O and N are both soluble in molten Fe, and will therefore be present after "purging". Ar is not, or at least not to any appreciable extent. I am not aware of any conventional practice that uses N as a purge with liquid Fe, but I'm certainly not an expert on Fe foundry techniques.
Iron castings do contain dissilved gases which can acting as potential nucleating sites during solidification. Ofcourse addition of suitable inoculants with nitrogen bearing compounds can also deliver the issue. I fail to understand your need to use 100% purity nitrogen while cast iron molten metal is so impure with high levels of S,P and other elements from auto scrap.
Is this a research project or a class assignment.
" All that is necessary for triumph of evil is that good men do nothing".
Edmund Burke
we are making a casting - and purge the ladle with pure nitrogen - looking at using a membrane system with liquid backup to save money - what issues will I have if I use a lower purity nitrogen?
A commercial grade nitrogen is adequate for your application. There is no need for using high or ultra high purity nitrogen. Only be careful about the moisture in the gas. If you could pass it through a preheater it will be helpful.
" All that is necessary for triumph of evil is that good men do nothing".
Edmund Burke
Agree with previous posts. We did do these tests with industrial grade nitrogen on cast iron.
Be prepared to have tens of ppm's of nitrogen in your steel though, which can be advantegeous in some steels (eg for enamelling or for solid sol. strengthening), but the steel will be extremely sensitive for stretcher strains.
Byucougar, I am wondering are you in Utah? If so you might want to contact Pacific States Cast Iron Pipe Co. in Provo, UT someone here could probably would be able to help you with your questions as we use nitrogen in our iron melting process.
. I am a maintenance reliability engineer so I am not familiar with the exact process, but I am sure a number of our engineers could help with this issue.
