| 摘要 |
<p>PURPOSE:To make texture dense and to obtain a product free from central segregation by dropping a molten steel in the form of fine granular drops from plural nozzles under reduced pressure and controlling the solid phase rate of the granular drops forming the lowermost surface in a low range. CONSTITUTION:A molten steel 1 is made into granular jet drops by nozzles 5, 9, 10 and inert gas blow pipe to form granular drops 4 having required sizes in the stage of flowing down the molten steel into a vacuum vessel 3. The molten steel drops onto a casting mold 7 while said steel is cooled thus forming a laminated layer. The solid phase rate of the drops 4 at the point of the time when the molten steel drops is made <=20% at the nozzle 5 which ejects the liquid drops 4 of the initial laminated layer forming the lowermost surface part in order to smooth satisfactorily the lowermost surface of a billet 8. The amt. of the inert gas is increased at the outflow nozzles 9, 10 for the drops 4 falling to the upper part of the billet in such a way that the solid phase is made larger than the solid phase rate of the lowermost surface within a 0-80% range to form very fine granular drops. The steel plate consisting of the very fine crystal grains is thus obtd.</p> |
