Thermophysical Properties and Solidification Defects of Fe-22Mn-0.7C TWIP Steel

The thermophysical properties and solidification defects of Fe-Mn-C twinning-induced plasticity (TWIP) steel have been experimentally studied. The liquidus and solidus of Fe-22Mn-0.7C TWIP steels are measured to be 1380 +/- 10 and 1270 +/- 10 degrees C, respectively. The thermal conductivity of Fe-22Mn-0.7C steel is the lowest compared with that of carbon steel Q235 and stainless steels 304 and J4. Combined with the highest thermal expansion coefficient of TWIP steel, internal cracking is apt to occur due to the extremely large thermal stress during cooling and heating. Severe shrinkage porosity and segregation have been observed in high alloy TWIP steel with large mushy zone. The macrosegregation of manganese along the central line is not as serious as that of carbon in TWIP steel, and the manganese/carbon microsegregation increases with the increase of not only manganese/carbon but also carbon/manganese. TWIP steel is liable to exhibit central shrinkage porosity due to the coarse dendrite and serious microsegregation during solidification. In order to improve the homogeneity and compactness of TWIP steel during traditional slab casting, combining application of control technology, such as decreasing steel casting temperature, descending water cooling intensity, and utilizing electromagnetic stirring and/or soft reduction, is strongly recommended.