Cryogenics goes Deeper

Although the application of deep cryogenics to cutting tools has yielded widely variable results in the past, current data from laboratory and field tests indicate that treatment can markedly increase tool life.

In spite of recent studies showing that deep cryogenics can improve the performance of cutting tools, the use of freezing processes to treat alloy-steel tools is debated in the metalworking community. In the 1950s and 1960s, when cryogenic treatment involved the direct immersion of tools in a medium maintained at -320° F, thermal shock typically damaged the tools. Memories of the unpredictable results of this earlier process have discouraged further R&D and use of cryogenic treatment.

As currently practiced, deep cryogenics does not directly expose cutting tools to cryogenic fluids. To minimize thermal shock, the tools are placed in an airtight refrigeration chamber (cold box) and the temperature of the tools is reduced gradually. The tools are then soaked in a dry cryogenic atmosphere at -310° F to -320° F for 20 to 60 hours, after which they are slowly returned to room temperature and subsequently tempered. The exact temperatures and times vary from manufacturer to manufacturer. Because this process is so time-consuming, it must be applied after heat-treatment. Without knowledge of the tools' heat-treat characteristics, the results of cryogenic treatment are completely unpredictable.

Comaprison of drilling thrust force for cryogenically and untreated twist drills when machining 4340 steel.