Special Issue Paper
(Received 14 January 2016; accepted 25 April 2016)
Published Online: 22 December 2016
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Over the years, ASTM Committee E4 on metallography has conducted interlaboratory test programs to evaluate the precision and bias associated with measurements of microstructure using proposed and existing test methods. ASTM decided in the late 1970s that all test methods that generated numerical data must have a precision and bias section defining the repeatability and reproducibility of the method. Defining bias associated with a test method is difficult unless there is an absolute known value for the quantity being measured and this is not possible when microstructural features are being measured. This paper shows the results for an interlaboratory test using Method A, “worst-field” ratings of inclusions in steels using the original Plates I and III of ASTM E45, using Method C, a worst-field rating using Plate II; and, using Method D, a quantitative approach where every field is rated using Plates I and III. The results from nine people who were reported to be qualified, regular users of the method revealed consistent problems of misclassification of inclusion types and a wide range of severity ratings for each specimen. The test results using an image analyzer will be compared to that of the manual raters.
Vander Voort, G. F.
Struers Inc., Westlake, OH
Stock #: MPC20160002