Stress Relieving is a vital process in which we reheat parts to redistribute residual stresses from machining, forming, or prior heat treating. Not only does this improve the component’s dimensional stability, but it also improves the component’s stress state as well.
Common Alloys that we treat through Stress Relieving
- Carbon Steels, e.g., 1018, 1045
- Structural Steels, e.g., A108, A572
- Alloy Steels, e.g., 4140, 4330, 4340
- Stainless Steels, e.g., 304, 316, 17-4
- Superalloys, e.g., Haynes, Hastelloy
- Aluminum, e.g., 6061, 7075
TMT’s Equipment and Variations of Stress Relieving
A standard stress relieving process involves heating a part, holding it just below the critical temperature, and then slowly cooling it. Care must be taken for hardened materials to not exceed the original tempering temperature that would decrease the strength. Controlled ramp rates and thermocouple driven control can be used when required.
Care must be taken when stress relieving austenitic stainless steels to avoid the sensitization range which will decrease corrosion properties. Parts can be stress relieved in air or vacuum atmospheres.
Applications of Stress Relieving
- During machining, stresses can be introduced via local deformation due to the cutting process. Aggressive feed rates can also increase these stresses. In addition, operations that introduce thermal gradients into the part or shaping operations, like bending and swaging, may introduce stresses to the component. Stress relieving helps to improve dimensional stability in subsequent machining operations, field use, and heat-treat operations.
- During the creation of the raw material, significant stresses are introduced as the material solidifies and cools. When a part is machined from the resulting material, such stresses can be released, causing the part to deform. Stress Relieving reduces this effect.
- Low-temperature stress relieving can be performed for high-strength parts. A low-temperature, stress-relief type of process is commonly used for reducing hydrogen embrittlement after plating.
- See Post-Weld Heat Treat for more details on stress relieving welds.
- AMS 2759/11
- ASTM A106, B850
- MIL 1684
What To Consider When Specifying for Stress Relieving
- Heat-Treat Condition
- Furnace Atmosphere
- Specification (if required)