Hi Micah , imho anything with a high enuf C content (.05>)could be used for a chisel. The spot that needs to be hard is the cutting surface/end. If you could heat and bend without letting the cutting edge dis-colour, at the same time letting what you heated slowly cool, it more than likely will work. Working with unfamiliar steels is always a $#@* shoot until you discover how they like to be handled. I generally use cheap import tools to modify for single task use , mainly because half the work is done already. And then construct my own out of familiar steels. For cutting edges old files, bearing races work well. For punching/prying tools I like "old" car springs. Ive been told that pre mid sixties are pretty well just carbon steel. Not alloyed as much as modern ones.. The general way to look at making cutting tools..
1 st step.... heat and shape, forge,rough file or grind, followed by slow cool. avoid quenching
2 nd, Anneal to relieve stress. This means re-heat and (really) slow cool in pre heated insulating medium (sand/ dying fire, BBQ etc)
3 rd, Heat treat... this has 2 steps in itself .... 1st is to harden, 2nd to temper
To harden...(step1) heat to non-magnetic and quench in appropriate medium...
To temper...(step2),controlled softening) slowly raise temps to require amounts. this will change depend on tools use. If you are watching heat colours, cutting edges are usually from straw to deeper blue. I would start at straws. If your tools edge chips, temper to darker colour. If it bends, dont go past straws.
Remember books are written about such things, a good one is
http://books.google.com/books/about/The_Complete_Modern_Blacksmith.html?id=em2Xmi1_-GcCHope this helps.......
Kerry