A typical sub-zero quenching and hardening chamber:

The parts are loaded on trolleys with a maximum load of 300 kg per trolley. The operating temperatures are -80°C for the hardening and +160°C for the tempering. The installation is equipped with a Siemens S7 PLC and touch screen. The customer has the possibility to program different cycles (temperature/time). For the registration of the temperature/time cycles the installation is equipped with a 2-pen recorder. All the temperature sensors are PT100 of which some are calibrated. The requested temperature homogeneity is ±5°C at -80°C and ±3°C at +160°C. During the acceptance tests, for which the customer used a calibrated controller together with 9 calibrated thermocouples distributed within the chamber, the homogeneity in the chamber was plentifully within the allowable range.