Sheet Finishes

Stainless steel sheets are produced on continuous mills or hand mills. The steel is usually cast in ingot form and rolled on a slabbing or a blooming mill to slabs or sheet bars. Alternatively, the steel may be cast directly in slab form ready for finish hot rolling.

Sheets produced on continuous mills from slabs are rolled into coils and are further processed by annealing, descaling, and cold reducing to specified thickness, then further annealing and descaling. Coils or lengths cut from coils may then be subjected to light cold rolling for finish on dull or bright rolls.

Sheet finishes (Table 3) are designated by a system of numbers: No. 1, 2D, and 2B for rolled (unpolished) finishes; and No. 3, 4, 6, 7, and 8 for polished finishes.

Table 3 Standard mechanical sheet finishes

Finish

Description

Unpolished or rolled finishes

No. 1

A rough, dull surface that results from hot rolling to the specified thickness followed by annealing and descaling

No. 2D

A dull finish that results from cold rolling followed by annealing and descaling, and may perhaps get a final light roll pass through unpolished rolls. A 2D finish is used where appearance is of no concern.

No.

A bright, cold-rolled finish resulting in the same manner as No. 2D finish, except that the annealed and descaled sheet receives a

2B

final light roll pass through polished rolls. This is the general-purpose cold-rolled finish that can be used as is, or as a preliminary step to polishing.

Polished finishes

No. 3

An intermediate polished surface obtained by finishing with a 100-grit abrasive. Generally used where a semifinished polished surface is required. A No. 3 finish usually receives additional polishing during fabrication.

No. 4

A polished surface obtained by finishing with a 120 to 150-mesh abrasive, following initial grinding with coarser abrasives. This is a general-purpose bright finish with a visible "grain" that prevents mirror reflection.

No. 6

A dull satin finish having lower reflectivity than No. 4 finish. It is produced by tampico brushing the No. 4 finish in a medium of abrasive and oil. It is used for architectural applications and ornamentation where a high luster is undesirable, and to contrast with brighter finishes.

No. 7

A highly reflective finish that is obtained by buffing finely ground surfaces but not to the extent of completely removing the grit lines. It is used chiefly for architectural and ornamental purposes.

No. 8

The most reflective surface, which is obtained by polishing with successively finer abrasives and buffing extensively until all grit lines from preliminary grinding operations are removed. It is used for applications such as mirrors and reflectors.

Source: Ref 2

Source: Ref 2

No. 1 is a very dull finish produced by first hot rolling the steel on hand sheet mills to the specified thickness and then annealing and descaling. It is used in industrial applications for resistance to heat or corrosion, where a smooth finish is not of particular importance.

No. 2D is a dull finish produced on either hand sheet mills or continuous mills by cold rolling to the specified thickness, annealing, and descaling. The dull finish may result from the descaling operation or may be developed by a final light cold roll pass on dull rolls. This finish is favorable to the surface retention of lubricants in deep drawing operations. It generally is used in forming deep-drawn articles that may be polished after fabrication.

No. 2B is a bright, cold-rolled finish commonly produced in the same way as No. 2D, except that the annealed and descaled sheet receives a final light cold-roll pass on polished rolls. It is a general-purpose finish used for all but exceptionally difficult deep drawing applications. This finish is more readily polished than No. 1 or 2D.

No. 3 is an intermediate polished finish for use where a semifinished polished surface is required and a further finishing operation follows fabrication. For sheets or articles that will not be subject to additional finishing or polishing, No. 4 finish is recommended.

No. 4 is a general-purpose polished finish widely used for architectural panels and trim, and for dairy, restaurant, and kitchen equipment. Following initial grinding with coarser abrasives, sheets are finally finished with lubricated 120- to 150-mesh abrasive belts.

No. 6 is a dull satin finish having lower reflectivity than No. 4. It is produced by tampico brushing No. 4 finished sheets in a medium of abrasive and oil and is used for architectural applications and ornamentation where a high luster is undesirable. It also is used to contrast with brighter finishes.

No. 7 is a finish with a high degree of reflectivity, produced by buffing a finely ground surface without removing the grit lines. It is used chiefly for architectural and ornamental purposes.

No. 8 is the most reflective finish and is obtained by polishing with successively finer abrasives and buffing extensively with very fine buffing rouges. The surface is essentially free of grit lines from preliminary grinding operations. This finish is most widely used for press plates, as well as for small mirrors and reflectors. Sheets can be produced with one or both sides polished. When polished on one side only, the other side may be rough ground in order to obtain the necessary flatness. The relationship between abrasive grit numbers and surface roughness in terms of microinches is sometimes a basis for specification. The values are approximately as follows:

Abrasive grit no.

Surface roughness

fim

^in.

500

0.10 to 0.25

4 to 10

320

0.15 to 0.38

6 to 15

240

0.20 to 0.51

8 to 20

180

0.64 max

25 max

120

1.14 max

45 max

0 0

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