Standard Forging Classifications of Gears

Standard Forging Classifications of Gears

Open Die Forging.
This method produces a rough dimensioned piece by mechanical deformation between an upper and lower die (hammer and anvil) in an open frame press or hammer. Open die forgings may be specified to be upset forged to increase center densification. An upset forging is produced when the billet is initially hot worked in one direction, and then is rotated 90 degrees and hot worked again. Upset forgings are often used for critical high speed gearing, greater than 30,000 feet/minute (152 m/sec) pitch line velocity, which develop high centrifugal stress at the center.
Closed Die Forging.
This method produces a closer toleranced piece, generally smaller than an open die forging. The upper and lower dies trap the steel billet in a closed (confined) cavity and the press action deforms the metal to fill the die cavity, producing a more exact contoured forging.
Rolled Ring Forging.
This method produces a donut---shapedwork piece. Typically the process involves piercing a pancake---shaped billet with amandrel and shaping the ring by a hammer action between themandrel and the press anvil. Large diameter rings are rolled on a roller press from circular billets containing a central hole.