I would say, yes, it probably (most likely) is possible to qualify two welders in this case, as long as each welder always did the same part of the process, with the same equipment, and to the same procedure. After all, you are supposedly testing the quality of the weld and process as it well always be done, and in its completed form. Ask the people who wrote the spec. you are working to, and also ask AWS. The AWS answer that gtaw quoted is for a much different situation. And, AWS said “No” because one test might be from either welder, but not both in the same sample piece. Thus, we don’t know which welder was qualified by that single test, at least one of them wasn’t tested.