Another new development integrates the additional module SCHMETZ system *COOL PLUS* into the standard vacuum furnace. This realises a man less fully automatic hardening and tempering process with a controlled „sub zero“ treatment down to –145°C between the hardening and tempering process.

The retained austenite reduction achieved during the “sub-zero” process minimizesthe quantity of tempering processes at the heat treatment of tool and high-speed steels.

Higher final hardness at hardening and tempering processes of for example stainless steels reduces costs due to a better cutting property at the following mechanical treatments.

Absolute metallic bright surface qualities are guaranteed because the parts do not have any contact with the surrounding atmosphere after the “sub zero” treatment (no surface corrosion).

A smoothly controlled „sub-zero“ treatment is also guaranteed by means of the eligible „sub-zero“ gradient by using load thermocouples. Thus the risk of cracks due to a „rough“ „sub-zero“ treatment like in the conventional processes is restricted considerably.

Advantages of SCHMETZ system *COOL PLUS* fully automatic process cycle:

• no handling between the processes
• lower staff costs
• no risk of accidents due to splashes
• no need for additional cooling machines
• selectable „sub zero“ gradient – low crack risk
• no surface corrosion
• continuous process documentation with complete load thermocouple recording
• absolute load reproducibility

State-of-the-art furnace technology and furnace control as well as a sensible operation of the furnace guarantee to operate our vacuum furnaces energy efficiently and environmentally friendly.

During the heating and temperature soaking cycle the supplied electric heat energy has to balance “empty losses”. These “empty losses” of the hot zone are reduced by means of an insulation structure that is designed as tight as possible. Due to its high temperature resistance and dimensional stability mainly graphite material is used as insulation material for hot zones of vacuum furnaces. By means of the additional use of a reinforced insulation there are even better insulation results. By means of a possible modification of SCHMETZ vacuum furnaces there is also a high energy saving potential at many older furnaces!

The gas distribution during the cooling

In order to guarantee the cooling uniformity within the complete useful space of chamber furnaces gas distribution plates made of hard graphite or CFC are used. Regarding the gas distribution plates we are today able to install newly developed patented insulated nozzle plates instead of the hard graphite plates used so far. This nozzle plate has the advantage of a considerable lower net weight. Thus the energy consumption of the “dead masses” is reduced during the heating and the cooling. In addition the weight-optimized nozzle plates effect a faster heating and a faster cooling of the load. At vacuum furnaces with innovative hot zone design up to 10 % (!) of the usual current consumption can be saved.