I am forgetting where I was reading on Euro steel and there is a bit about Swedish trade with England (14th century?) and that some of it was slag from Swedish smelting. Then de-carbing in making shear/blister. Buying the cast iron/slag dross for cheap. .Paraphrasing there, it has been decades.
It was probably in reading and searching here or a random Swedish steel article attached to Euro steel. There is a lot of port entry data and stuff like trade 'tariff' on Flemish steel items and a push for steel qualities (<15th century?)
https://www.british-history.ac.uk/
The Smiths like this book;
"The Knight and the Blast Furnace: A History of the Metallurgy of Armour in the Middle Ages & the Early Modern Period" by Alan Williams
A very good history of German steel can be read in;
"The Arms of Krupp 1587-1968: The Rise and Fall of the Industrial Dynasty That Armed Germany at War" by William Manchester
Great stuff I have not revisited in a long time.