Re: [MW:7413] Post Heating for Alloy Steel

Hydrogen embrittlement occurs when the weldment temperature is below 300 C not close to ambient temperature.

 

br,

msms

On Wed, Oct 6, 2010 at 7:35 PM, Jignesh Desai <jignesh.desai.met@gmail.com> wrote:

In ferritic steels, hydrogen embrittlement only occurs at temperatures close to the ambient temperature. Therefore, it is possible to avoid cracking in a susceptible microstructure by diffusing hydrogen from the welded area before it cools. After welding has been completed, the steel must not be allowed to cool to room temperature; instead, it should be immediately heated from the interpass temperature to the post heat temperature and held at this temperature for some minimum amount of time.

Also did you see UOP Spec 8-12-6, para 2.4(a) - Fabrication of piping?, where UOP asked for post heating of carbon steel? It may be carried out for some case of CS where thickness>50.0 mm). I am sure this spec. must be part of your project.

On Wed, Oct 6, 2010 at 11:47 AM, muthusrinivasan muthuselvam <msms2k@gmail.com> wrote:

Mr.Senthil..

 

The main purpose of doing immediate PWHT without post heating is to avoid hydrogen induced cracking.. To my knowledge there is no code requirement or specification mentioning about the time after which you can do the PWHT.

 

But please note that delaying the PWHT after welding will improve the condition for hydrogen induced cold cracking. So the PWHT has to be carrried out immediately after completion of welding.

 

best regards,

 

M.S.Muthu selvam.

On Tue, Oct 5, 2010 at 10:42 PM, senthil raja <senthilrajabarathi@gmail.com> wrote:

Hi,

 I m Senthil working in L&T. I m presently in MRPL project,
Mangalore. In our client(EIL) specification it is given that post
heating shall be carried out for the alloy steels (Cr-Mo) where PWHT
cannot be carried out immediately.

I need to know what is the time limit within which PWHT shall be
carried out without post heating. What is the standard or code which
can be reffered for this.

Kindly share your experience sirs & friends,



regards,
Senthil Raja.

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