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the surface of stainless steel is actually and extremely thin but stable and passive chromium rich oxide film, on which stainless steel relies for its excellent corrosion resistance. the surface finish on stainless steel should therefore be developed and maintained to ensure this vital property, and also for the secondary reason of the pleasing aesthetic appearance of stainless steel.
standard mill finished - flat rolled products
the standard mill surface finished are laid down in specifications (bs 1449, part 4, and the committee of stainless steel producers, american iron & steel institute).
the finished are designated by a system of numbers, and these are broadly described hereunder relative to the finishing operations employed. it should be remembered that different grades of stainless steel can result in a variation of visual appearance for the same finishing operation. the thickness can also have an effect, generally the thinner the material the smoother the surface finish.
the thicker gauge sizes of stainless steel are hot rolled. this is done at high temperatures and will always result in a scaled surface.
stainless steel flat product is supplied in the annealed ie fully softened condition.
this is also a high temperature operation and unless carried out in a very closely controlled inert atmosphere, will result in oxidation (scaling) of the surface.
surface | characteristic | summary of manufacturing method | application |
no.1 | silvery white | hot rolled to specified thickness | do not need to have a glossy surface use |
lackluster | |||
no.2d | silvery white | after cold rolling, heat treatment and pickling are carried out | general material, deep material |
no.2b | gloss is stronger than no.2d | after no.2d treatment, the final light cold rolling is carried out through the polishing roller | the general material |
ba | as bright as a sixpence | no standard, but usually a bright annealed surface with high reflectivity. | building materials, kitchen utensils |
no.3 | rough lapping | grind with 100~200# (unit) strop tape | building materials, kitchen utensils |
no.4 | intermediate grinding | polished surface obtained by grinding with 150~180# strop abrasive tape | building materials, kitchen utensils |
no.240 | fine lapping | grinding with 240# strop abrasive tape | kitchenware |
no.320 | very fine grinding | grinding was carried out with 320# strop abrasive tape | kitchenware |
no.400 | the luster is close to ba | use 400# polishing wheel to grind | general timber, building timber, kitchen appliances |
hl | hairline grinding | suitable particle material for hair stripe grinding (150~240#) with many grains | building, construction material |
no.7 | it's close to mirror grinding | use a 600# rotary polishing wheel to grind | for art or decoration |
no.8 | mirror ultrafinish | the mirror is ground with a polishing wheel | reflector, for decoration |
