Steel Marval 18 VIM-VAR
Grade
EN X3NiCoMoTi18-9-5
VIM-VAR = vIM-VAR premium melt, solution annealed + aged
Double vacuum melted for rocket motor cases / critical flight hardware — best toughness and fatigue scatter.
Values for the VIM-VAR condition
Other Marval 18 tempers and conditions
Marval 18 is listed in 7 conditions; see the grade overview at Marval 18.
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-VARThis page 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 VIM-VAR?
Marval 18 VIM-VAR is Marval 18 in the VIM-VAR grade — double vacuum melted for rocket motor cases / critical flight hardware — best toughness and fatigue scatter. Marval 18 VIM-VAR has a yield strength of 1,920 MPa (278 ksi) and a tensile strength of 1,990 MPa (289 ksi) — stronger than 100% of steel grades. Elongation at break is 11% and the elastic modulus is 190 GPa (27.6 Msi). Marval 18 VIM-VAR 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). STA-480-3H is the default condition FabDigit quotes; VIM-VAR is available on request or by drawing note.
Advantages
- High strength — 1,920 MPa (278 ksi), better than 100% of steel grades
- Polishes to a fine finish — 80/100, better than 97% of steel grades
- Good corrosion resistance — 24/100, better than 91% of steel grades
- Readily welded — 85/100, better than 83% 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 — 11%, worse than 89% of steel grades
- Low electrical conductivity — 3.1 % IACS, worse than 89% of steel grades
Marval 18 VIM-VAR properties
Typical room-temperature values for Marval 18 VIM-VAR; 22 are specific to this condition. Other listed values are Marval 18 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
Marval 18 VIM-VAR 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 VIM-VAR has a yield strength of 1,920 MPa (278 ksi) and a tensile strength of 1,990 MPa (289 ksi) — stronger than 100% of steel grades. Elongation at break is 11% and the elastic modulus is 190 GPa (27.6 Msi).
Thermal5
Marval 18 VIM-VAR 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 VIM-VAR conducts electricity at 3.1 % IACS, worse than 89% of steel grades.
Chemical & Environmental3
Corrosion resistance is poor (24/100), better than 91% of steel grades.
Sustainability4
Producing a kilogram of Marval 18 VIM-VAR 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 VIM-VAR's machinability is poor (25/100, worse than 93% of steel grades); weldability excellent (85/100); formability poor (15/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with Marval 18 VIM-VAR
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.
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.
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 | — |
Marval 18 VIM-VAR — frequently asked
What is Marval 18 VIM-VAR used for?
Marval 18 VIM-VAR 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 VIM-VAR?
Marval 18 VIM-VAR has a typical yield strength of 1,920 MPa (278 ksi) and a tensile strength of 1,990 MPa (289 ksi) — stronger than 100% of steel grades. Strength varies by condition: see the 7 listed tempers.
Is Marval 18 VIM-VAR 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 VIM-VAR be welded?
Yes — weldability is rated excellent (85/100). 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 VIM-VAR?
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 VIM-VAR 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 VIM-VAR?
Marval 18 VIM-VAR 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.
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. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.