A new system for pouring steel from ladle into tundish

The objective of the project was to re-engineer, develop and test a new system to pour liquid steel from the ladle to the tundish. The system designed ensures over pressurisation of the complete casting with respect to atmosphere by steel throttling at the bottom of the shroud. The benefits expected were: - improved steel quality and productivity, via reduction of downgraded steel, - improvement of the steel yield, - more efficient casting operations. The workgroup was composed of CSM, VESUVIUS, IRSID, Acciai Speciali Terni (AST) and Ugine. In particular: - VESUVIUS acted as refractory systems designer and maker; - UGINE and AST acted as plant partners, by contributing to the engineering, adaptation to plants and direct application of the solutions proposed, respectively, the reverse stopper for UGINE and the LS Rotor for AST; - CSM, project co-ordinator, and IRSID acted as RD - engineering, manufacturing of LS-Rotor prototypes together with the needed LS manipulator and the proper adaptations required for LS-rotor use at AST. b) UGINE allowed six plant tests of the reverse stopper on the plant allowing to individuate some fundamental problems in operating with the system; c) AST equipped its plant with LS manipulator and adaptation for rotor, also providing to hot test for the manipulator. Nevertheless, no trials were performed as a result of the not fully encouraging results of the modelling test on the system; d) CSM, apart from the co-ordination activity, provided for: a) a method to compare the performance of LS-rotor with that of a standard system, b) water modelling to test the LS-rotor starting from the original configuration up to an enhanced one able to overcome the process drawbacks formerly encountered; e) IRSID performed studies on vortex formation in ladle, with a literature survey on vortex formation and air ingress in ladle shroud and cold model tests, with a ladle-tundish system. As a result of the workgroup activity: - the reverse stopper tests gave satisfactory results only on 2 over 6 tests at UGINE. Moreover, from model studies at IRSID, problems of slag entrapment and in turn affection of steel cleanliness were magnified with the proposed system. The reason was that vortex are not delayed at the end of ladle emptying, metal projections in tundish during ladle change periods are strong and the retention in tundish of slag droplets is reduced; - the LS- rotor tested according to the original design presented strong safety problems due to liquid metal splashing out of the tundish. An enhanced configuration of the LS-Rotor design, giving no steel splashing in the tundish, has been developed and tested on cold model; the manufacturing of the modified rotor was estimated too expensive and not completely reliable for its industrial realisation.