How do you add N in steel 7

[Hercules28]

Dear all,

How do you add Nitrogen in Steel/Stainless steels?
I have found a paper

http://www.springerlink.com/content/mt834u5562168827/

That talks about adding nitrided manganese MnN2
or Caclium Cyanamide A.

What's the effect of the properties? I know this is a vague question so to narrow down, what's the effect on stainless?
I know that in duplex it stabilizes the austenite.

 

[mcguire]

Nitrogen is added to stainless steel in the argon-oxygen decarburization step (AOD). Nitrogen gas is injected along with argon and it dissolves in the steel.
Nitrogen is soluble in austenite up to about 0.25% depending on the manganese level. Manganese increases the solubility. It has essentially no solubility in ferrite at room temperature.
In solution in austenite nitrogen does three important things. It stabilizes austenite. It increases resistance to pitting corrosion. It causes significant solid-solution strengthening. All of these effects are well quantified and available in the literature.
Nitrogen can also be added to solid steel by various processes which involve diffusing it in from a nitrogen-rich environment, but this is done only to produce surface layers enriched in nitrogen.

Michael McGuire

http://stainlesssteelforengineers.blogspot.com/

 

[arunmrao]

Another simple method to add Nitrogen in stainless steel ,is usingt Nitrogen containing LCFeCr.

_____________________________________
"It's better to die standing than live your whole life on the knees" by Peter Mayle in his book A Good Year

 

[Metalhead97]

Hercules,

Please read this book:

http://www.amazon.com/High-Nitrogen-Steels-Manufacture-Applications/dp/3540664114

It may have what your looking for.

MH

 

[bhollands]

We add nitrogen to stainless using nitrogen bearing ferrochrome. Add it at the end of the heat. It tends to create a lot of slag as it melts in. It stabilizes austenite so it will change the austenite/ferrite balance in your steel. I have not seen other effects on the mechanical properties.

Bob

 

[lkrzyzan]

We also use nitrogen containing ferrochrome. A potential suggestion if you use a porous plug is to use a Ar-N gas mixture.

 

[EdStainless]

The other effect, and a strong one, is that N is an interstitial strengthening agent.
High N SS will be significantly stronger than the non-N version (though it will not have much higher creep strength).

Even when we melted small heats we bubbled N through the molten steel. We controlled N levels by mixing N and Ar.

= = = = = = = = = = = = = = = = = = = =
Plymouth Tube

 

[1gibson]

Here is a semi-relevant question: If you have duplex ingots with N content specified (CD4MCuN to be specific) will you lose some N when remelting to pour a large casting? The AOD is already completed during the process of creating the ingot.

Or, is it as simple as induction melt in ambient environment, pour casting, and end up with the exact same N content?

Phrased as a more relevant question: How would you get N out of steel (other than diluting with raw material that did not contain N.)

This is a difficult thing to search for.

 

[Metalhead97]

1gibson,

Yes you will lose some nitrogen. Nitrogen in solid solution will definitely outgas in a melt. In fact, I've heat treated nitrided surfaces, which resulted in a thin depletion layer near the surface. Nitrogen will also react with oxygen to form NO, which makes it more volatile. The fact is that nitrogen is metastable inside iron.

MH

 

[mk1979]

We already have an experience in how to add Nitrogen in stainless.Merely,we use ferromanganese bearing nitrogen during melting in open air induction furnace

 

[steelmtllrgst]

I have used the following:

FeCrN
FeMnN
Si3N4

Both the Cr and Mn methods show good and consistent recovery, Si3N4 is somewhat more variable.