Joining cast iron and steel

[SteveG]

The boss (SWMBO) has allocated me the task of "joining together" some bits of old metal junk that will form her new garden sculpture.
Doesn't have to carry any real load/structure other than its own weight but needs to sturdy enough to take the occasional small grandchild attempting to climb or a decent bump with the lawnmower.

The steel bits are no drama - just weld them with the MIG.

Problem is there are some cast iron bits that need to be joined to the steel. One bit I can reasonably just drill/tap and bolt without ruining the look, but others I can't.
I've done a quick test welding a steel nut to a cast iron boss with the MIG and standard wire, but a light tap with the hammer just knocks the nut off so can't use that.


At my disposal I've got MIG/TIG and stick welders along with a MAPP gas torch. Unfortunately don't have access to oxy-acetylene gear.
I have steel and stainless wire for the MIG and general, stainless, and some eutectic 680 rods for the stick welder.

I've never done any TIG brazing before, but thinking of trying that with some preheat.

Any ideas/comments?

Steve