Title

PRODUCTIVITY: ASPECTS ON LADLE REFINING

PRODUCTIVITY: ASPECTS ON LADLE REFINING

Authorship

KJELLBERG, BJÖRN

KJELLBERG, BJÖRN

I am this author

DOI

10.5151/2594-5300-29Aciaria-487-504

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Abstract

The typical EAF cycle time is reduced some 1.5 minute each year since 1970. Recently commissioned furnaces operate with less than 50 minutes cycle time. This improved EAF technology is of minor interest unless the ladle refining can match the EAF cycle. Neither the EAF nor the caster cycle time is constant. The variations in these cycles and also the similar variation in the refining cycle must not cause any delays. The layout must then be provided with enough buffer capacity. The refining time is not independent. It is controlled by the primary furnace upstream and the caster downstream the refining process. The treatment must then be adopted to the likely available time considering both the variations in the up/downstream processes and the time lost by the ladle handling. It is not possible to evaluate the available treatment time without statistical models of the actual processes and the plant logistics. Closer studies on the productivity in a number of ladle furnaces and vacuum degassers show the importance of close control of carry over slag, close control of the energy balance, fast and accurate steel sampling and analysis, high ladle furnace heating rate, fast materials handling system, repeatable process steps, and prediction of arrival and departure time. It is difficult to fulfil those requirements without a reliable equipment and process control system.

The typical EAF cycle time is reduced some 1.5 minute each year since 1970. Recently commissioned furnaces operate with less than 50 minutes cycle time. This improved EAF technology is of minor interest unless the ladle refining can match the EAF cycle. Neither the EAF nor the caster cycle time is constant. The variations in these cycles and also the similar variation in the refining cycle must not cause any delays. The layout must then be provided with enough buffer capacity. The refining time is not independent. It is controlled by the primary furnace upstream and the caster downstream the refining process. The treatment must then be adopted to the likely available time considering both the variations in the up/downstream processes and the time lost by the ladle handling. It is not possible to evaluate the available treatment time without statistical models of the actual processes and the plant logistics. Closer studies on the productivity in a number of ladle furnaces and vacuum degassers show the importance of close control of carry over slag, close control of the energy balance, fast and accurate steel sampling and analysis, high ladle furnace heating rate, fast materials handling system, repeatable process steps, and prediction of arrival and departure time. It is difficult to fulfil those requirements without a reliable equipment and process control system.

Keywords

Ladle Furnace, Refining, Vacuum

Ladle Furnace, Refining, Vacuum