All the following are Death rotes from Mage: the Awakening:
- Ghost Gate (Death •••) allows the mage to cross over into Twilight, becoming a Twilight being and interact with objects and denizens there.
- Ghostly Object (Death •••) allows you to turn a real world item (like your hunk of iron) into a Twilight object by utterly destroying it in the real world.
- Sculpt Ephemera (Death •••) allows you to take a Twilight object and reshape or enhance it, with successes going to durability first, then other bonuses.
- Touch of the Ghost (Death ••) allows you to use Twilight items in the real world. (Note that the duration here is "Prolonged," rather than Lasting.)
So, to accomplish what you want to do, you'd first need to destroy the lump of iron and cast Ghostly Object on it. Then, you'd cast Ghostly Gate to enter Twilight, and Sculpt Ephemera to give it the shape and bonuses you want. Ghostly Gate back out again, and use Touch of the Ghost to use the item for a duration contingent on the number of successes you got. That's four spells to accomplish something that could be done pretty easily with Matter — the other Moros Ruling Arcanum.
It sounds like you've assumed that going into Twilight through a Ghostly Gate turns all the things you have into ephemeral items as well. Based on the requirements of Ghostly Object, there's no reason to believe that's true; you'd need some kind of Matter-Death conjunctional effect to pull that off, and if you've got that much Matter, you can bonus up your stuff directly.
Twilight is part of the Material World — it, too, is separated from the Shadow by the Gauntlet. You'd need Spirit 3 to lay down a pathway between the two worlds to get the Ephemera there. Once it's there, yes, you can use the Ephemeral Object in Shadow just as you could in Twilight.