HOLLOW MEMBER AND HOLLOW MEMBER MANUFACTURING METHOD

Abstract: the present hollow member has a circumferential hardness difference portion in at least a portion in a longitudinal direction along a central axis. when the circumferential hardness difference portion is viewed in a cross section orthogonal to the central axis, a wall thickness difference obtained by subtracting an absolute minimum value of the wall thickness from an absolute maximum value of the wall thickness in a circumferential direction of the cross section is 20% or less of an average value of the wall thickness in a whole circumference of the cross section. furthermore, when an average of integration of vickers hardness in the whole circumference of the cross section is used as a hardness threshold, the cross section includes a low strength range in which the vickers hardness along the circumferential direction is equal to or less than the hardness threshold and a high strength range in which the vickers hardness along the circumferential direction is more than the hardness threshold.

Inventor(s): Nasa SHIMAZAKI, Ryota MATSUBAYASHI

CPC Classification: B21D35/005 (Combined processes according to {or processes combined with} methods covered by groups - ( takes precedence))

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