A new method for steel desulphurisation and non-metallic inclusion con
trol using magnesium produced from its oxide in situ in steel melts ha
s been developed. This involves the pneumatic injection into the steel
ladle of a granular product (average size 0.5 mm dia.) which consists
essentially of fine aluminium particles encapsulated by a coating com
prising a combination of calcium and magnesium oxides based on the for
mula (by weight): 50.27%MgO, 20.86%CaCO3, 18.18%Al, and 10.69%CaF2. At
steelmaking temperatures the free energy diagram predicts that the al
uminium will reduce MgO and release magnesium gas for desulphurisation
and deoxidation and such a reaction has been confirmed by earlier lab
oratory experiments. In the present work 180 kg of the reagent describ
ed above was injected with a Scaninject lancers injection system into
40 t of aluminium killed SAE 1513 steel contained in an alumina ladle
at 1570-degrees-C, and for comparison purposes an identical cast was t
reated in exactly the same way with CaSi. Both treatments achieved hig
h levels of desulphurisation and clean steels. Inclusion studies revea
led almost identical inclusion distributions for both treatments, and
microchemical analyses in the scanning electron microscope showed that
the inclusions present were typical of those expected in calcium and
magnesium treated aluminium killed steels.