Welding steel to cast iron

[rclxt]

Hi,
I have a cast iron exhaust manifold that Im trying to attach a machined mild steel flange to. The cast iron is about a 1/2 inch thick and the steel flange is about 3/4 of an inch thick. Ive never tried to weld cast iron before so any suggestions or comments would be very welcome. So far some of the suggestions Ive recived are to heat soak the cast iron and pack it in sand. Ive also been told it might be best to run a bead and just walk away for a day and try again the next day. Im thinking that running an inside and outside pass is probably best. If I can, Id like to use my lincoln mig 175 with a co2/ar but im guessing it probably doesnt have enough guts to get the job done but maybe with the two passes im planning on?? If need be I have access to a high dollar tig.
Thanks for the help
Terry

[HWooldridge]

I have welded steel to cast iron using a stick machine and nickel rods. You can preheat the cast iron with a torch after the pieces are tacked together, then run a bead about 1-2 inches long. Immediately take a chipping hammer or pneumatic descaler and peen the hell out of the bead. Start 1-2 inches away from this bead and weld back to it, making sure you get good penetration into the first bead. Keep going until done and don't take a break - get it all done in one session. The peening should take care of stresses and keep it from cracking in the future. If you want to cool it slowly, put it in a bucket of vermiculite or wood ashes to retain the heat. If it fits, you can also put it in the kitchen oven and bring it down very slowly.

[rclxt]

Thanks for the advice. A pnuematic descaler you say? Looks like ive got an excuse to buy yet another new tool!