Originally posted by Trakehner:

You have to unlock the next tier smelter (blast furnace) that allows you to smelt black ore and flammetal from the Ashlands.
https://www.shacknews.com/article/123483/how-to-smelt-black-scrap-metal-valheim

should mention at this point that Flametal doesn't currently have a use in the game right now. but its easy to stock up on right now for later as the only mobs in the Ashelands are Surtlings.

down side is getting close to the Ashlands will mark everything within 500 meters or you as "explored" so new content won't be added to in later patches. There also isn't a lot of the biom so you might end up with most of it "explored" before the biom even gets real content. like I did :(