel is the most commonly used material for elevator decorative panels. Although fingerprints on the surface can be wiped off, they affect the appearance, so it is best to choose a suitable surface to prevent fingerprints from leaving. Hygienic conditions are important in many industries, such as food processing, catering, brewing and chemical industries. In these applications, surfaces must be easy to clean every day, and chemical cleaning agents are often used. Stainless steel is the best material in this regard. In public places, the surface of stainless steel is often scrawled with graffiti. However, one of its important features is that they can be washed away. This is a significant advantage of stainless steel over aluminum. Features. The surface of aluminum tends to leave marks, which are often difficult to remove. When cleaning the surface of stainless steel, you should clean it along the lines of the stainless steel, because some surface processing lines are one-way. Stainless steel is most suitable for use in hospitals or other areas where hygiene is critical, such as food processing, catering, brewing and chemical industries, not only because it is easy to clean every day, sometimes using chemical cleaning agents, but also because it is less likely to breed bacteria . Tests have shown that stainless steel performs the same as glass and ceramics in this regard.
1. The natural appearance of stainless steel
Stainless steel gives people a natural strong and bright feeling, and its natural color softly reflects the color of the surrounding environment.
2. Basic types of metal surface processing
There are roughly five types of surface processing that can be used for stainless steel, and they can be combined to transform more final products.
The five categories are: rolling surface processing, mechanical surface processing, chemical surface processing, textured surface processing and colored surface processing.
There are also some special surface processing, but no matter which surface processing is specified, the following steps should be followed:
① Agree with the manufacturer on the required surface processing, preferably Prepare a sample as a standard for future mass production.
②When used in large areas (such as composite panels, it must be ensured that the base coils or coils used are from the same batch.
③In many construction applications, such as: Although fingerprints can be wiped off inside the elevator, they are not very noticeable if a cloth-textured surface is used.
Mirror stainless steel must not be used in these sensitive areas.
④The production process should be taken into consideration when selecting surface processing. For example, in order to remove the weld beads, the weld may need to be ground, and the original surface processing must be restored.
It is difficult or even difficult to obtain a patterned plate. This requirement cannot be met.
⑤ For some surface processing, grinding or polishing, the texture is directional, which is called unidirectional. If the texture is used vertically instead of horizontally, Dirt is not easy to adhere to it, and it is easy to clean.
⑥ No matter which finishing method is used, additional process steps are required, so the cost will be increased, so be careful when choosing surface processing.
Therefore, relevant personnel such as architects, designers and manufacturers need to have an understanding of stainless steel surface processing, and the desired results will be achieved through friendly cooperation and mutual communication.
⑦Based on our experience, we do not recommend using aluminum oxide as abrasives unless great care is taken during use.
It is best to use silicon carbide abrasives.
3. Standard surface processing
Many types of surface processing have always 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 Council Standard.”
4. Rolling surface processing
There are three basic rolling surface processings for plates and strips, which are represented by the production processes of plates and strips. No.1: Hot rolled, annealed, pickled and descaled. The surface of the treated steel plate is a dull surface and a bit rough.
No.2D: Better surface processing than N0.1, but also a dull surface. After cold rolling, annealing, descaling, and finally light rolling with matte rollers.
No.2B: This is the most commonly used in construction applications. Except for the last light cold rolling with a polishing roller after annealing and descaling, the other processes are the same as 2D. The surface is slightly shiny. Can be polished.
No.2B Bright Annealing: This is a reflective surface that is rolled with polishing rollers 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 bright annealing, pickling and passivation treatments are not required.
5. Polished surface processing
No.3: Represented by 3A and 3B. "3A: The surface is evenly ground, and the abrasive grain size is 80 to 100.
3B: The matte side is polished, and the surface has uniform straight lines. Usually, an abrasive belt with a grain size of 180 to 200 is used in 2A or The 2B board is polished in one step.
No.4: One-way surface processing, not very reflective. This kind of surface processing may be the most widely used in construction applications. The process step is to roughen it first. Abrasive polishing, and finally grinding with an abrasive of 180 grit.
No.6: It is a further improvement on No.4. It is polished with a Tampico polishing brush in abrasive and oil media. Surface. There is no such surface treatment in "British Standard 1449", but it can be found in the American standard.
No.7: It is called bright polishing, which is polished very finely but still polished. The surface with marks is usually used to polish the 2A or 2B plate, with a fiber or cloth polishing wheel and the corresponding polishing paste.
No.8: Mirror polished surface, with high reflectivity, often called The mirror surface is processed because the reflected image is very clear. Polish the stainless steel continuously with a fine abrasive and then polish it with a very fine polishing paste.
Care should be taken if this surface is used in architectural applications. Fingerprints can certainly be wiped off in areas with high traffic or where people touch them frequently, but sometimes the surface finish described in "official" standards and literature is general. The type of surface processing can be most intuitively represented by the introduction. Polishing or metal finishing manufacturers will provide samples of various surface processing, and users should discuss with them.
6.
Surface roughness
The classification of rolled surface processing and polished surface processing indicates the degree to which it can be achieved. Another effective way to express it is to measure surface roughness. The standard measurement method is called CLA ( center line average), the measuring instrument moves laterally on the steel plate surface and records the variation of the peaks and valleys. The smaller the CLA number, the smoother the surface. The final results of different grades can be seen from the surface processing and CLA numbers in the table below. . Surface processing
CLA, micron 2B 0.1-0.5 2A 0.05-0.1 2D 0.4-1.0 3 0.4-1.5 4 0.2-1.5 8 0.2 EP 1/2 of the basic value
EP =Electrolytic polishing can roughly reduce the peak and valley changes to 1/2 of the original surface.
7. Precautions for mechanical polishing:
We should remember that during the grinding operation. Grinding with sandpaper or abrasive belts is essentially a polishing cutting operation, leaving very fine lines on the surface of the steel plate.
We have had trouble using aluminum oxide as an abrasive, partly due to pressure issues.
Any grinding parts of the equipment, such as abrasive belts and grinding wheels, must not be used on other non-stainless steel materials before use. Because this will contaminate the stainless steel surface.
In order to ensure the consistency of surface processing, the new grinding wheel or belt should be tried on scrap materials with the same composition first, so that the same samples can be compared.
8. Electropolishing
This is a metal removal process in which stainless steel acts as an anode in the electrolyte, and the metal is removed from the surface after electricity is applied. The process is often used for parts whose shapes are difficult to polish using traditional methods.
This process is often used on the surface of cold-rolled steel plates because its surface is smoother than that of hot-rolled steel plates. However, electrolytic polishing will make surface impurities more obvious, especially titanium and niobium-stabilized materials, which will cause differences in the weld area 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, dissolving them preferentially.
The electrolytic polishing process is to immerse stainless steel in heated liquid. The proportion of the liquid involves many proprietary technologies and patented technologies.
Electrolytic polishing of austenitic stainless steel works very well.
9. Textured surface processing There are many types of patterns that can be used for stainless steel.
The advantages of adding patterns or textured surface processing to steel plates are as follows: ① Reduce "metal roofing material shrinkage" (oil
can-ning), which is a term used A term describing the surface of a shiny material that does not appear to be flat from an optical perspective. For example: even if a large-area decorative board is stretched or straightened by tension, it is difficult to make the surface completely flat, so the metal roof material will shrink.
②The mesh pattern can reduce glare in the sun. ③ If there are slight scratches and small-area indentations on the pattern plate, they will not be obvious. ④ Increase the strength of the steel plate. ⑤ Provides architects with a choice.
Patented patterns include cloth (used in the Ede Building in London), inlay, pearlescent and leather. Ripple and linear patterns are also available.
Patterned surfaces are particularly suitable for interior decoration such as elevator paneling, counters, wall panels and entrances.
When applying externally, consideration should be given to ensuring that the surface of stainless steel can be cleaned by rainwater and manual scouring, and to avoid dead corners where dirt and airborne impurities can easily accumulate, so as not to cause corrosion and affect the appearance.
10. Matte surface processing
Matte surface processing is one of the most commonly used surface processing. It is to use a nylon abrasive belt or brush on the surface of a polished or bright annealed steel plate. Perform polishing.
11.
Glass ball spraying or shot blasting For interior applications, such as the interior of elevators, hybrid surface treatments 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 mixed surface of polished and matte. Stainless steel sand balls can also be used in similar processes.
The glass balls or pellets to be used must not be used on other materials in advance, especially carbon steel. Because carbon steel particles will embed into the surface of stainless steel, it can easily cause corrosion.
Ceramic balls can also be used as spray materials.
12. Colored stainless steel
The stainless steel color process was successfully developed by International Nickel Company (INCO) in the 1970s, and many companies have licenses to use this process. As explained before, the reason why stainless steel does not rust is because of the chromium oxide film on its surface.
The color process uses this film to form the specified color. Because stainless steel utilizes this ever-present film, it neither fades nor requires the same regular maintenance as paint.
Colored stainless steel can also be shaped, even in sharp bends without any adverse effect on the color. Regarding the impact on corrosion resistance, tests show that corrosion resistance is enhanced after using this process.
This process is closely related to the operation time, and the color will change at different times. The order of color variation is brown, gold, red, purple and green.
A major feature of this process is that its final appearance can reflect the original surface of the material, that is: the mirror or polished surface will produce a strong metallic luster, while the color of the matte surface is matte. of. Process:
This process is to soak stainless steel in a solution tank. The solution should preferably contain 250 grams of Cr2O3 per liter, or 490 grams of sulfuric acid per liter. The temperature range is 80 to 85°C. The time depends on the color required and should not exceed 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 for about 10 minutes. , the current density is 0.2~0.4A/dm2.
To prevent damage, harden immediately after coloring, rinse in hot water and dry.
13. Hybrid Surface Finishing
Patterns can be added to colored stainless steel. The proprietary technique developed involves using a corundum abrasive belt to remove the "protruding" parts, so that the final result is Combining the natural beauty of the steel plate with the color of the colorful pattern.
This kind of surface is not easy to leave fingerprints and is especially suitable for interior decoration. Polishing manufacturers can provide surface processing samples.
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), and the uncoated parts are Parts of the film etch away, forming beautiful patterns on the surface of the stainless steel.