Take a look at the notes below Table 3.1, Approved Base Metals for Prequalified WPS's.....
1. In joints involving base metals of different groups, either of the following filler metals may be used: (1) that which matches the higher strength base
metal, or (2) that which matches the lower strength base metal and produces a low-hydrogen deposit. Preheating shall be in conformance with the
requirements applicable to the higher strength group.