| 摘要 |
PURPOSE:To obtain a pickled and hot rolled steel sheet having good resistance to die galling by pickling the hot rolled steel sheet by using an aq. soln. contg. a specific compsn. amt. of hydrochloric acid and oxidizing agent. CONSTITUTION:A hot rolled steel sheet is pickled to prevent die galling by using an aq. soln. contg. 10-15wt% hydrochloric acid and 5-10% oxidizing agent so as to contain <=20% total acid and consisting of the balance water and inevitable impurities as a pickling soln. in the stage of pickling the hot rolled steel. The longer treating time for pickling and weaker effect of descaling are resulted if said hydrochloric acid concn. is <10% and there is no room for adding the oxidizing agent if the concn. exceeds 15%. Sulfuric acid, nitric acid, hydrogen peroxide, potassium dichromate, perchloric acid, hydrofluoric acid, etc. which dissolve by reacting with scale are suitable for the above-mentioned oxidizing agent. The melting of the ferrite after descaling is accelerated and pitting arises if the amt. thereof exceeds 10% and the lower remaining effect of carbon and the easy tendency to galling results at <5%. The pickling time is longer and the pickling is disadvantageous if the total of the acids exceed 20%.
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