Cast Iron: A Historical and Green Material Worthy of Continuous Research

Throughout history, cast iron has been unique amongst metallic materials. No other metal can boast such a long history, together with such a wide diversity of variants, properties, and applications. Arguably, no other material can claim to have such complexity. While the cast iron foundry produces myriad components, researchers and engineers have humbly ensured the continued development of this sophisticated material. We control this process not with furnaces and wirefeeders, but with knowledge. This knowledge enables the creation of a material with a unique combination of design flexibility, mechanical properties, wear resistance, recyclability, low life cycle energy consumption, and low cost. And it will be with the continued pursuit of understanding and knowledge that tomorrow’s researchers and engineers will ensure the continued growth of new material variants, with improved material properties and new applications that make the world a better place. Cast iron: thousands of years of development and progress behind us; thousands of fascinating mysteries and opportunities ahead of us.

Cast iron; History; Market share

Cast iron is an easy-to-shape material whose properties have evolved over the years in line with improvements in the technical and scientific fields. As of 2018, the various forms of cast iron represented 70% of the 110 million tons of total metal cast per year worldwide (10% for cast steel, 20% for aluminum and other alloys) (Census of Word Casting Production, 2019). Cast iron is a low-cost recyclable material with relatively low levels of pollution when compared to its present-day competitors. This is schematically illustrated in Figure 1, where so-called gray cast iron is compared with cast steels and aluminum alloys, in terms of price per MPa of yield strength vs. embodied energy (Figure 1a), and CO₂ footprint (Figure 1b). The latter two terms refer to energy used and CO₂ emitted, respectively, for the primary production, casting, and recycling of 1 kg of alloy.

Long before the dollar was established as a universal term of reference, and before aluminum had even been thought of, cast iron was already attractive for use in several applications in agriculture, domestic applications, and decoration. Cast iron is, in fact, a historic material that first appeared during the Iron Age, when the temperatures in furnaces became high enough for the processing of iron ore. It is therefore of first interest to summarize the evolution of cast iron materials, since its first inception up to the modern era, which we will do in the section to follow. As with other materials, over the last two centuries, several significant steps have been taken in the processing of cast iron, in casting technology, and in the cast iron itself. These are covered in the following sections.

Nowadays, cast iron consists of a family of materials, as depicted in Figure 2. Two main branches can be defined depending on the carbon-rich phase, which can be either cementite and other carbides, or graphite. Alloys within this former branch, also called white cast iron due to the color of their rupture surface, have high wear properties and good heat and corrosion resistance when alloyed but tend to be brittle. This branch, however, is a minor part of the cast iron family and most of the current production consists of gray (or graphitic) cast irons, in which the carbon-rich phase is graphite, giving a dark coloring to the rupture surfaces. The vast majority of these irons are based on Fe-C-Si alloys, and thus, can also be called silicon cast iron. This group of irons will be the focus of this paper. Ni-resist graphitic cast irons are heat and corrosion resistant, while very high-Si alloys are corrosion resistant. Behind the sorting in Figure 2 is a continuous evolution of cast iron alloys and their processing, as described in the section "Main Steps".

Figure 1 Gray cast iron compared with cast steel and aluminum alloy in terms of price and environmental impact. X-axes concern the ratio between price and Yield strength, while y-axes concern estimations of energy used (a) and equivalent CO₂ emissions (b) for the primary production, casting and recycling of one kg of alloy. Data from Granta Edupack (2020).

Figure 2 The cast iron family with the basic microstructures indicated. They are all obtained in the as-cast state, except those appearing in italics that are subjected to specific heat-treatment (after Elliott (1998) and Stefanescu (2018)).

    We continue to judge the iron foundry by its grey walls, despite the significant progress in cleaning up the dust. The real image should be the atoms, not the walls. Cast iron is the first composite material, and it remains one of the most versatile composites available today from a technical point of view, and one of the most fascinating from a scientific point of view. In the future, iron foundries will produce castings with different graphite shapes in different areas of the component to optimize specific properties where they are needed. While the iron foundry world may struggle for image, our present-day ability to control alloy additions to within 10 grams per ton will soon seem rudimentary. The real iron-age is just beginning and the next iron will build its own legend.

    F. Landgraf, Uni. Sao Paulo, and W. Menk kindly provided historical references.

Castro-Roman, M.J., Lacaze, J., Regordosa, A., Sertucha, J., del Campo-Castro, R., 2020. Revisiting Thermal Analysis of Hypereutectic Spheroidal Graphite Cast Irons. Metallurgical and Materials Transactions A, Volume 51(12), pp. 6373–6386

Census of Word Casting Production, 2019. Modern Casting. pp. 22–25

Dawson, S., 2001. A Brief History of … Foundry, Engine Technology

Dawson, S., 2003. Cast Iron Alloy and Method Making the Same, US Patent 6,613,274 B2

Derui, T., Haiping, L., 2010. An Illustrated History of Ancient Chinese Casting. In: Organization Committee of the 69^th World Foundry Congress, pp. 54–65

Eiken, J., Subasic, E., Lacaze, J., 2020. 3D Phase-Field Computations of Microsegregation in Nodular Cast Iron Compared to Experimental Data and CalPhad-based Scheil-Prediction. Materialia, Volume 9, https://doi.org/10.1016/j.mtla.2019.100538

Elliott, R., 1998. Cast Iron Technology. Butterworths, London, pp. 1–45

Franzen, D., Weiss, P., Pustal, B., Bührig-Polaczek, A., 2019. Influence of Aluminium on Silicon Microsegregation in Solution Strengthened Ductile Iron. Materials Science and Technology, Volume 35(6), pp. 687–694

Granta Edupack, 2020. Ansys/Granta Inc. Available Online at https://www.grantadesign.com/news_articles/introducing-granta-edupack-2020-refreshing-materials-education/

Javaid, A., Loper, C.R., 1995. Quality Control of Heavy-Section Ductile Cast Irons. AFS Trans, Volume 103, pp. 119–134

Jhaveri, K., Lewis, G.M., Sullivan, J.L., Keoleian, G.A., 2018. Life Cycle Assessment of Thin-Wall Ductile Cast Iron for Automotive Lightweighting Applications. Sustainable Materials and Technologies, Volume 15, pp. 1–8

Jolly, M.R., Salonitis, K., 2017. Primary Manufacturing, Engine Production and on-the-road CO₂: How can the Automotive Industry Best Contribute to Environmental Sustainability? In: Vienna motor symposium

Karsten, C.J.B., 1820, French translation by F.J. Culmann, 1820: Manuel de la métallurgie du fer, tome 2, Available Online at https://gallica.bnf.fr/ark:/12148/bpt6k98189063/f142.image.r=silice

Kweon, E.S., Roh, D.H., Kim, S.B., Stefanescu, D.M., 2020. Computational Modelling of Shrinkage Porosity Formation in Spheroidal Graphite Iron: A Proof of Concept and Experimental Validation. International Journal of Metalcasting, Volume 14, pp. 601–609

Lacaze, J., Dezellus, O., 2021. Surface Tension, Interfacial Segregation and Graphite Shape in Cast Irons. Metallurgical and Materials Transactions B, Available Online at https://doi.org/10.1007/s11663-021-02352-x

Lacaze, J., Sertucha J., Castro-Roman, M.J., 2020. From Atom Scale to Casting: A Contemporary Monograph on Cast Irons Microstructure. Unspecified, Available Online at https://oatao.univ-toulouse.fr/26869/

Le Coze, J., 2000. Purification of Iron and Steels, A Continuous Effort from 2000 BC to AD 2000. Materials Transactions JIM, Volume 41, pp. 219–232

Le Coze, J., 2017. Récits sidérurgiques d'hier et d'aujourd'hui. Fers, Fontes, Aciers: 4000 ans d'affinage et de purification. EDP Sciences

Lekakh, S., 1998. Effect of Non-metallic Inclusions on Solidification of Inoculated Spheroidal Graphite Iron. International Journal of Metalcasting, Volume 13(2), pp. 129–138

Lekakh, S., Richards, V., Peaslee, K., 2009. Thermo-Chemistry of Non-Metallic Inclusions in Ductile Iron. International Journal of Metalcasting, Volume 3(4), pp. 25–37

Lesoult, G., 2009. Microporosity in Cast Alloys: Simple Considerations on its Formation. International Journal of Cast Metals Research, Volume 22, pp. 1–4

Lesoult, G., Bellocci, R., Grandpierre, M., 1984. Les fontes à Pont-à-Mousson, CR PAM (Pont-à-Mousson)

Loper, C.R., 1998. Inoculation of Cast Iron–Summary of Current Understanding. AFS Trans. Volume 106, pp. 523–528

Metalcasting Forecast and Trends, 2019. AFS, Schaumburg

Mitterpach, J., Hroncov, E., Ladomerský, J., Balco, K., 2017. Environmental Evaluation of Grey Cast Iron Via Life Cycle Assessment, Journal of Cleaner Production, Volume 148, https://doi.org/10.1016/j.jclepro.2017.02.023

Muhmond, H.M., Fredriksson, H., 2015. Graphite Growth Morphologies in High Al Cast Iron. In: Advances in the Science and Engineering of Casting Solidification, pp. 323–330

Nechtelberger, E., Puhr, H., von Nesselrode, J.B., Nakayasu, A., 1982. Cast Iron with Vermicular Graphite – State of the Art. Development, Production, Properties, Applications, International Foundry Congress, CIATF, Volume 49(1), pp. 1–39

Robion-Brunner, C., 2018. L'Afrique des métaux, in L'Afrique ancienne, de l'Acacus au Zimbabwe, 20000 avant notre ère – XVIIème siècle, edited by F.X. Fauvelle (Belin, Paris, 2018), pp. 519–543

Salonitis, K., Jolly, M., Pagone, E., Papanikolaou, M., 2019. Life-Cycle and Energy Assessment of Automotive Component Manufacturing: The Dilemma Between Aluminum and Cast Iron. Energies, Volume 12(13), pp. 2557–2580

Santos, I.A.D., 2021. Rendas de ferro: uma doação pela memória civilizatória brasileira (Iron lace: a donation by the Brazilian Civilizing Memory). In: Proceedings of the São Paulo Museum: History and Material Culture, Volume 29, pp. 1–26

Sawyer, J.C., Wallace, J.F., Hallerberg, W.L., 1968. Effects and Neutralization of Trace Elements in Gray, Ductile and Malleable Iron. AFS Trans. Volume 76(part 1: 2-20 and part 2), pp. 21–32

Skaland, T., Grong, Ø., Grong, T., 1993. A Model for the Graphite Formation. Metallurgical and Materials Transactions A, Volume 24, pp. 2321–2345

Sintercast. Microstructure and Porosity Control, SinterCast Technical Description, https://www.sintercast.com/library/technical-papers-english/

Stefana, E., Cocca, P., Marciano, F., Rossi, D., Tomasoni, G., 2019. A Review of Energy and Environmental Management Practices in Cast Iron Foundries to Increase Sustainability. Sustainability, Volume 11(24), pp. 7245–7263

Stefanescu, D.M., 2018. A History of Cast Iron. ASM Handbook, Volume 1A, Cast Iron Science Technology, ASM International, pp. 3–11

Stefanescu, D.M., 2019. The Meritocratic Ascendance of Cast Iron: From Magic to Virtual Cast Iron, International Journal of Metalcastin, Volume 13, pp. 726–752

Subramanian, S.V., Kay, D.A.R., Purdy, G.R., 1982. Compacted Graphite Morphology Control, American Foundrymen's Society, Volume 90, pp. 582–603

Wittmoser, A., 1959. Ein halbes Jahrhundert Giessereitechnik in Deutschland. Giesserei, Volume 22, pp. 630–639