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 Frequently Asked Questions
Consolidated reference of the questions our QA and procurement teams answer most often about 21CrMoV5-7 (Werkstoff 1.7709) bolting steel. Each answer links through to the dedicated detail page when more depth is needed.
Have a question not covered below? Send us a project enquiry.
Designations and Identification
Q. What is the correct Werkstoff number for 21CrMoV5-7?
Werkstoff 1.7709. Older or fabricated references that quote 1.7783 are wrong; 1.7783 is X22CrMoV12-1, a 12 percent chromium martensitic stainless steel for steam-turbine blades, an entirely different alloy class.
Q. Is 21CrMoV5-7 the same as 21CrMoV5-11?
No. 5-11 (Werkstoff 1.8070) has a higher Mo range (0.90 to 1.10 percent vs 0.55 to 0.80 percent for 5-7) and is the heavier-section variant. For OD up to 200 mm, 5-7 is the workhorse; above 200 mm fully-hardened, 5-11 is the preferred grade. See vs 21CrMoV5-11.
Q. What is the AFNOR or French designation for 21CrMoV5-7?
20CDV5.7 per NF A35-559. The Polish PN equivalent is 21HMF per PN-89/H-84030. See vs 20CDV5.7 and vs 21HMF.
Chemistry and Mechanicals
Q. What chemistry windows govern 21CrMoV5-7?
C 0.17 to 0.25, Si max 0.40, Mn 0.40 to 0.80, P max 0.030, S max 0.030, Cr 1.20 to 1.50, Mo 0.55 to 0.80, V 0.20 to 0.35, Ni max 0.60, Al max 0.030. Full element-by-element roles on the chemistry page.
Q. What are the room-temperature mechanical-property floors?
Tensile 700 to 850 MPa, 0.2 percent proof stress at least 550 MPa, elongation A5 at least 16 percent, Charpy V impact at least 63 J at 20 deg C. Full elevated-temperature data on the mechanicals page.
Heat Treatment and Welding
Q. What Q+T cycle do you run for 21CrMoV5-7?
Austenitise 880 to 940 deg C (1 hour per 25 mm section), oil quench, temper 680 to 740 deg C (minimum 2 hours), air cool. Detail on the heat treatment page.
Q. What welding consumable matches 21CrMoV5-7?
Matched-composition Cr-Mo-V low-hydrogen filler with preheat 200 to 300 deg C and PWHT 690 to 720 deg C. Full procedure on the welding page.
Service Temperature and Grade Selection
Q. What is the maximum service temperature for 21CrMoV5-7?
550 deg C continuous to EN 10269. Above 550 deg C the design steps up to Durehete 1055 (Alloy T41 / 1.7729). Below 450 deg C ASTM A193 B7 is the cheaper correct choice.
Q. Is 21CrMoV5-7 an exact substitute for ASTM A193 B16?
Close but not exact. Both are Cr-Mo-V Q+T bolting steels with overlapping chemistry and similar envelope. See vs ASTM A193 B16.
Q. What is VdTUV Wb 350 and is 21CrMoV5-7 approved under it?
VdTUV Werkstoffblatt 350 is the German pressure-vessel approval scope for bolting steels. 21CrMoV5-7 is approved. Detail on the VdTUV Wb 350 page.
Procurement and Documentation
Q. What size range do you supply 21CrMoV5-7 in?
Round bar OD 16 to 300 mm; stud bolts M12 to M120 (lengths 50 to 800 mm); hex bolts and heavy hex bolts to M64 / 4 inch. Forgings up to 800 kg piece weight on call-out.
Q. What inspection documentation do you supply?
EN 10204 type 3.1 by default; type 3.2 with Lloyd's, DNV, BV, SGS or TUV witness on call-out and standard for turbine and pressure-vessel work.
Q. Where can I download the 21CrMoV5-7 datasheet?
On the 21CrMoV5-7 datasheet page along with the EN 10269 specification reference.
21CrMoV5-7 Chemistry (Werkstoff 1.7709 Element Ranges)
21CrMoV5-7 (Werkstoff 1.7709) chemistry is fixed within a tight Cr-Mo-V Q+T window to EN 10269. Carbon at 0.17 to 0.25 percent gives the Q+T hardenability backbone without over-hardening for the secondary temper. Chromium at 1.20 to 1.50 percent provides through-thickness hardenability and stabilises the carbide network for creep. Molybdenum at 0.55 to 0.80 percent suppresses temper embrittlement and contributes to the secondary hardening peak. Vanadium at 0.20 to 0.35 percent drives the V4C3 precipitation during the 680 to 740 deg C temper that locks in the creep envelope. The chemistry window is shared with the AFNOR 20CDV5.7 (French) and Polish 21HMF designations.
| Element | Min % | Max % | Role |
|---|---|---|---|
| Carbon (C) | 0.17 | 0.25 | Q+T hardenability |
| Silicon (Si) | — | 0.40 | Deoxidation |
| Manganese (Mn) | 0.40 | 0.80 | Hardenability + solid-solution |
| Phosphorus (P) | — | 0.030 | Tramp limit for toughness |
| Sulphur (S) | — | 0.030 | Tramp limit |
| Chromium (Cr) | 1.20 | 1.50 | Hardenability + creep |
| Molybdenum (Mo) | 0.55 | 0.80 | Secondary hardening |
| Vanadium (V) | 0.20 | 0.35 | V4C3 carbide strengthening |
| Nickel (Ni) | — | 0.60 | Residual |
| Aluminium (Al) | — | 0.030 | Grain refinement |
Creep Performance at 500-550 deg C (EN 10269 Annex A)
The defining value-prop of 21CrMoV5-7 is the secondary-hardening creep envelope driven by V4C3 carbide precipitation. The fine V4C3 dispersion formed during the 680 to 740 deg C temper pins dislocation motion during long-time elevated-temperature service. The result is a 100,000-hour stress-rupture envelope to EN 10269 Annex A of approximately 340 MPa at 500 deg C, 290 MPa at 525 deg C, 260 MPa at 540 deg C, and 180 MPa at 550 deg C. Above 550 deg C the V4C3 coarsens faster than the design can tolerate; this is the boundary where the design must step up to Durehete 1055 (Alloy T41 / 1.7729) with Ti+B microalloying for grain-boundary pinning that extends the envelope to 568 deg C continuous service.
| Temperature | 100,000 h rupture stress | 1 percent creep strain at 100,000 h |
|---|---|---|
| 450 deg C | ~470 MPa | ~380 MPa |
| 500 deg C | ~340 MPa | ~280 MPa |
| 525 deg C | ~290 MPa | ~235 MPa |
| 540 deg C | ~260 MPa | ~210 MPa |
| 550 deg C | ~180 MPa | ~150 MPa |
Heat Treatment (Q+T Cycle)
The standard cycle for 21CrMoV5-7 is austenitisation at 880 to 940 deg C with hold time of 1 hour per 25 mm section, followed by oil quench. The temper is at 680 to 740 deg C for minimum 2 hours then air cool. The temper temperature is chosen to land on the secondary-hardening peak; below 660 deg C the V4C3 carbide precipitation is under-developed and long-term creep performance suffers; above 750 deg C the carbides over-coarsen and the room-temperature yield drops below the EN 10269 floor of 550 MPa. For heavily machined fastener blanks where dimensional stability matters, a stress relief at 50 deg C below the final temper is recommended after machining.
Welding Procedure (Matched Cr-Mo-V Filler + PWHT)
21CrMoV5-7 is welded with matched-composition Cr-Mo-V low-hydrogen filler (AWS A5.5 E9018-B3L for SMAW, AWS A5.28 ER90S-B3L for GTAW, AWS A5.23 EB3 for SAW) under preheat 200 to 300 deg C and diffusible-hydrogen cap of 5 ml per 100 g deposited. Post-weld heat treatment at 690 to 720 deg C for 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 metal verifies the PWHT achieved the intended tempering; HAZ hardness must not exceed 320 HBW.
Material Selection: 21CrMoV5-7 vs ASTM A193 B16 vs B7 vs Durehete 1055
21CrMoV5-7 sits between ASTM A193 Grade B7 (carbon-Mo only, no vanadium, capped at 450 deg C) and Durehete 1055 (Alloy T41 with Ti+B microalloying, 568 deg C envelope). Its direct US cousin is ASTM A193 Grade B16, with overlapping Cr-Mo-V chemistry and similar 540 deg C service envelope. Dual-certification to EN 10269 21CrMoV5-7 plus ASTM A193 B16 from the same heat lot is standard practice on cross-procurement projects.
| Grade | Chemistry | Max temp | When to specify |
|---|---|---|---|
| ASTM A193 B7 | Cr-Mo (no V) | 450 deg C | Lower-temp bolting where cost matters |
| 21CrMoV5-7 | Cr-Mo-V Q+T | 550 deg C | Workhorse mid-tier turbine + power + refinery |
| ASTM A193 B16 | Cr-Mo-V Q+T | 540 deg C | US dual-cert cousin |
| 21CrMoV5-11 (1.8070) | Cr-Mo-V Q+T higher Mo | 550 deg C | Heavier section (OD above 200 mm) |
| Durehete 1055 (Alloy T41 / 1.7729) | Cr-Mo-V-Ti-B | 568 deg C | HP turbine + supercritical + USC |
Related Reference Pages
More reference materials: Datasheet (PDF) · Torque Chart · Bolt Dimensions · Stress-Rupture Tables. Back to the 21CrMoV5-7 Alloy Hub.
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