Jorge,
We commonly weld on cast austenitic stainless steel valve and pump bodies for several of our customers. We are in the United States, but we ship casting to Europe, Canada, and even Argentina sometimes. I can't say for sure what the end uses are though.

Normally, ferrite is only an issue with weld cracking, but occasionaly, (10-20% of the time), our customer will specify that the weld metal must be within a certain ferrite range. Somtimes a certified material report from the filler metal manufacturer is adequate. Sometimes we have to test every weld we make with a Fisher Ferritiscope. We typically order our filler metal with a ferrite requirement on it. The catch comes when the filler metal manufacturer only tests their weld metal with a Magne-gage, and the customer specifies Ferritiscope, in which case we have to test the filler metal ourselves. We usually can return the material if it does not meet the ferrite requirement on our test, or just use the material on a job without ferrite specifications. All the ferrite specifications though, seem to be the customers internal standards, I have not seen, (which does not mean they aren't in use) industry standards. It is entirely possible that our customer takes their requirements from standards like NACE, or something similar.

As far as what we do if a tested weld does not meet the customer's ferrite requirements, we gouge it out and try again. Usually though, we can find a suspect source of contamination, (ie copper backing, carbon residue from gouging) that we can eliminate for a successful second try.

Hope this help

G Roberts

Often maximum ferrite contents are specified for certain applications. (e.g. In services where sigma phase embrittlement can occur, or in urea duties.)

Appart from the above, we typically measure ferrite (especially in the roots of pipeline welds) to ensure that the roots were in fact performed with an austenitic consumable. Here we would be looking to make sure that the ferrite content is not too high.

Regards
Niekie

The lower ferrite level is usually set to prevent hot cracking. If you get measurements below the specified minimum, you should check you weld metal for cracking, if the weld is clean there should not be a problem.