DSpace
 

Researchspace >
General science, engineering & technology >
General science, engineering & technology >
General science, engineering & technology >

Please use this identifier to cite or link to this item: http://hdl.handle.net/10204/3954

Title: Magnesium: Origin and role in calcium-treated inclusions
Authors: Pistorius, CP
Presoly, P
Tshilombo, KG
Keywords: Aluminium killed steel
Metallurgy
Calcium treatment
Magnesium
Spinel
Issue Date: Aug-2006
Citation: Pistorius, CP, Presoly, P and Tshilombo, KG. 2006. Magnesium: Origin and role in calcium-treated inclusions. SOHN International Symposium on Advanced Processing of Metals and Materials: Principles, Technologies and Industrial Practice, San Diego, California, 27-31 August 2006, pp 373-378
Abstract: Calcium treatment of alumina inclusions, to convert the alumina to molten or partially molten calcium aluminates, is a well-established treatment for steel, to improve the castability of aluminium-killed steel. However, the role of magnesium in calcium-treated steel is not fully clear, nor is the origin of the several percent of magnesium oxide that is often present in calcium-treated inclusions. To study this, steel was sampled after calcium treatment at an industrial steel plant, and the inclusions identified by energy-dispersive X-ray microanalysis (EDX) on polished sections of the samples (analysing the samples in a scanning electron microscope). The predicted fraction liquid in the inclusion was estimated from the ternary alumina-magnesia-lime phase diagram. Inclusions with higher CaO contents generally had lower MgO contents, indicating that the calcium wire is not the origin of the magnesium in the inclusions; this was also confirmed by wet chemical analysis of the calcium wire. Instead, it appears that magnesium-alumina spinel inclusions form during extended ladle contact after aluminium killing and before calcium treatment. While such spinels have been stated to cause poor castability (clogging the submerged-entry nozzle), it is clear that calcium treatment successfully modifies the spinel inclusions to mixed alumina-lime-magnesia inclusions, where the magnesia content contributes substantially to liquefaction of the inclusions: for typical MgO contents of around 10%, the range of Ca:O ratios which yield liquid (or partially liquid) inclusions is extended substantially to lower Ca:O ratios.
Description: 2006 TMS Fall Extraction & Processing Meeting. Sohn International Symposium on Advanced Processing of Metals and Materials: Principles, Technologies and Industrial Practice, San Diego, California, 27-31 August 2006
URI: http://hdl.handle.net/10204/3954
Appears in Collections:Metal and metal processes
General science, engineering & technology

Files in This Item:

File Description SizeFormat
Pistorius_2006.pdf119.29 kBAdobe PDFView/Open
View Statistics

Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.

 

Valid XHTML 1.0! DSpace Software Copyright © 2002-2010  Duraspace - Feedback