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 vs Durehete 1055 (Alloy T41 / Werkstoff 1.7729) (EN 10269 Cross-Reference)
21CrMoV5-7 (Werkstoff 1.7709) and Durehete 1055 (Alloy T41 / Werkstoff 1.7729 / 20CrMoVTiB4-10) are the workhorse and premium Cr-Mo-V bolting grades for steam turbine and high-temperature pressure-vessel service. Durehete 1055 adds titanium and boron microalloying for extended creep envelope to 568 deg C; 21CrMoV5-7 holds to 550 deg C with the simpler Cr-Mo-V chemistry.
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At a Glance
| 21CrMoV5-7 | Durehete 1055 (Alloy T41) | |
|---|---|---|
| Werkstoff | 1.7709 | 1.7729 (20CrMoVTiB4-10) |
| Standard | EN 10269 | EN 10269 |
| Service envelope | up to 550 deg C | up to 568 deg C |
| Microalloying | none | Ti 0.04-0.10, B 0.0010-0.0050 |
| Use case | Workhorse mid-tier | Premium HP turbine bolting |
| Cost per kg | Mid | High (Ti+B addition) |
Chemistry Comparison
| Element | 21CrMoV5-7 | Durehete 1055 |
|---|---|---|
| C | 0.17 to 0.25 | 0.17 to 0.24 |
| Cr | 1.20 to 1.50 | 0.80 to 1.20 |
| Mo | 0.55 to 0.80 | 0.55 to 0.75 |
| V | 0.20 to 0.35 | 0.20 to 0.40 |
| Ti | none | 0.04 to 0.10 |
| B | none | 0.0010 to 0.0050 |
Mechanical Comparison
| Property | 21CrMoV5-7 | Durehete 1055 |
|---|---|---|
| Tensile (Rm) | 700 to 850 MPa | 820 to 1000 MPa |
| 0.2 percent proof (RT) | ≥550 MPa | ≥680 MPa |
| Max service temp | 550 deg C | 568 deg C |
| Long-term creep (10^5 h at 540 deg C) | ~260 MPa | ~300 MPa |
When to Specify Which
Specify 21CrMoV5-7 for the bulk of turbine bolting (LP, IP, lower HP casings up to 550 deg C). Specify Durehete 1055 for upper HP casings above 550 deg C, supercritical main bolting, and ultra-supercritical projects where the Ti+B microalloyed creep envelope is required. For most subcritical power-plant work, the cheaper 21CrMoV5-7 is the design choice.
Form Availability
Both grades supplied in round bar and the full bolting form-factor range: stud bolts, hex bolts, heavy hex bolts, tap studs, nuts, washers and threaded rod.
Frequently Asked Questions
Q. What does the Ti+B microalloying do in Durehete 1055?
Titanium tied to nitrogen forms TiN precipitates that pin grain boundaries against creep cavitation. Boron segregates to prior-austenite grain boundaries and stabilises them against creep damage. The combined effect extends the 100,000-hour creep envelope by 30 to 50 MPa at 540 deg C compared to plain Cr-Mo-V.
Q. Can I substitute 21CrMoV5-7 for Durehete 1055 to save cost?
Only below 550 deg C service temperature. Above 550 deg C the V4C3-only chemistry of 21CrMoV5-7 lacks the Ti+B grain-boundary pinning and the long-term creep performance drops. The cost saving is consumed by reduced bolt life.
Q. Is Durehete 1055 the same as ASTM A540?
Closer to ASTM A540 Grade B23 or B24 than to ASTM A193 Grade B16. Durehete 1055 sits above the ASTM A193 envelope. Cross-procurement on US-design turbines uses ASTM A540 Grade B24 with dual-cert on call-out.
Q. Where can I get more detail on Durehete 1055?
The dedicated Durehete 1055 alloy hub is at durehete.com (TorqBolt sister site).
Related Cross-References
More cross-references: vs ASTM A193 B16 · vs ASTM A193 B7 · vs ASTM A193 B8 · vs 21CrMoV5-11 · vs 24CrMoV5-5 · vs 20CDV5.7 (AFNOR) · vs 21HMF (Polish) · vs 42CrMo4. Back to the 21CrMoV5-7 Alloy Hub.
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