Abstract: Two experimentally produced seamless-pipe steels with the same chemical composition were studied using Advanced Microstructural Characterization and non-destructive testing electromagnetic-acoustic transducer (NDT-EMAT) analysis. A systematic study was conducted to determine the factor(s) responsible for the variability in the impact toughness behavior exhibited by the steels. The samples studied had two different final wall-thickness. The sample with the thicker wall-thickness complied with the desired tensile properties (YS, UTS, and %El) including impact toughness values, while the steel with the thinner wall-thickness showed lower impact toughness values. The characterization included: a) evaluation of chemical composition; b) nondestructive Electromagnetic Acoustic Transducer (EMAT) ultrasound testing which provided valuable information regarding microstructural inhomogeneity in the bad material; c) analysis of the type and morphology of non-metallic inclusions and grain size variation; d) use of EDS analysis to assess local segregation; and e) scanning electron microscopy and OIM-EBSD for grain boundary character distribution (GBCD), image quality (IQ) of the microstructural constituents, phase identification and volume fraction assessment. The results of this study are presented and discussed.
Authors: Gregorio Solis Bravo and C. Isaac Garcia
Keywords: LP Steel Impact Toughness, Seamless Pipe, EMAT, Advanced Microstructural Characterization