Solution Anneal
Annealing & softening · Softening
Solution annealing dissolves detrimental precipitates and restores a single-phase matrix in austenitic stainless and many nickel alloys.
Solution anneal 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 Solution anneal?
Solution annealing dissolves detrimental precipitates and restores a single-phase matrix in austenitic stainless and many nickel alloys. Rapid cooling retains alloying elements in solution and restores corrosion resistance and ductility.
How it works
Heating above the solvus dissolves chromium carbides, sigma phase, and other constituents that formed during welding, hot work, or service. The soak must equalize the section without excessive grain growth. Rapid water or gas cooling then passes quickly through precipitation ranges so chromium and other solutes remain distributed in the matrix. Austenitic stainless is not hardened by this quench; it is softened and desensitized. Nickel-alloy schedules differ because some grades are solution treated as preparation for aging, while solid-solution grades use the treatment to restore ductility and corrosion performance.
Why specify it
- Restores corrosion resistance after carbide dissolution
- Produces a soft, ductile austenitic condition
- Prepares age-hardenable nickel alloys for controlled precipitation
Where it falls short
- Rapid cooling can distort thin or asymmetric parts
- High temperature can cause grain growth and surface oxidation
- The common cycle does not apply to every martensitic or precipitation-hardening stainless grade
The Solution anneal 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 | 1,010–1,175 °C (1,850–2,147 °F) — Grade-specific solution range for austenitic stainless and nickel alloys. |
|---|---|
| Soak | 0.3–2 h — Minimize time after section equalization to control grain growth. |
| Cooling | Water quench |
| Atmosphere | Vacuum |
| Door to door | 3–8 h — Vacuum heating and load cooling control total time. |
Stages
- 1Heat above the grade solvus
- 2Soak only after full equalization
- 3Rapid water or qualified gas quench
What Solution anneal does to the part
| Hardness | No hardness target — the treatment is specified by condition, not by HRC. |
|---|---|
| Section affected | The whole section transforms. |
| Toughness | Ductility generally rises as carbides and intermetallic phases dissolve; grain growth can reduce toughness. |
| Distortion | Medium risk. Water quenching creates thermal gradients; qualified gas quenching may reduce movement where the specification permits. |
| Surface after treatment | Vacuum gives a bright surface; air furnaces produce tenacious oxide that normally requires pickling. |
| Machining sequence | Finish machining may be required after quench; stainless surfaces exposed to iron tooling may require cleaning and passivation. |
Specifications for Solution anneal
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 |
Heat Treatment, Austenitic Corrosion-Resistant Steel Parts | Governing | — | Active |
Heat Treatment of Wrought Nickel Alloy and Cobalt Alloy Parts | Governing | — | Active |
Test and related methods: ASTM E10 (Standard Test Method for Brinell Hardness of Metallic Materials), AMS 2750 (Pyrometry), AMS 2769 (Heat Treatment of Parts in a Vacuum).
Drawing call-out
SOLUTION ANNEAL 316L PER AMS 2759/4 AT 1040 °C MINIMUM; WATER QUENCH; VERIFY 201 HBW MAXIMUM PER ASTM E10 AT LOCATION SHOWNWhich alloys take Solution anneal?
Verdict per material family, with the grades that behave differently. Each family links to its datasheets in the material library. Typical grades: 304, 316L, 321, 347, Inconel 625, Inconel 718.
| Material family | Verdict | Notes |
|---|---|---|
| Yes | Printed stainless and nickel parts commonly receive alloy-specific solution annealing after stress relief or HIP.
| |
| Yes | Many nickel alloys use solution annealing either as a final condition or before aging.
| |
| Yes | Austenitic stainless is solution annealed to dissolve carbides and restore corrosion resistance.
| |
| With care | Sintered stainless or nickel parts may be solution annealed after density and chemistry are verified. | |
| With care | Cobalt-chrome alloys use composition-specific solution cycles and cooling rates. | |
| No | Aluminum does not use this ferrous transformation cycle. | |
| No | Brass requires lower-temperature stress relief or recrystallization annealing. | |
| No | Bronze requires composition-specific annealing or precipitation treatment. | |
| No | Copper alloys require alloy-specific annealing or precipitation-hardening cycles. | |
| No | Magnesium requires tightly controlled alloy-specific cycles. | |
| No | Precious metals require alloy-specific annealing or age-hardening practice. | |
| No | Refractory metals require material-specific vacuum annealing practice. | |
| No | Carbon and low-alloy steel use full annealing or normalizing rather than this high-temperature corrosion-resistant-alloy cycle. | |
| No | Titanium requires alloy-specific annealing or solution-and-age cycles. | |
| No | Tungsten heavy alloys require supplier-specific sintering and stress-relief practice. | |
| No | Zinc alloys melt or lose properties at temperatures used by this process. |
Design rules for Solution anneal
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 4–8 working days beyond machining.Furnace scheduling, controlled cooling, hardness testing, and certification extend beyond the soak time.
- Provide drain paths for hollow parts before a liquid quench.Entrapped quench liquid can flash to steam and create a safety hazard or uneven cooling.
Solution anneal versus the alternatives
Treatments engineers weigh against Solution anneal, and when each wins.
| Treatment | Hardness | Toughness | Stability | Cost | Choose it when |
|---|---|---|---|---|---|
Solution anneal this page | — | 90 | 55 | $$$ | — |
| — | 75 | 95 | $ | when residual stress must be reduced without a full high-temperature solution cycle | |
| 40 | 65 | 82 | $$$$ | when solution-treated Inconel 718 must subsequently develop precipitation strength |
Cost, lead time and applications
Relative cost
Solution Anneal is a premium-cost treatment ($$$) 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 | 4–8 working days |
|---|---|
| Furnace time | 3–8 h |
What Solution anneal is used for
- Welded stainless process equipment
- Austenitic stainless forgings
- Nickel-alloy turbine components
- DMLS stainless and nickel parts
Solution anneal — frequently asked
What temperature is used for Solution anneal?
The representative process window is 1010–1175 °C, but the exact setpoint follows the alloy and governing specification. The listed soak is 0.25–2 h after the load reaches temperature.
What hardness does Solution anneal 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 Solution anneal take?
The thermal cycle is typically 3–8 h door to door. Commercial lead time is normally 4–8 additional working days because loading, certification, and inspection are separate from furnace time.
Will Solution anneal distort the part?
The catalog rates distortion risk as medium. Reserve machining stock and verify critical datums after treatment when tolerances are tighter than 0.05 mm.
How should Solution anneal 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.