Closed Die Forging

Closed die forging is when metal is placed in a die resembling a mould, which is attached to the anvil, Usually the hammer die is also shaped.  The hammer is then dropped on the piece, causing the metal to flow and fill the die cavities.  Excess metal is squeezed out of the die cavities, forming what is commonly referred to as 'flash'.  The 'flash' colls more rapidly than the rest of the material; this cool metal is stronger than the metal in the die so it helps prevent more flash from forming.  This also forces the metal to completely fill the die cavity.  After the forging process is complete the flash is removed.