Influence of Ladle Addition Practice on the Castability of Typical Low Carbon Low Silicon Steel
Anil Kumar,
Shiv Kumar Choudhary,
Saroj Kumar Singh
Issue:
Volume 3, Issue 1, March 2018
Pages:
1-14
Received:
25 April 2018
Accepted:
14 May 2018
Published:
12 June 2018
Abstract: Continuous casting of low carbon low silicon steel processed though Basic Oxygen Furnace (BOF) followed by Online Purging station (OLP) and Ladle Furnace (LF) inherently suffers from the problem of clogging of submerged entry nozzles (SEN) during casting due to gradual alumina deposition at the inner surface of the refractory wall. This restricts the incoming flow of liquid steel from tundish to mould through SEN and thus limits the productivity of the caster. On the other hand, excess alumina deposition and their periodic dislodgement from the nozzle refractory surface gives rise to undue stopper rod movement and melt level fluctuations in the mould. All these abnormalities lead to decreased production of good quality slabs. In the present work, influence of ladle addition practice on the castability of typical low carbon low silicon steel has been investigated for a conventional thick slab caster. For identification of inclusions characteristics at different stages of processing, liquid steel samples were collected using the lollipop and a specially designed large sampler during casting. Also, the clog deposits in the used SEN and the natures of inclusions in the clog deposits as well as in the liquid steel were identified by SEM–EDS analysis. Subsequently, to measure the process the different plant trials were carried out for several casting sequences using different deoxidation practices. The upstream processing parameter and corresponding casting data with nozzle clogging index (NCI) for a complete casting sequence were examined for evaluating their casting performances. Addition practice of deoxidant and lime during the ladle treatment has been found to have an important effect of the liquid steel casting. It has been clearly demonstrated the faulty addition practice can lead to severe nozzle clogging during casting. Though a series of plant trials the best addition practice has been determined and implemented in the regular production in the plant for ensuring the smooth production of the given grade of steel. For the quantification of steel cleanliness, total oxygen content (T [O]) of liquid steel, was measured from the samples collected after each ladle treatment stage. T [O] of liquid steel was found in the range of 60−120 ppm at OLP and 30−55 ppm at tundish of low carbon low silicon grade of steel.
Abstract: Continuous casting of low carbon low silicon steel processed though Basic Oxygen Furnace (BOF) followed by Online Purging station (OLP) and Ladle Furnace (LF) inherently suffers from the problem of clogging of submerged entry nozzles (SEN) during casting due to gradual alumina deposition at the inner surface of the refractory wall. This restricts t...
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