If you are working to D1.1, a tubular (round or square) that is connected to a flange by a CJP weld requires that the welder be qualified as 6GR.  Look at Table 4.10.  Don't forget to look at the notes, as depending on the details of the connection some additional restrictions may apply (for example, an acute angle heel qualification if the included groove angle falls below 30 degrees anywhere around the circumference of the joint, or a corner macroetch test for box tubulars).
Mankenberg