Annealing

After a material is shaped by a cold forging press, undesirable residual stress in the material may be introduced. Annealing is a heat treatment process used to relieve internal stresses, induce ductility, and improve the mechanical properties of cold forged products. At Li-Hsing, we are equipped to provide various annealing processes including normalizing, process annealing, full annealing, and spheroidizing.

Normalizing

Normalizing is used to remove undesirable residual stress and unevenness grain structure introduced during the forging process. This process can improve ductility and toughness of the forged product. This process also improves machinability of the product. To perform normalizing, a metal material is cooled in still air after heating the material above 900℃ (approximately 55 °C above Ac3 or Acm line). Normalizing is considerably more economical than full annealing since there is no added cost of controlled furnace cooling.

Process Annealing

Process annealing is a heat treatment cycle that restores ductility of a work piece and thus allows the work piece to be worked further without breaking. Ductility is important in creating and shaping a complex forged product. Process annealing is typical used to treat work-hardened products made out of low-carbon steel (< 0.25% Carbon). To perform process anneal, a work piece is heating to 700 ℃, and held there long enough to relieve residual stresses in the piece. The work piece is then finally cooled slowly to room temperature. The work piece is then ready again for additional cold forging.

Spheroidizing Annealing

Spheroidizing annealing is a heat treatment process used for high carbon steel with carbon greater than 0.6%. Low carbon steel is seldom spheroidized for machining, because it is excessively soft and gummy in spheoridized condition. High carbon steel needs to be spheroidized before it can be used to produce cold forged product. To perform Spheroidization, a metal material is heated to a temperature just below the material’s annealing point and held material at this temperature for a prolonged period of time. The material is then cooled gradually. This annealing process produces material with structure in which all the Cementite is in the form of small globules (spheroids) dispersed throughout the ferrite matrix. In this state, the material can be cold forged easily.