Fascinating and so much thanks to everyone!
Ann, "cast steel" is not steel which has been cast. It is a specific early industrial product (patented in England in 1749, I think) called "acero fino" ie. "fine steel" in Spainish (a freind has a Spainish language degree, and she said "fino" has all the same shadings of meaning in Spainish as does "fine" in English.) I've never made either. From my readings it seems to me that the big distinguishment of cast steel (also cast-steel, etc.) from "Eastern"/Tartaric crucible steel, or at least from blister steel, etc. was that it fully melted in the alloying process, while the European blister steel, sheer steel, etc. were alloyed at welding heat, some types in a crucible, which sort of "pudding"ed together, and had to then be hammered down to further join it and folded for homogeneity; don't know enough about Tartar steel to know how much this crosses over to it, or to what specific type of traditional European steel it most closely relates; shear steel I think.
Modern steel production is a full-melt process often and even usually involving (thankfully for my part, except when someone melts an old blade) recycled steel (different percents of different scrap items are allowed for different classes of industrial product), but its product is not "cast steel". Last I heard cast steel may still be produced in Sweden, but the last I heard was some sort of bad news involving this.....
Wrought iron still comes out of Sweden, I read, too.
What of Japanese "blue steel"; anyone know what that is? High carbon, obviously; at a guess, real high, like cast steel.