Subcutaneous longitudinal crack control method for peritectic high-aluminum steel continuous casting billet

The invention belongs to the technical field of metallurgical steelmaking, and particularly relates to a peritectic high-aluminum steel continuous casting billet subsurface longitudinal crack control method which is used for reducing the AL content of peritectic high-aluminum steel. A horn mouth large ladle sleeve is designed for plug-in casting and a silica gel sealing gasket; designing covering slag special for peritectic alloy high aluminum, and stabilizing the viscosity and crystallization temperature of the covering slag; the argon blowing flow of the large ladle sleeve is increased to 70-90 L/min; the highest pulling speed of peritectic high-aluminum steel is controlled to 1.4 m/min; designing a special slag salvaging process for the crystallizer; the variation range of the insertion depth of the submersed nozzle is reduced; and a weak cooling peritectic water distribution process is adopted. The influence of Als element redox on denaturation of the casting powder is reduced, and the denaturation time o