The punch and billet dimensions are shown in Fig. 1(a) and (c). The reduction in area of the billet was 50 %.
The high speed tool steel (SKH51 of 60 HRC) was applied for the punch and container. The contacting surface of
the punch and container with the billet was lapped to 0.4 Rz. The material of the billet was spheroidizing annealed
S10C (surface roughness: 6.3 Rz, 180 HV). The penetration depth into the billet was determined to be twice as
long as the punch stroke due to the 50 % reduction in area of the billet.