Welding Cast Iron

I have been patiently welding the big crack in the front of the cast iron stove I am restoring for a few weekends now. I weld for 10 seconds or so then let it cool down in the flames of firebox of my other stove. Cast iron is difficult to weld because it cracks if you don't do it right. I weld mine over the firebox of the stove, maybe 400 deg/c. I am not sure what the welding temperature is but it is so hot that is has to be done in very shore burst otherwise the temperature difference causes the cast iron to crack.
It's a great excuse to have a sip of my favourite alcoholic beverage while I wait for the temperature to stabilise.