Steel 18CrNi8 · heat-treated state
Steel 18CrNi8-BG
Properties of the BG condition, compared with the other 18CrNi8 tempers.
Reference condition of EN 10084 used to verify core properties; also used for small parts needing through-hardened high strength.
What is 18CrNi8-BG?
18CrNi8-BG is 18CrNi8 heat treated to BG — reference condition of EN 10084 used to verify core properties; also used for small parts needing through-hardened high strength. 18CrNi8-BG has a yield strength of 900 MPa (131 ksi) and a tensile strength of 1,300 MPa (189 ksi) — stronger than 90% of steel grades. Elongation at break is 9% and the elastic modulus is 210 GPa (30.5 Msi). 18CrNi8-BG has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,420°C (2,588 °F). HR is the default condition FabDigit quotes; BG is available on request or by drawing note.
Advantages
- High strength — 900 MPa (131 ksi), better than 90% of steel grades
- Polishes to a fine finish — 65/100, better than 78% of steel grades
Limitations
- Limited service temperature — 180°C (356 °F), worse than 98% of steel grades
- Difficult to machine — 20/100, worse than 97% of steel grades
- Limited ductility — 9%, worse than 93% of steel grades
- Poor heat conductor — 34 W/m·K (19.6 BTU/hr·ft·°F), worse than 77% of steel grades
18CrNi8-BG properties
Typical room-temperature values for 18CrNi8-BG — 10 properties are specific to this condition; the rest are grade-level values shared by every 18CrNi8 temper. Each bar shows where the value sits among the steel grades in FabDigit's library — further right is higher.
Physical3
18CrNi8-BG has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,420°C (2,588 °F).
Mechanical14
18CrNi8-BG has a yield strength of 900 MPa (131 ksi) and a tensile strength of 1,300 MPa (189 ksi) — stronger than 90% of steel grades. Elongation at break is 9% and the elastic modulus is 210 GPa (30.5 Msi).
Thermal6
18CrNi8-BG is rated for continuous service to 180°C (356 °F). It conducts heat at 34 W/m·K (19.6 BTU/hr·ft·°F), worse than 77% of steel grades. Thermal expansion is 11.6 µm/m·K (6.44 µin/in·°F).
Electrical2
18CrNi8-BG has an electrical resistivity of 2.5×10⁻⁷ Ω·m.
Chemical & Environmental2
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of 18CrNi8-BG takes about 33 MJ of energy and emits 2.3 kg of CO₂ — more than 76% of steel grades. Typical recycled content is 30%.
Manufacturability6
18CrNi8-BG's machinability is poor (20/100, worse than 97% of steel grades); weldability fair (35/100); formability fair (35/100).
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Other 18CrNi8 tempers and conditions
18CrNi8 is also supplied in 9 other conditions. The full side-by-side table is on the 18CrNi8 overview.
- HRDefaultStandard mill delivery for forging, rough machining and subsequent carburizing; hardness is uncontrolled and can be high because of the Cr-Ni content.570 MPa yield · 255 HB
- BGReference condition of EN 10084 used to verify core properties; also used for small parts needing through-hardened high strength.900 MPa yield · 41 HRC
- CHThe functional condition for gears and shafts: hard wear-resistant case with compressive residual stress over a tough 1100–1300 MPa core.880 MPa yield · 60 HRC
- Q&TNon-carburized through-hardened option for shafts and fasteners where toughness matters more than surface wear.830 MPa yield · 31 HRC
- NormalizedUsed to homogenize forgings before final annealing; with 2 % Cr + 2 % Ni air cooling already produces a hard bainitic/martensitic structure.670 MPa yield · 29 HRC
- AnnealedPick for maximum machinability and cold-working ability before carburizing; softest standard delivery condition.440 MPa yield · 205 HB
Working with 18CrNi8-BG
Is 18CrNi8 easy to machine?
Machine in the soft-annealed or +FP condition (≤229 HB) with carbide tooling, moderate speeds and generous coolant; leave 0.2–0.5 mm stock for post-carburizing grinding since 58–62 HRC surfaces need CBN/grinding only.
Can 18CrNi8 be welded?
Weld only in the annealed state with 200–300 °C preheat, low-hydrogen or matching-Ni consumables, then re-normalize/anneal; carburized surfaces must not be welded (cracking, case decarburization).
Can 18CrNi8 be formed, bent or molded?
Hot forge 1100–850 °C with slow cooling and mandatory post-forge normalize + soft anneal; cold heading/upsetting only in the annealed or spheroidized condition.
What surface finishes work on 18CrNi8?
No anodizing (steel); protect with oil, phosphate, black oxide, zinc-nickel or hard chrome; ground and superfinished gear flanks improve fatigue and pitting life, shot peening adds compressive stress.
18CrNi8 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 – 0.2 | 0.18 |
| Si | ≤ 0.4 | 0.25 |
| Mn | 0.4 – 0.6 | 0.5 |
| Pmax (EN 10084) | ≤ 0.03 | — |
| Smax; low-S or controlled-S variants available | ≤ 0.04 | — |
| Cr | 1.8 – 2.1 | 1.95 |
| Ni | 1.8 – 2.1 | 1.95 |
| Moresidual, not intentionally added | ≤ 0.1 | — |
| Fe | balance | — |
18CrNi8-BG — frequently asked
What is 18CrNi8-BG used for?
18CrNi8-BG is typically used for gears, industrial drive shafts and pins. In short: high-strength Ni-Cr bar.
What is the yield strength of 18CrNi8-BG?
18CrNi8-BG has a typical yield strength of 900 MPa (131 ksi) and a tensile strength of 1,300 MPa (189 ksi) — stronger than 90% of steel grades. Strength varies by condition: see the 10 listed tempers.
Is 18CrNi8-BG easy to machine?
Not especially — machinability is rated poor (20/100, worse than 97% of steel grades). Machine in the soft-annealed or +FP condition (≤229 HB) with carbide tooling, moderate speeds and generous coolant; leave 0.2–0.5 mm stock for post-carburizing grinding since 58–62 HRC surfaces need CBN/grinding only.
Can 18CrNi8-BG be welded?
With care — weldability is rated fair (35/100). Weld only in the annealed state with 200–300 °C preheat, low-hydrogen or matching-Ni consumables, then re-normalize/anneal; carburized surfaces must not be welded (cracking, case decarburization).
What surface finishes work on 18CrNi8-BG?
No anodizing (steel); protect with oil, phosphate, black oxide, zinc-nickel or hard chrome; ground and superfinished gear flanks improve fatigue and pitting life, shot peening adds compressive stress.
Can 18CrNi8-BG be formed, bent or molded?
Hot forge 1100–850 °C with slow cooling and mandatory post-forge normalize + soft anneal; cold heading/upsetting only in the annealed or spheroidized condition.
What is the maximum service temperature of 18CrNi8-BG?
18CrNi8-BG is rated for continuous use to about 180°C (356 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between 18CrNi8-HR and 18CrNi8-BG?
HR is the default condition — standard mill delivery for forging, rough machining and subsequent carburizing; hardness is uncontrolled and can be high because of the Cr-Ni content. BG: reference condition of EN 10084 used to verify core properties; also used for small parts needing through-hardened high strength. Yield strength is 570 MPa in HR versus 900 MPa in BG.
Can FabDigit make parts in 18CrNi8-BG?
Yes — 18CrNi8-BG 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)
- DIN 17210 (withdrawn) / SEW 550 case hardening steel data — DIN / VDEh (1987)
- ASM Handbook Vol. 1 — Properties and Selection: Irons, Steels and High-Performance Alloys — ASM International (1990)
- ASM Handbook Vol. 4A — Steel Heat Treating Fundamentals and Processes — ASM International (2013)
- Case-hardening steel 18CrNi8 / 1.5920 bar datasheet — Ovako / Böhler / Lucchini-type mill data (2022)
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.