Heat treatment is the soul of a cutting tool, by changing the microstructure of the steel to improve the performance of the tool.The sharpness, hardness, toughness, corrosion resistance and abrasion resistance of the cutting tool are directly related to the heat treatment of steel.Only proper heat treatment can improve and give full play to the properties of steel.
The four basic processes of annealing, normalizing, quenching and tempering are often said to be "four fire" in the cutting tool heat treatment. C·Cutting tools are paying attention to the "four fire" all the time to develop better cutting tools to make hard cutting easy.
Annealing is the process of heating the cutting tool to an appropriate temperature, holding the cutting tool for a different time according to the size, and then slowly cooling the cutting tool.The purpose is to make the internal structure of steel reach or close to equilibrium state, so as to obtain good process performance and service performance, or to prepare for further quenching.
Normalizing means heating the cutting tool to a suitable temperature and cooling it in the air.The effect is similar to that of annealing, but the resulting tissue is finer.Normalizing is often used to improve the cutting performance of cutters and is sometimes used in the final heat treatment of less demanding steels.
Quenching is the most important and commonly used of the four fires.Quenching is heating the cutting tool to a certain temperature and immediately cooling it in oil or muddy water containing minerals.The main function of this process is to improve the hardness of the cutting tool so as to fully display the excellent performance of Damascus cutting tool.In practice, materials are different, quenching temperature and quenching medium are also different.The heating temperature depends on the specific situation, too high temperature tool easy to crack, too low temperature will not improve the performance of the tool.
There are various quenching methods, including local quenching, integral quenching, surface quenching, cold quenching, air quenching, transparent quenching, jet quenching, layered quenching and so on.In this part, the cutting tool maker needs to know the material, what to use for the fire, what water to use, and then complete the quenching according to the fire color.
Tempering is the process of heating hardened steel to an appropriate temperature, keeping it hot for 1-2 hours before cooling.After quenching, the cutting tool steel will become brittle, and the purpose of tempering is to eliminate the residual force on the cutting tool during quenching, reducing the brittleness of the cutting tool.
It should be noted that the tool heat treatment process is not necessarily four fire.Most of the time, only after quenching and tempering two steps, or even a quenching.The purpose of quenching and low-temperature tempering is to improve the hardness, strength, plasticity and toughness of the cutting tool and to obtain comprehensive mechanical properties, which is mainly to balance the strength and toughness.
Every cutting tool maker's heat treatment method is his own secret.The same steel in the hands of different cutting tool, will appear different heat treatment effect.
All of good cutting tools need, is after heat treatment, so that the cutting tools steel properties to achieve the optimal balance.