| 摘要 |
A curved metallic material is produced by subjecting a metallic material plated with a zinc-based material to bending involving a heat treatment. The curved metallic material has high strength and has excellent corrosion resistance after coating, and is hence suitable for use as an automotive member, etc. The outer surface of a tubular metallic material having, on the surfaces thereof, a Zn-Fe alloy deposit film formed in an amount of 30-90 g/m2 per surface and having an iron content of 8-20% and a surface roughness (Ra) of 0.8 µm or less is supported, so as to be freely movable in the axial direction of the metallic material, in two positions apart from each other in the axial direction. While being fed in the axial direction, the metallic material is heated, in the region between the two positions, to a temperature of Ac3 point or higher at a heating rate of 3.0×102 ºC/sec or higher. The metallic material is held so that the period during which the temperature of the surface is 8.0×102ºC or higher is 2 seconds or shorter. Thereafter, the metallic material is rapidly cooled and, simultaneously therewith, that one of the two positions which is located downstream in the feed direction of the metallic material is two-dimensionally or three-dimensionally changed to thereby impart a bending moment to the heated part of the metallic material. As a result, a curved metallic material having, on the surfaces, a zinc-based coating film deposited in an amount of 30-90 g/m2 per surface, having an iron content of 8-35% and a surface roughness (Ra) of 2.0 µm or less, and including an ? phase can be produced. |
