I have welded the grades 60/70 with .045 E71 - T1 the ESAB dual shield 7000 series. Actually qualified at -20 with a heat input of 345 KJ/inch as welded. Yes you read that right 345. Had to set the root opening to about 1" with backing to get that slow of a progression in vertical. WFS of around 275-300 at 27 volts using C-15 gas.

The typical heat input range is 75-90 KJ but I was trying to prove a point that heat input is a relatively moot point on this steel.