Study on Secondary Phase Precipitation Behavior of Ship Plate Steel Slab Under Different Cooling Rates in Continuous Casting Process

The blank surface quality could be prevented through the control of the second phase precipitationPrecipitation. In this study, the precipitationPrecipitation behavior of carbon-nitrides was studied by a high-temperatureHigh temperature confocal laser scanning microscope under the cooling ratesCooling rate of 0.1, 0.5, 1.0, 3.0, and 5.0 ℃/s. And the effects of cooling rateCooling rate on the morphology and distribution of precipitates were obtained. The results show that the initial precipitationPrecipitation temperatureTemperature and “fast-growing region” of carbon-nitrides are varied under different cooling ratesCooling rate. As the cooling rateCooling rate increases, the nucleation location of carbon-nitrides changes from grain boundaryGrain boundaries to grain interior. Meanwhile, its size and quantity gradually decrease. When the cooling rateCooling rate is larger than 1 ℃/s, the carbon-nitride mainly precipitates in grain interior. Combining the above research, a new secondary coolingSecondary cooling method for ship plate steelShip plate steel slab is proposed and industrial tests are conducted, which improves the surface quality of the slab in continuous castingContinuous casting.