Where it comes from
Frontier raiders always drop it. So do armoured hollows, whose armour comes apart into it, an Ironbound set giving more than a Scavenged one. The robots of the Signal Keep leave plenty, the Castellan most of all, and cave caches hold some.
What it is for
Smelt it into iron ingots at the Smelter, or pack it straight into iron Bombs and blasting at the Powder bench. The Recycler also breaks old gear back down.