Steel 34CrNiMo6 · heat-treated state
Steel 34CrNiMo6-QT900
Properties of the QT900 condition, compared with the other 34CrNiMo6 tempers.
Higher-tempered condition for large sections or where maximum toughness/machinability is wanted.
What is 34CrNiMo6-QT900?
34CrNiMo6-QT900 is 34CrNiMo6 heat treated to QT900 — higher-tempered condition for large sections or where maximum toughness/machinability is wanted. 34CrNiMo6-QT900 has a yield strength of 760 MPa (110 ksi) and a tensile strength of 980 MPa (142 ksi) — stronger than 85% of steel grades. Elongation at break is 15% and the elastic modulus is 210 GPa (30.5 Msi). 34CrNiMo6-QT900 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). HR is the default condition FabDigit quotes; QT900 is available on request or by drawing note.
Advantages
- Polishes to a fine finish — 70/100, better than 87% of steel grades
- High strength — 760 MPa (110 ksi), better than 85% of steel grades
34CrNiMo6-QT900 properties
Typical room-temperature values for 34CrNiMo6-QT900 — 10 properties are specific to this condition; the rest are grade-level values shared by every 34CrNiMo6 temper. Each bar shows where the value sits among the steel grades in FabDigit's library — further right is higher.
Physical3
34CrNiMo6-QT900 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
34CrNiMo6-QT900 has a yield strength of 760 MPa (110 ksi) and a tensile strength of 980 MPa (142 ksi) — stronger than 85% of steel grades. Elongation at break is 15% and the elastic modulus is 210 GPa (30.5 Msi).
Thermal6
34CrNiMo6-QT900 is rated for continuous service to 400°C (752 °F). It conducts heat at 42 W/m·K (24.3 BTU/hr·ft·°F), worse than 56% of steel grades. Thermal expansion is 12.3 µm/m·K (6.83 µin/in·°F).
Electrical3
34CrNiMo6-QT900 conducts electricity at 7.5 % IACS, worse than 68% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of 34CrNiMo6-QT900 takes about 32 MJ of energy and emits 2.3 kg of CO₂ — more than 70% of steel grades. Typical recycled content is 30%.
Manufacturability7
34CrNiMo6-QT900's machinability is fair (45/100, worse than 65% of steel grades); weldability poor (30/100); formability poor (30/100).
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Other 34CrNiMo6 tempers and conditions
34CrNiMo6 is also supplied in 15 other conditions. The full side-by-side table is on the 34CrNiMo6 overview.
- HRDefaultMill as-rolled bar for re-forging or for parts that will be heat treated after machining.560 MPa yield · 26 HRC
- HardenedAustenitized ~850 °C and oil/polymer quenched to full martensite; maximum hardness but brittle — normally tempered before service.1,500 MPa yield · 54 HRC
- Q&T 36-40 HRCUpper hardness band for wear-loaded pins, spindles and tooling holders; machining becomes difficult.1,080 MPa yield · 38 HRC
- QT1200Maximum standard strength class; use only in thin sections and where notch sensitivity is controlled.1,060 MPa yield · 41 HRC
- QT1100High-strength class for smaller diameters — bolts, pins, connecting rods.970 MPa yield · 37 HRC
- Q&T 32-36 HRCTypical gear-blank and heavy-shaft hardness band; good balance of wear and impact resistance.950 MPa yield · 34 HRC
- Q&TStandard commercial supply condition: oil quench from ~850 °C and temper ~570–650 °C for balanced strength and toughness.870 MPa yield · 34 HRC
- QT1000Mid-range EN 10083-3 strength class for medium shafts, gears and couplings.870 MPa yield · 34 HRC
- NitridedChoose when a 0.2–0.5 mm wear- and fatigue-resistant case is needed without distortion from re-hardening.870 MPa yield · 34 HRC
- Q&T 28-32 HRCCommon purchase spec for shafting and API/oilfield parts needing good toughness and machinability.830 MPa yield · 30 HRC
- CRCold-rolled flat product with tight thickness tolerance and bright surface; limited availability in this grade.780 MPa yield · 30 HRC
- QT900Higher-tempered condition for large sections or where maximum toughness/machinability is wanted.760 MPa yield · 31 HRC
- CDBright, close-tolerance bar for shafting and turned parts machined without further heat treatment.720 MPa yield · 27 HRC
- NormalizedUniform fine-grain structure for forgings before final heat treatment or for moderately loaded parts.620 MPa yield · 29 HRC
- AnnealedSoftest supply condition — pick for deep machining, cold work or before final quench and temper.490 MPa yield · 18 HRC
- SpheroidizedSub-critical/cyclic anneal producing spheroidal carbides in ferrite — softest condition, best for cold forming, deep drilling and pre-machining.390 MPa yield · 190 HB
Working with 34CrNiMo6-QT900
Is 34CrNiMo6 easy to machine?
Machine in annealed (~215 HB) or Q&T ≤32 HRC condition with rigid setups, coated carbide, 80–140 m/min; above 36 HRC switch to CBN/ceramic or grinding.
Can 34CrNiMo6 be welded?
Weldable only with care: preheat 250–350 °C, low-hydrogen consumables, interpass control, and immediate post-weld temper 550–600 °C to avoid HAZ cracking.
Can 34CrNiMo6 be formed, bent or molded?
Hot forge 1100–850 °C then slow cool and normalize/anneal; cold forming limited to light straightening in the annealed condition.
What surface finishes work on 34CrNiMo6?
No anodizing — protect with oil, phosphate, black oxide, zinc-nickel or hard chrome; bake at 190–210 °C after plating to avoid hydrogen embrittlement; nitrides and polishes very well.
34CrNiMo6 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 | 0.3 – 0.38 | 0.34 |
| Si | ≤ 0.4 | 0.25 |
| Mn | 0.5 – 0.8 | 0.65 |
| P | ≤ 0.03 | 0.01 |
| S≤0.035 base grade; +S grade 0.020–0.040, low-S grade ≤0.005 | ≤ 0.04 | 0.02 |
| Cr | 1.3 – 1.7 | 1.5 |
| Mo | 0.15 – 0.3 | 0.22 |
| Ni | 1.3 – 1.7 | 1.5 |
| Fe | balance | — |
34CrNiMo6-QT900 — frequently asked
What is 34CrNiMo6-QT900 used for?
34CrNiMo6-QT900 is typically used for drive shafts, aerospace landing gear components, gears and pinions, crankshafts, high-strength bolts and studs and torsion bars. In short: premium Ni-Cr-Mo bar.
What is the yield strength of 34CrNiMo6-QT900?
34CrNiMo6-QT900 has a typical yield strength of 760 MPa (110 ksi) and a tensile strength of 980 MPa (142 ksi) — stronger than 85% of steel grades. Strength varies by condition: see the 16 listed tempers.
Is 34CrNiMo6-QT900 easy to machine?
Reasonably — machinability is rated fair (45/100, worse than 65% of steel grades). Machine in annealed (~215 HB) or Q&T ≤32 HRC condition with rigid setups, coated carbide, 80–140 m/min; above 36 HRC switch to CBN/ceramic or grinding.
Can 34CrNiMo6-QT900 be welded?
Not readily — weldability is rated poor (30/100). Weldable only with care: preheat 250–350 °C, low-hydrogen consumables, interpass control, and immediate post-weld temper 550–600 °C to avoid HAZ cracking.
What surface finishes work on 34CrNiMo6-QT900?
No anodizing — protect with oil, phosphate, black oxide, zinc-nickel or hard chrome; bake at 190–210 °C after plating to avoid hydrogen embrittlement; nitrides and polishes very well.
Can 34CrNiMo6-QT900 be formed, bent or molded?
Hot forge 1100–850 °C then slow cool and normalize/anneal; cold forming limited to light straightening in the annealed condition.
What is the maximum service temperature of 34CrNiMo6-QT900?
34CrNiMo6-QT900 is rated for continuous use to about 400°C (752 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between 34CrNiMo6-HR and 34CrNiMo6-QT1200?
HR is the default condition — mill as-rolled bar for re-forging or for parts that will be heat treated after machining. QT1200: maximum standard strength class; use only in thin sections and where notch sensitivity is controlled. Yield strength is 560 MPa in HR versus 1,060 MPa in QT1200.
Can FabDigit make parts in 34CrNiMo6-QT900?
Yes — 34CrNiMo6-QT900 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 10083-3 Steels for quenching and tempering — Part 3: Alloy steels — CEN (2006)
- EN 10250-3 Open die steel forgings — Alloy special steels — CEN (1999)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels and High-Performance Alloys — ASM International (1990)
- ASM Handbook Vol.19 — Fatigue and Fracture — ASM International (1996)
- Böhler V155 / 34CrNiMo6 datasheet — voestalpine BÖHLER Edelstahl (2022)
- Ovako 34CrNiMo6 (1.6582) steel data — Ovako (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.