BMS 7-240 - 15-5PH Stainless Steel Sheet, Strip & Plate (Electro-Slag Remelted, Condition A / H-Condition)
What is AMS BMS 7-240?
BMS 7-240 is a Boeing Material Specification (BMS) for 15-5PH stainless steel (UNS S15500), a martensitic precipitation-hardenable iron-chromium-nickel-copper-niobium stainless steel, supplied in the forms of sheet, strip, and plate.
Material procured under BMS 7-240 must be produced by electro-slag remelting (ESR), which controls delta ferrite content and inclusion size and morphology to levels not achievable by conventional air-melt or standard vacuum arc remelting practice for this alloy system.
The defining characteristic of BMS 7-240 15-5PH relative to 17-4PH (AMS 5604) is superior through-thickness (short transverse) toughness, achieved by the suppression of delta ferrite through ESR processing and controlled inclusion morphology.
15-5PH per BMS 7-240 is supplied in the Condition A (solution annealed) state or in a customer-specified H-condition (H900 through H1150) and offers tensile strengths from 115 ksi (793 MPa) in Condition H1150 to a minimum of 190 ksi (1310 MPa) in Condition H900. Boeing plate thickness range under BMS 7-240 is 0.1875″ to 6.50″ thick; sheet and strip forms are also covered.
15-5PH per BMS 7-240 is the Boeing standard for structural sheet metal and plate components in commercial and military aircraft programs requiring precipitation-hardenable stainless steel with verified short-transverse toughness and full Boeing quality documentation traceability.
BMS 7-240 Available Forms and Stocked Sizes
15-5PH stainless steel sheet per BMS 7-240 in Condition A (solution annealed) or customer-specified H-condition. Supplied in thicknesses below 0.1875″ (4.76 mm), standard widths to 48″ (1219 mm) or custom widths, standard mill lengths or cut to order. All sheet supplied with full CMTR documenting ESR melt practice, solution anneal or age heat treatment records, and chemical and mechanical certifications.
15-5PH stainless steel strip per BMS 7-240 in Condition A or H-condition. Narrow flat-rolled product in widths below 24″ (610 mm), in coil or cut lengths, for precision aerospace stamping and forming operations. Verify specific strip widths, thicknesses, and tolerances with Fighter Jet Metals.
15-5PH stainless steel plate per BMS 7-240 in Condition A or customer-specified H-condition. Stocked in thicknesses from 0.1875″ (4.76 mm) to 6.50″ (165.1 mm), widths up to 60″ (1524 mm), and mill-length plates. Plate is the dominant product form under BMS 7-240 for precision-machined Boeing structural fittings and thick structural brackets. Full CMTR package includes ESR melt practice documentation, chemistry (spectrographic per heat), anneal and age heat treatment records, and mechanical test certifications.
Applications of BMS 7-240
Boeing Aircraft Structural Applications
- Commercial and military aircraft structural sheet metal components – the primary application of BMS 7-240 is Boeing-specified structural airframe sheet metal for both wide-body and narrow-body commercial aircraft programs; 15-5PH per BMS 7-240 in the H925 condition provides 170 ksi tensile in a fully corrosion-resistant stainless steel without protective coating requirements, enabling weight-efficient structural panels, formed sheet metal fittings, and press-brake-formed structural channels in areas exposed to the aircraft operating environment
- Aircraft structural plate for thick machined fittings and lugs – BMS 7-240 plate up to 6.50″ thick provides through-thickness toughness for large-section plate machined into structural lugs, fittings, clevises, and attach brackets where 17-4PH (AMS 5604) does not meet the short-transverse toughness requirements; ESR-controlled low delta ferrite eliminates ferrite-direction fracture anisotropy in thick plate cross-sections
- Precision machined structural components from plate – BMS 7-240 plate machined into complex structural fittings, pressure bulkhead frames, and structural support brackets for Boeing aircraft programs requiring the combination of high strength, corrosion resistance, and through-thickness property consistency from surface to center across the full plate thickness range (0.1875″ to 6.50″)
- Flight control surface structural components – BMS 7-240 sheet and plate for Boeing-specified flight control structural hardware: flap fittings, actuator support brackets, and structural attach elements requiring precipitation-hardened stainless with full Boeing material documentation and ESR certification
- Hydraulic and pressurized system structural support plates – Boeing structural plate for hydraulic line support structures, pressurized system support brackets, and structural manifolds where the combination of corrosion resistance, strength, and through-thickness toughness is required in an ESR-certified material
Industrial and Non-Boeing Aerospace Applications
- Aerospace structural sheet metal and plate for programs that specify 15-5PH sheet/plate in ESR condition for through-thickness toughness – procurement to AMS 5862 (the SAE equivalent) when BMS 7-240 Boeing-specific documentation is not required
- High-strength corrosion-resistant structural plate applications in chemical processing, marine, and oil-and-gas sectors requiring ESR-quality PH stainless steel with verified delta ferrite control and short-transverse mechanical properties
Defense Aircraft Applications
- Military Boeing aircraft structural plate and sheet metal components on fighter, bomber, and rotorcraft programs that specify BMS 7-240 on engineering drawings – full Boeing specification compliance with ESR certification required for defense Boeing platform supply chain qualification
- Defense pressure vessel plates and structural casings requiring 15-5PH PH stainless in ESR conadition with confirmed delta ferrite control for short-transverse fracture-critical applications
Chemical Composition - BMS 7-240
| Element | Symbol | Minimum % | Maximum % |
|---|---|---|---|
| Iron | Fe | Balance | - |
| Chromium | Cr | 14.0 | 15.5 |
| Nickel | Ni | 3.5 | 5.5 |
| Niobium + Tantalum | nb+Ta | 0.15 | 0.45 |
| Phosphorus | P | - | 0.040 max |
| Carbon | C | - | 0.07 max |
| Manganese | Mn | - | 1.00 max |
| Silicon | Si | - | 1.00 max |
| Copper | Cu | 2.5 | 4.5 |
| Sulfur | S | - | 0.030 max |
Chromium (14.0–15.5%) the “15” in 15-5PH, lower than 17-4PH: Chromium provides corrosion resistance and forms the passive oxide film that defines stainless steel behavior.
The nominal 15% chromium in 15-5PH is intentionally lower than the nominal 17% in 17-4PH. This reduction in chromium content, combined with the corresponding increase in nickel, is the key compositional change that suppresses delta ferrite formation in 15-5PH relative to 17-4PH.
Chromium is a strong ferrite stabilizer – reducing Cr from 17% to 15% moves the alloy further into the austenite + martensite phase field on solidification, reducing the tendency to form delta ferrite.
The 15% Cr level still provides full corrosion resistance adequate for Boeing aerospace structural applications in ambient atmospheric environments.
Nickel (3.5–5.5%) the “5” in 15-5PH, higher than 17-4PH: Nickel is an austenite stabilizer.
The increased nickel content in 15-5PH (compared to 17-4PH’s 3.0–5.0% range) works in combination with the lower chromium to favor austenite formation over delta ferrite during solidification.
The result is a fully martensitic microstructure after solution annealing with minimal residual delta ferrite.
Nickel also contributes to improved toughness and corrosion resistance, particularly in reducing environments and chloride-containing environments relative to lower-nickel PH stainless steels.
Copper (2.5–4.5%) the precipitation hardening element: Copper is the primary precipitation hardening element in both 15-5PH and 17-4PH.
During aging (Condition H900 through H1150), fine coherent copper-rich epsilon-copper precipitates nucleate within the martensitic matrix, producing the significant strength increase from the solution-annealed Condition A to the fully aged condition.
The copper precipitation kinetics are temperature-dependent – H900 aging produces the finest, most coherent precipitates (highest strength, lowest toughness); progressively higher aging temperatures produce coarser precipitates that provide a trade-off toward higher toughness and ductility at lower strength (H925 through H1150).
The aging temperature range of 900°F to 1150°F (482°C to 621°C) covers the full range of Cu precipitate sizes from peak-hardened to over-aged microstructures.
Niobium + Tantalum (0.15–0.45%): Niobium (and tantalum as its companion element in the spec) has two functions in 15-5PH: grain refining and carbon stabilization.
Niobium carbides pin austenite grain boundaries during solution annealing, producing a fine prior austenite grain size that improves toughness and fatigue resistance in the precipitation-hardened condition.
The “Nb+Ta” range rather than Nb alone is specified because tantalum and niobium are chemically analogous and are produced together in nature – commercial ferroniobium always contains some tantalum, and the specification range accounts for this. The Nb+Ta range of 0.15–0.45% is the same range used in 17-4PH (AMS 5604) – this is not a differentiating composition variable between the two alloys.
Carbon (0.07% max): Low carbon is required in 15-5PH for weldability, corrosion resistance (preventing sensitization and intergranular corrosion at chromium carbide precipitation temperatures), and to minimize austenite retained after quenching.
Low carbon maximizes the martensite transformation fraction during solution anneal cooling, contributing to the fully martensitic, low-ferrite microstructure required by BMS 7-240.
Manganese (1.00% max) and Silicon (1.00% max): Controlled at moderate levels.
Manganese influences martensite start (Ms) temperature and austenite stability; excessively high Mn would increase retained austenite after solution annealing.
Silicon is a ferrite stabilizer – its 1.00% max limit is balanced against oxidation resistance requirements during processing.
Phosphorus (0.040% max) and Sulfur (0.030% max): Controlled to minimize grain boundary segregation and sulfide inclusion content.
Combined with ESR processing (which further reduces inclusion levels beyond the primary melt), these compositional limits ensure the clean microstructure required for BMS 7-240’s through-thickness toughness requirements.
Mechanical Properties - BMS 7-240
Minimum mechanical properties for 15-5PH per BMS 7-240 in the solution annealed condition (Condition A):
| Property | Imperial | Metric |
|---|---|---|
| Tensile Strength (min) | 150,000 psi (150 ksi) | 1034 MPa |
| Yield Strength, 0.2% offset (min) | 115,000 psi (115 ksi) | 793 MPa |
| Elongation in 2 in. or 4D (min) | 10ù | 10ù |
| Hardness (typical, Condition A) | 28–32 HRC | - |
Elevated Temperature Properties - BMS 7-240
15-5PH per BMS 7-240 is a precipitation-hardenable martensitic stainless steel optimized for room-temperature structural service in a corrosive aerospace environment – it is not a high-temperature alloy.
The precipitation-hardened microstructure (copper precipitates in a tempered martensite matrix) is stable up to approximately 600°F (316°C) for sustained structural service.
Above this temperature, progressive over-aging of the copper precipitates occurs – the fine coherent Cu precipitates coarsen and lose coherency, reducing strength toward lower-condition properties. This over-aging is permanent: once over-aged in service, the strength loss cannot be recovered without full re-solution annealing and re-aging.
The following representative elevated temperature tensile data for 15-5PH in the H925 condition are from published literature (Carpenter Technology, typical values):
| Temperature | Tensile Strength (typical) | Yield Strength (typical) | Elongation (typical) |
|---|---|---|---|
| Room Temp (70°F / 21°C) | 170 ksi (1172 MPa) | 155 ksi (1069 MPa) | 10% |
| 200°F (93°C) | ~165 ksi (1138 MPa) | ~150 ksi (1034 MPa) | ~10% |
| 400°F (204°C) | ~155 ksi (1069 MPa) | ~145 ksi (1000 MPa) | ~10% |
| 600°F (316°C) | ~145 ksi (1000 MPa) | ~130 ksi (897 MPa) | ~11% |
Physical Properties - BMS 7-240
| Property | Value (Imperial) | Value (Metric) |
|---|---|---|
| Density | 0.284 lb/in³ | 7.78 g/cm³ |
| Solidus Temperature | ~2570°F | ~1410°C |
| Modulus of Elasticity | 28.0 × 10⁶ psi | 193 GPa |
| Thermal Conductivity | 9.0 BTU/(hr·ft·°F) | 15.6 W/(m·K) |
| Coefficient of Thermal Expansion | 5.9 × 10⁻⁶ /°F | 10.6 × 10⁻⁶ /°C |
| Specific Heat | 0.107 BTU/(lb·°F) | 448 J/(kg·K) |
| Max Structural Service Temperature (sustained) | ~600°F | ~316°C |
| Solution Anneal Temperature | 1900°F ± 25°F | 1038°C ± 14°C |
| Aging Temperature Range | 900°F–1150°F | 482°C–621°C |
| Melt Practice | ESR - mandatory per BMS 7-240 | - |
| Delta Ferrite Content (ESR, typical) | <2–5% (controlled) | - |
| Magnetic Permeability | Magnetic (martensitic, ferromagnetic) | - |
BMS 7-240 vs AMS 5862 vs AMS 5604 - Which Specification Do You Need?
| Feature | BMS 7-240 | AMS 5862 | AMS 5604 |
|---|---|---|---|
| Alloy | 15-5PH (UNS S15500) | 15-5PH (UNS S15500) | 17-4PH |
| Cr content (nominal) | 14.0–15.5% | 14.0–15.5% | 15.0–17.5% |
| Ni content (nominal) | 3.5–5.5% | 3.5–5.5% | 3.0–5.0% |
| Product Forms | Sheet, Strip, Plate | Sheet, Strip, Plate | Sheet, Strip, Plate |
| Delta ferrite (typical) | <2–5% (controlled) | <2–5% (controlled) | 5–20% (higher) |
| Short transverse toughness | Enhanced | Enhanced | Lower than 15-5PH |
| Melt Practice | ESR required | ESR | Air melt or VAR (specify) |
| Strength levels available | H900–H1150 | H900–H1150 | H900–H1150 |
| Condition designations | A, H900–H1150 | A, H900–H1150 | A, H900–H1150 |
| Specification authority | Boeing Material Specification | SAE International | SAE International |
| Boeing documentation required | Yes - Boeing CMTRs | No | No |
| Max plate thickness (BMS/spec) | 0.1875" to 6.50" | Per current rev | Per current rev |
| Material cost (relative) | Higher (ESR) | Higher (ESR) | Lower (air melt option) |
| Applicable for Boeing programs | Yes - required on BMS 7-240 drawings | No (requires Boeing eng. approval) | Not equivalent |
Choose BMS 7-240 when:
- The engineering drawing calls out BMS 7-240 – this is non-negotiable on Boeing programs; do not substitute AMS 5862 or AMS 5604 without a documented engineering deviation or specification change
- Boeing-specific quality documentation (CMTRs, traceability, Boeing-approved mill source) is required by the purchase order or contract
- Thick plate (up to 6.50″) in 15-5PH is required with confirmed ESR melt and controlled delta ferrite for short-transverse fracture-critical applications
Choose AMS 5862 when:
- The engineering drawing specifies AMS 5862 (or “15-5PH per AMS 5862”)
- 15-5PH sheet or plate is required for non-Boeing aerospace or industrial programs where Boeing-specific documentation is not required
- The alloy and product form requirements are identical to BMS 7-240 but Boeing quality overlay is not part of the program’s supply chain qualification
Choose AMS 5604 (17-4PH) when:
- The engineering drawing specifies AMS 5604 (17-4PH) or when the program does not require the enhanced short-transverse toughness of BMS 7-240 15-5PH
- Air-melt material is acceptable (confirmed by engineering drawing – no ESR requirement)
- Lower material cost versus 15-5PH is a consideration and the OEM design allowables are achievable with 17-4PH properties in all cross-sectional directions
Approved Mill Producers
Fighter Jet Metals sources 15-5PH per BMS 7-240 sheet, strip, and plate from Boeing-approved, AS9100D-certified mill producers.
The limited number of mills capable of ESR production of 15-5PH includes major specialty stainless steel producers; specific mill names are confirmed at time of order.
Contact Fighter Jet Metals to confirm the supplying mill, Boeing approval status, and available CMTR documentation before purchase.
BMS 7-240 Machining Guidelines
15-5PH per BMS 7-240 is most commonly machined and fabricated in the Condition A (solution annealed) state – the preferred sequence for aerospace structural components is: form, cut, and machine in Condition A, then precipitation age the completed (or near-complete) part to the specified H-condition.
Machining in the Condition A state significantly reduces tooling costs, machining cycle times, and surface finishing difficulty compared to machining in the aged H900 or H925 condition.
Machining guidelines for BMS 7-240 plate (Condition A):
- Work hardening: 15-5PH in Condition A work-hardens more rapidly than 300-series austenitic stainless steels and more gradually than fully work-hardened conditions; continuous cutting with adequate chip load is required
- Milling of plate: Down (climb) milling preferred; positive-rake carbide endmills; feed rates high enough to maintain chip load and avoid rubbing at the surface; flood coolant at all times
- Drilling of plate: Cobalt HSS or solid carbide drills; peck drilling for depths greater than 2D; high-pressure coolant for deep bores
- Grinding and surface finishing: After precipitation aging to H-condition, grinding to final dimensional tolerance is the preferred finishing method for precision surfaces; stress-relief cycle (H1150) may be applied if grinding-induced surface stresses are a concern for fatigue-limited surfaces
Weldability of BMS 7-240
15-5PH per BMS 7-240 in the Condition A (solution annealed) state is the most weldable delivery condition for 15-5PH stainless steel.
Because the material has not been precipitation aged, weld heat input in the solution annealed condition does not produce the strain-age cracking risk associated with welding fully hardened PH stainless steel. BMS 7-240 Condition A sheet and plate are routinely welded in Boeing fabrication shops for structural panel assemblies, welded pressure vessel shells, and sheet metal structural assemblies:
- Approved welding process: Gas Tungsten Arc Welding (GTAW) is the primary welding process for BMS 7-240 sheet and plate in Condition A. Minimizing heat input is critical for thin sheet to prevent distortion and to limit the width of the heat-affected zone.
- Filler metal: AWS A5.9 ER630 (17-4PH-type filler wire) is the standard matching filler for GTAW of 15-5PH. For applications where weld strength and corrosion resistance must match BMS 7-240 base metal properties after precipitation aging, a matching 15-5PH-type filler should be verified per the applicable Boeing Welding Process Specification (WPS) or qualified BMS welding procedure.
- Preheat: Preheat is generally not required for BMS 7-240 sheet in Condition A for thicknesses below 0.500″ (12.7 mm). For thick plate (>0.500″), a preheat of 150–200°F (66–93°C) reduces thermal gradient cracking risk from rapid cooling in the thick cross-section.
Melt Practice - BMS 7-240
BMS 7-240 requires electro-slag remelting (ESR) for all product forms – sheet, strip, and plate.
ESR is the melt practice that distinguishes 15-5PH per BMS 7-240 from conventional 17-4PH (AMS 5604), which may be produced by air-melt or vacuum arc remelting without the ESR process.
The ESR requirement is the primary metallurgical mechanism by which BMS 7-240 achieves the enhanced through-thickness (short transverse) properties for which 15-5PH is specified over 17-4PH on Boeing structural programs.
Electro-Slag Remelting (ESR) - Mandatory per BMS 7-240
15-5PH per BMS 7-240 is produced by consumable electrode electro-slag remelting.
The standard practice begins with a primary melt (typically air induction melt or vacuum induction melt) to establish the 15-5PH composition – particularly the precise control of Cr, Ni, Cu, Nb, and C required for both ESR processability and the specified ferrite-free microstructure.
The primary electrode is then remelted by the ESR process, in which the electrode passes through a molten flux (slag) pool that acts simultaneously as a liquid resistance heater and a metallurgical filter.
ESR remelting of 15-5PH provides the following critical attributes required by BMS 7-240:
- Delta ferrite control – the primary reason for ESR: 17-4PH (UNS S17400), with nominally similar composition, contains 5–20% delta ferrite in the microstructure as-remelted; this delta ferrite forms during solidification and is not eliminated by subsequent heat treatment. Delta ferrite in 17-4PH creates directional toughness anisotropy: the short transverse (through-thickness) direction on a 17-4PH plate has significantly lower toughness than the longitudinal direction because the elongated delta ferrite stringers are oriented parallel to the rolling direction, creating preferential crack propagation paths perpendicular to the short-transverse direction. 15-5PH per BMS 7-240, through composition adjustment (lower chromium, higher nickel relative to 17-4PH) combined with ESR processing, achieves a delta ferrite content typically below 2–5%, producing isotropic toughness behavior in large-section plate with no preferred cracking direction – essential for Boeing structural plate applications where short-transverse stress is present in service
- Inclusion morphology control: The ESR slag blanket (calcium fluoride-based flux system) acts as a chemical filter that removes oxide and sulfide inclusions from the melt as the electrode remelts through the slag pool. Oxide inclusions are absorbed into the slag phase by chemical reaction; sulfide inclusions are controlled by the sulfur partition coefficient between metal and slag. The resulting ESR ingot has significantly lower non-metallic inclusion content and smaller average inclusion size than air-melt primary products – critical for fatigue life in cyclically loaded Boeing structural sheet metal applications
- Controlled solidification and segregation reduction: The ESR process produces solidification in a shallow, well-stirred molten pool under the slag – significantly different from the deep, convective solidification of a large air-cast ingot. The controlled solidification geometry minimizes macro-segregation of copper (2.5–4.5% Cu in 15-5PH), which is critical for uniform precipitation hardening response and consistent mechanical properties from surface to center in thick plate
- Surface quality: ESR produces a smooth, oxide-free ingot surface with no surface defects that would require conditioning before hot rolling into sheet and plate – contributing to consistent surface quality on finished BMS 7-240 sheet and plate that is important for tight aerospace thickness tolerances
Always confirm ESR melt practice on the certified mill test report (CMTR) at time of BMS 7-240 procurement – ESR must be explicitly documented, not implied.
BMS 7-240 Cross-Reference Specifications
15-5PH Sheet, Strip & Plate
The SAE International standard equivalent to BMS 7-240 for 15-5PH sheet, strip, and plate
15-5PH Bars & Shapes
The 15-5PH long-product specification for bars, forgings, and shaped cross-sections
17-4PH Sheet, Strip & Plate
The competing PH stainless steel in equivalent flat-rolled product forms
Trade Names and Equivalent Designations
15-5PH per AMS 5862 is known by the following trade names and equivalent designations across different standards systems:
| Designation | System | Notes |
|---|---|---|
| 15-5PH | Common trade name | "Precipitation Hardening" - 15% Cr, 5% Ni; Armco Steel / AK Steel / Carpenter Technology trade name |
| XM-12 | AISI type | Legacy AISI designation sometimes used in older references for 15-5PH |
| AMS 5659 | SAE AMS | 15-5PH bars, forgings, and rings — sibling long-product specification |
| UNS S15500 | UNS (Unified Numbering System) | Standard material identifier in North America |
| DIN 1.4545 / W.Nr. 1.4545 | Werkstoff Nr. (German) | European material number designation |
| AMS 5862 | SAE AMS | Solution heat treated sheet, strip, and plate |
| BMS 7-240 | Boeing Material Specification | The Boeing standard specification for 15-5PH sheet, strip, and plate with ESR requirement and Boeing-specific documentation requirements |
Why Source BMS 7-240 from Fighter Jet Metals?
ESR certification on every order
BMS 7-240 mandates ESR melt practice; every CMTR is reviewed for confirmed ESR process documentation before shipment from a Boeing-approved mill source
Boeing-approved mill sourcing
All BMS 7-240 material is sourced from mills on the Boeing Source Approval List (SAL) - not just any ESR stainless mill; Boeing program compliance is maintained from mill qualification through distribution
AS9100D-certified aerospace sourcing
Material sourced from AS9100D-certified mills only
Plate inventory in Condition A
BMS 7-240 plate is stocked in the solution annealed (Condition A) state across standard thickness range for rapid shipment; condition-treated (H-condition) material available with full precipitation age heat treatment at the mill
Full CMTR package included
ESR melt practice documentation, solution anneal or age heat treatment records, chemical analysis (spectrographic per heat), and mechanical test certifications all provided with every shipment
All H-conditions available
H900 through H1150 precipitation-treated plate and sheet available to order with confirmed heat treatment records on CMTR; condition specified at order entry
Same-day quote response
Competitive pricing with rapid quote turnaround
Plate processing
Saw cutting of plate to length, waterjet blanking, and shearing of sheet with full CMTR traceability maintained through all cutting operations
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.