# 15-5 PH stainless steel

UNS S15500 precipitation-hardening stainless: product forms, aging conditions, property evidence and fabrication limits.

Reviewed: 2026-11-01

Tags: materials, stainless-steel, precipitation-hardening

## Identity and purchase definition

ARMCO's **15-5 PH VAC CE** bulletin gives **1,276 MPa yield for H900** and **862 MPa for H1150**. The **414 MPa** difference is **32.4% of the H900 value**. Both are typical longitudinal 0.2% yield results at an intermediate test location, averaged from production-order qualification tests. Use the required condition and sampling location for acceptance. [ARMCO July 2022 bulletin, table 4](https://www.aksteel.nl/files/downloads/clf_datasheet_armco_15-5_ph_pdb_euro_072022_93.pdf#page=1)

15-5 PH is a martensitic precipitation-hardening stainless steel, UNS S15500. The grade name is not a complete material specification: identify the producer, product form, dimensions, remelting requirements and final heat-treatment condition. ATI lists chromium 14.0–15.5%, nickel 3.50–5.50%, copper 2.50–4.50% and carbon at most 0.07% by mass for its product. These composition limits are different information from a typical heat analysis. [ATI, 15-5 product page](https://www.atimaterials.com/products/Pages/ati-15-5.aspx)

ATI's form-specific listings associate bar with AMS 5659 and ASTM A564/A564M, and plate, sheet and strip with ASTM A693, ASME SA-693 and AMS 5862. A specification listing does not establish that an arbitrary size, condition or shipment meets every listed standard. Order the required edition and certification explicitly. [ATI, specifications by form](https://www.atimaterials.com/products/Pages/ati-15-5.aspx)

Keep the alloy separate from proprietary variants. ARMCO 15-5 PH VAC CE is a named vacuum-arc-remelted product; its bulletin also describes ESR supply. Do not assume all S15500 stock has the same melt route, inclusion population or transverse qualification. [Cliffs/AK Steel International, ARMCO 15-5 PH VAC CE bulletin, July 2022](https://www.aksteel.nl/files/downloads/clf_datasheet_armco_15-5_ph_pdb_euro_072022_93.pdf#page=1)

## Condition A and aging

“Annealed” needs care here. ATI describes Condition A as solution heat treated, with a martensitic structure after cooling. It is not equivalent to a soft, fully austenitic stainless condition. ATI generally advises against placing its annealed material directly into service because untempered martensite has less favorable ductility and embrittlement behavior than aged material. [ATI technical data sheet, version 1, March 15, 2012](https://www.atimaterials.com/Products/Documents/datasheets/stainless-specialty-steel/precipitationhardening/ati_15-5_tds_en_v2.pdf#page=1)

The ARMCO bulletin's aging examples, starting with the required solution-treated material, include H900 at 482°C for one hour and H1150 at 621°C for four hours, followed by air cooling. Its H1150-M treatment is a separate two-stage schedule, not another spelling of H1150. These are producer treatment descriptions, not a substitute for the ordered heat-treatment specification and section-dependent process control. [ARMCO bulletin, table 1](https://www.aksteel.nl/files/downloads/clf_datasheet_armco_15-5_ph_pdb_euro_072022_93.pdf#page=1)

The condition number refers to an aging temperature in degrees Fahrenheit; it is not a service-temperature rating. Record the complete sequence, including any re-solution treatment after forming or joining. A furnace setpoint alone does not document that the required material temperature, holding time and cooling sequence were achieved.

## Bounded property example

The ARMCO bulletin's table 4 gives **typical longitudinal properties at an intermediate test location**, representing averages of production-order qualification tests:

| Condition | Tensile strength | 0.2% yield strength | Elongation in 4D₀ |
| --- | ---: | ---: | ---: |
| H900 | 1379 MPa | 1276 MPa | 14% |
| H1150 | 1000 MPa | 862 MPa | 19% |

These are typical results, not universal minima or properties at every location. Preserve orientation and sampling position when transferring data. [ARMCO bulletin, table 4 and footnote](https://www.aksteel.nl/files/downloads/clf_datasheet_armco_15-5_ph_pdb_euro_072022_93.pdf#page=1)

Use specification minima for a design basis only after confirming the applicable form, section, orientation and test requirements. Preserve elongation gauge length and impact-test temperature with those results; neither is an interchangeable descriptor of “toughness.”

## Corrosion and fabrication limits

ATI reports corrosion resistance comparable to Type 304 in many media, while warning that peak-strength conditions are more susceptible to stress-corrosion cracking. For chloride-SCC exposure it recommends the lowest hardness compatible with the required properties. This is conditional guidance, not equivalence to 304 for every chemical environment. ATI also describes limited severe-forming capability and notes that overaged material can be easier to form. [ATI technical data sheet, corrosion and formability sections](https://www.atimaterials.com/Products/Documents/datasheets/stainless-specialty-steel/precipitationhardening/ati_15-5_tds_en_v2.pdf#page=1)

For welding, ATI states that postweld heat treatment is needed to obtain the selected precipitation-hardened properties. Matching filler can respond to aging; an austenitic nonmatching filler does not acquire the same precipitation-hardening response. Qualify the complete joint rather than assigning parent-metal properties to the weld. [ATI technical data sheet, weldability](https://www.atimaterials.com/Products/Documents/datasheets/stainless-specialty-steel/precipitationhardening/ati_15-5_tds_en_v2.pdf#page=1)

Document fluid composition, chloride exposure, temperature, applied and residual stress, surface condition and cleaning operations before claiming suitability. For dimensional planning, identify when finish machining, joining and final aging occur. Keep inspection allowances and acceptance criteria in the manufacturing route; “low-temperature aging” does not itself guarantee zero movement or a conforming final dimension.

## Wrought material versus additive manufacture

Carpenter's PowderRange 15-5PH guidance describes an L-PBF-specific route involving homogenization or HIP, solution treatment and aging. It discusses porosity and anisotropy as process considerations. These requirements demonstrate why a powder designation cannot establish wrought-equivalent finished-part performance: retain build parameters, orientation, densification and post-treatment history with the qualification results. Do not transfer a wrought table directly to an as-built component. [Carpenter Additive, PowderRange 15-5PH process guidance](https://www.carpenteradditive.com/datasheet-powderrange-15-5ph)

## Supply and acceptance record

A March 31, 2025 AK Steel International announcement describes expanded European sheet inventory compliant with ASTM A693 and AMS 5862. It is evidence of that supplier's stocking program, not proof of global availability or qualification of a particular delivery. [AK Steel International, sheet-stock announcement](https://www.aksteel.eu/events-news/news/2025-03-31-expansion-of-our-15-5-ph-stock-program-348/?start=10)

For each purchase or material record, retain grade/specification edition, form and size, melt route where required, supplied condition, required final condition, heat identity and inspection certificate. Attach the governing mechanical, corrosion and nondestructive inspection requirements. Treat an unapproved condition change, alternative remelt route or additive substitution as a review item rather than a naming correction.

## Source applicability

The ARMCO bulletin is printed July 2022. ATI's PDF is printed version 1, March 15, 2012, despite its URL ending in “v2”; its historical tables do not prove the requirements of a later specification revision. The current web product listings and Carpenter page have no verified printed revision date. Confirm contract-required editions with the supplier.

See also [grades, tempers and conditions](../grades-tempers-and-conditions.md).