Influence of microstructure on SSC and SOHIC in base materials and welded joints of high strength sour service steels
The main objective of the project is to assess the effect of relevant metallurgical parameters on the resistance to SSC and SOHIC of welded joints in spiral pipes, linepipes and pressure vessels, throughout the validation of laboratory testing methodologies. Considering X60 grade steels with different rolling parameter combinations, the main conclusions were a much better toughness using the lower temperature practices, but HIC cracks close to the spiral weld. Pulsating tests for SOHIC demonstrate the effect of cycles number and loading/relieve time (reducing the number of cycles to breaking by higher times for loading and relieve, independent by strain level). Considering GMAW and SMAW girth welds of Q&T X60 steels no HIC cracks were observed. The SSC tests in NACE sol. A, showed a good performance on GMAW joints (until 90% AYS), while SMAW microstructure, with lower content of chromium, nickel and molybdenum showed a lower SSC toughness both by constant load and pulsating tests. No HIC cracks but only Sulphide stress cracks were observed in all conditions by a newly proposed NACE T8-23 test method (an adaptation of ASTM G 39). Considering SAW longitudinal welds of Q&T steels, with fully bainitic microstructure, both no HIC and SSC cracks (until 80% SMYS) were found. The SOHIC tests, according newly proposed NACE T8-23, didn't show cracks (until 100% SMYS) only with high heat input and PWHT. Considering SAW wells of Q&T steel with fine microstructure of ferrite+perlite, a slight HIC susceptibility was found with a benefic effect of tempering and PWHT.
Bibliographic Reference: EUR 21906 EN (2006), 93 pp. Euro: 15
Availability: Katalogue Number: KI-NA-21906-EN-S The paper version can be ordered online and the PDF version downloaded at: http://bookshop.europa.eu
ISBN: ISBN: 92-79-01105-7
Record Number: 200719301 / Last updated on: 2007-07-10
Original language: en
Available languages: en