Maraging 250 – UNS K92890
Age-hardenable 18Ni(250) maraging steel
Ultra-high-strength steel with 18% nickel, cobalt, molybdenum and titanium, almost carbon-free. It is supplied solution annealed (≈ 30 – 35 HRC, machinable) and hardens by aging at 480 °C, reaching a minimum yield strength of 1,724 MPa with good toughness and minimal distortion. Used in aerospace and defense parts, highly stressed shafts and tooling.
Designations and equivalents
| System | Designation |
|---|---|
| UNS | K92890 |
| W.Nr./EN | 1.6359 (X2NiCoMo18-8-5) |
| DIN | X2NiCoMo18-8-5 |
| Trade names | Maraging 250, 18Ni(250), C250, VascoMax® C-250 |
| Others | AMS 6512; MIL-S-46850; BS S162; DTD 5212 |
Standards by product form
| Form | Standard |
|---|---|
| Bar and forging | AMS 6512 |
| Sheet and strip | AMS 6520* |
| Bar, forging and plate (military) | MIL-S-46850 |
| Bar and forging (UK) | BS S162 / DTD 5212 |
Tolerances and HS codes
- Forged bars (round and square): machining allowance from 2 mm (Ø 6–16 mm) to 24 mm (Ø 400–500 mm) on the diameter. E.g. Ø 100–125 mm finished: +7 mm, tolerance +6 / −0 (length up to 3,500 mm).
- Forged discs: allowance of 4 to 9 mm on the diameter and 3 to 11 mm on the height, plus-only tolerance.
- Cutting and machining: band saw −0 / +5 to +15 mm on length; waterjet +10 % of thickness on the diameter (min. 2 mm); machined parts −0 / +2 to +5 mm on the diameter. See the full tables (INF 002 and INF 003, the same for every alloy).
| Form | NCM (Brazil, 8 digits) | HS (international, 6 digits) | HTS (USA, 10 digits)* | CN (European Union, 8 digits)* |
|---|---|---|---|---|
| Forged bar | 7228.40.00 | 7228.40 | 7228.40.0000 | 7228 40 90 |
| Hot-rolled bar | 7228.30.00 | 7228.30 | 7228.30.8041 | 7228 30 61 |
| Plate (> 10 mm, width ≥ 600 mm) | 7225.40.90 | 7225.40 | 7225.40.3050 | 7225 40 40 |
| Flange and fitting | 7307.91.00 | 7307.91 | 7307.91.5030 | 7307 91 00 |
Tariff class: alloy steel (by chemical composition, under the Chapter 72 Notes and Section XV Note 5).
*: US and EU codes for reference. NCM per current legislation (General Rules of Interpretation, Notes to Chapters 72, 74 and 75 and Section XV Note 5). Confirm the final code with your customs broker according to the item size and finish. HS = first 6 digits of the NCM.
Chemical composition (%)
AMS 6512 (UNS K92890)
| Element | Range (%) |
|---|---|
| Ni | 17.0 – 19.0 |
| Co | 7.0 – 8.5 |
| Mo | 4.6 – 5.2 |
| Ti | 0.30 – 0.50 |
| Al | 0.05 – 0.15 |
| C | ≤ 0.03 |
| Mn | ≤ 0.10 |
| Si | ≤ 0.10 |
| P | ≤ 0.010 |
| S | ≤ 0.010 |
| Cr | ≤ 0.50* |
| Cu | ≤ 0.50* |
| Fe | balance |
Mechanical properties
Aged at 480 °C (900 °F) – AMS 6512 minimums; solution annealed hardness per supplier
| Property | Value |
|---|---|
| Yield strength (0.2%) | ≥ 1,724 MPa (250 ksi) |
| Tensile strength | ≥ 1,758 MPa (255 ksi) |
| Elongation (4D) | ≥ 6% |
| Hardness, aged | ≥ 48 HRC (typical 48 – 52 HRC) |
| Hardness, solution annealed | ≈ 30 – 35 HRC |
Typical physical properties
| Property | Value |
|---|---|
| Density | 8.03 g/cm³ |
| Modulus of elasticity | ≈ 186 GPa |
| Thermal expansion (mean) | ≈ 10.1 µm/m·K |
Heat treatment, welding and machining
| Item | Usual practice |
|---|---|
| Service temperature | From cryogenic up to ≈ 400 °C* in continuous service; above the aging temperature the material overages and loses strength. It is not stainless: it needs corrosion protection. |
| Heat treatment | Solution annealing at ≈ 815 – 830 °C*, about 1 h per 25 mm of thickness, air cool: soft Fe-Ni martensite (≈ 30 – 35 HRC). Aging at 480 °C (900 °F) for 3 to 6 h, air cool: 48 – 52 HRC. Large sections need longer times. Dimensional change on aging is small and uniform, so parts can be machined almost to final size before aging. |
| Welding | Good weldability without preheating or postheating, because the very low carbon does not form hard martensite in the heat-affected zone. Weld in the solution annealed condition and age the whole part afterwards to restore strength in the joint. Repair welding of tools and dies is possible. |
| Machining | Machine in the solution annealed condition (30 – 35 HRC), with carbide, and age afterwards; distortion is minimal. After aging, only grinding or light finishing. Excellent polishability. |
Typical applications
- Slat tracks and aerospace structural components
- Missile and ejection systems
- Highly stressed drive shafts
- Die casting dies and tooling
- Critical defense and structural parts
Alternatives: Maraging 300 (UNS K93120*) when even higher strength is required; quenched and tempered SAE 4340 or 300M when cost matters and quench distortion is acceptable; 17-4PH or 15-5PH when corrosion resistance is needed with lower strength.
Maraging 250: complete guide
What maraging steel is
Maraging comes from "martensite aging": the steel forms a very low-carbon iron-nickel martensite, soft and tough, which is then hardened by aging. During aging, molybdenum and titanium precipitate fine intermetallic compounds; cobalt accelerates this precipitation. That is why Maraging 250 hardens without quenching, without cracking and with almost no distortion, unlike quenched and tempered steels such as SAE 4340.
Maraging 250 and other precipitation-hardening alloys
Maraging 250 belongs to the same heat-treatment group as precipitation-hardening stainless steels such as 17-4PH and 15-5PH, but with much higher strength and no corrosion resistance. Maraging 300 is the higher-strength version, with more cobalt and titanium.
Supply forms and Dustre services
Round bars and blocks forged in open die, cut to size on a band saw, with rough or finish machining, heat treatment in our own furnaces and hardness, tensile and impact testing. All material is supplied with a 3.1 inspection certificate and heat traceability.
Frequently asked questions
What is the chemical composition of Maraging 250?
Per AMS 6512 (UNS K92890): Ni 17.0 – 19.0; Co 7.0 – 8.5; Mo 4.6 – 5.2; Ti 0.30 – 0.50; Al 0.05 – 0.15; C ≤ 0.03.
Which standards cover Maraging 250?
Bar and forging: AMS 6512. Sheet and strip: AMS 6520*. Bar, forging and plate (military): MIL-S-46850. Bar and forging (UK): BS S162 / DTD 5212.
Up to what temperature can Maraging 250 be used?
From cryogenic up to ≈ 400 °C* in continuous service; above the aging temperature the material overages and loses strength. It is not stainless: it needs corrosion protection.
Which materials can replace Maraging 250?
Maraging 300 (UNS K93120*) when even higher strength is required; quenched and tempered SAE 4340 or 300M when cost matters and quench distortion is acceptable; 17-4PH or 15-5PH when corrosion resistance is needed with lower strength.
What does the 250 in Maraging 250 mean?
It is the minimum yield strength after aging in ksi: 250 ksi, or 1,724 MPa. By the same rule, Maraging 300 targets about 300 ksi*.
Is Maraging 250 stainless?
No. It has 18% nickel but almost no chromium, so it does not form a passive layer. Parts exposed to moisture need protection (oil, paint, coating). For high strength with corrosion resistance, use 17-4PH or 15-5PH.
What is the aging temperature of Maraging 250?
480 °C (900 °F) for 3 to 6 h, air cooled, starting from solution annealed material. Hardness goes from ≈ 30 – 35 HRC to 48 – 52 HRC.
