Once you get to Vulcanus, iron pipes quickly become obsolete except for a few things.
Electric engine units require mechanical engines which require pipes. This whole thing makes no sense. It would be great to see a different recipe for them using copper wire + steel motor housings (new item) + rare metals.
Rocket silos require iron pipes. Just replace with steel.
Steam turbines have a really strange recipe. I would replace all iron components with steel equivalents and remove the steam engines from the recipe. Perhaps add some electric engine units to the recipe instead.
