Data Analysis: Surface Roughness of Mirror Stainless Steel

The term “mirror stainless steel plate” refers to the surface finish of the steel, but it also has different grades. This grade refers to the roughness of the stainless steel surface, and different grades correspond to different surface finishes. For example, 8k and 12k mirror stainless steel have different surface effects, but this differentiation is not precise enough.

The use of a “K number” to distinguish the surface effect of stainless steel is a general concept and can be difficult to differentiate without a comparison.

We have created a list to help identify different grades of stainless steel.

Surface gradeSurface roughnessSurface effect
Stainless steel surface finish Grade 14Ra 0.012~0.03μm 14k mirror stainless steel with excellent surface effect (ultra-fine polished stainless steel)
Stainless steel surface finish Grade 13Ra 0.015~0.02μm12k mirror stainless steel with excellent surface effect (ultra-precision polished stainless steel)
Stainless steel surface finish Grade 12Ra 0.02~0.16μm10k mirror stainless steel with excellent surface effect (fine polished stainless steel)
Stainless steel surface finish Grade 11Ra 0.1 ~0.2μm8k mirror stainless steel with good surface effect (fine polished stainless steel)
Stainless steel surface finish Grade 10Ra 0.2 ~0.3μm6k mirror stainless steel, BA stainless steel, original state of steel factory shipment
Stainless steel surface finish Grade 9Ra 0.4 μmThere is almost no brightness at 4k, also known as no brightness at 2B (fog)
Stainless steel surface finish Grade 8Ra 0.8 μm No mirror effect, can slightly identify the processing trace, and the unpolished surface
Stainless steel surface finish Grade 7Ra 1.6 μmNo mirror effect, able to identify the direction of processing traces, unpolished surface
Stainless steel surface finish Grade 6Ra 3.2 μmNo mirror effect, no visible processing trace, unpolished surface
Stainless steel surface finish Grade 5Ra 6.3 μmNo mirror effect, slight machining trace, unpolished surface
Stainless steel surface finish Grade 4Ra 12.5 μmNo mirror effect, visible processing trace, unpolished surface
Stainless steel surface finish Grade 3Ra 25 μmThere is no mirror effect, the surface is very rough, there are very obvious machining marks, and the surface is unpolished

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