SUNDARAVAL, The other variable is the F number. If you have a ASME Sec. IX code book, review QW-356 Manual and Semiautomatic Gas Tungsten-Arc Welding Essential Variables for welding performance qualification. As you go down the list of variables, QW-404 .15 states a change in a F number as an essential variable. This means if a welder is qualified on P42 with a F42 filler electode, and he will be welding to parameters listed on a P44 procedure with a F44 electrode, the person is not qualified to weld P44 base material. A seperate test is required on P44 base metal using a F44 filler electode.