Hot upset forging method

A hot upset forging method comprising:

• inserting a workpiece consisting of an alloy, with a bottom face diameter d and a height h satisfying h/d>3, into an insertion hole provided passing through a mold of a height H disposed on an anvil;
• and
• increasing a diameter of the workpiece while decreasing the height of the workpiece to form a forged material,
• wherein the mold satisfies the following relationships (1) to (3):
• (1) a shape of the insertion hole and a cross-sectional shape of the workpiece are substantially similar shapes;
• (2) the height h of the workpiece≦the height H of the mold;
• and
• (3) a largest diameter dl of the workpiece, and a maximum inner diameter D of the insertion hole, in a height range of the workpiece, satisfy dl<D≦dl×1.5, and
• wherein a chamfered portion is formed at from 5 mm to 30 mm from an end portion of the bottom face of the workpiece, and
• wherein a tapered portion, having an increasing diameter in a height direction such that an angle of the tapered portion is 3° or less from vertical, is formed at the insertion hole provided at the mold.