| 摘要 |
PROBLEM TO BE SOLVED: To unnecessitate a surface belt-grinding process in a mechanical pre- descaling treatment by hot-rolling a steel sheet, applying the mechanical pre- descaling treatment, at a specified temp. pickling in mixed aqueous solution containing specified concns. of nitric acid and hydrofluoric acid, and executing cold-rolling, finish-annealing, pickling and temper-rolling. SOLUTION: After annealing the steel sheet at 800-1050 deg.C, the mechanical pre-descaling treatment is applied and the pickling is executed in the mixed aqueous solution containing 20-100 g/l of nitric acid and 50-200 g/l of hydrofluoric acid. It is desirable to execute the annealing at 900-1010 deg.C and the pickling in the mixed aqueous solution containing 30-90 g/l of nitric acid and 100-150 g/l of hydrofluoric acid and 50-90 deg. pickling temp. The mechanical pre-descaling treatment may use with a single or a combination among the general methods of shot blast, bender, leveler, etc. The hot-rolled sheet is cold-rolled without executing the surface belt-grinding. Thereafter, the finish-annealing and the pickling to the cold-rolled sheet are executed and successively the temper-rolling e.g. at 1% draft is executed.
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