So, in my setting, there are dwarves that make good steel. Shocker, I know. To refine the ore, they rely on the bloomery process like everyone else, using anthracite (when they can get it), charcoal (the normal fuel) or bituminous coal (when they can't get a hold of anthracite or charcoal). From there, most of the more skilled blacksmiths use the crucible process to refine their iron blooms further, although only a minority are able to control the carbon content well enough to make proper steel consistently. For most dwarf-smiths, particularly the younger ones, the process is shrouded in superstition that prevents them from being able to make the highest quality steels (e.g. one must use the knuckle-bone of certain creatures for flux, using the blood of strong beasts, etc)
But the most skilled smiths are also wizards, able to manipulate the heat around them. Typically, they pull heat out of magma flows and geysers underneath the mountain tunnels they inhabit, and direct and concentrate it into the crucibles to get a more consistent, faster, and cheaper melt. These wizards are also capable of refining certain metals out of ores that would otherwise be impossible to produce with their (late medieval) technology, e.g. aluminum or tungsten.
This brings me to my question. Is there a reason that he might make his crucibles out of tungsten, instead of using more traditional clay or clay-graphite crucibles?
For the sake of argument, let's set a few parameters. This master dwarf-smith, although he can use magic to refine, melt, and shape any metal, can only do it a little bit at a time, and doing so drains his magical energy stores for weeks on end. Thus, though he can't use it to refine steel directly, he can produce crucibles with the skill. Further, although they're aware of graphite and have been known to produce graphite crucibles, there aren't any good deposits of it anywhere near their lands, while there are some good seams of tungsten ore. Lastly, dwarves have a lot of experience working tungsten using magic, and due to its extremely high magical conductance (jargon, I know), it's widely used among dwarves for magic wands and staves.