Phosphorous (P) is one of the elements that lowers grain boundary cohesion. If it migrates or accumulates on the grain boundaries it can lead to cracking. In the Cr-Mo alloys, P has been found by several investigators , to have a profound effect on susceptibility to reheat or PWHT cracking. The deleterious nature of P on temper embrittlement can be seen by the inclusion in the empirical equations J and X-bar used to evaluate sensitivity of steels to this problem. {J = (Si + Mn)(P + Sn) x 104 and X-bar = (10P + 5Sb + 4Sn + As)/100}
As far as I know, there is no single fixed value of P beyond which is unacceptable. Typically the effects are the result of combination of elements, see equations above.
Regarding reheat cracking susceptibility you might want to look for articles by Japanese researcher K. Tamaki.
Hope this helps.
John
From: materials-welding@googlegroups.com [mailto:materials-welding@googlegroups.com] On Behalf Of Sachin.Shelar1@thermaxindia.com
Sent: Thursday, July 07, 2011 12:01 AM
To: materials-welding@googlegroups.com
Subject: [MW:11609] Phosphorus content in Material composition
Importance: High
I would like to know what is the effect of Phosphorus content in material composition. How do we control phosphorus content if there is a specific requirement ( Is there any method). How much in % effect of Phosphorus content will affect the grain structure(any curves). Is there any specific requirement in NACE MR0175 &103 for % of Phosphorus content in material composition. Please specify references.
Thanking You.
Regards
Sachin Shelar
Sr. Engineer - Process Engg
Thermax Ltd.
Ph +91 20 66126775
E Mail: sachin.shelar1@thermaxindia.com================================================================================================================
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