According to my copy of B31.3, which is only 2004 ed, Section 3 Table 323.2.2 if the material is listed in curves C & D no impact testing is required if you are using impact tested consumables according to AWS. The problem is A333 grade 6 is not assigned to a curve in Table A1 only a temperature. As this temperature is more onerous than curve D, could I argue it’s curve D and escape impact testing by using impact tested consumables.
In my A-1 Table, Grade 6 is listed at -50 deg F. No impact testing is required for base metal. Per Table 323.2.2A, impact testing is required for the weld and heat affected zone unless exempted by Notes 3 and 5.