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What are Nitrogen binding elements in steel ?

 
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Natacha_Segeivna
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Joined: 10 Sep 2017
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PostPosted: Sun Sep 10, 2017 10:07 am    Post subject: What are Nitrogen binding elements in steel ? Reply with quote

Hello to everyone.
I hope you are well.

I am actually working with steel rebar, under standard BS4449:2005. There are chemical specification, mentioning that nitrogen should not have higher levels than 0.014% of mass.

Furthermore, Nitrogen is the only chemical compound on which it is said that : "Higher Nitrogen contents are permissible if sufficient quantities of nitrogen binding elements are present".

The problem is that nothing more is said concerning this last sentence. Despite many search on the internet, i did not find any hint concerning these binding elements, and on what extent they do allow higher nitrogen contents.

Also, when chemical testing is done on the product, i was wondering if it is total Nitrogen content that is being measured, or just free Nitrogen.

I would be grateful if you could help me on these questions, and give me a clearer view concerning the Nitrogen issue in this standard.

Kind regards,
Natacha.
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kunalkansara
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Joined: 26 Jan 2003
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PostPosted: Tue Oct 17, 2017 5:38 pm    Post subject: Reply with quote

Dear Er Natacha

Not sure what exactly you need this information for. I understand as of now the clarification on this clause is pending. But in general if the following two conditions are met with, it can be assumed that the Nitrogen binding elements are sufficient in quantity:

(N 0.012) < (1/7)*V
AND
Total N <0.025%

Where N and V are the amount of Nitrogen and Vanadium by mass in percentage.

Im not entirely sure on why only the nitride of Vanadium are used for the benchmarking despite the possibility for steel to have nitrides of a range of alloying elements in the soluble interstitial. Probably a steel material scientist can answer this more competently. I am not a material scientist!

Hope this is useful.

Thanks
Kunal
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spsvasan
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Joined: 18 Dec 2008
Posts: 289

PostPosted: Thu Oct 19, 2017 4:04 am    Post subject: Reply with quote

kunalkansara wrote:
Dear Er Natacha

Not sure what exactly you need this information for. I understand as of now the clarification on this clause is pending. But in general if the following two conditions are met with, it can be assumed that the Nitrogen binding elements are sufficient in quantity:

(N 0.012) < (1/7)*V
AND
Total N <0.025%

Where N and V are the amount of Nitrogen and Vanadium by mass in percentage.

Im not entirely sure on why only the nitride of Vanadium are used for the benchmarking despite the possibility for steel to have nitrides of a range of alloying elements in the soluble interstitial. Probably a steel material scientist can answer this more competently. I am not a material scientist!

Hope this is useful.
Thanks
Kunal


Dear Er.Natacha

I am attaching a technical note from the Standing Committee on Concrete Technology, Hong Kong on the nitrogen binding requirement. This is very similar to Dr.Kunal Kansara's post

I am not aware of the technical background of this information

S.P.Srinivasan



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SCCT Technical Note No 3.zip
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