Steel C300 · heat-treated state
Steel C300 Aged
Properties of the Aged condition, compared with the other C300 tempers.
Final full-strength condition (~53 HRC, ~1950 MPa) for aerospace structure, tooling and rotor parts; minimal distortion during aging.
What is C300 Aged?
C300 Aged is C300 heat treated to Aged — final full-strength condition (~53 HRC, ~1950 MPa) for aerospace structure, tooling and rotor parts; minimal distortion during aging. C300 Aged has a yield strength of 1,900 MPa (276 ksi) and a tensile strength of 1,965 MPa (285 ksi) — stronger than 100% of steel grades. Elongation at break is 8% and the elastic modulus is 190 GPa (27.6 Msi). C300 Aged 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). HR is the default condition FabDigit quotes; Aged is available on request or by drawing note.
Advantages
- High strength — 1,900 MPa (276 ksi), better than 100% of steel grades
- Polishes to a fine finish — 85/100, better than 99% of steel grades
- Good corrosion resistance — 22/100, better than 89% of steel grades
Limitations
- High embodied carbon — 7 kg CO₂/kg, worse than 98% of steel grades
- Limited ductility — 8%, worse than 95% of steel grades
- Poor heat conductor — 20.5 W/m·K (11.8 BTU/hr·ft·°F), worse than 95% of steel grades
- Difficult to machine — 25/100, worse than 93% of steel grades
- Limited formability — 12/100, worse than 91% of steel grades
C300 Aged properties
Typical room-temperature values for C300 Aged — 25 properties are specific to this condition; the rest are grade-level values shared by every C300 temper. Each bar shows where the value sits among the steel grades in FabDigit's library — further right is higher.
Physical3
C300 Aged 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).
Mechanical15
C300 Aged has a yield strength of 1,900 MPa (276 ksi) and a tensile strength of 1,965 MPa (285 ksi) — stronger than 100% of steel grades. Elongation at break is 8% and the elastic modulus is 190 GPa (27.6 Msi).
Thermal6
C300 Aged is rated for continuous service to 400°C (752 °F). It conducts heat at 20.5 W/m·K (11.8 BTU/hr·ft·°F), worse than 95% of steel grades. Thermal expansion is 10.1 µm/m·K (5.61 µin/in·°F).
Electrical3
C300 Aged conducts electricity at 3.8 % IACS, worse than 84% of steel grades.
Chemical & Environmental3
Corrosion resistance is poor (22/100), better than 89% of steel grades.
Sustainability4
Producing a kilogram of C300 Aged 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 Aged's machinability is poor (25/100, worse than 93% of steel grades); weldability good (55/100); formability not recommended (12/100).
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Other C300 tempers and conditions
C300 is also supplied in 6 other conditions. The full side-by-side table is on the C300 overview.
- HRDefaultMill hot-worked stock with scale and looser tolerances; solution anneal and age before use.850 MPa yield · 32 HRC
- CW+AgedHighest-strength route for wire, thin strip and springs; strength above 2100 MPa at the cost of ductility and toughness.2,050 MPa yield · 55 HRC
- AgedFinal full-strength condition (~53 HRC, ~1950 MPa) for aerospace structure, tooling and rotor parts; minimal distortion during aging.1,900 MPa yield · 53 HRC
- CDBright, close-tolerance bar or wire with modest cold-work strengthening; still machinable and can be aged afterwards.1,000 MPa yield · 34 HRC
- AnnealedStandard as-shipped condition (~30 HRC): machine, form and weld here, then age to final strength.800 MPa yield · 30 HRC
Working with C300 Aged
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.
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.
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 | — |
C300 Aged — frequently asked
What is C300 Aged used for?
C300 Aged 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 Aged?
C300 Aged has a typical yield strength of 1,900 MPa (276 ksi) and a tensile strength of 1,965 MPa (285 ksi) — stronger than 100% of steel grades. Strength varies by condition: see the 7 listed tempers.
Is C300 Aged easy to machine?
Not especially — machinability is rated poor (25/100, worse than 93% 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 Aged be welded?
Yes — weldability is rated good (55/100). 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 Aged?
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 Aged 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 Aged?
C300 Aged 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.
Can FabDigit make parts in C300 Aged?
Yes — C300 Aged is available for CNC machining and sheet metal with instant online pricing. 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. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.