Mechanical Metallurgy on Columbia Gas X100 Experimental Pipe

Published

August 28, 2024

Author(s)

Dash Weeks, Ryan White, Jake Benzing, Enrico Lucon, Nicholas Derimow, Ashley Kroon, Robert Smith

Abstract

This study evaluates the material properties of an X100 pipeline steel extracted from an experimental transmission pipeline section placed into service in the 1960s. The purpose is to compare these properties with current X100 steel standards. Comprehensive chemical characterization, microstructure analysis, and a series of mechanical tests—including tensile, Charpy impact, and indentation tests—were conducted to assess the long-term stability and reliability of these early high-strength steels. The analysis involved seven different welded sections of the pipeline to account for potential variations within the material and welding procedures. The findings indicate significant differences in chemical composition across the various pipe sections, suggesting that these sections may represent different experimental materials. The base metal predominantly exhibited a bainite-ferrite microstructure, with noticeable variations near the pipe surfaces. Unannealed girth welds demonstrated higher toughness and increased hardness in their heat-affected zones compared to seam welds. While most sections of the vintage X100 steel met the modern tensile property requirements, several sections did not meet the impact toughness criteria. In conclusion, the experimental X100 steel aligns with current tensile property requirements, however the steel fails to meet current toughness related requirements. The observed differences in testing methods between current standards and those published in the 1960s were minor, and therefore not a convincing source for observed property differences considering all sources of uncertainty. The absence of original pre-service mechanical testing data prevents conclusions about time-dependent property changes.

Citation

NIST Interagency/Internal Report (NISTIR) - 8535

Report Number

8535

NIST Pub Series

NIST Interagency/Internal Report (NISTIR)

Pub Type

NIST Pubs

Download Paper

https://doi.org/10.6028/NIST.IR.8535

Local Download

Keywords

Pipeline steels, X100 pipe, Welding, Metallurgy, Mechanical engineering.

Citation

Weeks, D. , White, R. , Benzing, J. , Lucon, E. , Derimow, N. , Kroon, A. and Smith, R. (2024), Mechanical Metallurgy on Columbia Gas X100 Experimental Pipe, NIST Interagency/Internal Report (NISTIR), National Institute of Standards and Technology, Gaithersburg, MD, [online], https://doi.org/10.6028/NIST.IR.8535, https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=958123 (Accessed November 8, 2024)