Fracture mechanics and wide-plate tests for analysis of nitrogen and strain aging effects on weld metal fracture properties

The effects of nitrogen and strain aging on C- Mn steel weld metal toughness and fracture characteristics were investigated by means of fracture mechanics. Multipass shielded metal arc weld metal bearing a total nitrogen content in the range of 80 to 210 ppm have been tested by using mini wide plates (WP) in tension and crack tip opening displacement (CTOD) specimens under four different conditions, viz., 1) As-Welded (AW), 2) Stress Relieved (SR): 580 C/120 min., 3) Artificially Strain Aged (SA): 10% cold deformation + 250 C/30 min. and 4) Artificially Strain Aged and Stress Relieved (SAS). In order to obtain specimens in SA condition, the welds were artificially strained (10% compression in plate thickness direction) and aged. The CTOD and sixteen through thickness center cracked wide-plate specimens with transverse weld metal were tested at room temperature to determine the sensitivity of each test type to the nitrogen and strain age embrittlement. The weld metal yield and ultimate tensile strengths increased with increasing nitrogen content for all four conditions. Results of the small scale CTOD tests clearly show that nitrogen and strain aging have a definite embrittling effect on the weld metal toughness and R-curve behaviour. The wide-plate test results, however, did not show a similar sensitivity to the nitrogen content and strain aging as CTOD tests showed and all of the WP plates fractured in fully ductile manner. (orig.)SIGLEReprinted from: Salama, M.M.; Webster, S.E.; Haswell, J.V.; Patterson, E.A.; Haagensen, P.J. (eds.): Proceedings of the 12. International conference on OMAE 1993, vol. 3, Pt. B, p. 741-751 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman