PRELIMINARY ASSESSMENT OF THE FATIGUE ENDURANCE BEHAVIOUR OF THIN SECTION TUBULAR WELDMENTS MANUFACTURED FROM AUSTENITIC STEELS AT 525°C

摘要

It has been recognised that the mechanical performance of welded 316H stainless steel can vary significantly, dependent on the material section size, weld geometry and other parameters. As part of the continual development, enhancement and validation of the UK high temperature structural integrity assessment code, R5, the performance of thin section welded 316H structures have been targeted for investigation. Thus, thin section 316H tube material, TIG welded with 316L filler to produce one or two weld beads, have been evaluated in the present work. Two different weld configurations have been manufactured and coupon test pieces have been extracted for evaluation of the mechanical properties. These have consisted of a 2-pass butt TIG weld between two 316H plates (6mm thickness) and butt TIG welded 316H tubes (4mm wall thickness). In addition to these coupon tests, whole tubes, containing a central butt weld have been produced and tested at the service temperature to provide validation information for the analysis procedure. The work reported here will focus upon the experimental work performed, for example the production of small scale weld extract test pieces and a successful large scale tube validation test piece. The test data described here concentrates on the low cycle fatigue behaviour at a typical service temperature of 525°C. This work has shown that the welded tube validation tests display significantly lower lives than the coupon tests and potential reasons for this difference are suggested.