| 摘要 |
PURPOSE:To produce spring steel for cold forming having excellent corrosion resistance at a low cost by forming an iron-zinc alloy coated film on the surface of a spring steel base material by blasting, and forming a chromate film on the coated film. CONSTITUTION:Untreated strip spring steel A is introduced into a blasting device C, a blasting material consisting of an aggregate of independent particles obtained by coating a core of iron or an iron alloy with zinc or a zinc alloy through an iron-zinc alloy layer is projected from projecting rotors c1 and c2 to form a porous iron-zinc alloy coated film on the surface of the base material A. At this time, the particle diameter of the blasting material is controlled to <=about 1mu, and the amt. of the film to be deposited is adjusted to about 6-20g/m<2>. The steel is then introduced into a treating vessel (d) contg. an aq. chromating soln., and a chromated film is formed at about 60-300mg/m<2>. The steel is then appropriately passed through a dehydrating roll E and a drying blower F, and wound on a roll shaft (b). As a result, spring steel for cold forming exhibiting excellent corrosion resistance over a long period is obtained. |
