ferrite FN range for SS

[matweld1]

I would like to know when I have a SS ASTM A312 TP316 at low temperature service (-160ºC ) what is the range of the FN for the metal deposit?

 

[metengr]

For 316L stainless steel weld deposit, the minimum ferrite content to prevent hot cracking is typically 3-5 FN. I do have data at -492 deg F that shows for a range of ferrite numbers of 0.1-10.1, the fracture toughness is

162 Ksi sq rt for 0.1 FN
161 " " for 0.8 FN
128 " " for 4.1 FN
98 " " for 8.5 FN
90 " " for 10.1 FN

for 316L SS SMAW welds.

 

[stanweld]

We have easily met the 15 mils, lateral expansion, weld metal requirement per ASME Section VIII and B31.3 at -320 F in Charpy V-notch testing with ferrite content as high as 11% using the GTAW process and as high as 8.5% using the SMAW process and E316-15 electrodes. Unless otherwise specified by the Owner or Engineer for ore stringent ferrite control, we specify purchasing ER316/ER316L with maximum ferrite content of 2-10% and E316/E316L-15 electrodes with a maximum ferrite content of 2-8% to assure meeting the above requirements.

 

[EdStainless]

Stan,
What CVN values do you get?
Lat exp is one thing, toughness is another.

In general I fully agree with you. 316 is very forgiving. Our autogenously welded tubing usually has 5-10% ferrite in the as welded condition and I have seen it pass cryo test criteria. This testing was done just for information.
Everything that we sell is annealed, so it is only an issue with field welds.
I know of one customer of ours that uses a 6% limit, but I have no idea how they arrived at that number.

= = = = = = = = = = = = = = = = = = = =
Corrosion, every where, all the time.
Manage it or it will manage you.

http://www.trent-tube.com/contact/Tech_Assist.cfm

 

[stanweld]

EdStainless
27 to 35 ft-lbs with the E316L-15 with 9.2% ferrite content. We too have had one Customer require 6% max ferrite as a filler metal control. We have had a number of Customers require 8% max. ferrite.

 

[matweld1]

Thanks for all
I would like to know if we have to do PWHT if we have a value under the range required:
Heat exchange for low temperature service, we find in different joint the FN<3.

 

[metengr]

No. The ferrite content reduces susceptibility to hot cracking in an austenitic stainless steel weld deposit. If you have no hot cracking at a lower ferrite number you are acceptable for use at low temperature service.

 

[matweld1]

my tube is 7.5mm WT, how could be sure that I have no hot cracking becaause of the lowest FN or how could be the right NDE to control my weld joint?

 

[metengr]

matweld1;
Your post is starting to become confusing. In general, for welding of austenitic materials, a minimum ferrite content is specified to reduce susceptibility to hot cracking. If you fall below the minimum specified, hot cracking can occur and it does not necessarily imply that hot cracking will occur.

To assure a defect free weld deposit, yes, NDT should be performed.