I once thought it would be cool to have a spectrometer for analyzing steel chemistry. There is one that works off of a spark test. Can't remember the name but they are portable units good for junkyards and scrap sorting, that kind of thing. Sadly, they are setup to assess the alloying elements and then the steel is matched to known alloys. Carbon testing is not involved. So I gave up on finding an easy cheap way of spec'ing steels.