Patent ID: 6959479

Claim:
A method of manufacturing a hollow shaft (b) with a flange (a) at one end thereof, comprising the steps of preparing a movable die ( 17 ) with an upper recess ( 17 a ) on an inside surface thereof and a mandrel ( 20 ) at a center position thereof; placing a fixed die ( 18 ) under said movable die ( 17 ) with a lower recess ( 18 a ) with a same inside diameter of said upper recess ( 17 a ) in said inside surface thereof; inserting a steel pipe ( 19 ) between said movable die ( 17 ) and said fixed die ( 18 ); clamping said steel pipe ( 19 ) in a vertical direction by said movable die ( 17 ) and said fixed die ( 18 ); engaging said mandrel ( 20 ) into said steel pipe ( 19 ); and pressing said steel pipe ( 19 ) while performing a shear spinning treatment on an outer peripheral surface of said steel pipe ( 19 ) so as to deform to only reduce an outside diameter thereof until touching thoroughly with an outside surface of said mandrel ( 20 ) without changing a thickness of said steel pipe ( 19 ) and to integrally form said flange (a), wherein said hollow shaft (b) and said flange (a) are composed of 0.2-0.6 wt % of C, 0.01-0.1 wt % of Si, 0.05-0.5 wt % of Mn, 0.001-0.01 wt % of B, 0.01-0.1 wt % of Ti or Nb, with the balance being Fa, and are subjected to a heat treatment upon finished forming, so as to ensure an improved ductility and thus an improved plastic workability.