Austenite to Ferrite and Martensite

[member 392791]

Hello,

I am wondering how I could create only ferrite and martensite from a hypoeutectoid plain carbon steel. I am looking at the TTT diagram, and I don't see how this can be done. If I quench to create martensite, and then temper it I will have ferrite and cementite. I don't see how I could separate the ferrite from the cementite. I don't see pure ferrite anywhere on the TTT diagram, is it a metastable phase that is not shown?

Also, is it possible to create pure ferrite from austenite?

 

[smpowell]

Start by looking at an iron-iron carbide phase diagram. For example, if you take 1030 steel and heat it to 1700F, will become 100% austenite.

Then cool it to 1400F and let it sit for a long time. You will then have a mixture of ferrite and austinite. This is the area between A1 & A3 on your TTT diagram. Note that the transformation time is in the 1000 to 10000 second range.

Use a fast quench to get the steel from 1400F to below the martensite start temperature.

You need a fast quench to prevent any transformation of the austinite before it reaches the martenisite start temperature.