Steel Marval 18
EN X3NiCoMoTi18-9-5
Marval 18 is a French trade designation for an 18Ni(300)-class maraging steel (X3NiCoMoTi18-9-5), a carbon-free Fe-Ni-Co-Mo martensite hardened by intermetallic precipitation during a ~480 °C age rather than by carbon.
Reference datasheet — Marval 18 is not in the instant-quote catalog. Upload your part and an engineer will quote it in this grade or suggest the closest stocked equivalent.
Values for the STA-480-3H condition
Marval 18 tempers and conditions
Marval 18 is supplied in 7 conditions, soft to hard. STA-480-3H is the default FabDigit quotes; the values on this page are for it.
Compare all 7 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Solution annealed (≈820 °C, air cool), soft martensite | Delivery condition for machining, forming and welding before final aging. | 800 | 1,030 | 18 | 31 HRC | — |
Overaged | Choose when fracture toughness and CVN matter more than peak strength (thick motor cases). | 1,720 | 1,800 | 12 | 50 HRC | 3.2 % IACS |
STA-480-3HDefault STA | Standard aerospace service condition: ~1950–2000 MPa UTS with usable toughness. | 1,900 | 1,980 | 10 | 54 HRC | — |
Aged + gas/plasma nitrided (≈450 °C surface treatment) | For wear surfaces, dies and shafts — nitriding at/below the aging temperature keeps the core properties. | 1,900 | 1,980 | 8 | 54 HRC | 3.1 % IACS |
VIM-VAR premium melt, solution annealed + aged | Double vacuum melted for rocket motor cases / critical flight hardware — best toughness and fatigue scatter. | 1,920 | 1,990 | 11 | 54 HRC | 3.1 % IACS |
STA | Longer age for maximum hardness/strength when toughness is less critical (tooling, dies). | 1,980 | 2,050 | 8 | 55 HRC | — |
Cold worked + aged | Cold-rolled/drawn before aging for the highest strengths in thin sections and springs. | 2,080 | 2,150 | 5 | 57 HRC | 3.1 % IACS |
What is Marval 18?
Marval 18 is a French trade designation for an 18Ni(300)-class maraging steel (X3NiCoMoTi18-9-5), a carbon-free Fe-Ni-Co-Mo martensite hardened by intermetallic precipitation during a ~480 °C age rather than by carbon. Engineers specify it for 1900 MPa yield, 1980 MPa tensile, 10 % elongation and 54 HRC combined with weldability and simple heat treatment; it is supplied as VIM-VAR bar, forging stock, plate and rings, and is used solution annealed, aged, overaged or aged-and-nitrided. Limits are cost of double-vacuum melting, no inherent corrosion resistance, service capped near 400 °C and low machinability (rating 25) once aged. Where lower strength with higher toughness is acceptable, an 18Ni(250) maraging grade is the nearest alternative. Marval 18 has a density of 8 g/cm³ (0.289 lb/in³), heavier than 95% of steel grades. It melts at 1,413°C (2,575 °F). Marval 18 has a yield strength of 1,900 MPa (276 ksi) and a tensile strength of 1,980 MPa (287 ksi) — stronger than 100% of steel grades. Elongation at break is 10% and the elastic modulus is 190 GPa (27.6 Msi).
What is Marval 18 used for?
- rocket motor cases
- high-strength aerospace shafts
- structural fasteners
Advantages
- High strength — 1,900 MPa (276 ksi), better than 100% of steel grades
- Polishes to a fine finish — 80/100, better than 97% of steel grades
- Good corrosion resistance — 22/100, better than 90% of steel grades
- Readily welded — 80/100, better than 79% of steel grades
Limitations
- High embodied carbon — 6.8 kg CO₂/kg, worse than 98% of steel grades
- Poor heat conductor — 20 W/m·K (11.6 BTU/hr·ft·°F), worse than 96% of steel grades
- Difficult to machine — 25/100, worse than 93% of steel grades
- Limited ductility — 10%, worse than 91% of steel grades
- Low electrical conductivity — 3.1 % IACS, worse than 89% of steel grades
Marval 18 properties
Typical room-temperature values for Marval 18-STA-480-3H; bars are the position among steel grades.
Physical3
Marval 18 has a density of 8 g/cm³ (0.289 lb/in³), heavier than 95% of steel grades. It melts at 1,413°C (2,575 °F).
Mechanical16
Marval 18 has a yield strength of 1,900 MPa (276 ksi) and a tensile strength of 1,980 MPa (287 ksi) — stronger than 100% of steel grades. Elongation at break is 10% and the elastic modulus is 190 GPa (27.6 Msi).
Thermal5
Marval 18 is rated for continuous service to 400°C (752 °F). It conducts heat at 20 W/m·K (11.6 BTU/hr·ft·°F), worse than 96% of steel grades. Thermal expansion is 10.1 µm/m·K (5.61 µin/in·°F).
Electrical3
Marval 18 conducts electricity at 3.1 % IACS, worse than 89% of steel grades.
Chemical & Environmental3
Corrosion resistance is poor (22/100), better than 90% of steel grades.
Sustainability4
Producing a kilogram of Marval 18 takes about 105 MJ of energy and emits 6.8 kg of CO₂ — more than 99% of steel grades. Typical recycled content is 20%.
Manufacturability8
Marval 18's machinability is poor (25/100, worse than 93% of steel grades); weldability very good (80/100); formability poor (15/100).
Common Calculations5
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Strength versus weight in the steel family
Yield strength against density for every steel grade FabDigit runs. Marval 18 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with Marval 18
Is Marval 18 easy to machine?
Machine in the solution-annealed state (≈30 HRC) with sharp carbide tooling, rigid setups and generous coolant; aged material at 54 HRC needs low-speed carbide/CBN or grinding, and aging shrinkage of about 0.04–0.08 % must be allowed for.
Can Marval 18 be welded?
Excellent weldability by TIG/EB/laser with matching filler, no preheat and no hydrogen cracking risk thanks to the carbon-free martensite; weld in the annealed state, keep heat input low and re-age at 480 °C to restore joint strength.
Can Marval 18 be formed, bent or molded?
Cold form, spin or roll only in the solution-annealed condition (still ~800 MPa yield, so heavy tooling is needed); hot work 1150–900 °C, then re-solution treat at ~820 °C before aging.
Marval 18 chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| Cultra-low carbon, carbide-free martensite | ≤ 0.03 | 0.01 |
| Ni | 17.5 – 19 | 18.3 |
| Co | 8.5 – 9.5 | 9 |
| Mo | 4.6 – 5.2 | 4.9 |
| Timain Ni3Ti precipitate former | 0.55 – 0.8 | 0.68 |
| Al | 0.05 – 0.15 | 0.1 |
| Si | ≤ 0.1 | 0.05 |
| Mn | ≤ 0.1 | 0.05 |
| P | ≤ 0.01 | 0.01 |
| S | ≤ 0.01 | 0 |
| Fe | balance |
What surface finishes work on Marval 18?
Not corrosion resistant — protect with cadmium, zinc-nickel or nickel plating, phosphate plus primer, or passivating paint; avoid electrolytic processes that charge hydrogen, or bake immediately after plating; nitriding at ≤480 °C gives a hard wear case without softening the core.
Surface treatments FabDigit runs on steel parts — pick them in the quote configurator or call them out on the drawing. Each links to its datasheet in the surface-finish library (thickness, specs, call-out, material verdicts).
Organic Coating
Black / Phosphate
Thermal Spray
Equivalent designations
Standards and trade names that resolve to Steel Marval 18 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- EN / DIN / Werkstoff-Nr.
- X3NiCoMoTi18-9-5
How much does Marval 18 cost?
Marval 18 is a high-cost steel ($$$$), pricier than about 78% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Marval 18 — frequently asked
What is Marval 18 used for?
Marval 18 is typically used for rocket motor cases, high-strength aerospace shafts and structural fasteners. In short: weldable ultra-high-strength steel; 1900 MPa yield, 54 HRC; no preheat, low-distortion aging.
What is the yield strength of Marval 18?
Marval 18 has a typical yield strength of 1,900 MPa (276 ksi) and a tensile strength of 1,980 MPa (287 ksi) — stronger than 100% of steel grades. Strength varies by condition: see the 7 listed tempers.
Is Marval 18 easy to machine?
Not especially — machinability is rated poor (25/100, worse than 93% of steel grades). Machine in the solution-annealed state (≈30 HRC) with sharp carbide tooling, rigid setups and generous coolant; aged material at 54 HRC needs low-speed carbide/CBN or grinding, and aging shrinkage of about 0.04–0.08 % must be allowed for.
Can Marval 18 be welded?
Yes — weldability is rated very good (80/100). Excellent weldability by TIG/EB/laser with matching filler, no preheat and no hydrogen cracking risk thanks to the carbon-free martensite; weld in the annealed state, keep heat input low and re-age at 480 °C to restore joint strength.
What surface finishes work on Marval 18?
Not corrosion resistant — protect with cadmium, zinc-nickel or nickel plating, phosphate plus primer, or passivating paint; avoid electrolytic processes that charge hydrogen, or bake immediately after plating; nitriding at ≤480 °C gives a hard wear case without softening the core.
Can Marval 18 be formed, bent or molded?
Cold form, spin or roll only in the solution-annealed condition (still ~800 MPa yield, so heavy tooling is needed); hot work 1150–900 °C, then re-solution treat at ~820 °C before aging.
What is the maximum service temperature of Marval 18?
Marval 18 is rated for continuous use to about 400°C (752 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between Marval 18 STA-480-3H and Marval 18-SA?
STA-480-3H is the default condition — standard aerospace service condition: ~1950–2000 MPa UTS with usable toughness. SA: delivery condition for machining, forming and welding before final aging. Yield strength is 1,900 MPa in STA-480-3H versus 800 MPa in SA.
How much does Marval 18 cost?
Marval 18 is a high-cost steel ($$$$), pricier than about 78% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Sources
- AMS 6514 — Steel, Maraging, Bars/Forgings 18.5Ni-9.0Co-4.9Mo-0.65Ti, consumable electrode melted — SAE International (2020)
- EN 10027 / material 1.6354 X3NiCoMoTi18-9-5 designation — CEN (2016)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels and High-Performance Alloys (Maraging Steels) — ASM International (1990)
- ASM Handbook Vol.19 — Fatigue and Fracture — ASM International (1996)
- Marval 18 maraging steel datasheet — Aubert & Duval (2021)
- MMPDS-style typical room-temperature data for 18Ni(300) maraging steel — Battelle/FAA (2023)
Property data is compiled from published supplier and standards handbooks and normalised for comparison; hardness values on non-Brinell scales are converted approximately for charting only. Manufacturability limits are FabDigit quote-engine defaults and may be relaxed by engineering review. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.