Is it usefull to go for a smaller size of electrode to avoide Carbide precipitation?

Using a SS-312 type electrode for joining a 4140 type Chrome - Moly Steel broaken shaft, with a dia of 10", should we go for 3.2mm size for 'V' grove joining and build up rather to use a 4mm size electroe to avoid Heat input and carbide precipitation.If yes then please confirm with your conception and if not ,please give the reason.