AMS 6512 Maraging 250 Steel UNS K92890 Round Bar
Short Description:
AMS 6512 Maraging 250 Steel Bar UNS K92890 delivers ultra-high aged strength, good toughness and low heat-treatment distortion for aerospace tooling and shafts. Round bars are available with custom diameter, finish, cutting, MTC and EN 10204 3.1.
Maraging 250 Steel Bar, also known as 18Ni250, C250, UNS K92890 and W.Nr. 1.6359, is a low-carbon, nickel-cobalt-molybdenum maraging steel supplied as round bar for ultra-high-strength aerospace, tooling and precision mechanical components. Unlike conventional quenched tool steels, it develops strength by precipitation aging of a tough, low-carbon martensitic matrix.
SAKY STEEL supplies AMS 6512 Maraging 250 round bar in annealed or specified aged condition. Available processing may include sawing, peeling, rough turning, centerless grinding and machining. Diameter, length, tolerance, surface, melting route, heat-treatment condition and inspection requirements should be clearly stated in the inquiry.
Product Parameters
| Item | Product Details |
|---|---|
| Product Name | Maraging 250 Steel Round Bar |
| Grade | Maraging 250 / C250 / 18Ni250 |
| UNS Designation | UNS K92890 |
| European Reference | W.Nr. 1.6359 / X2NiCoMo18-8-5 reference |
| Material Family | 18% nickel cobalt-containing maraging steel |
| Product Shape | Round bar and forged round bar |
| Regular Production Size | Approximately Ø10–250 mm |
| Made-to-Order Size | Larger forged sizes subject to technical review |
| Length | 1000–6000 mm or cut to length |
| Surface Finish | Black, peeled, rough turned or ground |
| Delivery Condition | Solution annealed or aged when specified |
| Standard | AMS 6512 |
| Tolerance | AMS tolerance, h9, h11 or drawing-specific |
| Available Services | Cutting, peeling, turning, grinding and machining |
| Certificates | MTC, EN 10204 3.1 and inspection reports |
Chemical Composition
Maraging 250 is an extremely low-carbon iron-nickel alloy strengthened primarily by cobalt, molybdenum, titanium and aluminum additions. The following ranges are typical references associated with AMS 6512 material.
| Element | Typical Content, wt.% | Technical Function |
|---|---|---|
| Nickel | 17.00–19.00 | Forms the tough nickel-martensitic matrix |
| Cobalt | 7.00–8.50 | Enhances age-hardening response |
| Molybdenum | 4.60–5.20 | Forms strengthening intermetallic precipitates |
| Titanium | 0.30–0.50 | Supports precipitation hardening |
| Aluminum | 0.05–0.15 | Contributes to the aging response |
| Carbon | 0.03 maximum reference | Kept very low to retain toughness and weldability |
| Manganese | 0.10 maximum reference | Controlled residual element |
| Silicon | 0.10 maximum reference | Restricted for premium alloy quality |
| Phosphorus | 0.010 maximum reference | Restricted to support toughness |
| Sulfur | 0.010 maximum reference | Restricted to limit inclusions |
| Iron | Balance | Base metal matrix |
Actual chemical composition shall be confirmed by the applicable product specification and MTC.
Mechanical and Heat-Treatment Properties
Maraging 250 is normally machined in the solution-annealed condition and then aged to develop ultra-high strength. The exact guaranteed properties depend on bar diameter, test orientation, melting route, aging treatment and AMS 6512 acceptance requirements.
| Property | Typical Reference | Condition | Engineering Meaning |
|---|---|---|---|
| Tensile Strength | Approximately 1720–1860 MPa | Aged | Provides the nominal 250 ksi strength class |
| 0.2% Yield Strength | Approximately 1655 MPa minimum reference | Aged | Supports highly stressed components |
| Elongation | Approximately 5–8% | Aged, size dependent | Maintains useful ductility at high strength |
| Hardness | About 48–52 HRC | Aged | Suitable for high-strength tooling and shafts |
| Annealed Hardness | Approximately 30–35 HRC | Solution annealed | Facilitates machining before aging |
| Density | Approximately 8.0–8.1 g/cm³ | Room temperature | Used for weight calculation |
| Elastic Modulus | Approximately 185–195 GPa | Room temperature | Supports structural stiffness calculations |
| Solution Treatment | Approximately 815–830°C | Air cooled | Prepares the alloy for machining and aging |
| Typical Aging | About 480°C for approximately 3–6 hours | Air cooled | Develops precipitation strength with low distortion |
Common Size Table
| Diameter | Length | Surface | Processing | Typical Use |
|---|---|---|---|---|
| Ø10–25 mm | 1000–4000 mm | Peeled or ground | Cutting and precision grinding | Pins, fasteners and precision shafts |
| Ø30–60 mm | 2000–6000 mm | Peeled or turned | Machining and centerless grinding | Drive shafts, gears and tooling |
| Ø65–120 mm | 2000–6000 mm | Rough turned | Saw cutting and rough machining | Landing gear and structural components |
| Ø125–200 mm | Custom cut length | Forged and rough turned | UT and machining when specified | Heavy-duty shafts and tooling blanks |
| Above Ø200 mm | Made to order | Forged or machined | Project-specific production | Large critical components |
Different Specifications Comparison
Round Bar Surface and Production Comparison
| Condition | Main Feature | Typical Use | Purchase Advice |
|---|---|---|---|
| Hot-Rolled Bar | Economical mill surface with machining allowance | General rough machining | Specify minimum finished diameter |
| Forged Bar | Suitable for larger sections and critical parts | Heavy shafts and tooling blanks | Specify UT and melting-route requirements |
| Peeled Bar | Scale-free surface with improved diameter control | CNC-machined shafts and fasteners | Suitable where reduced machining allowance is needed |
| Rough-Turned Bar | Clean surface and controlled machining allowance | Large structural parts | State final diameter and allowance |
| Ground Bar | Tight tolerance and smooth surface | Precision shafts and tooling components | Specify h9, h8 or drawing tolerance |
Comparison with Related Maraging Grades
| Grade | Main Strength | Relative Limitation | Typical Selection |
|---|---|---|---|
| Maraging 200 | Higher toughness and lower alloy strength | Lower aged strength than C250 | Moderately stressed precision components |
| Maraging 250 | Balanced ultra-high strength and toughness | Lower strength than C300 and C350 | Aerospace shafts, tooling and landing gear |
| Maraging 300 | Higher aged strength | Reduced toughness compared with C250 | More highly loaded structural parts |
| Maraging 350 | Maximum strength in the conventional family | Higher cost and lower toughness balance | Specialized maximum-strength components |
Equivalent Standards and International Names
| System | Designation | Relationship |
|---|---|---|
| Common Name | Maraging 250 / C250 / 18Ni250 | Common commercial designations |
| UNS | K92890 | Unified Numbering System designation |
| SAE Aerospace Standard | AMS 6512 | Primary bar and forging-stock specification |
| European Reference | 1.6359 | Common cross-reference; verify product requirements |
| British Reference | BS S162 / DTD 5212 | Common aerospace cross-reference |
| Legacy Military Reference | MIL-S-46850 | Historic maraging-steel reference |
| Commercial Reference | Vascomax 250 type | Commercial family reference, not automatic substitution |
Production Process Flow
Low-carbon iron, nickel, cobalt, molybdenum and controlled additions are prepared.
VIM supports precise chemistry and low gas content.
VAR improves cleanliness and structural uniformity.
Billets are reduced into round-bar or forging-stock form.
The structure is prepared for machining and later age hardening.
Bars may be peeled, turned, descaled or ground.
Chemistry, dimensions, surface and mechanical properties are verified.
Heat-number traceability is retained through export packing.
Product Inspection
| Inspection | Method | Purpose |
|---|---|---|
| Chemical Analysis | Laboratory spectrometric analysis | Confirm AMS 6512 chemistry |
| PMI | Positive material identification | Reduce alloy-mix risk; not a replacement for full chemistry |
| Tensile Testing | Yield, tensile and elongation testing | Verify aged mechanical properties |
| Hardness Testing | Rockwell or equivalent method | Confirm annealed or aged condition |
| Dimensional Inspection | Micrometer, caliper and length measurement | Verify diameter, length and tolerance |
| Surface Inspection | Visual and finish examination | Identify laps, cracks, scale or damage |
| Ultrasonic Testing | UT when specified | Evaluate internal soundness |
| Traceability Review | Heat number and document verification | Link the bar to MTC and EN 10204 3.1 |
| Third-Party Inspection | SGS, BV, TÜV or appointed inspector | Available when specified |
Product Packaging
Bars can be protected with oil, VCI paper, film or waterproof wrapping.
Separators and secure bands reduce movement and scratching.
Ground or machined bars can receive end caps or padded protection.
Export cases, skids or pallets are selected according to size and weight.
Grade, heat number, size and customer shipping marks are retained.
Applications, Core Performance and Fabrication
Primary Applications
- Aircraft landing-gear components
- High-strength drive shafts and crankshafts
- Rocket and missile structural components
- Ejector-system and actuator parts
- High-load gears, pins and fasteners
- Precision dies, mandrels and tooling inserts
- High-performance motorsport components
- Pressure-containing and structural aerospace parts when qualified
Strength and Toughness
Maraging 250 combines ultra-high aged strength with better toughness than higher-strength Maraging 300 and Maraging 350 grades. Its low-carbon matrix helps reduce brittle carbide formation and supports useful transverse properties and resistance to crack propagation.
Machinability
Machinability is generally good in the solution-annealed condition for an ultra-high-strength alloy steel. Major turning, drilling, milling and threading operations are normally completed before final aging. Carbide tooling, rigid machines, stable feeds and effective coolant are recommended.
Weldability
Maraging 250 has useful weldability because of its very low carbon content. Welding procedure qualification, matching filler strategy, cleanliness and post-weld aging must be selected according to the component design and governing aerospace or engineering requirements.
Heat Treatment
The alloy is designed for precipitation hardening. It is typically solution annealed, air cooled, machined close to final dimensions and then aged near 480°C. Aging produces intermetallic precipitation with relatively low dimensional change compared with conventional quench-hardening tool steels.
Corrosion and Surface Protection
Maraging 250 is not a stainless steel and should not be selected primarily for corrosion resistance. Protective coatings, plating, oiling or controlled storage may be required in humid, marine or chemically aggressive environments.
Why Choose SAKY STEEL?
Diameter, length, machining allowance and surface condition can be supplied according to drawings.
Material identification can be maintained from mill documentation through final packing.
MTC (Mill Test Certificate / 质保书) and EN 10204 3.1 can be provided according to the order.
PMI, hardness, tensile, dimensional and ultrasonic testing can be arranged when specified.
Saw cutting, peeling, rough turning and grinding are available subject to size and tolerance.
Protected bundles, wooden cases, pallets and customized shipping marks are available.
FAQ
What is Maraging 250 steel?
Maraging 250 is an ultra-high-strength, low-carbon iron-nickel steel containing cobalt, molybdenum, titanium and aluminum. It is strengthened by precipitation aging rather than conventional high-carbon quench hardening.
What standard applies to Maraging 250 round bar?
AMS 6512 is the principal aerospace specification used for Maraging 250 bars and forging stock. The required revision, size range, condition and inspection level should be specified in the purchase order.
Is Maraging 250 the same as UNS K92890?
UNS K92890 is the commonly used UNS designation for Maraging 250. The UNS number identifies the alloy family, while AMS 6512 controls product-specific requirements.
What strength can Maraging 250 achieve?
After correct aging, Maraging 250 commonly reaches approximately 250 ksi tensile-strength class, or around 1720 MPa and above. Exact guaranteed properties depend on bar size, orientation and the applicable AMS 6512 requirements.
Can Maraging 250 be machined before aging?
Yes. Major machining is normally performed in the solution-annealed condition, when the material is softer and easier to cut. Final grinding or dimensional correction may be completed after aging when required.
Can custom-ground Maraging 250 bars be supplied?
Ground, peeled and rough-turned bars can be discussed according to diameter, length, tolerance, straightness and surface requirements. Drawing-specific tolerances should be included in the inquiry.
Is ultrasonic testing available?
UT can be arranged for suitable bar and forged-bar sizes when specified. The inquiry should state the inspection method, acceptance level and reporting requirements.
Can SAKY STEEL provide an MTC?
Yes. MTC, heat-number traceability and EN 10204 3.1 documentation can be provided according to the purchase order. Additional hardness, tensile, dimensional, PMI or UT reports may also be arranged.
