Metal Processing Through Centuries
Over thousands of years, humanity has grown and evolved in many ways. One advancement of note is our evolved understanding and usage of metal processing from ancient civilizations to modern society. The jump from burning iron ore over an open hearth to recycling steel and using electric furnaces is a huge one.
If you are curious about how we got to where we are today with metal processing, do read on.
History of Metal Processing
Iron’s beginnings date back many centuries. The first recorded use of iron was in 1800 BC by a people known as the Chalybes. The Chalybes wanted to make unparalleled weapons. At the time, bronze was primarily used but it wasn’t ideal as it was softer than iron. So the Chalybes would put iron ore into a hearth, hammer it, and then fire it repetitively. This method of metal ore processing created wrought iron, a predecessor to modern steel.
In 500 BC, the Chinese had developed a different method. They smelted the iron in tall furnaces using wood and the resulting liquid was poured into molds. This is one of the first instances of cast iron, another predecessor to modern steel.
Indian ironworkers in 400 BC happened to invent a method for smelting that created the perfect combination of carbon and iron for steel. They used crucibles. Crucibles were small clay cups that iron ore and charcoal could be put into, then the crucible was fired in the furnace and once it cooled, pure steel ingot resulted. However, this method did not gain traction elsewhere and thus the secrets of steel remained unknown to most of the world.
A major advancement came centuries after in present-day Germany. The blast furnace. The blast furnace was similar to the method used by the Chinese except on a larger scale. This blast furnace was capable of producing mass amounts of iron.
This innovation was incredibly popular however it required copious amounts of timber for smelting the iron. Until a British cast iron pot maker by the name of Abraham Darby made a discovery.
Darby realized that by roasting coal and then using it to smelt the iron, the coal held its heat for far longer which allowed for thinner iron which could be used for more precise products like gun molds. However, this method wasn’t quite perfected yet.
Then around 1740, a British clockmaker named Benjamin Huntsman entered the scene. Huntsman began experimenting with iron production because he found that iron produced at present varied too much for the fabrication of clock springs. This experimentation led him to a discovery similar to that of the ancient Indian crucible. The two key differences being the use of roasted coals as a heat source and instead of combining fuel and ore in a crucible, he heated the mixture over the coals. The results shook the world. Huntsman had created steel as we recognize it today.
Beginning of Steel Era
Henry Bessemer, a renowned British inventor in the 1850s, recognized the biggest issue with steel production was expense. So he developed a new method for the production of steel called the Bessemer converter. The converter was egg-shaped, lined with clay on the inside, and covered with steel on the outside. The converter blasted molten iron compounds with hot oxygen in bursts of air. The carbon in the iron compound bonded with the oxygen to leave behind pure iron. All they had to do then was add carbon compounds to the iron and the result was perfect steel. The only issue was that steel was too brittle.
The Bessemer Converter
Then along came Sidney Gilchrist Thomas of Britain. Through experimentation, he realized that the steel needed the addition of phosphorus so it wouldn’t be so brittle. To solve this problem he replaced the clay lining in the Bessemer converter with limestone. This slight adjustment was the silver bullet that allowed the converter to churn out many magnitudes more steel than ever before.
Steel production first reached America in the early 1800s but didn’t grow in productivity/popularity until Andrew Carnegie began producing steel using the Bessemer converter. The steel industry quickly exploded in the US and soon, America became the leader in steel production worldwide.
Back in Europe, a German scientist named William Siemens developed a furnace that could recycle the hot air produced by the furnace in order to hold its peak temperature for longer. Siemens’ idea took two decades to gain traction. In the 1860’s French engineer Pierre-Emile Martin adopted Siemens’ furnace design and constructed it on a larger scale. He found that the longer peak temperature allowed ironworkers more time to add precise amounts of carbon to the iron to make steel. It also allowed for scrap steel to be melted down. The design became known as the Siemens-Martin process.
In the 20th century, a Swiss engineer named Robert Durrer further modified the Siemens-Martin process. He discovered that by blasting pure oxygen, rather than regular air into the furnace, carbon separated from the iron more effectively. Additionally, by blowing the air in the top of the furnace versus the bottom (like the Bessemer converter), cold scrap steel could be used in the production process. This concept was aptly named the basic oxygen process.
It is important to note that the United States never adopted the basic oxygen process, they continued with the Siemens-Martin process which would lead to the eventual downfall of the United States steel industry. By the 1950s the United States steel industry was on the decline, hurt even more by the invention of aluminum for home goods. By the 1970's the United States was no longer the top steel producer and as of 2016, the United States is the fourth largest steel producer.
Modern Steel Production
And that brings us to today. The concept of the mini-mill was introduced for the production of stainless steel. Mini mills utilize electric arc furnaces that operate using carbon electrodes to create an electric charge to melt down metal. Mini mills operate primarily on the recycling of scrap steel.
The basic oxygen process that is still used around the world is a huge emitter of greenhouse gas. The mass amount of burning coal releases copious amounts of carbon dioxide. This has become a growing problem in today’s climate. And even though electric arc furnaces are environmentally friendly, they rely entirely on scrap steel, of which only a finite amount exists.
This is the driving force behind the research being conducted by MIT. They are trying electricity-based technologies for smelting metals but they haven’t discovered a method for smelting at high enough temperatures to melt iron or steel.
History of Metal Rolling
Metal rolling is a process adjacent to metal processing. The key difference being metal processing centers around the formation of steel whereas metal rolling centers around the manipulation of steel. The metal rolling process is when metal is forced between two rolls and compressed, like rolling dough with a rolling pin.
Early Metal Rolling
The first mention of metal rolling that we know of was in 1480 when Leonardo DaVinci made a sketch of a metal rolling machine that would roll lead for stained glass. There is no evidence that this machine was ever built though. In the 15th century, there were rolling mills that worked with soft metals like gold. By the beginning of the 17th century, rolling techniques were more widespread and there is evidence that lead and tin were rolled with cast iron rolls in two-high mills. These small mills were used because they didn’t have the energy capabilities to construct mills that were any bigger. However, by the end of the 17th century, larger rolled metal products could be made by heavier mills powered by horses or water wheels.
Middle Metal Rolling
Leonardo Da Vinci’s Design for a Rolling Mill
By the end of the 18th century, steam power was introduced and thus utilized in the rolling mills. These mills began to look similar to their modern counterparts. There were not notable changes to these mills until roughly 1900 with the advent of electric powered machines. The electric power was transferred from generators to motors that powered the turning rolls in the mills. Around this time, there was a growing demand for steel rolling over iron rolling as well as a desire for a refined sheet metal pressing process for things like ships.
Modern Metal Rolling Technology
The same basic design is used today in rolling mills as was used years ago. The primary differences are the materials used for the rolls and the design of the roll stack. This means more durable rolls and roll stacks that are capable of more control and force in the rolling process.
Today’s mills are capable of working with different types of metals and can create numerous end products, whether it is a sheet, a coil, or a slab of metal through evolved sheet metal processing methods. As such, rolling mills are designed with exacting standards pertinent to dimensional accuracy, surface, and material properties.
We hope that you gained some insight into the vast history of steel production and metal rolling. At Texas Iron and Metal we have a huge supply of surplus steel and metal inventory to meet your needs. If you are interested in finding out more or would like to request a quote, one of our knowledgeable salespeople would be happy to assist you.