To improve the quality and the yield of a product by reducing the crack of a steel sheet caused by hot-rolling and also the occurrence of breakage etc.
Reciprocative burners 17a, 17b are slantingly set to the axial direction of a mandrel 5 on both side walls 3a, 3b of a furnace body 3 corresponding to both end parts of the mandrel 5, and flames 18a, 18b from the burners are made to inject toward winding start part 4a of the steel sheet for winding round the mandrel. Gas ventilating holes 14a, 14b communicating with the inner part of this mandrel are opened on the conical wall surface part near both end parts of the hollow fusiform mandrel 5 and also a burner 15 is arranged on the furnace wall side 3a so that the flame 16 is injected toward these gas ventilating holes.
KOMAKI FUJIO
NAKA KENJI
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