Heat treatment is the name of several different methods of altering the physical properties of an object or material. In knife production, a heat treatments is an essential processing step to ensure the high quality of the knife blade.
Heat treatment is a collective term for several methods of subjecting an object, such as a knife steel, to certain influences in order to alter its physical properties without altering its external shape. Heat treatments include thermal, mechanical/thermal and chemical/thermal processes. The goal of the heat treatment is to achieve the best possible property profile for the object – for a knife blade, this includes a well-balanced combination of hardness and robustness, elasticity and edge retention.
Heat treatments should not be confused with hot working (which alters the outer shape of the object) or heat-based methods for protecting the surface of an object without altering its material properties (e.g. sealing). Generally speaking, there are heat treatments that cause changes in the microstructure of an object and heat treatments that merely alter the surface of the object. Hardening belongs to the first group. Hardening is an essential step in the manufacturer of a knife blade, because an unhardened blade, even one made from premium-quality steel, would be completely useless.
Apart from hardening, other heat treatments are also part of the knife production process, including normalizing, soft annealing, stress relief and annealing. Heat treatments are of vital importance for the production of knife blades. Next to the selection of the right steel and best possible blade geometry, the right heat treatment is one of the deciding factors that determine the quality of the blade.
The wrong heat treatment can spoil even the best stainless steel. The right heat treatment, on the other hand, can improve the properties of lower-grade steel significantly.