Cast iron: the types and development of an evolving material

Cast iron: a fascinating material, ancient but still current and fundamental to modern life. Without the cast iron castings that leave foundries, many of the finished products that are part of our daily life, and which are also the result of various industrial activities, would not be made. A journey to discover this metal can therefore offer many points for reflection, no matter whether you stop and think about its properties, types and applications, or consider the new challenges that the market constantly proposes in terms of performance and sustainability.

The strong points of cast iron

Pig iron (ghisa di prima fusione in Italian) is a carbon-iron alloy that is used to make steel and is a raw material for iron foundries. Cast iron (ghisa di seconda fusione in Italian), which we produce in our foundries, is corrected with other elements and then used to make casts.

Cast iron and steel are both carbon-iron alloys; the difference, however, lies in the percentage of carbon they contain (cast iron contains more than 2% carbon, steel contains much less).

This is therefore cast iron’s first strong point. Even though they have the same mechanical characteristics, cast iron – in applications where it can be used – is about 10% lighter than steel thanks to its higher percentage of carbon. This, naturally, is a very important characteristic: just think about the relationship between material weight and energy efficiency. In the automotive sector, for example, where performance and consumption are essential characteristics, the lightness of cast iron is an unquestionable additional value.

Other strong points of cast iron are its low cost and its excellent castability. The latter derives from its chemical composition, which makes it particularly suitable for coating geometrically complex forms. The possibility that cast iron has of giving life to an infinite number of forms is enhanced at Fonderie di Montorso by the company’s ability to assemble very complex cores and offer a co-design service that follows clients through foundry process project optimisation.

Cast iron, however, is also sustainable: the melting process means that metal products at the end of their life can be used again and be returned to their initial condition. This makes it possible to insert cast iron into the recycled materials category and to consider foundries as a perfect example of circular economy.

Different types of cast iron

Cast iron can differ according to its chemical composition.

Grey cast iron is characterised by thin layers of graphite. Ductile cast iron (also called spheroidal graphite cast iron), on the other hand, takes its name from the form of the graphite, which in this case is not in thin layers but spheroidal. EN-GJS-400-18-LT spheroidal graphite cast iron is interesting because the selection of materials, the melting process and the cleanliness of the metal make it ideal for use in the automotive and hydraulics sectors.

Thanks to the recent acquisition of Fonderia Scaranello and the introduction of shell moulding, Fonderie di Montorso today also works with high alloy cast iron, Cr-Hard cast iron and compacted graphite iron, materials used to produce sealing rings for the automotive and construction sectors.

Cast iron: history and innovation

Tradition and innovation are a fundamental duo when talking about cast iron.

The first attempts to heat ferrous materials using charcoal in rudimentary forges date back to 3000 years ago, even if the development of cast iron is tied above all to the progressive refinement of man’s ability in the Middle Ages to build furnaces. To make cast iron, specific temperatures had to be reached….

In addition to the development of furnaces, the transformation in the 17th century of fossil carbon into coke, which has a higher heat capacity, was very important.

Even if cast iron is rooted in the distant past, few materials were able to develop as much over time. Constant improvements in its microstructural characteristics and production technologies ensure that it continues offering possibilities of development. Updated foundry processes and more automated melting plants that give real time data, which translate into process specifications when formalised, give products with increasingly higher operating performances.

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