steel weld filler and process with extremely machinability

[dtimberlake]

We have some 6000 lb A27 Grade 60-30. 5-7" thick. They have some defects less than .5" deep that are excavated and then weld repaired with E81T1-Ni1C flux core MIG. 100°C to 200°C preheat. PWHT 600°C ±40 °C.

Machining the large bores has problems that the machine shop says act like "hard spots."

1 - can we anneal or otherwise heat treat the part to make the welds machine like A27 Grade 60-30 steel?

2 - is there another MIG wire or SMAW filler that would machine exactly like soft, mild steel?

Thanks,

Dan T

 

[kingnero]

Based on the max. alloying elements, carbon equivalent could go as high as 0.6
Preheat of 100°C is insufficient. 200° is better, but on a casting of that thickness still on the low side. Do you know for sure the temperature is achieved "inside" the plate, so not only on the surface?
Why are you using Ni filler? The base metal is 60 ksi, the filler is near 100 ksi iirc.
Probably you could get away with a run-of-the-mill 70S-3 wire.

 

[dtimberlake]

The foundry uses the E81T1-Ni1C flux core as their standard for cast steel.

Thanks for the wire recommendation. We are pursuing "lesser" weld materials.