On the Representativeness of Automated SEM/EDS Analyses for Inclusion Characterisation with Special Regard to the Measured Sample Area

Abstract

The cleanness of steel has emerged to an important quality criterion for a wide field of special applications. In order to ensure the reliable characterisation of non-metallic inclusions, the constant optimisation of current analysing methods is essential. The present study focuses on the automated SEM/EDS analysis, especially determining the influence of the analysed sample area on the obtained particle diameters and size distributions of non-metallic inclusions. Besides the experimental analysis of different area sizes, a model was formulated to estimate the error of area ratio as a function of inclusion content. For the assumed conditions, an area range combining a sufficient and significant area size with a feasible time effort is defined. The model also evaluates the significance of the results for the maximum and medium particle diameter gained out of the measurements. Moreover, the truncation of the data -resulting from an experimental analysing limit -and its consequences are discussed. The results underline the potential of this analysing method for inclusion characterisation but also demonstrate the limitations especially regarding the maximum particle diameter. This work contributes to a better understanding in terms of representativeness of automated SEM/EDS analysis and provides important information for further practical analyses.

Modeling of manganese sulfide formation during the solidification of steel

“…After the aforementioned sample preparation process, the inclusions in the samples are measured using automated SEM/EDS analysis. This method has been widely applied to investigate the steel cleanness [40][41][42]. These measurements employed a Scanning Electron Microscope (SEM) (ZEISS Ultra55) equipped with an Energy Dispersive X-ray Spectrometer (EDS) (Oxford Instruments).…”

Assessment of inclusion analysis via manual and automated SEM and total oxygen content of steel

“…One of the major limitations of the method is related to the representative area of the sample. Due to the combination of low inclusion occurrence in clean steel and the limited volume of the sample for cleanliness assessment, the meaning of the results is heavily dependent on the size of the area analyzed [13,25]. Another limiting factor is the size of the inclusion; in general, the larger the particle the smaller the steel matrix around the inclusion [8,11,14].…”

“…There are a variety of techniques that can be used industrially to determine the inclusion content of steel. However, it is important to consider the size of inclusions, time needed for inspection and the volume of the material to be analyzed [12][13][14]. According to Hénault [12], Fig.…”

“…Methods based on sample volumes, for inclusions larger than 20 m, detect inclusions that can cause potentially catastrophic effects during manufacturing processes or at the beginning of the life cycle of a steel part. Despite the limitation of assuming the behavior of a homogeneous heat, due to the small sample size [12], statistical methods aid in the treatment of data so that these better correspond to the reality of the entire heat [13].…”

Modeling of Inclusion Formation during the Solidification of Steel

“…[25][26][27][28] Based on the automated SEM/EDS analysis, inclusions are detected due to the material contrast differences in the backscattered electron (BSE) image. Usually, non-metallic inclusions are displayed as darker compared to the steel matrix.…”