Cryogenic treatment

A cryogenic treatment is the process of treating workpieces to cryogenic temperatures (i.e. below −190 °C (−310 °F)) in order to remove residual stresses and improve wear resistance on steels. In addition to seeking enhanced stress relief and stabilization, or wear resistance, cryogenic treatment is also sought for its ability to improve corrosion resistance by precipitating micro-fine eta carbides, which can be measured before and after in a part using a quantimet.

The process has a wide range of applications from industrial tooling to the improvement of musical signal transmission. Some of the benefits of cryogenic treatment include longer part life, less failure due to cracking, improved thermal properties, better electrical properties including less electrical resistance, reduced coefficient of friction, less creep and walk, improved flatness, and easier machining.[1]

Processes

Cryogenic hardening

Cryogenic hardening is a cryogenic treatment process where the material is cooled to very low temperatures. By using liquid nitrogen, the temperature can go as low as −190 °C. It can have a profound effect on the mechanical properties of certain materials, such as steels or tungsten carbide.

Main article: Cryogenic hardening

Applications of cryogenic hardening

Cryogenic machining

Cryogenic machining is a machining process where the traditional flood lubro-cooling liquid (an emulsion of oil into water) is replaced by a jet of either liquid nitrogen (LN2) or pre-compressed carbon dioxide (CO2). Cryogenic machining is useful in rough machining operations, in order to increase the tool life. It can also be useful to preserve the integrity and quality of the machined surfaces in finish machining operations. Cryogenic machining tests have been performed by researchers since several decades,[5] but the actual commercial applications are still limited to very few companies.[6] Both cryogenic machining by turning[7] and milling[8] are possible.

Cryogenic deflashing

Main article: Cryogenic deflashing

Cryogenic deburring

Main article: Cryogenic deburring

Cryogenic rolling

Cryogenic rolling or cryorolling, is one of the potential techniques to produce nanostructured bulk materials from its bulk counterpart at cryogenic temperatures. It can be defined as rolling that is carried out at cryogenic temperatures. Nanostructured materials are produced chiefly by severe plastic deformation processes. The majority of these methods require large plastic deformations (strains much larger than unity). In case of cryorolling, the deformation in the strain hardened metals is preserved as a result of the suppression of the dynamic recovery. Hence large strains can be maintained and after subsequent annealing, ultra-fine-grained structure can be produced.

Advantages

Comparison of cryorolling and rolling at room temperature:

References

  1. ASM Handbook, Volume 4A, Steel Heat Treating Fundamentals and Processes. ASM International. 2013. pp. 382–386. ISBN 978-1-62708-011-8.
  2. Thamizhmanii, S:; Mohd, Nagib; Sulaiman, H. (2011). "Performance of deep cryogenically treated and non-treated PVD inserts in milling". Journal of Achievements in Materials and Manufacturing Engineering. 49 (2): 460–466.
  3. http://www.deanmarkley.com/products/by-subcategory/2-catalog/276-blue-steel-electric
  4. http://www.seymourduncan.com/2011products/zephyr-silver-pickups.php
  5. Zhao, Z; Hong, S Y (October 1992). "Cooling Strategies for Cryogenic Machining from a Materials Viewpoint". Journal of Materials Engineering and Performance. 1 (5): 669–678.
  6. Richter, Alan. "Cryogenic machining systems can extend tool life and reduce cycle times". Cutting Tool Engineering.
  7. Strano, Matteo; Chiappini, Elio; Tirelli, Stefano; Albertelli, Paolo; Monno, Michele (2013-09-01). "Comparison of Ti6Al4V machining forces and tool life for cryogenic versus conventional cooling". Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture. 227 (9): 1403–1408. doi:10.1177/0954405413486635. ISSN 0954-4054.
  8. Shokrani, A.; Dhokia, V.; Newman, S. T.; Imani-Asrai, R. (2012-01-01). "An Initial Study of the Effect of Using Liquid Nitrogen Coolant on the Surface Roughness of Inconel 718 Nickel-Based Alloy in CNC Milling". Procedia CIRP. 45th CIRP Conference on Manufacturing Systems 2012. 3: 121–125. doi:10.1016/j.procir.2012.07.022.

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