We have weld requiring impact testing and will be done between dissimilar base metal thicknesses. The thickness on one of the base metals is 12mm and the other is 45mm, P3 gr. 3 material, SMAW. If I need to simulate this exact scenario in the PQR, using test coupons one 12mm and the other 45mm thick, my base metal ranges according to ASME IX and QW 403.6 , QW202.4(b) and QW403.8 if I understand correctly will be from 12 to 24 for the thinner member and from 16 to unlimited for the thicker member. We will do impact testing on both sides of the HAZ. The weld metal thickness will also be limited to 24mm.
Can I use this same PQR to weld base metals both with a thickness of 12 mm?
Or should I rather do two PQR's one with coupon thickness of 12mm and the other 38mm and the use them to support the WPS?
Cheers
Joe
qw200.2(f) multiple WPS's with One PQR/Multiple PQRs with One WPS. It gives an example of the situation your in. At the bottom of QW202.4 "More than one procedure qualification may be required to qualify for some dissimilar thicknesses"
QW451 10 to 19mm qualifys for 5mm and assuming you test with 12mm to 24mm or a 19mm which brings you to 38mm You then go to your >38/45mm.
I believe you are required to have 2 PQR's but under the provision of qw200.2f you can use them to create 1 WPS.
Joe, unless I'm mistaken, ASME IX doesn't impose rules for impact testing but rather defers to the constructing code. Which code is it you're building to?
I don't remember Section IX being very definative on this point, and this is strictly from memory, wish I had one in front of me. I think from a practical standpoint whenever you are confronted with these types of situations (code gray areas), if you anticipate this as a limited application and you and your customers engineer can agree that the impact properties are accurately represented, then you might possibly achieve your end with a single qual. But if you anticipate this will be an ongoing application it would most likely be more practical to just go ahead and perform two in order to eliminate any future controversies. You can also write to ASME and have your situation interpreted, which they do quarterly at Code Week. Although, if the code does not address the situation specifically that is the response you will get.
By JdB
Date 02-21-2007 04:09
We are building to ASME VIII. I think it will be best to do two PQR; it will definitely help preventing future controversies.
Cheers
Joe
Joe, ASME Codes (in general terms) do not require impact testing for materials less than 15.8mm thick. Does your specification require impacts for all thicknesses of materials? If not, I would say there's no need to perform impacts on the 12mm side. If your specification does require impact testing for all material thickness, it should provide criteria for those materials less than 15.8mm thick.
Jon makes a very good point on the thickness issue. Metallurgically the fracture mechanism changes with greater thickness. The code body limtiation reflects this phenomena. The thicker the material the more 'brittle' the fracture. Something to do with thickness/triaxial restraint, or somethin or other, its been a long time. Without retraint you have a more ductile fracture. In any case, if your specs do call for impacts on all thicknesses I would sure be interested to hear their rationale. and also how you would actually represent the thinner materials. The codes do accomodate reduced specimens, but there is a practical limit.
If both sides of the joint are the same P No./Gr No., I don't see why you can't do the one PQR with 12mm and 45mm thick plate and get a qualification range of base metal from 12mm to unlimited. However, since the weld would be 12mm thick, I think your "t" (weld metal thickness) would be limited to 24mm (as you state). If you need to weld thicker materials later, then you will have to do another PQR. When needing 8" thickness on welds and base metals, you can also do 38mm plate with a 3/4" PJP weld, and that does cut down on the amount of welding required.
Greg, I've debated this issue with code people before; since "most" of the ASME Codes begin notch toughness requirements at 5/8" or greater, where do you find criteria for materials less than 5/8"?
Our requirement come from an owner requirement that impact testing will be done below a certain temperature.
Thank you for pointing out the 15.8mm thickness limit for impact testing requirements. However I always thought that the bottom thickness limit was 2.5mm as per UG-84(c) 3. Also if you look at fig UCS-66, if I understand correctly, impact test is require even for the lower thickness when the design temperature and thickness lay below the relevant cure. For example SA516 gr 70 not normalized requires impact testing for a design temperature of -30°C and 10mm thickness. Obviously I am missing something, will you please explain?
Thank you
Joe
Joe, you're right. Sorry I didn't have my response focused on Section VIII. I can tell you that in ASME IX, there is a Supplementary Essential Variable; QW-403.6 which limits base metal thickness to 5/8" when impacts are required however if the test coupon is less than 1/4" (6mm) the minimum qualified thickness is 1/2T. In any case, the acceptance criteria for impacts are to be in accordance with the Code Section specifying impact requirements. Once again, sorry for the previous knee-jerk response. ASME VIII is apparently where you'll find your requirements and acceptance criteria.
Most of the requirements I get like that come from customer specifications.
