Dalnox Bright New annealing & pickling process technology for cold rolled stainless steel strip

摘要

Cold rolled stainless steel strips are supplied with two surface finishes (according to EN10088/2): > 2D/2B - cold rolled, annealed, pickled and skin passed (2B); > 2R - cold rolled, bright annealed (BA) and skin passed. 2D/B finish is produced on high-capacity (up to 150 tph) continuous annealing and pickling line (A&PL), in which the strip is annealed in an oxidizing atmosphere (combustion gas mixture). The oxide layer produced during annealing has to be removed and passivity has to be restored. This is obtained by an electrolytic descaling process followed by a chemical pickling that produces a large amount of pollutants that require treatment processes. 2R finish is produced on bright annealing vertical plant in which the strip is annealed in a H2/N2 gas mixture, able to avoid surface oxidation, consequently pickling processes are not required. The vertical furnace reduces productivity to a maximum of 20-25 tph.