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The heat treatment of annealing has as its objective the elimination of internal tensions and the achievement of a good workability of the tool. In this case, we also talk about “steel softening”.

In addition to steel, the annealing treatment can also be performed on cast iron, brass, bronze and some aluminum alloys.

Different cycles are available in relation to the hardness and structure to be obtained.

Complete annealing: has the scope of mitigating both the effects on the structure due to solidification and plastic deformation, and the heterogeneity of the chemical composition of the metal. At an industrial level, isothermal annealing is preferred: the two cycles differ substantially only as regards the cooling phase.

Heterogenization annealing: involves a clear separation of the phases causing the coalescence of the globule. The globular structures of the treated metals become coarser so as to obtain excellent cold deformability and, consequently, better workability on machine tools.

Subcritical or workability annealing: it is one of the most frequent cycles for construction steels. It is practiced on the parts obtained with the use of strong cold or hot plastic deformation, with consequent high thermal stress. The process temperatures differ according to the steel used: they never exceed the AC1 limit, but they are significantly close to 700 ° C.

Through annealing, the microstructure of the material is altered, causing changes in its properties such as flexibility and hardness.

The typical result is the removal of defects in the crystal structure. It can also have the purpose of standardizing the chemical composition of the steel, in which case heating is performed at a higher temperature and for longer times

  • Slow cooling in the furnace
  • Removal of defects in the structure