(Ti,nb)(C,N) precipitate characterization: from hot rolling to girth welding (ETCS)

1. (Ti,Nb)(C,N) precipitate characterization: from hot rolling to girth welding (ETCS)

Researchers: Lu Sun, Rishav Raj, Tailin Ren, Vanda Milani, Anqi Shao, Jonas Valloton, Barry Wiskel, Weixing Chen, Leijun Li, Douglas Ivey and Hani Henein

Funding: Evraz NA, TC Energy, CRC Evans, Accuren, SGS Canada, Canmet Materials and NSERC

Status: in progress

The goal of this partnership is to generate new knowledge on the processing and microstructural conditions for the formation of small TiN and (Ti,Nb)(C,N) precipitates in pipeline steels. The latter are less stable than the former. During hot rolling TiN is preferred as they pin down austenite grain boundaries. The conditions where a fine dispersion of TiN rather than (Ti,Nb)(C,N) forms needs to be determined. In addition, it is of interest to identify the process conditions that yield the formation of NbC and the relationship of these precipitates to toughness. The project seeks to generate a new understanding of the quantity, composition, location and size of TiN, (Ti,Nb)(C,N) and NbC precipitates and the microstructure evolution and properties of hot rolled product and girth welded heat affected zone (HAZ).[1,2] These pipeline steels are critical for the transport of energy procucts across Canada or internationally. These products include oil, natural gas, CO2 and hydrogen. This project will, therefore, provide the Sponsors (EVRAZ, TransCanada Pipelines Limited, CRC Evans, SGS Canada, Acuren and CanmetMATERIALS) with knowledge regarding the evolution of structure and precipitates during hot rolling and how they affect steel toughness. Additionally, the relationship between girth weld parameters and steel properties will provide Sponsors with knowledge on ways to assess the suitability of a steel for girth welding beyond simply the steel chemistry. Five HQP are planned to be trained on this project addressing the role of processing-structure and properties of these pipeline steels.