Konzept und Prozessoptimierung für die Herstellung bainitischer nahtloser Rohre mit speziellen Eigenschaften

Translated title of the contribution: Concept and process optimization for the production of bainitic seamless steel tubes with special features

Andreas Martin Weber

Research output: ThesisDoctoral Thesis

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Abstract

Due to the wide range of applicability the demand of seamless steel tubes will increase in the next years although the currently low price of oil-brent. This is primarily caused by the ambient conditions in the oil field industry even so the forcing requirements in the automotive industry. So the need for a better combination of strength and toughness and further for better resistance against hydrogen embrittlement continuous to rise. Present study shows investigations about eight individual designed melts with different heat treatments for as-quenched, Quenched & Tempered, carbide free and Quenched & Partitioning high strength morphologies. The influence of retained austenite and the transformation induced residual stress to the hydrogen embrittlement was worked out. It could be shown that strength up to 1800 MPa with total elongation close to 15 % are able to reach with mixed morphologies. Further it was found that mixed morphologies with martensitic and bainitic states show the best resistance against hydrogen embrittlement. It was found that the most important influence is set to the stability of the retained austenite against transformation to martensite and the release of hydrogen. Furthermore it could be shown that the PSE (Product of Strength and Elongation) reaches up to 18 GPa%. Therefore a carbon content level between 0.15 and 0.2 % leads to the best results. A detailed process analysis of the production route on the influences of advanced high strength morphologies shows capabilities and gives a ranking with focus of technological and economical aspects. It could be emphasized that the continuous cooling path offers a simple production route without additional reconstruction work and enables a homogeneous texture over the cross section of the steel tube. A complementary patent search shows that there is no overlapping with other trademarks and competitors.
Translated title of the contributionConcept and process optimization for the production of bainitic seamless steel tubes with special features
Original languageGerman
QualificationDr.mont.
Supervisors/Advisors
  • Leitner, Harald, Assessor B (external)
  • Buchmayr, Bruno, Assessor A (internal)
Publication statusPublished - 2016

Bibliographical note

embargoed until null

Keywords

  • carbide free bainite
  • seamless steel tube
  • hydrogen embrittlement
  • retained austenite

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