The Industrial Revolution was characterized by enormous growth in many areas of industry: mining, transport, and construction to name but a few. This growth set up a demand for more raw materials, and in many cases, for new materials with better properties that did not yet exist.
As these new materials were developed, by design or by chance, new applications sprang up to make use of them, creating further demands and so on. One of the features of the Industrial Revolution is the plethora of new materials that became available, and the upsurge in manufacturing methods that made use of them.
Metals, fibres and even the early precursors of modern plastics were available in unprecedented variety and quantity. In the s iron was by no means a new material, it had, after all, been around since the Iron Age nearly years earlier.
However, production of iron was restricted to small-scale smelting of iron ores, and the amount that could be produced was limited. Iron was produced by smelting it with charcoal wood that has been heated in the absence of air to burn off the impurities in the wood and leave it enriched in carbon: this partial burning produces an excellent fuel which is much more effective than wood itself. Britain had depleted huge areas of forest for fuel since the s, and timber supplies for charcoal were not going to be a sustainable long-term solution.
Legislation was in place to ban the harvesting of trees for charcoal production. Charcoal is more than just a heat source for producing iron from its ores. The key step in smelting iron ore to make raw metal is providing a reducing agent as well as heat: a reducing agent is a chemical that reacts with the iron oxides in the ore to release the iron in metallic form. The simplicity of charcoal is that it acts as both the heat source and the reducing agent.
What was needed was a method by which iron could be smelted in serious tonnage quantities. This was going to need a better heat source than charcoal. Woods in Britain were becoming scarce with demands on them for both building timber and charcoal.
Coal looked like it might be such a fuel. There was a problem, though: coal tends to have a high concentration of sulphur, which along with other impurities makes iron brittle. So iron produced by smelting with coal was of very poor quality. The development of cast iron as an engineering material is very much the story of the Darby family, who developed large-scale methods of making this valuable material. Abraham Darby had the idea of using not coal, but coke to smelt the iron.
Coke is made by controlled heating of coal in the same way that charcoal is produced from wood. Coke was the key step in developing a furnace capable of making cast iron on a large scale. This development in led to the cast iron industry being founded on the banks of the Severn at Coalbrookdale. The Old Furnace, parts of which still exist today, was the forerunner of the modern blast furnace Figure 1. It was used to make the members of the first cast iron bridge, spanning the Severn at Coalbrookdale, which also still stands shown right.
In this furnace, coke, together with limestone and iron ore, was fed in at the top and heated by burning in air that was fed in lower down; the molten cast iron was extracted at the base.
The air was fed in by pipes leading in about halfway up the furnace, which "blasted" a draught of hot air to the charge. The mechanical properties of the coke were important because the mixture had to be porous enough so that reduction of the ore proceeded smoothly, and it had to resist the weight of material above it. The molten iron could then be tapped and run directly into moulds. This furnace was especially important for making the key parts of steam engines.
The limestone helps in the reduction process, and also mops up some of the impurities to form a "slag" that floats on top of the liquid iron, and can be removed separately. A key discovery was that the amount of carbon present in the iron controlled not only its melting point but also its properties.
But who invented steel? They likely used techniques similar to the Bessemer process, which was only developed and popularised in Europe in the 19th century. Early examples of high-quality steel in China can be traced back to the 2nd century BC, with mass production taking off in the 3rd century AD. Damascus blades were manufactured in the Near East from ingots of wootz steel that were imported from India and Sri Lanka. They were renowned for their capability to be honed to a very sharp edge and their resistance to shattering.
However, it was still quite expensive to make, and was produced in limited quantities for special applications like armour, tools and weaponry. Alongside steam, steel leads the way towards the Industrial Revolution. Japanese smiths washed themselves before making a sword. If they were not pure, then evil spirits could enter the blade. The metal forging began with wrought iron. A chunk of the material was heated with charcoal until it became soft enough to fold.
A swordsmith used clay, charcoal, or iron powder for the next step, brushing the material along the blade to shape the final design. Patterns emerged in the steel that were similar to wood grain with swirling knots and ripples. Along the Rhine Valley in present-day Germany, metalworkers developed a contraption that stood about 10 feet high, with two bellows placed at the bottom, to accommodate larger quantities of iron ore and charcoal.
The blast furnace got blazing hot, the iron absorbed more carbon than ever, and the mixture turned into cast iron that could be easily poured into a mold. It was the ironmaking process the Chinese had practiced for 1, years—but with a bigger pot. Workers dug trenches on the foundry floor that branched out from a long central channel, making space for the liquid iron to flow. The trenches resembled a litter of suckling piglets, and thus a nickname was born: pig iron.
Iron innovation came just in time for a Western world at war. The invention of cannons in the 13th century and firearms in the 14th century generated a hunger for metal. Pig iron could be poured right into cannon and gun barrel molds, and Europe started pumping out weapons like never before. But the iron boom created a problem. As European powers began to stretch their power across the globe, they used up tremendous amounts of timber, both to build ships and to make charcoal for smelting.
The British Empire turned to the untapped resources of the New World for a solution and began shipping metal smelted in the American colonies back across the Atlantic. But smelting iron in the colonies destroyed business for the ironworks in England. Abraham Darby spent much of his childhood working in malt mills, and in the early s, he remembered a technique from his days of grinding barley: roasting coal, a combustible rock. Others had tried smelting iron with coal, but Darby was the first to roast the coal before smelting.
Roasted coal maintained its heat far longer than charcoal and allowed smiths to create a thinner pig iron—perfect for pouring into gun molds. England had discovered the power of smelting with coal. Benjamin Huntsman was frustrated with iron.
The alloys available to the clockmaker from Sheffield varied too much for his work, particularly fabricating the delicate springs. An untrained eye doctor and surgeon in his spare time, Huntsman experimented with iron ore and tested different ways of smelting it.
Eventually he came up with a process quite similar to the ancient Indian method of using a clay crucible. The ingots that emerged from the smelter were more uniform, stronger, and less brittle—the best steel that Europe, and perhaps the world, had ever seen.
By the s, Sheffield became the national fulcrum of steel manufacturing. Seven decades later, the whole country knew the process, and the steelworks of England burned bright. The Crystal Palace was built with cast iron and glass for the event, and almost everything inside was made of iron and steel.
Locomotives and steam engines, water fountains and lampposts, anything and everything that could be cast from molten metal was on display. The world had never seen anything like it. Henry Bessemer was a British engineer and inventor known for a number of unrelated inventions, including a gold brass-based paint, a keyboard for typesetting machines, and a sugarcane crusher. When the Crimean War broke out in Eastern Europe in the s, he built a new elongated artillery shell. He offered it to the French military, but the traditional cast iron cannons of the time were too brittle to fire the shell.
Only steel could handle the controlled explosion. The crucible steelmaking process was much too expensive to produce items as large as cannons, so Bessemer set out to find a way to produce steel in larger quantities.
One day in , he decided to pour pig iron into a container rather than let it ooze into a trench. Once inside the container, Bessemer blasted air through perforations on the bottom.
According to Steel: From Mine to Mill , everything remained calm for about 10 minutes, and then suddenly sparks, flames, and molten pig iron came bursting from the container. When the chaos ended, the material left in the container was carbon-free, pure iron. The impact of this explosive smelting incident is hard to overstate. When Bessemer used the bellows directly on the molten pig iron, the carbon bonded with the oxygen from the air blasts, leaving behind pure iron that—through the addition of carbon-bearing materials such as spiegeleisen, an alloy of iron and manganese—could easily be turned into high-quality steel.
At the top, a small opening spewed flames 30 feet high when the air blasted into the furnace. Almost immediately, though, a problem arose in Britain's ironworks. It turned out that Bessemer had used an iron ore containing very little phosphorus, while most iron ore deposits are rich in phosphorus. The old methods of iron smelting reliably removed the phosphorus, but the Bessemer Converter did not, producing brittle steel. The issue vexed metallurgists for two decades, until a year-old British police clerk and amateur chemist, Sidney Gilchrist Thomas, found a solution to the phosphorus problem.
It worked like a charm. The old Huntsman crucible process, which produced a paltry 60 pounds of steel in two weeks, was obsolete. The Bessemer Converter was the new king of steel. On the other side of the Atlantic, massive iron ore deposits remained untapped in the American wilderness. In , the United States was producing only a fifth as much iron as Britain. But after the Civil War, industrialists began turning their attention to the Bessemer process, sparking a steel industry that would generate vastly more wealth than the California Gold Rush.
There were roads to build between cities, bridges to construct over rivers, and railroad tracks to lay into the heart of the Wild West. No one accomplished the American dream quite like Carnegie. The Scottish immigrant arrived in the country at age 12, settling in a poor neighborhood of Pittsburgh. Carnegie began his ascent as a teenage messenger boy in a telegraph office. One day, a high-ranking official at the Pennsylvania Railroad Company, impressed by the hardworking teen, hired Carnegie to be his personal secretary.
He owned stakes in a bridge-building company, a rail factory, a locomotive works, and an iron mill. When the Confederacy surrendered in , the year-old Carnegie turned his attention to building bridges. Thanks to his mill, he had the mass production of cast iron at his disposal. But Carnegie knew he could do better than cast iron. A durable bridge needed steel.
About a decade before Sidney Thomas refined the Bessemer Converter with a lime-based lining, Carnegie brought the Bessemer process to America and acquired phosphorus-free iron to produce steel. By this point, Carnegie was single-handedly producing about half as much steel as all of Britain. Additional steel companies started sprouting up around the country, creating new towns and cities, including an iron mining town in Connecticut named " Chalybes " after the ironmakers of antiquity.
America was suddenly steamrolling its way to the top of the steel industry. To keep manufacturing costs down, wages were low. In July , tensions boiled over between the Carnegie Steel Company and the union representing workers at the Homestead mill. The company chair, Henry Clay Frick, took a hard stance, threatening to cut wages.
The workers hanged an effigy of Frick, and he responded by surrounding the mill with three miles of barbed-wire fence, expecting hostilities. About 3, strikers took control of Homestead, forcing out local law enforcement. Frick hired agents from the Pinkerton Detective Agency to guard the mill, and on the morning of July 6, , a civil battle ensued. Men gathered at the riverbank, throwing rocks and firing guns at the Pinkerton agents trying to get ashore in boats.
The strikers used whatever they could find as weapons, rolling out an old cannon, igniting dynamite, and even pushing a burning train car into the boats. Order was restored when a National Guard battalion of 8, entered the town and placed Homestead under martial law.
Ten people were killed in the clash. Frick was later shot and stabbed in his office by an anarchist who heard of the strike, but survived.
He left the company shortly after, and in , Carnegie hired an engineer named Charles M.
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