Reg. post heating for low alloy steels

[Prasu Cutie]

Dear experts,
We are going to start pqr for low alloy steels i.e. A335 Gr P11, P22, P5, P91 etc, it suppose to be post weld heat treated immediately  after welding. As per literature if pwht is not possible immediately  after welding, intermediate PWHT recommende .i.e pos heating.
Now the question is is there any code reference for the same? What is the heating time n temp???
The codes we r following  here are shell dep's n asme b 31.3
Project: refinery

Awaiting for your reply

Thanks n regards
Prasad
0096594122634

[Kannayeram Gnanapandithan]

U should not take it immediately for P91, it has to cool down below 100deg

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[pgoswami]

What‘re thickness involved. You’ve to respect the materials engineering requirements, otherwise pay the price. For example  it’s not advisable  to weld P-91 steel without any provision for immediate PWHT. Better try when you’re ready with PWHT facilities.

 

You may delay PWHT for the other grade by adopting Post Heating or DHT, but may not have much luck with Garde-91 steel.

 

For P-91 a DHT @ 300-350 Deg C / 4 hrs is recommended as an alternative. Mind you NON-heat treated hardness of grade-91 steel would be easily over 350 HV, hence any impact loading, rough handling could crack the welds. Hence sooner the PWHT done, it’s better.

 

Also note DHT for grade -91 steel must be done after cooling the steel to room temperature for the whole martensitic transformation to occur. DHT should follow next. Without this the creep properties would be bad.

 

It’s better to know the full details first.

 

Shell DEP’s are exhaustive , read thoroughly & you’ll have the answer.

 

 

Thanks.

 

Pradip Goswami, P.Eng,IWE
Independent Welding & Metallurgical Engineering Specialist ,

Ontario,Canada.
ca.linkedin.com/pub/pradip-goswami/5/985/299

pgos...@quickclic.net

pradip....@gmail.com

 

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[George Dilintas]

Correct me if I am wrong nut martensitic transformation occurs in the range of 800 to 400 degC

2016-08-07 6:41 GMT+03:00 pgoswami <pgos...@quickclic.net>:

What‘re thickness involved. You’ve to respect the materials engineering requirements, otherwise pay the price. For example  it’s not advisable  to weld P-91 steel without any provision for immediate PWHT. Better try when you’re ready with PWHT facilities.

 

You may delay PWHT for the other grade by adopting Post Heating or DHT, but may not have much luck with Garde-91 steel.

 

For P-91 a DHT @ 300-350 Deg C / 4 hrs is recommended as an alternative. Mind you NON-heat treated hardness of grade-91 steel would be easily over 350 HV, hence any impact loading, rough handling could crack the welds. Hence sooner the PWHT done, it’s better.

 

Also note DHT for grade -91 steel must be done after cooling the steel to room temperature for the whole martensitic transformation to occur. DHT should follow next. Without this the creep properties would be bad.

 

It’s better to know the full details first.

 

Shell DEP’s are exhaustive , read thoroughly & you’ll have the answer.

 

 

Thanks.

 

Pradip Goswami, P.Eng,IWE
Independent Welding & Metallurgical Engineering Specialist ,

Ontario,Canada.
ca.linkedin.com/pub/pradip-goswami/5/985/299

pgos...@quickclic.net

pradip....@gmail.com

 

From: materials-welding@googlegroups.com [mailto:materials-welding@googlegroups.com] On Behalf Of Prasu Cutie
Sent: Saturday, August 06, 2016 10:33 PM
To: materials-welding@googlegroups.com
Subject: [MW:25208] Reg. post heating for low alloy steels

 

Dear experts,
We are going to start pqr for low alloy steels i.e. A335 Gr P11, P22, P5, P91 etc, it suppose to be post weld heat treated immediately  after welding. As per literature if pwht is not possible immediately  after welding, intermediate PWHT recommende .i.e pos heating.
Now the question is is there any code reference for the same? What is the heating time n temp???
The codes we r following  here are shell dep's n asme b 31.3
Project: refinery

Awaiting for your reply

Thanks n regards
Prasad
0096594122634

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Dr. Georgios Dilintas,

Dipl. Ing. In Aeronautic and Space Engineering

Ph.D in Mechanics of Solids - Computational Mechanics

A.I.S, A.N.I, IRCA Lead Auditor

Welding, Stress Analysis, Corrosion, QA/QC, Failure Analysis, Risk Analysis

[George Dilintas]

In the BPVC ASME Section IX there is a variable "Preheat Maintenance". This is the variable which applies in your case. It is up to you do define the value. The issue is that this variable is a supplementary essential one, i.e when impact test is required, then the PQR has to be qualified with this variable. If the value of temperature is reduced then a new PQR is necessary.

PWHT is possible after welding if you dont remove insulation and you raise the temperature as per B31.3 requirements 331.1.4

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[Kannayeram Gnanapandithan]

Preheat maintenance is slightly different from post heating( dehydration, hydrogen bake out). Preheat maintenance is a non essential variable. Post heating is generally good for lowalloy/Cr-Mo steel to avoid HICC.

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[Kannayeram Gnanapandithan]

Starts at around 400 and finish around 120

On 07-Aug-2016 3:40 pm, "George Dilintas" <dili...@gmail.com> wrote:

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[untraceablenator]

Dear Prasad,

You can refer to the series of API 934 A or API 934 B or API 934 C., E, & G.

& refer to the clause on "Intermediate Stress Relief/ Dehydrogenation Heat Treatment".

These are standards for pressure vessels.

Regards

MK

[veloumany siva]

Dear Prasad,

As  per the SHELL DEP 31.22.11.32 Appendix C, please find below the post heating requirement

If, for fabrication reasons, the final required heat treatment is not performed directly

after welding, a post-weld soaking heat treatment shall be performed at a temperature

of 350 °C for 3 hours, without cooling down below the preheat temperature, prior to

cooling down to ambient temperature.

The DEP's 31.22.11.32,31.22.20.31 ,31.22.10.32 also applicable for equipment and piping.

Please read the DEPs carefully.

best regards,

veloumany

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From: Prasu Cutie <pra...@gmail.com>
To: material...@googlegroups.com
Sent: Sunday, August 7, 2016 5:33 AM

Subject: [MW:25208] Reg. post heating for low alloy steels

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[George Dilintas]

correct it is not the same, but the only way to handle post heating in the frame of the ASME Code is to handle it as preheat maintenance. Remember that it is a supplementary essential variable

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[Kannayeram Gnanapandithan]

Mr lintas , preheat maintenance is a non essential variable as per QW 250

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