2B, 2D and BA Cold Rolled Finishes
What are Cold Rolled Finishes?
Cold rolled finishes apply to flat products such as stainless sheet or stainless steel coil, with thickness less than about 5mm and usually less than 3mm. They are firstly hot rolled into a strip (or cast into a slab which is hot rolled into a strip) and then cold rolled. Cold rolling reduces the thickness by at least 50%. This smooths the surface, refines the grain structure and causes differences in the mechanical properties along and across the rolling direction. In the case of austenitic and duplex alloys, the process hardens and strengthens the stainless steel. Finally, the steel is softened by annealing in a furnace? Each surface finish may undergo additional processes to improve the surface further. The smoother the surface finish is, the higher resistance to corrosion it will be.
2B
2B is the most widely used stainless steel surface finish. It is especially common in industrial, chemical and food processing applications such as process vessels and tanks. It is also used in some architectural applications that will not be closely examined for uniformity of finish such as downpipes and gutters.
When specifying this finish think about these attributes:
2B is the most economical finish
It is highly corrosion resistant because it has been chemically pickled and is smooth
Over broad areas and between batches etc., it is not uniform and may not match in appearance
It has been produced in the mill and can't be matched after fabrication
It if often protected by plastic films until final cleanup and commissioning
2D
2D is used around the world in applications where its low reflectivity is important. The largest application is in roofing materials. The surface is rougher than 2B and retains lubricants better making it appealing for deep drawring. 2D surfaces are not designed for appearance so the limitations on matching of weld and other surface damage is not as critical. Railcars are a typical example where thicker sheet and ongoing abrasive damage make the rougher 2D a suitable finish.
When specifying this finish think about these attributes:
2D is not commonly available in Australia
It is highly corrosion resistant because it has been chemically pickled and is relatively smooth
Over broad areas and between batches etc., it is not uniform and may not match
It has been produced in the mill and can't be matched after fabrication
Bright Annealed (BA)
The classic use of a BA finish is domestic: the interior of a dishwasher or clothes washing machine. In the clothes washer, it also provides a smooth, non-abrasive surface for the clothes to slide around. The mirror like surface is also used in road mirrors where a precise image is not required.
When specifying this finish think about these attributes:
BA is common in some grades and thicknesses, but not all
It is highly corrosion resistant because it is very smooth
Different batches may not match
It is has been produced in the mill and can't be exactly matched after fabrication although a mechanical mirror polish can be close.
Post Production Processing to Improve Corrosion Resistance
All the cold rolled processes include a pickling stage. Pickling is the removal of high temperature scale and the adjacent low chromium layer of metal from the surface of stainless steel by chemical means. Pickling will also remove manganese sulphide inclusions and any other contamination on the surface. Pickling results in a very clean, highly corrosion resistant surface, but will slightly roughen the surface.
GNEE Steel has been committed to stainless steel products for many years and is an expert in the field of stainless steel, providing various grades of stainless steel products, including stainless steel seamless pipes, stainless steel welded pipes, stainless steel plates, stainless steel coils, stainless steel pipe fittings, etc. If you need stainless steel, please contact us.ss@gneesteel.com
