Improvements in Creep Ductility of the UK Cast MarBN steel, IBN1

Improvements in Creep Ductility of the UK Cast MarBN steel, IBN1

 

Prof Scott Lockyer¹, Mr Steve Roberts², Dr Martin Strangwood³, Simran Thandi⁴ and Dr Mark Jepson⁴

 

There has been extensive research and development undertaken in the UK on MarBN steels. These steels were first proposed by Professor Fujio Abe at NIMS in Japan and the work in the UK has done much to commercialise them via a number of Government funded industrial collaborative projects (IMPACT, IMPEL, INMAP, IMPULSE and IMPLANT). These projects have resulted in a number of significant achievements including: installation of trial tubes in an operational power plant; production of full-scale extruded pipes; development of a matching welding consumable; and most importantly, a new steel, IBN-1, with creep strength 30-45% higher than Grade 92. However, similar to other creep strength enhanced ferritic steels, a reduction in creep ductility is observed at lower stresses representative of operation. Good creep ductility is necessary to ensure components have adequate damage tolerance and allow effective in-service condition monitoring. This paper reports the results of creep rupture tests from an IBN1 cast subject to an alternative normalising and tempering heat treatment that exhibits improved creep ductility and the analysis undertaken to determine any microstructural reasons for this behaviour.

 

¹ Uniper Technologies Limited

² Goodwin Steels Castings Ltd

³ University of Birmingham

⁴ Loughborough University