Byucougar
In my youth I worked at a stell plant alloying and degassing steel (in the same process). We used argon instead of nitrogen since apparantly Nitrogen affect the quality of steel/iron before casting for certain qualities.
When we lost temperature before the alloying we also used pure oxygen (with lances) to gain the needed temperature, this also added gasses to the molten iron/steel.
I guess everything depends on what you intend to use the iron (steel?) for. Som qualities/applications isn't sensitive and some others are. So it is really a question for metallurgist to answer.