347H with 4 hour PWHT

Date 12-08-2005 15:34

I need to run a PQR for 347H plate (groove weld) using GTAW process. The customer requires a 1600 F PWHT for 4 hours to "prevent sensitization, a condition necessary for PTA-SCC." I'm looking for confirmation as to which consumable to use. I'm thinking ER347. The C content of the 347H plate is .04-.10; C for 347 bare wire is .08 max. Seems like I'd be OK there. Any thoughts re: a different consumable, etc?

By goodyr1 Date 12-08-2005 21:43

I agree that the ER347 is the filler metal of choice in this case. Since 347 GTAW filler metal can have a max. carbon limit of 0.08%, I would request that your wire supplier check the certs and give you the lot with the highest carbon percentages. The higher the C limit, the higher % of stabilizing elements you will have. (10 X C minimum/1.0 max).

By kedawhit (*)

Date 12-15-2005 17:19

Thanks for the response.

By jon20013 (*****)

Date 12-29-2005 14:29

goodyr1; I am in a similar quandry. I am required to perform ss clad overlay of carbon steel plate material which will then be subjected to hot forming at 1800F and subsequently allowed to air cool. Due to the thickness of the carbon steel (3.25") it will take a long time to cool while passing directly through the sensitization range. Initially we had planned a 309L/308L cladding but now determined this will not work with our planned approach.

Would 321 or 347 be a better choice given the above circumstances???

By - Date 12-29-2005 16:08

Depending on the time at temperature, you should also be aware of the possibility of sigma in conjunction with sensitization. Naturally, a stabilized filler metal such as a 347 will prolong the onset of both. Maybe cladding after the hot forming can be considered. Like you said, a 3.25" thick metal will remain in the sigma range if the time is adequate. If this is held for around 4 hours, it is likely sigma will form, and almost definitely sensitization.

By jon20013 (*****)

Date 12-29-2005 16:34

Thanks Chuck, you are truly one of the greatest! It's funny, our field never leaves me much time free from studying, and I've studied this topic more in the past week than the entirety of my 33 years in the welding field...

Education being a wonderful thing, is only disappointing when one finally realizes that there is a need for further education, one seldom has time to assimilate his/her newly acquired knowledge adequately to answer the proposed problem.

What a great thing this forum is to have experts from all areas of welding. Your input is deeply appreciated!