well i think this is a topic of much discussion,
the steel itself in files is a high carbon steel, which is great for knives,
however i think the main problem with forging files (and rasps) is
that the grooves, or furrows i suppose one could call them create weaknesses in the metal and can cause it to break
especially in the process of hardening the steel.
this is actually how the file my knife was made from was broken.
im not sure how accurate my information is and i dont know if im the best to give advice, im not exactly a very experinced blacksmith, but i think the best way to avoid
breaking a file is to either remove the grooves by forging it smooth or by stock removal. otherwise you just have to be really careful when hardening the steel.
but yes files are excellent for making blades and fairly easy to forge
happy forging