>>61232388The "pedantry" has been covered by others, so I'll leave that. But overall the way you seem to equal dissolved impurities with the slag (which is a necessary for for the process, it goes bad if you don't have enough, and with modern metallurgy it can pull impurities out of the metal) simply suggests that you're not familiar with what happens in a smelter. Also, solutions (liquid or solid) do not just separate out. That's what makes them solutions instead of suspensions. Only if you have a supersaturated solution will things want to fall out, and then only the excess. As far as iron making goes, the slag is not dissolved into the metal, it's a separate phase.
Now I did misread one part of your post, I thought you were talking about the slag melting, not the metal. Alas, this doesn't leave the comparison you seem to be trying to make a very reasonable one. You're jumping all over place and time to pick out the tastiest cherries on one hand, and then comparing the result to one take on traditional Japanese sword making on the other. Simply "I'm talking about the production of Nihonto, not modern Japanese heavy industry. To legally qualify, they must use traditional methods." makes a mess out of things, because you're doing this in reply to OP who specifically asked about WW2 when that tatara was at best someone's back yard hobby, and the laws you're taking about are a post war affair. Nor do you seem to know which processes you're actually comparing, because the historical crucible steel making you refer to was usually done with metal as the raw material, not ore. (See for example Manouchehr; Arms and Armor From Iran, and Buchanan; A journey from Madras, through the countries of Mysore, Canara, and Malabar.) Thus it isn't an alternative to the tatara that removes the need for folding, but an alternative to the folding. The end result of this being your claim that European swords were some kind of monosteel in the days of Muaramasa, which is just bollocks.