Over a three-month construction period, ThyssenKrupp VDM (Werdohl) modernized the batch-pickling unit at its Siegen site. Some 450 metric tons of soil have been excavated to make way for the new concrete backfill and the acid-resistant ceramic slabs which form the new foundations for the pickling unit at the Siegen plant. Pickling is an important step in the production of special stainless steels and nickel alloys. It removes the scale formed on the surface during hot rolling and heat treatment. The Siegen plant uses a pickling process with hydrofluoric or sulfuric acid to avoid the nitrogen oxides created when nitric acid is used. A further environmental aspect is the use of waste heat from the annealing furnace to heat the acid baths to the required temperature of 30 to 35C. This is done by plate heat exchangers set into the pickling unit. Plates measuring 2500 by 8000mm and weighing up to 2800kg can be pickled in the new unit.
