Steel 42CrMo5-6 +QT (Quenched and tempered)
Heat-treated state · default condition
EN 42CrMo5-6
Standard supply condition for shafts, gears and rods needing ~1000–1200 MPa with good toughness.
Values for the +QT condition
Other 42CrMo5-6 tempers and conditions
42CrMo5-6 is listed in 10 conditions; see the grade overview at 42CrMo5-6.
Compare all 10 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Annealed | Pick for heavy machining, cold forming or before a customer-side hardening cycle; lowest hardness supply state. | 440 | 700 | 20 | 215 HB | 44 W/m·K |
Ferrite-pearlite structure, hardness range specified | Ordered when a narrow, reproducible pre-machining hardness band is needed for automatic machining lines. | 470 | 760 | 18 | 17 HRC | 8.2 % IACS |
Treated for high shearability | Bar delivered with a capped hardness so slugs can be cold-sheared cleanly for forging or upsetting. | 490 | 780 | 17 | 20 HRC | 7.8 % IACS |
Normalized | Use to refine grain and homogenize forgings before final machining or quench-and-temper. | 520 | 820 | 16 | 22 HRC | 7.8 % IACS |
Hot rolled | Cheapest supply state when the buyer will re-heat-treat the part anyway; properties are not guaranteed. | 560 | 880 | 14 | 25 HRC | 7.8 % IACS |
Cold drawn | Bright bar with close tolerance and a straight, work-hardened surface for shafting and short-run machining. | 720 | 880 | 10 | 24 HRC | 7.8 % IACS |
tempered to a medium hardness band | Common ordering band for large shafts, flanges and pressure parts where toughness and machinability outrank hardness. | 800 | 980 | 15 | 30 HRC | — |
+QTDefaultThis page Quenched and tempered | Standard supply condition for shafts, gears and rods needing ~1000–1200 MPa with good toughness. | 850 | 1,050 | 13 | 34 HRC | — |
tempered to a higher hardness band | Chosen for gears, spindles and hydraulic rods where wear and fatigue strength matter more than machining ease. | 950 | 1,120 | 12 | 34 HRC | — |
low-temperature tempered, high strength | For small sections, tooling and high-strength fasteners; toughness and hydrogen-embrittlement margin drop sharply. | 1,250 | 1,400 | 9 | 43 HRC | — |
What is 42CrMo5-6 +QT?
42CrMo5-6 +QT is 42CrMo5-6 heat treated to +QT — standard supply condition for shafts, gears and rods needing ~1000–1200 MPa with good toughness. 42CrMo5-6 +QT has a yield strength of 850 MPa (123 ksi) and a tensile strength of 1,050 MPa (152 ksi) — stronger than 88% of steel grades. Elongation at break is 13% and the elastic modulus is 210 GPa (30.5 Msi). 42CrMo5-6 +QT 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
- Low embodied carbon — 1.9 kg CO₂/kg, better than 92% of steel grades
- High strength — 850 MPa (123 ksi), better than 88% of steel grades
- Polishes to a fine finish — 65/100, better than 78% of steel grades
Limitations
- Limited formability — 20/100, worse than 80% of steel grades
- Limited ductility — 13%, worse than 78% of steel grades
42CrMo5-6 +QT properties
Typical room-temperature values for 42CrMo5-6 +QT; 16 are specific to this condition. Other listed values are 42CrMo5-6 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
42CrMo5-6 +QT 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
42CrMo5-6 +QT has a yield strength of 850 MPa (123 ksi) and a tensile strength of 1,050 MPa (152 ksi) — stronger than 88% of steel grades. Elongation at break is 13% and the elastic modulus is 210 GPa (30.5 Msi).
Thermal6
42CrMo5-6 +QT 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
42CrMo5-6 +QT conducts electricity at 7.8 % IACS, worse than 57% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of 42CrMo5-6 +QT takes about 25 MJ of energy and emits 1.9 kg of CO₂ — less than 82% of steel grades. Typical recycled content is 30%.
Manufacturability7
42CrMo5-6 +QT's machinability is fair (45/100, worse than 65% of steel grades); weldability fair (35/100); formability poor (20/100).
Common Calculations5
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 42CrMo5-6 +QT
Is 42CrMo5-6 easy to machine?
Machine in the annealed or 28–32 HRC condition with rigid setups, coated carbide and generous coolant; above 36 HRC expect ceramic/CBN finishing and heavy tool wear.
Can 42CrMo5-6 be welded?
Weldable only with 150–300 °C preheat, low-hydrogen consumables and a 600–650 °C post-weld temper; avoid welding fully hardened sections.
Can 42CrMo5-6 be formed, bent or molded?
Hot forge at 1050–1200 °C with slow cooling to avoid quench cracks; cold forming is limited to the +A/+S conditions.
What surface finishes work on 42CrMo5-6?
No anodizing — use black oxide, phosphate, zinc or Ni plating (bake for hydrogen relief), hard chrome for rods, or gas/plasma nitriding for 600–700 HV surfaces.
42CrMo5-6 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 |
|---|---|---|
| C0.42 % nominal, basis of the grade name | 0.38 – 0.45 | 0.42 |
| Si | ≤ 0.4 | 0.25 |
| Mn | 0.6 – 0.9 | 0.75 |
| P | ≤ 0.03 | 0.02 |
| Sresulphurized (+S-type) variants run 0.020–0.040 for machinability | ≤ 0.04 | 0.02 |
| Crricher than 42CrMo4 for hardenability | 1.1 – 1.4 | 1.25 |
| Moraises temper resistance and cuts temper embrittlement | 0.5 – 0.7 | 0.6 |
| Niresidual | ≤ 0.4 | — |
| Fe | balance | — |
42CrMo5-6 +QT — frequently asked
What is 42CrMo5-6 +QT used for?
42CrMo5-6 +QT is typically used for shafts, gears, connecting rods, high-strength fasteners and machine tool components. In short: controlled-chemistry 42CrMo grade; supplied in defined QT bands; nitrides to 600–700 HV.
What is the yield strength of 42CrMo5-6 +QT?
42CrMo5-6 +QT has a typical yield strength of 850 MPa (123 ksi) and a tensile strength of 1,050 MPa (152 ksi) — stronger than 88% of steel grades. Strength varies by condition: see the 10 listed tempers.
Is 42CrMo5-6 +QT easy to machine?
Reasonably — machinability is rated fair (45/100, worse than 65% of steel grades). Machine in the annealed or 28–32 HRC condition with rigid setups, coated carbide and generous coolant; above 36 HRC expect ceramic/CBN finishing and heavy tool wear.
Can 42CrMo5-6 +QT be welded?
With care — weldability is rated fair (35/100). Weldable only with 150–300 °C preheat, low-hydrogen consumables and a 600–650 °C post-weld temper; avoid welding fully hardened sections.
What surface finishes work on 42CrMo5-6 +QT?
No anodizing — use black oxide, phosphate, zinc or Ni plating (bake for hydrogen relief), hard chrome for rods, or gas/plasma nitriding for 600–700 HV surfaces.
Can 42CrMo5-6 +QT be formed, bent or molded?
Hot forge at 1050–1200 °C with slow cooling to avoid quench cracks; cold forming is limited to the +A/+S conditions.
What is the maximum service temperature of 42CrMo5-6 +QT?
42CrMo5-6 +QT 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.
Sources
- EN 10083-3 Steels for quenching and tempering — Alloy steels — CEN (2006)
- EN 10250-3 Open die steel forgings — Alloy special steels — CEN (1999)
- Stahlschlüssel / Key to Steel (W.-Nr. 1.7233) — Verlag Stahlschlüssel Wegst (2019)
- 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)
- GB/T 3077 (42CrMo) — SAC (2015)
- SAE J404 / ASTM A29 (4142 chemistry) — SAE / ASTM (2020)
- Mysteel / SMM (2025)
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.