Ferrite content for SS316L

By rodofgod (**)

Date 06-02-2004 03:18

Hi!

As I understand it, the level of Ferritic in S/S (316L) weldments to aim for is around 5%.

Regards

By GRoberts (***)

Date 06-02-2004 04:17

The optimum ferrite greatly depends on the type of service. If at elevated or cold temperatures, low ferrite is desirable. High ferrite can help resist Stress corrosion cracking in marginal situations. You need to find out what is desirable for your particular situation, as there will be no general answer applicable to all situations. The 5% ferrite mentioned in the post by rodofgod is a ballpark figure for weldability (hot cracking resistance), not necessarily corrosion resistance. To resist hot cracking, the weld metal needs to solidify as primary Ferrite instead of primary austenite. (See the 1992 WRC diagram)

By swnorris (****)

Date 06-02-2004 21:08

Here's a link to NRC Guide 1.31 Control of Ferrite Content in Stainless Steel Weld Metal that may be helpful:

http://www.nrc.gov/reading-rm/doc-collections/reg-guides/power-reactors/active/01-031/

It includes verbage which it says has been extracted from a future edition of the AWS "Specification for Corrosion-Resisting Chromium and Chromium-Nickel Steel Covered Welding Electrodes," which the AWS plans to publish as AWS A5.4-78.4. It describes a procedure for weld pad preparation and ferrite measurement of covered electrode deposits. I don't know whether this is a current publication or it's still in the planning stages.

Here's a few more related links:

"Considerations for the Weldability of Types 304L and 316L Stainless Steels"

http://sti.srs.gov/fulltext/ms2001544/ms2001544.html

"Improved Ferrite Number Prediction that Accounts for Cooling Rate Effects"

http://www.ornl.gov/~webworks/cppr/y2001/pres/113776.pdf

"Improved Models for Predicting Ferrite Content in Stainless Steel Welds"

http://www.ornl.gov/~webworks/cppr/y2001/pres/113800.pdf