Steel 18NiCrMo14-6 +AC (Spheroidize annealed)
Heat-treated state · default condition
EN 18NiCrMo14-6
Standard stock condition for bar and forging billet: spheroidized carbides give the best machinability and dimensional stability before carburizing.
Values for the +AC condition
Other 18NiCrMo14-6 tempers and conditions
18NiCrMo14-6 is listed in 7 conditions; see the grade overview at 18NiCrMo14-6.
Compare all 7 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Treated for high shearability | Choose for coil, wire and bar that must be cold sheared, sawn or cold headed into blanks without cracking; softest supplied condition. | 450 | 680 | 19 | 200 HB | — |
Annealed | General annealed delivery condition for forging and rough machining where a specified spheroidized structure is not required. | 480 | 720 | 17 | 16 HRC | 7 % IACS |
+ACDefaultThis page Spheroidize annealed | Standard stock condition for bar and forging billet: spheroidized carbides give the best machinability and dimensional stability before carburizing. | 500 | 750 | 16 | 220 HB | — |
Treated to a specified hardness range | Pick for automated turning/hobbing lines that need a narrow, repeatable hardness window before carburizing. | 580 | 850 | 14 | 25 HRC | 7 % IACS |
Hot rolled | Cheapest mill condition for stock that will be re-forged and fully heat treated by the user. | 650 | 950 | 12 | 30 HRC | 7 % IACS |
Supplied to specified hardenability (Jominy) band, carburize-and-harden… | Order +H when the deep case and through-hardened tough core must be guaranteed by end-quench band on large bearing rings and gears. | 1,050 | 1,350 | 11 | 41 HRC | — |
Carburized, hardened and low-temperature tempered | Final in-service condition: 58–62 HRC deep case over a tough 36–45 HRC martensitic core for high-load rolling contact and bending fatigue. | 1,100 | 1,400 | 10 | 60 HRC | — |
What is 18NiCrMo14-6 +AC?
18NiCrMo14-6 +AC is 18NiCrMo14-6 heat treated to +AC — standard stock condition for bar and forging billet: spheroidized carbides give the best machinability and dimensional stability before carburizing. 18NiCrMo14-6 +AC has a yield strength of 500 MPa (72.5 ksi) and a tensile strength of 750 MPa (109 ksi) — stronger than 63% of steel grades. Elongation at break is 16% and the elastic modulus is 210 GPa (30.5 Msi). 18NiCrMo14-6 +AC 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).
Advantages
- Polishes to a fine finish — 75/100, better than 94% of steel grades
Limitations
- Limited service temperature — 200°C (392 °F), worse than 93% of steel grades
- High embodied carbon — 2.5 kg CO₂/kg, worse than 82% of steel grades
- Poor heat conductor — 34 W/m·K (19.6 BTU/hr·ft·°F), worse than 77% of steel grades
- Difficult to weld — 25/100, worse than 77% of steel grades
18NiCrMo14-6 +AC properties
Typical room-temperature values for 18NiCrMo14-6 +AC; 13 are specific to this condition. Other listed values are 18NiCrMo14-6 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
18NiCrMo14-6 +AC 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).
Mechanical16
18NiCrMo14-6 +AC has a yield strength of 500 MPa (72.5 ksi) and a tensile strength of 750 MPa (109 ksi) — stronger than 63% of steel grades. Elongation at break is 16% and the elastic modulus is 210 GPa (30.5 Msi).
Thermal6
18NiCrMo14-6 +AC is rated for continuous service to 200°C (392 °F). It conducts heat at 34 W/m·K (19.6 BTU/hr·ft·°F), worse than 77% of steel grades. Thermal expansion is 11.5 µm/m·K (6.39 µin/in·°F).
Electrical3
18NiCrMo14-6 +AC conducts electricity at 7 % IACS, worse than 74% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of 18NiCrMo14-6 +AC takes about 34 MJ of energy and emits 2.5 kg of CO₂ — more than 82% of steel grades. Typical recycled content is 25%.
Manufacturability8
18NiCrMo14-6 +AC's machinability is fair (45/100, worse than 65% of steel grades); weldability poor (25/100); formability fair (45/100).
Common Calculations5
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 18NiCrMo14-6 +AC
Is 18NiCrMo14-6 easy to machine?
Machine in the +AC/+A condition with rigid setups, sharp coated carbide and generous coolant; the high-Ni matrix work-hardens and produces gummy chips, and finish grinding is normally required after carburizing.
Can 18NiCrMo14-6 be welded?
Not a structural welding grade — high carbon equivalent means preheat 250–350 °C, low-hydrogen consumables and immediate stress relief; never weld a carburized part.
Can 18NiCrMo14-6 be formed, bent or molded?
Hot forge 1100–1200 °C with slow cooling and full anneal afterwards; cold heading/shearing only in the +S condition, and severe cold forming is not practical.
What surface finishes work on 18NiCrMo14-6?
Case-harden (900–950 °C carburize, oil or high-pressure gas quench, deep-freeze plus 150–180 °C temper), then hard-turn/grind and superfinish; protect with oil film, manganese phosphate, black oxide or thin dense chrome — no anodizing.
18NiCrMo14-6 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 |
| Simax only | ≤ 0.4 | 0.25 |
| Mn | 0.4 – 0.7 | 0.55 |
| Pmax; bearing quality often ≤0.015 | ≤ 0.03 | 0.01 |
| Smax; low for cleanliness/fatigue | ≤ 0.02 | 0.01 |
| Cr | 1.15 – 1.45 | 1.3 |
| Mo | 0.2 – 0.3 | 0.25 |
| Ni | 3.2 – 3.6 | 3.4 |
| Curesidual max | ≤ 0.3 | — |
| Fe | balance | — |
18NiCrMo14-6 +AC — frequently asked
What is 18NiCrMo14-6 +AC used for?
18NiCrMo14-6 +AC is typically used for aerospace bearing rings, critical carburized gears, main-shaft bearing races, planetary gear pinions, heavily loaded gear and pinion shafts and motorsport transmission gears. In short: high core toughness; deep-hardening Ni-Cr-Mo case steel; aerospace bearing grade.
What is the yield strength of 18NiCrMo14-6 +AC?
18NiCrMo14-6 +AC has a typical yield strength of 500 MPa (72.5 ksi) and a tensile strength of 750 MPa (109 ksi) — stronger than 63% of steel grades. Strength varies by condition: see the 7 listed tempers.
Is 18NiCrMo14-6 +AC easy to machine?
Reasonably — machinability is rated fair (45/100, worse than 65% of steel grades). Machine in the +AC/+A condition with rigid setups, sharp coated carbide and generous coolant; the high-Ni matrix work-hardens and produces gummy chips, and finish grinding is normally required after carburizing.
Can 18NiCrMo14-6 +AC be welded?
Not readily — weldability is rated poor (25/100). Not a structural welding grade — high carbon equivalent means preheat 250–350 °C, low-hydrogen consumables and immediate stress relief; never weld a carburized part.
What surface finishes work on 18NiCrMo14-6 +AC?
Case-harden (900–950 °C carburize, oil or high-pressure gas quench, deep-freeze plus 150–180 °C temper), then hard-turn/grind and superfinish; protect with oil film, manganese phosphate, black oxide or thin dense chrome — no anodizing.
Can 18NiCrMo14-6 +AC be formed, bent or molded?
Hot forge 1100–1200 °C with slow cooling and full anneal afterwards; cold heading/shearing only in the +S condition, and severe cold forming is not practical.
What is the maximum service temperature of 18NiCrMo14-6 +AC?
18NiCrMo14-6 +AC 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.
Sources
- EN 10084 — Case hardening steels: technical delivery conditions — CEN (2008)
- ISO 683-17 — Heat-treatable steels, alloy steels and free-cutting steels, Part 17: Ball and roller bearing steels — ISO (2014)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels, and High-Performance Alloys — ASM International (1990)
- ASM Handbook Vol.4A/4D — Steel Heat Treating / Carburizing — ASM International (2014)
- Case-hardening bearing steel bar datasheets (Ovako / Ascometal / Böhler-type Ni-Cr-Mo carburizing grades) — European special steel producers (2022)
- (Mysteel / SMM / 1688 ) — Chinese steel market sources (2025)
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.