Process Anneal
Annealing & softening · Softening
Process annealing is a subcritical softening cycle inserted between cold-working operations.
Process 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 Process anneal?
Process annealing is a subcritical softening cycle inserted between cold-working operations. It restores ductility in low-carbon steel without fully austenitizing the part.
How it works
Cold work stores dislocations and elongates grains, raising strength while reducing available forming strain. Heating below Ac1 allows recovery and recrystallization: new strain-free ferrite grains nucleate and replace the worked structure without an austenite transformation. The required temperature and hold depend strongly on prior reduction, steel chemistry, and strip thickness. Cooling rate is usually not critical because no pearlite-to-austenite transformation is intended, but excessive temperature or time causes grain growth and can reduce surface quality. Protective atmosphere limits oxidation on finished sheet.
Why specify it
- Restores ductility between deep-draw or heading operations
- Keeps the cycle below the steel Ac1 transformation temperature
- Reduces work-hardening forces and cracking risk
Where it falls short
- Primarily useful for low-carbon cold-worked steel
- Cannot replace final hardening where strength is required
- Excess soak can produce coarse grains and orange-peel surfaces
The Process 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 | 550–700 °C (1,022–1,292 °F) — Subcritical recovery and recrystallization range for low-carbon steel. |
|---|---|
| Soak | 0.5–2 h — After load equalization; strip practice can be much faster. |
| Cooling | Still air |
| Atmosphere | Endothermic gas / vacuum |
| Door to door | 2–6 h — Batch furnace practice. |
Stages
- 1Heat below Ac1
- 2Hold for recovery and recrystallization
- 3Air or controlled cool
What Process 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 | Formability is restored by reducing dislocation density; final ductility depends on prior cold reduction. |
| Distortion | Low risk. No quench is used, although asymmetric residual stress may relax. |
| Surface after treatment | Protective atmosphere is used for bright sheet; air heating can scale thin stock. |
| Machining sequence | Usually followed by another forming operation; final dimensions should be established after the last anneal. |
Specifications for Process 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 |
Test and related methods: ASTM E10 (Standard Test Method for Brinell Hardness of Metallic Materials), ASTM A1033 (Standard Practice for Quantitative Measurement and Reporting of Hypoeutectoid Carbon and Low-Alloy Steel Phase Transformations), MIL-H-6875 (Heat Treatment of Steel Raw Materials).
Drawing call-out
PROCESS ANNEAL PER AMS 2759 BELOW Ac1; VERIFY FINAL HARDNESS 115–150 HBW PER ASTM E10 ON WITNESS COUPONWhich alloys take Process anneal?
Verdict per material family, with the grades that behave differently. Each family links to its datasheets in the material library. Typical grades: 1006, 1008, 1010, 1018, AISI 1020.
| Material family | Verdict | Notes |
|---|---|---|
| Yes | The cycle is established for carbon, alloy, and tool steels within grade-specific temperature limits.
| |
| With care | Sintered steel can be treated after density and residual porosity are qualified.
| |
| With care | Brass is process annealed at lower alloy-specific temperatures, not by the listed steel cycle. | |
| With care | Copper alloys can be recrystallization annealed, but require a separate alloy-specific schedule. | |
| With care | Printed steel may use the cycle after density, chemistry, and build-orientation effects are qualified.
| |
| With care | Some cold-worked stainless products use subcritical anneals, but grade-specific solution or stabilization practice usually governs. | |
| No | Aluminum does not use this ferrous transformation cycle. | |
| No | Bronze requires composition-specific annealing or precipitation treatment. | |
| No | Cobalt-chrome requires alloy-specific solution or aging practice. | |
| No | Magnesium requires tightly controlled alloy-specific cycles. | |
| No | Nickel alloys require alloy-specific solution, anneal, or age cycles. | |
| No | Precious metals require alloy-specific annealing or age-hardening practice. | |
| No | Refractory metals require material-specific vacuum annealing practice. | |
| 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 Process 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 2–5 working days beyond machining.Furnace scheduling, controlled cooling, hardness testing, and certification extend beyond the soak time.
- Define the cold reduction before the anneal.Recrystallization response depends on stored strain energy, and lightly worked regions may not recrystallize uniformly.
Process anneal versus the alternatives
Treatments engineers weigh against Process anneal, and when each wins.
| Treatment | Hardness | Toughness | Stability | Cost | Choose it when |
|---|---|---|---|---|---|
Process anneal this page | — | 90 | 85 | $ | — |
| — | 95 | 80 | $$ | when full transformation and maximum bulk softening are required | |
| — | 75 | 95 | $ | when dimensional stability is needed without recrystallization |
Cost, lead time and applications
Relative cost
Process Anneal 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 | 2–6 h |
What Process anneal is used for
- Deep-drawn steel shells
- Cold-headed fastener blanks
- Rolled low-carbon strip
- Multi-stage formed brackets
Process anneal — frequently asked
What temperature is used for Process anneal?
The representative process window is 550–700 °C, but the exact setpoint follows the alloy and governing specification. The listed soak is 0.5–2 h after the load reaches temperature.
What hardness does Process 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 Process anneal take?
The thermal cycle is typically 2–6 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 Process anneal 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 Process 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.