Creep Behaviour of Welding Connections up to 620 °C

Project Number 197

In order to be able to exploit the potential of the new steels (E 911, 7CrMoV TIB1010, 1.4910), which have been developed for use in large steam generators with high efficiencies for the steam generator components "membrane wall" and "superheater outlet manifold", it is necessary to optimise and qualify the welds. To do this, a reliable database is necessary which will be built up in the following stages:

• description of the failure behaviour with static, nearly realistic stresses,
• predicting the operating behaviour on the basis of experimental results of the stresses in the welds,
• determining the toughness taking thermally-induced segregation processes into account.

This project will be managed by the State Materials Testing Organisation (MPA) of the University of Stuttgart, Prof. Eberhard Roos, in co-operation with three steam generator manufacturers. The work is a continuation of an earlier project "Qualification of Materials for Use in Steam Generators with Increased Efficiency" which was also promoted by the VGB under project number 136.

This will help to establish the statistical certainty of the previous results and also provide information on the strength characteristics. In overall terms, principles will be acquired for the design and fatigue analysis of welds for qualifying the materials for power plants to be built in the future. The results will be included in the engineering standards.

The project will be managed by the VGB Technical Committee "Materials and Quality Supervision" and will be co-ordinated with other projects promoted by the VGB as part of VGB's research theme "New Materials for Power Plants" (NWK).