Careful what kind of ship you use. This can result in the shifting of tons of other resources as well: most notably quatloos, food, and people.
I'd echo this. Your best bet for steel is scouts, but then you're still moving loads of other resources.
If you're going to do it on a colony, then wait until it's got a big enough population that you're not moving a large % of the people. If you want to get steel from your home planet to somewhere else, then same applies for when you get it there and build something.
