ASTM A247:16 pdf download

ASTM A247:16 pdf download.Standard Test Method for Evaluating the Microstructure of Graphite in lron Castings.
8. Classification of Graphite Distribution Using Chart
8. 1 The graphite distribution chart (Fig. 2) is useful principally in rating flake graphite, Type VII, distributions in gray cast iron. Graphite in malleable iron may occur in a nonrandom distribution pattern which the distributions B to E may be used to describe.
9. Classification of Graphite Size by Chart
9.1 This method categorizes the graphite particles by size into eight classes. Figs. 3-5 show size classes for flake graphite and nodular graphite to facilitate comparisons. The maximum dimension of the graphite particles for the various size classes are listed in Table I.
9.2 For direct comparison with the size classes in Figs. 3-5, the specimen to be evaluated shall he captured at the magnification of exactly lOOx. Usually visual comparison with the chart is adequate to define the size class. Where a mixture of one or more sizes occurs in the same sample, the sizes may he reported as percentages of the total graphite area represented by the sizes involved. It is a common practice in malleable irons to use nodule count per unit area instead of a comparison chart as given here. Nodule count, with known free carbon content, is a measure of calculated average nodule uea.
10. Nodularity
10.1 Nodularity (Fig. 6 and Fig. 7) is expressed by counting the nodular particles and reporting the results as a percentage of the total amount of graphite present in the microstructure. Ductile irons typically exhibit a nodularity between 80 to 100 %, gray irons a nodularily of
100 %, and compacted graphiLe irons a nodularity of 0 to 20 %. Nodularity should be assessed by evaluating more than one field of view. The final report should state the number of fields of view or area of the sample evaluated. The location of the measurement should be agreed upon between the manufacturer and purchaser.
11. Nodule Count
11 . I Nodule count is expressed as the number of graphite nodules/mm2 and is performed at a magnification of 1 OOx. Generally, high nodule count indicates good metallurgical quality, but there is an optimum range of nodule count for each section size of casting, and nodule counts in excess of this range may result in a degradation of properties. Nodule count should be established between the manufacturer and the purchaser. Figs. 8-10 compare the nodule counts of ductile iron at 100 % nodularity, 90 % nodularity, and 80 % nodularity. respectively.