All carbon steels have close to the same properties. File steel is usually 1095 which is .95% carbon which is a lot. It is the carbon that makes it harden-able.
The temperature of transformation is about 1725F. That is a bright 'cherry red' in color. At that temperature weird and wonderful things happen among the molecules that allows them to be 'arranged' in several ways. Cooling slow makes the steel as soft as it'll get. It is 'annealed'. If the steel is suddenly cooled, it gets as hard as it'll get. "Quenching" can be done in many ways, but .95 C steel needs to cool at a rate supplied by common 'oil'. Auto transmission fluid in good. Water can be used, but there is a danger of cracking in long sections like a knife blade.
TIP: Instead of try to guess at what 'cherry red' is, just stick a small magnet to the part. When it falls off, the transformation temp has been reached, quench fast before it can cool any.
After quenching the steel will be a frosty, dark gray with black patches that will have to be re-polished to bright and shiny but be CAREFUL! If you drop it, expect it to shatter. It is file hard again.
"TEMPERING" or "Drawing Back" is the process of re-heating the steel to a much lower temperature that arranges the molecules for toughness. An oven is best because the entire blade can be heated to the correct temperature and held there to 'soak' which arranges ALL the molecules and not just a few on the surface, but blacksmiths have been tempering by eyeball since Roman times. Here's how.
Steel oxidizes as it heats up and turns color. You've probably seen springs that are bright blue. Spring steel blue is caused by the steel being heated to 550F. The lower colors are 'straw' color. A medium straw is 400F and perfect for the EDGE of your knife. That gives about a 55Rc. An axe or hatchet should be a little softer so a darker straw to purple and Rc 45 is about right.
Here's how to get the right color on your fifth try.
Maybe faster if you're lucky.
Fill a tray or length of angle iron with clean white sand and stand the blade in the sand with the spine down and the edge sticking up. With a torch, heat the angle iron and sand from the bottom and slowly. It should take at least five minutes to see any color in the blade. You want to heat the sand through the iron and the sand transfers heat to the blade. As you see the color, SLOW DOWN with the heat. You want at least 30 minutes of even heat. The color will race up the blade as it gets thinner in section. Be carefull and let it very slowly climb the blade. Have the quench bucket handy in case it gets away from you you can quench to stop too much heat from the edge. It would be perfect if the spine was pale blue and the edge is medium straw.
WHEN you screw up and get too soft a blade, simply re-harden and temper again.
Here's a better description with more technicalities to it. https://en.wikipedia.org/wiki/Temper...8metallurgy%29
This method does NOT work on any stainless steel and the more alloys in carbon steel the more the process changes.
You should be able to clamp a blade in a vise and bend it ten degrees without it breaking but only a fool risk a lot of work ruined by trying it. At least files are cheap and common and have the right alloys to be a very good blade.
I'll add this so you can see what 'modern SS' heat-treating is like. MUCH more complicated but I think worth it. I've used vacuum melt 440-C since 1970 but I was lucky to be on a deer hunt in Colorado and met the owner/metallurgist from Memphis Metal Treating high up on the Flattops a year before. He suffered my questions for a day and a half and satisfied me he knew his stuff and this is the process he used on my knives until dying young. The same process is done by MAXCOR in Colorado Springs and do my work now.
I do everything to the blade but put the guard and handles on and sharpen it. Anything that needs done-drilling, milling, grinding, filing polishing and engraving is done in the annealed state.
The blades are heated in an oxygen free atmosphere to 1785F and held there for 15 minutes.
The quench is in moving oxygen free 'air' at 70F. (High nickle allows very slow cooling to attain maximum hardness.)
The blades then go into liquid nitrogen at -325F for three hours. This is called 'cryo-genic quench'.
The blades are allowed to come back up to 70F and they're transferred to another inert atmosphere furnace for tempering.
They're brought up to 400F and held there for four hours, then allowed to cool back to 70F then the same process repeated again: 400F for 4 hrs then cool to 70F
Each blade is tested in a place I specify and guaranteed 58-59RC +/- half a point.
50 pounds of blades used to be $58 but that was nearly 30 years ago! Several outfits will heat treat individual blades by combining with other orders but it's plain to see, if you have a facility like this, you need TONS of metals going through every day to justify the expense of keeping things hot and cold 24/7.
154 CM is a WEIRD steel that takes even more exotic HT.
Randal has used O-1 bar stock for blades and heat treated in his own ovens for 65 years or so and nobody faults HIS knives!