Grain type

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In metallurgy a distinction is made between primary, secondary and austenite grains .

Primary grain

The primary grain / primary structure , also known as cast or solidification grain , is the structure that occurs during solidification immediately after casting. It has meaning when used in castings.

Secondary grain

The primary grain is transformed into the secondary grain (secondary structure) in the solid state by heat treatment and forming processes . Influence on the secondary structure, e.g. B. of steel have:

  • the chemical composition of the material
  • its austenite grain size
  • the degree of deformation and
  • the heat treatment.

Austenite grain

The austenite grain size is the grain size of a steel in the austenitized state. It depends on the type of melting of the steel, the temperature and holding time in the austenitizing area. The austenite grain is particularly important when assessing the sensitivity of a steel to overheating and its hardening depth.