I have a project that I am working on where we need to weld some high tensile strength, high toughness material to a pipe.  It's basically a large flange that will see high stress at the lip.
The dimensions of the flange are 24" OD x 1.50" thick x 6" tall (long).  The flange will be welded to a 24" OD x 1.50" wall ASTM A106 Gr.70 pipe.

The material that I am considering is 4320, normalized, quenched and tempered at 900 deg F to bring the toughness up.
I was thinking of using LA-75 Wire with 880 flux and sub-arc welding the parts on a turn-table or using 81Ni1A75-H FCAW-G wire 1/16".

I have not yet bought the material, so I am throwing this out there to see what you all think about welding on the Q&T steel.  I don't have experience with this, so I am hoping to get some feedback here.  I can't heat treat after welding, the best we can do is flame heat the part to xxxx Deg. and blanket cool.

As an alternative I can also use AISI 3310 (similiar to 9310) steel, which has less Carbon, more nickel.  I may be able to get away with using this material in the normalized condition.

Thoughts?