[LT] No-steel-pocalypse! Lifespan of iron & steel equipment?

[Seneschal]

So, I'm currently GM-ing a low-fantasy-bordering-on-horror campaign inspired by Dark Souls. A thousand years ago, the main culture of the setting were the recipients of a divine boon that made them amazing blacksmiths (i.e. in their hands, iron had the melting point of lead), so they easily made steel weapons and late TL4 plate, even if their furnaces are TL1, 2 at most.

That boon is due to end in a month, and I was wondering just what kind of chaos would ensue. Assume that the biggest portion of their economy is based on metalworking. How soon would steel need maintenance which could not be done anymore? What components of infrastructure used iron or steel at TL4, and would now become irreplaceable? What adjustments would need to occur if an entire culture would have to switch to softer metals overnight?