SURFACE-TREATED STEEL TUBE FOR HYDROFORMING HAVING EXCELLENT COATABILITY

摘要

PROBLEM TO BE SOLVED: To provide a surface-treated steel tube for hydroforming which prevents seizure during the hydroforming, reduces friction, and is free from any problem of coatability after the hydroforming. SOLUTION: In the surface-treated steel tube for hydroforming of excellent coating suitability, a phosphate zinc film of the P-ratio äphosphophyllite / (phosphophyllite + hopeite)} of≥0.3 to < 0.6 is formed on an outer surface of a pickled steel tube, and lubricating oil with rust-preventive performance is applied thereto. Grain size of the phosphate zinc film is preferably 5-20μm, and the film deposition is preferably in the range of 2 g/m2to 5 g/m2. COPYRIGHT: (C)2005,JPO&NCIPI