SEDL / STP / STP1327-EB / STP12117S



Inclusion Ratings: Past, Present, and Future

Vander Voort, GF
Director, Buehler Ltd., Lake Bluff,IL


Pages: 14    Published: Jan 1998


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Source: STP1327-EB


Abstract

Chart-based techniques, such as ASTM E 45, have been used to rate inclusion types and content for more than half a century. Chart ratings are subject to considerable error, reproducibility among raters is poor, and they lack precision for today's steels with very low inclusion contents. Image analysis procedures, using ASTM E 1122, where the rating system has been modified to generate improved JK-chart ratings, are now being used widely. A new, alternate approach using stereological relationships for inclusion measurements is given by ASTM E 1245. In this method, the inclusions are separated by type (oxide vs. sulfide usually) and the volume fraction, number per unit area, average length, average area, and spacing are determined. E 1245 is easy to do by image analysis and is fast. In this paper, heats of 52100 bearing steel, made by different technologies, were rated using the current E 45/E 1122 method and by the method of the future, E 1245. The greater merit of the E 1245 method was demonstrated statistically by comparing the test results for the steels made by the different procedures.


Keywords:
automatic image analysis, bearing steels, nonmetallic inclusions, oxides, sulfides, stereology

Paper ID: STP12117S
Committee/Subcommittee: A01.28
DOI: 10.1520/STP12117S
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