Hello there,
I’m a newbie in sewing machine world but I’m not in welding world.
i don’t know what you have as far as welding equipment but there is a GMAW wire
you should seriously consider
Crown Alloys 44-30 mig wire
It’s not cheap at 70-80 per 2lbs spool, but it’s going to be a more forgiving than any GTAW approach where pre and post heat are critical, and you get a weld that is rather difficult to grind or clean up once your done.
I’d still preheat (I bought a used gas bbq just to use as a preheater!) 44-30 can be filed or ground if you want to clean it post weld.
I’m also a fan of brazing cast iron, but I haven’t done any of that since I bought a spool of the 44-30.
Best of luck
Carl