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dc.contributor.advisorSpeer, J. G.
dc.contributor.authorSun, Jun
dc.date.accessioned2007-01-03T04:52:22Z
dc.date.accessioned2022-02-09T08:39:21Z
dc.date.available2007-01-03T04:52:22Z
dc.date.available2022-02-09T08:39:21Z
dc.date.issued2013
dc.identifierT 7208
dc.identifier.urihttps://hdl.handle.net/11124/78725
dc.description2013 Spring.
dc.descriptionIncludes illustrations.
dc.descriptionIncludes bibliographical references (pages 75-80).
dc.description.abstractSome newer hot rolled high strength low alloy (HSLA) steels with a single phase ferrite matrix have obtained substantial strengthening from nanoscale precipitation. These HSLA are reported to have a good combination of strength, ductility and hole-expansion ability. In the current work, Gleeble® 3500 torsion testing was employed to simulate the hot rolling process with varying run-out table cooling rates and coiling temperatures on five microalloyed steels with additions of Ti, Nb, Mo, Cr and V, to investigate the effects of microalloy additions and processing conditions on microstructures as well as mechanical properties. Subsized tensile specimens obtained from as-twisted torsion samples were used to evaluate mechanical properties. The precipitation states of the five steels with different processing conditions were characterized using extraction replica TEM. Comparison of microstructures and mechanical properties was discussed. Characterization of the microstructure via light optical microscopy showed the matrix microstructure was mainly influenced by coiling temperature, which indicates that the transformation from austenite to ferrite occurred during the coiling period. A higher Ti content was shown to reduce the second constituent fractions. Investigation of carbon extraction replica specimens via TEM revealed the presence of nanoscale precipitation. Extensive nanoscale precipitation was observed in most of the specimens having a polygonal ferrite matrix, while in the granular bainite/ferrite microstructure at lower temperatures, fewer microalloy carbides were present. The specimens with polygonal ferrite had similar or higher yield strength than the specimens with granular bainite microstructure, which suggests the effectiveness of precipitation strengthening from extensive nanoscale precipitates. In the Nb-Mo steel, more significant strengthening due to grain refinement was evident. Yield strength values were less than reported for JFE's "NANOHITEN®" steel in specimens with similar microstructure (polygonal ferrite matrix with extensive nanoscale precipitation).
dc.format.mediumborn digital
dc.format.mediummasters theses
dc.languageEnglish
dc.language.isoeng
dc.publisherColorado School of Mines. Arthur Lakes Library
dc.relation.ispartof2013 - Mines Theses & Dissertations
dc.rightsCopyright of the original work is retained by the author.
dc.subject.lcshSteel, High strength
dc.subject.lcshMicroalloying
dc.subject.lcshMicrostructure
dc.subject.lcshPrecipitation (Chemistry)
dc.subject.lcshMetals -- Mechanical properties
dc.subject.lcshTorsion -- Testing
dc.titleNanoscale precipitation in hot rolled sheet steel
dc.typeText
dc.contributor.committeememberMatlock, David K.
dc.contributor.committeememberThompson, S. W. (Steven W.)
dc.contributor.committeememberVan Tyne, C. J.
thesis.degree.nameMaster of Science (M.S.)
thesis.degree.levelMasters
thesis.degree.disciplineMetallurgical and Materials Engineering
thesis.degree.grantorColorado School of Mines


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