Abstract:The secondary cooling of slab continuous casting was one of the important factors affecting the quality of slab, and the selection and layout of nozzle was particularly important for secondary cooling uniformity. Based on the production characteristics of ultra-thick slab with over 400mm thickness, like low casting speed and angle temperature, uneven horizontal temperature and long metallurgical length, the design criteria of the nozzle selection and layout was present. Additionally, according to the experimental parameter provided by nozzle manufactory and equipment design feature, the selection and layout of the nozzle was analyzed in terms of spray angle, installation height, nozzle spacing, and arrangement form. The suggestion was proposed for ultra-thick slab edge cooling weakening and water flow density uniformity. Proven by the production, both shape/size of ultra-thick slab and the surface /internal quality are very good.