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Measurement techniques for the analysis of surface layers on grain oriented electrical steel. / Darren Poultney

Swansea University Author: Darren Poultney

Abstract

Fully processed, grain oriented electrical steel possesses a forsterite glass film and a phosphate-based insulation coating on both of its surfaces. The composition, quality and thickness of these layers, in addition to a preceding decarburisation oxide layer, are known to have a significant effect...

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Published: 2007
Institution: Swansea University
Degree level: Doctoral
Degree name: Ph.D
URI: https://cronfa.swan.ac.uk/Record/cronfa42469
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Abstract: Fully processed, grain oriented electrical steel possesses a forsterite glass film and a phosphate-based insulation coating on both of its surfaces. The composition, quality and thickness of these layers, in addition to a preceding decarburisation oxide layer, are known to have a significant effect on the properties of the material on which the final product is assessed. This includes physical properties, such as appearance, as well as the magnetic properties upon which the electrical steel is routinely graded. Due to their importance, methods of rapidly and accurately assessing these surface layers would provide great benefits as the characteristics could be monitored to ensure the optimum processing conditions are achieved. Unfortunately, it has previously been found that the complexity of the layers has made their analysis problematical, particularly in terms of accuracy and the time required for testing. A number of experimental techniques have been investigated to establish their potential for the analysis of the aforementioned surface layers, including Fourier Transform Infrared (FTIR), Electrochemical Potential (ECP), X-ray Photoelectron Spectroscopy (XPS) and Sputtered Neutral Mass Spectrometry (SNMS). Further methods were also used to determine characteristics of the coated material such as magnetostriction and magnetic loss, which provided an insight into the stressing capability of the material. As a result of these investigations: Combining a number of techniques resulted in a correlation between ECP profiles and the composition and / or morphology of the decarburisation oxide layer. A link has been established between the transmittance levels of the FTIR spectra and the thickness of the forsterite glass film layer. FTIR absorption bands have been linked to the constituents of the insulation coating. Further to the study into the feasibility of these methods, a number of the techniques were used to analyse material during the development of an alternative, chrome-free insulation coating, which has subsequently been adopted as the standard production coating for the grain oriented electrical steel produced at Orb Works.
Keywords: Materials science.
College: College of Engineering