welding 12L14

12L14 is "the" freecutting iron based low carbon alloy. It contains Lead and from safety point of view I think it will be a problem. Although I am not a metallurgist but to my best knowledge all free cutting alloys do not fit for welding due to the additives in the alloy matrix intended to improve nachinability such as Lead, Phosphor etc.

Leaded steels like 12L14 exhibit poor weldability due to the sulfur and lead contents. Extreme caution is required when welding this material because of the potential for hot cracking during welding.

I've been involved in a case where parts were welded onto pivot pins made of Stressproof 1144. Even with preheat and good welding practices we experienced cracking. My experience and research tells me never weld a resulfurized steel and lead just adds to the problem. Switch to the standard low carbon steels and tell the machining people that's the way its got to be. We ended up switching to 1050 with 100k yield for the Stressproof. Cracks disappeared and so did field failures.