Continuous casting

Abstract

The TRD-BOC Dc transferred are plasma system is now in operation on 8 tundishes in Japan and Europe. The first system was installed in 1987 on a single out let slab caster and since then units have been used on multi strand billet and slab casting machines to control tundish steel temperature within ± 1°C of the optimum. Quality improvements are attributable to the decreased and constant superheat of the steel that enters the mould. This gives a finer and consistent microstructure in the semi and finished product. The caster itself works at a steady hjeat-load so that stresses and forces in the cooling and solidifying semi are reduced thereby lowering frequency of surface defects. Torch capacities of up to 1.4 MW are available. Variation of temperature at ladle changeover can be minimised and cool steel from the ladle can be rapidly heated to its optimum mould entry temperature. Because rapid heating at full tundish flow is possible, the converter can be tapped at lower temperatures. This decrease, which can be up to 30°C, reduce ≪tap to tap≫ time and has a significant beneficial effect on operating cost and output of the steel plant as a whole. Experience from the operating units has shown that heating efficiencies of up to 80% can be achieved with correct design of the plasma hood, clean steel surface and insulated torch tip. Service lifes of the cathodic plasma torch of 140 hrs have been reported by users of the TRD-BOC system.