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As-cast transformation-induced plasticity (TRIP) steels with two different aluminium contents (2.80 and 6.75 wt-%) were subjected to investigate the effect of aluminium content on the tensile strength and hot ductility. As the Al content increases from 2.80 to 6.75 wt-%, the third brittle zone of the steel is shifted from 950–750°C to 800–750°C. The 6.75 wt-% Al-TRIP steel is a typical δ-TRIP steel that contains 44.5 wt-% δ-ferrite compared with no δ-ferrite in the 2.80 wt-% Al-TRIP steel. The solidification behaviour of these two types of TRIP steel was compared by calculating equilibrium phase diagrams. The 6.75 wt-% Al-TRIP steel was found to have better ductility than the 2.80 wt-% Al-TRIP steel below 1100°C.

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Cooling in the continuous casting mold is the essential process of the molten steel solidifying into a slab shell. The synergistic relationship of casting state, process operation, continuous casting equipment, and other factors is complex and has a significant influence on thermal transfer in the mold. Therefore, a concept of "process thermal dissipation rate" defined by mold system thermal input and output was proposed in this work. The thermal input of molten steel was calculated through the casting temperature, and the slab residual thermal at the outlet of the mold was calculated by the solidification heat transfer model. Consequently, the thermal dissipation rate was calculated to quantify the multi-factor cooperative relationship of mold. The industrial case reflected that the thermal dissipation rates of three stable castings were 12.5%, 14.3%, and 18.8%, respectively, and all of them were obviously abnormal in unsteady casting such as start casting, changing tundish, and end casting. The results above indicated that the thermal dissipation rate could characterize the mold cooling target under the cooperation of complex factors and provide a new method for the dynamic evaluation of the mold system cooling effect with different casting states.Accordingly, the correlation analysis between superheat, casting speed, cooling water flow, and thermal dissipation rate revealed the synergistic influence law of multi-operation on mold cooling effect, which provided a new idea for the precise control of multi-process collaboration in continuous casting.