I believe there's a technique called "replica" : it produces an image of the metal structure. Normally this technique is used to measure grain growth of the material after PWHT.

Maybe you should contact a metallurgical engineer and discuss this. Forged materials have a different grain structure. Maybe it is possible to detect the type of grain structure on a replica to know if it is a forged material or not. But, I am not a specialist on this topic. I have only seen it once for grain growth detection in materials.

Can you contact the nozzle manufacturer and find out what process was used? Usually you can tell how a part was produced by looking at the surface of the part. If it was machined from a billet then you would see machining marks unless the forging had subsequent operations performed to it.

I'd start by clearing up that a "nozzle" consists of a pice of pipe (which in this case isn't important), welded to a flange, which is causing Raphael's concern. The nozzle is usually made by the vessel fabricator as part of his job. .
ASTM Standard A105 covers only FORGED material, so any flange or pipe fitting made to ASTM A105 MUST be forged, and not rolled or cast.
If I were Raphael I'd proceed like this.
1st. Require the vessel fabricator to furnish him a copy of the flange material certificate, which the flange manufacturer is obliged to furnish on request. If the vessel fabricator isn't able to furnish the certificate, put the blame on him. He'll have to change all the flanges at no cost for Raphael.
2nd. If the vessel fabricator does furnish the flange certificate saying that the material is ASTM A105 steel, show it to the client and ask him to take it easy. The chances that the flange manufacturer issues a false certificate for which he assumes liability are remote. He can be taken before a court if the certificate is false.
3rd. If after this the client insists in making a destructive test, warn him that if the test result is in Raphael's favor, i.e., the material is forged, then the client will have to bear all the consequences, among which:
a) cost of the test itself, charged by the laboratory
b) Raphael's cost to send the material for testing in the lab
c) justified delay in the delivery date
d) etc.
Giovanni S. Crisi
Sao Paulo - Brazil

Around 1992 there was a big investigation by the National Board of Boiler & Pressure Vessel Inspectors here in the U.S. due to an inservice failure of a flange that was supposed to be A105. It was stamped A105 and made in China. It turned out to be fabricated from plate and was cleverly welded and machined so that it would not be obvious. The material test reports also certified it as meeting A105.

I suppose either the client purchasing this vessel is concerned about a similar situation or saw something on the nozzles that led them to believe they were not forged. As a fabricator, one may have purchased such flanges unknowingly. You may need to contact a competant metallurgist in your area to either perform field metallography (surface replica) or send one of the flanges to their lab for analysis.

Hope this helps,
Marty

Additional info on field metallography process:

ASTM Designation E1351 "Standard Practice for production and Evaluation of Field Metallographic Replicas" gives details of the replication technique. You can purchase a copy of ASTM E1351 via the ASTM website at http://www.astm.org .

You can also learn about the technique by reading
http://www.metallography.com/bboard/messages/1998/1064.html
http://www.metallography.com/bboard/messages/1998/1193.html
http://www.metallography.com/bboard/messages/1998/1355.html
http://www.metallography.com/bboard/messages/1998/860.html
http://www.metallography.com/bboard/messages/1997/302.html

Prior to applying the acetate tape, a small area about 1" x 2" will need to be polished using progressively finer grits of abrasive wheels from 80 grit to 600 or 800 grit, then final polish with 1 micron diamond paste. It's not a technique easily achieved by reading the ASTM standard. You will need some practice and training.

Buehler (http://www.buehlerltd.com ) has a "Replicating Kit" code 57-5002, for $13.
Struers (http://www.struers.com) also makes a replica kit called "Transcopy" which includes green colored acetate tape with an aluminum coated backing.

All this information was found by searching the Archives at http://www.metallography.com/bboard/search.html using the keywords: acetate, replicas, and replicate.