Steel 100CrMo7 +AC (Spheroidize annealed)
Heat-treated state · default condition
EN 100CrMo7 · GB GCr18Mo
Standard stock condition for bar/tube that will be machined into bearing rings and then hardened.
Values for the +AC condition
Other 100CrMo7 tempers and conditions
100CrMo7 is listed in 8 conditions; see the grade overview at 100CrMo7.
Compare all 8 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Annealed | Use when only maximum softness for heavy hot/warm forming is needed and carbide morphology is not yet critical. | 400 | 680 | 22 | 14 HRC | 3.8 % IACS |
+ACDefaultThis page Spheroidize annealed | Standard stock condition for bar/tube that will be machined into bearing rings and then hardened. | 420 | 700 | 20 | 210 HB | 42 W/m·K |
Spheroidized, peeled/turned and ground bright bar | Use where decarburised skin must be removed and tight straightness/diameter are needed for roller or pin blanks. | 420 | 700 | 20 | 15 HRC | 3.8 % IACS |
Hot rolled | Mill-supplied uncooled condition for forging shops that will spheroidize in-house; too hard and variable for direct machining. | 600 | 1,000 | 10 | 31 HRC | 3.7 % IACS |
Spheroidize annealed and cold drawn bar | Choose for close-tolerance, bright-surface bar going straight to automatic-lathe machining of small rings, rollers and pins. | 620 | 820 | 10 | 245 HB | — |
Q&T tempered 230–250 °C | Pick for bearings running up to ~200 °C where dimensional stability outranks peak hardness. | 1,750 | 2,050 | 2 | 59 HRC | 35 W/m·K |
Bainite hardened | Choose for large railway, rolling-mill and wind-turbine bearings needing residual compressive stress, higher toughness and tolerance of contaminated lubrication. | 1,750 | 2,100 | 2 | 59 HRC | 35 W/m·K |
Q&T 60–64 HRC | Standard finished-bearing condition: maximum hardness, wear and rolling-contact fatigue life for service below ~150 °C. | 1,900 | 2,250 | 1 | 62 HRC | 34 W/m·K |
What is 100CrMo7 +AC?
100CrMo7 +AC is 100CrMo7 heat treated to +AC — standard stock condition for bar/tube that will be machined into bearing rings and then hardened. 100CrMo7 +AC has a yield strength of 420 MPa (60.9 ksi) and a tensile strength of 700 MPa (102 ksi) — weaker than 53% of steel grades. Elongation at break is 20% and the elastic modulus is 210 GPa (30.5 Msi). 100CrMo7 +AC has a density of 7.83 g/cm³ (0.283 lb/in³), lighter than 80% of steel grades. It melts at 1,420°C (2,588 °F).
Advantages
- Polishes to a fine finish — 80/100, better than 97% of steel grades
Limitations
- Difficult to weld — 12/100, worse than 96% of steel grades
- Limited service temperature — 200°C (392 °F), worse than 93% of steel grades
- Low electrical conductivity — 3.8 % IACS, worse than 84% of steel grades
100CrMo7 +AC properties
Typical room-temperature values for 100CrMo7 +AC; 17 are specific to this condition. Other listed values are 100CrMo7 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
100CrMo7 +AC has a density of 7.83 g/cm³ (0.283 lb/in³), lighter than 80% of steel grades. It melts at 1,420°C (2,588 °F).
Mechanical15
100CrMo7 +AC has a yield strength of 420 MPa (60.9 ksi) and a tensile strength of 700 MPa (102 ksi) — weaker than 53% of steel grades. Elongation at break is 20% and the elastic modulus is 210 GPa (30.5 Msi).
Thermal6
100CrMo7 +AC is rated for continuous service to 200°C (392 °F). It conducts heat at 42 W/m·K (24.3 BTU/hr·ft·°F), worse than 56% of steel grades. Thermal expansion is 11.9 µm/m·K (6.61 µin/in·°F).
Electrical3
100CrMo7 +AC conducts electricity at 3.8 % IACS, worse than 84% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (13/100), better than 66% of steel grades.
Sustainability4
Producing a kilogram of 100CrMo7 +AC takes about 32 MJ of energy and emits 2.3 kg of CO₂ — more than 70% of steel grades. Typical recycled content is 25%.
Manufacturability8
100CrMo7 +AC's machinability is fair (45/100, worse than 65% of steel grades); weldability not recommended (12/100); 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 100CrMo7 +AC
Is 100CrMo7 easy to machine?
Machine only in the spheroidized condition (~210 HB) with sharp coated carbide and rigid setups; after hardening to 60+ HRC use CBN turning or grinding.
Can 100CrMo7 be welded?
Effectively non-weldable at ~1 %C — cracks readily; if unavoidable, preheat 300–400 °C, use low-hydrogen filler and immediately re-anneal.
Can 100CrMo7 be formed, bent or molded?
Cold ring-rolling and cold forging are possible only after full spheroidizing; hot forge 1050–1150 °C and cool slowly to avoid flake/quench cracks.
What surface finishes work on 100CrMo7?
Bearing surfaces are hard-turned, ground and honed/lapped; corrosion protection by oil, phosphating, black oxide or thin dense chrome — no anodising.
100CrMo7 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 | 0.93 – 1.05 | 0.99 |
| Si | 0.2 – 0.4 | 0.3 |
| Mn | 0.25 – 0.4 | 0.33 |
| P | ≤ 0.03 | — |
| S | ≤ 0.02 | — |
| Cr | 1.65 – 1.95 | 1.8 |
| Mo | 0.15 – 0.3 | 0.22 |
| Niresidual, max | ≤ 0.3 | — |
| Curesidual, max | ≤ 0.3 | — |
| Alresidual, max | ≤ 0.05 | — |
| O≤15 ppm typical for bearing quality | ≤ 0 | — |
| Fe | balance | — |
100CrMo7 +AC — frequently asked
What is 100CrMo7 +AC used for?
100CrMo7 +AC is typically used for large ball and roller bearings, bearing rings and rollers for heavy machinery and wind turbine and industrial gearbox bearings. In short: deeper-hardening 100Cr6 upgrade; large-section bearing steel; hardens above 60 HRC.
What is the yield strength of 100CrMo7 +AC?
100CrMo7 +AC has a typical yield strength of 420 MPa (60.9 ksi) and a tensile strength of 700 MPa (102 ksi) — weaker than 53% of steel grades. Strength varies by condition: see the 8 listed tempers.
Is 100CrMo7 +AC easy to machine?
Reasonably — machinability is rated fair (45/100, worse than 65% of steel grades). Machine only in the spheroidized condition (~210 HB) with sharp coated carbide and rigid setups; after hardening to 60+ HRC use CBN turning or grinding.
Can 100CrMo7 +AC be welded?
Not readily — weldability is rated not recommended (12/100). Effectively non-weldable at ~1 %C — cracks readily; if unavoidable, preheat 300–400 °C, use low-hydrogen filler and immediately re-anneal.
What surface finishes work on 100CrMo7 +AC?
Bearing surfaces are hard-turned, ground and honed/lapped; corrosion protection by oil, phosphating, black oxide or thin dense chrome — no anodising.
Can 100CrMo7 +AC be formed, bent or molded?
Cold ring-rolling and cold forging are possible only after full spheroidizing; hot forge 1050–1150 °C and cool slowly to avoid flake/quench cracks.
What is the maximum service temperature of 100CrMo7 +AC?
100CrMo7 +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.
What is the difference between 100CrMo7 +AC and 100CrMo7 QT-250C?
+AC is the default condition — standard stock condition for bar/tube that will be machined into bearing rings and then hardened. QT-250C: pick for bearings running up to ~200 °C where dimensional stability outranks peak hardness. Yield strength is 420 MPa in +AC versus 1,750 MPa in QT-250C.
Sources
- EN ISO 683-17 Heat-treatable steels — Ball and roller bearing steels — ISO/CEN (2014)
- GB/T 18254 (GCr18Mo) — SAC (2016)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels and High-Performance Alloys — ASM International (1990)
- Bearing steel grade datasheets (100Cr6 / 100CrMo7 / 100CrMo7-3) — Ovako / Sandvik / Böhler (2022)
- ASM Handbook Vol.19 — Fatigue and Fracture — ASM International (1996)
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.