Take a wander through the history of iron in Sweden - from prehistoric iron production to today's high-tech steel making processes.
Iron has been produced in Sweden for at least 2,500 years and down through the ages has had great significance for the country’s economy. Access to a supply of iron has been decisive for the development of technology in many cases – from agriculture to defence. Today, we are surrounded by iron and steel – it is so common that we barely think about it. But in bygone times, iron was both an expensive material and in high demand.
Metals – a Godsend
This gallery deals primarily with iron and steel production but in the first room there is also a presentation of other metals that have had great significance from an historical point of view. For the alchemists, the known metals – copper, gold, silver, iron, lead, mercury and tin – were of divine origin and linked to the seven heavenly bodies and the days of the week. The number seven was magical and full of secret knowledge.
The first Furnaces
The history of the iron industry began in Sweden around 500 BCE. For many centuries, iron was smelted from limonite or bog-iron ore and ferruginous earth in simple blister furnaces. The end product from such a furnace was an iron with a low carbon content, which could be forged and hammered out into, for example, shovel blades, scythe blades or knives. These blister furnaces were used in certain parts of Sweden until as late as the end of the 19th century. By that time they had been replaced by bigger and much more efficient blast furnaces.
Pig Iron and Bar Iron
As furnaces were built larger over time, they came to be called blast furnaces. The gallery displays models of various blast furnaces. The product from a blast furnace is called pig iron – iron with a high carbon content that is not malleable. Pig iron must therefore go through an additional process – refining – to become malleable. Various methods are used for refining pig iron The gallery shows a Walloon forge and a Lancashire forge. In the Lancashire forge from the mid 1800s, you can experience how the work was done at the hearth and see the gigantic dimensions of the tools used. The big hammer forge gets its power from a water wheel that you can just see in the background. The end product from the forge is called bar iron – a semi-manufactured product that can be worked into various kinds of products. Each ironworks had its own stamp hammered into the iron. The stamp allowed the authorities to monitor production throughout the country. It was important to the Swedish iron export industry that the quality was high. A bit further into the gallery, you’ll find a large collection of iron stamps from ironworks through Sweden.
A CHANGING WORLD
Quality Swedish steel and special alloy steel have been important exports for Sweden, particularly during the 20th century. Further back in history, steel, which has a higher carbon content than malleable iron, was an expensive product to make. A revolution in steel making resulted in the development of ingot steel processes during the latter part of the 19th century. In the mid 1800s, an Englishman by the name of Henry Bessemer invented a method for the mass production of steel and the process was named after him – the Bessemer process. The gallery displays a Bessemer converter. With the Bessemer process and other methods such as the Martin process and electric steel furnaces, steel production increased rapidly at the end of the 1800s. This new, cheap steel came to be used for railway rails, ships, bridges, prefab building units, and much, much more. The Eiffel Tower, which was erected for the World Expo in Paris in 1889, is a patent example of what the new technology could achieve.
The processing of iron and steel into other products is also described. It includes a universal rolling mill from the 1880s, for example.
Casting in Iron
Casting in iron is another area treated in this gallery. Cannon were already being cast at gun foundries in Sweden in the 16th century. At the foundries and mechanical workshops that were set up during the 19th century, stoves, agricultural implements, machine parts, garden furniture and many more products were made of cast iron. The gallery includes many examples of cast iron products.
Ferdinand Boberg’s drawings from Bergslagen in the 1920s reflect the decline of the iron and steel industry that occurred during that period. Many of the smaller forges and foundries, which had survived the competition from the big steel mills, were shut down at that time.
Manufacturing Steel today
The final part of the gallery shows how iron and steel are produced today. A century ago, the production from an average blast furnace in Sweden was around 10 tonnes of pig iron per day (24 hrs). At that time, there were around 150 blast furnaces in the country with a combined production of around 400,000 tonnes of pig iron per year. Today, the daily output of a modern blast furnace is around 2,000 tonnes. The four blast furnaces that remain in Sweden today produced (in 1996) around 3.5 million tonnes per year – seven times as much as a century ago.
In modern steel manufacture, the steel can be given a wide variety of characteristics in accordance with what it will be used for. Depending on whether the steel will be used in a bridge structure, for example, or a fire extinguisher or a surgical instrument, different characteristics will be required. The steel gets its characteristics from its chemical composition, but also from how it is processed and heat-treated. Very often, it is desirable to combine several different characteristics such as high strength with high ductility. Developing steel is an ongoing task for researchers.