2090 – 04 – What are Hypoeutectoid and Hypereutectoid Steels?

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Knowing how carbon precipitates is vital in understanding how steel will react at various temperatures and phases. The austenite phase has 0% carbon. As more carbon is introduced, the temperature of phase transformation lowers. Once the threshold of 0.77% carbon is reached, temperature climbs along with carbon content. At 1340 degrees Fahrenheit, steel reaches the eutectoid temperature, which is the lowest temperature that can change austenite into ferrite and cementite.
Steel is then separated into two separate groups:
– Hypoeutectoid steels have a carbon content of under 0.77%
– Hypereutectoid steels which has more than 0.77% carbon content.
These two types of steels have different structure and, therefore, different properties.