Quenched steel pipe member, vehicle axle beam using quenched steel pipe member, and method for manufacturing quenched steel pipe member

摘要

A quenched steel pipe member is formed of a GI galvanized steel pipe, in a middle section in a longitudinal direction of the GI galvanized steel pipe, a cross-section perpendicular to the longitudinal direction has a substantially V shape including a contact section at which opposite parts of an inner circumferential surface of the GI galvanized steel pipe come into contact with each other, the contact section is bonded using a Fe—Zn alloy phase, and a micro Vickers hardness at a location 50 μm deep from a base material surface layer is 95% or more of a micro Vickers hardness at a location 200 μm deep from the base material surface layer.