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Simple identification of Al 2 O 3 and MgO·Al 2 O 3 spinel inclusions in steel using X‐ray‐excited optical luminescence
Author(s) -
Imashuku Susumu,
Wagatsuma Kazuaki
Publication year - 2018
Publication title -
x‐ray spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.447
H-Index - 45
eISSN - 1097-4539
pISSN - 0049-8246
DOI - 10.1002/xrs.2995
Subject(s) - spinel , luminescence , materials science , analytical chemistry (journal) , excited state , wavelength , argon , mineralogy , metallurgy , optoelectronics , chemistry , atomic physics , physics , chromatography , organic chemistry
Nonmetallic inclusions in steel cause problems in steel products and steel production. In particular, an analysis of Al 2 O 3 and MgO·Al 2 O 3 spinel inclusions is important since they are one of the most harmful inclusions. A rapid and simple analysis of nonmetallic inclusions is required as the conventional analytical methods for nonmetallic inclusions are time‐consuming. In this study, we propose a simple method to identify Al 2 O 3 and MgO·Al 2 O 3 spinel inclusions in steels. X‐ray‐excited optical luminescence (XEOL) analysis was selected as a promising method because it can rapidly identify sizes, shapes, and compositions of nonmetallic inclusions and can be performed in air. A model steel sample prepared by heating a mixture of Fe, Al, and MgO powders at 1550°C in argon atmosphere was used. XEOL images of the model steel sample showed that Al 2 O 3 inclusions emitted blue and red luminescences. Using a filter attached to the camera, blocking light in the wavelength region above 650 nm, only the blue luminescence of the Al 2 O 3 inclusions was observed. This was implemented as the luminescences of the Al 2 O 3 inclusions appeared in both blue and red regions at wavelengths of 350, 485, 695, and 750 nm; consequently, the luminescences at 695 nm and 750 nm were blocked by the filter. In contrast, MgO·Al 2 O 3 spinel inclusions emitted green luminescence (peak at 520 nm), unaffected by the filter. This indicates that we can simply identify Al 2 O 3 and MgO·Al 2 O 3 spinel inclusions by an XEOL image in the wavelength range of 420–650 nm.