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
21CrMoV5-7 (Werkstoff 1.7709) and Durehete 1055 are the mid-tier and premium grades of the Cr-Mo-V Q+T bolting steel family. Durehete 1055 is a trade name for the Tata Steel (formerly British Steel) Ti+B microalloyed grade, designated 20CrMoVTiB4-10 (Werkstoff 1.7729) in EN 10269 and Alloy T41 / T44 in the older British nomenclature. The differences are titanium and boron additions in Durehete 1055 that pin austenite grain boundaries during long-life service. Durehete 1055 holds higher proof stress at 550-600 deg C, qualifying it for the upper-IP and HP turbine casing flange bolting that 21CrMoV5-7 cannot serve.
Chemistry side by side
| Element (wt%) | 21CrMoV5-7 (EN 10269) | Durehete 1055 / 20CrMoVTiB4-10 (1.7729) |
|---|---|---|
| Carbon (C) | 0.17 to 0.25 | 0.17 to 0.23 |
| Silicon (Si) | max 0.40 | max 0.40 |
| Manganese (Mn) | 0.40 to 0.80 | 0.35 to 0.75 |
| Phosphorus (P) | max 0.025 | max 0.020 |
| Sulfur (S) | max 0.030 | max 0.020 |
| Chromium (Cr) | 1.20 to 1.50 | 0.90 to 1.20 |
| Molybdenum (Mo) | 0.55 to 0.80 | 0.90 to 1.10 |
| Vanadium (V) | 0.20 to 0.35 | 0.60 to 0.80 |
| Titanium (Ti) | not specified | 0.07 to 0.15 |
| Boron (B) | not specified | 0.001 to 0.010 |
The premium-tier signatures are higher Mo, much higher V, and the Ti+B microadditions. Titanium ties up free nitrogen and pins grain boundaries; boron strengthens the boundaries during creep. The result is a measurable lift in long-life proof-stress at 550-600 deg C.
Mechanical property floor
| Property | 21CrMoV5-7 (+QT, d ≤ 160 mm) | Durehete 1055 (+QT, d ≤ 100 mm) |
|---|---|---|
| 0.2 percent proof stress, min | 550 MPa | 660 MPa |
| Tensile strength | 700 to 850 MPa | 820 to 1000 MPa |
| Elongation A5, min | 16 percent | 15 percent |
| Reduction of area, min | 60 percent | 50 percent |
| Charpy V impact at +20 deg C, min | 63 J | 40 J |
Durehete 1055 trades a small amount of room-temperature toughness for substantially higher proof stress, which is what matters for design at temperature.
When to specify 21CrMoV5-7
- Service temperature up to 550 deg C continuous.
- The mid-tier strength envelope is sufficient for the bolted joint.
- Cost optimisation matters; Ti+B microalloying carries a premium.
- EN 10269 procurement framework defaults to this grade for general turbine and pressure-vessel bolting.
When to specify Durehete 1055
- Service temperature in the 550-600 deg C band where 21CrMoV5-7 starts to soften.
- Upper-IP and HP turbine casing flange bolting on supercritical and ultra-supercritical units.
- Long-life creep performance is the design driver and the strength premium justifies the alloy cost.
- OEM specification calls out Durehete 1055, Alloy T41, T44, 20CrMoVTiB4-10 or Werkstoff 1.7729 by name.
Related cross-references
- vs ASTM A193 B16 — the US mid-tier analogue
- vs 21CrMoV5-11 — heavier-section sister of 21CrMoV5-7
- 21CrMoV5-7 creep-rupture envelope
- EN 10269 equivalents master table
FAQs
Q. Is Durehete 1055 the same as Alloy T41?
Yes. Durehete 1055 is the Tata Steel trade name; Alloy T41 (and the closely related T44) are the older British designations. 20CrMoVTiB4-10 is the EN 10269 designation, and Werkstoff 1.7729 is the German material number. All four refer to the same Ti+B microalloyed Cr-Mo-V bolting steel.
Q. What does Ti+B do?
Titanium ties up free nitrogen and pins prior-austenite grain boundaries during long-life service. Boron strengthens grain boundaries against creep cavitation. The combination lifts the long-life proof stress at 550-600 deg C above what plain Cr-Mo-V (21CrMoV5-7, B16) can deliver.
Q. Why not always use Durehete 1055?
Cost. Ti+B microadditions, tighter chemistry windows, and the higher Mo and V loadings make Durehete 1055 substantially more expensive than 21CrMoV5-7. For service below 550 deg C the premium is not justified.
Q. Can TorqBolt supply both grades?
Yes. Both are supplied as stud bolts, hex bolts, heavy hex bolts, and forged blanks with EN 10204 type 3.1 or 3.2 certification against the relevant standard (EN 10269 or BS 1506-621 for Durehete 1055).
Satisfaction Survey
