Welding advanced martensitic creep-resistant steels with boron containing filler metal

S. Baumgartner, G. Posch, P. Mayr

Research output: Contribution to journalArticlepeer-review

13 Scopus citations

Abstract

Within the last years, the benefi cial effect of boron addition in order to increase the creep strength of martensitic 9-12 % Cr steels has been widely investigated and demonstrated. Several boron-strengthened alloys are the outcome of an intensive European research activity within the scientifi c framework of COST. The most promising alloy for castings with a targeted application temperature of 650 °C for use in future ultra-super critical steam power plants is a modifi ed 0.1C-9Cr-1.5Mo steel with the addition of approximately 110 ppm boron. For joining of this advanced steel grade, new "chemically matching" welding consumables have to be developed to provide similar creep strength in the weld. Within this paper, the development of an advanced fl ux-cored wire with a good "out of position weldability" - based on a rutile slag system is presented. The work discusses the optimization of the chemical composition of the fi ller, the infl uence of various post-weld heat treatments on short term mechanical properties, fi rst results of creep tests and results of thick section welds. The boron content of the consumable was optimized to achieve highest creep strength combined with acceptable toughness and lowest hot cracking sensitivity. For a butt weld of a 34 mm-thick casting, the optimum welding parameters and layer sequence were determined. A post-weld heat treatment consisting of stress relieving twice at 730 °C for 12 h seemed to be the best compromise between applicability in the manufacturing of large turbine casings and achievement of acceptable weld toughness.

Original languageEnglish
Pages (from-to)2-9
Number of pages8
JournalWelding in the World
Volume56
Issue number7-8
DOIs
StatePublished - 2012
Externally publishedYes

Keywords

  • B additions
  • Castings
  • Creep resisting steels
  • FCA welding

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