Grinding of stainless steel
Stainless steels can be used diversely due to its favourable properties, like corrosion resistance. Of course, the basic requirement for a satisfactory result is the right selection of the material to be used for the intended application. Also the correct surface finish maintains thefavourlable properties.
For this reason, and also for optical aspects many componants of stainless steel are ground at the end of the working process. With regard to the corrosion resistance the finer the surface the higher the resistance against corrosion.
What preconditions have to be fulfilled and what has to be observed during grinding in order to achieve a satisfactory final result?
The surface finish made in the factory, i.e. the rolled, pickled and/or once more heat treated material should be selected so that the original surface corresponds to the surface desired later as close as possible.
For the corrosion resistance it has to be observed in advance that the material is stored and transported properly. That means primarily:
- Avoid any contact with other steels (steel brushes, wire ropes). (cross contamination) This also includes the separate storing of rolled steel.
- Avoid damages to the surface and edges, as well as abrasion.
- Do not store the material in working areas.
There is a multitude of parameters which has an effect on the roughness and the appearance of the processed surface:
- The grinding machine with the corresponding contact elements and working parameters (cutting speeds and feed rates)
- The application of auxiliary supplies (oils and emulsions)
- The quality of the abrasive
Due to these boundary conditions preset by the grinding process no general statement can be made on the interrelation between surface finish achieved and abrasive used. In order to avoid misunderstandings when stipulating the requested surfaces reference samples and roughness values (Ra) should be fixed in advance of working.
Grinding and Corrosion
Irrespective of the stainless steel used, and thus the resistance of the workpiece, the measures listed in the following should be observed implicitly during grinding of noncorrosive steel:
- Do not use grinding tools on standard steel and subsequently on stainless steel!
- Always remove abrasive dust from all surfaces thoroughly!
- Never alow the stainless steel surfaces to come into contact with glowing fountains of sparks!
- The working temperatures have to be so low that no chromium carbides and thus intercrystalline corrosion is formed. If the material blues reworking is absolutely necessary!
Only this ensures that the passive layer in the sectors worked develops newly and the other surfaces are not damaged through pitting corrosion or intercrystalline corrosion (see also ’Can noncorrosive steel rust?’).