|Annealing, Hardening, Tempering - Course: Working Techniques of Heat Treatment of Steel. Trainees' Handbook of Lessons|
By this process, the strength of unalloyed steels with a carbon content of generally 0.2 to 0.6% in most cases can be changed in a wide range.
In spite of the low carbon content, those steels can reach higher strength values with higher toughness at the same time.
1. Heating of the material according to the hardening temperature in furnaces or melting baths between 700 °C to 860° C.
2. Quenching in water or oil to lukewarm.
3. Tempering according to the desired properties at temperatures between 360°C and 670°C and cooling down to lukewarm.
A high tempering temperature decreases the strength and increases the toughness!
Which properties shall be reached by hardening and