This "sub-zero" treatment process, particularly suitable for treating stainless steels, high-speed steels and tooling, comes between the hardening and tempering cycles.

The cold treatment is carried out at the end of the hardening cycle and offers several advantages. *COOL PLUS* reduces the residual austenite content while increasing the hardness and dimensional stability of the processed parts, which also retain an exceptional shine.

Apart from the good results, because of the increased hardness at the end of hardening and the "sub-zero" treatment, the *COOL PLUS* process among other things permits a reduction in tempering cycle times and so costs, hence increasing competitiveness.

This process is characterised by an injection of liquid nitrogen at -185°C. Once injected into the heating zone, the nitrogen changes phase and becomes gaseous.

Vaporisation leads to a considerable increase of the volume of the nitrogen (x700) which is brought in a constant and homogeneous manner into contact with the parts to be treated.

With regard to customers' inherent needs and the different types of trades we encounter, the temperatures required and observed on the surface generally vary between -60°C and -150°C.

This totally automated and controlled process (thermocouples) is fully reproducible. As an example, thanks to *COOL PLUS* a type X20Cr13 steel hardened at 1035°C and reduced to -100°C, at the end of a tempering cycle at 150°C, will have a hardness of 690 HV as opposed to 640 HV without "sub-zero" treatment.

For more information, contact