PURPOSE: To construct semipermanent refractory walls by cooling castable refractories coating the inside surface of a furnace thickly with many cooling means consisting of endothermic heads made of castings.

CONSTITUTION: Refractory walls 14 are cooled by many cooling means 3 consisting of cooling cylinders 4 and endothermic heads 5 made of castings fixed integrally to the ends thereof. Said heads 5 project to the inside surface of shells 3 and the cylinders 4 are so mounted as to penetrate through the shells 2. Castable refractories 13 re coated thickly over the entire inside surface of the shells 2 so as to embed the heads 5 therein, whereby a refractory wall 14 is formed. The rate of abrasion of the wall 14 of such steel making furnace is small and the wall is used semipermanently.