The process involved modifying an open hearth furnace to use oxygen instead of air.
[1] The use of oxygen in the open hearth negated the need for an external fuel source, as with Linz-Donawitz converters.
[2] The furnaces were used at the United Steel Companies at the Appleby-Frodingham steelworks near Scunthorpe, Lincolnshire, England as an alternative to installing completely new oxygen based steelmaking plant.
[1] Conversion time of the open hearths to the oxygen-based process was around 28 days on average, with a stated capital cost of £180,000 each.
[4] In 1966 the Appleby-Frodingham steelworks decided to replace the AJAX production with Linz-Donawitz (LD) converters.