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J-Rod
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Join Date: Jan 2010
Location: Jamestown, North Dakota
Posts: 62
Good Answers: 1

PWHT of Welded P-91

01/12/2010 8:23 AM

Is there a critical time after which PWHT of welded P-91 will no avail the desired results? I have read that the time interval between completion welding and the start of PWHT is vital to the successful elimination of Heat affected Zone cracking. In some cases, radigraphy is required of pipe welds and repairs are best made before any PWHT. The maintenance of the interpass temperature may not be feasible for radiography. Do you have any advise for this case?

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Anonymous Poster
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Re: PWHT of P-91

01/12/2010 8:48 AM

As far as I am aware there is no maximum time (unless it is in years) after which the PWHT will not avail any result- the residual stresses unless released will self relieve and if not heated may create cracks (at the PWHT temperature the reduced Yield point helps in the grains to realign and reduce the stresses by plastic deformation)

However the P91 is prone for SCC (stress corrosion cracking) and in certain atmospheric condition- especially high humidity- it is advisable to do PWHT as quickly as possible after welding to avoid the ingress of the moisture in the hot metal and thus promote the SCC.

The PWHT of this material also has to be much more controlled.
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