Behavior of ferrite in AISI304 stainless steel strips

To determine the formation and transformation behavior of retained ferrite in AISI304 austenitic stainless steel strips during the solidification process, the characteristic of retained ferrite and the solidification microstructure in the steel strips were studied by color metallography, electro-etching, electron backscatter diffraction and X-ray diffraction analysis. In the cast strips, there are three kinds of solidification structures:fine cellular crystals in the surface layer, equiaxed grains in the center, and columnar dendrites between them. The morphology of retained ferrite is rod-like in the fine cellular crystal zone in the surface, comb-like in the columnar dendrite zone, and curved branch in the equiaxed zone in the center. The mass fraction of retained ferrite in the cellular zone, the columnar dendrite zone, and the central equiaxed zone is about 4. 60% to 6. 60%, 3. 60% to 3. 70%, and 11. 27% to 11. 34%, respectively. The residual ferrite shows a W-shaped distribution in the thickness direction.