Steel 18Ni350 SA+A
Precip hard · default condition
EN 18Ni350
SA+A = solution annealed + aged 490 °C/6 h
Standard delivered/ finished condition for tooling and high-stress parts — maximum strength and hardness at ~2400 MPa.
Values for the SA+A condition
Other 18Ni350 tempers and conditions
18Ni350 is listed in 7 conditions; see the grade overview at 18Ni350.
Compare all 7 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Solution annealed 815 °C/1 h, air cooled | Machining and forming condition — soft, tough and dimensionally stable before the low-distortion aging step. | 860 | 1,100 | 15 | 32 HRC | 19 W/m·K |
As built (as printed) | Printed and stress-relieved but not aged — machine/EDM features in this softer state before hardening. | 1,000 | 1,180 | 9 | 37 HRC | 2.4 % IACS |
As-built L-PBF + direct age 490 °C/6 h | Fastest route to hardened AM tooling inserts — near-full strength with minimal distortion, but lower ductility than wrought. | 2,000 | 2,100 | 3 | 56 HRC | 2.7 % IACS |
Solution annealed + under-aged 480 °C/3 h | Choose when a little strength can be traded for higher fracture toughness and impact energy in thick or notch-sensitive sections. | 2,100 | 2,200 | 9 | 54 HRC | 2.6 % IACS |
Hot isostatic pressed, solution annealed and aged | Specify for fatigue-critical or aerospace AM parts where residual porosity must be closed and properties matched to wrought. | 2,250 | 2,350 | 6 | 57 HRC | 2.7 % IACS |
SA+ADefaultThis page Solution annealed + aged 490 °C/6 h | Standard delivered/ finished condition for tooling and high-stress parts — maximum strength and hardness at ~2400 MPa. | 2,300 | 2,400 | 7 | 57 HRC | 15 W/m·K |
Aged then gas/plasma nitrided surface | Use for punches, dies and wear surfaces — nitriding at the aging temperature range adds a ~1100 HV case without softening the core. | 2,300 | 2,400 | 5 | 57 HRC | 2.7 % IACS |
What is 18Ni350 SA+A?
18Ni350 SA+A is 18Ni350 in the SA+A condition — standard delivered/ finished condition for tooling and high-stress parts — maximum strength and hardness at ~2400 MPa. 18Ni350 SA+A has a yield strength of 2,300 MPa (334 ksi) and a tensile strength of 2,400 MPa (348 ksi) — stronger than 100% of steel grades. Elongation at break is 7% and the elastic modulus is 190 GPa (27.6 Msi). 18Ni350 SA+A has a density of 8.08 g/cm³ (0.292 lb/in³), heavier than 96% of steel grades. It melts at 1,413°C (2,575 °F).
Advantages
- High strength — 2,300 MPa (334 ksi), better than 100% of steel grades
- Polishes to a fine finish — 85/100, better than 99% of steel grades
- Good corrosion resistance — 25/100, better than 92% of steel grades
Limitations
- Poor heat conductor — 15 W/m·K (8.67 BTU/hr·ft·°F), worse than 98% of steel grades
- Difficult to machine — 18/100, worse than 97% of steel grades
- Limited ductility — 7%, worse than 96% of steel grades
- Low electrical conductivity — 2.7 % IACS, worse than 96% of steel grades
- High embodied carbon — 5.2 kg CO₂/kg, worse than 96% of steel grades
18Ni350 SA+A properties
Typical room-temperature values for 18Ni350 SA+A; 16 are specific to this condition. Other listed values are 18Ni350 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
18Ni350 SA+A has a density of 8.08 g/cm³ (0.292 lb/in³), heavier than 96% of steel grades. It melts at 1,413°C (2,575 °F).
Mechanical15
18Ni350 SA+A has a yield strength of 2,300 MPa (334 ksi) and a tensile strength of 2,400 MPa (348 ksi) — stronger than 100% of steel grades. Elongation at break is 7% and the elastic modulus is 190 GPa (27.6 Msi).
Thermal6
18Ni350 SA+A is rated for continuous service to 400°C (752 °F). It conducts heat at 15 W/m·K (8.67 BTU/hr·ft·°F), worse than 98% of steel grades. Thermal expansion is 10.3 µm/m·K (5.72 µin/in·°F).
Electrical3
18Ni350 SA+A conducts electricity at 2.7 % IACS, worse than 96% of steel grades.
Chemical & Environmental3
Corrosion resistance is poor (25/100), better than 92% of steel grades.
Sustainability4
Producing a kilogram of 18Ni350 SA+A takes about 70 MJ of energy and emits 5.2 kg of CO₂ — more than 97% of steel grades. Typical recycled content is 20%.
Manufacturability7
18Ni350 SA+A's machinability is poor (18/100, worse than 97% of steel grades); weldability good (55/100); formability poor (20/100).
Common Calculations5
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 18Ni350 SA+A
Is 18Ni350 easy to machine?
Rough machine in the solution-annealed state (~32 HRC) with sharp carbide tooling and rigid setups; after aging to 57 HRC use grinding, EDM or CBN only.
Can 18Ni350 be welded?
Excellent TIG/laser/EB weldability with matching filler and no preheat — weld annealed, then age the whole part; keep heat input low and interpass cool to limit reverted austenite.
Can 18Ni350 be formed, bent or molded?
Cold form or bend only when annealed; aging causes just ~0.05 % shrinkage so parts can be finished near net size before hardening, and L-PBF prints readily with low cracking risk.
What surface finishes work on 18Ni350?
Polishes to mirror for mould surfaces; not corrosion resistant, so nitride, hard chrome/electroless nickel plate, black oxide or oil for storage and service.
18Ni350 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 |
|---|---|---|
| Ni | 18 – 19 | 18.5 |
| Co | 11 – 12.5 | 12 |
| Mo | 4.6 – 5.2 | 4.9 |
| Tiprincipal age-hardening element vs 18Ni300 | 1.3 – 1.6 | 1.45 |
| Al | 0.05 – 0.15 | 0.1 |
| C | ≤ 0.03 | 0.01 |
| Si | ≤ 0.1 | 0.05 |
| Mn | ≤ 0.1 | 0.05 |
| P | ≤ 0.01 | 0.01 |
| S | ≤ 0.01 | 0.01 |
| Bgrain refining addition, optional | ≤ 0 | 0 |
| Zroptional | ≤ 0.02 | 0.01 |
| Fe | balance | — |
18Ni350 SA+A — frequently asked
What is 18Ni350 SA+A used for?
18Ni350 SA+A is typically used for mold inserts, aerospace tooling and high-strength brackets. In short: highest-strength maraging powder; machine soft, age to 57 HRC; near-zero aging distortion.
What is the yield strength of 18Ni350 SA+A?
18Ni350 SA+A has a typical yield strength of 2,300 MPa (334 ksi) and a tensile strength of 2,400 MPa (348 ksi) — stronger than 100% of steel grades. Strength varies by condition: see the 7 listed tempers.
Is 18Ni350 SA+A easy to machine?
Not especially — machinability is rated poor (18/100, worse than 97% of steel grades). Rough machine in the solution-annealed state (~32 HRC) with sharp carbide tooling and rigid setups; after aging to 57 HRC use grinding, EDM or CBN only.
Can 18Ni350 SA+A be welded?
Yes — weldability is rated good (55/100). Excellent TIG/laser/EB weldability with matching filler and no preheat — weld annealed, then age the whole part; keep heat input low and interpass cool to limit reverted austenite.
What surface finishes work on 18Ni350 SA+A?
Polishes to mirror for mould surfaces; not corrosion resistant, so nitride, hard chrome/electroless nickel plate, black oxide or oil for storage and service.
Can 18Ni350 SA+A be formed, bent or molded?
Cold form or bend only when annealed; aging causes just ~0.05 % shrinkage so parts can be finished near net size before hardening, and L-PBF prints readily with low cracking risk.
What is the maximum service temperature of 18Ni350 SA+A?
18Ni350 SA+A 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 18Ni350 SA+A and 18Ni350-SA?
SA+A is the default condition — standard delivered/ finished condition for tooling and high-stress parts — maximum strength and hardness at ~2400 MPa. SA: machining and forming condition — soft, tough and dimensionally stable before the low-distortion aging step. Yield strength is 2,300 MPa in SA+A versus 860 MPa in SA.
Sources
- AMS 6515 — Steel, Maraging Bars, Forgings and Tubing 18Ni(350) — SAE International (2019)
- ASM Specialty Handbook: Maraging Steels (in Tool Materials / Carbon and Alloy Steels) — ASM International (1996)
- ASM Handbook Vol. 1 — Properties and Selection: Irons, Steels and High-Performance Alloys — ASM International (1990)
- Maraging steel 18Ni350 / MS1-350 powder data sheets — Various AM powder producers (Sandvik Osprey, Höganäs, CNPC/ ) (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.