Improvement in billet and bloom surface quality through developments in mould level and powder depth measurements and control, including automatic pow[d]er feed

Optimised mould heat transfer and mould lubrification are essential factors to ensure good surface and sub-surface quality of as-cast products. These factors in turn rely on a uniform cover of mould powder and a stable meniscus level. An array-based radiometric mould level measuring device has been developed to measure both steel level and powder depth. The aim of this is to allow more stable meniscus level control and closed loop control of powder depth. Trials with this device have been limited due to development problems, but the principle of the measurement technique has been proven. Online trials with outputs of both meniscus level and powder depth have not been possible. A thermographic imaging system has also been developed as an alternative means of indicating the powder depth. A mechanical support has been built to move the camera to allow maximum coverage of the mould surface and industrial tests have been undertaken. Software has been developed to indicate areas requiring powder additions. Characterisation of mould powders has been undertaken and equations have been developed to relate consumption rates to casting parameters. These equations have been used to control the feed rate of a gravity fed powder delivery system. Other methods of powder transportation have also been considered, together with how closed loop powder depth control could be implemented. Industrial tests have been undertaken on billet, large bloom and beam blank casters. The suitability of the various techniques developed within the project to different types of caster has been assessed.