I need help with backing material for qualifying a WPS.

By Kix

Date 05-14-2007 18:03

I could of sworn i saw something about your backing material had to be the same material as that of your strongest plate for qualifying a WPS or for whatever application. I looked all over under backing and now i can't find it and i was wondering if someone could help. Example I'm quailfying a piece of A514 to a piece of A572 does the backing bar have to be A514 T-1 One more thing that maybe you guys can help me out on P.123 of d1.1 2006 4.7.3 base metal qualification it says steels listed in table 4.9 (A514)being one shal also qualify table 3.1 or table 4.9 steels in conformance to table 4.8. I'm haveing probs interpriting table 4.8 and was wondering if i qualify a test plate of 2 A514's does that save me from haveing to qualify table 3.1 steels with the same filler and from haveing to do any more procedures of table 3.1 steels to A514?
One more thing i promise!!! Does it say anywhere that you have to use the same tensile filler as the base metal you are welding on or is that just recomended.? We're using and 80 and 90psi wire on A514 t-1 that has a 100 to 130 ksi tensile range and i found that kind of od. Do you guys think the tensile pulls will come out using an 80psi wire?wp

By 803056

Date 05-18-2007 19:47

I believe you have to read a little deeper than you are. Table 4.8 uses the combinations of the groupings (of the steels) listed in Table 3.1 and/or the base metals listed in Table 4.9. Depending on the combination of groups, you may or may not have to do additional qualifications.

"if i qualify a test plate of 2 A514's"
Simply qualifying two plates of ASTM A514 doesn't automatically qualify you to weld any of the base metals listed in Table 3.1. Instead, it says that you can only weld base metals having the same specification (ASTM A514) and the same grade (or type), and the same minimum yield strength as listed in the PQR.

As for the backing material, usually the backing can be the same as either of the two "dissimilar" base metals being welded.

If you are qualifying the procedure, you can do what you wish provided the final results complies with the minimum requirements of the code. If you are using an undermatch filler metal, it stands to reason that the weld may not have a tensile strength or yield strength that is the same as the "stronger" base metal. This can work to your benefit in highly restrained joints where it is desirable to have a weld with lower strength, but better ductility to accommodate the contraction that will take place as the weld and surrounding base metals cools to room temperature. I've used this technique for maintenace welding of large casting. However, I usually limit the reduction in tensile strength of the filler metal to 10,000 psi so as not to produce a weld that is "very" under strength compared to the base metal being welded. The published tensile strengths of the filler metal (per the AWS/ASME filler metal specification) are typically lower than the actual tensile strength produced by the weld.

Good luck - Al

By Kix

Date 05-21-2007 13:00

Here's the info on the use of backing if anyone ever needs it. 5.2.2.2 on page 189 of D1.1 2006