HIGH-ENERGY-RATE FORGING (HERF), sometimes called high-velocity forging, is a closed-die hot- or cold-forging
process in which the stored energy of high-pressure gas is used to accelerate a ram to unusually high velocities in order to
effect deformation of the workpiece. Ideally, the final configuration of the forging is developed in one blow or, at most, a
few blows. In high-energy-rate forging, the velocity of the ram, rather than its mass, generates the major forging force.
Table 1 lists the die-closing speeds of forming machines, and it is apparent that the maximum impact velocity of HERF
machines is about three to four times that of conventional drop hammers. Typically, the ram velocity at impact in the
HERF machine is in the range of 5 to 22 m/s (16 to 72 ft/s); ram velocities range from 4.5 to 9.1 m/s (15 to 30 ft/s) for a
power-drop hammer and from 3.6 to 5.5 m/s (12 to 18 ft/s) for a gravity-drop hammer.