Pearlitic intermediate stage
Pearlitic intermediate stage is a lamellar composite of ferrite and cementite, which forms from austenite at moderate cooling rates. It represents an equilibrium state.
Physical-Chemical Mechanism
With moderate cooling steps, austenite condenses into a lamellar pattern of ferrite and cementite. This process is controllable and results in a homogeneous coarsening of the microstructure.
Metallurgical Relevance & Welding Risks
The perlitic intermediate stage offers a good combination of strength and formability. It prevents the development of martensite, which can lead to hard and crack-sensitive welds. However, an inadequately controlled cooling process can cause excessive coarsening, reducing toughness.
Workshop Practice & Actions
To produce a perlitic intermediate stage, watch for a controlled cooling rate. This can be achieved by selecting the right welding process and parameters. For steels with high zinc content or certain austenitic structures, a special cooling curve is needed to get the desired microstructure.