[MW:8284] MW: 8258- How to control cracks when weld P91 and P91

Hello Liu,

 

I've attached some information on recommended welding consumables and welding parameters for P-91 steel. Being the products of Metrode certainly these products are very well known in the welding world.

 

The typical formula for heat input as per Sec-IX is = 

  =380X35X60 / 25=3192 J/mm =3.2 KJ/mm

 

The heat input looks to be  at least 25-50% higher than the optimum level 2-2-5. KJ/mm. This may be controlled by increasing the travel speed. SAW welds produces wider HAZ, as compared to SMAW or GTAW. Impact properties for SAW welds are relatively less than GTAW -P-91 weld metal One of the possible causes for reduced impact strength could be higher "Si" in the weld metal and relatively higher input in SAW

 

As regarding PWHT-- all welds in utility (power plant) services would require PWHT at 760°C ± 14°C (1400°F ± 25°F) minimum, regardless of wall thickness or diameter.

 

Te preheat and interpass temperature looks fine.The recommendations  would be :-

 

Controlling Cracks:-For controlling cold cracks, maintain the preheat, interpass control,immediate cooling to 100deg C for complete martensitic transformation as below. Hot cracks could be controlled through a strict control of:C" and 'Si" in the weld.

 

As regarding PWHT:- Ensure the PWHT temperature does not exceed the base metal tempering temperature and stays in the above mentioned temperature range. In fact it would be advisable to work out the best welding parameters after verifying the base metal CMTR(especially impact)

 

Thanks.

 

 

Pradip Goswami,P.Eng.

Welding & Metallurgical Specialist & Consultant

Email-pgoswami@sympatico.ca,

pgoswami@quickclic.net

 

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From: materials-welding@googlegroups.com [mailto:materials-welding@googlegroups.com] On Behalf Of Roy LIU??
Sent: Sunday, November 14, 2010 7:30 AM
To: materials-welding@googlegroups.com
Subject: [MW:8258] How to control cracks when weld P91 and P91

Dear All,
I just meet a problem from one of my customers.
It is a Boiler Manufactory in China.
 
Details as follow:
base material: P91
process: SMAW (root) + SAW (filler metals)
Heat Input: high  
I=380A
U=35V
V=250mm/min
Preheat, Interpass Temperature: ≤250℃
 
How to control cracks?
How to increase impact properties afer PWHT?

 

Best regards

 

Roy LIU

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