What Is Maraging 250 Steel? Overview and Key Properties
Maraging 250 Steel is a premium ultra-high-strength martensitic precipitation hardening alloy steel belonging to the 18% nickel maraging family, classified within the broader alloy structural steel category. Unlike conventional high-strength steels that rely on carbon-induced hardening, Maraging 250 Steel achieves its exceptional mechanical properties through the precipitation of intermetallic phases — primarily Ni3Mo and Ni3Ti — within a soft, ductile, low-carbon iron-nickel martensite matrix. This unique strengthening mechanism results in an outstanding combination of ultra-high yield strength, good fracture toughness, and excellent weldability that carbon-hardened steels cannot match.
The principal alloying elements are nickel (17–19%), cobalt (7–8.5%), molybdenum (4.6–5.2%), and titanium (0.30–0.50%). Nickel stabilizes the martensite matrix and promotes toughness; cobalt enhances the precipitation hardening response by reducing the solubility of molybdenum; molybdenum is the primary precipitate-forming element responsible for the high-strength increment on aging; and titanium further accelerates and strengthens the precipitation reaction. The carbon content is held to an extremely low maximum of 0.03%, which eliminates the brittleness of carbide phases and retains the inherent toughness of the martensitic matrix.
The grade is supplied in the solution annealed condition (maximum 34 HRC), making it easy to machine and form. After precision aging at approximately 480°C, it develops a minimum yield strength of 1,655 MPa (240 ksi) and minimum tensile strength of 1,724 MPa (250 ksi) — the "250" in its name directly references this 250 ksi tensile capability. Its primary market is the aerospace and defense sector, where it is used for highly stressed structural components, rocket motor casings, and landing gear parts. Fushun Metal supplies Maraging 250 Steel as round bar and forgings produced via the VIM + VAR double-vacuum melting route, conforming to AMS 6512 and related standards.
Maraging 250 Steel — Equivalent Grades and Cross-Reference
| Trade / Common Name | USA — UNS | AMS Standard | ASTM Standard | Notes |
|---|---|---|---|---|
| Maraging 250 / 18Ni(250) | K92890 | AMS 6512 (bar, forgings) AMS 6514 (sheet, strip, plate) | ASTM A538 Grade B | 18% Ni maraging family; named for 250 ksi (1,724 MPa) tensile target |
Note: Maraging steels are primarily governed by US/AMS and ASTM standards. There is no direct, fully equivalent DIN, EN, JIS, or GB designation for this specific grade. Procurement should reference AMS 6512 or ASTM A538 Grade B as the controlling specification.
Applications of Maraging 250 Steel
The unique property profile of Maraging 250 Steel — combining ultra-high strength, good toughness, and excellent weldability with low distortion on aging — makes it the material of choice for the most demanding aerospace and defense components. Its near-zero carbon content and dimensional stability during the aging heat treatment allow it to be machined to final dimensions in the annealed state, then hardened with minimal dimensional change.
- Solid-propellant rocket motor casings and pressure vessels requiring high fracture toughness
- Aircraft primary structural frames, spars, and bulkheads
- Aircraft and helicopter landing gear components (main struts, drag struts, torque links)
- High-strength fasteners, bolts, and tension rods for aerospace assemblies
- Missile airframe sections and guidance system housings
- Undercarriage actuator rods and hydraulic cylinder bodies
- High-performance drive shafts and torsion bars in rotorcraft
- Tooling fixtures and stretch-form dies requiring high strength with minimal deflection
- Flexible metal hose core elements for low-cycle fatigue applications
- Test frames and structural components in space launch vehicles
Applicable Standards for Maraging 250 Steel
Maraging 250 Steel is governed primarily by US aerospace materials standards. The table below lists all confirmed applicable standards. Fushun Metal can produce to any of these specifications upon request; customers should specify the required standard and product form when inquiring.
| Standard Body | Standard Number | Grade / Class | Covered Product Form |
|---|---|---|---|
| AMS | AMS 6512 | 18Ni(250) / Maraging 250 | Bars, forgings, and stock for forging — up to 10 in. (254 mm) diameter or least distance between parallel sides |
| AMS | AMS 6514 | 18Ni(250) / Maraging 250 | Sheet, strip, and plate |
| ASTM | ASTM A538 Grade B | Grade B (250 grade) | Precipitation hardening maraging steel plate, sheet, and strip |
Available Sizes and Delivery Conditions
Rolled Round Bar
Fushun Metal supplies Maraging 250 Steel as hot-rolled round bars covering a broad diameter range. All bars are supplied in the solution annealed condition per AMS 6512 requirements, with dimensional tolerances to IT h/k 11 for smaller sections and IT h/k 14 for larger sections.
| Diameter Range (mm) | Length Range (m) | Dimensional Tolerance | Surface Condition |
|---|---|---|---|
| 5 – 12.49 | 3.00 – 4.00 | IT h/k 11 | Solution Annealed / Black |
| 12.50 – 55.00 | 3.00 – 4.00 | IT h/k 11 | Solution Annealed / Black |
| 55.01 – 120.00 | 3.00 – 4.00 | IT h/k 11 | Solution Annealed / Black |
| 120.01 – 140.00 | 3.00 – 5.00 | IT h/k 14 | Solution Annealed / Black |
Forged Round Bar and Shaft
For larger cross-sections exceeding the rolled bar range, Fushun Metal produces forged round bars and shafts using our 6,000-ton forging press and radial forging machine. Forging from VIM + VAR ingot ensures excellent internal soundness, consistent grain structure throughout the cross-section, and compliance with the stringent ultrasonic inspection requirements of AMS 6512. Maximum diameter follows the AMS 6512 limit of 10 inches (254 mm).
| Diameter Range (mm) | Length Range (m) | Dimensional Tolerance | Surface Condition |
|---|---|---|---|
| 140.01 – 203.20 (8 in.) | 3.00 – 5.00 | IT h/k 14 | Solution Annealed / Black or Turned |
| 203.21 – 254.00 (10 in.) | 3.00 – 5.00 | IT h/k 14 | Solution Annealed / Black or Turned |
Delivery Condition, Lead Time, and MOQ
| Order Type | MOQ | Typical Lead Time | Notes |
|---|---|---|---|
| Stock sizes (ready inventory) | 1 piece | ~ 7 days | Common diameters held in solution annealed condition |
| Custom rolling / small-batch VIM+VAR | 3 – 5 tons | ~ 30 days | Custom diameter, length, or surface finish requirements |
| Large-batch forging / rolling | Negotiable | 30 – 60 days | Full AMS 6512 certification package included |
Need Maraging 250 Steel for Your Project?
Fushun Metal holds ready stock in common sizes and can produce custom dimensions to AMS 6512 with full VIM + VAR melting and 3.1 certification. Get a fast response from our technical team.
Chemical Composition of Maraging 250 Steel
The composition of Maraging 250 Steel is tightly controlled, particularly the ultra-low carbon and impurity levels, to ensure the ductile martensite matrix that underpins its toughness. The table below presents the composition requirements per AMS 6512 and ASTM A538 Grade B. Note that AMS 6512, as an aircraft-quality specification, additionally specifies limits on boron (B), calcium (Ca), and zirconium (Zr) for enhanced cleanliness and melt consistency; these elements are not universally specified in ASTM A538.
| Designation | C | Si | Mn | P | S | Cr | Mo | Ni | Co | Ti | Al | Cu | B | Ca | Zr |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| AMS 6512 (18Ni250, bar/forgings) | max 0.03 | max 0.10 | max 0.10 | max 0.010 | max 0.010 | max 0.50 | 4.60 – 5.20 | 17.00 – 19.00 | 7.00 – 8.50 | 0.30 – 0.50 | 0.05 – 0.15 | max 0.50 | max 0.004 | max 0.05 | max 0.02 |
| ASTM A538 Gr. B (18Ni250) | max 0.03 | max 0.10 | max 0.10 | max 0.010 | max 0.010 | max 0.50 | 4.60 – 5.20 | 17.00 – 19.00 | 7.00 – 8.50 | 0.30 – 0.50 | 0.05 – 0.15 | max 0.50 | — | — | — |
All values in weight percent (wt.%). Highlighted cells (orange) indicate differences between the two standards. AMS 6512 additionally controls B, Ca, and Zr for aircraft-quality cleanliness requirements.
Melting Process and Steel Cleanliness
The melting route for Maraging 250 Steel is critical to its performance. Due to the extremely low carbon requirement, the reactive alloying elements (titanium, aluminum), and the demanding aerospace end-use, conventional open-atmosphere melting is not suitable for this grade. The standard and required production route per AMS 6512 is double-vacuum melting: Vacuum Induction Melting (VIM) followed by Vacuum Arc Remelting (VAR). This two-step process ensures the highest possible cleanliness, inclusion control, chemical homogeneity, and segregation minimization throughout the cross-section.
For customers with less stringent requirements — such as tooling or test-article applications not requiring full AMS 6512 certification — alternative melting routes can be discussed. Fushun Metal works closely with each customer to select the optimal melting path for their specific application and budget. The available routes are summarized below:
Mechanical Properties
Maraging 250 Steel is typically supplied in the solution annealed condition for machining and fabrication. The final mechanical properties are developed by the customer through an aging heat treatment. The properties in both conditions are presented below.
Maraging 250 Steel in Solution Annealed Condition
| Diameter / Section | Tensile Strength | Hardness (HRC) | Condition |
|---|---|---|---|
| ≤ 12.7 mm diameter | max 1,103 MPa (160 ksi) | max 34 HRC | Solution Annealed |
| > 12.7 mm diameter | — | max 34 HRC | Solution Annealed |
Maraging 250 Steel after Aging Treatment (Precipitation Hardened)
After aging at 480°C (900°F) for a minimum of 3 hours followed by air cooling, the following minimum mechanical properties are required per AMS 6512 at room temperature:
| Condition | Tensile Strength (MPa) | 0.2% Yield Strength (MPa) | Elongation (%, 50.8 mm GL) | Reduction of Area (%) |
|---|---|---|---|---|
| Aged: 480°C / 3 h min, AC | min 1,724 MPa (250 ksi) | min 1,655 MPa (240 ksi) | min 6% | min 25% |
Properties listed are minimum requirements per AMS 6512 at room temperature. Actual test values typically exceed minimum requirements. Specific size and sampling requirements per AMS 6512 apply — consult the standard for details.
Heat Treatment of Maraging 250 Steel
The heat treatment cycle for Maraging 250 Steel consists of two steps: solution annealing (performed by the mill as part of the delivery condition) and aging (precipitation hardening), typically performed by the end-user after final machining. Due to the near-zero distortion that occurs during aging, it is advantageous to machine the part to final dimensions in the annealed condition and then age the finished component.
| Process | Temperature | Holding Time | Cooling Method | Purpose |
|---|---|---|---|---|
| Solution Annealing | 820°C ± 14°C (1500°F ± 25°F) | 1 hour minimum per 25 mm of cross-section | Air Cool | Dissolves precipitates; produces soft martensitic matrix (max 34 HRC); enables machining |
| Aging (Precipitation Hardening) | 480°C ± 8°C (900°F ± 15°F) | 3 hours minimum | Air Cool | Precipitates Ni3Mo and Ni3Ti intermetallics; achieves min 1,724 MPa tensile / 1,655 MPa yield strength |
Surface Finish and Machining Options
Maraging 250 Steel in the solution annealed condition (max 34 HRC) exhibits machinability broadly comparable to austenitic stainless steel. Carbide tooling with appropriate chip-breaker geometry is recommended. After aging to full hardness (approximately 50–52 HRC), machining is significantly more difficult; therefore, finish machining is strongly advised prior to the aging treatment. Fushun Metal offers the following surface conditions and precision machining services:
| Product Form | Available Surface Conditions | Achievable Surface Roughness | Dimensional Tolerance |
|---|---|---|---|
| Rolled Round Bar | Black (as-rolled) Turned (peeled) | Black: Ra ≤ 12.5 μm Turned: Ra ≤ 3.2 μm | IT h/k 11 (standard) IT h/k 14 (larger sections) |
| Forged Round Bar / Shaft | Black (as-forged) Turned (peeled) | Black: Ra ≤ 12.5 μm Turned: Ra ≤ 3.2 μm | IT h/k 14 |
| Precision-Turned Round Bar | CNC Turned + Ground | Ra ≤ 0.8 μm (ground) | h6 / h7 on request |
Custom cutting to length, facing, and chamfering are available as standard services. Please specify your required surface condition and tolerance class when placing an inquiry.
Quality Inspection and Testing
Fushun Metal operates a comprehensive quality management system certified to ISO 9001. For aerospace-grade Maraging 250 Steel supplied to AMS 6512, our quality system also aligns with AS9100 requirements. Inspection is conducted at three stages to ensure full traceability and conformance.
Pre-Production
- Review and approval of customer specification, drawing, and AMS 6512 requirements
- Raw material (VIM + VAR ingot) chemical composition verification by OES spectrometry
- Melting and heat records review and traceability assignment
In-Process
- Dimensional checks at each production stage (forging, rolling, heat treatment)
- Heat treatment records: solution anneal temperature, time, and cooling method recorded for every lot
- Visual surface inspection for laps, seams, or heat treatment anomalies
Post-Production (Final Inspection)
- Chemical Composition: Final product verification by certified laboratory OES analysis
- Mechanical Testing: Tensile strength, yield strength, elongation, reduction of area per AMS 6512 sampling requirements (solution annealed + aged test pieces)
- Hardness Testing: Brinell or Rockwell C hardness verification on each bar or lot
- Ultrasonic Testing (UT): 100% longitudinal UT per ASTM A388 or equivalent; acceptance per AMS 6512 requirements
- Metallographic Examination: Grain size, cleanliness rating (inclusion content), and macrostructure evaluation on representative samples
- Dimensional Inspection: Diameter, length, straightness, and surface finish verification
Standard certification: EN 10204 Type 3.1 Mill Test Certificate (MTC) issued with every shipment. Type 3.2 (witness by independent party) is available on request. Third-party inspection by SGS, TÜV, or other nominated agencies can be arranged.
Packing and Shipping
All Maraging 250 Steel products are carefully packed to ensure the material arrives at your facility free from damage, corrosion, and surface contamination. Packing method is selected based on surface condition and product form.
Black (As-Rolled / As-Forged) Surface
- Bundled with steel wire or steel strapping in standard bundle weights
- Anti-rust oil applied to all surfaces before bundling
- Bundle ends protected with steel caps to prevent handling damage
- Suitable for standard container loading; bundles arranged to prevent movement in transit
Bright / Turned / Ground Surface
- Each bar individually wrapped in VCI (Vapor Corrosion Inhibitor) plastic film to protect the machined surface
- Wrapped bars bundled and further protected with woven polypropylene cloth
- For precision-ground bars: individual wooden boxes or foam-lined crates to fully protect dimensional integrity and surface roughness
- Anti-rust oil applied beneath film wrapping; guaranteed corrosion-free for minimum 12 months during ocean transit
Shipping and Documentation
- Export packing compliant with ISPM 15 for wooden materials (where applicable)
- Full shipping documentation: commercial invoice, packing list, certificate of origin, EN 10204 3.1 MTC, and any required test reports
- Shipment by sea (FCL or LCL), air freight, or land transport — worldwide delivery available
Frequently Asked Questions
Can you cut Maraging 250 Steel to my specific length?
What is the hardness of Maraging 250 Steel in the solution annealed condition?
What is the minimum order quantity for Maraging 250 Steel?
What international designations are equivalent to Maraging 250 Steel?
Ready to Order Maraging 250 Steel?
Fushun Metal supplies AMS 6512-conforming Maraging 250 Steel bar and forgings produced by VIM + VAR double-vacuum melting, with EN 10204 3.1 certification as standard. Stock available. Custom dimensions and large-batch orders welcome. Contact our technical sales team for a fast, professional response.
