When Was Steel Invented?

When was steel invented? Crude steel has been made since 200 B.C., but it was William Kelly who received a patent for a steel making process in 1855.   

An alloy is a mixture of minerals or metals. Steel is mostly iron with a small amount of carbon. In ancient times, molten iron ore was processed to remove most of the carbon. Then, other metals could be added to the steel to make it stronger or to increase corrosion resistance.  

Steel may also include chromium, manganese, vanadium, and tungsten. These elements can make the steel harder, more ductile (its shape can be changed without cracking), and have more tensile strength (how much pull it can withstand before it changes shape or breaks).  

When Was Steel Invented?

Cast iron was made very early in steel making history. Iron absorbs carbon at high temperatures. Cast iron contains between 3 and 4 ½% carbon. This much carbon makes it harder, but more brittle.  

However, in the late Middle Ages, the blast furnace was invented. It used a blast of air to increase combustion. The molten cast iron ran through troughs, which were connected to a series of smaller troughs. This resembled a pig nursing her piglets, and so, the cast iron made in this way was nicknamed “pig iron.”

William Kelly

“When was steel invented?” is a question with no answer. But, the person who invented a process to purify iron was American, William Kelly (1811-1888). Kelly was in the iron making business, and because of the high cost of fuel, began to experiment with an “air boiling process” in 1847.

Air was blown through molten iron to reduce its carbon content. Contrary to what everyone thought would happen, the air did not cool the iron, but combined with the carbon. This made the iron boil rapidly until the carbon was extracted, thus making the iron a higher quality or changing it to steel.

In summary, this was a process that converted pig iron to steel using air, so it was called the “pneumatic process of steelmaking.” 

Sir Henry Bessemer 

Henry Bessemer (1813-1898) used Kelly’s process to lessen the cost of making steel and to mass produce it. In 1856, he made a converter which had holes in the bottom where compressed air was blown into the molten pig iron. This took the carbon out of the iron very quickly, and heated the iron even more, so it remained in a molten state.

One flaw in the process was it did not remove phosphorus, which makes steel brittle. The way around this was to only use ores that were phosphorous-free, but they were expensive.  

In 1876, Welshman Sidney Gilchrist Thomas, discovered that certain materials that are bases (as opposed to acids), like limestone, would  pull the phosphorous from the pig iron. It would float to the top and could be skimmed off. Now, steel making was cheap and easy. Because of this great contribution, Bessemer was knighted in 1879.

Stainless Steel

In addition to answering the question, “When was steel invented?” the invention of stainless steel is worth a look. Harry Brearley, from England, was the inventor of stainless steel.

Because he was an expert in steel production, two steel companies financed a laboratory for him. He was asked to solve a problem of a small arms manufacturer, whose rifle barrels were corroding away too quickly. So he began looking for a corrosion resistant steel, and began experimenting with changing the amount of chromium in the steel.

At that time, higher chromium steel was used in the aircraft industry because it was lighter than other steel. Stainless steel was invented on August 13th, 1913 and contained iron with 0.24% carbon and 12.8% chromium.  

After more testing, he found this new steel to be highly resistant to acids. Table cutlery, at that time, was prone to rusting and needed to be washed and dried thoroughly each time it was used. He saw how this would be very valuable to the cutlery industry. He had R. F. Mosley make some knives with, what he called, “rustless” steel. Mosley called it “stainless” when he experimented on them and failed to stain them. Since then, hundreds of applications for stainless steel have been found.