Continuous casting crystallizer covering slag special for extra-thick slab peritectic steel and preparation method thereof

The invention discloses continuous casting crystallizer covering slag special for extra-thick slab peritectic steel and a preparation method thereof. In the covering slag, a peritectic reaction is performed in the process of solidifying the peritectic steel, and the overquick or overlarge volume contraction of the peritectic steel leads to the surface quality problems such as casting blank cracks, and causes dangers in a continuous casting process. In consideration of the characteristics of the peritectic steel, the covering slag for the extra-thick slab peritectic steel shall be cooled slowly and has higher alkalinity and melting points so as to increase the heat resistance of a slag membrane of the covering slag, reduce the speed of transferring heat outwards by casting blanks, and increase the uniformity of heat transfer.