Steel 31CrMoV9 · heat-treated state · default condition
Steel 31CrMoV9 Q&T
Properties of the Q&T condition, compared with the other 31CrMoV9 tempers.
Standard stocked condition: oil/polymer quenched and tempered ~600–680 °C, ready for finish machining and subsequent nitriding.
What is 31CrMoV9 Q&T?
31CrMoV9 Q&T is 31CrMoV9 heat treated to Q&T — standard stocked condition: oil/polymer quenched and tempered ~600–680 °C, ready for finish machining and subsequent nitriding. 31CrMoV9 Q&T has a yield strength of 880 MPa (128 ksi) and a tensile strength of 1,100 MPa (160 ksi) — stronger than 90% of steel grades. Elongation at break is 12% and the elastic modulus is 210 GPa (30.5 Msi). 31CrMoV9 Q&T 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
- High strength — 880 MPa (128 ksi), better than 90% of steel grades
- Polishes to a fine finish — 70/100, better than 87% of steel grades
- High service temperature — 450°C (842 °F), better than 86% of steel grades
Limitations
- Limited ductility — 12%, worse than 84% of steel grades
- Difficult to weld — 20/100, worse than 84% of steel grades
- Limited formability — 20/100, worse than 80% of steel grades
- Difficult to machine — 40/100, worse than 76% of steel grades
31CrMoV9 Q&T properties
Typical room-temperature values for 31CrMoV9 Q&T — 13 properties are specific to this condition; the rest are grade-level values shared by every 31CrMoV9 temper. Each bar shows where the value sits among the steel grades in FabDigit's library — further right is higher.
Physical3
31CrMoV9 Q&T 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 Q&T has a yield strength of 880 MPa (128 ksi) and a tensile strength of 1,100 MPa (160 ksi) — stronger than 90% of steel grades. Elongation at break is 12% and the elastic modulus is 210 GPa (30.5 Msi).
Thermal6
31CrMoV9 Q&T is rated for continuous service to 450°C (842 °F). It conducts heat at 36 W/m·K (20.8 BTU/hr·ft·°F), worse than 72% of steel grades. Thermal expansion is 11.8 µm/m·K (6.56 µin/in·°F).
Electrical2
31CrMoV9 Q&T 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 Q&T takes about 30 MJ of energy and emits 2.3 kg of CO₂ — more than 55% of steel grades. Typical recycled content is 25%.
Manufacturability8
31CrMoV9 Q&T's machinability is fair (40/100, worse than 76% of steel grades); weldability poor (20/100); formability poor (20/100).
Common Calculations5
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Other 31CrMoV9 tempers and conditions
31CrMoV9 is also supplied in 7 other conditions. The full side-by-side table is on the 31CrMoV9 overview.
- Q&TDefaultStandard stocked condition: oil/polymer quenched and tempered ~600–680 °C, ready for finish machining and subsequent nitriding.880 MPa yield · 34 HRC
- Q&T d<=16Small-diameter bar fully hardened through section — highest core strength available in this grade.950 MPa yield · 38 HRC
- Q&T+NitridedFinal service condition for gears, spindles and extruder screws: hard, wear- and scuff-resistant case on a tough Q&T core with minimal distortion.880 MPa yield · 65 HRC
- Q&T 40-100Typical shaft/gear-blank section; slightly lower core strength due to reduced quench severity.780 MPa yield · 31 HRC
- Q&T 100-160Heavy forged sections for large screws/barrels where 800–1000 MPa core strength is sufficient.680 MPa yield · 27 HRC
- +APick for rough machining, deep hole drilling or forming before the final quench-and-temper cycle.550 MPa yield · 230 HB
Working with 31CrMoV9 Q&T
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 Q&T — frequently asked
What is 31CrMoV9 Q&T used for?
31CrMoV9 Q&T 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 Q&T?
31CrMoV9 Q&T has a typical yield strength of 880 MPa (128 ksi) and a tensile strength of 1,100 MPa (160 ksi) — stronger than 90% of steel grades. Strength varies by condition: see the 8 listed tempers.
Is 31CrMoV9 Q&T easy to machine?
Not especially — machinability is rated fair (40/100, worse than 76% 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 Q&T be welded?
Not readily — weldability is rated poor (20/100). 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 Q&T?
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 Q&T 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 Q&T?
31CrMoV9 Q&T is rated for continuous use to about 450°C (842 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
Can FabDigit make parts in 31CrMoV9 Q&T?
Yes — 31CrMoV9 Q&T 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 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.