The processed being induced transformation die high intensity metal tubing and its production mannered null mass which are superior in

摘要

PROBLEM TO BE SOLVED: To provide a high-strength steel pipe which exhibits an excellent workability in a hydroforming step wherein the pipe is formed into a desired shape by putting it into a metal mold and applying pressure to the inside of the pipe to push it in its axial direction; and a method for producing the same.;SOLUTION: This steel pipe of a strain induced transformation type excellent in hydroformability comprises 0.04-0.30% C, 0.3-3.0% the sum of Si and Al, and the balance being Fe and unavoidable impurities and consists of a ferrite phase, which is the maximum-volume-percentage phase, and the second phase containing at least 3 vol.% austenite; the ratio (Vuniaxial/Vshear) of the volume percentage (Vuniaxial) of the austenite phase under a uniaxial tensile deformation of 15% in terms of equivalent strain to the volume percentage (Vshear) of the austenite phase under a shear deformation of 15% in terms of equivalent strain is 0.4-0.8.;COPYRIGHT: (C)2003,JPO