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steam hammer[′stēm ‚ham·ər]
a hammer that uses steam or compressed air to power the working parts. Steam hammers are among the most widely used machines in the forging and stamping industry. The dropping parts of a steam hammer are connected by a rod to a piston driven back and forth in a cylinder by steam or compressed air. The pressure of the steam or air usually measures 0.4 to 0.7 meganewtons per sq m (4 to 7 kilograms-force per sq cm), with up to 1.2 meganewtons per sq m in the case of large steam hammers. The energy carrier is supplied to the cylinder of the steam hammer from an external source: steam is fed from steam boilers, and air by compressors. Depending on the technological purpose and special design features of the hammers, the following are distinguished: single-acting forging steam hammers and counterblow steam hammers, both with one-sided impact on the anvil; and double-acting steam hammers, which do not have anvils.
Forging steam hammers are used in smith forging and stamping in self-guiding dies. The dropping parts weigh between 3 and 8 tons, and the hammers develop striking velocities of 7 to 8 m/sec and impact energies of up to 125 kilojoules. The frames of these hammers are of the arch or bridge type.
Counterblow steam hammers are used in hot closed-impression die forging and sheet-metal stamping. The dropping parts weigh up to 5 tons. Maximum striking velocity is 5 to 7 m/sec for steam hammers used in hot forging and 3 m/sec for those used in sheet-metal stamping. A unique steam hammer used for hot forging in the USSR has dropping parts weighing 35 tons and an impact energy of 630 kilojoules. The frames of steam hammers used for stamping are either sectional or cast.
Steam hammers without anvils are used in hot forging of heavy parts. They have relative striking velocities of 5 to 6 m/sec and impact energies of up to 1.6 megajoules with hydromechanical linkage of the moving parts and up to 0.4 megajoules with belt linkage.