Quantitative evaluation of oxide impurities in bright annealed stainless steels for deep drawing

Abstract

Cold rolled SS is suitable for deep drawing operations, however the presence of resilient scales or oxides on the surface can damage the deep drawing punch/die sets and emphasise creep phenomena of the material. These oxides can be formed during the hot rolling process preceding the cold one, or during the bright annealing performed between the steps of thickness reduction of the coil. Then a cleaning of the SS surface before drawing is necessary to have a longer life of the tools. The removal of the surface oxide scale can be performed with electrolytic pickling using neutral electrolytes, but the process parameters can be varied depending on the amount of oxides present on the surface of the starting material. To optimise the process efficiency, then, an univocal scale of the degree of oxidation of the bright annealed SS was determined through microscopical analysis and potentiodynamic tests.