Steel 18CrNiMo7-6 · heat-treated state
Steel 18CrNiMo7-6 Spheroidized (+AC)
Properties of the Spheroidized (+AC) condition, compared with the other 18CrNiMo7-6 tempers.
EN 10084 soft-annealed condition with globular carbides, giving the lowest hardness and the best cold formability for extrusion, upsetting and heavy machining before carburizing.
What is 18CrNiMo7-6 Spheroidized (+AC)?
18CrNiMo7-6 Spheroidized (+AC) is 18CrNiMo7-6 heat treated to Spheroidized (+AC) — eN 10084 soft-annealed condition with globular carbides, giving the lowest hardness and the best cold formability for extrusion, upsetting and heavy machining before carburizing. 18CrNiMo7-6 Spheroidized (+AC) has a yield strength of 360 MPa (52.2 ksi) and a tensile strength of 590 MPa (85.6 ksi) — weaker than 72% of steel grades. Elongation at break is 22% and the elastic modulus is 210 GPa (30.5 Msi). 18CrNiMo7-6 Spheroidized (+AC) has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,430°C (2,606 °F). Annealed is the default condition FabDigit quotes; Spheroidized (+AC) is available on request or by drawing note.
Advantages
- Forms and bends easily — 62/100, better than 78% of steel grades
Limitations
- Limited service temperature — 300°C (572 °F), worse than 77% of steel grades
18CrNiMo7-6 Spheroidized (+AC) properties
Typical room-temperature values for 18CrNiMo7-6 Spheroidized (+AC) — 39 properties are specific to this condition; the rest are grade-level values shared by every 18CrNiMo7-6 temper. Each bar shows where the value sits among the steel grades in FabDigit's library — further right is higher.
Physical3
18CrNiMo7-6 Spheroidized (+AC) has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,430°C (2,606 °F).
Mechanical15
18CrNiMo7-6 Spheroidized (+AC) has a yield strength of 360 MPa (52.2 ksi) and a tensile strength of 590 MPa (85.6 ksi) — weaker than 72% of steel grades. Elongation at break is 22% and the elastic modulus is 210 GPa (30.5 Msi).
Thermal6
18CrNiMo7-6 Spheroidized (+AC) is rated for continuous service to 300°C (572 °F). It conducts heat at 35 W/m·K (20.2 BTU/hr·ft·°F), worse than 74% of steel grades. Thermal expansion is 11.9 µm/m·K (6.61 µin/in·°F).
Electrical3
18CrNiMo7-6 Spheroidized (+AC) conducts electricity at 8 % IACS, better than 55% of steel grades.
Chemical & Environmental2
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of 18CrNiMo7-6 Spheroidized (+AC) takes about 34 MJ of energy and emits 2.3 kg of CO₂ — more than 82% of steel grades. Typical recycled content is 30%.
Manufacturability8
18CrNiMo7-6 Spheroidized (+AC)'s machinability is good (58/100, better than 75% of steel grades); weldability fair (45/100); formability good (62/100).
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Other 18CrNiMo7-6 tempers and conditions
18CrNiMo7-6 is also supplied in 9 other conditions. The full side-by-side table is on the 18CrNiMo7-6 overview.
- AnnealedDefaultStandard delivery condition for machining of gear blanks before carburizing.370 MPa yield · 200 HB
- Carburized 58-62 HRCFinal service condition for heavy-duty gears: hard wear-resistant case with compressive residual stress over a tough core.950 MPa yield · 60 HRC
- Blank HardenedReference condition used to verify core mechanical properties per EN 10084.850 MPa yield · 38 HRC
- Q&T 28-32 HRCChoose when the part is used as a through-hardened shaft rather than a carburized gear.800 MPa yield · 30 HRC
- NormalizedUniform fine-grained structure for forgings prior to machining and carburizing.550 MPa yield · 250 HB
- High Shearability (+S)EN 10084 condition softened only enough to cap hardness (~≤255 HB) so bar can be cold-sheared into blanks without cracking the shear tooling.500 MPa yield · 21 HRC
- Heat Treated (+TH)EN 10084 delivery condition treated to a controlled Brinell band (~179–229 HB) so bar and forging stock machines predictably before carburizing.450 MPa yield · 205 HB
- Spheroidized (+AC)EN 10084 soft-annealed condition with globular carbides, giving the lowest hardness and the best cold formability for extrusion, upsetting and heavy machining before carburizing.360 MPa yield · 175 HB
Working with 18CrNiMo7-6 Spheroidized (+AC)
Is 18CrNiMo7-6 easy to machine?
Machine all gear geometry in the soft-annealed state (≈55% of 1212); after carburizing only grinding, honing or hard skiving with CBN is practical.
Can 18CrNiMo7-6 be welded?
Weldable only with care — preheat 200–250 °C, low-hydrogen consumables and immediate stress relief; never weld carburized surfaces.
Can 18CrNiMo7-6 be formed, bent or molded?
Hot forge at 1050–1150 °C then normalize; cold forming limited to annealed small-section bar with generous radii.
What surface finishes work on 18CrNiMo7-6?
Not anodizable — use phosphating, black oxide, oil or Zn-Ni plating (bake to avoid hydrogen embrittlement); shot peening of tooth roots markedly raises bending fatigue life.
18CrNiMo7-6 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 |
|---|---|---|
| C | 0.15 – 0.21 | 0.18 |
| Si | ≤ 0.4 | 0.25 |
| Mn | 0.5 – 0.9 | 0.7 |
| P | ≤ 0.03 | — |
| Smax; low-S (≤0.015) variants used for wind-turbine gears | ≤ 0.04 | — |
| Cr | 1.5 – 1.8 | 1.65 |
| Mo | 0.25 – 0.35 | 0.3 |
| Ni | 1.4 – 1.7 | 1.55 |
| Fe | balance | — |
18CrNiMo7-6 Spheroidized (+AC) — frequently asked
What is 18CrNiMo7-6 Spheroidized (+AC) used for?
18CrNiMo7-6 Spheroidized (+AC) is typically used for wind-turbine gearbox gears, heavy industrial spur and helical gears, drive shafts and pinion shafts, planet carriers and planetary pinions, marine and rail gearbox components and bevel and hypoid gears. In short: premium gear-steel bar.
What is the yield strength of 18CrNiMo7-6 Spheroidized (+AC)?
18CrNiMo7-6 Spheroidized (+AC) has a typical yield strength of 360 MPa (52.2 ksi) and a tensile strength of 590 MPa (85.6 ksi) — weaker than 72% of steel grades. Strength varies by condition: see the 10 listed tempers.
Is 18CrNiMo7-6 Spheroidized (+AC) easy to machine?
Reasonably — machinability is rated good (58/100, better than 75% of steel grades). Machine all gear geometry in the soft-annealed state (≈55% of 1212); after carburizing only grinding, honing or hard skiving with CBN is practical.
Can 18CrNiMo7-6 Spheroidized (+AC) be welded?
With care — weldability is rated fair (45/100). Weldable only with care — preheat 200–250 °C, low-hydrogen consumables and immediate stress relief; never weld carburized surfaces.
What surface finishes work on 18CrNiMo7-6 Spheroidized (+AC)?
Not anodizable — use phosphating, black oxide, oil or Zn-Ni plating (bake to avoid hydrogen embrittlement); shot peening of tooth roots markedly raises bending fatigue life.
Can 18CrNiMo7-6 Spheroidized (+AC) be formed, bent or molded?
Hot forge at 1050–1150 °C then normalize; cold forming limited to annealed small-section bar with generous radii.
What is the maximum service temperature of 18CrNiMo7-6 Spheroidized (+AC)?
18CrNiMo7-6 Spheroidized (+AC) is rated for continuous use to about 300°C (572 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
Can FabDigit make parts in 18CrNiMo7-6 Spheroidized (+AC)?
Yes — 18CrNiMo7-6 Spheroidized (+AC) 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
- EN 10084 — Case hardening steels: technical delivery conditions — CEN (2008)
- EN 10263-4 / EN ISO 683-3 case-hardening steel designations — CEN/ISO (2018)
- 18CrNiMo7-6 (1.6587) gear steel data sheet — Ovako / Böhler / Dörrenberg (2022)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels — ASM International (1990)
- ASM Handbook Vol.4 — Heat Treating (carburizing of gear steels) — ASM International (1991)
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.