Ductile Iron Front-End Ultrasonic Nodularity Determination Using Standard Coupons

  • James CreeEmail author
  • Mike RoblesJr.
  • Adam Hoover
  • Nicholas Thornberry
  • Shana Beckley


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.


metallography ultrasonic velocity testing nodularity testing image analysis 



The authors give special thanks to the following individuals for their invaluable assistance in getting front-end ultrasonic nodularity determination using standard coupons (FEUNDUSC) implemented as standard procedure for the real-time quantification of ductile iron nodularity at AAM Casting-New Castle: (1) To Marc Henry and Joe Marie of Team NDT, LLC, for their mentoring on the basic physics and fundamentals of ultrasonic testing. (2) To Clarke Steigerwald, Adam Babarik, Neethu Varghese, Nikhil Naik and Ricardo Jimenez of Midwest Information Systems, Inc., for their clear presentation of the capabilities of the PAX-it!® software for digital image analysis of cast irons and further tutoring on navigation of the software whenever it was needed. (3) To David Coulston of LECO Corporation for sharing his practical experience in using the PAX-it!® software for the digital image analysis of cast irons. (4) To Skip Weaver of Heraeus Electro-Nite Company for loaning thermal analysis equipment and donating ‘plain’ thermal analysis cups for the November 2009 fade campaign. (5) To Tom Kasee of Sawbrook Steel Castings for providing us with the plain hypoeutectoid carbon steel plates devoid of graphite nodules. Those plates of both ‘low’-carbon (more ferrite) and ‘high’-carbon (more pearlite) contents were used in evaluating the effect of ferrite/pearlite contents on ultrasonic velocity in the absence of graphite nodules. (6) To John Finley and Jim Miller of ASQ Section No. 0904 for their generous review and commentary on much of the statistical analysis presented in this paper. (7) To Nicholas Thornberry and Shana Beckley for their voluminous processing of highly detailed metallography reports that were necessary for drawing meaningful and statistically significant conclusions regarding correlations between metallography metrics and ultrasonic velocity. (8) To all AAM Casting-New Castle Melt Department personnel who provided support and assistance in the casting of all coupons used in the development work. (9) To Gary Bray, Herb McGhee, Craig Ead, Barry Mosier and others for their support and assistance with the FEUNDUSC development work in addition to their primary laboratory responsibilities for production support. (10) To Joe Sullivan and Jerry Krupp for doing comparative MAGMASOFT® solidification simulations of conventional metallographic micro-lugs and FEUNDUSC coupons. (11) To Tim Davis for his support in enabling compatible implementation of the FEUNDUSC testing procedure with AAM Casting-New Castle’s internal computer systems and his further assistance in facilitating data analysis.

Supplementary material

40962_2019_322_MOESM1_ESM.pdf (99 kb)
Appendix 1. Effects of Varying Cu and Mn on ‘Fresh’ and ‘Aged’ Ultrasonic Velocities, presented at AFS Committee 5-R Meeting on 09/18/13 (PDF 98 kb)
40962_2019_322_MOESM2_ESM.pdf (456 kb)
Appendix 2. AAM-New Castle’s DIS Autumn 2015 Abridged Meeting Info (PDF 455 kb)
40962_2019_322_MOESM3_ESM.pdf (179 kb)
Appendix 3. Ductile Iron Aging Effects Following Supercritical (Re-Austenitization) Heat Treatments (PDF 179 kb)
40962_2019_322_MOESM4_ESM.pdf (729 kb)
Appendix 4. Effects of Thermal History and Image Analysis Filters on Ductile Iron Metallography (PDF 729 kb)
40962_2019_322_MOESM5_ESM.pdf (141 kb)
Appendix 5. Effects of Casting Cooling Rates and Supercritical HT’s on Ductile Iron Ultrasonic Velocity (PDF 141 kb)
40962_2019_322_MOESM6_ESM.pdf (902 kb)
Appendix 6. Effects of Carbon Content on the Ultrasonic Velocity and Microstructure of Hypoeutectoid Carbon Steels (PDF 901 kb)


  1. 1.
    J.W. Cree, Appendix B of Ductile Iron Society Report No. 42 (October, 2008 Version) Ultrasonic velocity testing of nodularity in coupons (2008)Google Scholar
  2. 2.
    AFS Committee 12-K, Microscopic test coupons. AFS Trans. Article No. 60–108, pp. 655–656Google Scholar
  3. 3.
    ASTM A247-17, ASTM Committee A04 and its subcommittee A04-21 on testing. Standard test method for evaluating the microstructure of graphite in iron castingsGoogle Scholar
  4. 4.
    I. Riposan, M. Chisamera, S. Stan, Control of surface graphite degeneration in ductile iron for windmill applications. Int. J. Metalcast. 7, 9–20 (2013)CrossRefGoogle Scholar
  5. 5.
    N. Ivan, I. Riposan, M. Chisamera, Mold coatings to reduce graphite degeneration in the surface layer of ductile iron castings. Int. J. Metalcast. 6, 61–70 (2012)CrossRefGoogle Scholar
  6. 6.
    S. Boonmee, D.M. Stefanescu, Casting skin management in compacted graphite iron part II: mechanism of casting skin formation. AFS Trans. 13–1392, 449–459 (2013)Google Scholar
  7. 7.
    D.R. Askeland, F. Farinez, Factors affecting the formation of secondary graphite in quenched and tempered ductile iron. AFS Trans. 79–72, 99–106 (1979)Google Scholar
  8. 8.
    R.C. Voigt, C.R. Loper Jr., Secondary graphitization in quenched and tempered ductile cast iron. AFS Trans. 82–95, 239–255 (1982)Google Scholar
  9. 9.
    AFS Committee 5-J, Minimizing retained austenite in heat treated cast iron. Modern Casting, p. 50 (1995)Google Scholar
  10. 10.
    Results of AAM Casting-New Castle Research Presented at AFS Committee 5-R Meeting on 05/04/11Google Scholar
  11. 11.
    Results of AAM Casting-New Castle Research Presented at AFS Committee 5-R Meeting on 09/18/13Google Scholar
  12. 12.
    Results of AAM Casting-New Castle Research Presented at AFS Committee 5-R Meeting on 05/16/12Google Scholar
  13. 13.
    Results of AAM Casting-New Castle Research Presented at AFS Committee 5-R Meeting on 09/19/12Google Scholar
  14. 14.
    Results of AAM Casting-New Castle Research Presented at AFS Committee 5-R Meeting on 01/23/13Google Scholar
  15. 15.
    ASTM E2567-16a, ASTM committee E04 and its subcommittee E04-14 on quantitative metallography. Standard test method for determining nodularity and nodule count in ductile iron using image analysisGoogle Scholar
  16. 16.
    D.B. Coulston, LECO Corp., IA metallographic analyses conducted on ASTM A536-84(2014) Keel Block Test Bars from November, 2009 Fade Campaign for Correlation to Elastic Moduli (2009)Google Scholar
  17. 17.
    Results of AAM Casting-New Castle Research Presented to DIS Image Analysis Committee for Presentation at DIS Autumn, 2015 Meeting on 10/29/15Google Scholar
  18. 18.
    Results of AAM Casting-New Castle Research Presented at AFS Committee 5-R Meeting on 01/29/14Google Scholar
  19. 19.
    J.W. Cree, Gray iron aging effects as measured using NDT and microstructural analysis. Int. J. Metalcast. 11, 696–728 (2017). CrossRefGoogle Scholar
  20. 20.
    K.E. Metzloff, C.R. Loper, Jr., Effect of nodularity, heat treatment and copper on the elastic modulus of ductile and compacted graphite irons. AFS Transactions, 01-088Google Scholar
  21. 21.
    A. Alagarsamy, Sound advice for nodularity testing. Mod. Cast. 95(7), 31–34 (2005)Google Scholar
  22. 22.
    H.E. Henderson, The effect of heat treatment on ultrasonic velocity of ductile iron castings. Iron Worker 40, 23–25 (1976)Google Scholar
  23. 23.
    A.G. Fuller, P.J. Emerson, G.F. Sergeant, A report on the effect upon mechanical properties of variation in graphite form in irons having varying amounts of ferrite and pearlite in the matrix structure and the use of nondestructive test in the assessments of mechanical properties of such irons. AFS Trans. 88, 21–50 (1980)Google Scholar
  24. 24.
    S.-C. Lee, J.-M. Suen, Ultrasonic nondestructive evaluation of matrix structures and nodularity in cast irons. Metall. Trans. A 20, 2399–2407 (1989)CrossRefGoogle Scholar
  25. 25.
    H. Li, R.D. Griffin, C.E. Bates, Gray iron property measurements using ultrasonic techniques. AFS Trans. 113, 687–697 (2005)Google Scholar

Copyright information

© American Foundry Society 2019

Authors and Affiliations

  1. 1.American Axle and Manufacturing Casting DivisionNew CastleUSA

Personalised recommendations