PRODUCTION OF CONTINUOUSLY CAST ROUND BILLET AND APPARATUS THEREFOR

PROBLEM TO BE SOLVED: To obtain a cast round billet for pipe-making having good complete roundness without developing the inner crack, center porosity and center segregation by simultaneously executing the unsolidified rolling reduction from the vertical and the horizontal directions and successively, executing the complete roundness formation with the rolling reduction after solidifying. SOLUTION: The cast round billet 34 drawn out from a mold 32 is allowed to accelerate the cooling with water cooling at cooling roll group 36. successively, this billet is transported to the unsolidified rolling reduction roll group 40 composed of the upper and lower roll pair through guide roll group 38. After executing the rolling reduction to the billet 34 in order, finally, the unsolidified rolling reduction is executed to the billet 34 from four directions at the unsolidified rolling reduction stand 42 to complete the unsolidified rolling reduction. The solidified round billet 43 completed with the unsolidified rolling reduction is successively subjected to the working of complete roundness formation through the solidified vertical rolling reduction stand 44 constituted with the paired vertical rolls and the solidified horizontal rolling reduction stand 46 constituted with the paired horizontal rolls to form the cast round billet for manufacturing a seamless pipe.