| 摘要 |
PROBLEM TO BE SOLVED: To provide a steel material without needs for a resin layer, excellent in corrosion resistance of a weld part and corrosion resistance in acidic soil environment.SOLUTION: A steel material has a scale formed on a surface, and a predetermined chemical composition, and the scale is a structure where magnetite, fayalite, wustite and hematite are laminated or partially mixed or the like with thickness of the scale of 5 to 50 μm and satisfies a relationship of the following formula. 0.15<(Mm+Mf)/(Mw+Mh)<0.35, 9.0<([Cr]+[Sn])/[Si]<23.0, where magnetite content is Mn, fayalite content is Mf, wustite content is Mw and hematite content is Mh in the scale, and Cr content is [Cr], Sn content is [Sn] and Si content is [Si] of the scale.SELECTED DRAWING: None |
