Steel C300 · supply condition · default condition
Steel C300-HR
Properties of the HR condition, compared with the other C300 tempers.
Mill hot-worked stock with scale and looser tolerances; solution anneal and age before use.
What is C300-HR?
C300-HR is C300 supplied in the HR condition — mill hot-worked stock with scale and looser tolerances; solution anneal and age before use. C300-HR 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). C300-HR 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).
Advantages
- Polishes to a fine finish — 78/100, better than 95% of steel grades
- Good corrosion resistance — 22/100, better than 89% of steel grades
- High strength — 850 MPa (123 ksi), better than 88% of steel grades
- Readily welded — 80/100, better than 80% of steel grades
- Forms and bends easily — 62/100, better than 78% of steel grades
Limitations
- High embodied carbon — 7 kg CO₂/kg, worse than 98% 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-HR properties
Typical room-temperature values for C300-HR — 7 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-HR 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-HR 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-HR 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-HR conducts electricity at 2.9 % IACS, worse than 93% of steel grades.
Chemical & Environmental3
Corrosion resistance is poor (22/100), better than 89% of steel grades.
Sustainability4
Producing a kilogram of C300-HR 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-HR's machinability is fair (42/100, worse than 72% of steel grades); weldability very good (80/100); formability good (62/100).
Common Calculations5
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-HR
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-HR — frequently asked
What is C300-HR used for?
C300-HR 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-HR?
C300-HR 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 7 listed tempers.
Is C300-HR easy to machine?
Not especially — machinability is rated fair (42/100, worse than 72% 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-HR 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-HR?
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-HR 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-HR?
C300-HR 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-HR?
Yes — C300-HR 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.