Stress Relief
Stress relief · Stress relief
Stress relief reduces residual stress from welding, machining, forming, casting, or additive manufacture without intentionally changing the bulk microstructure.
Stress relief at a glance
Four scores, each 0–100 against every heat treatment in this catalog. Hardness is derived from the HRC target (20 HRC = 0, 70 HRC = 100) — treatments without a hardness target (anneals, stress relief, HIP, cryo) are not rated. Toughness, dimensional stability and cost are FabDigit's engineering assessment.
What is Stress relief?
Stress relief reduces residual stress from welding, machining, forming, casting, or additive manufacture without intentionally changing the bulk microstructure. It is specified to improve dimensional stability before finish machining or service.
How it works
Residual elastic strains remain after nonuniform plastic deformation, solidification, welding, or rapid thermal cycles. Heating below the principal transformation or solution temperature increases atomic mobility and lowers yield strength, allowing local plastic relaxation while retaining the intended phase structure. A controlled soak equalizes thick and thin regions; slow cooling prevents a new thermal-stress pattern. The temperature must stay below prior tempering or aging temperatures unless property changes are accepted. Stress relief reduces rather than eliminates residual stress, and the released strain can appear as measurable movement.
Why specify it
- Reduces machining movement in welded and flame-cut fabrications
- Uses no hard quench and has high dimensional stability
- Common 1–2 h soak after section equalization
Where it falls short
- Cannot correct existing distortion
- Can overtemper hardened steel if the relief temperature is too high
- Does not remove every residual stress or improve fatigue-damaged material
The Stress relief cycle
Typical furnace parameters from the governing specifications and shop practice; the heat treater sets the exact recipe from the alloy, section size and required result.
| Temperature | 480–680 °C (896–1,256 °F) — Typical steel range; remain below the prior tempering temperature. |
|---|---|
| Soak | 1–2 h — Common steel practice after the entire section reaches temperature. |
| Cooling | Furnace cool |
| Atmosphere | Air |
| Door to door | 3–8 h — Section size and controlled cooling dominate. |
Stages
- 1Heat uniformly below transformation temperature
- 2Hold after section equalization
- 3Furnace cool to limit new gradients
What Stress relief does to the part
| Hardness | No hardness target — the treatment is specified by condition, not by HRC. |
|---|---|
| Section affected | The whole section transforms. |
| Toughness | Proper subcritical stress relief should preserve bulk strength and toughness; excessive temperature can overtemper hardened steel. |
| Distortion | Low risk. No quench is used, but releasing asymmetric stress can move an already unstable part. |
| Surface after treatment | Air treatment leaves light-to-heavy oxide; vacuum or inert atmosphere is selected for bright parts. |
| Machining sequence | Stress relieve after rough machining or welding, then re-establish datums and finish machine critical features. |
Specifications for Stress relief
The documents a drawing cites to define this treatment. Each links to a page explaining the standard, its classes and the tests it invokes.
| Standard | Role | Classes used | Status |
|---|---|---|---|
Heat Treatment of Steel Parts, General Requirements | Governing | — | Active |
Stress Relief of Steel Parts | Governing | — | Active |
Test and related methods: ASTM E10 (Standard Test Method for Brinell Hardness of Metallic Materials), ASTM E18 (Standard Test Methods for Rockwell Hardness of Metallic Materials), AMS 2750 (Pyrometry), MIL-H-6875 (Heat Treatment of Steel Raw Materials).
Drawing call-out
STRESS RELIEVE PER AMS 2759/11 AT 595 ± 15 °C FOR 2 h MINIMUM; FURNACE COOL TO 315 °C; VERIFY HARDNESS PER ASTM E18 AT LOCATION SHOWNWhich alloys take Stress relief?
Verdict per material family, with the grades that behave differently. Each family links to its datasheets in the material library. Typical grades: A36, 1018, 1045, 4140, 17-4PH, 316L.
| Material family | Verdict | Notes |
|---|---|---|
| Yes | Cold-worked brass is commonly stress relieved to reduce season-cracking susceptibility.
| |
| Yes | Stress relief before support removal is standard for many printed alloys.
| |
| Yes | Nickel-alloy weldments and AM parts use alloy-specific stress-relief schedules. | |
| Yes | Stainless fabrications use grade-specific stress relief with sensitization risk evaluated.
| |
| Yes | The cycle is established for carbon, alloy, and tool steels within grade-specific temperature limits.
| |
| Yes | Titanium weldments and AM parts commonly use alloy-specific vacuum stress relief.
| |
| With care | Aluminum residual-stress relief normally uses controlled stretching, compression, or alloy-specific thermal practice.
| |
| With care | Sintered parts may be stress relieved if the alloy and residual porosity permit. | |
| With care | Selected bronze alloys use low-temperature stress relief after casting or machining. | |
| With care | Cobalt-chrome AM parts use alloy-specific stress relief under inert gas or vacuum. | |
| With care | Copper alloys may be stress relieved at lower composition-specific temperatures. | |
| With care | Magnesium castings use tightly controlled low-temperature stabilization cycles. | |
| With care | Cold-worked precious-metal alloys can be stress relieved using alloy-specific low-temperature cycles. | |
| With care | Refractory metals require high-vacuum, material-specific stress relief. | |
| With care | Tungsten heavy alloys may use supplier-qualified stress relief after machining. | |
| No | Zinc alloys melt or lose properties at temperatures used by this process. |
Design rules for Stress relief
What to decide on the drawing before the part goes to the heat treater.
- Identify the alloy designation and incoming condition on the purchase order.A temperature that is correct for one grade can overtemper, sensitize, or fail to transform another grade.
- Place hardness test locations at least 3 mm from an edge where geometry permits.Edge decarburization, local cooling, and indentation spacing can bias the reported result.
- Leave 0.2–0.5 mm finish stock on critical ground surfaces when a quench or scale-producing atmosphere is used.Final grinding removes oxide, decarburization, and dimensional movement after the thermal cycle.
- Allow 2–5 working days beyond machining.Furnace scheduling, controlled cooling, hardness testing, and certification extend beyond the soak time.
- Set the stress-relief temperature at least 25 °C below the previous temper where properties must be retained.Reheating near or above the prior temper can lower hardness and tensile strength.
Stress relief versus the alternatives
Treatments engineers weigh against Stress relief, and when each wins.
| Treatment | Hardness | Toughness | Stability | Cost | Choose it when |
|---|---|---|---|---|---|
Stress relief this page | — | 75 | 95 | $ | — |
| — | 75 | 65 | $ | when steel also needs grain refinement and a full austenite transformation | |
| — | 40 | 90 | $$ | when retained austenite stabilization is the specific objective |
Cost, lead time and applications
Relative cost
Stress Relief is a budget-cost treatment ($) relative to the other heat treatments in this catalog.
Heat treatment is priced per lot with a furnace minimum. The exact figure appears on the instant quote once the part is uploaded.
Lead time
| Added lead time | 2–5 working days |
|---|---|
| Furnace time | 3–8 h |
What Stress relief is used for
- Welded machine bases
- Rough-machined precision housings
- Flame-cut steel plates
- Metal AM build plates and components
Stress relief — frequently asked
What temperature is used for Stress relief?
The representative process window is 480–680 °C, but the exact setpoint follows the alloy and governing specification. The listed soak is 1–2 h after the load reaches temperature.
What hardness does Stress relief produce?
The catalog result is not a specified hardness target. Hardness must be verified on the part or a qualified witness coupon using the test method called out on the drawing.
How long does Stress relief take?
The thermal cycle is typically 3–8 h door to door. Commercial lead time is normally 2–5 additional working days because loading, certification, and inspection are separate from furnace time.
Will Stress relief distort the part?
The catalog rates distortion risk as low. Reserve machining stock and verify critical datums after treatment when tolerances are tighter than 0.05 mm.
How should Stress relief be specified on a drawing?
State the governing process specification, alloy condition, required result, and inspection location. Report hardness to ASTM E18 or ASTM E10 as applicable, and do not substitute a furnace recipe for an acceptance requirement.