Austenite grain classification
Austenite grains have three different concepts: starting grains, actual grains and essential grains.
(1) Starting grains. It refers to the grains at the end of the austenite transformation process during heating. The grain size at this time is called the initial grain size of austenite.
(2) Actual crystal grains. Refers to the austenite grains finally obtained under a specific heating condition during heat treatment, and their size is the actual grain size of austenite.
(3) Essential crystal grains. Refers to the tendency of austenite grains to grow when various steels are heated. The grains that are easy to grow are called intrinsically coarse grains, and those that are not easy to grow are called intrinsically fine grains.