The Bessemer Process
Adam Stone
UWID 1063731
ME 401
Professor Laura West
July 26, 2012
Sir Henry Bessemer lived from 1813 until 1898 and could be considered one of the outstanding
inventors of the nineteenth century with 117 patents in his name and many others not protected by
patents. Bessemer is referred to by many as the “father of steel” and yet 40 percent of the patents in his
name are totally unrelated to the iron and steel industries. Bessemer’s first patent involved the casting,
breaking off and counting of printing type and among other inventions to his credit were: developing a
die metal that could reproduce fine detail on cardboard and leather, creating a machine for grinding and
polishing telescope lenses as well as developing a machine for extracting the juice from sugar cane.
Clearly the man was intelligent and clever to say the least and was eager to attack new problems which
he encountered.
“The father of steel” is mainly known as the inventor of the Bessemer converter and the
Bessemer process both of which involve the production of steel from pig iron. It is interesting to learn
that Bessemer’s involvement in steel and steel production was a direct result of his recognition of the
low accuracy of bullets being fired from smooth bore guns. This was in 1854 when round shot was being
replaced by elongated shells or bullets and finding that the bullets were not hitting their targets.
Bessemer realized that the projectiles accuracy would be improved if the shell could be made to rotate
about its longitudinal axis. Bessemer designed a shell which contained a longitudinal channel which
terminated in a tangential vent. Through full scale tests he would eventually prove the validity of this
improved accuracy concept which also brought light to the fact that these newer and heavier projectiles
allowed heavier pressures to develop in the cast iron barrels of the guns being used, and it was soon
discovered that the cast iron barrels were made of a material which was too weak for this increased
loading. Keep in mind at this time steel which was used for cutlery and so-called edge tools did have the
strength needed however it was considered too costly for applications such as weaponry. The main
problem was that there was not a quick and inexpensive method of removing the carbon content in pig
iron. Up until this point steel manufacturing was somewhat of a reverse method by which carbon was
added to wrought iron in a process which took nearly a week of time and was also costly due to the
large amount of fuel needed for the process. Although at the time Bessemer had little knowledge of iron
metallurgy he was determined to produce a superior form of ferrous metal economically which would
provide the needed foundation for stronger gun barrels.
Bessemer soon began experimenting with methods to improve the quality of iron. Seemingly by
chance he witnessed two blocks of pig iron which appeared to be unmelted on the side of an open
hearth furnace. When he went to push the blocks he noticed that they were actually simply shells of
decarburized iron which were caused by the hot air converting the outsides of the iron blocks to steel.
As a result of this observation Bessemer began to realize that air alone could be used to reduce the
excess carbon in the molten pig iron as well as to raise the metal temperature resulting in a form of mild
steel without the cost of extra fuel being required. Prior to this observation by Bessemer the idea of
adding a stream of air to the molten iron was believed to have the effect of simply cooling down the
metal.
With this discovery Bessemer then began redesigning his furnace so that high pressure air would
be forced through the molten iron resulting in what would become known as the Bessemer process. This
forced air method (sometimes referred to as a pneumatic process) causes silicon and carbon impurities
in the iron to ignite which cause a “repeating cycle” in which the iron becomes hotter which burns off
more impurities, which becomes hotter, etc. The end result is a hotter, purer, molten iron which
converts to steel more easily by means of a method which was both faster and much less costly than the
current methods of the period. The Bessemer converter is essentially a furnace in which air is blown into
the bottom of the vessel and into the molten metal allowing the Bessemer process to take place as
previously outlined above.
So with the introduction of air to molten air the Bessemer process was born which was
seemingly discovered by a near accidental observation. The resulting forced air Bessemer process
method then prompted the bulk steelmaking era which fueled the rapidly expanding industrial
developments in areas such as railways, engineering and shipbuilding. This should be no real surprise as
once steel could be produced in a timely fashion at an affordable cost, the demand for steel would
immediately increase and new found applications would soon be discovered where once wrought iron
provided acceptable results, steel would prove superior.
Prior to the Bessemer process railways were expanding worldwide and were quite literally being
called “iron roads”. These iron roads however were laid exclusively with wrought iron rails. The wrought
iron rails provided acceptable results however they were prone to wear and repeated replacement.
Steel which has superior wear properties as compared to wrought iron was eventually tried on a few
tracks and once the railway company’s engineers noticed the outstanding wear properties the future of
the steel rails was all but guaranteed. Other significant steel consuming areas resulting from the
development of the Bessemer process were in steel ocean liners as well as skyscraper office, factory,
and residential buildings.
The basic Bessemer process has been altered and modified through the years and has stood the
test of time. Sometimes people refer to various second and third generation processes spawned by the
basic concept of Bessemer’s converter and some people have even tried to claim his process as their
own. These modifications and alterations of the process all would not have been possible without the
“father of steel” initially stumbling upon this great discovery of pumping air into molten metal and the
counter intuitive benefits of doing so. In looking around at all of the steel which is in use in today’s
modern world it would be hard to imagine what the world would be like today if it wasn’t for Sir Henry
Bessemer and his great contribution to the production of steel.
Resources:
Bodsworth, Colin. Sir Henry Bessemer: Father of the Steel Industry. London: IOM
Communications, 1998. Print.
Bessemer, Sir Henry (1905). An Autobiography. London: Engineering.
Langdon, William Chauncy. Everyday Things in American Life ... New York: C. Scribner's Sons,
1941. Print.