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- MERKBLATT AD 2000 W2/W7/W10
VdTÜV Werkstoffblatt 350 — German Pressure-Vessel Approval for Cr-Mo-V Bolting
VdTÜV Werkstoffblatt 350 (Wb 350) is the German Verband der TÜV material approval document for high-temperature bolting steels intended for pressure-vessel and steam-turbine service in the German regulatory regime. Durehete 1055 (20CrMoVTiB4-10 / 1.7729) and Durehete 950 (40CrMoV4-6 / 1.7711) are the two Durehete grades published under Wb 350 with full qualification data.
Scope
Wb 350 covers Cr-Mo-V and Cr-Mo-V-Ti-B bolting steels for service in pressure vessels and steam turbines under the German AD 2000-Merkblatt regime. The document publishes chemistry ranges, heat-treatment cycle, room-temperature mechanicals and the elevated-temperature design-stress envelope (analogous to EN 10269 Annex A but in the German regulatory format used by TÜV inspectors during pressure-vessel acceptance).
Relationship with EN 10269 and AD 2000
EN 10269 is the European harmonised technical-delivery standard. AD 2000-Merkblatt is the German pressure-vessel design code. Wb 350 is the bridge: it publishes the German-regulator-accepted version of the EN 10269 mechanical property and elevated-temperature data, in the format that AD 2000 design calculations reference. A bolt purchased to EN 10269 with a Wb 350 certificate is automatically acceptable in AD 2000 pressure-vessel construction.
Qualification Testing
Wb 350 qualification requires extended creep-rupture testing (typically 30,000-hour minimum) at three test temperatures, plus full chemistry verification, microstructure characterisation and impact testing across the temperature range. The VdTÜV publishes the consolidated data sheet only after the test programme is complete.
Import Route into India / UK Procurement
For Indian and UK power-generation OEM specifications, a Wb 350 mill certificate alongside the EN 10269 type 3.1 / 3.2 certificate is acceptable as evidence of TÜV-equivalent qualification. TorqBolt supplies Durehete 1055 and 950 with both certificate sets when the procurement specification calls for German pressure-vessel acceptance.
Frequently Asked Questions
What is VdTÜV Werkstoffblatt 350?
German Verband der TÜV material approval document for high-temperature Cr-Mo-V and Cr-Mo-V-Ti-B bolting steels in pressure-vessel and steam-turbine service. Durehete 1055 and 950 are both covered.
How does Wb 350 relate to EN 10269?
Wb 350 is the German regulatory bridge that translates EN 10269 design data into the AD 2000-Merkblatt format used by TÜV inspectors during pressure-vessel acceptance.
Do I need a Wb 350 certificate for Indian power-generation procurement?
Only when the OEM specification explicitly references German pressure-vessel acceptance or AD 2000-Merkblatt. EN 10269 type 3.1 or 3.2 is sufficient for most non-German OEMs.
How long does Wb 350 qualification take?
30,000-hour creep-rupture testing at three temperatures is the minimum. Total qualification programme runs 4-7 years; the published Wb 350 data sheet consolidates the result.
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