InnoZun – Improvement of the surface quality of stainless steel strip by secondary scale conditioning and innovative descaling processes

Situation:

In hot processing of steel, reactions of the metal surface with ambient air result in the formation of complex scale and oxide layers with a thickness of up to 10 µm on stainless steels. These scale layers must be removed before further processing in order to achieve good surface quality and re-establish the corrosion protection properties of the stainless steel.

Approach:

– Optimisation of the descaling process chain of stainless steels

– Enabling the use of more environmentally friendly and resource-saving pickling solutions by combining new descaling processes with innovative additives to reduce scale adhesion

– Improvement of surface quality by reduction of mechanical surface stress

Results:

It was shown that the scale adhesion on the stainless steels can be reduced by additives selected according to the steel quality and thus surface-protecting cleaning by the use of alternative blasting agents is possible. Here, too, the selection of the blasting method must be adapted to the type of scale. The complete removal of the chromium depleted metal layer by means of alternative pickling solutions and thus the reduction or substitution of conventional, aggressive and environmentally damaging chemical pickling processes could not be achieved within the scope of this project.

Note on funding:

The IGF Project No. 18731 N of the Forschungsvereinigung VDEh-Gesellschaft zur Förderung der Eisenforschung mbH, Sohnstraße 65, 40237 Düsseldorf was funded by the AIF within the framework of the programme for the promotion of joint industrial research IGF, of the Federal Ministry of Economics and Energy on the basis of the resolution of the German Bundestag. We would like to take this opportunity to express our sincere thanks.

The final report is available at the German National Library of Science and Technology (TIB) Hannover.

• scale conditioning additives; surface quality of stainless steel strip; alternative blasting methods; innovative pickling processes; process chain optimization