Alloying with gas injection

Alloying can be done during tapping by simply dropping the material on the surface, or with a carrier gas. The dissolution and homogenization of the alloying additions are enhanced by stirring and small particle size. Stirring intermixes top slag with the bath which should be minimized to avoid oxidation.  The vigorous intermixing of top slag with the bath can be minimized by the lowering of a refractory lined cylinder into the liquid steel. This will minimize reaction of steel exposed to air.

Heating of steel

Synthetic slag practice with argon stirring or injection of solid powder requires higher tap temperatures to compensate for the heat losses during refining. This increased tap temperature causes problems in BOF such as poor phosphorus removal and  increased lining wear. In EAF  increased power and electrode consumption and an increase in furnace time are the main issues to tap steel at higher temperature.

Arc heated ladle processes have been developed. Ladle arc furnace in addition to allowing for lower temperatures, also allows steelmakers to perform many metallurgical processes like

i)    Bath homogenization by argon stirring

ii)    Inclusion removal and inclusion engineering

iii)    Desulphurization by synthetic slag or by injection metallurgy

iv)    Holding of ladles for long periods if and when need arises for example in sequence            casting.

v)    The ability to make addition of alloying elements.

There are three different types of ladle arc heated furnaces: Induction stirred, gas stirred by porous plugs and gas stirred using a tuyere.