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Publication Information and Contributors Forming and Forging was published P2

Fig. 4 Double-frame power hammer used for open-die forging A typical open-die forging hammer is operated by steam or compressed air--usually at pressures of 690 to 825 kPa (100 to 120 psi) for steam and 620 to 690 kPa (90 to 100 psi) for air. These | Fig. 4 Double-frame power hammer used for open-die forging A typical open-die forging hammer is operated by steam or compressed air--usually at pressures of 690 to 825 kPa 100 to 120 psi for steam and 620 to 690 kPa 90 to 100 psi for air. These pressures are similar to those used for power-drop hammers. There are two basic differences between power-drop hammers used for closed-die forging and those used for open-die forging. First a modern power-drop hammer has blow-energy control to assist the operator in setting the intensity of each blow. In hammers for closed-die forging the hammer stroke is limited by the upper die surface contacting the surface of the lower die face. In open-die forging the upper and lower dies do not make contact stroke-position control is provided through control of the air or steam valve that actuates the hammer piston. The second difference between closed- and open-die forging hammers is that the anvil of an open-die hammer is separate and independent of the hammer frame that contains the striking ram and the top die. Separation of the anvil from the frame allows the anvil to give way under a heavy blow or series of blows without disturbing the frame. The anvil may rest on oak timbers which absorb the hammering shock. High-Energy-Rate Forging HERF Machines High-energy-rate forging machines are essentially high-speed hammers. They can be grouped into three basic designs ram and inner frame two-ram and controlled energy flow. Each differs from the others in engineering and operating features but all are essentially very-high-velocity single-blow hammers that require less moving weight than conventional hammers to achieve the same impact energy per blow. All of the designs employ counterblow principles to minimize foundation requirements and energy losses and they all use inert high-pressure gas controlled by a quick-release mechanism for rapid acceleration of the ram. In none of the designs is the machine frame required to resist the .