COMPREHENSIVE TECHNICAL ANALYSIS AND DATASHEET OF 15-5 PH (UNS S15500) FASTENING SYSTEMS
15-5 PH (Precipitation Hardening), officially designated as UNS S15500 or Type XM-12, is a martensitic, precipitation-hardening stainless steel. It was developed as a direct structural improvement over 17-4 PH. By precisely adjusting the chromium and nickel ratios and utilizing advanced melting practices (such as Consumable Electrode Remelting), 15-5 PH eliminates the delta ferrite stringers found in 17-4 PH.
This refined, ferrite-free microstructure gives 15-5 PH vastly superior transverse toughness, improved ductility, and better forging characteristics compared to its predecessor. Like 17-4, it can be aged at low temperatures to achieve phenomenal yield strengths without significant scaling or distortion. It is the premier choice for complex, high-stress aerospace fastening, marine engineering, and highly pressurized chemical reactor components where multidirectional load stresses are present.
■ Product Overview & Specifications
15-5 PH fasteners can be thermally treated to various conditions (H900 through H1150M) to precisely balance strength, hardness, and fracture toughness for specific engineering requirements.
| Material Classification | Precipitation-Hardening Martensitic Stainless Steel (Ferrite-Free) |
|---|---|
| UNS Designation | S15500 (XM-12) |
| Microstructure | Martensitic |
| Magnetic State | Strongly Magnetic |
| Density | ~7.80 g/cm³ (0.282 lb/in³) |
| Size Range | Metric: M6 to M100 | Imperial: 1/4" to 4" Custom hot-forged and precision-machined fasteners available. |
| Thread Types | UNC, UNF, 8UN, Metric Coarse, Metric Fine |
| Strengthening Method | Solution Annealing + Low-Temperature Ageing (Precipitation) |
■ Proprietary Datasheet Download (GATED)
Access professional-grade technical data for 15-5 PH, including detailed transverse impact strength charts, specific heat treatment parameters, and aerospace (AMS) specification cross-references.
15-5 PH (S15500) — Complete Technical Datasheet
Contains comprehensive transverse vs. longitudinal mechanical comparisons, specific thermal aging cycles, and critical anti-galling installation torques for AMS 5659 compliance.
⬇ DOWNLOAD DATASHEET■ MTC Integration Section
Due to its frequent use in critical aerospace and high-pressure environments, 15-5 PH requires rigorous metallurgical documentation mapping back to the remelt process.
- EN 10204 Type 3.1: Provides verified ladle chemistry, final condition mechanical properties (tensile, yield, elongation), and transverse reduction of area metrics to verify the absence of delta ferrite.
- EN 10204 Type 3.2: Third-party witness testing (e.g., Lloyds, DNV) available for critical structural offshore or high-pressure applications.
■ Chemical Composition (UNS S15500)
Compared to 17-4 PH, the Chromium is slightly reduced and Nickel is carefully controlled to prevent the formation of ferrite stringers, ensuring isotropic (uniform in all directions) mechanical properties.
| Chromium (Cr) | Nickel (Ni) | Copper (Cu) | Manganese (Mn) | Silicon (Si) | Columbium (Cb/Nb) + Ta | Carbon (C) |
|---|---|---|---|---|---|---|
| 14.0 – 15.5 | 3.50 – 5.50 | 2.50 – 4.50 | 1.00 Max | 1.00 Max | 0.15 – 0.45 | 0.07 Max |
*Phosphorus (0.040 Max) and Sulfur (0.030 Max) are restricted to maximize toughness and transverse ductility.
■ Mechanical Properties (By Common Heat Treatment Conditions)
The longitudinal strength values of 15-5 PH are nearly identical to 17-4 PH. Its distinct advantage lies in transverse testing, where it maintains high reduction of area and impact toughness.
| Property | Condition H900 (Max Strength) | Condition H1025 | Condition H1150 (Max Ductility) |
|---|---|---|---|
| Tensile Strength (Min) | 190 ksi (1310 MPa) | 155 ksi (1070 MPa) | 135 ksi (930 MPa) |
| Yield Strength (0.2% Offset, Min) | 170 ksi (1170 MPa) | 145 ksi (1000 MPa) | 105 ksi (725 MPa) |
| Elongation in 2" (Min) | 10% | 12% | 16% |
| Reduction of Area (Min) | 35% | 45% | 50% |
| Hardness (Rockwell C) | 40 HRC Min | 35 HRC Min | 28 HRC Min |
■ Equivalent Grades & Designations
| Standard / System | Designation |
|---|---|
| UNS Designation | S15500 |
| Common Trade Name | 15-5 PH, Type XM-12 |
| European Equivalent | EN 1.4545 / X5CrNiCu15-5 |
| ASTM Specifications | ASTM A564 Grade XM-12 |
| Aerospace Specs | AMS 5659 |
■ Applications & Industries
15-5 PH is specifically chosen when components are subjected to heavy loads from multiple directions, where standard 17-4 PH might risk brittle failure along longitudinal ferrite stringers.
- Aerospace & Aviation: Landing gear fastening, wing spars, engine mounts, and highly stressed internal aircraft fasteners.
- Marine & Subsea: High-stress boat shafting, heavy-duty marine hardware, and high-pressure subsea valves.
- Petrochemical: Reactor fastening systems, high-pressure pump shafts, and processing equipment subject to multidirectional stresses.
- Nuclear & Power Gen: Critical structural anchors and heavy-duty reactor component bolting.
■ Compatible Fastener Assemblies
To avoid severe thread galling, stainless-to-stainless fastening requires distinct material mating strategies and robust lubrication protocols.
| External Threads (15-5 PH Studs/Bolts) | Recommended Mating Component (Nuts) |
|---|---|
| 15-5 PH Condition H900 | 15-5 PH Heavy Hex Nuts (Strict lubrication/anti-seize mandatory) |
| 15-5 PH Any Condition | Nitronic 60 (UNS S21800) Nuts (Optimal for galling prevention) |
■ Torque & Installation Guidelines
The high yield strength of 15-5 PH permits extreme clamping forces. Premium anti-seize pastes (e.g., MoS2 or Nickel-based) are non-negotiable to prevent thread stripping or cold-welding during installation.
| Nominal Diameter | Threads Per Inch (UNC) | Target Torque (H900/H1025) — Lubricated (ft-lbs) |
|---|---|---|
| 1/2" | 13 | 65 - 80 |
| 5/8" | 11 | 130 - 150 |
| 3/4" | 10 | 230 - 270 |
| 1" | 8 | 550 - 650 |
■ Why Choose Ananka Group?
Ananka Group specializes in the precision manufacturing of severe-service, precipitation-hardening alloys.
- Advanced Melting Sourcing: We utilize Consumable Electrode Remelted (ESR/VAR) 15-5 PH stock to guarantee the highest purity and maximum transverse strength for aerospace and critical applications.
- In-House Heat Processing: Flawless execution of custom aging cycles (H900 to H1150M) directly managed by our internal metallurgical team.
- Full Traceability: 100% heat lot tracking mapped back to the original steel mill, ensuring absolute metallurgical authenticity.
- Custom CNC Machining: We manufacture fully custom drawings, 12-point bolts, double-end studs, and specialty structural pins.
■ Frequently Asked Questions
1. What is the fundamental difference between 15-5 PH and 17-4 PH?
While they have similar longitudinal strength and corrosion resistance, 15-5 PH is ferrite-free. 17-4 PH contains microscopic structures called "delta ferrite stringers" which can reduce strength across the grain (transverse direction). 15-5 PH eliminates these, providing excellent toughness and ductility in all directions.
2. Is 15-5 PH more expensive than 17-4 PH?
Yes. Because 15-5 PH typically requires a secondary melting process (like Vacuum Arc Remelting - VAR or Electroslag Remelting - ESR) to achieve its high purity and precise chemistry, it carries a premium over standard 17-4 PH.
3. Can 15-5 PH be used in corrosive saltwater environments?
15-5 PH has excellent corrosion resistance, comparable to 304 stainless steel. It performs well in atmospheric and mild marine environments. However, in stagnant or highly concentrated chloride (saltwater) conditions, it may pit. For extreme marine applications, Duplex or Super Duplex stainless steels are often preferred.
4. Does 15-5 PH require heat treatment after machining?
15-5 PH is typically supplied in "Condition A" (Solution Annealed), which is the best state for machining. Once machined, it must undergo a low-temperature aging cycle (e.g., 900°F for Condition H900) to achieve its final strength and hardness. This low-temp process causes virtually no scaling or distortion.