COMPANYVALUES AND SERVICESPRODUCTS
LONG
FLAT
STRUCTURAL
TIGBRUSHNEWSCONTACT
LEGAL NOTE
PRIVACY POLICY
ES EN CAT FR

Articles - Roughness in stainless steels and its measurement

Roughness is one of stainless steel's technical values frequently evaluated or even set by the customer, it is therefore required to have a certain level of knowledge about it; in this article you will be able to find the main key points both about roughness as well as its measurement.

Roughness is a measurement unit defining how rough the texture of a given surface is. Its obtention is according to the vertical deviations from the ideal form of this given surface. According to it we can thus find many different kinds of surfaces, from roughest to smoothest ones.

Its measurement is done with a stylus which travels across the surface of the material, being all the values obtained fully registered. The final result is expressed as Ra or average roughness, being just the arithmetic average value of the deviation of those values from the centre line. Ra is usually measured in micrometres.

To know if a certain surface is suitable for a given application most of the times we need to know both amplitude as well as frequency of the roughness. Amplitude would be the real deviation form the central line at a given point whilst frequency being the periodicity at which the surface shows these deviations.

Ra is a very practical and useful average. However, it is not exempt of limitations, which we need to bear in mind. The most relevant one without any doubt is not differentiating between peaks and valleys. This results in materials with same Ra value having very different profiles one from the other.

When customer sets the Ra requested, we need to have very clear if they are speaking about Ra as the upper limit or as the maximum value. In the first case a value is defined (Ra ?0.6 µm as a random example), and according to it material will be acceptable as long as values over the one defined do not exceed 16% of all those ones registered for a defined length. On the other hand, when it is set as the Ra max (being the expression "max" mentioned next to the value) none of the measurements recorded can be over this given one. On regular basis only higher values are considered, being therefore not that common that minimum values are defined. There are nevertheless some exceptions.

As an alternative way to measure roughness we find Rz too, defining max height of the deviation. Rq also exists, defining the root-mean-square deviation of a profile.


It is worth pointing out that roughness is quite linked to the finish the material has. Equally, it changes if we apply polishing finishes or any other mechanical processing, even resulting in irreversible damage if not applied properly.

We present next the common roughness values for the main finishes of the flat products of our partner JSL Stainless:

1. No.1 finish (hot rolled): 6µm max.

2. 2B/2D finish (cold rolled mat): around 0.3µm

3. No.3 finish (coarse abrasive finish applied mechanically): around 1.0µm

4. No.4 finish (grinded, depending on grain): around 0.6µm



For more information, you can fill in our form. If you prefer, you can contact directly with one of our sales agents. We are here to help you!

Most read

Buses. Vision and experience

Today we bring you this interesting article publis

+ INFO

Kinds of corrosion in stainless steel: crevice corrosion

In this article crevice corrosion in stainless ste

+ INFO

Roughness in stainless steels and its measurement

Roughness is one of stainless steel's technical va

+ INFO

Search by category

+ ARTÍCULOS DIVULGATIVOS+ NOTICIAS DEL SECTOR+ LOS TIPOS DE CORROSIÓN EN ACEROS INOXIDABLES+ NOVEDADES