The question was why increasing to 18 Cr in austenitic staibnless
steels when 11 is enough to make it stainless.
The answer is that when casting the steel it is better to have ferrite
forming from the liquid and that he auqtenite is
formed as a solid state transformation at a lower temperature. If
only 11 Cr there is no ferrite at high temperature.
The ferrite/austenite transformation is affected by many alloying
elements and the balance between these phase is a key to controlling
the properties of steel.
- posted 15 years ago