I insist. ASME IX covers all of pressure piping except oil and gas pipelines (which are also pressure piping), that are covered by API 1004.
AWS D1.1 is intended for structural steel, API 1104 is intended for oil and gas pipelines and ASME IX is intended for vessels, either atmospheric (API 650, for example) or pressure (ASME I -boilers- and VIII -unfired-) and piping other than oil and gas pipelines. Therefore, each standard looks at qualification from a different standpoint.
A welder qualified under API 1104 IS NOT automatically qualified to weld pressure vessels nor structural steel, same as a welder qualified under AWS D1.1 IS NOT automatically qualified to weld pressure vessels.
Of course, good engineering sense must govern in all circumstances. Back in my days of erector engineer I'd been in charge of the construction of a natural gas compressing station in a remote location of Argentina (South America), 75 miles away from the nearest town. All of the welders were qualified by API 1104. When it came to make a few welds on the compressor building structural steel and weld the pipe supports, the client and the contractor (me) agreed to let our API 1104 qualified welders to do the job.
By the way, all of the standards we're talking about are not available for download on the internet, they must be bought from the editors (and they're rather expensive)
Giovanni S. Crisi