New Quenching Process Maximizes Stress Relief

Controlled cryogenic chamber allows critical aluminum parts to achieve superior material stabilization.

The Cryogenic Institute of New England Inc. has introduced Nitrofreeze® “uphill quenching” to maximize stress relief in cast, heat-treated and forged aluminum parts. The process enables critical aluminum components made from aluminum to achieve a superior level of material stabilization.

The procedure involves using a controlled cryogenic chamber where the parts are cooled to ultralow temperatures by using liquid nitrogen or liquid helium. Once the components have reached the low temperature, they are subjected to a controlled warming cycle to a higher temperature appropriate for the alloy. The process is repeated up to six times, each following the same cool down and “uphill” quenching cycle. The process typically operates within a range of 450 degrees F on the low side and up to +450 degrees F at the high side.

The Cryogenic Institute of New England, in Worcester, MA, offers a full range of cryogenic technologies for industry, government, and scientific applications. Services include conventional cryogenic treatment, heat and freeze thermal cycling, cryogenic deflashing and deburring services, shrink fitting services, and dry ice (CO2) blast cleaning. It also offers engineering services, cryogenic lab work in support of R & D, and custom equipment design for cryogenic applications.

“Aluminum alloys used in high-precision aerospace and optic components require maximum part stabilization so that they will hold the tolerances needed in their mission critical tasks,” explained Cryogenic Institute of New England Inc. president Robin Rhodes. “The Nitrofreeze® Uphill Quenching Process eliminates the resident residual stresses in the raw cast or forged aluminum block as well those that are created during CNC machining operations,” he added.

Alcoa adopted uphill quenching in the 1950s for artificial aging of aluminum to produce a more stable microstructure with less residual stress. The adopters of the technique enjoy benefits including reduced part deformation, elimination of machining distortion, and improved mechanical properties. Aerospace and optics firms use uphill quenching to reduce or eliminate “walk and creep,” which can occur during machining of critical tolerance parts.

Most uphill quenching treatments are used in aerospace, high-precision optics and military applications. “Our experience with uphill quenching and other thermal cycling enables us to perform precise profiles as specified by MIL/DOD and U.S. governmental agencies,” said Ryan Taylor, product marketing specialist at the Cryogenic Institute of New England Inc. “We are able to cycle a wide range of parts to temperatures approaching absolute zero at controlled ramps and extended dwells,” he added. The company completes the uphill quenching processes with its own specially developed chambers and other vessels.

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