Cryogenic Applications

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“Cryogenic temperature” is defined by the Cryogenic Society of America as temperatures below -140 ° C. For this reason, it is separated from the so-called sub-zero process or cold process by thermal processors. The temperatures used in the mentioned processes are at most -100°C.

The cryogenic process is a continuation of the heat treatment process which ends at room temperature. The aim is to maintain the martensitic transformation by decreasing to low temperatures and to reduce the residual austenitic amount as much as possible. Cryogenic treatment is performed in specially designed processor controlled chambers.

Cryogenic Applications Detail

Effects of cryogenic treatment:

  • Removal of residual austenite and conversion of the structure to martensite
  • Homogeneous deposition of very fine η-carbide (etacarbide) particles on martensitmatris
  • Regulation of hardness distribution
  • Elimination of internal stresses / residual stresses (affects many mechanical properties)
  • Increases toughness, increases abrasion resistance, fatigue resistance

Change of Wear Life Increase in Cryogenic Steels

Five different tool steels subjected to heat treatment were subjected to abrasive wear test after sub-zero treatment and cryogenic treatment. Table 1 contains these test results. The subzero process improved the abrasion resistance of the steels by 18 to 104%, but the test results in cryogenic treated steels showed an improvement of 105 to 560%.

Rw = F.V / W.Hv, F = force applied in N to press the surfaces together; V = shear rate in mm / s; W = wear rate in mm3 / s and Hv = vickers hardness in MPacin. The Rw value is dimensionless.

A standard cryogenic process cycle:

a: Time from ambient temperature to cryogenic processing temperature.

b: Retention time at this level after the process temperature (-140 ° C) is reached

c: Time to reach ambient temperature after treatment

d: Tempering temperature