Under oxidizing conditions, several of the alloying elements are oxidized and transferred to the slag phase. These must be recovered into the steel since they represent a high value and, in some cases, are environmentally unfriendly if they end up in the disposable slag. Most of the alloy oxidation takes place during the melt-down step, where local high concentrations of alloys are present in the charge.
Oxygen enters the furnace from two main sources:
- Air drawn through the furnace by the off-gas system
- Oxide raw materials, e.g. Molybdenum oxide, recycled EAF dust, etc.
The simplest way to avoid excessive air suction is to operate the furnace at a slight over-pressure. In practice, this task is difficult due to the large fluctuations in furnace pressure, the large volumes of off-gas, and the requirement to keep an acceptable working environment for the steel mill personnel.
This is principally correct but not practically possible, as oxides are present in some materials which will be used due to cost and/or recycling.
Correct, one should make sure there are reductants available to 'bring back' any oxidized valuable element from the slag to the steel phase.
Correct, separation of oxides and valuable elements is a good way of increasing the yield.
Correct, this will not help.
Correct, this follows from the above but note that any 2 differently sized grains sectioned at random could give the same Feret diameter depending on the plane of section.
Correct, this is principally the same as balancing with reductants.
Sorry, try again.
Correct.