Experiences in the use of advanced materials for Ultra Super Critical thermoelectric power plants: ASTM P92 grade and its weldability

Abstract

Currently, ASTM A335 P92 is the best available material for manufacturing major steam lines and manifolds for modern Ultra Super Critical thermoelectric power stations, in that it combines high resistance to a viscous creep, high microstructural stability, and good resistance to steam corrosion and oxidation. These characteristics allow it to be used at up to 620°C and at pressures of up to 320 bar. Welding this material, characterized by a high alloy content, requires particular attention with regard to the control of the operating conditions. In this paper, Tenaris and the Italian Welding Institute present a joint study investigating the weldability of Grade 92, in which the effect of varying significant parameters such as preheating, interpass, and post-welding treatments on joint mechanical and microstructural properties has been examined.

Keywords:

• creep
• creep-resisting materials
• creep strength
• creep tests
• elevated temperature strength
• hardness tests
• heat affected zone
• high alloy Cr Mo steels
• high temperature
• influencing factors
• mechanical properties
• mechanical tests
• metallography
• microstructure
• multirun welding
• post weld heat treatment
• post weld operations
• power stations
• preheating
• service conditions
• temperature
• toughness, weld zone
• weldability

Notes

Paper presented at the IWI Training and Refresher Day: ‘Welding of Cr–Mo low alloy steels for high temperature applications and Ni alloy steels for cryogenic operations’, Genoa, 20 May 2010.