| 摘要 |
PURPOSE:To eliminate the center segregation for a tool steel billet by adjusting the relation between casting velocity and over heat degree of molten steel in a tundish by the prescribed inequality and finding a distance from solidify starting point in a mold to electromagnetic stir starting point, to continuously stir the molten steel to the solidifying position for the center part of cast billet. CONSTITUTION:The tool steel billet having a square or a rectangle section of <=22,500mm<2> section and >=100mm short side is continuously cast. Then, the relation between the casting velocity Vm/min and the over heat degree DELTAT deg.C of molten steel in the tundish 2 is adjusted by the inequality DELTAT<=50 deg.C (provided that in case of V<=0.4m/min) or DELTAT<=(64.6-36.4V) deg.C (provided that in case of V>0.4m/min). Further, the distance Z from the solidify starting point in the mold 3 to the electromagnetic stir starting point in the mold 3 to the electromagnetic stir starting point is found by inequality Z<=(3.5/K)<2>V (provided that K is constant of solidifying velocity cm/min<1/2>) and the section, to the position at when the center part of cast billet is solidified, is continuously stirred by the electromagnetic stirrer 4-7. In this way, the center segregation in the cast billet is improved. |
