Not quite what I am trying to do here.  Basically looking for a way to set up  smelter to convert iron to steel by consuming 1 iron and turning it into 1 steel for the initial building.  This could possibly be used for a second tier as well with steel being blended with crystal to a crystal infused metal but that is down the road if I can get the first part to work.

You can also set up an independent improvement that reduces metal income by -1 and increases steel income by +0.5 or so. It could be tricky though, because your metal income may change over time and you could run into negative metal if you just keep subtracting.

Hmm, not sure about that now ...

I think I'd do it more like this.

+1 iron, +2 iron, +4 iron, +3 iron +1 steel, +2 iron +2 steel.

That sort of progression

I do agree, however, that it should be tied directly to the Iron mines (better for a game like this)