>>20180162Caking ability is what makes metallurgical coals, metallurgical coals -- i.e. suitable for producing coke as a fuel for making steel (yes, coke is also a fuel and energy source, not just a carbon source, needed to make steel, though it is a carbon source as well).
Caking ability means that if you bake the coal like a cake, at high temperatures, the "volatile matter" will gasify and go away, leaving hard, porous, grayish coke fuel needed to make steel.
So there's met coal in a nutshell. Later, I will get into the Australian (used in Asia) and American (used everywhere, but not as much in Asia) classification systems for met-grade coals -- coals that are "met grade" by today's standards, though historically, many other bituminous coals, like Illinois Basin and Pittsburgh seam coals (high in sulfur), have been used to produce steel.
So today's classification systems for met coals are just kind of a convenience, not a thorough systemization of ALL possible steelmaking coals and their properties and what's needed to make all different possible bituminous coals into coke.
