Cast Iron History – When Did It All Start?
Cast iron has been around for a very long time! In China, archaeologists have discovered cast iron artefacts that originate from the 5th century BC. Indeed, cast iron was invented in China. It was first cast in moulds to make weapons, farm equipment and cooking pots.
You may be surprised to learn that the Chinese also invented their own method of annealing by burning off some of the carbon to create a material with more tensile strength. And early examples of furnaces, dating back some 1000 years have been discovered in the Congo. In fact there are many early examples of cast iron items all over the world.
But it was in 19th-century England during the Industrial Revolution, when Abraham Darby developed a new method of smelting iron ore with coke, that cast iron began to be produced on a large scale. This new method of production meant that cast iron could be mass-produced cheaply and efficiently. Cast iron became widely used, and such was the demand for the product that many towns had their own foundries during this time.
The Casting Process Explained
Cast iron is made from pig iron. It is produced by melting iron ore in a blast furnace to produce crude ingots called pigs. This crude material is extremely brittle, so it is remelted and other elements are added in small quantities. Impurities are also removed, and the melt is then poured into casts and allowed to solidify.
Cast iron is an alloy, and its properties are changed by adding small amounts of different alloying elements…
Carbon is the main alloying agent, and this increases strength. The carbon content is usually between 1.8% – 4.0%
Silicon is the other main alloying element of cast iron and its content ranges between 1.0% – 3.0%. Silicon increases graphitization and controls the level of carbon present.
Nickel and copper increase strength and durability.
Titanium is added as a degasser and deoxidiser but it increases fluidity.
Vanadium will increase hardness and resistance to heat and wear.
Zirconium will deoxidise and increase fluidity.
Why Is Cast Iron So Popular?
The worldwide popularity of cast iron can be attributed to its valuable, natural properties:
- Durability
- Wear Resistance
- Compressive Strength
- Damping
- Fluidity and Castability
These properties have been exploited for centuries, particularly within the following applications:
Cooking: Cast iron is naturally non-stick, so you won’t need to use substances like Teflon, which have been found to be detrimental to health. Also, cookware made from cast iron will withstand extremely high temperatures and retain heat effectively. And the durability of cast iron makes it a sensible choice in terms of cost and replacement value.
Drainage – years ago, cast iron was a popular material for use in drainage and sanitation products. It is incredibly durable and highly impermeable to water and smells. Cast iron also has immense damping properties, meaning that it will absorb vibration and shock and withstand huge amounts of compression. However, more recently, the use of cast iron for pipes and drainage has declined and been replaced by PVC or ABS as they are lighter and have a reduced impact on the environment. Cast iron is still used in many high-rise buildings due to its durability and compressive strength.
Machinery – cast iron is exceptionally durable and has immense compressive strength. It can withstand high temperatures, and it has good fluidity, making it an excellent choice for casting machine components. Also – unlike cast steel – cast iron does not shrink.
Transportation – the properties of cast iron such as castability, wear resistance, damping qualities, compressive strength and relatively low cost have made it an ideal choice in the transport industry. Common applications include engine blocks, cylinder heads, industrial and marine pumps and generators, to name a few, and all can be maintained and restored effectively.
Structural – engineers have long favoured cast iron as a structural material, as it has a high strength-to-weight ratio. Its weight-bearing capability made it the first structural metal to be used, and it was applied in the first skyscrapers to be constructed. If used correctly, will provide excellent structural integrity for long-lasting structures.
Decorative Architecture – cast iron is a highly castable material, and it can be used to create very intricate, decorative items. Its longevity, as well as castability, means that these decorative exterior items will stand the test of time if correctly maintained. Typical examples include statues, fountains, bridges and bandstands.
Cast iron has been used for centuries to produce components for warfare, agriculture, cooking and architecture. It has seen many developments and improvements over the years but today it maintains its status as a crucial material for use within the engineering industry. And while alternative materials such as titanium can outperform cast iron in some applications, the cost often puts them out of reach.
Marie Palmer
Director
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