To harden the knife, make a few metal plates to conduct experiments. Heat the first plate irregularly from minimum to maximum temperature and put in water or oil. In the grip start breaking plate and to break find you need to size the grain. If the grain at the bend, the metal will have poor cutting quality, kink should have a coarse surface. For example, consider the fracture of a large file, around the perimeter he will have a smooth fracture, but in the heart already will have the desired grained surface. After this experience, you determine the desired temperature for heating.
Now you need to choose the medium for quenching. Hardened in water, oil, nitrogen, and even use mercury. After the heat of the plate should be lowered into the oil, whose temperature is 200°, withstand of 15 minutes to 2 hours, and then put it in cold water. Sometimes for quenching even use liquid lead.
Environment for hardening can be alternated by double tempering or conditioning. Continue with your research. Take a plate, heat it to the desired temperature, make the hardened to such strength that the plate could break the grip if it is to decline at a 30 degree angle from vertical, then release make this disc might break if 45градусах. Using this method, you will get high strength and good cutting properties.
Some General rules: a blade before quenching it is necessary to anneal, then there will be fewer cracks. Do heat slowly, evenly and longer. Use muffle furnace adjustment. For hard quenching into liquid immerse the blade vertically and hold it steady. If you do the annealing in different environments, the knife will last longer.