Estimating steel line pipe toughness using composition and microstructure

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Citation: Switzner, N., Anderson, J., Rosenfeld, Veloo, P., Gibbs, J., Gonzalez, R., “Assessing steel pipe toughness using chemical composition and microstructure,” Pipeline Pigging and Integrity Management (PPIM), Paper #57, Houston, TX, February 22-26, 2021.
Link: www.researchgate.net/publication/350040295_Assessing_steel_pipe_toughness_using_chemical_composition_and_microstructure
Revisions to federal natural gas regulations introduced the process of Maximum Allowable Operating Pressure (MAOP) reconfirmation using the method of Engineering Critical Assessment (ECA). ECA requires Operators to perform defect and remaining life assessments that require data regarding pipeline feature toughness. Traditionally, toughness has been estimated using laboratory Charpy V-notch (CVN) testing. In the absence of laboratory toughness test data operators may use appropriate toughness values that demonstrably “provide conservative [CVN] toughness values of crack-related conditions of the pipeline segment” per 49 CFR § 192.712(e)(2)(i)(E).
Steel pipe manufacturers utilize composition and microstructure to achieve their targeted strength and toughness values. Pacific Gas and Electric Company (PG&E) coordinated the collection of destructive test data from two vendors that had performed laboratory composition, microstructure, and CVN testing on steel pipes and fittings that varied in terms of size, vintage, and grade. Utilizing these data, in addition to detailed knowledge of the evolution of historical pipe manufacturing processes, an exploratory study has been performed into the viability of utilizing NDE chemical composition and in-situ metallography to estimate toughness. Several models to predict CVN upper shelf energy and the CVN ductile to brittle transition temperature were constructed so that the most appropriate model can be selected from among the available models based on compositional elements and microstructural data inputs.