Behavior and Mechanism of Inclusion Deformation in Type 430 Stainless Steel During Isothermal Compression

To clarify the deformation behaviors and mechanism of various kinds of inclusions in type 430 stainless steel during hot rolling, isothermal compression experiments using Gleeble-3500 thermo-mechanical simulator were conducted with different deformation temperatures [1273 K to 1473 K (1000 degrees C to 1200 degrees C)], reduction ratios (25 to 75 pct), and strain rates (0.01 to 10 s(-1)). Experimental results showed that the typical inclusions in the as-cast of type 430 stainless steel were single-phase CaO-SiO2-Al2O3-MgO inclusions, single-phase MgO-Al2O3-TiO x -Cr2O3-MnO inclusions, and multi-phase CaO-SiO2-Al2O3-MgO + MgO-Al2O3-TiO x -Cr2O3-MnO inclusions. Only the CaO-SiO2-Al2O3-MgO phases in inclusions were deformable during isothermal compressive deformation as the temperature exceeded 1273 K (1000 degrees C) but the MgO-Al2O3-TiO x -Cr2O3-MnO phases did not. Higher deformation temperature, reduction ratio, and strain rate promoted the deformation of CaO-SiO2-Al2O3-MgO phases and resulted in larger average aspect ratio of them after the isothermal compression. The deformation behavior of multi-phase inclusions depended on the major phase, i.e., either CaO-SiO2-Al2O3-MgO or MgO-Al2O3-TiO x -Cr2O3-MnO. Young's modulus, solidus and liquidus temperatures, and liquefaction rate of inclusions were calculated and compared. Experimental and calculated results demonstrated that liquefaction rate higher than 40 pct could be a better index to quantitatively evaluating the deformability of inclusions during isothermal compression.