THIN-STRIP CASTING PROJECT OF THE KRUPP-STAHL-AG AND VDM-NICKEL-TECHNOLOGIE-AG

The twin-roll casting technology described in this report, which makes it possible to produce steel strip directly from the melt, is based on the pioneer work of Sir Henry Bessemer, who proposed a downwards vertically casting machine. The lateral sealing of the casting rolls was to be ensured by flanges, which overlap alternately the rolls. The strip casting process developed by Krupp Stahl and VDM Nickel-Technologie is based on a different principle. The diameters of the casting rolls differ from one another. The smaller top roll is arranged in an 11 o'clock position above the bottom roll. The steel melt is guided between the rolls from one side by means of a refractory casting nozzle. The advantage over Bessemer's proposal consists in the higher stability of the casting process against breakouts. The new process makes, however, exacting demands on the control of the liquid steel level and the sealing between casting nozzle and casting rolls. Hitherto the plant has carried out trials with high-alloy steels, nickel alloys and copper-nickel. At present, the maximum cast strip length is 250 m. This corresponds to a strip weight of about 3 t. The solidification structure of the cast strip consists of two columnar crystal zones having grown in each others direction with a globular zone in-between. The thickness of the cast strip is mainly determined by the casting rate.