Specifications
Surface Treatments
Certifications
- ISO 9001 - 2015 Certified
- PED 2014/68/EC
- NACE MR0175/ISO 15156-2
- NORSOK M-650
- DFAR
- MERKBLATT AD 2000 W2/W7/W10
21CrMoV5-7 Heat Treatment (Q+T Cycle) (EN 10269 / 1.7709)
The quenched-and-tempered (Q+T) cycle for 21CrMoV5-7 (Werkstoff 1.7709) is the controlling process for the mechanical-property floor and the secondary-hardening peak that drives the creep envelope. The cycle is austenitisation at 880 to 940 deg C, oil quench, and temper at 680 to 740 deg C with minimum 2-hour hold and air cool.
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Austenitisation
| Parameter | Value | Notes |
|---|---|---|
| Temperature | 880 to 940 deg C | Above Ac3 to fully transform ferrite to austenite |
| Hold time | 1 hour per 25 mm section | Allows carbide dissolution and homogenisation |
| Atmosphere | Neutral or protective | Avoid decarburisation |
Quench
| Quench medium | Use case | Cooling rate |
|---|---|---|
| Oil | Standard for all sections to OD 200 mm | ~30 deg C/s at the surface |
| Polymer quench | Reduced distortion on thin sections | ~20 deg C/s at the surface |
| Water (rare) | Only on thick sections where oil hardenability is marginal | ~60 deg C/s at the surface |
Temper
| Parameter | Value | Notes |
|---|---|---|
| Temperature | 680 to 740 deg C | Secondary-hardening peak; V4C3 precipitation |
| Hold time | Minimum 2 hours; 1 hour per 25 mm section | Allows V4C3 nucleation and growth |
| Cool | Air cool | Slow furnace cool also acceptable |
Temper Temperature Window
Below 660 deg C: V4C3 precipitation under-developed; long-term creep performance suffers; hardness too high above 250 HBW. Above 750 deg C: V4C3 over-coarsens and the carbide strengthening fades; room-temperature yield drops below the EN 10269 floor of 550 MPa.
Stress Relief After Machining
For heavily machined fastener blanks where dimensional stability matters, stress relief at 50 deg C below the final temper (typically 620 to 680 deg C) and slow furnace cool is recommended. The stress relief redistributes residual stresses without altering the temper microstructure.
PWHT for Welded Joints
Post-weld heat treatment at 690 to 720 deg C with hold time 1 hour per 25 mm joint thickness, minimum 2 hours, slow furnace cool to 300 deg C then air cool. The PWHT re-tempers the heat-affected zone and restores creep performance. Hardness traverse across weld plus HAZ plus parent verifies the PWHT achieved the intended tempering. See the welding page for the full procedure.
Frequently Asked Questions
Q. What is the standard Q+T cycle for 21CrMoV5-7?
Austenitise 880 to 940 deg C, hold 1 hour per 25 mm section, oil quench, temper 680 to 740 deg C minimum 2 hours, air cool. The cycle lands on the secondary-hardening peak driven by V4C3 carbide precipitation.
Q. Can I water-quench 21CrMoV5-7 instead of oil?
Generally no. Oil quench gives sufficient hardenability for all sections to OD 200 mm and avoids the quench-cracking risk that water introduces on Cr-Mo-V Q+T chemistry. Water quench only on call-out for thick sections above OD 200 mm where oil hardenability is marginal.
Q. Why is the temper window so tight?
The 680 to 740 deg C window lands on the secondary-hardening peak. Below 660 deg C the V4C3 precipitation is under-developed and creep suffers. Above 750 deg C the carbides over-coarsen and the room-temperature yield drops below the EN 10269 floor.
Q. Do you supply 21CrMoV5-7 in annealed condition for customer Q+T?
Yes, on call-out. Standard delivery is Q+T to EN 10269 mechanical-property floors. Annealed (700 to 750 deg C, slow furnace cool) for customer-side Q+T is supplied on heavy-section forgings (OD above 300 mm) where the customer prefers to control the Q+T cycle in-house.
Related Properties Pages
Drill into 21CrMoV5-7 properties: Chemical Composition · Mechanical Properties · Elevated-Temperature Properties · Hardness · Creep-Rupture · Welding Procedure · Machinability. Standards: EN 10269 · vs ASTM A193 B16. Back to the 21CrMoV5-7 Alloy Hub.
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