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Abstract

Methods for annealing and pickling high manganese cold rolled steel sheets for use in automobiles and electronic panels in which a superior formability and high strengths are required are disclosed. That is, the invention provides a method for annealing a cold rolled high manganese steel sheet, in which, after cold-rolling a high manganese steel of Fe--Mn--Al--C series, the annealing atmospheric gas is adjusted during an annealing so as to minimize the thickness of a surface oxide layer, and an oxide layer removing agent such as aluminum nitride is spread into the oxide layer, so that the surface oxide layer can be easily removed. The invention further provides a method for pickling a cold rolled high manganese steel sheet, in which the surface oxide layer formed on the cold rolled high manganese steel sheet is uniformly removed with a mild aqueous solution of chloric acid, thereby improving the surface quality of the steel sheet, and saving the pickling facility cost. When the high manganese steel sheet is annealing at a temperature of 500.degree.-1000.degree. C., the annealing atmosphere consists of 100% of nitrogen or 50% or more of nitrogen and a balance of hydrogen. The high manganese steel sheet is pickled for 30-90 seconds within an aqueous solution of chloric acid having an acid concentration of 0.06-0.8 weight % and a temperature of 15.degree.-50.degree. C.

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First Claim