Microstructural optimization of unalloyed ductile cast irons with a ferritic matrix used in the manufacture of wind turbine rotors

Authors

DOI:

https://doi.org/10.3989/revmetalm.118

Keywords:

Design of experiments, Ductile iron, Gray iron, Nodulizers, Pearlite, Quantitative metallography, Spheroidal graphite, Wind turbine rotor

Abstract


The aim of this work was the microstructural optimization of cast irons with nodular graphite for the manufacture of wind turbine hubs, paying preferential attention to the geometry and distribution of graphite spheroids to ensure the required mechanical properties for this application. The target was pursued based upon microstructure-properties correlation, in an environment of great competitiveness and exigency marked by current international standards. The methodology followed consisted of the generation of knowledge from tailor-made industrial castings, followed by the analysis of their microstructures, in order to extract valuable conclusions for the production process through the use of statistical analysis. The approach method employed was a Fractional Design of Experiments (DOE) with 7 factors, 16 experiments and resolution IV. The samples from each experiment were cubes of identical geometry, and designed to match a surface-to-volume module equal to 4 cm (1.57 in) found as the highest values in real hubs of 3 MW power wind turbines. It is concluded that the use of nodulizers with traces of lanthanum favour the reduction of the volume fraction of pearlite, although La has proved not to promote the spherical shape of primary graphite. The negative effect of pre-inoculants containing SiC on the spheroidal morphology of graphite has also been verified, and also that low-Mn bearing scrap favours graphite formation and the reduction of the volume fraction of pearlite, in spite of being a carbide forming element. The whitening effect of Mn was minimized with low carbon equivalent melts.

Downloads

Download data is not yet available.

References

Asenjo, I., Larrañaga, P., Garay, J., Sertucha, J. (2011). Influence of the chemical composition of different steel scraps on the mechanical properties of ductile iron. Rev. Metal. 47 (4), 307–318.

Asensio-Lozano, J., Álvarez-Antolín, J.F. (2007). Application of Fractional Design of Experiments to the Optimisation of the Hardness and Microstructure of Duplex Cast Rolls. Prakt. Metallogr.-Pract. Metallogr. 44 (11), 503–522. https://doi.org/10.3139/147.100360

Asensio-Lozano, J., Álvarez-Antolín, J.F., Vander Voort, G.F. (2008). Identification and quantification of active manufacturing factors for graphite formation in centrifugally cast Nihard cast irons. J. Mater. Process. Tech. 206 (1–3), 202–215. https://doi.org/10.1016/j.jmatprotec.2007.12.015

ASTM E2567-11 (2011). Standard Test Method for Determining Nodularity And Nodule Count In Ductile Iron Using Image Analysis, ASTM International, West Conshohocken, PA.

Bockus, S., Zaldarys, G. (2010). Production of Ductile Iron Castings with Different Matrix Structure. Mater. Sci.-Medzg. 16 (4), 307–310. http://internet.ktu.lt/lt/mokslas/zurnalai/ medz/pdf/medz0-103/05%20Metals...(pp.307-310).pdf.

Box, G., Hunter, J., Hunter, W. (2005). Statistics for Experimenters. John Wiley & Sons, Inc., New York, USA. PMCid:PMC1273458

Geier, G.F., Bauer, W., McKay, B.J., Schumacher, P. (2005). Microstructure transition from lamellar to compacted graphite using different modification agents. Mat. Sci. Eng. A-Struct. 413–414, 339–345. https://doi.org/10.1016/j.msea.2005.08.159

Guzel, E., Yuksel, C., Bayrak, Y., Sen, O., Ekerim, A. (2014). Effect of section thickness on the microstructure and hardness of ductile cast iron. Mater. Test. 56 (4), 285–288. https://doi.org/10.3139/120.110558

Han, S.Y., Sohn, S.S., Shin, S.Y., Lee, S., Suh, Y.C. (2013). In Situ fracture observation and fracture toughness analysis of pearlitic graphite cast irons with different nodularity. Met. Mater. Int. 19 (4), 673–682. https://doi.org/10.1007/s12540-013-4006-6

Johnson, R.A. (1997). Probabilidad y Estadística para Ingenieros. Prentice-Hall Hispanoamérica, México.

Lacaze, J., Sertucha, J., Larra-aga, P., Suárez, R. (2016). Statistical study to determine the effect of carbon, silicon, nickel and other alloying elements on the mechanical properties of as-cast ferritic ductile irons. Rev. Metal. 52 (2), e070. https://doi.org/10.3989/revmetalm.070

Magenreuter, T., Velichko, A., Mücklich, F. (2008). The dependence of the shape parameters roundness and compactness of various graphite morphologies on magnification. Prakt. Metallogr.- Pract. Metallogr. 45 (2), 53–71. https://doi.org/10.3139/147.100371

Montgomery, D.C., Runger, G.C. (1996). Probabilidad y Estadística aplicada a la Ingeniería. Mc Graw-Hill, México.

Mottitschka, T., Pusch, G., Biermann, H., Zybell, L., Kuna, M. (2012). Influence of graphite spherical size on fatigue behaviour and fracture toughness of ductile cast iron EN-GJS-400-18LT. Int. J. Mater. Res. 103 (1), 87–96. https://doi.org/10.3139/146.110636

Onsoien, M.I., Skaland, T., Grong, O. (1999). Mechanisms of graphite formation in ductile cast iron containing cerium and lanthanum. Int. J. Cast. Metal. Res. 11 (5), 319–324. https://doi.org/10.1080/13640461.1999.11819293

Onsoien, M.I., Skaland, T. (2001). Preconditioning of Gray Iron Melts using Ferrosilicon or Silicon Carbide. 105th Casting Congress, American Foundry Society (AFS), Dallas, USA.

Pan, Y.N., Lin, C.C., Chang, R.M. (2012). Assessments of relationship between microstructures and mechanical properties for heavy section ductile cast irons. Int. J. Mater. Res. 25 (5), 301–306. https://doi.org/10.1179/1743133612Y.0000000027

Pedersen, K.M, Tiedje, N.S. (2008). Graphite nodule count and size distribution in thin-walled ductile cast iron. Mater. Charact. 59 (8), 1111–1121. https://doi.org/10.1016/j.matchar.2007.09.001

Pedersen, K.M., Tiedje, N.S. (2009). Influence of rare earths on shrinkage porosity in thin walled ductile cast iron. Int. J. Cast. Metal. Res. 22 (1–4), 302–305. https://doi.org/10.1179/136404609X367830

Prat, A., Tort-Martorell, X., Grima, P., Pozueta, L. (1997). Métodos estadísticos control y mejora de la calidad. Ediciones UPC, Barcelona, Espa-a.

Radzikowska, J.M. (2005). Effect of specimen preparation on evaluation of cast iron microstructures. Mater. Charact. 54 (4–5), 287–304. https://doi.org/10.1016/j.matchar.2004.08.019

Sheikh, M.A., Iqbal, J. (2007). Effect of lanthanum on nodule count and nodularity of ductile iron. J. Rare Earths 25 (5), 533–536. https://doi.org/10.1016/S1002-0721(07)60557-2

Shiraki, N., Watanabe, T., Kanno, T. (2015). Relationship between Fatigue Limit and Defect Size in Spheroidal Graphite Cast Iron with Different Graphite Spheroidization Ratios and Microstructures. Mater. Trans. 56 (12), 2010–2016. https://doi.org/10.2320/matertrans.F-M2015826

Shiraki, N., Usui, Y., Kanno, T. (2016). Effects of Number of Graphite Nodules on Fatigue Limit and Fracture Origins in Heavy Section Spheroidal Graphite Cast Iron. Mater. Trans. 57 (3), 379–384. https://doi.org/10.2320/matertrans.F-M2015841

Skjegstad, N.T., Skaland, T. (1996). Inoculation of Grey and Ductile Iron. Proceedings of Bombay Foundry Congress, Bombay, India, pp. 1–23.

Soivio, K., Elmquist, L. (2013). Influence of inoculation on shrinkage defects in spheroidal graphite cast iron. Int. J. Cast. Metal Res. 26 (4), 220–227. https://doi.org/10.1179/1743133613Y.0000000057

Published

2018-06-30

How to Cite

Asensio-Lozano, J., Álvarez-Antolín, J. F., & Álvarez-Pérez, C. H. (2018). Microstructural optimization of unalloyed ductile cast irons with a ferritic matrix used in the manufacture of wind turbine rotors. Revista De Metalurgia, 54(2), e118. https://doi.org/10.3989/revmetalm.118

Issue

Section

Articles

Most read articles by the same author(s)