Q
Do you know the different types of surface of stainless steel?
A


 

A No. 1 finish has rough, dull, and non-uniform appearance. There may be shiny spots were surface imperfections were removed by grinding. It is generally used in industrial applications, such as equipment for elevated temperature service.

 


No. 2B Finish is a bright cold rolled finish commonly produced in the same manner as 

No. 2B is a general purpose cold rolled finish commonly used for all but exceptionally difficult deep drawing applications. It is more readily polished to high luster than a No. 1 or No. 2D finish.

 

No. 2D Finish is a uniform, dull silver gray finish that is applied to thinner coils whose thickness has been reduced by cold rolling. A No. 2D finish is preferred for deep drawing components because it retains lubricants well. It is used as a substrate when a painted finish is desired because it provides excellent paint adherence.

 

 

Bright Annealed (BA or 2BA) is produced by heat-treating (annealing) in a controlled atmosphere furnace. It has a mirror like appearance but may have some cloudiness and other imperfections. A finish that is designated “BA” has only been bright annealed. A finish that is designated “2BA” has been bright annealed and then passed between highly polished rolls. 

 

 

No. 3 Finish is characterized by short, relatively coarse, parallel polishing lines, which extend uniformly along the length of the coil.


 

No 4 Finish is characterized by short, parallel polishing lines, which extend uniformly along the length of the coil. It is obtained by mechanically polishing a No. 3 finish with gradually finer abrasives. Depending on the requirements of the application, the final finish can be anywhere between 120 and 320 grit. Higher grit numbers produce finer polishing lines and more reflective finishes. The surface roughness is typically Ra 25 micro-inches or less. This general-purpose finish is widely used for restaurant and kitchen equipment, storefronts and food processing and dairy equipment. If a fabricator needs to blend in welds or do other refinishing, the resulting polishing lines are usually longer than on product polished by a producer or toll-polishing house.

 

 

No 7 Finish has a high degree of reflectivity and a mirror-like appearance. A No. 4 finish that has been polished to 320-grit is buffed for up to 10 minutes but existing grit lines are not removed. The remnants of fine polishing lines can generally seen by an observer standing several feet from a panel.


 

No 8 Finish is the most reflective polished finish that is covered by the ASTM standards. It is produced in the same manner as the No. 7 finish except that the buffing is continued for an additional five to ten minutes. In comparison to a No. 7 finish, the grit lines are much less visible, but they can be seen if the finish is examined closely. The resulting finish is mirror-like but not a perfect mirror.

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