Steel C300
EN 18Ni Maraging 300 · AMS 6514
C300 (18Ni(300), VascoMax C300, AMS 6514) is an ultra-low-carbon 18% Ni maraging steel with 9% Co, 5% Mo and small Ti and Al additions, strengthened by Ni3Mo/Ni3Ti intermetallic precipitation during aging at 480 °C rather than by carbon quench hardening.
Values for the HR condition
C300 tempers and conditions
C300 is supplied in 8 conditions, soft to hard. HR is the default FabDigit quotes; the values on this page are for it.
Compare all 8 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
900–980 °C grain-refining anneal + air cool (intermediate homogenising treatment) | Intermediate treatment used to refine coarse as-cast/as-forged grain before the 815 °C solution anneal; not a final delivery condition. | 790 | 1,000 | 16 | 31 HRC | 2.9 % IACS |
solution annealed 815 °C / 1 h, air cool (as-supplied soft martensite) | Standard as-shipped condition (~30 HRC): machine, form and weld here, then age to final strength. | 800 | 1,010 | 17 | 30 HRC | — |
HRDefault Hot rolled | Mill hot-worked stock with scale and looser tolerances; solution anneal and age before use. | 850 | 1,050 | 13 | 32 HRC | 2.9 % IACS |
Cold drawn | Bright, close-tolerance bar or wire with modest cold-work strengthening; still machinable and can be aged afterwards. | 1,000 | 1,150 | 10 | 34 HRC | 2.9 % IACS |
Cold rolled | Thin sheet and strip with smooth surface and light cold work; formed to shape then aged (weld first, age last). | 1,050 | 1,180 | 7 | 35 HRC | 2.9 % IACS |
Quenched and tempered | For maraging C300 the hardened condition is solution anneal at 815-830 °C, air cool, then age 3-6 h at 480 °C, giving about 1930 MPa tensile and 52-56 HRC with near-zero distortion instead of a conventional quench-and-temper cycle. | 1,860 | 1,930 | 8 | 54 HRC | 3.1 % IACS |
solution annealed + 480 °C / 3–6 h, air cool | Final full-strength condition (~53 HRC, ~1950 MPa) for aerospace structure, tooling and rotor parts; minimal distortion during aging. | 1,900 | 1,965 | 8 | 53 HRC | 3.8 % IACS |
Cold worked (≈20–50 % reduction) then maraged 480 °C | Highest-strength route for wire, thin strip and springs; strength above 2100 MPa at the cost of ductility and toughness. | 2,050 | 2,120 | 5 | 55 HRC | — |
What is C300?
C300 (18Ni(300), VascoMax C300, AMS 6514) is an ultra-low-carbon 18% Ni maraging steel with 9% Co, 5% Mo and small Ti and Al additions, strengthened by Ni3Mo/Ni3Ti intermetallic precipitation during aging at 480 °C rather than by carbon quench hardening. Solution annealed it is about 30 HRC and machines and cold forms normally; aging then gives roughly 1900–2000 MPa tensile with good fracture toughness and only 0.05–0.1% shrinkage, so finished dimensions stay predictable. Corrosion resistance is poor (plating, passivation or nitriding required), the Ni-Co content makes it expensive, and continuous service above about 400 °C overages and softens it. C300 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). C300 has a yield strength of 850 MPa (123 ksi) and a tensile strength of 1,050 MPa (152 ksi) — stronger than 88% of steel grades. Elongation at break is 13% and the elastic modulus is 186 GPa (27 Msi).
What is C300 used for?
- Rocket motor cases
- Missile bodies
- Centrifuge rotors
- Aerospace structural fittings
- Die-casting dies
- High-strength tooling and punches
Advantages
- Polishes to a fine finish — 78/100, better than 95% of steel grades
- Good corrosion resistance — 22/100, better than 90% of steel grades
- Tough — resists crack growth — 130 MPa·√m (118.3 ksi·√in), better than 89% of steel grades
- High strength — 850 MPa (123 ksi), better than 88% of steel grades
- Readily welded — 80/100, better than 79% of steel grades
Limitations
- High embodied carbon — 7 kg CO₂/kg, worse than 99% of steel grades
- Poor heat conductor — 19.5 W/m·K (11.3 BTU/hr·ft·°F), worse than 97% of steel grades
- Low electrical conductivity — 2.9 % IACS, worse than 93% of steel grades
- Limited ductility — 13%, worse than 78% of steel grades
C300 properties
Typical room-temperature values for C300-HR; bars are the position among steel grades.
Physical3
C300 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
C300 has a yield strength of 850 MPa (123 ksi) and a tensile strength of 1,050 MPa (152 ksi) — stronger than 88% of steel grades. Elongation at break is 13% and the elastic modulus is 186 GPa (27 Msi).
Thermal6
C300 is rated for continuous service to 400°C (752 °F). It conducts heat at 19.5 W/m·K (11.3 BTU/hr·ft·°F), worse than 97% of steel grades. Thermal expansion is 10.1 µm/m·K (5.61 µin/in·°F).
Electrical3
C300 conducts electricity at 2.9 % IACS, worse than 93% of steel grades.
Chemical & Environmental3
Corrosion resistance is poor (22/100), better than 90% of steel grades.
Sustainability4
Producing a kilogram of C300 takes about 105 MJ of energy and emits 7 kg of CO₂ — more than 99% of steel grades. Typical recycled content is 20%.
Manufacturability7
C300's machinability is fair (42/100, worse than 73% of steel grades); weldability very good (80/100); formability good (55/100).
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. C300 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with C300
Is C300 easy to machine?
Machine in the annealed condition (~30 HRC) with sharp carbide tooling, rigid setups and generous coolant; it is gummy and work-hardens, so use positive rake, moderate speeds and heavy feeds — aged material at 53 HRC needs grinding or ceramic/CBN finishing.
Can C300 be welded?
Excellent weldability by GTAW/EB/laser with matching low-carbon filler, no preheat and low heat input; solution-anneal or at minimum re-age at 480 °C after welding to restore joint strength, and keep the weld area free of oil, moisture and hydrogen.
Can C300 be formed, bent or molded?
Form, bend, deep-draw or spin in the annealed state where ductility is 15–20 %; aging causes only ~0.05–0.1 % uniform shrinkage, so finished dimensions are predictable after heat treatment.
Manufacturability
The process limits FabDigit applies to C300. Every C300 part is priced by an engineer; design inside these and the quote comes back without a redesign loop.
CNC machining
| Machinability | Fair42 / 100 |
|---|---|
| ISO material group | P.2 |
| Cutting speed (rough / finish) | 180 / 210 m/min |
| Minimum wall | 0.8 mm |
| Minimum internal radius | 1 mm |
| Drill depth limit | 5× diameter |
| Best surface (machined / polished) | Ra 1.6 / — |
| Hardenable after machining | No |
Sheet metal
| Formability | Fair55 / 100 |
|---|---|
| Weldability | Better80 / 100 |
C300 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 is essential | ≤ 0.03 | 0.01 |
| Ni | 18 – 19 | 18.5 |
| Co | 8.5 – 9.5 | 9 |
| Moforms Ni3Mo on aging | 4.6 – 5.2 | 4.9 |
| Timain strength lever vs 18Ni-250 | 0.55 – 0.8 | 0.65 |
| 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 |
| Bgrain-boundary addition (optional) | ≤ 0 | 0 |
| Zroptional addition | ≤ 0.02 | 0.01 |
| Caoptional deoxidiser | ≤ 0.05 | 0.02 |
| Fe | balance |
What surface finishes work on C300?
Not corrosion resistant — protect with nitriding (raises surface to 65+ HRC), hard chrome, electroless nickel, cadmium/zinc-nickel or phosphate plus paint; avoid embrittling acid pickling and always bake after electroplating to relieve hydrogen.
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).
Plating
CVD Coating
Black / Phosphate
Thermal Spray
Equivalent designations
Standards and trade names that resolve to Steel C300 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- AMS
- 6514
- EN / DIN / Werkstoff-Nr.
- 18Ni Maraging 300
How much does C300 cost?
C300 is a specialty-cost steel ($$$$$), pricier than about 99% 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.
C300 — frequently asked
What is C300 used for?
C300 is typically used for rocket motor cases, missile bodies, centrifuge rotors, aerospace structural fittings, die-casting dies and high-strength tooling and punches. In short: ultra-strong maraging steel.
What is the yield strength of C300?
C300 has a typical yield strength of 850 MPa (123 ksi) and a tensile strength of 1,050 MPa (152 ksi) — stronger than 88% of steel grades. Strength varies by condition: see the 8 listed tempers.
Is C300 easy to machine?
Not especially — machinability is rated fair (42/100, worse than 73% of steel grades). Machine in the annealed condition (~30 HRC) with sharp carbide tooling, rigid setups and generous coolant; it is gummy and work-hardens, so use positive rake, moderate speeds and heavy feeds — aged material at 53 HRC needs grinding or ceramic/CBN finishing.
Can C300 be welded?
Yes — weldability is rated very good (80/100). Excellent weldability by GTAW/EB/laser with matching low-carbon filler, no preheat and low heat input; solution-anneal or at minimum re-age at 480 °C after welding to restore joint strength, and keep the weld area free of oil, moisture and hydrogen.
What surface finishes work on C300?
Not corrosion resistant — protect with nitriding (raises surface to 65+ HRC), hard chrome, electroless nickel, cadmium/zinc-nickel or phosphate plus paint; avoid embrittling acid pickling and always bake after electroplating to relieve hydrogen.
Can C300 be formed, bent or molded?
Form, bend, deep-draw or spin in the annealed state where ductility is 15–20 %; aging causes only ~0.05–0.1 % uniform shrinkage, so finished dimensions are predictable after heat treatment.
What is the maximum service temperature of C300?
C300 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 C300-HR and C300 Aged?
HR is the default condition — mill hot-worked stock with scale and looser tolerances; solution anneal and age before use. Aged: final full-strength condition (~53 HRC, ~1950 MPa) for aerospace structure, tooling and rotor parts; minimal distortion during aging. Yield strength is 850 MPa in HR versus 1,900 MPa in Aged.
How much does C300 cost?
C300 is a specialty-cost steel ($$$$$), pricier than about 99% 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.
Can FabDigit make parts in C300?
Yes — C300 is available for CNC machining and sheet metal; every part is priced by an engineer rather than instantly. Upload a STEP file to get a price and a DFM check.
Sources
- AMS 6514 — Steel, Maraging, Bars, Forgings, Tubing and Rings, 18.5Ni-9.0Co-4.9Mo-0.65Ti — SAE International (2019)
- AMS 6521 — Maraging 300 Sheet, Strip and Plate — SAE International (2018)
- ASTM A538/A538M — Pressure Vessel Plates, Maraging Steels (Grade C, 18Ni-300) — ASTM (2018)
- ASM Specialty Handbook: Tool Materials / Maraging Steels chapter — ASM International (1995)
- ASM Handbook Vol.1: Properties and Selection — Irons, Steels and High-Performance Alloys — ASM International (1990)
- VascoMax C300 maraging steel datasheet — Carpenter Technology / Latrobe (2021)
- MMPDS-2023 maraging steel allowables — Battelle/FAA (2023)
- GB/T 34474 / 00Ni18Co9Mo5TiAl (2017)
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.