Austenite-ferritic stainless steel is not enough to make stainless steel have pure austenite structure at room temperature or very high temperature due to the expansion of γ region and the effect of stabilizing austenite elements, so it is austenite-ferrite. In the complex state, the amount of ferrite can also vary in a wide range due to the composition and heating temperature.
There are many stainless steels in this category, such as low-carbon 18-8 chromium-nickel steel, 18-8 chromium-nickel steel with titanium, niobium, and molybdenum, especially in the structure of cast steel, ferrite can be seen, in addition to containing Chromium-manganese stainless steels with chromium greater than 14-15% and carbon less than 0.2% (such as Cr17Mn11), as well as most of the chromium-manganese-nitrogen stainless steels currently studied and applied.
Compared with pure austenitic stainless steel, this type of stainless steel has many advantages, such as higher yield strength, higher resistance to intergranular corrosion, lower sensitivity to stress corrosion, less tendency to produce hot cracks during welding, and good casting fluidity. and many more. The disadvantage is that the pressure processing performance is poor, the pitting corrosion tendency is large, it is easy to produce c-phase brittleness, and it shows weak magnetic properties under the action of a strong magnetic field. All these advantages and disadvantages are derived from the ferrite in the structure.
