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Mostahl, High-Alloy Steel

One day, a dwarf had too much to drink before heading back to work at the smelter. In their inebriated state, they added a littany of impurities to the steel they were attempting to make, mistaking pyrolusite for coal - much to their surprise, the resulting alloy wasn't nearly as brittle as anticipated. Rather than being executed for mismanaging the fortress's precious iron resources, they were permitted to investigate further!

Mostahl is a steel alloy that tempers to a soft hay color, containing a high percentage of the elements nickel, chrome, molybdenum, vanadium, manganese, and cobalt. It possesses superior mechanical properties to steel, being more resistant to impacts and much more resilient to shear forces, as well as able to hold a much sharper edge - however, it is less ductile, and more prone to breaking once its mechanical limits have been exceeded. Thankfully, no weapons-grade materials shy of adamantine or divine metal are capable of meaningfully damaging it.

Mostahl is produced in bulk due to the sheer volume of ingredients involved. All of the following are required:
1 bar iron
1 bar pig iron
1 bar steel
1 bar charge chrome
1 bar nickel
1 bag vanadium slag
1 bag molybdenum slag
1 bag manganese slag
1 bag cobalt slag
1 unit flux
1 carbon source (coke or charcoal)
Fuel, if not using magma

Charge chrome is a ferrochrome alloy smelted from chromite, a vanilla stone the dwarves have long since known of but only now been able to process!

The intermediate slag products are created at a kiln. Vanadium slag is produced as a trace element from magnetite, requiring a carbon source as well. Molybdenum slag is produced from molybdenite, a rare stone found in igneous intrusive and quartzite environments, as well as within anhydrite and pyrite pockets. Magnesium slag is produced from pyrolusite. Cobalt slag is produced from cobaltite. A unit of flux is required for each slag precursor. Bags are needed to contain the resulting products.

Mostahl is a complex and labor-intensive weapons-grade metal, as valuable as platinum or aluminum, and effectively a direct upgrade to steel. Its many ingredients are uncommon, and all are needed to complete the alloy - trading or especially fruitful mining are required to source the precursors. While the metallurgy is based in large part on real alloys and properties, the processes depicted in game to obtain this alloy are not realistic. It is, however, balanced for a mid-late game fort to use as a supplement or alternative to other late-game metals, at the expense of not being quite as effective in arms and armor, and being exceptionally logistically challenging - while the production process itself is marginally more labor-efficient than conventional steel due to the bulk volumes at play, the additional dependencies on other industries are quite demanding.