Analysis of ECCC cross-weld creep test data on grade 92 steel

ABSTRACT

The UK High Temperature Power Plant Forum have completed a long term cross-weld creep test programme on a Grade 92 steel pipe. This paper describes an analysis of the creep test data. The weld strength factor (WSF), i.e. the ratio of cross-weld strength to base material strength for a specified rupture time and temperature, is shown to be a unique function of a dimensionless parameter S, the creep test stress divided by ultimate tensile strength at the test temperature. The key practical finding is that, since a single universal cross-weld creep life parametric is applicable to all temperatures, long-term behaviour at service temperatures should reliably be predictable from short-term tests at accelerated temperatures.

KEYWORDS:

• Creep
• martensitic steel
• Grade 92
• steam pipe
• boiler header
• cross-weld test
• weld heat-affected zone
• “type IV” failure

Acknowledgments

Thanks are due to the UK High Temperature Power Plant Forum for supporting this work, to the EPSRC Supergen project consortium for their initial preparatory work, to Tenaris Dalmine for the supply of pipe material, to Doosan Babcock for weld manufacture, to Tata Steel and Doosan Babcock for carrying out creep testing, and to my previous employer E.On UK (now Uniper) for supporting my role as technical correspondent to HTPPF. Particular thanks are due to Philip Clarke at Tata Steel, to Mike Spindler (EDF) and Peter Barnard (then Doosan Babcock) for recovering the specimens from Swinden Laboratories after its closure, and to Peter for similarly retrieving the specimens and final test data after the closure of the Doosan Babcock creep laboratory.

Disclosure statement

No potential conflict of interest was reported by the author(s).