Eutectoid Point
The eutectoid point is the specific composition and temperature at which a solid state decomposes into two other solid phases. In the steel system, this means the transformation of austenite into pearlite.
Physical-Chemical Mechanism
In the steel system, the eutectoid point is the temperature and composition at which austenite (a finely distributed phase) transforms directly into pearlite (a mixture of ferrite and cementite). This occurs through a continuous transformation of the austenitic structure into pearlitic grains.
Metallurgical Relevance & Welding Risks
With improper handling, eutectoid formation can lead to uneven hardness and stress zones, increasing cracks and wear. It is important that the melting process and cooling are controlled to ensure a homogeneous structure.
Workshop Practice & Action Guidelines
To avoid or control eutectoid formation, it is important:
• To precisely maintain the melting temperature and time.
• To ensure uniform cooling through cooling water or other cooling media.
• For high-carbon steels, to extend the cooling duration to ensure complete pearlite formation.