The black art of changing a metals characteristics is an art but in days past it was known to a few hence the name Blacksmith but you dont have to be a full time practitioner of the black art to do it on a small scale at home. Looking back at the number of times that needed to use high Carbon steel to make parts was very minimal though it was good to know how it was done, usually the steel I used was a piece of second hand scrap and usually in the hardened state, and of course the part was needed yesterday to no chance of the luxury of purchasing new and in an anniellid state.
So lets do it is not Rocket science.
1) to soften a piece of hardened high carbon steel such as a chisel, old filed saw blades, etc. A gas blow torch capable to heat the price of metal red hot, A little luxury a box of dry sand. To soften the steel from its hardened state you heat it to cherry red and let it cool down slowly, if you bury it in dry sand it will cool slowly failing that just apply some heat now and again to stop the metal cooling down to quickly. If normal high carbon steel it will be soft enough to work with hand tools.
2) Now to harden the steel we heat it to cherry red and keep there for about a minute, then plunge quickly quench into oil or water my prefeed method is having a tin box with about six inches of water and two inches of oil floating on the tot, lets just say the best of both worlds.
Annealing to the required hardness because the steel you have now is glass hard and if you struck it with a hammer it would shatter. To make the steel usable we have to adjust its hardness for what is required of the steel to do. This is accomplished by heating the steel again to the annealing temperature required. For a DIY person watching the oxide colours change with temperature on the steel you are heating after polishing some of the surface rather than an expensive annealing oven.
In the photograph is a photograph of the oxide colours used for differing uses you will see as you heat the metal to anneal it, to fix the temperature you can plunge the metal into cold water.
it all sounds complicated but from start to finish about five minutes. Give it a try, it really is simple and I will say one of the best pieces of information I ever learned during my apprenticeship.
