Steel 31CrMoV9 +N (Normalized)
Heat-treated state
EN 31CrMoV9
Intermediate mill condition for homogenising forgings and bar before final hardening; rarely a service condition.
Values for the +N condition
Other 31CrMoV9 tempers and conditions
31CrMoV9 is listed in 7 conditions; see the grade overview at 31CrMoV9.
Compare all 7 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Annealed | Pick for rough machining, deep hole drilling or forming before the final quench-and-temper cycle. | 550 | 800 | 16 | 230 HB | — |
+NThis page Normalized | Intermediate mill condition for homogenising forgings and bar before final hardening; rarely a service condition. | 650 | 950 | 13 | 29 HRC | 7.8 % IACS |
+QT | Heavy forged sections for large screws/barrels where 800–1000 MPa core strength is sufficient. | 680 | 900 | 14 | 27 HRC | 7.8 % IACS |
+QT | Typical shaft/gear-blank section; slightly lower core strength due to reduced quench severity. | 780 | 1,000 | 13 | 31 HRC | 7.8 % IACS |
Q&TDefault Quenched and tempered | Standard stocked condition: oil/polymer quenched and tempered ~600–680 °C, ready for finish machining and subsequent nitriding. | 880 | 1,100 | 12 | 34 HRC | — |
gas/plasma nitrided surface (≥800 HV) | Final service condition for gears, spindles and extruder screws: hard, wear- and scuff-resistant case on a tough Q&T core with minimal distortion. | 880 | 1,100 | 11 | 65 HRC | — |
+QT | Small-diameter bar fully hardened through section — highest core strength available in this grade. | 950 | 1,150 | 10 | 38 HRC | 7.8 % IACS |
What is 31CrMoV9 +N?
31CrMoV9 +N is 31CrMoV9 heat treated to +N — intermediate mill condition for homogenising forgings and bar before final hardening; rarely a service condition. 31CrMoV9 +N has a yield strength of 650 MPa (94.3 ksi) and a tensile strength of 950 MPa (138 ksi) — stronger than 79% of steel grades. Elongation at break is 13% and the elastic modulus is 210 GPa (30.5 Msi). 31CrMoV9 +N 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). Q&T is the default condition FabDigit quotes; +N is available on request or by drawing note.
Advantages
- Polishes to a fine finish — 70/100, better than 87% of steel grades
- High strength — 650 MPa (94.3 ksi), better than 79% of steel grades
Limitations
- Difficult to weld — 22/100, worse than 81% of steel grades
- Limited ductility — 13%, worse than 78% of steel grades
- Low fracture toughness — 60 MPa·√m (54.6 ksi·√in), worse than 78% of steel grades
31CrMoV9 +N properties
Typical room-temperature values for 31CrMoV9 +N; 22 are specific to this condition. Other listed values are 31CrMoV9 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
31CrMoV9 +N 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
31CrMoV9 +N has a yield strength of 650 MPa (94.3 ksi) and a tensile strength of 950 MPa (138 ksi) — stronger than 79% of steel grades. Elongation at break is 13% and the elastic modulus is 210 GPa (30.5 Msi).
Thermal6
31CrMoV9 +N is rated for continuous service to 420°C (788 °F). It conducts heat at 38 W/m·K (22 BTU/hr·ft·°F), worse than 69% of steel grades. Thermal expansion is 11.8 µm/m·K (6.56 µin/in·°F).
Electrical2
31CrMoV9 +N has an electrical resistivity of 2.2×10⁻⁷ Ω·m.
Chemical & Environmental2
Corrosion resistance is poor (16/100), better than 79% of steel grades.
Sustainability4
Producing a kilogram of 31CrMoV9 +N takes about 30 MJ of energy and emits 2.3 kg of CO₂ — more than 56% of steel grades. Typical recycled content is 25%.
Manufacturability8
31CrMoV9 +N's machinability is fair (44/100, worse than 71% of steel grades); weldability poor (22/100); formability poor (25/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 31CrMoV9 +N
Is 31CrMoV9 easy to machine?
Finish machine in the Q&T state with coated carbide, ~80–140 m/min and rigid setups; leave 0.02–0.05 mm for post-nitride lapping/grinding since the nitrided case is essentially unmachinable.
Can 31CrMoV9 be welded?
Poor weldability — 0.3 %C with 2.5 %Cr; if unavoidable, preheat 300–350 °C, use matching low-hydrogen or austenitic filler and temper immediately after welding; never weld nitrided surfaces.
Can 31CrMoV9 be formed, bent or molded?
Hot forge 1050–850 °C with slow cooling, then soft anneal ~680–710 °C; cold forming is impractical above the annealed condition.
What surface finishes work on 31CrMoV9?
Gas or plasma nitride 500–530 °C for 0.25–0.6 mm case (≥800 HV); alternatives are oxide-black, phosphating, hard chrome or QPQ — no anodizing.
31CrMoV9 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 | 0.27 – 0.34 | 0.31 |
| Si | ≤ 0.4 | 0.25 |
| Mn | 0.4 – 0.7 | 0.55 |
| P | ≤ 0.03 | — |
| Smax; lower S for higher toughness/ESR grades | ≤ 0.04 | — |
| Cr | 2.3 – 2.7 | 2.5 |
| Mo | 0.15 – 0.25 | 0.2 |
| V | 0.1 – 0.2 | 0.15 |
| Fe | balance | — |
31CrMoV9 +N — frequently asked
What is 31CrMoV9 +N used for?
31CrMoV9 +N is typically used for nitrided industrial shafts, gear surfaces, extruder screws and barrels, hydraulic piston rods, machine tool spindles and cam and control shafts. In short: high-strength Q&T bar.
What is the yield strength of 31CrMoV9 +N?
31CrMoV9 +N has a typical yield strength of 650 MPa (94.3 ksi) and a tensile strength of 950 MPa (138 ksi) — stronger than 79% of steel grades. Strength varies by condition: see the 7 listed tempers.
Is 31CrMoV9 +N easy to machine?
Not especially — machinability is rated fair (44/100, worse than 71% of steel grades). Finish machine in the Q&T state with coated carbide, ~80–140 m/min and rigid setups; leave 0.02–0.05 mm for post-nitride lapping/grinding since the nitrided case is essentially unmachinable.
Can 31CrMoV9 +N be welded?
Not readily — weldability is rated poor (22/100). Poor weldability — 0.3 %C with 2.5 %Cr; if unavoidable, preheat 300–350 °C, use matching low-hydrogen or austenitic filler and temper immediately after welding; never weld nitrided surfaces.
What surface finishes work on 31CrMoV9 +N?
Gas or plasma nitride 500–530 °C for 0.25–0.6 mm case (≥800 HV); alternatives are oxide-black, phosphating, hard chrome or QPQ — no anodizing.
Can 31CrMoV9 +N be formed, bent or molded?
Hot forge 1050–850 °C with slow cooling, then soft anneal ~680–710 °C; cold forming is impractical above the annealed condition.
What is the maximum service temperature of 31CrMoV9 +N?
31CrMoV9 +N is rated for continuous use to about 420°C (788 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
Can FabDigit make parts in 31CrMoV9 +N?
Yes — 31CrMoV9 +N is available for CNC machining and sheet metal; every part is priced by an engineer rather than instantly. Upload a STEP file to get a price and a DFM check.
Sources
- EN 10085 — Nitriding steels: technical delivery conditions — CEN (2001)
- DIN 17211 (superseded) — Nitriding steels — DIN (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 (nitriding) — ASM International (2013)
- 31CrMoV9 / 1.8519 nitriding steel datasheet — Lucefin / Böhler / Dörrenberg (2021)
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.