Files are good Denis, but test the steel first so you don't screw it up at the heat treat stage.
#1) Get a little test piece red hot ( if you want to be scientific use a piece of magnet on a stick to confirm that it's become non magnetic ) and then allow it to air cool.
If it's softer afterwards go to #2
If it's still hard then it's an air hardening steel and you have your work cut out there
#2) Take your now soft test piece, heat it to critical again and quench in oil
If it has hardened you have an oil hardening steel
If not, go to #3
#3) Heat to critical, quench in water. If it doesn't harden then you did something wrong
This test will ensure you don't use an incorrect quenchant and fail to harden the blade, or worse make it crack
Then heat the whole file to critical and allow it to cool slowly in wood ash or vermiculite or similar. You don't want to work steel in it's hardened state unless you have to ( I'm assuming you aren't forging to shape )
#4) Have Fun !
