Isothermal annealing is to heat steel to Ac3, (or Ac1,) above 20-30 ℃. Insulate for a certain time and then quickly Cooled to the subcooled austenite isothermal transition curve near the 'nose' temperature (pearlite transition zone) and heat for a certain time, so that the austenite into pearlite and then slowly cooled down the heat treatment.
The purpose of isothermal annealing is similar to that of complete annealing, but the isothermal annealing is easy to control, and the uniform expected structure can be obtained. For large parts and alloy steel parts, the annealing period can be greatly shortened.
Post time: Nov-01-2017