The cast iron of Greenpipe gratings
Cast iron is a metal alloy composed primarily of iron and carbon, characterized by a carbon percentage between 2.06% and 6.67% (2.06% < C < 6.67%) and obtained by the reduction of iron ores using coke coal within blast furnaces (editor’s note: steels are metal alloys with a carbon content between 0.08% and 2.06%).
The production of cast iron in a blast furnace (pig iron)
A blast furnace is a vertical industrial structure used for the production of cast iron. Its walls are lined with refractory bricks and a cavity through which water flows to cool the structure.
The primary use is the production of cast iron, with by-products such as blast furnace gas and slag (blast furnace slag). The by-products are reused for heating the furnaces, while the slag is used in cement production.
After 6 to 8 hours, the pig iron is tapped, which is mainly used for steel production.
The production process of the material consists of three stages and can be briefly described as follows:
- Charging the blast furnace: iron ores, limestone, and coke are inserted from the top (throat) into the blast furnace. The coke produces heat and reacts with the air without melting.
- Reaction: preheated air is injected, burning the coke and generating CO gas which reduces the iron oxides, separating them.
- Melting and collection: The molten iron bonds with the carbon and descends into the hearth, separating from the waste—namely cast iron and slag—by gravity.
Foundry cast irons
The produced iron pigs are used to create steel or foundry cast irons for finished products. In the foundry, this process takes place in furnaces with scrap and additives, and the management of the melt determines the type of cast iron based on the form of the carbon (cementite or graphite).
The classification of foundry cast irons can be outlined as follows:
- White cast iron
- Malleable cast iron
- Grey cast iron (Graphite C) which can be of the lamellar or spheroidal type
White cast iron
White cast iron is formed by rapidly cooling the iron, combining the carbon with the iron into cementite, which makes it extremely hard and wear-resistant but brittle, suitable for components not subject to impact.
Malleable cast iron
Malleable cast iron is obtained through two distinct annealing processes (in an oxidizing environment for the white-heart type or a reducing environment for the black-heart type), which determine its properties and final applications.
It is often used to create agricultural tools.
Lamellar grey cast iron
Lamellar grey cast iron is obtained by increasing graphitizing elements such as silicon to create lamellar graphite, a structure that facilitates machining. This composition reduces tensile strength and is not weldable. It is used in components such as cylinder heads and engine blocks, valves, and fittings, thanks to its excellent vibration-damping capacity.
Spheroidal grey cast iron (also known as ductile or nodular iron)
Ductile iron is a material widely used in modern engineering thanks to a unique combination of mechanical properties. The secret of its performance lies in its microstructure, where the graphite appears in the form of compact “spheroids.” This spheroidal morphology does not interrupt the continuity of the metal matrix, eliminating weak points. This gives the material remarkable ductility and superior mechanical strength.
Its properties approach those of steel, far exceeding the brittleness of traditional cast iron. This enables it to withstand significant plastic deformation before failure.
It is the ideal choice for components subjected to heavy loads and impacts. In infrastructure, such as gratings for drainage channels and manhole covers, it is essential to ensure durability and safety.
Ductile iron offers an optimal balance between ease of production and the structural performance required by the most demanding engineering applications.
Greenpipe has been using ductile iron for its gratings for years, thus ensuring durability and resistance over time.
Our products
Gratings and Rails
Design gratings
Concrete channels with cast iron gratings
Self-supporting channels with cast iron gratings
Suitable for high load classes (D400 and F900), they are used in road and motorway networks, port and logistics terminals, and large infrastructures thanks to their very high compressive strength.