Base Metal Variable

By jmeador Date 12-08-2006 19:09

First posting.

I need some opinions on the interpretation.
Per AWS D1.1:2004 Table 4.6 item #1 states "A change in group number" SMAW, SAW, GMAW, FCAW, & GTAW.
As I understand it, if a procedure is qualified with impacts per contract / specification requirements and the base material qualified was for example group II to group II. Then only group II is qualified. Any other combination is not qualified.
Here is what I am not sure of since I get multiple opinions. If a procedure is qualified by welding group I to group II, and CVN's were tested in the following locations for group I side, weld, fusion line, fusion line + 2 mm,& fusion line + 5 mm. Then for the group II side, fusion line, fusion line +2 mm, and fusion line + 5 mm. Then are the following combinations also qualified per code along with group I to group II:
(1) Group I to Group I
(2) Group II to Group II

I say yes they are, but the third party inspector thinks otherwise, please help! I do not care if I am correct or not. I just want to know the correct answer. Thanks for your time.

Jeff

By CWI555

Date 12-12-2006 22:38

Going with whats required in the code is the only safe path. Even though you had group 1 & 2 in one weld, there is no guarantee that the tensiles, cvn's and the rest of the mechanicals will come up acceptable. There are to many variables (dilution percentages for instance will have an impact on the mechanical values) in a situation like that, I think to cover your butt I would follow your third parties advice.

By js55

Date 12-19-2006 21:16

I think it depends. If your talking about materials of differing tensiles strengths under the same spec, as for example A572 50/60/70, then dilution is not problematic. A weld metal, such as 7018 which overmatches the lesser BM strength will still do so no matter what the dilution from the greater BM. And the weld metal will also still bend as well or better than the greater BM, as long as it did so before of course. This is why Group designations under ASME are only Supplementary Essential Variables. And ASME is quite clear-unless it has just recently changed, I've been out of the loop a while-that this practice is acceptable. I think not unjustiifed. However, I cannot speak for the acceptability under AWS D1.1. However, if your Group to Group transition is based upon differing specifications and alloying concepts I think some metallurgical judgment is in order, and dilution could very well play a part. As for impact testing, the primary reasoning is that if you were successful with Group I to Group II, given the dilution from the Group II then you will most likely be successful in a Group I to Group I with no dilution from a higher alloyed material. Therefore, there may be greater concern for the Group II to Group II. But without being specific with your alloys thats the best I can do.