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Ductile iron nodularity is of critical importance to its quality, but nodularity determination by metallographic analysis can be problematic. The widespread practice of estimating nodularity via comparator chart is highly subjective and prone to unacceptably high variation. An improvement over visual metallographic estimates is digital image analysis (IA) by which subjectivity can be greatly reduced, but the more reliable results obtained from IA are time-consuming and difficult to implement in a production environment. For this paper, the use of ultrasonic velocity testing via a standard coupon was evaluated as a possibly more reliable technique for determining front-end (real time) nodularity. Major results are presented herein along with details necessary for implementation of front-end ultrasonic nodularity determination using standard coupons as standard practice.

In the original article, the authors neglected to explicitly state prior to presentation of results for the as-cast water-quenched (ACWQ) plus tempered coupons from the November, 2012 (Y2012) fade campaign that all reported velocities were measured prior to tempering, as the tempering was necessary only to facilitate the sectioning of those coupons by conventional band saw for their metallographic analysis. The tempering of such ACWQ coupons at 482 °C for 48 h raises their velocities by ~ 100 m/s.