Stainless steel may have first been created in ancient Persia during the 11th century — 1,000 years before it was first made in Sheffield, the Steel City.
Sheffield has a proud history as a northern powerhouse and it is all based on a formidable metal industry, bolstered by its invention of stainless steel in 1913.
Stainless steel is defined as an alloy of iron and chromium and by modern standards, must contain at least 10.5 per cent chromium.
But a new study found evidence in modern-day Iran of steel deliberately forged with chromium, at approximately one per cent.
This picture shows slag adhering to the side of a piece of a crucible. It was found at the site of Chahak, in Fars province, southern Iran. Analysis of this revealed it contained chromium, the first known use of it to make a steel alloy
Although the medieval methods left the metal unable to reach the high standards of today, the addition of chromium would have been substantial,researchers believe.
Just like modern-day stainless steel, where the chromium provides an anti-corrosive layer, the Persian steel would have obtained a protective coat.
Researchers from UCL tracked down the archaeological site where the chromium steel was made with the help of historical manuscripts.
They speak of a once famous steel production centre called Chahak.
Stainless steel and Sheffield
Sheffield was famous for its cutlery long before it became Steel City.
By the early modern period Hallamshire cutlers were importing steel from the Continent.
The earliest reference to steel making in South Yorkshire is from 1642.
The Sheffield steelmaking district had little or no reputation outside the area before Benjamin Huntsman invented crucible steel in 1742.
The early steelmakers simply supplied the cutlers, but by the mid nineteenth century nearly half the European output of steel was made in the Sheffield district.
The population of Sheffield grew from 14,531 in 1736 to 135,310 in 1851.
Yet the scale of the steel industry in the classic period of the Industrial Revolution was still small compared with that of Victorian times, and it depended on the handicraft skills of its workers.
A new era began in 1837 with the giant steel works of the East End, which soon used Bessemer converters to manufacture railway rolling stock and then armaments.
The cutlers were no longer the major customers of the steelmen.
At the end of the nineteenth century Sheffield remained the leading world centre for special steels, and its population had risen to over 400,000.
Source: David Hey
However, the physical location of the site remained a mystery, hindered by the fact many current villages in Iran are called Chahak.
But researchers tracked down the most likely location as Chahak, in Fars province, a village only known for agriculture, not archaeology.
Here they found a number of charcoal pieces retrieved from within a crucible slag and a smithing slag.
Using scanning microscope analysis, the researchers were able to prove the existence of chromite ore.
One ancient manuscript, called ‘al-Jamahir fi Marifah al-Jawahir’ (‘A Compendium to Know the Gems’), written by the Persian polymath Abu-Rayhan Biruni around the 11th century, describes this as a key ingredient.
Next, the researchers set out to find if the chromite ore, which is abundant in the area, was due to contamination or design.
In steel particles left over from the forging of the metal, the researchers discovered it was made up of between one and two per cent chromium.
This, they say. is evidence that it was added to the process on purpose to create the chromium alloy, which would make for a superior weapon or tool.
Dr Rahil Alipour, lead author on the study, said: ‘Our research provides the first evidence of the deliberate addition of a chromium mineral within steel production. We believe this was a Persian phenomenon.’
Historical records say the steel made from Chakak had a stunning pattern, but was notoriously brittle.
Researchers also hope their method and findings will allow for previously discovered Persian weapons to be tested to see if they were made at Chakak.
The presence of chromium in the steel could also explain why many Persian blades are in such good condition when found by archaeologists.
Stainless steel may have first been created in ancient Persia in the 11th century — 1,000 years before it was independently forged in Sheffield, the steel city. Pictured, a steel works in Sheffield in 1913, the same year Harry Brearley, a metallurgist, created a steel alloy with 12.8 per cent chromium – this was previously believed to be the first known batch of stainless steel
The earliest reference to steel making in South Yorkshire is from 1642. The city’s steel reputation grew in 1742 when Benjamin Huntsman invented crucible steel. By the mid nineteenth century nearly half the European output of steel was made in the Sheffield district
It is unknown why the chromium steel fell out of use in the region after several centuries.
And after it vanished from existence, chromium was not used again to make steel until the 20th century.
On the 13th August 1913, Harry Brearley, a metallurgist, created a steel alloy with 12.8 per cent chromium and 0.24 per cent carbon.
Until the latest Persian finding, it was believed this was the first ever batch of what became known as ‘stainless steel’.
He was focused on making metals that were resistant to rusting at high temperatures.
His invention is one of the most widely used of the 20th century, and is still utilised to this day.
The full findings are published in the Journal of Archaeological Science.