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
Durehete 1055 vs 21CrMoV5-7 — EN 10269 Cr-Mo-V Bolting Steel Comparison
Durehete 1055 (Alloy T41 / 20CrMoVTiB4-10 / Werkstoff 1.7729) and 21CrMoV5-7 (Werkstoff 1.7709) sit in the EN 10269 Cr-Mo-V bolting family. The procurement decision hinges on the Ti+B microalloying that distinguishes 1055 from 21CrMoV5-7 and the 25-50°C of additional service temperature it delivers.
Chemistry Comparison
| Element (wt %) | Durehete 1055 (20CrMoVTiB4-10) | 21CrMoV5-7 |
|---|---|---|
| Carbon | 0.17 to 0.23 | 0.17 to 0.25 |
| Silicon, max | 0.40 | 0.40 |
| Manganese | 0.35 to 0.75 | 0.40 to 0.70 |
| Chromium | 0.90 to 1.20 | 1.20 to 1.50 |
| Molybdenum | 0.90 to 1.10 | 0.45 to 0.65 |
| Vanadium | 0.60 to 0.80 | 0.20 to 0.40 |
| Titanium | 0.07 to 0.15 | not specified |
| Boron, max | 0.020 | not specified |
1055 has higher Mo (0.90-1.10 vs 0.45-0.65) and higher V (0.60-0.80 vs 0.20-0.40), plus the Ti+B microalloying that 21CrMoV5-7 lacks entirely.
Mechanical Comparison (Q+T condition)
| Property | Durehete 1055 | 21CrMoV5-7 |
|---|---|---|
| Tensile strength, room temp | 820 to 1000 MPa | 700 to 850 MPa |
| 0.2% proof stress, min | 660 MPa | 540 MPa |
| Elongation, min | 16% | 17% |
Service Envelope
1055 covers 565°C continuous service; 21CrMoV5-7 covers approximately 510-525°C. The 40-55°C gap is the result of the higher Mo and V content plus the Ti+B grain-boundary pinning that prevents M23C6 carbide coarsening at long-duration exposure above 525°C.
When to Specify Each Grade
Specify Durehete 1055 for HP turbine casing flanges, supercritical and ultra-supercritical bolting, fired-heater radiant section, and any application where casing skin exceeds 525°C. Specify 21CrMoV5-7 for IP and LP turbine casings, subcritical balance-of-plant, lower-temperature pressure-vessel bolting where the cost premium of Ti+B microalloying isn't justified.
Frequently Asked Questions
Are Durehete 1055 and 21CrMoV5-7 interchangeable?
Below 510°C continuous service, yes. Above 525°C, only 1055 covers the EN 10269 Annex A 100,000-hour creep envelope.
What does the Ti+B microalloying actually do?
Titanium ties up free nitrogen and forms TiC plus TiN dispersoids; boron segregates to grain boundaries. The combined effect pins grain boundaries against M23C6 carbide coarsening at long-duration high-temperature exposure.
Is 21CrMoV5-7 cheaper than Durehete 1055?
Yes, typically 15-25 percent lower mill cost due to lower alloy content (Mo, V) and absence of Ti+B microalloying control. Cost difference erodes when the higher service envelope of 1055 is required.
Can I dual-certify both grades to ASTM A193 B16?
Both grades broadly map to A193 B16 territory but B16 chemistry envelope is tighter on Cr (0.80-1.15) and falls between the two EN grades. Specific dual certification requires negotiating the heat-treatment target with the mill.
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