ASME has provisions where the PQR coupon weld deposited with different filler metal F numbers or different welding processes can be recorded. The WPS thickness range is then qualified based on the thickness of the weld deposited with each welding process or F number.
That isn't the case with AWS. There are no provisions to record the deposited thickness for each F number or welding process. The thickness range of the WPS is based on the thickness of the base metal used for the PQR coupon. Therefore, it stands to reason, forgetting the philosophy of other welding standards, that only one filler metal F number or one welding process can be used to qualify the WPS.
There are provisions for the production WPS to include supporting PQRs and a prequalified WPS to expand the applications. For instance, I can qualify a WPS to weld an open root joint with GTAW. I can then write a WPS that includes a supporting PQR to permit welding the open root joint with GTAW and fill the remaining groove with SMAW using E7024 as long as the production welding is performed in the flat position. If I need to perform the production weld the overhead, I can revise the WPS to include E7018 for overhead and vertical, but I am still locked into using GTAW for the open root portion provided the PQR was welding in the required positions.
In the case cited above, the question was whether the WPS that included welding the root (assumed) with 6010 could permit the use of 7018 (I assume the post is looking to use 7018 for the open root). That would not be permitted because 6010 and 7018 have different F numbers. Thus the PQR using 6010 is fine, but it doesn't permit the use of 7018 in its stead.
Granted, I am reading between the lines because the post leave a lot of details out and I am making a number of assumptions that may or may not be correct. For instance, the PQR could included alternate weld beads deposited with 6010 and 7018. The PQR could have been welded with a wide root and backing such that both 6010 and 7018 could have been deposited in the root layer. While that practice is feasible following ASME Section IX, it is unlikely following AWS D1.1 Structural Welding Code / Steel. Another assumption is that the post actually is asking a question about a AWS welding standard since it is posted under AWS, but we know from experience that is far from how things really work around here.
By the way, how is life treating you these days. I have some snow I would love to share with you. Your wife would love it. I remember years ago I drove from New England to Mississippi right after a New England snow storm. I drove straight through. I checked into a hotel, showered, shaved, and headed out to get a bite to eat. Low and behold, there where two housekeepers in the bed of my pickup truck throwing snow at each other and having a ball. I didn't know whether to ask them to get out of the truck or leave them to their fun and games!
Best regards - Al