Steel 34CrAlMo5-10 +QT-100 (+QT)
Heat-treated state · default condition
EN 34CrAlMo5-10
Standard stocked condition: oil/water quench from ~880 °C plus temper ~580–680 °C, ready for finish machining and nitriding.
Values for the +QT-100 condition
Other 34CrAlMo5-10 tempers and conditions
34CrAlMo5-10 is listed in 7 conditions; see the grade overview at 34CrAlMo5-10.
Compare all 7 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Annealed | Delivery condition for bar/forging stock that will be rough machined then quenched, tempered and nitrided. | 450 | 720 | 20 | 220 HB | — |
Normalized | Grain-refining condition for forgings before the final quench-and-temper cycle; rarely a final state. | 550 | 850 | 16 | 25 HRC | 8 % IACS |
annealed and cold drawn bar | Bright cold-drawn bar for small shafts and pins where tight tolerance stock is machined then nitrided. | 600 | 800 | 12 | 22 HRC | 8 % IACS |
+QT | Large forgings and thick screw/barrel blanks; lowest guaranteed strength class of the grade. | 620 | 800 | 16 | 24 HRC | 8 % IACS |
+QT | Same heat treatment on heavier bar/forging where mass effect lowers guaranteed strength. | 670 | 850 | 15 | 27 HRC | 8 % IACS |
+QT-100DefaultThis page +QT | Standard stocked condition: oil/water quench from ~880 °C plus temper ~580–680 °C, ready for finish machining and nitriding. | 720 | 900 | 14 | 29 HRC | — |
+QT + gas/plasma nitrided | Final in-service condition: Q&T core with a 0.2–0.6 mm nitrided case for wear, scuffing and fatigue resistance. | 720 | 900 | 12 | 68 HRC | — |
What is 34CrAlMo5-10 +QT-100?
34CrAlMo5-10 +QT-100 is 34CrAlMo5-10 heat treated to +QT-100 — standard stocked condition: oil/water quench from ~880 °C plus temper ~580–680 °C, ready for finish machining and nitriding. 34CrAlMo5-10 +QT-100 has a yield strength of 720 MPa (104 ksi) and a tensile strength of 900 MPa (131 ksi) — stronger than 82% of steel grades. Elongation at break is 14% and the elastic modulus is 210 GPa (30.5 Msi). 34CrAlMo5-10 +QT-100 has a density of 7.8 g/cm³ (0.282 lb/in³), lighter than 87% of steel grades. It melts at 1,420°C (2,588 °F).
Advantages
- High service temperature — 500°C (932 °F), better than 90% of steel grades
- High strength — 720 MPa (104 ksi), better than 82% of steel grades
- Polishes to a fine finish — 65/100, better than 78% of steel grades
Limitations
- Difficult to weld — 20/100, worse than 84% of steel grades
- Poor heat conductor — 34 W/m·K (19.6 BTU/hr·ft·°F), worse than 77% of steel grades
- Limited ductility — 14%, worse than 75% of steel grades
34CrAlMo5-10 +QT-100 properties
Typical room-temperature values for 34CrAlMo5-10 +QT-100; 13 are specific to this condition. Other listed values are 34CrAlMo5-10 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
34CrAlMo5-10 +QT-100 has a density of 7.8 g/cm³ (0.282 lb/in³), lighter than 87% of steel grades. It melts at 1,420°C (2,588 °F).
Mechanical16
34CrAlMo5-10 +QT-100 has a yield strength of 720 MPa (104 ksi) and a tensile strength of 900 MPa (131 ksi) — stronger than 82% of steel grades. Elongation at break is 14% and the elastic modulus is 210 GPa (30.5 Msi).
Thermal6
34CrAlMo5-10 +QT-100 is rated for continuous service to 500°C (932 °F). It conducts heat at 34 W/m·K (19.6 BTU/hr·ft·°F), worse than 77% of steel grades. Thermal expansion is 12.3 µm/m·K (6.83 µin/in·°F).
Electrical3
34CrAlMo5-10 +QT-100 conducts electricity at 8 % IACS, better than 55% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of 34CrAlMo5-10 +QT-100 takes about 31 MJ of energy and emits 2.2 kg of CO₂ — more than 64% of steel grades. Typical recycled content is 30%.
Manufacturability6
34CrAlMo5-10 +QT-100's machinability is fair (45/100, worse than 65% of steel grades); weldability poor (20/100); formability poor (25/100).
Common Calculations5
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 34CrAlMo5-10 +QT-100
Is 34CrAlMo5-10 easy to machine?
Machine in the +A or +QT condition with carbide tooling and rigid setups; leave 0.05–0.15 mm grinding stock and stress-relieve at ~550 °C before nitriding to control distortion.
Can 34CrAlMo5-10 be welded?
Welding is not recommended — high Al and Cr promote hard, crack-sensitive HAZ; if unavoidable, preheat 300–350 °C, use matching or austenitic filler and temper immediately.
Can 34CrAlMo5-10 be formed, bent or molded?
Hot forge 1100→850 °C with slow furnace cooling then anneal; cold forming is limited to light straightening of annealed bar.
What surface finishes work on 34CrAlMo5-10?
Gas or plasma nitride 500–530 °C for a 0.2–0.6 mm case at ≥800 HV1; grind/lap lightly afterwards, and protect the uncoated steel with oil, phosphate or black oxide since it is not corrosion resistant.
34CrAlMo5-10 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 – 0.37 | 0.34 |
| Si | ≤ 0.4 | 0.25 |
| Mn | 0.5 – 0.8 | 0.65 |
| P | ≤ 0.03 | — |
| Smax; low-S variants for cleanliness | ≤ 0.04 | — |
| Cr | 1 – 1.3 | 1.15 |
| Mo | 0.15 – 0.25 | 0.2 |
| Alforms hard AlN in the nitrided case | 0.8 – 1.2 | 1 |
| Fe | balance | — |
34CrAlMo5-10 +QT-100 — frequently asked
What is 34CrAlMo5-10 +QT-100 used for?
34CrAlMo5-10 +QT-100 is typically used for gears, camshafts, wear-resistant bushings and extruder screws. In short: highest nitrided case hardness; EN 10085 nitriding standard; not weldable in practice.
What is the yield strength of 34CrAlMo5-10 +QT-100?
34CrAlMo5-10 +QT-100 has a typical yield strength of 720 MPa (104 ksi) and a tensile strength of 900 MPa (131 ksi) — stronger than 82% of steel grades. Strength varies by condition: see the 7 listed tempers.
Is 34CrAlMo5-10 +QT-100 easy to machine?
Reasonably — machinability is rated fair (45/100, worse than 65% of steel grades). Machine in the +A or +QT condition with carbide tooling and rigid setups; leave 0.05–0.15 mm grinding stock and stress-relieve at ~550 °C before nitriding to control distortion.
Can 34CrAlMo5-10 +QT-100 be welded?
Not readily — weldability is rated poor (20/100). Welding is not recommended — high Al and Cr promote hard, crack-sensitive HAZ; if unavoidable, preheat 300–350 °C, use matching or austenitic filler and temper immediately.
What surface finishes work on 34CrAlMo5-10 +QT-100?
Gas or plasma nitride 500–530 °C for a 0.2–0.6 mm case at ≥800 HV1; grind/lap lightly afterwards, and protect the uncoated steel with oil, phosphate or black oxide since it is not corrosion resistant.
Can 34CrAlMo5-10 +QT-100 be formed, bent or molded?
Hot forge 1100→850 °C with slow furnace cooling then anneal; cold forming is limited to light straightening of annealed bar.
What is the maximum service temperature of 34CrAlMo5-10 +QT-100?
34CrAlMo5-10 +QT-100 is rated for continuous use to about 500°C (932 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
Sources
- EN 10085 — Nitriding steels: technical delivery conditions — CEN (2001)
- DIN 17211 / material no. 1.8507 (superseded) — DIN (1987)
- BS 970 En40B — BSI (1991)
- GB/T 3077 — 38CrMoAl (near-equivalent) — SAC (2015)
- ASM Handbook Vol.4 — Heat Treating (Nitriding) — ASM International (1991)
- Nitriding steel 1.8507 bar datasheet — European special steel producers (2022)
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.