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The study of steel inclusions with scanning probe microscopy techniques
2002 (English)Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

The topic of this thesis is studies of the formation of steel inclusions and experimental studies of inclusions in low-carbon steel. The presence of non-metallic inclusions can result in material failure during the metal forming process, or lead to a serious deterioration of the quality of the final product. Understanding the effects of inclusions during metal forming are therefore an important step towards predicting the behaviour of inclusions and minimising their consequences. Inclusions are alloying elements that have been added to the steelmaking process to reduce the amount of oxygen and carbon. Ideally, the inclusions float up to the surface and yield a slag above the liquid steel. However, as the steel solidifies some inclusions might get trapped in the steel. If the size and amount of inclusions are too large, material defects are developed. The atomic force microscope has been used, in combination with several other surface sensible methods, to study steel inclusions. The inclusions have been studied in detail with the atomic force microscope (AFM), down to an atomic scale, to determine their interaction with the surrounding matrix. Experiments have also been done with the scanning tunneling microscope (STM). Moreover, another setup to measure the current between a conducting AFM tip and the sample has been designed and partially implemented. This method is often devoted scanning spreading resistance microscopy (SSRM). The aim has been to measure local electrical properties and trace the composition of the inclusions. The high-resolution scanning probe techniques, in combination with other measurements, was shown to give new valuable insights to understand the effects of inclusions during metal forming. It was found that the aluminium oxide inclusions have a void to the surrounding matrix. At some positions, barriers were found towards the surrounding, this was probably due to imperfections in the ferrite matrix. Manganese oxide inclusions are fragile. As the steel with manganese oxide inclusions is worked on, micro cracks in the final product possibly appears. The holes in the manganese oxide clusters verify such polishing effects.

Place, publisher, year, edition, pages
Keyword [en]
Technology, Scanning probe microscopy, SPM, STM, Scanning Tunneling, Microscopy, AFM, Atomic Force Microscopy, Steel, Inclusions
Keyword [sv]
URN: urn:nbn:se:ltu:diva-51695ISRN: LTU-EX--02/344--SELocal ID: 8e4e068c-a6a3-4f90-ac1a-fdca9b55769eOAI: diva2:1025059
Subject / course
Student thesis, at least 30 credits
Educational program
Engineering Physics, master's level
Validerat; 20101217 (root)Available from: 2016-10-04 Created: 2016-10-04Bibliographically approved

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