Mike,
They are most likely some form of carbon steel which will have been tempered for toughness. Carbon steel was the forerunner of High Speed Steel for use as lathe tools and whilst it will cut non ferrous and mild steel, it does not like heat and must be kept cool or it will lose its' edge very quickly.
With the price of HSS, my advice is don't bother. IMHO it's a lot of work to grind them to the correct shape and then temper them, to end up with a second rate lathe tool.
Hope this helps ??? ???
Best Regards
Bob.
EDIT - MM's suggestion is a good one. :bow: :bow: