The continuous process of tempering blade strips
The tempering of blade strips consists of hardening and subsequent one-time tempering. The crystal lattice structure of the blade band is transformed.
In the following, this will be explained briefly and in a very simplified way using the example of martensitic stainless steel.
Heating and holding for austenitizing the blade strip at approx. 1,100 °C in the hardening furnace. Conversion of ferrite into austenite; contained carbides are partially dissolved, thereby increasing the content of carbon and chromium in the matrix.
Subsequent quenching to room temperature in the cooling section. Conversion of most of the austenite into martensite.
of the blade strip in deep-freezing to approx. -80 °C. Further, permanent transformation of austenite into martensite. Depending on the freezing temperature, approx. 15% residual austenite remains in the microstructure.
at approx. 200 °C without holding time in the tempering furnace. Reduction of brittleness and increase of toughness; achievement of additional hardness. Subsequent cooling to room temperature in the cooling unit.