In terms of metals, iron is an enigma. It rusts easily, yet it is one of the most widely-used metals, and up to 90 per cent of all metal refined today is iron. Here we look at the specific properties of the iron element, its uses, its history, and how wrought iron is obtained from iron.
The word “iron” derives from an Anglo-Saxon word, “iren”, which is thought to have derived from earlier words meaning “holy metal” because it was used to make the swords used in the Crusades. It is a chemical element with the symbol “Fe”, which is derived from the Latin “ferrum”, which means “firmness”.
The iron element atomic number is 26. An atomic number is the number of protons in the nucleus of an atom, and the number of protons defines the identity of an element. Iron belongs to the first transition series and group 8 of the periodic table.
Iron metal is, by mass, the most common element on Earth ahead of oxygen. However, its metallic state is rare in the Earth’s crust, limited mainly to deposits by meteorites. Conversely, iron ores are among the most abundant in the Earth’s crust. Iron ores are minerals and rocks from which metallic iron can be extracted. Iron is a solid at 20ºC and has a melting point of 1538ºC and a boiling point of 2861ºC. In terms of melting point, that is around 500 °C higher than that required to smelt copper!
In terms of appearance, iron is smooth and pristine and pure iron ore surfaces are mirror-like silvery-grey. Iron reacts readily with water and oxygen to give brown to black hydrated iron oxides, commonly known as rust. Unlike the oxides of some other metals that form passivating layers, rust occupies more volume than the metal and thus flakes off, exposing fresh surfaces for corrosion.
History of iron
Iron objects have been found in Egypt, dating from around 3500 BC. They contain about 7.5 per cent nickel, which indicates that they were of meteoric origin. Before iron, humans used bronze for their weapons, tools and art, as it was the most robust material of their time.
In 1500 BCE, people in Mesopotamia started to recognise iron’s strength, lightness and workability compared to bronze. With advances in metallurgy, they could melt iron in their bloomeries (a type of metallurgical furnace used widely for smelting iron from its oxides). They discovered the material to be supple, easily manipulated, and it hardened to an incredible strength when it was cooled. The technology spread to southeast Europe through Italy and Greece and eventually to the British Isles and Central Asia.
This era is considered to be the transition from the Bronze Age to the Iron Age. Although, the history of the Iron Age didn’t start at the same time for all civilisations across the globe. Because of the distance between them and the fluid discovery of iron metallurgy, every subcontinent essentially had its own Iron Age with its own start date.
What is certain is that iron literally changed the destiny of Asia, Europe and other subcontinents where it was independently discovered and adopted, and it was a key factor in paving the way for our modern world.
Uses of iron
Iron was initially only used for small knives, personal ornaments, and as a way to repair bronze items. But its suitability for weapons and farming equipment quickly became apparent. This was a revolutionary move that made people more formidable warriors but also more efficient farmers. Tribes could suddenly travel much further, migrating to different parts of Asia or Europe and protecting themselves from attack along the way. This gave them access to places with greater potential, and when they did decide to settle down, they could use their newly-made sickles and ploughs to produce more food.
Iron has remained crucial throughout history and powered the Industrial Revolution. In the modern world, iron alloys like steel, stainless steel and cast iron are the most common industrial metals because of their lower cost and mechanical properties.
Alloy steels are carbon steels with other additives such as nickel, vanadium, chromium, manganese and tungsten. These are stronger and tougher than carbon steels and have a huge variety of applications, including bridges, cutting tools, electricity pylons, rifle barrels and bicycle chains. Stainless steel is very resistant to corrosion, and other metals such as nickel, copper, titanium and molybdenum are added to enhance its strength and workability. It is used in bearings, architecture, jewellery, cutlery and surgical instruments. Cast iron is as tough as steel but cheaper and is used for things like valves, pipes and pumps.
So we’ve covered iron, but what is wrought iron?
Traditional wrought iron consists of around 99.4 percent iron by mass and is an iron alloy with a very low carbon content (typically less than 0.08 per cent) compared to cast iron, which has between 2.1 per cent to 4 per cent. Before the development of effective methods of steelmaking and the availability of large quantities of steel, wrought iron was the most common form of malleable iron. The term “wrought” means “worked” because wrought iron is rolled, hammered or otherwise worked while it was hot enough to expel molten slag.
Wrought iron has been used in China for thousands of years but wasn’t popular in Western Europe until the 15th century. It reached its peak in the 1860s, and was used to create railways, warships, and the magnificent gates and doors seen in many European cathedrals, churches, and other significant buildings. It was also used for more commonplace building items like nails, chains, rivets, wire, bolts, nuts, and everyday items such as wagon tires and horseshoes.
However, although the use of wrought iron declined with enhanced ferrous metallurgy and steel became less costly to make, wrought iron was still popular due to its tough, malleable and corrosion-resistant qualities.
Once hot, the iron element material of wrought iron can be shaped into the chosen product. Wrought iron has a range of desirable features. It is incredibly durable, easy to maintain, and aesthetically beautiful. In fact, the ability of wrought iron to be customised is also one of its most alluring features. From gates and fences to balustrades and entranceways, wrought iron adds a touch of style and uniqueness to any property. Adding decorative spirals, curves, insets, scrolls and intricate patterns to the base design produces a result that is virtually impossible to replicate with other fencing materials.