Correct blade hardening is a real art. A knife can be very beautiful and comfortable, but improper hardening can negate its consumer qualities. To prevent the blade from breaking at a crucial moment, a number of rules should be followed when hardening it.
Instructions
Step 1
You should know that hardness is far from the most important indicator of a properly hardened blade. A knife with an overheated cutting edge, which seems to be very sharp and durable, will quickly become unusable, since the edge will constantly crumble. When properly hardened, the knife clamped in a vice must withstand a bend of at least 45 degrees.
Step 2
Ideally, you should take several strips of metal, similar to the one from which you made the blade, and tempered under different conditions. Then check for bending and select the hardening mode that gives the best result. If this option seems too costly and time-consuming to you, temper the blade using one of the recipes below. But in this case it will be difficult to obtain the highest possible quality.
Step 3
The easiest way to quench is in cold water. The heated blade is lowered vertically into the water. When lowered with the tip down, the hardening of the tip and cutting edge will be stronger than when lowered with the tip up. Do not wiggle the blade after dipping it into the water, otherwise uneven cooling can lead to bends and cracks. The strongest cooling will give ice water.
Step 4
The blade can be hardened in mineral oil heated to 200 degrees. Heated oil provides better cooling than cold oil, as its viscosity decreases when heated. Dip the heated blade in hot oil and soak in it for about an hour. Then transfer to water.
Step 5
This option is also possible: heat the blade to a crimson color and lower it vertically, tip down, into mineral oil. As soon as the tint colors (rainbow) appear on the blade, transfer it to the water.
Step 6
You can harden the blade in wet sand. This method provides normal hardening of the cutting edge and leaves a resilient core. The blade can be weaved into the sand several times, this will strengthen the hardening.
Step 7
It is important not only to harden the blade in an optimal way, but also to release it correctly after hardening. Vacation is carried out by heating to a low temperature. The heating method is also important: if you hold the blade in a muffle furnace at a temperature of 190 degrees for two hours, then lower it into the same medium in which it was tempered (water or oil), then it will be twice as strong as with simple heating in the furnace to the same temperature (golden color).
Step 8
For a light leave, boil the blade in water for two hours, then lower it in ice water. If it is thick enough, you can heat the butt in a furnace to a purple color and let it cool slowly.
