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.

Effect of Cold Working and Annealing Condition on Scale Formation of AISI 4140 Steel

“…Thus, scale can affect the workpiece by creep phenomena and damage and extensive wear of tool that affects the surface quality of products. [1][2]. Furthermore, alloying element in metal can be effect on the oxidation surface.…”

“…[3] The removal of the scale can be performed by pickling using neutral electrolytes such as neutral sodium sulphate solution (Na 2 SO 4 ) or sulfuric acid solution (H 2 SO 4 ) with electrochemical process. [1], [4] The previous study was showed that the scale formed on some steel such as stainless steel, the condition of moist air was the most difficult to remove, while annealing in a reducing atmosphere was easy descaling. [4].…”