AMS 5629 - PH 13-8 Mo Stainless Steel Bars, Wire, Forgings & Rings (Condition A)
What is AMS 5629?
AMS 5629 is the SAE International aerospace material specification for PH 13-8 Mo stainless steel (UNS S13800) in the form of bars, wire, forgings, rings, and extrusions, supplied in Condition A (solution heat treated and annealed).
PH 13-8 Mo is a martensitic precipitation hardening (PH) stainless steel produced by Vacuum Induction Melting (VIM) followed by Vacuum Arc Remelting (VAR) or Electroslag Remelting (ESR) – also termed Consumable Electrode Melting (CEM). This double-melt process achieves the macro- and microcleanliness required for critical aerospace structural applications.
In Condition A, material per AMS 5629 achieves a minimum tensile strength of 130 ksi (896 MPa) and can be further precipitation hardened by the customer to H950 through H1150 aging conditions, reaching tensile strengths up to 220 ksi (1517 MPa) at H950.
AMS 5629 Available Forms and Stocked Sizes
AMS 5629 covers PH 13-8 Mo (UNS S13800) in wrought solid forms. The SAE/AMS definitions for covered product forms are:
Round, hexagonal, square, or rectangular solid cross-sections; typically 0.125″ and above in diameter or thickness
Round or profiled cross-section in coil or straightened form; typically under 0.500″ in diameter
Closed-die or open-die forgings, including near-net-shape aerospace structural parts; no thickness limitation
Rolled or forged ring forms, including seamless rings for frames and flanges
Solid or hollow extruded profiles
Fighter Jet Metals supplies PH 13-8 Mo per AMS 5629 in round bar starting at 0.125″ diameter up to 14.00″ diameter, supplied in Condition A (solution heat treated).
Custom cut-to-length, saw-cut sections, and trepanning available.
Applications of AMS 5629
Landing Gear Structures
- PH 13-8 Mo per AMS 5629 is widely used in aircraft landing gear for structural members including struts, trunnions, axles, and actuator cylinders. H1000 and H1025 are the most common aging conditions for landing gear applications, balancing high tensile strength (195–205 ksi) with fracture toughness requirements. The low carbon martensitic matrix provides superior transverse toughness compared to 17-4 PH at equivalent strength levels.
Aerospace Fasteners and Hardware
- The combination of high strength, good corrosion resistance, and dimensional stability after aging makes AMS 5629 bar stock the preferred material for aerospace fasteners including structural bolts, pins, studs, and locking hardware. H1000 is a common fastener condition, providing 205 ksi minimum tensile with 48% RA.
Aircraft Engine-Adjacent Structural Parts
- PH 13-8 Mo is used for airframe structural components near the engine bay and exhaust zones where both strength and oxidation resistance are required. The alloy is not a high-temperature engine alloy, but its performance at moderate elevated temperatures and its corrosion resistance make it suitable for nacelle structures, brackets, and support hardware.
Valve and Pump Components
- The corrosion resistance of PH 13-8 Mo (superior to 17-4 PH and 15-5 PH in many environments) combined with its ultra-high strength in the H950 condition makes it a preferred material for critical valve stems, pump shafts, and impellers in both aerospace fluid systems and industrial applications.
Plastic Injection Mold Components and Tooling
- High-hardness applications such as plastic injection mold cores and cavities utilize PH 13-8 Mo in the H950 condition (~47–48 HRC). The excellent polishability and dimensional stability after aging make it suitable for mold applications requiring fine surface finish.
Defense and Missile Components
- The ultra-high strength and dimensional stability of AMS 5629 PH 13-8 Mo make it suitable for missile structural components, fuse housings, and defense hardware where strength-to-weight ratio and corrosion resistance are simultaneously required.
Chemical Composition - AMS 5629
The following chemical composition limits are specified in AMS 5629 for PH 13-8 Mo (UNS S13800):
| Element | Symbol | Minimum % | Maximum % |
|---|---|---|---|
| Chromium | Cr | 12.25 | 13.25 |
| Nickel | Ni | 7.50 | 8.50 |
| Iron | Fe | Balance | - |
| Nitrogen | N | - | 0.010 |
| Molybdenum | Mo | 2.00 | 2.50 |
| Cobalt | Co | - | 1.00 |
| Titanium | Ti | - | 0.40 |
| Aluminum | Al | 0.90 | 1.35 |
| Carbon | C | - | 0.05 |
| Manganese | Mn | - | 0.10 |
| Silicon | Si | - | 0.10 |
| Phosphorus | P | - | 0.010 |
| Sulfur | S | - | 0.008 |
The nominal composition is 13Cr-8Ni-2Mo-1Al (balance Fe).
Chromium provides corrosion resistance and matrix strengthening. Nickel stabilizes the martensitic structure and improves toughness. Molybdenum increases corrosion resistance and solid-solution strength.
Aluminum is the primary precipitation hardening agent, forming NiAl (β’) precipitates during aging that produce the high-strength H conditions.
The tight limits on carbon (0.05% max), phosphorus (0.010% max), sulfur (0.008% max), and nitrogen (0.010% max) are critical to the VIM+VAR/ESR process specification.
Mechanical Properties - AMS 5629
Material supplied per AMS 5629 is in Condition A (solution heat treated). The minimum mechanical properties required in Condition A are:
| Property | Imperial | Metric |
|---|---|---|
| Tensile Strength (min) | 130 ksi | 896 MPa |
| Yield Strength, 0.2% offset (min) | 90 ksi | 620 MPa |
| Elongation in 2 in. (min) | 8% | 8% |
| Reduction of Area (min) | 35% | 35% |
| Hardness (max) | 38 HRC | ~363 HBN |
Precipitation Hardening Conditions - AMS 5629 PH 13-8 Mo (H950 through H1150)
Material received in Condition A per AMS 5629 can be age-hardened by the customer or processor to achieve higher strength.
Aging is performed by heating to the listed temperature for a minimum of 4 hours, followed by air cooling. The mechanical property minimums for each aging condition are:
| Condition | Aging Temp | Tensile (min) | Yield (min) | Elong (min) | RA (min) |
|---|---|---|---|---|---|
| H950 | 950°F (510°C) | (1517 MPa) | 205 ksi (1413 MPa) | 10% | 45% |
| H1000 | 1000°F (538°C) | 205 ksi (1413 MPa) | 190 ksi (1310 MPa) | 10% | 48% |
| H1025 | 1025°F (552°C) | 195 ksi (1344 MPa) | 180 ksi (1241 MPa) | 11% | 50% |
| H1050 | 1050°F (566°C) | 175 ksi (1207 MPa) | 160 ksi (1103 MPa) | 12% | 52% |
| H1100 | 1100°F (593°C) | 155 ksi (1069 MPa) | 145 ksi (1000 MPa) | 14% | 54% |
| H1150 | 1150°F (621°C) | 135 ksi (931 MPa) | 110 ksi (758 MPa) | 16% | 57% |
Physical Properties - AMS 5629
| Property | Value (Imperial) | Value (Metric) |
|---|---|---|
| Density | 0.277 lb/in³ | 7.67 g/cm³ |
| Melting Range | 2560°F–2630°F | 1404°C–1443°C |
| Modulus of Elasticity | 28.0 × 10⁶ psi | 193 GPa |
| Thermal Conductivity | 110 BTU·in/(hr·ft²·°F) | 15.9 W/(m·K) |
| Coefficient of Thermal Expansion | 6.0 µin/in/°F | 10.8 µm/m·°C |
| Specific Heat | 0.11 BTU/(lb·°F) | 460 J/(kg·K) |
Mill Producers
PH 13-8 Mo per AMS 5629 is produced by a small number of specialty steel producers due to the VIM+VAR/ESR melt requirement.
The primary producer in the United States is:
- Carpenter Technology Corporation : markets this alloy as Custom 13-8® (registered trade name); primary U.S. VIM+VAR producer
- Aubert & Duval : European producer, supplies European aerospace programs
- Böhler (voestalpine) : European VIM+VAR producer
All material supplied by Fighter Jet Metals is sourced from AS9100-certified mill producers with full chemistry and mechanical test certifications, heat and lot traceability, and conformance to AMS 5629.
AMS 5629 Machining Guidelines
PH 13-8 Mo should be machined in Condition A (solution heat treated, ~38 HRC max) before aging to the final H condition. Machining after aging to H950 (47+ HRC) significantly increases tool wear and reduces machinability.
- Use carbide (WC/Co) or high-speed steel tooling with sharp edges
- Use coolant : dry machining causes work hardening and accelerated tool wear
- Machinability rating: approximately 50–60% of 1212 free-machining steel (similar to 17-4 PH in Condition A)
- Avoid excessive tool pressure : PH stainless steels work-harden more than austenitic grades if tooling is dull
Weldability of AMS 5629
PH 13-8 Mo per AMS 5629 can be welded using conventional processes.
Preferred method is Gas Tungsten Arc Welding (GTAW / TIG) with inert argon shielding gas.
Key welding considerations:
- Filler wire: ER630 (17-4 PH chemistry) is a common choice for matching PH stainless filler. Direct match filler (13-8 PH chemistry) is available from specialty wire producers.
- Pre-heat: Generally not required for thin sections; for sections >1″ consider pre-heat to 50–100°F (10–38°C) to reduce thermal gradients.
- Post-weld heat treatment: For full mechanical properties recovery in the HAZ, re-solution anneal (return to Condition A) followed by re-aging to the required H condition is recommended.
- Avoid high heat input : excessive heat causes delta ferrite formation and reduces toughness.
- The low carbon content minimizes sensitization risk in the heat-affected zone.
AMS 5629 vs AMS 5864 - What's the Difference?
Both specifications cover PH 13-8 Mo stainless steel (UNS S13800) in Condition A. The difference is the product form:
| Property | AMS 5629 | AMS 5864 |
|---|---|---|
| Alloy | PH 13-8 Mo (UNS S13800) | PH 13-8 Mo (UNS S13800) |
| Product Forms | Bars, Wire, Forgings, Rings, Extrusions | Sheet, Strip, Plate |
| Condition | Condition A (Solution Heat Treated) | Condition A (Solution Heat Treated) |
| Chemistry | Same as AMS 5864 | Same as AMS 5629 |
| Melt Practice | VIM + VAR or ESR | VIM + VAR or ESR |
| Typical Applications | Landing gear struts, structural fasteners, pump shafts | Structural panels, bulkheads, tooling plates |
Use AMS 5599 for standard Nickel 625 sheet and plate procurement.
Specify AMS 5879 only where low-cycle fatigue or bellows/expansion joint applications require the tighter processing controls.
Melt Practice - AMS 5629
AMS 5629 requires a double-melt process:
Vacuum Induction Melting (VIM) followed by either Vacuum Arc Remelting (VAR) or Electroslag Remelting (ESR). VIM removes dissolved gases and produces a tightly controlled chemical composition.
The secondary melt (VAR or ESR) further refines the microstructure, reduces segregation, and achieves the macro- and microcleanliness specified by the aerospace industry for landing gear, structural, and engine-adjacent applications.
The low carbon content (0.05% max) combined with this controlled melt practice produces outstanding transverse toughness and uniform mechanical properties in heavy sections – a critical requirement for large-diameter bars and forgings used in aircraft structural components.
What is Condition A? (AMS 5629 Solution Heat Treatment)
Material supplied per AMS 5629 is in Condition A, which is the solution heat treated and annealed state. The solution heat treatment consists of:
1. Heat to 1700°F ± 25°F (927°C ± 14°C)
2. Hold for sufficient time to achieve temperature uniformity
3. Air cool or faster cooling
In some processes, a second anneal step at ~1100°F (593°C) is performed to reduce retained austenite and ensure full martensitic transformation before aging.
- Condition A material is:
- In the martensitic structure (not austenitic – PH 13-8 Mo transforms to martensite on cooling, unlike austenitic stainless steels)
- Machinable (hardness max 38 HRC – roughly 65 HRB equivalent)
- Ready for customer-applied precipitation hardening to the desired H condition
- Not yet at full design strength – aging is required to reach H950–H1150 properties
Do not confuse Condition A with fully softened or annealed austenitic stainless steels.
PH 13-8 Mo in Condition A is already higher strength than most annealed austenitic grades due to the martensitic matrix.
Cross-Reference Specifications - AMS 5629
Sheet, Strip & Plate
Different product form of the same alloy. AMS 5629 covers bars, wire, forgings, rings, and extrusions. AMS 5864 covers the flat-rolled forms.
BARS & FORGINGS
ASTM-system specification for PH 13-8 Mo bars and shapes, providing an alternate standard-body procurement path to the SAE AMS system.
BOEING SPECIFICATIONS
Boeing-approved PH 13-8 Mo for airframe, landing gear, and structural applications. DMS specifications originated at McDonnell Douglas, now administered by Boeing.
Honeywell Specifications
Covers PH 13-8 Mo used in Honeywell aerospace engine and airframe applications, focusing on high-strength bar and forging stock.
Precipitation Hardening Conditions
Age-hardening conditions applied to AMS 5629 Condition A base material to achieve full design strength.
Non-Destructive Testing
Ultrasonic inspection standard for AMS 5629 bars, forgings, and rings when NDE is required by contract.
Trade Names and Equivalent Designations
| Designation | System | Notes |
|---|---|---|
| PH 13-8 Mo | Industry (generic) | Describes precipitation hardening, 13% Cr, 8% Ni, Mo addition |
| Custom 13-8 | Carpenter Technology | Registered trade name; Carpenter is the primary U.S. mill producer |
| XM-13 | ASTM | ASTM designation for this alloy system |
| UNS S13800 | SAE / ASTM | Unified Numbering System designation |
| DIN 1.4534 | European (DIN) | German/European material number |
| W.Nr. 1.4534 | European (Werkstoffnummer) | German/European material number |
| 13-8 PH | Industry (informal) | Reversed convention; same alloy |
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
Complete heat-lot traceability
Full chain-of-custody documentation from mill to your door
AS9100-certified aerospace sourcing
Material from AS9100-certified mills only
OEM specification support
Stock and supply to Boeing BMS/DMS, Gulfstream GMS, Honeywell EMS, Safran DMD, and Airbus AIPS requirements
In-house processing
Plate saw cutting, shearing, and laser cutting available; custom-cut sizes to your dimensions
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.