Continuous cooling transformation from coarse-grained austenite in X80 line pipe steels
department or school: Applied Science, Faculty of
department or school: Materials Engineering, Department of
data provider: DSpace
degree campus: UBCV
creator: Yamada, Kaiya
issued: 2023-01-05T17:54:57Z
issued: 2022
related degree: Master of Applied Science - MASc
degree grantor: University of British Columbia
description: Oil and natural gas are important contributors to Canada’s energy sector, and pipelines are the most prevalent means of transporting these products. Modern Canadian pipelines are produced from advanced line pipe steels that have suitable properties for their applications as they are manufactured with the thermomechanical-controlled process (TMCP) and contain an optimized steel chemistry, including a low carbon content usually below 0.1wt% and specific additions of microalloying elements. When the line pipe segments are welded, the region next to the fusion zone experiences rapid heating and subsequent rapid cooling, creating a heat-affected zone (HAZ). The microstructure and, thus, the mechanical properties of the HAZ may be different from that of the as-rolled steel and may have a detrimental effect on pipeline integrity. The area of the HAZ closest to the fusion boundary, referred to as the coarse-grain heat-affected zone (CGHAZ), is subjected to temperatures high enough to dissolve precipitates, such as niobium carbonitrides. The dissolution of these precipitates may result in significant coarsening of the austenite grains. The resulting microstructural changes can lead to inadequate properties, such as insufficient toughness and strength. The purpose of this study was to investigate austenite decomposition kinetics during continuous cooling from coarse-grained austenite in three different line pipe steels with variations in chromium and molybdenum levels. Thermal conditions were simulated with a Gleeble 3500 thermomechanical simulator. Samples were continuously cooled at rates of 3, 5, 10, 30 and 50℃/s. Resulting microstructures were examined with optical microscopy and electron backscatter diffraction (EBSD) analysis. Hardness was measured with a Vickers hardness tester. An increase in molybdenum content from 0.11wt% to 0.26wt% resulted in a decrease in transformation start temperature by approximately 15℃ for all cooling rates. Lower transformation temperature…
aggregated CHO: https://circle.library.ubc.ca/rest/handle/2429/83581
note: Continuous Cooling Transformation from Coarse-Grained Austenite in X80 Line Pipe Steels by KAIYA YAMADA B.A.Sc., The University of British Columbia, 2019 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF APPLIED SCIENCE in THE FACULTY OF GRADUATE AND POSTDOCTORAL STUDIES (Materials Engineering) THE UNIVERSITY OF BRITISH COLUMBIA (VANCOUVER) December 2022 © Kaiya Yamada, 2022 ii The following individuals certify that they have read, and recommend to the Faculty of Graduate and Postdoctoral Studies for acceptance, the thesis entitled: Continuous Cooling Transformation from Coarse-Grained Austenite in X80 Line Pipe Steels submitted by Kaiya Yamada in partial fulfillment of the requirements for the degree of Master of Applied Science in Materials Engineering Examining Committee: Matthias Militzer, Professor, Materials Engineering, UBC Supervisor Warren J. Poole, Professor, Materials Engineering, UBC Supervisory Committee Member Rizhi Wang, Professor, Materials Engineering, UBC Supervisory Committee Member iii Abstract Oil and natural gas are important contributors to Canada’s energy sector, and pipelines are the most prevalent means of transporting these products. Modern Canadian pipelines are produced from advanced line pipe steels that have suitable properties for their applications as they are manufactured with the thermomechanical-controlled process (TMCP) and contain an optimized steel chemistry, including a low carbon content usually below 0.1wt% and specific additions of microalloying elements. When the line pipe segments are welded, the region next to the fusion zone experiences rapid heating and subsequent rapid cooling, creating a heat-affected zone (HAZ). The microstructure and, thus, the mechanical properties of the HAZ may be different from that of the as-rolled steel and may have a detrimental effect on pipeline integrity. The area of the HAZ closest to the fusion boundary, referred to as the coarse-grain heat-affect…
has type: Thesis/Dissertation
date issued: 2023-05
is shown at: 10.14288/1.0422977
language: eng
degree discipline: Materials Engineering
provider: Vancouver : University of British Columbia Library
publisher: University of British Columbia
rights: Attribution-NonCommercial-NoDerivatives 4.0 International
rights URI: http://creativecommons.org/licenses/by-nc-nd/4.0/
scholar level: Graduate
contributor: Militzer, Matthias
type: Text
identifier URI: http://hdl.handle.net/2429/83581