Heating and cooling Rates-PWHT-P91

By baldassar Date 12-21-2009 09:51

We are welding A335 P91 and this grade needs PWHT, It is recommended that the heating and cooling rate are about 80°C/Hr.
My question is: what happens if this rate is more elevated (example: 150°C/hr) ?

Thanks very much for your replies!

By js55

Date 12-21-2009 16:03

You create through thickness temp gradients that can cause high stress and possible cracking. The idea is to homogenize the temp regime as much as possible.

By pgoswami (*)

Date 01-13-2010 20:56

Hi,

P-91 is not like regular grade of Cr-Mo alloy steels.The best properties of this steel comes in Normalized &Tempered grade. After fabrication one needs to do very dilligent PWHT, with a controlled rate of heating/cooling and a proper hold /soaking at the PWHT temperature.

Slower heating rate (80 deg C/hr) would ensure a though and comprehensive PWHT,without any thermal stress being generated during PWHT.Thermal stresses may cause cracking also. P-91 steel generates quite a bit of hardness in weld and HAZ, hence a controlled heating and cooling rate is required for proper PWHT.

There are many good guidelines on welding + PWHT of P-91 steel. Feel free to drop a line if you require more info.

Thanks

By welderbrent (*****)

Date 01-13-2010 20:59

Looks like we have two people here who need a big 'WELCOME TO THE AWS WELDING FORUM!!!'

Nothing creative to add to the thread, just wanted to let you know your participation is appreciated.

Hope you enjoy all the info and opportunity to network.

Have a Great Day, Brent