Steel 18NCD6
EN 18NCD6
18NCD6 is an AFNOR nickel-chromium-molybdenum carburizing steel comparable to AISI 8620, used where a hard case and a tough, moderately strong core are both needed.
Reference datasheet — 18NCD6 is not in the instant-quote catalog. Upload your part and an engineer will quote it in this grade or suggest the closest stocked equivalent.
Values for the A condition
18NCD6 tempers and conditions
18NCD6 is supplied in 7 conditions, soft to hard. A is the default FabDigit quotes; the values on this page are for it.
Compare all 7 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
ADefault Solution annealed | Standard as-supplied bar state: lowest hardness and best machinability for rough-cutting gear blanks before case hardening by carburizing and quenching. | 370 | 580 | 24 | 170 HB | — |
Normalized | Normalize at about 880–900 °C and air cool to refine and homogenize forgings and bar, either in preparation for carburizing or for medium-strength non-carburized parts. | 430 | 680 | 20 | 14 HRC | 7.8 % IACS |
Hot rolled | Most economical blank supply form; as-rolled tolerances and surface are coarse, so normalize or anneal before machining to reach usable structure and finish. | 440 | 700 | 19 | 15 HRC | 7.8 % IACS |
Cold drawn | Choose for small- and medium-diameter shaft blanks machined directly from bar: annealing plus cold drawing gives 580 MPa yield with close size tolerance and good surface, at reduced formability. | 580 | 700 | 12 | 16 HRC | 7.8 % IACS |
Q&T 28–34 HRC | Pick when the part runs through-hardened and tempered to 28–34 HRC without carburizing, for medium-strength shafts, or to verify the core properties of carburized components. | 800 | 1,000 | 15 | 31 HRC | — |
Carburized and hardened | Specify the intended service state — carburized, hardened and low-temperature tempered — for gears, splined shafts and bearing rings needing a 58–62 HRC wear case over a tough core; machine beforehand. | 900 | 1,150 | 11 | 60 HRC | — |
Q&T 36–42 HRC | Use the lower tempering temperature route to 36–42 HRC for heavily loaded non-carburized shafts and connecting rods; tensile reaches 1250 MPa but elongation drops to 12% and machining is harder. | 1,050 | 1,250 | 12 | 39 HRC | — |
What is 18NCD6?
18NCD6 is an AFNOR nickel-chromium-molybdenum carburizing steel comparable to AISI 8620, used where a hard case and a tough, moderately strong core are both needed. Annealed values are 370 MPa yield, 580 MPa tensile, 24 % elongation and 170 HB (87 HRB), with machinability 58 and formability 60; it is supplied as hot-rolled, annealed, normalized and cold-drawn bar and forging stock. The molybdenum addition improves hardenability over 16NC6 and 20MC5, but the steel has no corrosion resistance and cannot be welded after carburizing. 18NCD6 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). 18NCD6 has a yield strength of 370 MPa (53.7 ksi) and a tensile strength of 580 MPa (84.1 ksi) — weaker than 70% of steel grades. Elongation at break is 24% and the elastic modulus is 207 GPa (30 Msi).
What is 18NCD6 used for?
- gears
- shafts
- pinions
Advantages
- Polishes to a fine finish — 65/100, better than 78% of steel grades
Limitations
- Limited service temperature — 200°C (392 °F), worse than 93% of steel grades
18NCD6 properties
Typical room-temperature values for 18NCD6-A; bars are the position among steel grades.
Physical3
18NCD6 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).
Mechanical13
18NCD6 has a yield strength of 370 MPa (53.7 ksi) and a tensile strength of 580 MPa (84.1 ksi) — weaker than 70% of steel grades. Elongation at break is 24% and the elastic modulus is 207 GPa (30 Msi).
Thermal6
18NCD6 is rated for continuous service to 200°C (392 °F). It conducts heat at 43 W/m·K (24.8 BTU/hr·ft·°F), better than 51% of steel grades. Thermal expansion is 11.6 µm/m·K (6.44 µin/in·°F).
Electrical3
18NCD6 conducts electricity at 7.8 % IACS, worse than 57% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of 18NCD6 takes about 29 MJ of energy and emits 2.1 kg of CO₂ — less than 53% of steel grades. Typical recycled content is 25%.
Manufacturability7
18NCD6's machinability is good (58/100, better than 75% of steel grades); weldability fair (45/100); formability good (60/100).
Common Calculations5
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Strength versus weight in the steel family
Yield strength against density for every steel grade FabDigit runs. 18NCD6 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with 18NCD6
Is 18NCD6 easy to machine?
In the annealed or normalized condition it turns and mills efficiently with carbide tooling at roughly 60–65 % of 1212 machinability. After carburizing and quenching, use grinding or hard turning with CBN only.
Can 18NCD6 be welded?
Carbon equivalent is about 0.6–0.7, so it is weldable with 150–250 °C preheat, low-hydrogen consumables and a post-weld temper. Do not weld in or near carburized surface layers.
Can 18NCD6 be formed, bent or molded?
The annealed condition suits hot forging at 1150–1200 °C with finishing above 850 °C, and moderate cold heading. Normalize after forging to refine the structure before carburizing.
18NCD6 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 |
|---|---|---|
| CLow-carbon core of carburizing steel | 0.15 – 0.21 | 0.18 |
| Si | 0.1 – 0.4 | 0.25 |
| Mn | 0.5 – 0.9 | 0.7 |
| P | ≤ 0.04 | |
| Smax; free-machining variants up to 0.020-0.035 | ≤ 0.04 | |
| Cr | 0.8 – 1.15 | 0.95 |
| NiAFNOR grade digit 6 corresponds to Ni approx. 1.5% | 1.3 – 1.75 | 1.5 |
| Mo | 0.15 – 0.3 | 0.22 |
| Fe | balance |
What surface finishes work on 18NCD6?
No corrosion resistance: black oxide, phosphate, zinc or nickel plating, or rust-preventive oil on non-carburized surfaces. Carburized and ground tooth flanks are usually shot peened to raise bending fatigue life.
Surface treatments FabDigit runs on steel parts — pick them in the quote configurator or call them out on the drawing. Each links to its datasheet in the surface-finish library (thickness, specs, call-out, material verdicts).
Organic Coating
Black / Phosphate
Thermal Spray
Equivalent designations
Standards and trade names that resolve to Steel 18NCD6 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- Similar grades
- 8620
How much does 18NCD6 cost?
18NCD6 is a budget-cost steel ($), cheaper than about 90% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
18NCD6 — frequently asked
What is 18NCD6 used for?
18NCD6 is typically used for gears, shafts and pinions. In short: 8620-equivalent gear steel; mo-boosted hardenability; machines well before carburizing.
What is the yield strength of 18NCD6?
18NCD6 has a typical yield strength of 370 MPa (53.7 ksi) and a tensile strength of 580 MPa (84.1 ksi) — weaker than 70% of steel grades. Strength varies by condition: see the 7 listed tempers.
Is 18NCD6 easy to machine?
Reasonably — machinability is rated good (58/100, better than 75% of steel grades). In the annealed or normalized condition it turns and mills efficiently with carbide tooling at roughly 60–65 % of 1212 machinability. After carburizing and quenching, use grinding or hard turning with CBN only.
Can 18NCD6 be welded?
With care — weldability is rated fair (45/100). Carbon equivalent is about 0.6–0.7, so it is weldable with 150–250 °C preheat, low-hydrogen consumables and a post-weld temper. Do not weld in or near carburized surface layers.
What surface finishes work on 18NCD6?
No corrosion resistance: black oxide, phosphate, zinc or nickel plating, or rust-preventive oil on non-carburized surfaces. Carburized and ground tooth flanks are usually shot peened to raise bending fatigue life.
Can 18NCD6 be formed, bent or molded?
The annealed condition suits hot forging at 1150–1200 °C with finishing above 850 °C, and moderate cold heading. Normalize after forging to refine the structure before carburizing.
What is the maximum service temperature of 18NCD6?
18NCD6 is rated for continuous use to about 200°C (392 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between 18NCD6-A and 18NCD6 QT-38?
A is the default condition — standard as-supplied bar state: lowest hardness and best machinability for rough-cutting gear blanks before case hardening by carburizing and quenching. QT-38: use the lower tempering temperature route to 36–42 HRC for heavily loaded non-carburized shafts and connecting rods; tensile reaches 1250 MPa but elongation drops to 12% and machining is harder. Yield strength is 370 MPa in A versus 1,050 MPa in QT-38.
How much does 18NCD6 cost?
18NCD6 is a budget-cost steel ($), cheaper than about 90% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Sources
- NF A35-551 — Aciers de cementation (18NCD6) — AFNOR (1987)
- EN 10084 — Case hardening steels (18NiCrMo5 / 18CrNiMo7-6 family) — CEN (2008)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels and High-Performance Alloys — ASM International (1990)
- ASM Handbook Vol.4 — Heat Treating (carburizing) — ASM International (1991)
- Machinery's Handbook, 31st ed. — machinability ratings — Industrial Press (2020)
- GB/T 3077 — (20CrNi2Mo/20CrNiMo ) — SAC (2015)
Property data is compiled from published supplier and standards handbooks and normalised for comparison; hardness values on non-Brinell scales are converted approximately for charting only. Manufacturability limits are FabDigit quote-engine defaults and may be relaxed by engineering review. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.