AMS 5659 - 15-5 PH Stainless Steel Bars, Wire, Forgings & Rings (Condition A)
What is AMS 5659?
AMS 5659 is the SAE International specification for [15-5 PH stainless steel](/stainless-steel/15-5-ph/) (UNS S15500) in long product forms: bars, wire, forgings, rings, and extrusions, delivered in Condition A (solution heat treated).
The alloy is a martensitic precipitation hardening stainless steel with a nominal composition of 15% chromium, 5% nickel, and 3% copper, balanced with iron and a small addition of columbium (niobium).
AMS 5659 bars and forgings are supplied in Condition A so the end user or heat treater can machine the material to near-net shape and then apply a precipitation hardening cycle (H900 through H1150) to achieve the target mechanical properties for the finished component.
Typical applications include structural airframe fittings, landing gear components, shafts, hydraulic actuators, fastener blanks, and precision machine components throughout commercial and military aerospace programs.
AMS 5659 Available Forms and Stocked Sizes
AMS 5659 covers UNS S15500 in long product forms. The SAE/AMS definitions for the product forms covered by this specification are:
Round, square, flat, and hexagonal cross-sections; Condition A
Coiled or straight lengths; Condition A
Closed-die or open-die forgings; Condition A; custom shapes per customer drawing
Rolled or forged rings; Condition A; used for flanges, valve bodies, and pressure vessel components
Extruded shapes and profiles; Condition A
Applications of AMS 5659
Structural Airframe Fittings and Brackets
- AMS 5659 bar in Condition A is the preferred material for precision machined structural fittings – wing attachment brackets, spar fittings, seat track fittings, door hinges, and other structural connections. The material is machined in Condition A, then aged to H925 or H1025 to develop final tensile strength and fatigue resistance. The result is a corrosion-resistant structural fitting with mechanical properties comparable to other PH stainless grades in H900 condition.
Landing Gear and Actuation Components
- The combination of high strength, corrosion resistance, and machinability makes AMS 5659 a standard specification for landing gear components. Axles, torque links, drag braces, and actuator bodies are routinely produced from AMS 5659 bar and forging stock. H900 and H925 aging conditions are commonly specified for these applications where peak strength and hardness are required. The alloy’s resistance to stress corrosion cracking in H925 and higher conditions makes it preferable to higher-strength carbon steels for landing gear in marine or salt-fog environments.
Fasteners and Precision Machined Parts
- AMS 5659 wire and bar are used as the starting material for aerospace fastener blanks (bolt bodies, stud bolts, and hex head fasteners). The wire form allows cold heading to produce near-net fastener blanks, which are then aged. Precision machined shafts, valve bodies, pump housings, hydraulic manifolds, and fuel system components are also produced from AMS 5659 bar – the corrosion resistance of UNS S15500 eliminates the plating steps required for low-alloy steel equivalents.
Defense and Marine Structural Applications
- AMS 5659 is used in naval and submarine structural hardware, weapons system components, and defense electronics housings where stainless corrosion resistance combined with high strength is required. The predictable aging response and tight chemistry control under AMS 5659 make the material traceable for defense program qualification.
Chemical Composition - AMS 5659
The following chemical composition limits apply to UNS S15500 per AMS 5659:
| Element | Symbol | Minimum % | Maximum % |
|---|---|---|---|
| Chromium | Cr | 14.00 | 15.50 |
| Nickel | Ni | 3.50 | 5.50 |
| Iron | Fe | Balance | - |
| Copper | Cu | 2.50 | 4.50 |
| Columbium + Tantalum | Nb+Ta | 0.15 | 0.45 |
| Carbon | C | - | 0.07 |
| Manganese | Mn | - | 1.00 |
| Silicon | Si | - | 1.00 |
| Phosphorus | P | - | 0.040 |
| Sulfur | S | - | 0.030 |
Mechanical Properties - AMS 5659 - Condition A
AMS 5659 specifies minimum mechanical properties for bars delivered in Condition A (solution heat treated).
Condition A material has not yet been precipitation hardened; the values below represent the as-delivered condition from the mill, before the customer applies a final aging cycle.
The values in the table below are specification minimums for standard bar cross-sections per AMS 5659 (SAE International, current revision). Actual certified mill test report values are typically above the listed minimums.
| Property | Imperial | Metric |
|---|---|---|
| Tensile Strength (min) | 160 ksi | 1103 MPa |
| Yield Strength, 0.2% offset (min) | 120 ksi | 827 MPa |
| Elongation in 2 in. (min) | 5% | 5% |
| Reduction of Area (min) | 25% | 25% |
| Hardness (max) | 38 HRC | 38 HRC |
AMS 5659 Precipitation Hardening Conditions
AMS 5659 bars are delivered in Condition A (solution heat treated).
The customer then applies a precipitation hardening heat treatment to develop final mechanical properties.
The standard aging conditions for UNS S15500 per AMS 2759/1 and industry practice are listed below.
These H-condition designations correspond to the aging temperature in degrees Fahrenheit.
| Condition | Aging Temp | Aging Time | Tensile (min) | Yield (min) | Elong (min) | RA (min) |
|---|---|---|---|---|---|---|
| H900 | 900°F (482°C) | 1 hour + air cool | 190 ksi (1310 MPa) | 170 ksi (1172 MPa) | 10% | 44% |
| H925 | 925°F (496°C) | 4 hours + air cool | 180 ksi (1241 MPa) | 165 ksi (1138 MPa) | 10% | 44% |
| H1025 | 1025°F (552°C) | 4 hours + air cool | 155 ksi (1069 MPa) | 145 ksi (1000 MPa) | 12% | 45% |
| H1075 | 1075°F (579°C) | 4 hours + air cool | 145 ksi (1000 MPa) | 125 ksi (862 MPa) | 13% | 45% |
| H1100 | 1100°F (593°C) | 4 hours + air cool | 140 ksi (965 MPa) | 115 ksi (793 MPa) | 14% | 45% |
| H1150 | 1150°F (621°C) | 4 hours + air cool | 135 ksi (931 MPa) | 105 ksi (724 MPa) | 16% | 50% |
Physical Properties - AMS 5659
| Property | Value (Imperial) | Value (Metric) |
|---|---|---|
| Density | 0.284 lb/in³ | 7.87 g/cm³ |
| Melting Range | 2560°F–2625°F | 1404°C–1440°C |
| Modulus of Elasticity | 28.0 × 10⁶ psi | 193 GPa |
| Thermal Conductivity (room temperature) | 91 BTU·in/(hr·ft²·°F) | 13.1 W/(m·K) |
| Coefficient of Thermal Expansion (68–212°F / 20–100°C) | 5.9 × 10⁻⁶/°F | 10.6 × 10⁻⁶/°C |
| Specific Heat (room temperature) | 0.11 BTU/(lb·°F) | 460 J/(kg·K) |
| Electrical Resistivity | 455 µΩ·in | 11.6 µΩ·cm |
Approved Mill Producers
Fighter Jet Metals sources AMS 5659 bar and forging stock from AS9100-certified mill producers. All material is supplied with full mill certifications, heat/lot numbers, chemical analysis reports, and mechanical test certifications traceable to the originating mill heat.
Machining AMS 5659
AMS 5659 bar stock in Condition A has a machinability rating of approximately 45–50% relative to B1112 (free-machining carbon steel baseline = 100%).
The Condition A hardness (max 38 HRC) is significantly lower than the hardened H900–H925 conditions, which is why all machining and drilling operations are performed before final aging.
The standard machining approach for AMS 5659 components is:
1. Receive AMS 5659 bar in Condition A
2. Rough machine to near-net shape (leave 0.010–0.020 inch stock for final machining)
3. Inspect dimensions and surface quality
4. Send to heat treater for precipitation hardening (H900, H925, H1025 as specified on drawing)
5. Return from heat treater (dimensional change is minimal – typically less than 0.001 in/in)
6. Finish machine to final print dimensions
7. Final inspection
Tooling recommendations for Condition A machining:
- Carbide tooling recommended : for production runs; high-speed steel (HSS) acceptable for prototyping
- Cutting speeds: 200–350 SFM with carbide
- Feed rates: Consistent with other 300-series and PH stainless steels
- Use : positive rake carbide inserts with TiAlN or TiCN coating
- Use flood coolant : UNS S15500 work-hardens at the cutting edge with interrupted cuts
- Avoid dwelling or rubbing at the cutting edge: maintain a consistent feed rate
Sulfurized cutting oils are effective for tapping and drilling. Thread milling is preferred over tapping for blind holes in the hardened condition.
Weldability of AMS 5659
AMS 5659 bar and forging stock is weldable.
All welding is performed in Condition A (before precipitation hardening), using filler metal matched to the base alloy or an austenitic filler for reduced crack susceptibility.
Key weldability considerations:
- Filler metal: AWS A5.9 ER630 wire (17-4 PH chemistry) is commonly used for GTAW (TIG) welding. Austenitic fillers such as ER308L or ER316L are also used where joint strength can be sacrificed for reduced heat input sensitivity.
- Pre-heat: Not required for most wall thicknesses. May be used for sections above 1.00 inch to reduce thermal gradient.
- Post-weld heat treatment: Weld joints are typically solution annealed (re-solution treated at ~1900°F / 1038°C) before precipitation hardening to relieve residual stresses and restore Condition A properties in the weld heat-affected zone. Where re-solution treatment is not possible, aging in place at H1150 is the minimum requirement to stabilize the weld microstructure.
- Hydrogen risk: VAR-produced AMS 5659 bar has very low dissolved hydrogen; no special hydrogen bake is required for most weld applications.
- Design consideration: Avoid highly restrained weld joints on parts that will be aged to H900 – the very high strength combined with residual weld stress can reduce fatigue life.
AMS 5659 vs AMS 5862 - What Is the Difference?
Both AMS 5659 and AMS 5862 cover UNS S15500 with the same chemical composition and both are supplied in Condition A.
The sole difference is the product form:
AMS 5659 covers long products (bars, wire, forgings, rings, extrusions); AMS 5862 covers flat-rolled products (sheet, strip, and plate).
| Property | AMS 5659 | AMS 5862 |
|---|---|---|
| Alloy (UNS) | S15500 (15-5 PH) | S15500 (15-5 PH) |
| Product Forms | Bars, Wire, Forgings, Rings, Extrusions | Sheet, Strip, Plate |
| As-Delivered Condition | Condition A (Solution Heat Treated) | Condition A (Solution Heat Treated) |
| Nominal Composition | 15Cr-5Ni-3Cu-0.3Cb | 15Cr-5Ni-3Cu-0.3Cb |
| Melt Practice | Declared on certification (VAR common) | Declared on certification (VAR common) |
| Typical Applications | Structural fittings, shafts, fastener blanks, forgings | Engine bay sheet metal, structural panels, formed brackets |
| Typical Processing Route | Machine → Age (H900–H1150) | Form / stamp → Age (H900–H1150) |
If your drawing or purchase order calls for 15-5 PH stainless steel in bar, rod, forging, ring, or extrusion form, AMS 5659 is the applicable specification.
If the requirement is sheet, strip, or plate, the applicable specification is AMS 5862.
Both specifications use the identical chemistry, so a bar cut from AMS 5659 plate and an AMS 5862 sheet cut from the same heat are chemically equivalent; the specifications differ in product form, mechanical test requirements, and documentation requirements.
AMS 5659 Melt Practice
AMS 5659 requires the melt practice to be identified and declared on the certified mill test report.
Standard practice for aerospace-grade AMS 5659 bar is Electric Arc Furnace (EAF) with Argon Oxygen Decarburization (AOD) followed by Vacuum Arc Remelting (VAR), or Vacuum Induction Melting (VIM) followed by VAR.
VAR remelting eliminates residual hydrogen, reduces sulfur, oxygen, and nitrogen content, produces a more homogeneous ingot, and improves transverse toughness – all of which are critical for bars and forgings used in flight-critical structural applications.
The melt practice code is reported on the certification document as required by AMS 5659.
When source control drawings or purchase orders specify “VAR” or “CVM” (Consumable Vacuum Melting), the supplier must furnish mill certifications that specifically identify a VAR or equivalent remelt step. Always verify the melt practice statement on the certified mill test report before procurement for flight-critical programs.
Fighter Jet Metals supplies AMS 5659 bar and forging stock from North American mills with full certification packages including heat analysis, product analysis, mechanical test data, and melt practice identification.
What Is Condition A for AMS 5659?
Condition A is the as-delivered heat treatment state specified by AMS 5659.
It means the bar, forging, or ring has been solution heat treated at approximately 1900°F (1038°C) and then air or oil quenched to produce a martensitic microstructure.
In this condition, the material is machinable, has moderate strength (160 ksi tensile minimum), and is ready for further processing by the customer.
Condition A is not the final service condition for most AMS 5659 applications.
After machining, forming, or welding, the finished component is typically sent to a heat treater for precipitation hardening (aging) at one of the standard H-condition temperatures listed above.
The aging cycle causes the copper-niobium precipitates to form within the martensite matrix, raising tensile strength significantly – from 160 ksi in Condition A to 190 ksi minimum in H900, for example – while retaining good toughness and dimensional stability.
Key characteristics of AMS 5659 Condition A material:
- Solution heat treated and quenched – martensitic microstructure established
- Hardness maximum 38 HRC – machinable with standard tooling
- Low distortion risk during machining compared to hardened material
- Can be straightened, re-machined, and re-inspected before final aging
- Welding (if required) is performed in Condition A before final aging
AMS 5659 specifies the Condition A requirements for the as-delivered product.
The final aged-condition requirements are specified by the engineering drawing or the applicable heat treatment specification (AMS 2759/1 or similar).
AMS 5659 Cross-Reference Specifications
Trade Names and Equivalent Designations
UNS S15500 covered by AMS 5659 is marketed and registered under several trade names and technical designations.
The table below lists the most common equivalents for procurement, design, and traceability purposes.
| Designation | System | Notes |
|---|---|---|
| AMS 5659 | SAE/AMS Specification | SAE International |
| S15500 | ASTM / SAE | UNS Number |
| Type XM-12 | ASTM Type Designation | ASTM A564 (Bars & Shapes) |
| Custom 15-5 PH® | Carpenter Trade Name | Carpenter Technology Corporation |
| 1.4545 | European DIN | DIN / EN |
| X5CrNiCuNb15-5 | European EN | EN 10088 |
| MIL-S-22216 | Military Specification | U.S. Military (largely superseded) |
Why Source AMS 5629 from Fighter Jet Metals?
Full mill certifications on every order
Heat number, lot number, chemical analysis, and mechanical test reports included with every shipment
Aerospace-only focus
every bar and forging we supply is procured for flight-critical programs; no commercial-grade substitution
AS9100-certified aerospace sourcing
Material from AS9100-certified mills only
Saw cutting services
cut-to-length to ±0.030″; no need to purchase full bars
In-stock AMS 5659 bar from 0.125″ to 14.00
no minimum order quantity on cut lengths
Same-day quote response
Competitive pricing with rapid quote turnaround
Certified Material for Critical Service
Materials supplied in 6Al-4V titanium must meet strict aerospace certification and traceability requirements. Fighter Jet Metals supports sourcing across a wide range of AMS, MIL, and OEM specifications, ensuring compliance with industry standards.
All material is supplied with full mill certifications, complete heat-lot traceability, and detailed documentation. This ensures reliability and suitability for safety-critical aerospace, defense, and high-performance engineering applications.