Q+T H900
Through-hardening · Precipitation hardening
Q+T H900 is a precipitation-hardening condition for 17-4 PH (S17400) and 15-5 PH (S15500).
H900 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 H900?
Q+T H900 is a precipitation-hardening condition for 17-4 PH (S17400) and 15-5 PH (S15500). It develops strength by solution treatment followed by controlled aging; the final condition, material specification, and acceptance test belong on the drawing.
How it works
Solution treatment dissolves strengthening constituents and establishes a controlled starting microstructure. Cooling retains a supersaturated or otherwise metastable matrix. During the prescribed age, diffusion forms a fine dispersion of strengthening precipitates that obstruct dislocation motion. Temperature and time control precipitate size, spacing, coherency, and grain-boundary chemistry: lower or shorter cycles generally favor peak strength, while overaging trades some strength for toughness, conductivity, or stress-corrosion resistance. The complete route, including the incoming material condition and cooling practice, is therefore part of the engineering definition.
Why specify it
- Produces 40–47 HRC across the stated grade set
- Provides 1310 MPa or greater tensile capability where the cited product condition defines it
- Adds strength through precipitation rather than a carbon-steel temper
- Can be applied after near-net machining with less movement than a severe steel quench
Where it falls short
- Properties depend on alloy, product form, section size, and incoming condition
- Overaging or underaging can miss both strength and corrosion targets
- Solution treatment or quenching may distort thin and asymmetric parts
- A condition name does not replace material heat-lot traceability
The H900 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 | 477–493 °C (891–919 °F) — Primary solution or age temperature window represented by the stages; use the alloy-specific specification. |
|---|---|
| Soak | 1 h — At-temperature time; load and section corrections may apply. |
| Cooling | Still air |
| Atmosphere | Air / vacuum |
| Door to door | 2–5 h — Typical furnace cycle excluding queue and laboratory testing. |
Stages
- 1Solution treat to Condition A per product specification
- 2Age at 482 °C (900 °F) for 1 h
- 3Air cool to room temperature
What H900 does to the part
| Hardness | 40–47 HRC (375–444 HB) — Condition and product-form range; Brinell is commonly reported as 375–444 HB. |
|---|---|
| Section affected | The whole section transforms. |
| Tensile strength | ≥ 1,310 MPa — Minimum 1,310 MPa for 17-4 PH H900 under AMS 5643 / ASTM A564; product form and size limits apply. |
| Toughness | Highest strength of the listed 17-4 PH conditions, with lower ductility and stress-corrosion resistance than overaged conditions. |
| Distortion | Low risk. Small contraction is possible during aging; verify close fits. |
| Surface after treatment | Bright in vacuum or inert atmosphere; light heat tint in air. |
| Machining sequence | Machine in Condition A where practical, age, then finish-grind only the tightest features. |
Specifications for H900
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, Precipitation-Hardening Corrosion-Resistant and Maraging Steel Parts | Governing | — | Active |
Steel, Corrosion-Resistant, Bars, Wire, Forgings, Tubing, and Rings, 16Cr - 4.0Ni - 0.30Cb - 4.0Cu, Solution Heat Treated, Precipitation Hardenable | Governing | — | Active |
Standard Specification for Hot-Rolled and Cold-Finished Age-Hardening Stainless Steel Bars and Shapes | Alternative | — | Active |
Test and related methods: ASTM E18 (Standard Test Methods for Rockwell Hardness of Metallic Materials).
Drawing call-out
17-4 PH PER AMS 5643, CONDITION H900; AGE PER AMS 2759/3; HARDNESS 40–47 HRC PER ASTM E18Which alloys take H900?
Verdict per material family, with the grades that behave differently. Each family links to its datasheets in the material library. Typical grades: 17-4 PH (S17400), 15-5 PH (S15500).
| Material family | Verdict | Notes |
|---|---|---|
| Yes | Designed for martensitic precipitation-hardening stainless grades.
| |
| With care | Applicable to qualified additively manufactured 17-4 PH after the specified solution treatment.
| |
| No | This alloy category does not use the PH stainless cycle. | |
| No | This alloy category does not use the PH stainless cycle. | |
| No | This alloy category does not use the PH stainless cycle. | |
| No | This alloy category does not use the PH stainless cycle. | |
| No | This alloy category does not use the PH stainless cycle. | |
| No | This alloy category does not use the PH stainless cycle. | |
| No | This alloy category does not use the PH stainless cycle. | |
| No | This alloy category does not use the PH stainless cycle. | |
| No | This alloy category does not use the PH stainless cycle. | |
| No | This alloy category does not use the PH stainless cycle. | |
| No | This alloy category does not use the PH stainless cycle. | |
| No | This alloy category does not use the PH stainless cycle. | |
| No | This alloy category does not use the PH stainless cycle. | |
| No | This alloy category does not use the PH stainless cycle. |
Design rules for H900
What to decide on the drawing before the part goes to the heat treater.
- Machine the solution-treated Condition A part before aging where possible.The precipitation response depends on the material condition entering the age cycle.
- Keep heavy and thin sections thermally balanced in the load.Uniform temperature and controlled transfer reduce property variation and distortion.
- State the alloy, product specification, final condition, and hardness-test method on the drawing.A condition name alone does not define material pedigree or acceptance sampling.
- Protect finished dimensions and verify critical fits after treatment.Precipitation aging is low-distortion but can still produce measurable contraction or growth.
H900 versus the alternatives
Treatments engineers weigh against H900, and when each wins.
| Treatment | Hardness | Toughness | Stability | Cost | Choose it when |
|---|---|---|---|---|---|
H900 this page | 47 | 55 | 80 | $$ | — |
| 37 | 68 | 84 | $$ | when greater toughness and corrosion resistance justify lower strength |
Cost, lead time and applications
Relative cost
Q+T H900 is a standard-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 | 3–7 working days |
|---|---|
| Furnace time | 2–5 h |
What H900 is used for
- Aerospace structural hardware
- Precision shafts, fittings, and actuators
- High-strength tooling and fixtures
- Corrosion-resistant mechanical components
H900 — frequently asked
What does H900 mean?
H900 identifies a controlled solution-treatment and precipitation-aging condition, not a generic furnace temper. The drawing should also identify the alloy specification and acceptance hardness or tensile requirement.
Is this a quench-and-temper treatment?
No in the metallurgical sense. Strength comes primarily from fine precipitates formed during aging rather than tempering quenched carbon-steel martensite.
Will the part distort?
The expected risk is low. Aging is normally more stable than a hard steel quench, but residual stress, section changes, fixtures, and prior solution treatment still matter.
How should hardness be verified?
Use ASTM E18 for Rockwell hardness on a suitable flat section. The expected catalog range is 40–47 HRC; thin sections may require ASTM E384 microindentation and an approved conversion.
Can the condition be assigned after machining?
Usually yes when the starting material and process route are compatible. The purchase order must preserve traceability to the governing product specification and the heat treater must certify the complete cycle.