if your file was wouldn't cut it then it is good high carbon steel however you don't know what type so normalizing it and then re-tempering might or might not get you a good blade as you don't know the proper temps to do that, steel types have different temps and processes so not knowing the steel type is the problem, also not knowing the steel type you don't know how hard it can get. It could also have been work hardened. Having said that i would if i wanted to try and make a blade from it would carefully cut and grind it without trying to heat it and lose its current temper. I have made a few knives from saw blades and they work well but it is time consuming. Use water to keep it cool as you grind it, if you discolor the blade then you have changed the temper. thats a great looking first try and will do the job if you haven't lost the temper.