Cryogenics - cold treating metals
What is Cryogenic Processing?
Cryogenic processing is in the sub-zero (below 0°C) range, though it is not well defined at what point on the temperature scale refrigeration ends and cryogenics begins. DCT (Deep Cryogenic Treatment) is considered below −180°C (−292.00°F) range.
Cryogenic processing requires a process of time and temperatures (some above sub-zero) to achieve the required end result without damage to the product. The alloy or product and customer requirements determine the process requirements.
Here you can find some good information on cryogenic processing.
The National Institute of Standards and Technology has chosen temperatures below −180°C or −292.00°F, The Cryogenics Society of America has chosen temperatures below −153°C or −244.00°F and Wikipedia defines cryogenics as a process of treating workpieces to cryogenic temperatures below −190°C or −310°F.
How Will Cryogenic Processing Benefit You?
Cryogenic treatment improves wear resistance and lengthens service life, giving you the edge in the competition against manufacturing costs and product superiority.
Cryogenic effects have been most widely studied in the context of engineering steels, where it is used to complete the heat treatment process. In the common heat treat practice, the conversion from austenite to martensite is incomplete, which results in internal stresses that can weaken the metal and compromise its dimensional stability. What Cryogenics does, in effect, is complete the quenching process so that most of the retained austenite - the source of the internal stresses - is converted to martensite. The benefits can be dramatic. When cryogenics is used to treat tool steels, for instance, tool life is typically improved by 200-400%, and in some cases 600%.
Although Cryogenics effect on steel is the most understood, the technique is also quite widely applied to other metals and products such as iron, titanium, aluminum, brass and to non-metallic materials such as plastics, musical instruments which have been found to produce a better tone and sustained resonance after cryogenic processing. Also, brake rotors, engine components, off-road equipment, knives and cutting tools. Its benefits are well known throughout the performance race industry, from the weekend warrior to the multi-million dollar race teams.
Some of the terms used in cryogenic processing: DCT (Deep Cryogenic Treatment), deep cryogenic processing, deep-freezing and sub-zero stabilization.
Example of life improvements in metals
Example below of before and after improvements of particular tools after being exposed to cold processing
| Tooling | Average life before treatment | Average life after treatment | Wear Ratio * |
|---|---|---|---|
| 5-cm end mills used to cut C1605 steel | 64 parts | 200 parts | 3.07 |
| Hacksaw blades used to cut bosses on M107 shells | 4 h | 6 h | 1.5 |
| Zone punches used on shell casings | 64 shells | 5,820 shells | 82.5 |
| Nosing thread dies used in metal working | 225 shells | 487 shells | 2.12 |
| Copper resistance welding tips | 2 weeks | 6 weeks | 3.0 |
| Progressive dies used in metal working | 40,000 hits | 250,000 hits | 6.25 |
| Blanking of heat treated 4140 and 1095 steel | 1000 pieces | 2000 pieces | 2.0 |
| Broach used on a C1020 steel torque tube | 1,810 parts | 8,602 parts | 4.75 |
| Broaching operation on forged connecting rods | 1,500 parts | 8,600 parts | 5.73 |
| Gang milling T-nuts from C1018 steel with M2 cutters | 3 bars | 14 bars | 4.67 |
| AMT-38 cut-off blades | 60 h | 928 h | 15.4 |
Table above shows tools being exposed to sub-zero treatment to improve wear ratio and overall life of the tool.
Cryogenic processing, originally developed for aerospace applications, has been used for over 30 years to improve the properties of metals.
* Wear ratio = Life after treatment / Life before treatment