Steel parts often require some form of heat treatment to increase their hardness and obtain maximum strength and durability. We need to carefully consider the heat treatment processing requirements to ensure the optimum performance properties can be achieved from the steel used to manufacture the machine blade.

Hardening and tempering are generally part of standard blade heat treatment services, to help increase the life of the blade and improve its resistance to wear and tear. But what characterizes these two treatments?

Hardening and tempering

Hardening and tempering are the most common heat treatments for knives. They are performed to give components the mechanical properties they require for their intended purpose.

In this type of heat treatment, the knife undergoes controlled heating to an extremely high temperature (austenitization temperature) in a range of between 790 and 1250 deg C, depending on the chemical properties and behavior of the steel. After a specific time at this temperature, the steel is rapidly cooled or "quenched" in different quenching media (oil, water, pressurized air, gaseous nitrogen). The knife is then "tempered" or soaked at a lower temperature to relieve stress on the blade and to achieve optimum hardness for specific uses such as for example in (metal industry, recycling, wood and wood processing industry and also paper and tire industry). 


Recycling and metal industry

Recycling metal knives

Wood and paper industry

Wood and paper knives

Open vs. protective environment 

Hardening and tempering can be performed in "open" environments, such as furnaces, or in a protective environment such as a gaseous atmosphere, molten salt or vacuum if the knife surface has to be kept clean. This variation is known as "neutral" or "clean" hardening.

This knives were hardened in a vacuum furnace, stacked in a basket and tempered at a lower temperature. 

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What are the benefits?

The heat treatment process brings various benefits. Hardening and tempering helps give knives extra strength and durability, so they do not need to be replaced so often. Hardening in a protective atmosphere or in a vacuum furnace helps knives retain their surface integrity. Vacuum-hardened tempered knives have a clean metal surface.

For additional information about out heat treatment service for your knives, please contact our technology department on +386 2 87 06 242 or send us an e-mail:


Learn more about Heat Treatment at SIJ Ravne Systems

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