Controlled Atmosphere Hardening

Hardening is the heating and subsequent cooling of steel at such a speed that there is a considerable increase in hardness, either on the surface or throughout. In most cases hardening takes place in conjunction with subsequent reheating, the tempering.

It should be noted that Hardening means to fully through harden a material. Hardening and tempering is therefore quite different from surface hardening or precipitation hardening.

Depending on the material, hardening improves the hardness, wear resistance, fatigue life and increased tensile strength.


 
 
 
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the process
Controlled atmosphere hardening is the hardening of components in an inert atmosphere designed to match exactly to the carbon content of the respective material in order to protect the surface of the component against carburisation and decarburisation and against scaling and oxidation and. By regulating carbon potential in the inert gas atmosphere, decarburisation and carburisation processes can be reversed.

At temperatures normally above 780°c the structure of the material is first converted into an austenitic structure. The workpiece is maintained at this temperature so that the alloying elements can be incorporated homogenously in this austenitic structure. The workpiece is then quenched in such a way a so-called martensitic structure is originated. Next, tempering creates the desired properties of the component, above all, the necessary hardness and toughness. An optional sub-zero treatment can be carried out after the protective gas hardening which serves to transform the retained austenite and stabilize the martensite. Because of the high temperatures and rapid quenching involved, there will inevitably be some degree of distortion.

Most processes are performed in highly sophisticated furnace equipment, specially designed to give the best results possible.

 
 
 
the commonly treated material and fields of application

Practically all technically interesting steel alloys, such as spring steels, cold-worked steels, quenched and tempered steels, anti-friction bearing steels, hot-worked steels and tool steels, as well as a large number of high-alloy stainless steels and cast-iron alloys, can be hardened.

Hardening of metals and steels in general is a very broad subject and there are many different routes which can be used for different materials. If you are in any doubt about the best process for your purpose, we would advise that speak to one of our experienced metallurgists prior to specifying treatments.


 
 
 
specialised case hardening and low pressure vacuum heat treatments
 
 
 

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Registered Address.: Aalberts Surface Technologies Heat Ltd, Blackhorse Road, Letchworth. SG6 1HD 

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