NEUTRALIZING TREATMENT OF STAINLESS STEEL

摘要

PURPOSE:To effectively utilize a waste hydrofluoric nitric acid solution produced at the time when hydrofluoric nitric acid is used for the pickling of a stainless steel and is recovered by using it for neutralization of a salt-treated stainless steel. CONSTITUTION:Stainless steel (wire rod) 13 is pickled by hydrofluoric nitric acid solution 1 contained in pickling treatment tank 2 and this hydrofluoric nitric acid solution 1 lowered in concn. is sent into an acid recovery device 3 via a pipeline 4. Water is sent into the acid recovery device 3 through a pipeline 5 and acid recovering treatment is performed. The recovered solution is returned to the pickling treatment tank 2 via a pipeline 6 and also waste hydrofluoric nitric acid solution 9 is stored in a neutralizing treatment tank 8. In the other hand, the stainless steel (wire rod) 13 subjected to salting treatment by salt (salt bath) 11 in a salt treatment vessel 12 is quenched by cooling liquid 14 in a quenching vessel 15 and thereafter transferred to a neutralizing treatment vessel 8 to perform neutralizing treatment and furthermore transferred to the pickling treatment tank 2 to perform pickling treatment. Thereby waste hydrofluoric nitric acid solution 9 which is conventionally discarded is effectively utilized.