| 摘要 |
PURPOSE:To improve heat extracting efficiency and to form a thick and dense chill crystal by supplying a mold additive having low viscosity and low softening temp. to the molten steel in a casting mold thereby closing the spacing between the solidified shell and the mold. CONSTITUTION:A mold additive to be used is required to have <=1.0 poise viscosity at 1,300 deg.C and <=900 deg.C softening temp. The molten steel supplied into the mold forms a solidified shell from the part in contact with the mold but as the solidification progresses, the molten metal shrinks. A space is consequently generated between the mold and the solidified shell, and the heat extracting efficiency of the mold decreases. However the above-described mold additive has a satisfactory liquidizing characteristic and therefore the space is closed by the molten slag of the mold additive and the heat extracting efficiency of the mold is improved. The molten metal is thus quickly solidified and the chill crystal having 5-10mm. thickness is formed to the billet. |
