Standards of Surface Processing
Many surface processing technologies, classified by numbering or other methodologies, have been incorporated into relevant standards, such as the American Standard ASTM A484, the British Standard BS1449 and the European Standard EN10221.
Rolling surface processing
Basically, there are three rolling finishes for sheets and strips, expressed by their production processes.
No.1 Finish
Finish: The finishes of the treated sheets are dull and somewhat rough.
Production Process: The sheets are hot rolled, annealed, pickled, and descaled.
No.2D Finish
Finish: No.2D is better than N0.1 finish, but it also presents a dull surface.
Production Process: The sheets and strips are subjected to cold rolling, annealing, descaling, and finally light rolling with a matte roller.
No.2B Finish
Finish: The surface is slightly illuminated and allows for polishing treatment.
Production Process: It is the most commonly used for architectural applications. The production process is similar to 2D finish; only No. 2B entails light cold rolling with a polishing roller after annealing and descaling for its last process.
No. 2B Bright Annealing Finish
Finish: This is a reflective surface. Bright annealing still maintains its reflective surface and does not produce oxide skin.
Production Process: The sheet is rolled by a polishing roll and subjected to final annealing in a controlled atmosphere. Since the oxidation reaction does not occur during the bright annealing process, it eliminates the necessity to perform pickling and passivation treatment.
Polished surface processing
No. 3 Finish
No.3 is represented by 3A and 3B.
3A finish is uniformly ground with the abrasive grain size at 80 to 100.
3B Finish
Finish: The mill finish is polished, with uniform straight lines on the surface.
Production Process: Usually, it is polished on the 2A or 2B sheet by the abrasive belt with grain size at 180-200 to get 3B finish.
No.4 Finish
Finish: No.4 or 4K finish is unidirectional and of low reflectivity, with the widest use for architectural applications.
Production Process: The sheets are first polished with coarse abrasive and finally with abrasive grain size at 180.
No.6 Finish
Finish: No.6 Finish is a further improvement of No. 4, which is polished with a Tampico polishing brush in abrasive and oil media. No.4 finish is not available in British Standard 1449 but can be found in the US standard.
No.7 Finish
Finish: No.7 is known as bright polishing on the surface that has been ground very fine but still has scratch marks.
Production Process: 2A or 2B plates are commonly used, with fiber or cloth polishing wheels and corresponding polishing pastes.
No.8 Finish
Finish: No.8, or 8K finish is often referred as mirror finish, because the image it reflects is sharp.
Production Process: The stainless steel is usually polished continuously with fine abrasives and then polished with polishing pastes. Care should be taken when it is designed for architectural applications. Such stainless steel with 8K finish, if used in places where people are heavily mobile or where people often touch them, can be left handprints. Though the fingerprints can be erased easily, but sometimes it affects the appearance.
Note
The surface processing described in official standards and literature is quite general; only the sample can best show the type of surface processing. Polishing or metal finishing mills can provide samples of a variety of finishes for straightforward communications with their users.
Surface roughness
The classification of rolling surface processing and polishing surface processing is to illustrate the extent to which a surface can be processed; another effective method is to measure surface roughness. The standard measurement method is called CLA (center line average). Move the gauge laterally on the surface of the steel sheet to record the change in the peaks and valleys. The smaller the CLA number, the smoother the surface.
Contact
CIVMATS Co., Ltd. produces high-value stainless steel raw materials. If you want to know more about stainless steel, please keep following us. Any requirements or questions about stainless steel, call CIVMATS!
- Company: CIVMATS CO., LIMITED
- Phone: 86-519-81809659
- Fax: 86-519-81809959
- Email: [email protected]
- Address: 10th Floor, Xin Cheng Nan Du, Wujin District, Jiangsu, China
- Website: www.civmats.com
