Uphill Quenching

Residual Stress Relieving for Aluminum

One offering from our full range of thermal cycling services is uphill quenching for aluminum. This service is typically used for residual stress relief in metals. Through our vast thermal cycling experience, we have developed many proprietary uphill quenching profiles. In addition, we can follow recipes and formulas as called in MIL/DOD specifications or as written on part drawings. Many of these quenching profiles involve three cycles between cold and hot temperature extremes. We have completed uphill quenching operations from one to six cycles. In addition, we have completed these cycles utilizing both liquid nitrogen (-320°F) and liquid helium (-448°F) for the most advanced uphill quenching specifications.

Uphill quenching has been used for aluminum components to relieve residual stresses created during the manufacturing phase. Uphill quenching was originally termed tri-cycle stress relieving. Three cycles between cold and hot temperature extremes would be completed. In the beginning, dry ice was used followed by an immersion in boiling water. Several years later the process began to use liquid nitrogen and steam at different velocities. When parts frozen by liquid nitrogen were subjected to rapid heating via extreme temperature gradients it was determined that the maximum stress relief benefit was attained. This became the most effective way to stress relieve heat treated aluminum components. It is important to note that the high side of the quench does not exceed temperatures that would adversely affect tensile strength.

Many aluminum components from the aerospace and defense industries undergo cyclic loading. Over time cyclic loading can result in part fatigue failure. Residual stresses from manufacturing will be inherent in these components even after heat treatment. As a result, companies will uphill quench their parts to relieve these residual stresses immediately following heat treatment. Other benefits of uphill quenching include improved mechanical properties, significant reduction in distortion, elimination of machining distortion and reduced manufacturing costs (less scrapped parts).

Uphill Quenching is completed in the following steps:

1. Cool parts in liquid nitrogen and liquid helium if specification requires temperature lower than liquid nitrogen’s boiling point.
2. Allow parts to reach equilibrium in liquid nitrogen. Once equilibrium is attained, the part will be uniform in temperature.
3. Transfer parts to heating element.  In most cases this is boiling hot water, steam, or convection heat.
4. Uphill quench parts via rapid temperature gradients for a specified amount of time.
5. Measure part temperature to ensure that the part met specification.
6. Repeat cycle as designated by specifications or part drawings.

At The Cryogenic Institute of New England, Inc. we have substantial experience in uphill quenching. We have completed work for U.S. Government agencies, MIL and DOD contractors, universities and private industry.

Call us today for more information on uphill quenching at 800 739-7949 or email us at info@nitrofreeze.com.